penetration of atlantic westerly winds into central and east asia abstract the geographical position of the convergence zone where the western atlantic climate system meets the asian winter monsoonal system depends on their relative strength these individual strengths are determined by the intensities of the air pressure gradients over the north atlantic and the siberian high pressure cell respectively since the factors that forced those gradients varied throughout glacial interglacial cycles the location of the convergence zone should have moved accordingly both the grain size characteristics of wind blown sediments and climate modelling prove that the atlantic influence extended remarkably far eastward at times the northeastern tibetan plateau was at the cross road of western and monsoonal influences during the last glacial this region was dominated by an atlantic signal with millennial scale climatic oscillations that are similar to the north atlantic marine and greenland ice core records in contrast that same region was only under monsoonal influence during the last interglacial it implies that the atlantic winds penetrated more vigorously eastward in full glacial conditions than in interglacial conditions

global marine gravity from retracked geosat and ers 1 altimetry ridge segmentation versus spreading rate 1 three approaches are used to reduce the error in the satellite derived marine gravity anomalies first we have retracked the raw waveforms from the ers 1 and geosat gm missions resulting in improvements in range precision of 40 and 27 respectively second we have used the recently published egm2008 global gravity model as a reference field to provide a seamless gravity transition from land to ocean third we have used a biharmonic spline interpolation method to construct residual vertical deflection grids comparisons between shipboard gravity and the global gravity grid show errors ranging from 2 0 mgal in the gulf of mexico to 4 0 mgal in areas with rugged seafloor topography the largest errors of up to 20 mgal occur on the crests of narrow large seamounts the global spreading ridges are well resolved and show variations in ridge axis morphology and segmentation with spreading rate for rates less than about 60 mm a the typical ridge segment is 50 80 km long while it increases dramatically at higher rates 100 1000 km this transition spreading rate of 60 mm a also marks the transition from axial valley to axial high we speculate that a single mechanism controls both transitions candidates include both lithospheric and asthenospheric processes

palaeo water depth estimation for a 600 year record from nam co tibet using an ostracod based transfer function a modern training set of ostracods from the large slightly saline lake nam co on the southeastern tibetan plateau is presented in total 44 samples covering the largest part of the lake and water depth from 2 to 93 m were taken there are eight ostracod species in surface sediments of nam co leucocytherella sinensis leucocythere dorsotuberosa fabaeformiscandona gyirongensis candona xizangensis candona candida ilyocypris cf mongolica eucypris gyirongensis and limnocythere inopinata in order of mean dominance a morphological variant of l dorsotuberosa the forma postilirata is an indicator form of deep water below the thermocline the 36 samples comprise a sufficient number of ostracods for analysis covering water depths between 3 7 and 89 3 m two transfer function models based on weighted average binomial regression wa br and weighted average partial least square regression wa pls using the programs excel and c2 were established to estimate past water depths of nam co transfer functions were applied to ostracod data from two short cores from nam co covering approximately the past 600 years model results show a lake level minimum occurring during the little ice age lia between about 1490 and 1760 ad this minimum corresponds to results from previous stable isotope analysis and indicates a lake level which was about 5 m below the present day level the more exact transfer function model wa pls was set up using c2 and revealed a higher correlation index r o f 0 91 and a lower standard error of 6 7 m however the more selective because of using indicator taxa only wa br model using excel r 0 88 standard error 10 6 m seems to represent palaeo water depths better at least for the studied short cores

paleoenvironmental and archaeological investigations at qinghai lake western china geomorphic and chronometric evidence of lake level history abstract qinghai lake located on the northeastern qinghai tibet plateau qing zang gaoyuan is china s largest extant closed basin lake its position relative to major asian climate systems makes it sensitive to global climate change the lake has been the subject of numerous paleoenvironmental investigations including dating of shoreline features around the lake basin here we report new age estimates of shoreline features geomorphic exposures and archaeological sites that contribute to the development of a lake level history for qinghai lake and a landscape model of the qinghai lake basin lake highstands above 3230 m 36 m above the modern lake level appear to date to late mis 5 70 110 ka the lake has had much more modest highstands since then no evidence of mis 3 lake stands higher than modern were found and early holocene highstands are no more than 12 m above modern if the age of highstands greater than 3230 m is confirmed through future work then the qinghai lake basin hydrologic balance prior to 70 ka was dramatically different than after that time including during the holocene a simple hydrologic balance model provides insights into the combination of precipitation evaporation and runoff generation needed to sustain the lake at 3260 m the highest shoreline observed a range of factors may explain the difference primarily the relative strength of the east asian monsoon the basin was apparently subject to extensive alluviation during mis 3 interrupted by widespread erosion and development of cryogenic features before and during the last glacial maximum lgm loess that presently drapes much of the lower basin landscape began to be deposited after the lgm 16 18 ka the landscape model outlined here has implications for archaeological visibility of early human occupation of the qinghai tibet plateau

