intra oceanic subduction related hydrothermal venting kermadec volcanic arc new zealand intra oceanic volcanic arcs mark the boundaries between converging lithospheric plates where subduction produces volcanic and tectonic activity that ensures a steady supply of magmatic heat and hydrothermal fluids to the seafloor here we report on the first broad and systematic survey of hydrothermal emissions generated along a submarine arc front more than half seven of 13 of the volcanoes surveyed along 260 km of the southern kermadec arc ne of new zealand are hydrothermally active our results indicate that volcanic arcs represent a previously unheeded but potentially extensive source of shallow 2 km water depth vent fields expelling fluids of a unique and heterogeneous composition into the oceans

stepwise expansions of c4 biomass and enhanced seasonal precipitation and regional aridity during the quaternary on the southern chinese loess plateau abstract the expansion of c 4 plants is one of the most prominent vegetation changes in the global ecosystem during the cenozoic era although c 4 plant expansions in the latest miocene have been widely reported factors driving the expansions are still in debate and the details of vegetation changes during the quaternary have not been well studied here we present high resolution carbon isotope time series of both organic matter and bulk carbonates covering the past 2 58 ma derived from the loess soil successions on the southern chinese loess plateau the organic matter 13 c values indicate stepwise c 4 plant expansions initiated at 1 6 and at 0 43 ma respectively we conclude that such tectonic time scale c 4 plant expansions are controlled by enhanced seasonality of precipitation relatively more precipitation in the warm growing season as well as regional aridity and this long term fluctuation superimposes on the orbital scale variations of c 4 plants while the latter appears phase locked with cyclical changes of summer monsoon circulations

submarine hydrothermal activity along the mid kermadec arc new zealand large scale effects on venting 1 the 2 500 km kermadec tonga arc is the longest submarine arc on the planet here we report on the second of a series of cruises designed to investigate large scale controls on active hydrothermal venting on this arc the 2002 nzaplume ii cruise surveyed 12 submarine volcanic centers along 580 km of the middle kermadec arc mka extending a 1999 cruise that surveyed 260 km of the southern kermadec arc ska average spacing between volcanic centers increases northward from 30 km on backarc crust along the ska to 45 km on backarc crust along the southern mka to 58 km where the mka joins the kermadec ridge volcanic cones dominate in the backarc and calderas dominate the kermadec ridge the incidence of venting is higher along the mka 83 10 of 12 volcanic centers than the ska 67 8 of 12 but the relative intensity of venting as given by plume thickness areal extent and concentration of dissolved gases and ionic species is generally weaker in the mka this pattern may reflect subduction of the 17 km thick oceanic hikurangi plateau beneath the ska subduction of this basaltic mass should greatly increase fluid loss from the downgoing slab initiating extensive melting in the upper mantle wedge and invigorating the hydrothermal systems of the ska conversely volcanic centers in the southern mka are starved of magma replenishment and so their hydrothermal systems are waning farther north where the mka centers merge with the kermadec ridge fewer but larger magma bodies accumulate in the thicker older crust ensuring more widely separated caldera dominated volcanic centers

spatiotemporal changes in c4 plant abundance in china since the last glacial maximum and their driving factors abstract knowledge of changes in the distribution of c3 and c4 plants in relation to climate change is the key to predicting the biosphere s response to future climatic warming there are significant differences in the spatiotemporal evolution of c4 plant abundance at different latitudes since the last glacial maximum lgm and the factors responsible remain debated in this study we reconstructed the spatiotemporal pattern of c4 plants in china since the lgm based on a synthesis of 13c records of soil organic matter from paleosol sequences and 13c records of individual n alkanes from lake and marine sediments the results indicate that spatially maximum c4 abundance during the lgm was in south china while maximum c4 abundance occurred in the chinese loess plateau in north china during the early and mid holocene temporally in north china c4 plant abundance initially increased since the lgm reached a maximum during the early and mid holocene and then decreased however the opposite trend occurred in south china combined with a physiological process model used to study the sensitivity of c3 and c4 plants to changes in climate and atmospheric pco2 in different regions our results reveal that temperature was the dominant factor driving c4 plant expansion in north china whereas atmospheric pco2 and precipitation were the main factors controlling c4 plant abundance in south china

changes in vegetation type on the chinese loess plateau since 75 ka related to east asian summer monsoon variation abstract floral communities in terrestrial habitats such as steppes are highly sensitive to regional climate changes here we generated carbon and nitrogen isotope profiles for soil organic matter som in the weinan loess paleosol section in order to investigate changes in floral communities on the chinese loess plateau clp and their relationship to climate variation since 75 ka 13csom at weinan ranges from 23 6 to 18 0 and 15nsom ranges from 3 4 to 5 5 modeling based on the 13csom record suggests that the proportion of c4 plants c4 has varied from lower during cold intervals with minima of 24 32 at 73 1 ka 20 9 ka lgm and 0 6 ka to higher during warm intervals with maxima of 62 64 at 53 0 ka and 8 2 ka the 13csom and 15nsom profiles are strongly correlated r 0 82 p

thermo erosional notch development at fresh water calving tasman glacier new zealand controls on glacier calving rates are receiving increased scientific interest at fresh water calving glaciers limnological factors might be more important than glaciological ones measurements of thermo erosional notch development at the calving ice cliff of tasman glacier new zealand suggest that the calving rates at this glacier are directly controlled by the rate of thermal undercutting notch formation rates typically vary between 10 and 30 cm d 1 maximum rate 65 cm d 1 in summer corresponding to an average calving rate of 34 m a 1 notch formation is slower than waterline melt and is controlled by water temperatures and circulation cliff geometry debris supply and water level fluctuations the latter shift the position of undercutting resetting the level of the notch formation process and thereby slowing it the geometry of the notch and the debris supply determine the extent of influence of the lake on notch water temperatures and circulation hence water temperatures in the lake are not necessarily indicative of the rate of notch formation the prediction of rate of notch formation from far field variables is hampered by the complex interaction of the influencing factors the significance of thermal undercutting as a calving rate controlling process decreases with increasing ice velocities calving rates and surface gradients

geographical distribution of 3he 4he ratios in japan implications for arc tectonics and incipient magmatism the 3he 4he and 4he 20ne ratios of 115 natural gas samples including various types of gases from volcanoes hot springs mineral springs water wells petroleum fields and natural gas fields were measured using a mass spectrometer the observed 3he 4he and 4he 20ne ratios range from 7 47 10 8 to 9 65 10 6 and from 0 26 to 1100 respectively the 3he 4he ratios reflect well the geotectonic structure of the japanese islands in northeastern ne japan there is a clear geographical difference in the 3he 4he ratios between the frontal arc forearc and volcanic arc back arc regions lower ratios were found in the trench side region and higher ratios in the back arc side this result suggests that the mantle derived helium in the volcanic arc region is associated with the diapiric uprise of a magma lower 3he 4he ratios in the frontal arc region may be due to radiogenic he produced by radioactive decay of u and th in the crustal and sedimentary rocks in southwestern sw japan there is no clear geographical contrast in the 3he 4he ratios some samples in the frontal arc region show quite high 3he 4he ratios the tendency of the 3he 4he ratios agrees with the distribution of terrestrial heat flow data and reflects geotectonic structures different from ne japan the high 3he 4he ratios observed in the frontal arc region in sw japan may be indicative of renewed or incipient magmatism due to a descending young and warm slab

a cosmogenic 3he chronology of late quaternary glacier fluctuations in north island new zealand 39 s abstract mountain glaciers advance and retreat primarily in response to changes in climate establishing the timing and magnitude of mountain glacier fluctuations from geological records can thus help to identify the drivers and mechanisms of past climate change in this study we use cosmogenic 3 he surface exposure dating and tephrochronology to constrain the timing of past glaciation on tongariro massif in central north island new zealand 39 s exposure ages from moraine boulders show that valley glaciation persisted between c 30 18 ka which coincides with the global last glacial maximum reinterpretation of moraine tephrostratigraphy using major element geochemistry analysis shows that ice retreat and climatic amelioration at the last glacial termination was well underway prior to 14 ka the equilibrium line altitude in central north island during the last glacial maximum was c 1400 1550 m above sea level which is c 930 1080 m lower than present considering the uncertainties in the glacial reconstruction and temperature lapse rates we estimate that this equilibrium line altitude lowering equates to a temperature depression of 5 6 1 1 c relative to present our mapping and surface exposure dating also show evidence for an earlier period of glaciation of similar magnitude to the last glacial maximum which culminated prior to 57 ka probably during marine isotope stage 4 good agreement between the timing and magnitude of glacier fluctuations in central north island and the southern alps indicate a response to a common climatic forcing during the last glacial cycle

lower temperature as the main cause of c4 plant declines during the glacial periods on the chinese loess plateau abstract the distribution of c3 and c4 plants changed in regionally contrasting ways during the last glacial period c4 plant expansion in low latitude africa and america coincided with c4 plant decreases in mesoamerica and the us great plains this c4 plant expansion has been attributed to lower pco2 and increased aridity and the decline in c4 plants is believed to have been caused by increased winter precipitation and lower temperatures however it is still difficult to generalize whether pco2 temperature or aridity was mainly responsible for c3 vs c4 vegetation changes during glacial periods paleoclimate conditions on the chinese loess plateau clp offer opportunities to further evaluate the role of temperature in the c3 vs c4 competition detailed climate records have shown that the clp region was drier and colder during glacial periods with aridity favoring c4 expansion and lower temperatures favoring c3 expansion here we present two high resolution compound specific carbon isotope records of n alkanes from the clp as vegetation biomarkers to estimate the relative abundance of c4 plants during the last two glacial interglacial transitions more negative 13c values during the glacial periods from two clp sites clearly show that in contrast with low latitude sites c4 plants declined this decrease in c4 abundance was caused by lower temperature despite the lower pco2 and increased aridity on the clp during glacial time

origin of carbon in fumarolic gas from island arcs abstract we have measured 3 he 4 he ratios 13c values and co 2 3 he ratios of fumaroles and hot spring gases in three volcanic areas in japan the 3 he 4 he ratios 13c values and co 2 3 he ratios vary from 02 05 ratm 9 7 to 2 7 and from 7 74 109 to 1 18 1011 respectively based on these data and those in the literature we present the first quantitative estimates of the upper mantle sediment and limestone including slab components in co2 of volcanic and hydrothermal fluids from subduction zones taking compiled c isotopic data of limestone and organic sediment assuming that the co 2 3 he ratio and 13c value of mid ocean ridge basalt morb are representative of the upper mantle component and that later isotopic and elemental fractionations are minimal it is possible to deconvole each fraction of c on the basis of simple mixing equations up to 20 of the carbon in high temperature volcanic gases in subduction zones is derived from a morb type source while the major fraction of the gases is attributable to co2 produced by decarbonation of subducted marine limestone and slab carbonate

cenozoic climate change in eastern asia part i abstract this special issue provides new studies in the field of cenozoic climate change in eastern asia the papers in this volume are multidisciplinary in nature and examine a range of topics including paleovegetation sedimentology clay mineralogy geochemistry magnetostratigraphy and climate modelling the findings of these studies demonstrate that analysis of terrestrial paleoclimate changes in eastern asia may offer insights into the effects of tibetan plateau uplift and ultimately the dynamic processes of global change that took hold throughout the cenozoic the second part of this special issue to be published later will add a paleoecology component examining how cenozoic climate change has impacted floras and faunas in eastern asia

did an extensive forest ever develop on the chinese loess plateau during the past 130 ka a test using soil carbon isotopic signatures abstract pleistocene vegetation history on the chinese loess plateau has been traditionally investigated using palynological methods and questions remain regarding whether an extensive broadleaf deciduous forest ever developed on the loess table under favorable climatic conditions the authors have employed a c isotope approach to address this question by comparing 13 c values in soil organic matter from different loess ecological domains with known source vegetation to the c isotope values obtained from a paleosol section that can be dated back to 130 ka the c isotopic compositions of modern soils from the loess table and the loess desert transition gave 13 c values of 24 5 to 18 2 and 25 7 to 20 7 respectively these c isotopic ratios are consistent with the standing modern vegetation that is dominated by a mixture of c 3 and c 4 plants and can be distinguished from that in the patchy forest areas where exclusive c 3 trees yield a narrow 13 c value range from 26 9 to 25 average 26 1 obtained 13 c compositions from paleosols and loess sediments in the lantian and the luochuan profiles vary from 24 to 16 9 indicating a grass dominated steppe with shifting c 3 and c 4 contributions controlled mainly by paleoclimatic changes during the late pleistocene the present results suggest no extensive forest coverage on the loess table during the past 130 ka even under the most suitable conditions for forest development this conclusion supports the explanation of natural causes for the development of only patchy forests on the modern loess table and provides critical historical information toward the vegetation restoration project that is currently underway on the chinese loess plateau

multiple origins and interpretations of the magnetic susceptibility signal in chinese wind blown sediments abstract in most chinese loess paleosol sequences high magnetic susceptibility values are found in the soil horizons with low values in the loess layers the susceptibility signal has been widely used as a proxy climatic indicator however both the causes and mechanisms which control susceptibility still remain controversial our recent studies challenge some earlier interpretations of the magnetic susceptibility signal in chinese wind blown sediments first the prevailing hypothesis of pedogenic origin cannot totally account for the susceptibility variations in many sections second in some cases the principal carrier of the magnetization seems not to be the ultrafine pedogenic minerals rather coarse lithogenic magnetic minerals derived from local sources can also contribute significantly to the susceptibility signal finally not all the chinese soils have higher susceptibility values than that of loess or sand layers opposite relationships do exist it is concluded that the source and causes of susceptibility may be different from site to site or even at different times at a given site any single hypothesis cannot completely account for the susceptibility variations in the chinese loess plateau and its surrounding regions besides the previous explanations of carbonate leaching pedogenic processes and organic decomposition the contribution of source materials to magnetic susceptibility must also be taken into account

calving of a tidewater glacier driven by melting at the waterline we present a study of the development of a thermo erosional notch at the waterline and its influence on calving of hansbreen a medium sized grounded tidewater glacier in southern svalbard the study is based on the results of undercut notch melt modelling based on measurements of sea water properties repeated terrestrial laser scans and analysis of time lapse camera images there is a strong correlation between observed calving activity and modelled melt rate of the undercut notch measured depths of the undercut reach 4 m and vary greatly over time the calving activity of hansbreen was significantly lower in 2011 than in 2012 due to the persistent presence of the ice pack in hornsund fjord which cooled the sea surface and suppressed the wave action calving on hansbreen is controlled by a local imbalance of forces at the front due to thermo erosional undercutting at the sea waterline calving activity is therefore sensitive to changes in sea water temperature and wave height it may be expected that calving rates will rise with increased advection of warm oceanic water to the arctic

link between climate and catchment erosion in the himalaya during the late quaternary abstract few studies using geochemistry of sediments from plains and delta of the himalayan river system have reported contrasting results on the shift in erosion of different lithotectonic units across the strike of himalayan orogen in response to changes in the intensity of indian summer monsoon ism and glacial cover during the late quaternary here we present records of the 143nd 144nd end and 87sr 86sr ratios and 13c of sediment organic matter 13csom in bulk sediment samples from two 45 m long alluvial cores collected from a paleo sutlej channel in sirhind punjab at an upstream connection of a large river ghaggar hakra with present day sutlej river in nw india the isotopic variations are compared with the available proxy records that document changes in the ism and himalayan glacial extent significant covariation in down core profiles of end 14 1 to 22 2 and 87sr 86sr 0 72251 0 79456 reveals changing contributions of sediment derived from the higher and lesser himalaya end member sources in the catchment higher end and lower 87sr 86sr during early marine isotope stage mis 1 and late mis3 reflects increased contribution from the higher himalaya as a result of receding glacial cover as well as intense ism that penetrates into the interior of the higher himalaya during warm periods the 13csom varies from 28 5 to 21 3 and shows a 5 7 increase from colder mis2 to warmer early mis1 implying an increase in c4 plant abundance during the same period in response to intensification of the ism in the post last glacial maximum period these variations in sediment provenance and vegetation pattern thus highlight the pronounced influence of climate on distribution of erosion and vegetation types in the nw himalaya

palynological evidence for late miocene pliocene vegetation evolution recorded in the red clay sequence of the central chinese loess plateau and implication for palaeoenvironmental change innorthernchina the late miocene pliocene redclay in the easternloess plateau fills a gapofclimate records between the wellknown loess soil sequences of the last 2 6 ma and the miocene loess soil sequences from the western loess plateau previous studies indicate that the red clay is also of wind blown origin covering the period from 7 8t o 2 6 ma the red clay therefore provides a good archive to reconstruct paleoecological succession and paleoclimate change in this study a palynological investigation was conducted on the late miocene pliocene red clay sequence at xifeng central loess plateau which provides new insights into the nature of the evolution of vegetation and climate change from 6 2 to 2 4 ma our results show that during this period the central loess plateau region was covered mainly by a steppe vegetation indicating long lasting dry climatic condition three vegetational zones were recognized during this period zone a 6 2 to 5 8 ma is characterized by a steppe ecosystem zone b 5 8 to 4 2 ma is characterized by a significant increase of temperate forest plants indicating a relatively humid regional climate zone c 4 2 to 2 4 ma indicates a typical steppe ecosystem the vegetation shift at about 4 5 3 7 ma when the temperate forest plants decrease the vegetation gradually changed to typical grassland and even to desert steppe this is interpreted to represent a drying event the uplift of the tibetan plateau at about 4 5 ma that resulted in the intensification of the monsoon reversal is thought to have playedanimportantroleinthissignificantecological change high latitude coolingmayhavepartiallycontributedtotheclimateshift during 4 5 to 3 7 ma in the loess plateau region and most likely was the driving force for the ecological shift at about 3 7 ma

late quaternary loess in northeastern colorado part i age and paleoclimatic significance loess in eastern colorado covers an estimated 14 000 km 2 and is the westernmost part of the north american midcontinent loess province stratigraphic studies indicate there were two periods of loess deposition in eastern colorado during late quaternary time the first period spanned ca 20 000 to 12 000 14 c yr b p ca 20 14 ka and correlates reasonably well with the culmination and retreat of pinedale glaciers in the colorado front range during the last glacial maximum the second period of loess deposition occurred between ca 11000 and 9000 14 c yr b p this interval may be holocene or may correlate with a hypothesized younger dryas glacial advance in the colorado front range sedimentologic mineralogic and geochemical data indicate that as many as three sources could have supplied loess in eastern colorado these sources include glaciogenic silt derived from the colorado front range and two bedrock sources volcaniclastic silt from the white river group and clays from the pierre shale the sediment sources imply a generally westerly paleowind during the last glacial maximum new carbon isotope data combined with published faunal data indicate that the loess was probably deposited on a cool steppe implying a last glacial maximum july temperature depression relative to the present of at least 5 6 c overall loess deposition in eastern colorado occurred mostly toward the end of the last glacial maximum under cooler and drier conditions with generally westerly winds from more than one source

plio pleistocene vegetation changes in the north china plain magnetostratigraphy oxygen and carbon isotopic composition of pedogenic carbonates abstract the plio pleistocene history of c4 plant biomass in northwestern china has been documented from the loess soil sequences of the loess plateau region however how c4 plants evolved in the warmer and low elevation eastern china monsoon zone is still poorly known mainly because of the unavailability of well dated geological records in this study a 203 6 m core of floodplain deposits was recovered from the north china plain near tianjin and dated magnetostratigraphically the results define a chronosequence for the last 3 3 ma the late quaternary portion of the core consists of fluvio marine sediments while the rest of the section 3 3 0 6 ma contains abundant paleosols formed on the floodplain as confirmed by soil micromorphological evidence the stable carbon and oxygen isotopic composition of pedogenic carbonates was measured to document vegetation and climate changes the results reveal mixed c3 and c4 vegetation with an estimated c4 abundance of 40 60 from 3 1 to 2 2 ma and a subsequent gradual decline to 25 until 0 6 ma this trend is consistent with the data from the loess soil sequences further west on the loess plateau suggesting they are regionally significant changes the lowering of growing season temperature and or drier conditions induced by global cooling would explain this overall decline

climatically driven glacial interglacial variations in c3 and c4 plant proportions on the chinese loess plateau high resolution 13c records of bulk organic matter om from three loess paleosol successions from the central chinese loess plateau document systematic fluctuations in c3 and c4 plant abundance for certain intervals during the past 620 k y measured 13c values of om in paleosols are less negative by 0 5 4 and total organic carbon toc contents are higher by up to 0 5 wt relative to corresponding values in loess deposits the 13com and toc decrease from peak values in paleosols progressively into overlying and underlying loess deposits integrated 13com toc and magnetic susceptibility rec ords indicate an increase in c4 vegetation to 50 during peak paleosol formation and a decrease in c4 vegetation to 30 during loess deposition for three of the past glacial interglacial cycles these results indicate that c4 plant abundance declined during glacials in this mid latitude region driven primarily by a shift to enhanced winter precipitation and lower temperatures and further contribute to the rapidly growing body of evidence that low p co2 during pleistocene glacials was insufficient to trigger c4 plant expansion without coincident favorable climatic conditions

test stable carbon isotopic composition of soil organic matters as a proxy indicator of past precipitation study of the sand fields in northern china abstract understanding the stable carbon isotopic composition 13 c of surface soil organic matter under various climates is crucial for quantitative reconstruction of past climatic changes although the relationship between precipitation and plant 13 c is well understood at global and regional scale studies relating 13 c of surface soil organic matter to precipitation in northern china remain controversial in this study 90 surface soil samples were collected from the desert loess transition zone of northern china where vegetation is sensitive to climatic changes the stable carbon isotopic composition of organic matter in these soil samples was analyzed in order to examine its palaeoclimatic implications our results show that the 13 c varied from 26 56 to 19 41 among the investigated sites with an average of 23 54 there was a strong negative correlation between the 13 c of surface soils and the mean annual precipitation map r 2 0 52 p 13 c of c 3 plants was the main factor that determined the 13 c of soil organic matter the c 4 c 3 biomass ratio may also contribute to the 13 c changes but this effect was relatively minor in our study area our findings suggest that a general transform function between the proxy index 13 c value and climates may not be applicable at one specific site and that a comprehensive investigation is needed when reconstructing the past climate change using the 13 c of buried soils

rates processes and morphology of freshwater calving at miage glacier italian alps the rates and processes of freshwater calving at miage glacier mont blanc massif italy are described calving at miage glacier has occurred for two centuries on its right lateral side into a small ice marginal lake miage lake field surveys identified the main processes leading to iceberg production and quantified the calving losses over a summer season calving losses were compared 1 with the surface ablation of the debris covered tongue evaluated through a simple model based on measured ablation rates at different altitudes and debris cover thicknesses and 2 with other inputs to the lake stream inflow discharge and with the lake volume results show that thermal undercutting by warmer surface water plays an important role in driving ice cliff evolution thermal notches grow at 30 35m year 1 and cause a similar amount of cliff retreat calving contributes 2 of the estimated summer runoff from the debris covered part of the ablation zone but this is equivalent to 38 of the lake volume and is of the same magnitude as the mean discharge from the inflow streams these data indicate that calving of the ice cliff is one of the main water sources for maintaining the lake at the maximum summer volume with the surface at the level of the subaerial outlet stream a survey of italian calving glaciers shows that calving is becoming more widespread and that debris covers are present at all calving ice margins the lake ice interactions described in this study can therefore be considered to have wider representativeness copyright 2006 john wiley sons ltd

helium 3 anomalies and crust mantle interaction in italy abstract the distribution of primordial 3he in the crust of italy has been investigated through a survey of groundwaters hot springs exploration and production geothermal wells the mantle derived component varies from 0 to 60 and reaches a maximum at vulcano in the eolian islands 3he anomalies occur where the conductive heat flow is relatively high but the relationships between heat flow and anomaly are uncertain the distribution of 3he in the main reservoir and cap rock to the larderello geothermal system shows that the mantle derived 3he varies from 5 to 40 of total he and reaches a maximum in fluids extracted from a depth of ca 3 km within the basement bomb produced tritiogenic 3he appears to make a near negligible contribution well 107 at larderello has been monitored over a period of 17 months and the 3 he 4 he ratio r varies from 1 4 to 1 6 times the atmospheric ratio ra whilst he ne varies from 9 to 160 a model is proposed for the larderello geothermal system whereby mantle derived heat and volatiles are advected to shallow 6 8 km depths in association with melts and released into the main geothermal reservoir at larderello in a non uniform manner possibly associated with fracturing isotopic and elemental equilibrium of gaseous species c o h appears to have taken place in the basement to the main reservoir from where fluid with r ra 3 2 has been extracted

helium isotopes in icelandic geothermal systems ii helium heat relationships abstract a model has been developed that relates the 3he content of the reservoir fluid to the fluid enthalpy in contrast to oceanic hydrothermal systems that display a uniform 3he enthalpy ratio 0 4 14 106 atoms of 3he joule icelandic systems vary by 1000 0 4 400 106 atoms joule a process that preferentially extracts helium relative to heat from a cooling magma produces high 3he enthalpy ratios for young systems e g krafla and low 3he enthalpy ratios for aging magmatic systems e g hveragaerdi using the highest 3he heat ratios measured in the fluid estimates of initial gas concentrations in the basalt are made for 3he 5 10 10 cc g and carbon 1200 ppm low temperature wells near geysir in southwest iceland appear to result from mixing of high temperature fluid 200 c and cold groundwater along a curve of constant 3he enthalpy