geochemical differentiation and prehistoric procurement of obsidian in the mount taylor volcanic field northwest new mexico abstract recently due to an increasing number of analyses of archaeological obsidian worldwide the reporting of chemically differentiated and compositionally zoned obsidian producing rhyolite domes has increased while these studies have been important and furthered our knowledge of the potential chemical variability of rhyolite magmas as they relate to archaeological obsidians they are rarely made relevant to archaeological issues in northwestern new mexico the grants ridge source in the mount taylor volcanic field exhibits two compositionally differing glasses derived from the same magma source that also exhibit significant megascopic variability correlating with raw material quality while grants ridge was previously seen as a single source this study suggests that one of the localities was considered a more viable raw material in prehistory at least in the local area the grants ridge study indicates the value of more intensive investigations of archaeological obsidian sources in the southwest including systematic geoprospection and chemical analysis the wavelength and energy dispersive x ray fluorescence analysis reported here provides the first systematic study of this high silica archaeological obsidian source in the mount taylor volcanic field

sourcing ceramics with portable xrf spectrometers a comparison with inaa using mimbres pottery from the american southwest seventy five intact mimbres and jornada pottery sherds from the american southwest were analyzed by portable xrf and instrumental neutron activation analysis inaa examination of the data demonstrates that inaa and portable xrf results for elements common to both analyses can be used to construct similar compositional groups when individual compositional groups are compared to one another it is apparent that unambiguous separation of compositional groups is challenging by portable xrf given 1 the limited number of key discriminating elements that can be measured relative to inaa and 2 the relative analytical precision and accuracy of portable xrf for measurements of intact heterogeneous ceramics we conclude that sourcing intact ceramics by portable xrf is challenging and that bulk analytical measurements such as inaa remain a better approach for sourcing archaeological pottery

using portable energy dispersive x ray fluorescence edxrf analysis for on site study of ceramic sherds at el hibeh egypt as part of its geoarchaeological research program the el hibeh project of the university of california berkeley field tested at the site of el hibeh northern middle egypt the utility of a portable edxrf unit for obtaining geochemical analyses of pottery suitable for provenance and other ceramic classification studies when the geochemical ceramic data from the field test are combined with basic petrographic analysis for the pottery sample set compelling results are generated in particular a triangular scattergram using elemental iron strontium and rubidium data in parts per million provides excellent temporal and spatial separation of ceramic fabrics type origin and date the geochemical behavior of iron strontium and rubidium is discussed in relation to geological source materials utilized for pottery manufacture

early to mid holocene lake high stand sediments at lake donggi cona northeastern tibetan plateau china lake high stand sediments are found in three onshore terraces at lake donggi cona northeastern tibetan plateau and reveal characteristics of hydrological changes on lake shorelines triggered by climate change geomorphological processes and neo tectonic movements the terraces consist of fluvial alluvial to littoral lacustrine facies end member modeling of grain size distributions allowed quantification of sediment transport processes and relative lake levels during times of deposition radiocarbon dating revealed higher than modern lake levels during the early and mid holocene lake levels follow the trend of asian monsoon dynamics and are modified by local non climatic drivers site specific impacts explain fluctuations during the initial lake level rise 11 cal ka bp maximum lake extension reached 9 2 cal ka bp at 16 5 m above present lake level a p l l littoral and lacustrine sediment deposition paused during a phase of fluvial activity and post depositional cryoturbations at 8 5 cal ka bp when the lake level fell to 8 m a p l l after a second maximum at 7 5 cal ka bp lake level declined slightly at 6 8 cal ka bp probably due to a non climatic pulse that caused lake opening the level remained high until a transition towards drier conditions 4 7 cal ka bp though discontinuous high stand sediments provide a unique high resolution archive

ostracod distribution and habitat relationships in the kunlun mountains northern tibetan plateau abstract surface sediment samples were collected from the lakes heihai kusai haiding nuur and yan hu and from streams and ponds in the kunlun mountains at the northern margin of the tibetan plateau to investigate the sub fossil ostracod micro crustacean fauna of the region among 65 collected samples 46 ostracod shell rich samples were used to study the relationship between the ostracod distribution and specific conductivity sc of the water which ranged from 0 6 to 53 0 ms cm 1 a total of eleven ostracod species was identified from this region with about half of the species restricted to the tibetan plateau and its adjacent mountain areas and the other half representing holarctic taxa tonnacypris cf estonica and tonnacypris tonnensis are reported from the tibetan plateau for the first time leucocythere sp is the dominant species and ilyocypris cf bradyi is also relatively abundant the other seven species were recorded with limited abundances apparently due to lower sc tolerances leucocythere sp was recorded over the full sc range from 0 6 to 53 ms cm 1 eucypris mareotica is a typical brackish and saline water species which was found at sample sites with high sc 2 8 53 0 ms cm 1 in contrast leucocythere dorsotuberosa candona candida and eucypris afghanistanensis prefer freshwater to slightly oligohaline waters with sc 1 the sc optimum and tolerance range for each species were determined and compared to earlier reported data from other regions of central asia the results indicate that species assemblage data from fossil ostracod shells have a large potential to provide information on past sc levels and more general climate determined moisture conditions