hydrothermal water rock interaction and the redistribution of li b and cl in the taupo volcanic zone new zealand abstract lithium b and cl occur as trace elements in the dominant protoliths rhyolite andesite and greywacke underlying high temperature hydrothermal systems in the taupo volcanic zone tvz the fluid mobility of li decreases substantially at 200 c 20 c with the pervasive deposition of quartz chlorite regardless of protolith and altering fluid compositions boron and cl are more fluid mobile than li at all temperatures with mobility affected by the rock type composition of circulating aqueous solutions and to a limited extent by incorporation of the trace elements in hydrothermal minerals uptake of b by clays decreases its mobility at 320 c occur compared to volcanic rocks the mobility of b and cl in greywackes is very low and thus the b cl signature of greywacke in hydrothermal aqueous solutions of the tvz is overwhelmed by the effects of rhyolite and andesite dissolution temperature dependent transitions from mg fe clays and phyllosilicates to k bearing illitic clays tend to decrease the mg li ratios in aqueous solutions at 200 c

reconstructing in situ vegetation dynamics using carbon isotopic composition of biopolymeric residues in the central chinese loess plateau abstract carbon isotopic compositions of total organic carbon toc or leaf waxes in soils have been used to reconstruct past changes in the relative abundance of c 3 and c 4 plants however toc contains organic matter of different source organisms plants animals fungi bacteria etc and its isotopic ratios could be modified during diagenesis since different organic fractions e g carbohydrates proteins lipids etc have different isotopic ratios and degradation rates leaf waxes on the other hand are transported by wind and hence represent vegetation input from a large geographic area we report in this paper a new approach to extract in situ paleovegetation information from late quaternary paleosols by determining carbon isotopic compositions of biomarkers derived from aliphatic bio and geopolymers of plant origin we show that c 9 to c 17 n alkenes derived from aliphatic bio and geopolymers are the dominant compounds released by flash pyrolysis of insoluble organic matter isolated from the late quaternary paleosols in the chinese loess plateau because the aliphatic polymeric substances are mainly derived from plant leaves bark and roots the isotopic signatures of these alkenes determined using pyrolysis gas chromatography isotopic ratio mass spectrometry reflect in situ vegetation changes our down core 13 c data from the xifeng loess paleosol profile show significant coherence among biopolymer derived n alkenes leaf wax n alkanes and toc for the past 40 kyr however the different amplitudes of the temporal isotopic changes among these data sets are indicative of variability in in situ and regional vegetation dynamics organic sources and effect of diagenesis our data also imply that below ground biomass is a major source of soil organic matter in the central china loess sediment

negative δ18o δ13c relationship of pedogenic carbonate from northern china indicates a strong response of c3 c4 biomass to the seasonality of asian monsoon precipitation abstract evaluating how future climate changes may impact c3 c4 biomass in east asia depends largely on the understanding of the relationship between past c3 c4 variations and asian monsoon circulation the glacial interglacial variations in c3 c4 biomass have been readily ascribed to the summer monsoon however the internal processes governing the link of c3 c4 vegetation to the asian monsoon have not been clearly described here we present isotopic results of pedogenic carbonate from northern china for the holocene the last and penultimate interglacial periods comparison of the observed and predicted 18o values of modern soil carbonate from gravelly soils suggests that pedogenic carbonate forms mainly in warm rainy season carbonate nodules from the chinese loess demonstrate a distinct negative 18o 13c relationship and a wider scatter of isotopic values in the southern loess plateau than in the northern part by combining rainfall 18o of precipitation and the peak of c3 and c4 plant metabolism we develop a conceptual model to explain the isotopic signatures of the carbonate nodules our model shows that a narrowly focused season of monsoon precipitation at a specific site produces low 18o values of soil water and simultaneously favors c4 over c3 plants our model further suggests that the scattered isotopic values of soil carbonate reflect a strong summer monsoon while the focused values indicate a weak summer monsoon 13c values of soil carbonate indicate a striking pattern of northward increasing c4 vegetation for the last interglacial while a flat spatial pattern is seen for the penultimate interglacial and the holocene it is inferred that the summer monsoon was stronger during the last interglacial than during the penultimate interglacial and the holocene leading to a northward displacement of c3 forest ecosystems into the southern loess plateau in addition an in phase relationship between intra nodule 13c and 18o values suggests a strong and possibly rapid response of c3 c4 biomass to the seasonality of asian monsoon precipitation in this context if the last interglacial period mis 5 is taken as an analog for the projected near future then c3 plants may be favored in the south while c4 plants may be efficient in the north

correlation of gold in siliceous sinters with 3he4he in hot spring waters of yellowstone national park opaline sinter samples collected at yellowstone national park ynp were analyzed for gold by neutron activation and for other trace elements by the inductively coupled plasma optical emission spectroscopy icp oes method no correlation was found between au and as sb or total fe in the sinters although the sample containing the highest au also contains the highest sb there also was no correlation of au in the sinter with the h2s concentration in the discharged hot spring water or with the estimated temperature of last equilibration of the water with the surrounding rock the au in rhyolitic tuffs and lavas at ynp found within the yellowstone caldera show the same range in au as do those outside the caldera while thermal waters from within this caldera all have been found to contain relatively low dissolved au and to deposit sinters that contain relatively little au therefore it is not likely that variations in au concentrations among these sinters simply reflect differences in leachable au in the rocks through which the hydrothermal fluids have passed rather variations in h2s the concentration of total dissolved sulfide that result from different physical and chemical processes that occur in different parts of the hydrothermal system appear to exert the main control on the abundance of au in these sinters hydrothermal fluids at ynp convect upward through a series of successively shallower and cooler reservoirs where water rock chemical and isotopic reactions occur in response to changing temperature and pressure in some parts of the system the fluids undergo decompressional boiling and in other parts they cool conductively without boiling mixing of ascending water from deep in the system with shallow groundwaters is common all three processes generally result in a decrease in h2s and destabilize dissolved gold bisulfide complexes in reservoir waters in the ynp system thus different reservoirs in rocks of similar composition and at similar temperatures may contain waters with different h2s and au the h2s in a subsurface reservoir water is difficult to assess on the basis of analyses of hot spring waters because of uncertainties about steam loss during fluid ascent however the same processes that result in low h2s in reservoir waters also tend to result in decreases in the ratio of 3he4he r dissolved in that water values of r relative to this ratio in air ra attain values 15 in ynp thermal waters to date all of the thermal waters at ynp that have rra values 9 have been found to deposit sinters with relatively low gold concentrations these include all of the thermal waters that discharge from 180 215 c reservoirs at upper midway and lower geyser basins within the western part of the yellowstone caldera and thermal waters at norris geyser basin outside the yellowstone caldera where some of the waters flow directly to the surface from a reservoir where the temperature is about 300 c a high 3he4he ratio in thermal water discharged at the surface does not guarantee high gold concentrations in the sinter deposited by this water boiling with loss of steam the gas phase takes a separate route to the surface during rapid upflow from the shallowest reservoir to the surface decreases the h2s and total he dissolved in the residual liquid without appreciably changing the 3he4he ratio this is because the isotopic composition of the he of the initial bulk fluid is unchanged and there is too little time for much radiogenic 4he to build back into the liquid during this rapid ascent from the near surface reservoir however if boiling with phase separation and loss of steam occurs deep in the system the 3he4he ratio in the residual liquid now depleted in h2s and total he will be susceptible to dilution with radiogenic 4he that is acquired during the longer residence time underground some or all of the au that comes out of solution when an initial gold bisulfide complex breaks down as a result of loss of h2s may be swept up to the surface as solid probably colloidal particles depending on the rate of flow of the mixture of water and steam and the geometry of the channel where colloidal silica also forms as a result of this boiling free au apparently becomes attached to the colloidal silica and deposits where the silica deposits

middle pleistocene dynamics of southern africa s winter rainfall zone from δ13c and δ18o values of hoedjiespunt faunal enamel abstract stable carbon and oxygen isotopes of fossil fauna have become important tools in linking palaeoecology and palaeoclimate in the case of grazing ungulates enamel 13c reflects c3 c4 grass abundance which in turn is primarily a reflection of minimum growing season temperature the south western cape is today a winter rainfall area where grasses are almost entirely c3 other parts of the country in contrast have summer rainfall and c4 grass flora in palaeoenvironmental studies the presence of c3 grasses serve as an important proxy for the presence of a winter rainfall regime and as a test of regional models of glacial interglacial climate change however evidence for the extent and intensity of the winter rainfall regime beyond the last glacial period is currently thin and a coherent picture of the long term evolution of this system has not yet emerged here we present a set of 13c and 18o values of fauna from paleontological layers at hoedjiespunt 1 hdp1 a fossilised brown hyaena parahyaena brunnea lair dating to between 200 and 350 ka on the west coast of south africa the assemblage is dominated by large grazing species which were resident during a glacial period when sea levels were lower and grasslands were widespread and productive grazers had predominantly c3 diets an indication of the dominance of c3 grass taxa comparison with other sites shows an extended picture of c3 grass dominance and hence winter rainfall regime on the west coast of south africa throughout the pleistocene however a positive shift in 13c values relative to those expected for pure c3 consumers is noted across all species in part this may reflect fluctuations in the global carbon isotopic content of the atmosphere but most likely indicates a small but significant intrusion of c4 grasses into the vegetation mosaic this phenomenon is most consistent with models which predict that c4 grasses should be favoured over c3 species at very low pco2 and reveals a hitherto unknown subtlety in our understanding of the evolution of this important biome

iceberg properties and distributions in three greenlandic fjords using satellite imagery icebergs calved from tidewater glaciers represent about one third to one half of the freshwater flux from the greenland ice sheet to the surrounding ocean using multiple satellite datasets we quantify the first fjord wide distributions of iceberg sizes and characteristics for three fjords with distinct hydrography and geometry sermilik fjord rink isbrae fjord and kangerlussuup sermia fjord we estimate average total iceberg volumes in summer in the three fjords to be 6 4 1 5 1 7 0 40 and 0 16 0 09 km 3 respectively iceberg properties are influenced by glacier calving style and grounding line depth with variations in size distribution represented by exponents of power law distributions that are 1 95 0 06 1 87 0 05 and 1 62 0 04 respectively the underwater surface area of icebergs exceeds the subsurface area of glacial termini by at least one order of magnitude in all three fjords underscoring the need to include iceberg melt in fjord freshwater budgets indeed in sermilik fjord we calculate summertime freshwater flux from iceberg melt of 620 m 3 s 1 140 m 3 s 1 similar in magnitude to subglacial discharge the method developed here can be extended across greenland to assess relationships between glacier calving iceberg discharge and freshwater production

sulfur cycling in the aftermath of a 635 ma snowball glaciation evidence for a syn glacial sulfidic deep ocean we have analyzed 34 s sulfate and pyrite 18 ocarbonate and 13 ccarbonate and major and trace elemental concentrations including extractable fe and mn phases in four sections of the maieberg formation the cap carbonate sequence to the marinoan glaciation in northern namibia 34 ssulfate profiles and other geochemical characteristics in the basal transgressive cap dolostone keilberg member are nearly identical in all sections and indicate deposition from a water mass with very low sulfate concentrations in the overlying interval that consists of rhythmites deposited during the transgressive high stand large geochemical disparities occur between sections that we interpret to have been deposited in open ocean versus restricted settings in the former a large negative shift in 34 ssulfate of 20 above the cap dolostone accompanies a change in mineralogy from dolomite to limestone a sharp decrease in 18 o and 13 c and a positive spike in fe and mn concentrations in the latter dolomite persists above the cap dolostone 34 ssulfate increases abruptly 18 o and 13 c are invariant and a spike in mn and fe concentrations is present but subtle these contrasting geochemical signatures in coeval sections can be explained by strong lateral chemical gradients that developed as cold euxinic deep water and a cap of warm oxic brackish water flooded the continental shelf during the post glacial transgression the geochemical di e rences between open ocean and restricted sections diminishes upsection presumably recording the gradual mixing and homogenization of the waters along the otavi platform

petrology of matthew and hunter volcanoes south new hebrides island arc southwest pacific abstract matthew and hunter the two southernmost active volcanoes of the new hebrides island arc southwest pacific differ markedly from the other mainly tholeiitic quaternary volcanoes of this arc geodynamically related to the new hebrides subduction zone they also lie close to the southern limb of the active expanding ridge of the north fiji basin both volcanoes are made up of acid medium k calcalkaline orogenic andesites containing a variety of inclusions pyroxene and gabbroic cumulates as well as doleritic cognate inclusions this paper presents the first systematic petrographic and chemical study of these volcanics and their inclusions trace element geochemistry and rare earth element modelling suggest that the two volcanoes developed from successive batches of similar parental magmas originating from limited partial fusion of garnet peridotite in the mantle wedge various degrees of fractional crystallization of these batches led to the formation of three volcanic suites hunter little fractionated west matthew moderately fractionated and east matthew highly fractionated moreover on matthew island no correlation exists between the degree of fractionation and the eruptive chronology the youngest edifice west matthew being less evolved than the older one east matthew

radiocarbon and δ13c depth profiles of soil organic carbon in the u s great plains a possible spatial record of paleoenvironment and paleovegetation abstract soil profiles from undisturbed grassland sites around the great plains of the usa were sampled for analysis of soil organic carbon soc content radiocarbon age and stable carbon isotope composition 13 c with the exception of a few pronounced dating anomalies soc radiocarbon age generally increases steadily with depth back to 10 15 000 cal yr bp the deepest soil intervals in 9 of the 12 sites the radiocarbon ages were used to establish the chronology of changes in past plant distribution over time and space based on soc 13 c as an indicator of c 3 and c 4 plant abundance changes were referenced to an soc 13 c value of 20 which is the approximate mid point between c 3 and c 4 carbon isotope composition i e an equal mixture of c 3 and c 4 carbon prior to 10 000 cal yr bp the region was dominated by c 3 plants with the exception of the southernmost texas sites from 10 000 to 2000 cal yr bp c 4 plants expanded their range initially as a peninsula of c 4 predominant grasses extending northeastward and ultimately dominating all but the northernmost border of the region finally the c 3 predominant region re expanded after 1000 cal yr bp perhaps as a response to the little ice age cooling despite uncertainties associated with using radiocarbon dated soc depth profiles as a proxy the past c 3 and c 4 plant distribution inferred from soc 13 c conforms well to results from other paleoclimate proxies and differences may be helpful in targeting future research

high resolution δ13ctoc and magnetic susceptibility data from the late early pleistocene southern margins of the chinese loess plateau abstract on the chinese loess plateau stable carbon isotope values for total organic matter 13ctoc from more than 10 loess paleosol sequences since the last glacial interglacial show generally consistent variations with enriched values normally occurring in paleosol layers the only exceptions are records from the westernmost and northwestern chinese loess plateau however both asian summer monsoon intensity and temperature have been suggested as the principal factor affecting these consistently similar 13ctoc variations until now 13ctoc records covering the whole quaternary have been relatively rare with problems including low resolution and conflicts in both the c4 expansion history and with related climatic interpretations in this paper we report on high resolution late early pleistocene low frequency magnetic susceptibility lf and 13ctoc data from yushan section on the southern margins of the chinese loess plateau our 13ctoc data present an abstruse relation with the glacial interglacial cycles represented by loess paleosol sequences with 13c enriched excursions in some paleosol layers and 13c depleted excursions in others furthermore our 13ctoc data shows negative and positive correlations with lf data using a threshold lf value of 70 10 8 m3 kg if the lf data are taken as an indicator of pedogenetic intensity and therefore an indicator of asian summer monsoon intensity there are two possible relations between chinese loess 13ctoc and asian summer monsoon intensity i e the chinese loess 13ctoc cannot simply be adopted as the sole indicator of asian summer monsoon intensity at least during the late early pleistocene on the southern margins of the chinese loess plateau our results demonstrate that c4 plants became a significant proportion of local vegetation cover only when asian summer monsoon intensity exceeded a certain degree for example in the surface vegetation for the s15 and s16 paleosol layers of the yushan section the relation between climate and chinese loess 13ctoc requires further detailed study

the role of fluids in lower crustal earthquakes near continental rifts earthquakes in the lower continental crust of the earth are rare as the lower crust is thought to be too hot to allow brittle failure so it is surprising that they occasionally occur where continental crust is rifting apart a study of three dimensional crustal structure and seismicity in the taupo volcanic zone an active continental rift in new zealand has now provided insight into how these earthquakes arise the crustal earthquakes form a continuous band along the rift and often occur in swarms suggesting fluid movement in critically loaded fault zones seismic velocities within the band are consistent with the presence of fluids and the linking of upper and lower crust seismicity to crustal structure point to a common explanation for all of the seismicity probably the weakening of faults on the periphery of an otherwise dry crust by hot fluids a report on three dimensional tomographic imaging of seismic velocities and attenuation in the taupo volcanic zone an active continental rift where earthquakes are known to occur in the lower crust finds that crustal earthquakes form a continuous band along the rift and often occur in swarms suggesting fluid movement in critically loaded fault zones the occurrence of earthquakes in the lower crust near continental rifts has long been puzzling as the lower crust is generally thought to be too hot for brittle failure to occur1 2 such anomalous events have usually been explained in terms of the lower crust being cooler than normal3 4 but if the lower crust is indeed cold enough to produce earthquakes then the uppermost mantle beneath it should also be cold enough2 and yet uppermost mantle earthquakes are not observed5 numerous lower crustal earthquakes occur near the southwestern termination of the taupo volcanic zone tvz an active continental rift in new zealand6 here we present three dimensional tomographic imaging of seismic velocities and seismic attenuation in this region using data from a dense seismograph deployment7 we find that crustal earthquakes accurately relocated with our three dimensional seismic velocity model form a continuous band along the rift deepening from mostly less than 10 km in the central tvz to depths of 30 40 km in the lower crust 30 km southwest of the termination of the volcanic zone these earthquakes often occur in swarms suggesting fluid movement in critically loaded fault zones8 seismic velocities within the band are also consistent with the presence of fluids and the deepening seismicity parallels the boundary between high seismic attenuation interpreted as partial melt within the central tvz and low seismic attenuation in the crust to the southwest this linking of upper and lower crustal seismicity and crustal structure allows us to propose a common explanation for all the seismicity involving the weakening of faults on the periphery of an otherwise dry mafic crust by hot fluids including those exsolved from underlying melt such fluids may generally be an important driver of lower crustal seismicity near continental rifts

a carbon isotope record of the upper chinese loess sequence estimates of plant types during stadials and interstadials the upper three couplets of paleosol loess in the luochuan section of northern china were analyzed for carbon isotopes these units date back to about 205 ka and have been correlated with the marine oxygen isotope stages 1 6 calcite is present as nodules concretions and interstitial cement analyses were performed on bulk samples of slightly cemented soil and loess material an ashing study indicates the presence of organic matter in the samples and it is possible that analyzed gases included a contribution from this source the measured 13c values and the estimates of co2 content in the atmosphere over this time derived from studies of the vostok ice core and from the 13c values of planktic benthic foraminifera are used following the method of cerling 1984 1991 to calculate the proportions of c3 vs c4 plants which contributed co2 to the formation of calcite in the paleosols and the loess c3 plants were dominant at all times paleosols 70 80 loess 55 60 c3 and both loess and paleosols show a decrease toward the present these relationships suggest a progressive drying of the environments due either to climate change or to changes in the local drainage network

flux of debris transported by ice at three alaskan tidewater glaciers the stability of tidewater terminus is controlled by glacial dynamics calving processes and sedimentary processes at the grounding line an investigation of grounding line sediment dynamics and morainal bank sediment budgets in glacier bay alaska u s a has yielded data that enable us to determine the debris fluxes of grand pacific margerie and muir glaciers debris flux ranges from 10 5 to 10 6 m 3 a 1 one to two orders of magnitude lower than the glacifluvial sediment fluxes 10 6 10 7 m 3 a 1 combined these fluxes represent the highest yields known for glacierized basins large debris fluxes reflect the combined effecrs of rapid glacier flow driven by the maritime climate of southeast alaska and highly erodible bedrock englacial debris distribution is affected by valley width and relief both of which control the availability of sediment the number of tributaries controls the distribution and volume of debris in englacial and supraglacial moraines at the terminus iceberg rafting removes up to two orders of magnitude more sediment from the ice proximal environment than is deposited by melt out or is dumped during calving events rough estimates of the sediment flux by deforming beds suggests that soft bed deformation may deliver up to an order of magnitude more sediment to the terminus than is released from within the glacier ice

global biogeochemical cycle of boron 1 the global boron b cycle is primarily driven by a large flux 1 44 tg b yr through the atmosphere derived from seasalt aerosols other significant sources of atmospheric boron include emissions during the combustion of biomass 0 26 0 43 tg b yr and coal which adds 0 20 tg b yr as an anthropogenic contribution these known inputs to the atmosphere cannot account for the boron removed from the atmosphere during rainfall 3 0 tg b yr and estimated dry deposition 1 3 2 7 tg b yr in addition to atmospheric deposition rock weathering is a source of boron 0 19 tg b yr for terrestrial ecosystems and humans mine about 0 31 tg b yr from the earth s crust more than 4 8 tg b yr circulates in the biogeochemical cycle of land plants and about 0 53 0 63 tg b yr is carried from land to sea by rivers the biogeochemical cycle of boron in the sea includes 4 4 tg b yr circulating in the marine biosphere and an annual loss of 0 47 tg b yr to the oceanic crust via a variety of sedimentary processes that collectively remove only a small fraction of the total annual inputs to the oceans thus with our current understanding of the global biogeochemistry of b the atmospheric budget shows outputs inputs while the marine compartments show inputs outputs despite these uncertainties it is clear that the human perturbation of the global b cycle has more than doubled the mobilization of b from the crust and contributes significantly to the b transport in rivers

a 130 ka reconstruction of precipitation on the chinese loess plateau from organic carbon isotopes abstract we study the relationship between organic carbon isotopes 13ctoc in soil and mean annual precipitation map in the east asian monsoon area by combining the results of carbon isotope studies of plants c4 c3 ratios and precipitation in the modern ecosystem of the chinese loess plateau based on this relationship we estimate the amount of paleoprecipitation that has occurred in the southeastern part of the loess plateau since the last interglacial stage using the carbon isotopic compositions of the soil organic matter som the results show that the annual precipitation in that region was high during the interglacial stages with a maximum value of 850 mm and that it decreased during the last glacial stage to a minimum value of 350 mm we suggest that the use of organic carbon isotopic composition in paleosol sediments is a reliable method for reconstructing paleoprecipitation due to the clear relationships between soil 13ctoc c4 c3 abundance and precipitation in modern ecosystems

phytoliths as quantitative indicators for the reconstruction of past environmental conditions in china ii palaeoenvironmental reconstruction in the loess plateau abstract quantitative reconstruction of the climatic history of the chinese loess plateau is important for understanding present and past environment and climate changes in the northern hemisphere here we reconstructed mean annual temperature mat and mean annual precipitation map trends during the last 136 ka based on the analysis of phytoliths from the weinan loess section 34 24 n 109 30 e near the southern part of the loess plateau in northern china the reconstructions have been carried out using a chinese phytolith climate calibration model based on weighted averaging partial least squares regression a series of cold and dry events as indicated by the reconstructed mat and map are documented in the loess during the last glacial periods which can be temporally correlated with the north atlantic heinrich events our mat and map estimations show that the coldest and or driest period occurred at the upper part of l2 unit late mis 6 where mat dropped to ca 4 4 c and map to ca 100 mm two other prominent cold dry periods occurred at lower ll 5 ca 77 62 ka and l1 1 ca 23 10 5 ka where the mat and map decreased to about 6 1 6 5 c and 150 370 mm respectively ca 6 6 6 2 c and 400 200 mm lower than today however the highest mat average 14 6 c max 18 1 c and map average 757 mm max 1000 mm occurred at sl interval mis 5 during the interstadial of l1 4 l1 2 mis 3 and during the holocene warm wet period the mat was about 1 2 c and map 100 150 mm higher than today in the weinan region the well dated mat and map reconstructions from the chinese loess plateau presented in this paper are the first quantitatively reconstructed proxy record of climatic changes at the glacial interglacial timescale that is based on phytolith data this study also reveals a causal link between climatic instability in the atlantic ocean and climate variability in the chinese loess plateau

seasonal and geographic climate variabilities during the last glacial maximum in north america applying isotopic analysis and macrophysical climate models abstract climate models provide estimates of climatic change over periods of time in the ancient past macrophysical climate models mcm differ from the more widely used general circulation models gcm in that mcms provide temporally high resolution 100 years and site specific estimations of monthly values of climate variables such as temperature and precipitation in this paper seasonal changes in climate variables are modeled for six 14c dated fossil localities in north america five of these localities represent the time of maximum extent of ice during the most recent glacial episode the full glacial 25 15 ka including one at the peak of the last glacial maximum 17 15 ka the other locality represents the time as the ice began to recede the late glacial 15 11 ka seasonal variations in temperature and precipitation modeled by mcm are herein compared with interpretations of seasonal variation based upon oxygen isotopes from serially sampled hypsodont teeth mostly equus and bison collected from each of these localities additionally the mcm modeled seasonal variations are used to predict the expected abundances of different plant functional groups pfg during those times especially c3 and c4 functional groups using modern relationships these predictions are compared with carbon isotopic values from the same teeth the importance of atmospheric pco2 for the relative abundance of plants utilizing the c4 metabolic pathway is discussed given that glacial episodes are known to have been times of lower atmospheric pco2 interpretations of seasonal variability and the relative abundance of c3 versus c4 vegetation based upon isotopes from tooth enamel are in broad agreement with predictions using the mcm and the modern distribution of pfgs with climate variables the influence of pco2 on the distribution of c4 vegetation during glacial times appears to be negligible

regional climate driven c3 and c4 plant variation in the cheollipo area korea during the late pleistocene abstract marine isotope stage 3 mis3 spanning from 25 to 60 ka bp was a time of substantial environmental change that included changes in the global ice volume and atmospheric composition with resultant regional climate changes to understand past vegetation responses to such environmental changes in korea we estimated the abundance of c3 and c4 plants using the c n and carbon isotope ratios of sedimentary organic matter the mis3 sedimentary unit at the cheollipo site located in a western coastal area of korea is characterized by a dark to light gray colored sedimentary unit 3 05 to 5 05 m in elevation mis3 which is between an underlain oxidized yellowish sedimentary unit 5 05 m in elevation the estimated abundance of c4 plants varied between 60 and 10 during the mis3 the suborbital scale variation in the estimated percentage of c4 plants was similar to those reported in continental ice volume and the east asian monsoon intensity suggesting that c4 plants prevailed under colder and drier conditions intensified winter monsoon whereas c3 plants have favored a warmer and wetter climate intensified summer monsoon compared with high latitude regions e g chinese loess plateau and lake baikal where low summer temperature suppressed aridity and pco2 influences during the last glacial period vegetation change in cheollipo area may have more sensitively responded to aridity change which had been affected by the summer winter monsoon intensity the climate change in the western coastal area yellow sea side of korea during the late pleistocene may have been controlled by regional climate change coupled with continental ice volume change

does δ13ccarb of the chinese loess indicate past c3 c4 abundance a review of research on stable carbon isotopes of the chinese loess current research on stable carbon isotopes of the chinese loess is reviewed the stable carbon isotopic composition of soil organic matter som 13corg of paleosols formed during interglacials is more positive than that within loess accumulated during glacials spatially it becomes progressively more negative from the eastern chinese loess plateau clp to the western however stable carbon isotopic composition of pedogenic carbonates 13ccarb from the same sequence produces an opposing trend both temporally and spatially and variation differs from expectations under conditions of equilibrium this indicates that 13ccarb in the chinese loess cannot be used to reconstruct the relative proportion of c3 c4 plants in past ecological communities furthermore use of 13ccarb to reconstruct the expansion of c4 plants in older tertiary red clay deposits is considered unreliable we believe 13ccarb may act as an indirect indicator of vegetation density following on changes in moisture supply controlled by the intensity of the asian summer monsoon but conclude that full understanding of the paleoclimatic significance of 13ccarb in the chinese loess and underlying tertiary red clay requires better understanding of modern isotopic processes

subaerial and sublacustrine hydrothermal activity at lake rotomahana abstract lake rotomahana is a crater lake in the okataina volcanic centre new zealand that was significantly modified by the 1886 tarawera rift eruption the lake is host to numerous sublacustrine hydrothermal vents water column studies were conducted in 2011 and 2014 along with sampling of lake shore hot springs and crater lakes in waimangu valley to complement magnetic seismic bathymetric and heat flux surveys helium concentrations below 50 m depth are higher in 2014 compared to 2011 and represent some of the highest concentrations measured at 6 10 7 ccstp g with an end member 3he 4he value of 7 1 ra the high concentrations of helium when coupled with ph anomalies due to high dissolved co2 content suggest the dominant chemical input to the lake is derived from magmatic degassing of an underlying magma the lake shore hot spring waters show differences in source temperatures using a na k geothermometer with inferred reservoir temperatures ranging between 197 and 232 c water 18o and d values show isotopic enrichment due to evaporation of a steam heated pool with samples from nearby waimangu valley having the greatest enrichment results from this study confirm both pre 1886 eruption hydrothermal sites and newly created post eruption sites are both still active

magnetic susceptibility of loess in china abstract the low field susceptibility of the loess deposits in the chinese loess plateau is due to both paramagnetic and ferromagnetic minerals paramagnetism can be seen in the less to unweathered loess horizons where superparamagnetic contributions which arise from ultrafine magnetite particles are not as strongly developed as in the heavily weathered palaeosols frequency dependent susceptibility and minimum unblocking temperatures of low temperature thermoremanent magnetization generally indicate finer grain sizes in the palaeosols as compared to the loess beds this grain size difference and the fact that susceptibilities of the same stratigraphic palaeosol layer vary by an order of magnitude between the western and central regions of the plateau are considered as strong evidence that the ultrafine magnetite is not of detrital aeolian origin but was formedin situ the pedogenetic processes are clearly related to palaeoclimatic changes therefore the various susceptibility properties may serve for a detailed reconstruction of the continental palaeoclimatic conditions for the last 2 5 ma since the palaeomagnetically dated beginning of loess sedimentation in china

fluid geochemistry and geothermometry in the western sector of the sabatini volcanic district and the tolfa mountains central italy abstract a geochemical survey of 197 fluid discharges cold and thermal waters and bubbling pools and 15 gas emissions from the western sector of the sabatini volcanic district and the tolfa mountains latium central italy was carried out in 2007 2008 the chemical and isotopic compositions of the fluid discharges indicate the occurrence of two main sources 1 relatively shallow aquifers with ca na k hco 3 and ca mg hco 3 compositions when trapped in volcanic and sedimentary formations respectively and 2 a deep reservoir which is hosted in the mesozoic carbonate sequence rich in co 2 and having a ca so 4 hco 3 composition dissolution of a co 2 rich gas phase into the shallow aquifers produces high tds and high pco 2 cold waters while oxidation of deep derived h 2 s to so 4 2 generates low ph the 13 c co 2 values for gas emissions from 2 8 to 2 7 vs vpdb suggest that the origin of co 2 associated with the deep fluids is mainly related to thermo metamorphic reactions within the carbonate reservoir although significant mantle contribution may also occur however r r a values 0 37 0 62 indicate that he is mainly produced by a crustal source with a minor component from a crust contaminated mantle on the basis of the 13 c ch 4 and d ch 4 values from 25 7 to 19 5 vs vpdb and from 152 to 93 4 vs vsmow respectively ch 4 production is associated with thermogenic processes possibly related to abiogenic co 2 reduction within the carbonate reservoir the 34 s h 2 s values from 9 3 to 10 4 vs vcdt are consistent with the hypothesis of a sedimentary source of sulfur from thermogenic reduction of triassic sulfates geothermometric evaluations based on chemical equilibria co 2 ch 4 and separately h 2 s suggest that the reservoir equilibrium temperature is up to 300 c the d and 18 o data indicate that water recharging both the shallow and deep aquifers has a meteoric origin fluid geochemistry coupled with gravimetric data and tectonic lineaments supports the idea that significant contributions from a deep seated geothermal brine are present in the stigliano thermal fluid discharges exploration surveys investigated this area during 70 s 90 s for geothermal purposes nevertheless presently the area is still under exploited the presence of thermal waters and anomalous heat flow together with the demographic growth of the last years makes this site a suitable location for direct applications of the geothermal resource

variation and paleoclimatic significance of organic carbon isotopes of ili loess in arid central asia as an indicator for terrestrial paleovegetation the stable isotopic composition of total organic matter delta c 13 org in loess sediments has been widely used for paleoclimatic reconstruction in western europe the great plains of north america and the chinese loess plateau clp however little is known about the variation and paleoclimatic significance of the loess delta c 13 org in arid central asia aca we report delta c 13 org data from an axike axk loess paleosol profile from the eastern ili basin eastern central asia along the profile the delta c 13 org values were more negative in the paleosol layers observed in the field and were confirmed by environmental magnetic proxies and a higher concentration of total organic carbon toc consistent with results for western europe and the northwestern clp our results demonstrate that the loess delta c 13 org in this region documents mainly the response of delta c 13 of locally predominant c 3 plants to paleoclimatic variation especially paleoprecipitation our results also suggest that the loess delta c 13 org values in the area have the potential for quantitative paleoprecipitation reconstruction on the basis of detailed delta c 13 org results from modern plants and surface soils in the future c 2013 elsevier ltd all rights reserved

the geothermal system of wairakei new zealand physical processes and age estimates inferred from noble gases abstract atmospheric and non atmospheric noble gases were identified by their isotopic composition in 31 samples from geothermal features from the wairakei tauhara and mokai geothermal fields north island new zealand in the fumaroles atmospheric noble gases ang were found in concentrations that exceed the values in air saturated recharge water asw by a factor of up to 14 significant concentrations of non atmospheric na 4 he he na and 40 ar ar na were observed up to 4 3 10 4 and up to2 9 10 4 cm 3 stp g fluid respectively in contrast the hot spring waters revealed significant depletions in ang as low as 0 02 of the asw concentrations and low but recognizable concentrations of he na and ar na in geothermal wells a wide spectrum of ang concentrations was observed from 0 02 to 30 times the concentrations in asw 4 he na and 40 ar na varied accordingly these observations lead to the simplified boiling model meteoric water penetrated into the geothermal compartment where it was heated and enriched by 4 he na and 40 ar na of mantle and crustal origins boiling of ascending fluid due to pressure decrease results in formation of a noble gas enriched steam phase issuing as fumaroles and drowned fumaroles and a noble gas depleted residual liquid the latter may cause secondary boiling of shallow groundwater emerging in hot springs geothermal wells tap fluids at various degrees of steam separation the depth of recharge of meteoric water into the geothermal system exceeds the depth of boiling which is 600 m at the studied area the ang patterns along with he na ang ratios are applied to identify the following physical processes a mixing of early separated steam with residual liquid b mixing of a few per cent groundwater with residual liquid c addition of air d addition of excess ne and e encroachment of recent groundwater due to pressure decrease retention enrichment values of the ang were applied to reconstruct non atmospheric initial nai concentrations of he nai ar nai and the initial co 2 in the geothermal water literature data on 3 he 4 he were used to separate the 4 he nai concentrations into crustal and mantle derived components the crustal radiogenic 4 he concentration calculated for the initial water was applied to derive an age estimate of the geothermal water assuming storage in rhyolitic rocks effective ages of 2 10 4 1 10 5 and2 10 5 a were obtained for the initial liquids feeding the wairakei wells fumaroles and mokai wells respectively crustal ar na concentrations were estimated from those of crustal he and from the rhyolitic 4 he 40 ar production ratio the calculated crustal 40 ar is 0 1 of 40 ar na and 4 he 40 ar contribution is found at wairakei to be 0 5 within the range of values measured by other workers in mantle derived rocks

reply to comment on regional climate driven c3 and c4 plant variation in the cheollipo area korea during the late pleistocene by j lim w h nahm j k kim d y yang palaeogeography palaeoclimatology palaeoecology 298 2010 370 377 abstract ouyang et al 2013 in this issue raise two concerns regarding carbon isotope analysis and its use for reconstructing past vegetation changes recently published by lim et al 2010 one issue questions the formation of sedimentary organic matter by competitive contribution of c 3 and c 4 plants and calculation of the relative contributions of c 3 and c 4 plants with a binary mixing model using their mean 13 c values the second issue questions the use of the 13 c value of flora from other regions or of the current flora as a universal reference to determine the composition of plants in the remote past pointing out the importance of understanding the exact assemblage of local plants in the past by complete sporo pollen assemblage analysis and molecular biomarker analysis in response to these concerns we provide a detailed description of the tracing process for determining the source of sedimentary organic matter using 13 c values and c n ratios and assess the suitability of calculating the relative contributions of c 3 and c 4 plants using a binary mixing model finally based on its advantages compared to other biological proxies we explain the utility of using 13 c toc values for reconstructing past vegetation changes

evolution of the taupo hikurangi subduction system abstract the present day taupo hikurangi subduction system is a southward extension of the tonga kermadec arc system into a sediment rich continental margin environment it consists of a shallow structural trench the hikurangi trough a 150 km wide imbricate thrust controlled accretionary borderland the continental slope shelf and coastal hills of eastern north island a frontal ridge the main greywacke ranges of north island and a volcanic arc and marginal basin the taupo volcanic zone structural elements become progressively more elevated and subduction more oblique towards the south the whole nne trending system is truncated at a largely strike slip transform boundary that extends along the southwestern part of the hikurangi trough and the hope fault of south island to the main alpine fault the volcanic arc is 200 270 km from the structural trench and comprises a nne trending chain of andesite dacite volcanoes extending along the eastern side of the taupo volcanic zone most of the andesites are olivine bearing and have been erupted within the last 50 000 years it is suggested the taupo hikurangi margin has evolved by rotation of accretionary elements from an original nw trending subduction system north of new zealand the older elements of the prism were associated with subduction of a re entrant of the pacific plate and perhaps the south fiji basin in mid tertiary times they subsequently became separated from their nw trending volcanic arc by dextral strike slip movement along curved faults east of the main greywacke ranges during the plio pleistocene oblique subduction and accretion intensified as the taupo hikurangi margin rotated into line with the nne trending kermadec system and a marginal basin was developed along a similar trend to form the taupo volcanic zone within the last 50 000 years olivine bearing andesite volcanism has commenced along the eastern side of the taupo volcanic zone

vegetation variation of loess deposits in the southeastern inner mongolia ne china over the past 1 08 million years abstract the stable carbon isotopic composition of organic matter of aeolian silt deposits is regarded as an appropriate proxy index of paleovegetation especially in the chinese loess plateau in central china in this study a loess paleosol sequence in the southeastern inner mongolia autonomous region in northeastern ne china which is located outside the chinese loess plateau is chosen to reconstruct the vegetation history since 1 08 ma temperature exhibits a threshold value which determines the growth of c4 plants in this study area the organic matter of the samples is derived from two different vegetation types namely the mixed c3 and c4 plants and the pure c3 plants the 13c of the organic matter shows negative values in loess units and higher values in paleosol units this finding reflects the influence of temperature and summer monsoon intensity on the vegetation dynamics over glacial interglacial cycles on a longer time scale the 13c values are higher between 1 1 and 0 9 ma and after 0 35 ma and lower between 0 9 and 0 35 ma which may be attributed to a long term temperature variation our analysis shows that regional temperature is the most important limiting factor that forces vegetation changes at the glacial interglacial time scale in ne china

reinterpreting climate proxy records from late quaternary chinese loess a detailed osl investigation abstract numerous authors have utilised physical properties of chinese loess and red clay deposits to develop apparently detailed and continuous past climate records from the miocene into the holocene many of these studies have further suggested that the principal climatic agent responsible for the aeolian emplacement and diagenesis of chinese loess the east asian monsoon has fluctuated rapidly on millennial to sub millennial timescales in concert with dramatic changes in the north atlantic dansgaard oeschger cycles and heinrich events and the western pacific el nino southern oscillation much of this evidence is based on reconstructions and age models that are tied to assumptions concerning the nature of loess sedimentation and diagenesis for example the belief that loess sedimentation can be viewed as essentially continuous some authors have however cast doubt on these assumptions and suggest that the application of radiometric techniques may be required to determine their validity recent studies utilising optically stimulated luminescence osl methods have reinforced these doubts and here osl dates obtained at 10 cm intervals from three sites along a transect across the chinese loess plateau have been used in combination with climate proxy evidence to test the existing assumptions that underpin many palaeoclimatic reconstructions from loess in this way the first time continuous and independently dated late quaternary climate reconstruction is developed from loess the data indicate that sedimentation is episodic and that once emplaced loess is prone to pedogenic disturbance diagenetic modification and in some cases erosion the relationships between proxies and sedimentation rates are also assessed and climatic interpretations based on different age models compared the implications of these findings for reconstructions of climate from loess are explored and comparisons are made between the developed palaeoclimate records and evidence from ice and ocean cores this exercise also highlights important information concerning the relative influence of forcing mechanisms behind east asian monsoon change over the late quaternary

onset of calving at supraglacial lakes on debris covered glaciers of the nepal himalaya field surveys of supraglacial ponds on debris covered glaciers in the nepal himalaya clarify that ice cliff calving occurs when the fetch exceeds 80 m thermal undercutting is important for calving processes in glacial lakes and subaqueous ice melt rates during the melt and freeze seasons are therefore estimated under simple geomorphologic conditions in particular we focus on the differences between valley wind driven water currents in various fetches during the melt season our results demonstrate that the subaqueous ice melt rate exceeds the ice cliff melt rate when the fetch is 20 m and water temperature is 2 48c calculations suggest the onset of calving due to thermal undercutting is controlled by water currents driven by winds at the surface of the lake which develop with expanding water surface

summer monsoon intensity controls c4 c3 plant abundance during the last 35 ka in the chinese loess plateau carbon isotope evidence from bulk organic matter and individual leaf waxes the natural abundance of c3 and c4 plants is affected by multiple environmental factors including temperature moisture balance and atmospheric pco2 the relative importance of these factors is a subject of considerable debate and may vary in different natural ecosystems previous studies generally focus on single loess sequences in the chinese loess plateau and conflicting conclusions on c4 c3 have been reached when studying carbon isotope ratios in carbonate and organic matter in this paper we report a comprehensive carbon isotopic characterization of total organic carbon toc and individual higher plant leaf waxes from five loess sequences spanning the last 35 ka from the chinese loess plateau clp the five coring sites encompass large gradients of annual mean temperature 9 2 13 9 c and precipitation 402 673 mm allowing us to assess the controlling mechanisms on c4 c3 plant ratios glacial interglacial sequences provide carbon isotope data for comparison with other climatic and environmental proxies such as lithology and magnetic susceptibility our results demonstrate that increased c4 c3 ratios are positively correlated with higher temperature and increased summer rainfall which characterize stronger summer monsoon in all five sites we conclude c4 abundance increases from the last glacial to the holocene in response to greater monsoon activity and that the c4 expression is suppressed in the cold and drier intervals

impact of additional dead carbon on the circulation estimation of thermal springs exposed from deep seated faults in the dongguan basin southern china abstract in hydrothermal systems the dissolved carbon of thermal groundwater may contain components derived from mineral alterations under high temperatures metamorphic source and or from magmatic gases additionally from carbonate dissolution most common these components are known as additional dead carbon which dilutes the modern carbon used for dating leading to the overestimation of 14c ages four typical geothermal springs hosted by deep seated faults and eighteen non thermal springs and wells from the dongguan basin of southern china were investigated to assess the circulation times of the hydrothermal system based on their radiocarbon contents for the thermal springs the circulation depth approximately 3648 m the apparent 14c ages 20 15 to 12 97 ka and the 13c calibrated 14c ages 16 02 to 8 55 ka were estimated the circulation speed of the thermal groundwater was as low as 0 46 m a which was too slow for a fracture hydrothermal system hosted by deep faults the analysis of the helium and carbon isotopes in the thermal groundwater revealed the existence of mantle derived carbon and thermally altered carbon from limestones a 13c 3he 4he illustration was proposed to correct for the additional dead carbon content according to the reassessed 14c ages the groundwater circulation time was overestimated and the circulation speed of the thermal groundwater was underestimated in hydrothermal system the reassessed 14c ages can provide a more reasonable result than the initial slow estimate in the context of a fracture hydrothermal system hosted by deep faults we conclude that measured 14c contents should be reassessed during the use of radiocarbon dating for thermal groundwater if additional dead carbon exists in the water

climatic implications of the s5 paleosol complex on the southernmost chinese loess plateau the s5 is the most prominent paleosol unit in the chinese loess plateau and is distinguished by its great thickness dark color and well developed clay coatings previous studies led to the proposal that the s5 developed under much warmer and wetter conditions than at present implying a climatic optimum however the s5 is a paleosol complex corresponding in time to a period of weak glacial interglacial oscillations as recorded by marine oxygen isotope stages 15 through 13 to understand the character of this climatic interval two profiles of the paleosol s5 in the guanzhong basin were studied with most of the emphasis being placed on the uppermost and best developed pedon s5 i grain size mineralogical and chemical data indicate that the major pedogenic processes experienced by the s5 i included complete decalcification and mechanical translocation of fine particles chemical alteration of silicate minerals has been weak stable carbon isotope analyses of organic matter showed that c4 plant remains are abundant throughout the profiles these results suggest that grasslands dominated the paleovegetation during s5 i development the prominent development of the s5 paleosol complex may reflect a prolonged period of pedogenesis in contrast to previous reports paleoclimatic conditions perhaps even drier than at present are implied by the data for the s5 profiles the relative strength of the glacial interglacial oscillation in this region related to the east asian monsoon was similar to that indicated for global climate during s5 time

glacier calving a numerical model of forces in the calving speed water depth relation empirical data suggest that the rate of calving of grounded glaciers terminating in water is directly proportional to the water depth important controls on calving may be the extent to which a calving face tends to become oversteepened by differential flow within the ice and the extent to which bending moments promote extrusion and bottom crevassing at the base of a calving face numerical modelling suggests that the tendency to become oversteepened increases roughly linearly with water depth in addition extending longitudinal deviatoric stresses at the base of a calving face increase with water depth these processes provide a possible physical explanation for the observed calving rate water depth relation

characteristics of tide water calving at glaciar san rafael chile glacial calving is a poorly understood process this study tests the influence of local environmental variables on the magnitude and frequency distributions of calving behaviour at glaciar san rafael chile near the terminus of the glacier surface speeds average 17 m d 1 in summer and calving is profuse and continual the size location and characteristics of over 7000 calving events were recorded during 32 d in 1991 and 1992 together with meteorological bathymetric and oceanographic data mean daily calving exceeds 400 events per day and the mean calving flux is more than 2 mm 3 d 1 mean annual calving speed and calving flux are about 4500 m a 1 and 2 0 km 3 a 1 respectively this calving speed is higher than that predicted by the established empirical relationship between tide water calving speed and water depth this is surprising given the low salinity of laguna san rafael and that fresh water calving speeds are commonly much lower than those in tide water daily patterns of calving frequency and flux correlate poorly or not at all with meteorological variables but tidal stage may have some control over the timing of large submarine calving events submarine calving produced the largest bergs however the relatively small total flux recorded from the submerged part of the ice cliff may imply unusually rapid melt rates

island arc tectonics of new zealand manifested in helium isotope ratios abstract thirty gas samples of various types volcanic gas geothermal gas ch4 rich natural gas and petroleum gas were collected in and around the north island new zealand 3 he 4 he and 4 he 20 ne ratios were measured using a mass spectrometer the observed 3 he 4 he and 4 he 20 ne ratios of the samples varied from 0 08 10 6to 8 75 10 6 and from 4 8 to 2100 respectively based on a 3 he 4 he 4 he 20 ne diagram he in the samples can be explained by mixing of a subduction type magmatic a radiogenic and an air component the geographical distribution of 3 he 4 he ratios over the island indicates a clear contrast between forearc and volcanic arc regions high in the former and low in the latter a he boundary can be drawn from the taupo volcanic zone to egmont volcano in terms of the 3 he 4 he profile this boundary agrees well with that of high q lowq in the upper mantle as well as with the geographical distribution of terrestrial heat flow values the high 3 he 4 he ratios in the volcanic arc region are attributed to subduction type he associated with an uprising magma from the upper mantle and the lower ratios in the forearc region to radiogenic he derived from u and th in basement and sedimentary rocks this tendency is very similar to that found in northeast japan and is understood to be a general signature of the he isotope ratio in an island arc system

helium isotopes in historical lavas from mount vesuvius comment on noble gas isotopic ratios from historical lavas and fumaroles at mount vesuvius by d tedesco et al helium isotope results recently published by tedesco et al 1 appear to show a decrease in 3he 4he since 1631 ad at mount vesuvius the authors proposed that this change is the result of a residual magma with a fractionated low 3he 4he ratio produced by preferential degassing of 3he during historical time if such a process generally occurred in nature it would seriously hinder our ability to characterize the 3he 4he ratio of mantle source regions in proposing their model tedesco et al 1 disregarded the previously published data of graham et al 2 which showed no change in 3he 4he with time at vesuvius and implied that diierences between the two studies result from diierent methods of gas extraction in response we have reanalyzed several of the critical samples by fusion these new results are in complete agreement with our original analyses performed by crushing 2 and are completely at odds with any measurable change in the 3he 4he ratio of vesuvius lavas since 1631 ad 2 results

correlation between climate events in the north atlantic and china during the last glaciation episodes of massive iceberg release heinrich events 1 3 into the north atlantic ocean during the last glaciation were associated with recurring episodes of unusually cold north atlantic surface water bond cycles 4 and cold air temperatures over greenland dansgaard oeschger events 5 6 four of the youngest of these cold events have also been reported in climate records from sites outside the north atlantic region7 but until now the entire suite has been identified only in north atlantic marine sediments greenland ice core records and tentatively in french lake sediments8 here we examine grain size data from chinese loess and intercalated accretionary palaeosols of last glacial age for evidence of similar climate signals remote from the north atlantic region we see grain size maxima with ages that match those of the last six heinrich events which we interpret as an indication of the changing strength of the east asian winter monsoon which largely controls the transport and deposition of central asian aeolian dust thus it seems that these heinrich events have left their signature in the chinese loess record this is consistent with simulations of the glacial climate9 which imply that the climates of the north atlantic and china were linked by the effect of westerly winds

age dating and the orbital theory of the ice ages development of a high resolution 0 to 300 000 year chronostratigraphy using the concept of orbital tuning a continuous high resolution deep sea chronostratigraphy has been developed spanning the last 300 000 yr the chronology is developed using a stacked oxygen isotope stratigraphy and four different orbital tuning approaches each of which is based upon a different assumption concerning the response of the orbital signal recorded in the data each approach yields a separate chronology the error measured by the standard deviation about the average of these four results which represents the best chronology has an average magnitude of only 2500 yr this small value indicates that the chronology produced is insensitive to the specific orbital tuning technique used excellent convergence between chronologies developed using each of five different paleoclimatological indicators from a single core is also obtained the resultant chronology is also insensitive to the specific indicator used the error associated with each tuning approach is estimated independently and propagated through to the average result the resulting error estimate is independent of that associated with the degree of convergence and has an average magnitude of 3500 yr in excellent agreement with the 2500 yr estimate transfer of the final chronology to the stacked record leads to an estimated error of 1500 yr thus the final chronology has an average error of 5000 yr

helium and carbon isotope systematics of natural gases from taranaki basin new zealand abstract the chemical and isotopic compositions of gases from hydrocarbon systems of the taranaki basin of new zealand both offshore and onshore show wide variation the most striking difference between the western and south eastern groups of gases is the helium content and its isotopic ratio in the west the maui gas is over an order of magnitude higher in helium concentration up to 190 mol mol 1 and its 3he 4he ratio of 3 8 ra where ra the air 3he 4he ratio of 1 4 10 6 is approximately half that of upper mantle helium issuing from volcanic vents of the taupo volcanic zone in the se the kupe south and most kapuni natural gases have only a minor mantle helium input of 0 03 0 32 ra and low total helium concentrations of 10 19 mol mol 1 the 3he c ratio where c represents the total carbon in the gas phase of the samples measured including those from a recent study of on shore taranaki natural gases are generally high at locations where the surface heat flow is high the 3he co2 ratio of the maui gases of 5 to 18 10 9 is higher than the morb value of 0 2 to 0 5 10 9 a feature found in other continental basins such as the pannonian and vienna basins and in many high helium wells in the usa extrapolation to zero co2 3he and co2 c indicates 13c co2 values between 7 and 5 close to that of morb co2 the remaining co2 would appear to be mostly organically influenced with 13c co2 c 15 there is some evidence of marine carbonate co2 in the gases from the new plymouth field the radiogenic 4he content herad varies across the taranaki basin with the highest herad c ratios occurring in the maui field 13c ch4 becomes more enriched in 13c with increasing herad and hydrocarbon maturity because 3he 4he is related to the ratio of mantle to radiogenic crustal helium and 3he c is virtually constant in the maui field there is a correlation between rc ra where rc air corrected 3he 4he and 13c ch4 in the maui and new plymouth fields with the more negative 13c ch4 values corresponding to high 3he 4he ratios a correlation between 3he 4he and 13c co2 was also observed in the maui field in the fields adjacent to mt taranaki 2518 m andesitic volcano correlations of some parameters particularly co2 ch4 c2h6 ch4 and 13c ch4 are present with increasing depth of the gas reservoir and with distance from the volcanic cone

subaqueous calving margin morphology at mueller hooker and tasman glaciers in aoraki mount cook national park new zealand the subaqueous margins of calving glaciers have the potential to make significant contributions to glacier mass loss however to date very little is known about the morphology and development of subaqueous margins a unique combination of sub bottom profile and bathymetric data collected between 2008 and 2010 in proglacial lakes at mueller hooker and tasman glaciers in new zealand s southern alps reveal subaqueous ice ramps extending up to 510 m from the terminus of each glacier ice ramp surfaces are undulating and covered with a thick layer up to 10 m of unsorted sediment derived from supraglacial and englacial debris lateral moraines and deltaic deposits a cyclic calving pattern relatively stable lake level and the debris cover appear to control the development and maintenance of these ice ramps high subaerial retreat rates generally correspond to high subaqueous calving rates although the highest subaerial retreat rates are not associated with the largest ice ramp debris mantling the subaqueous ice ramp surfaces insulates the ice from melting and also reduces buoyant forces acting on the terminus comparisons with previous studies show that the ice ramps evolve over time with changes in glacier dynamics and water body properties

bulk rock and mineral chemistries and ascent rates of high k calc alkalic epidote bearing magmas northeastern brazil abstract a manifestation of the pan african brasiliano orogeny 700 550 ma in northeastern brazil was the emplacement of widespread neoproterozoic granitoids in diverse tectonic terranes among these plutons are the magmatic epidote bearing conceicao das creoulas caldeirao encantado murici and boqueirao plutons located close to the boundary between the alto pajeu and cachoeirinha salgueiro terranes the plutons are high k calc alkalic granodiorites to monzogranites with tabular k feldspar megacrysts pistacite atomic fe 3 fe 3 al in epidote in these granitoids ranges from 21 to 27 high oxygen fugacity log f o 2 19 to 13 and the preservation of epidote suggest that the magma was oxidized al in hornblende barometry indicates hornblende solidification between 6 and 8 kbar at 620 to 780 c according to the hornblende plagioclase thermometer zircon saturation thermometry attests to a near liquidus temperature range from 794 to 853 c partial corrosion of magmatic epidote in these four plutons occurred during an interval of no more than 10 30 years which corresponds to maximum magma ascent rates of 650 1000 m year diking associated with regional shearing probably facilitated rapid transport of granitic magma through hot continental crust at peak metamorphism and permitted survival of epidote that was out of equilibrium at the low pressure of final emplacement similarities between mineralogical composition chemistry and isotopic compositions end 0 60ga between 2 and 5 t dm from 1 2 to 1 3 ga 18 o values 10 v smow of these four plutons and neoproterozoic magmatic epidote bearing plutons elsewhere in northeastern brazil argue for similar metabasaltic mafic sources that had previously experienced low temperature alteration

calving processes and the dynamics of calving glaciers abstract calving of icebergs is an important component of mass loss from the polar ice sheets and glaciers in many parts of the world calving rates can increase dramatically in response to increases in velocity and or retreat of the glacier margin with important implications for sea level change despite their importance calving and related dynamic processes are poorly represented in the current generation of ice sheet models this is largely because understanding the calving problem involves several other long standing problems in glaciology combined with the difficulties and dangers of field data collection in this paper we systematically review different aspects of the calving problem and outline a new framework for representing calving processes in ice sheet models we define a hierarchy of calving processes to distinguish those that exert a fundamental control on the position of the ice margin from more localised processes responsible for individual calving events the first order control on calving is the strain rate arising from spatial variations in velocity particularly sliding speed which determines the location and depth of surface crevasses superimposed on this first order process are second order processes that can further erode the ice margin these include fracture propagation in response to local stress imbalances in the immediate vicinity of the glacier front undercutting of the glacier terminus by melting at or below the waterline and bending at the junction between grounded and buoyant parts of an ice tongue calving of projecting submerged ice feet can be regarded as a third order process because it is paced by first or second order calving above the waterline first order calving can be represented in glacier models using a calving criterion based on crevasse depth which is a function of longitudinal strain rate modelling changes in terminus position and calving rates thus reduces to the problem of determining the ice geometry and velocity distribution realistic solutions to the problem of modelling ice flow therefore depend critically on an appropriate choice of sliding law models that assume that basal velocities are controlled by basal drag can replicate much of the observed behaviour of calving glaciers with grounded termini but an important limitation is that they cannot be used to model floating glacier termini or ice shelves alternative sliding laws that parameterise drag from the glacier margins provide more flexible and robust ways of representing calving in ice sheet models such models can explain a remarkable range of observed phenomena within a simple unifying framework including downglacier increases in velocity and strain rates where basal and or lateral drag diminishes flow acceleration in response to thinning through time the tendency for glaciers to stabilise at pinning points in relatively shallow water or fjord narrowings the constraints on ice shelf stability and the contrasts in calving rates between tidewater and freshwater calving glaciers many unresolved issues remain however including the role played by the removal of backstress in the acceleration of retreating calving glaciers and the controls on melting at and below the waterline

helium isotope studies of geothermal fields in the taupo volcanic zone new zealand abstract we report new measurements of 3he 4he and ne on 69 samples of gas from geothermal fields in the central section of the ne sw trending taupo volcanic zone tvz we find 3 he 4 he ratios in the range 5 9 7 3 times the atmospheric ratio 5 9 7 3ra typical of subduction zone systems in some areas near the boundaries of the volcanic zone the ratio is much lower 2 4ra the values in the wairakei field are extremely uniform and vary by only a few per cent from 7 2 ra in contrast the wells in the ohaaki broadlands field show a striking factor of two variation with the west bank section characterised by values near 6 ra while the east bank section has values as low as 3 0 ra this suggests that mixing of two types of geothermal source fluids may be occurring at ohaaki broadlands an inverse relationship has been found between the 3 he 4 he ratio of the gases and the b cl ratios in the associated fluids thus the helium isotope ratios appear to be affected both by the flux of mantle helium associated with mantle subduction and also by the presence of sedimentary rocks beneath the geothermal field leaching by the hot ascending fluid of radiogenic 4he together with boron from the underlying high boron low chloride mesozoic greywacke basement is thought to be the cause of this inverse relationship the co 2 3 he ratio in the tvz exceeds the morb ratio by a factor of up to 100 with higher values corresponding to higher b cl fluid ratios suggesting that the greywacke may also be the major source of the co2 we have also measured argon concentrations and isotopes on 19 samples in the ohaaki broadlands area in order to further elucidate the nature of the striking helium isotope variations the argon isotope ratios are relatively close to atmospheric indicating that the majority of the argon comes from recirculated groundwater the simplified boiling model of mazor et al 1990 has been used to calculate the 3 he heat ratio in the ohaaki broadlands and wairakei fields the values obtained fall within the range previously reported for mid ocean ridge systems this model has been extended and has led us to the conclusion that compared to the 3 he 4 he ratio the 3 he 36 ar asw ratio is a much better indicator of the potential geothermal heat the 4 he 40 ar na where na non atmospheric ratio of both the high mantle derived and low crustal derived 3 he 4 he end members of the analyses reported here is about 3 6 but for samples with low 3 he 36 ar ratio this ratio falls to values below 0 5 the value of 3 6 is in the range which is expected for the radiogenic component and although considerably lower than that often found in subduction type mantle gases it is still within the accepted range of values

middle holocene environmental change in central korea and its linkage to summer and winter monsoon changes to trace the surficial responses of lowlands to past climate change we investigated 13c in total organic carbon toc c n ratios magnetic susceptibility ms and silicon si intensity directly proportional to concentration in wetland sediments collected from the gimpo area of central korea covering 6600 4600 cal yr bp two organic layers with high toc negatively depleted 13ctoc values 27 to 29 low ms values and low si intensities were found at 6200 5900 and 5200 4800 cal yr bp respectively these middle holocene wet periods corresponded to relatively intensified summer monsoon and solar activity periods the intervening dry period 5900 5200 cal yr bp with high ms high si and low toc corresponded to an intensified dust activity interval and stronger winter monsoon this multi centennial climatic fluctuation of wet periods 6200 5900 cal yr bp and 5200 4800 cal yr bp and an intervening dry period 5900 5200 cal yr bp in central korea was more synchronous with climate change in the arid inner part of china than with that in south china suggesting possible strong high latitude driven climatic influences e g north atlantic cooling events during the middle holocene

long term vegetation change and controlling factors in donghae area korea over the past 40 000years abstract determining the effect of climate change since the last glacial maximum lgm in the east sea sea of japan coastal region of korea has been difficult owing to a dearth of suitable paleoclimate proxies a 40 000 year carbon isotope 13c record from cave deposits collected from cheongok cave korea reveals both long term change and superimposed shorter term isotopic excursions the 13c value of the sedimentary organic matter a proxy for past vegetation change varied from 25 to 21 with lower values during the lgm and higher values during the holocene a pattern that is generally consistent with trends in total organic carbon content toc and magnetic susceptibility from the lgm to the late holocene the c4 plant abundance mainly grasses estimated using a simple binary mixing model increased from 15 to 45 this long term change resembles trends in biogenic opal production in the east sea sea surface temperature and global sea level more than it does asian summer monsoon strength long term changes in c4 plant abundance in eastern coastal areas of korea over the last 40 000 years were probably affected most strongly by sea level driven ocean circulation changes in the east sea coupled with continental ice volume changes low pco2 during the lgm was not sufficient to cause the expansion of c4 plant coverage without favorable climatic conditions

middle pleistocene climate and habitat change at zhoukoudian china from the carbon and oxygen isotopic record from herbivore tooth enamel the pleistocene deposits at zhoukoudian often referred to as the bpeking manq site contain dental remains from a diverse group of herbivores including equus sanmeniensis cervus elaphus cervus nippon megaloceros pachyosteus sus lydekkeri and dicerorhinus choukoutienensis the carbon and oxygen isotopic compositions of structural carbonate within the enamel of these teeth are used to reconstruct the paleodiet and paleoenvironment of the mammals the d 13 c values of enamel from zhoukoudian range from 2 3x to 13 0x indicating that these mammals consumed between 25 and 100 c3 plants the presence of significant amounts of c4 plants in the diets of some herbivore species indicates that at the onset of the middle pleistocene local habitats included mixed c3 c4 vegetation by approximately 470 000 yr ago c3 plants dominated the diets of herbivores studied suggesting that the abundance of c4 flora had decreased in the area for all deer analyzed in this study the values of d 13 c and d 18 o decrease substantially from about 720 000 to 470 000 yr ago this trend may be due to a strengthening of the winter monsoon during the middle pleistocene

paleosol nodules as pleistocene paleoclimatic indicators luochuan p r china abstract loess deposits with their interbedded paleosols in central china record the world wide climatic changes of the past 2 5 ma the carbon and oxygen isotopic compositions of carbonate nodules in a loess profile at luochuan record paleoclimatic and paleoecologic conditions of paleosol formation interglacial periods during the past several 100 000 years it appears that the climatic and ecologic conditions during different periods of paleosol s 1 s 8 formation interglacial periods were very similar at luochuan and are marked by a presence of a mixed c 3 and c 4 type flora or mixed grass and wood and or shrublands

a lower pleistocene to holocene terrestrial record from the eskisehir graben central anatolia paleoclimatic and morphotectonic implications abstract as one of the rare terrestrial archive with continuous sedimentation back to almost 1 ma in anatolia the eskisehir graben was investigated in outcrops and cores by multi proxy analysis regarding chronology and paleoclimatology the present study comprises significant implications for both the impact of climate changes on fluvial systems in the timescales of the milankovitch band and the controversial age and rate of the crustal extension in western anatolia our findings indicate that loi950 and 18ocarb which are indicators for the amount of soil carbonate and paleo temperature respectively are collectively capable of distinguishing between glacial and interglacial periods in the predominantly floodplain deposits of the graben infill secondarily loi550 and 13ccarb values further help this discrimination via primary production and composition of vegetation cover respectively pollen data albeit highly discontinuous due to poor preservation under subaerial conditions point out a steppe like vegetation cover where the forest components expand particularly in the wet interglacial periods in the other hand the chronological frame provided by astronomical calibration of certain proxy records strongly suggest that the eskisehir fault zone initiated as a boundary fault of a half graben some 900 ka the rate of vertical movement on its southern branch since the last 70 ka is unexpectedly high 2 3 mm a a phenomenon that requires urgent risk assessment analysis in the vicinity of the eskisehir city

the structure of the mokai geothermal field based on geophysical observations abstract the mokai geothermal area about 25 km northwest of taupo has only minor thermal manifestations with a natural heat output of about 6 mw in late 1976 a roving dipole resistivity survey was made in the area surrounding mokai springs since then an extensive schlumberger resistivity survey has been made using two spacings nominally 600 m and 1200 m covering an area of about 4 b v n 2 around the mokai area interpretation of all the resistivity data suggests the area of mokai geothermal field below which high temperatures may be expected at depth is about 12 16 km 2 low resistivities from soundings within this area indicate highly conductive saline geothermal fluids at a depth of about 60 m although below this the resistivity increases suggesting a lowering of porosity the interpretation of resistivity measurements suggests a considerable subterranean flow of geothermal fluids northward from the mokai geothermal field and a further 76 mw of heat is estimated to be carried by springs and seeps into the deeply incised waipapa stream a second low resistivity region occurs at the waikato river about 12 km north of the geothermal field with an area of 3 4 km 2 there are indications that this anomaly is caused by hot geothermal fluids and it is suggested here that these geothermal fluids have their origin at the mokai geothermal field on this basis an estimate of the total heat output of the mokai geothermal area is 400 160 mw temperature in a drill hole within the geothermal field as outlined by this study reach a maximum of 290 c

submarine hydrothermal activity and gold rich mineralization at brothers volcano kermadec arc new zealand brothers volcano of the kermadec intraoceanic arc is host to a hydrothermal system unique among seafloor hydrothermal systems known anywhere in the world it has two distinct vent fields known as the nw caldera and cone sites whose geology permeability vent fluid compositions mineralogy and ore forming conditions are in stark contrast to each other the nw caldera site strikes for 600 m in a sw ne direction with chimneys occurring over a 145 m depth interval between 1 690 and 1 545 m at least 100 dead and active sulfide chimney spires occur in this field and are typically 2 3 m in height with some reaching 6 7 m their ages at time of sampling fall broadly into three groups 4 23 and 35 years old the chimneys typically occur near the base of individual fault controlled benches on the caldera wall striking in lines orthogonal to the slopes rarer are massive sulfide crusts 2 3 m thick two main types of chimney predominate cu rich up to 28 5 wt cu and more commonly zn rich up to 43 8 wt zn geochemical results show that mo bi co se sn and au up to 91 ppm are correlated with the cu mineralization whereas cd hg sb ag and as are associated with the dominant zn rich mineralization the cone site comprises the upper cone site atop the summit of the recent main dacite cone and the lower cone site that straddles the summit of an older smaller more degraded dacite cone on the ne flank of the main cone huge volumes of diffuse venting are seen at the lower cone site in contrast to venting at both the upper cone and nw caldera sites individual vents are marked by low relief 0 5 m mounds comprising predominately native sulfur with bacterial mats vent fluids of the nw caldera field are focused hot 300 c acidic ph 2 8 metal rich and gas poor calculated end member fluids from nw caldera vents indicate that phase separation has occurred with cl values ranging from 93 to 137 of seawater values by contrast vent fluids at the cone site are diffuse noticeably cooler 122 c more acidic ph 1 9 metal poor and gas rich higher than seawater values of so4 and mg in the cone vent fluids show that these ions are being added to the hydrothermal fluid and are not being depleted via normal water rock interactions iron oxide crusts 3 years in age cover the main cone summit and appear to have formed from fe rich brines evidence for magmatic contributions to the hydrothermal system at brothers includes high concentrations of dissolved co2 e g 206 mm kg at the cone site high co2 3he negative d and 18oh2o for vent fluids negative 34s for sulfides to 4 6 sulfur to 10 2 and 15n2 to 3 5 vent fluid ph values to 1 9 and mineral assemblages common to high sulfidation systems changing physicochemical conditions at the brothers hydrothermal system and especially the cone site occur over periods of months to hundreds of years as shown by interlayered cu au and zn rich zones in chimneys variable fluid and isotopic compositions similar shifts in 3he 4he values for both cone and nw caldera sites and overprinting of magmatic mineral assemblages by water rock dominated assemblages metals especially cu and possibly au may be entering the hydrothermal system via the dissolution of metal rich glasses they are then transported rapidly up into the system via magmatic volatiles utilizing vertical 2 5 km long narrow 300 m diameter pipes consistent with evidence of vent fluids forming at relatively shallow depths the nw caldera and cone sites are considered to represent stages along a continuum between water rock and magmatic hydrothermal dominated end members

δ13c analyses of individual lignin phenols in quaternary lake sediments a novel proxy for deciphering past terrestrial vegetation changes this study of the sediments from sacred lake mount kenya demonstrates that 13 c analyses of individual lignin phenols can be used to assess past changes in the proportion of c 3 and c 4 plants within different plant groups in the lake catchment vegetation changes resulting from climatic and atmospheric changes since the last glacial maximum can be deduced from specific lignin phenols lignin a major biopolymer in vascular plants differs from n alkyl lipids in 1 its higher specificity and more quantitative representation of vascular plant input and 2 its major transport mechanism into the sediments by fluvial runoff as opposed to the greater importance of eolian transport for leaf waxes and pollen lignin 13 c data support the hypothesis that atmospheric co 2 concentration is an important factor controlling the vegetation in tropical mountain ecosystems and provide additional insights into past changes in vegetation structure specifically the 13 c values of p coumaric acid indicate the persistence of c 4 grasses during the late glacial when the lake level was lower than today suggesting that aridity also played a role in controlling the abundance of c 4 plants

fluid geochemistry of hydrothermal systems in the arica parinacota tarapaca and antofagasta regions northern chile we investigate the chemical and isotopic composition of water and gas thermal discharges from six hydrothermal systems in the tarapaca and antofagasta regions northern chile surire puchuldiza tuja pampa lirima pampa apacheta el tatio and torta de tocorpuri to determine the chemical physical conditions at the fluid source the chemical facies of the thermal discharges vary from na cl el tatio puchuldiza tuja and part of surire where so42 rich waters also occur to na ca2 cl so42 pampa lirima ca2 so42 hco3 torta de tocorpuri and ca2 so42 pampa apacheta the gas seeps are characterized by the dominance of co2 h2s and ch4 with n2 ar ratios that occasionally are up to 450 significant amounts of so2 and hcl are present at pampa apacheta water and gas geothermometry suggests that el tatio and puchuldiza tuja fluid reservoirs have relatively high reservoir equilibrium temperature up to 270 c gases from pampa apacheta apparently equilibrated at unusually high temperature for hydrothermal fluids up to 350 c being likely related to an active magmatic system as testified by the presence of highly acidic gas compounds such as so2 and hcl on the contrary low equilibrium temperatures were calculated for the surire fluids 200 c suggesting interactions of deep originated fluids with meteoric water at shallow depth shallow low temperature aquifers mask any signal of deep fluids in the pampa lirima and torta de tocorcupi thermal discharges despite the variations in temperatures he isotopic compositions and redox conditions of the fluid reservoirs consistently indicate a significant contribution from magmatic degassing although geophysical studies are necessary to better constrain the geothermal potential of northern chile the geothermometric estimations carried out in the present study indicate that el tatio pampa apacheta surire and puchuldiza tuja can be regarded as the most promising areas and deserve more detailed geological investigations

calving processes at a grounded ice cliff repeat photographs and field survey reveal the mechanism of short term ice cliff evolution at maud glacier a temperate lake calving glacier in new zea land calving is cyclic each cycle involving four stages 1 waterline melting and collapse of the roof of a sub horizontal notch at the cliff foot 2 calving of ice flakes from the cliff face leading to a growing overhang from the waterline upwards and crack propagation from the glacier surface 3 large but infrequent calving of slabs in response to the devel oping overhang returning the cliff to an initial vertical profile 4 rare subaqueous cal ving of a submerged ice foot results indicate that the rate controlling process is the speed of waterline melting and that calving rate is independent of water depth at least at time scales of weeks to months slowly calving lake terminating glaciers have mass balances more negative than land terminating glaciers but nevertheless advance and retreat in response to mass balance driven changes in ice velocity

separation of pedogenic and lithogenic components of magnetic susceptibility in the chinese loess palaeosol sequence as determined by the cbd procedure and a mixing analysis summary magnetic susceptibility variations in the chinese loess palaeosol sequences have been used extensively for palaeoclimatic interpretations the magnetic signal of these sequences must be divided into lithogenic and pedogenic components because the palaeoclimatic record is primarily reflected in the pedogenic component in this paper we compare two methods for separating the pedogenic and lithogenic components of the magnetic susceptibility signal the citrate bicarbonate dithionite cbd extraction procedure and a mixing analysis both methods yield good estimates of the pedogenic component especially for the palaeosols the cbd procedure underestimates the lithogenic component and overestimates the pedogenic component the magnitude of this eect is moderately high in loess layers but almost negligible in palaeosols the mixing model overestimates the lithogenic component and underestimates the pedogenic component both methods can be adjusted to yield better estimates of both components the lithogenic susceptibility as determined by either method suggests that palaeoclimatic interpretations based only on total susceptibility will be in error and that a single estimate of the average lithogenic susceptibility is not an accurate basis for adjusting the total susceptibility a long term decline in lithogenic susceptibility with depth in the section suggests more intense or prolonged periods of weathering associated with the formation of the older palaeosols the cbd procedure provides the most comprehensive information on the magnitude of the components and magnetic mineralogy of loess and palaeosols however the mixing analysis provides a sensitive rapid and easily applied alternative to the cbd procedure a combination of the two approaches provides the most powerful and perhaps the most accurate way of separating the magnetic susceptibility components