obsidian hydration at high elevation archaic quarrying at the chivay source southern peru we examine obsidian hydration as a means to date archaeological sites at high elevation in the central andes and in particular quarry sites that are difficult to date by radiocarbon means the chivay obsidian source lies in a volcanic depression above the colca valley in arequipa peru 71 5355 s 15 6423 e at 4950 masl we compare obsidian hydration readings from one quarry and two workshop locations ninety one flakes from the quarry pit and 61 and 33 flakes from the workshops were analyzed for hydration bands of these 68 from the quarry and 54 and 33 respectively from the workshops produced at least one culturally meaningful hydration band as expected obsidian appears to hydrate slowly at this high elevation yet variation in hydration readings is low within stratigraphic contexts suggesting relatively narrow windows of knapping activities in each excavation level a small number of radiocarbon dates allow us to develop a preliminary hydration rate for chivay obsidian in this high elevation location hydration data indicate that intensive quarrying began by 3800 cal bc and stopped ca 2300 cal bc by contrast the two workshops appear to have been deposited 2900 and 1200 cal bc and 2700 and 2400 cal bc the data are consistent with an uptick in obsidian use by at least the terminal archaic period 2011 elsevier ltd all rights reserved

moving obsidian the case of antofagasta de la sierra basin southern argentinean puna during the late middle and late holocene abstract this paper presents the results of an xrf analysis on the provenience of 118 obsidian artifacts from archaeological sites of the antofagasta de la sierra basin catamarca province argentina dating to the late middle and late holocene c 4500 1100 bp the time span considered encompasses a local process of gradual transformation from hunter gatherer early agro pastoral groups to consolidated agro pastoral societies for this study non destructive elemental analysis of obsidian artifacts was conducted using two different x ray fluorescence spectrometers ed xrf this information was then supplemented by previous provenience results undertaken on 59 obsidian archaeological artifacts from the same area a comparative synthesis of chemical and macroscopic characterization of five obsidian sources located in southern argentinean puna is also presented the provenance of archaeological materials was assigned by comparison with twelve presently known argentine sources on this basis late middle and late holocene obsidian regional movement patterns differential distribution and use of this raw material are discussed furthermore this obsidian research lends support to the existence of exchange networks based on the use of different extra regional obsidian sources located in the northern argentinean puna

the last frontier in sourcing the hopes constraints and future for iron provenance research abstract the socioeconomic importance of iron to the populations that make use of it is evidenced by the metal s incorporation into nearly every aspect of life from domestic chores and agriculture to large scale building construction transportation and warfare yet while provenance analysis or sourcing has a long history of generating insights concerning the circulation of most other archaeological materials iron has languished in what seems a perpetual stage of method development the past decade to be sure has witnessed a flurry of new iron provenance research that displays increasing sophistication of both data acquisition techniques and statistical applications it has also exposed divergent stances on what can or should serve as an object s potential source practical achievements beyond localized case studies however are few this paper reviews current practice in iron provenance research and evaluates it in terms of ironmaking technology and the provenance postulate constraints to iron provenance success are identified in the unique attributes of iron and ironmaking technology as well as some of the sourcing strategies employed some novel approaches however do present opportunities to empirically evaluate longstanding models of iron production and distribution and to generate seeds for new models the effective implementation of these emerging research programmes will require more extensive sampling of sources and efforts to ensure comparability of inter laboratory data

did the hudson strait in arctic canada record the opening of the labrador sea abstract the hudson strait evans strait foxe channel hef is a major composite topographic feature that connects hudson bay and foxe basin with the labrador sea hudson strait is underlain by several fault controlled sub basins with a half graben geometry the sedimentary succession in the sub basins is thicker than the one preserved onshore and reaches a maximum of 2 6 km in the eastern part of the hudson strait the lower part of the offshore succession correlates with paleozoic rocks exposed in nearby islands but the nature and age of the upper part remains poorly constrained faults have a clear morphological expression strike wnw and ene dip predominantly toward the north and record an extensional tectonic event that predates an episode of shortening a model is proposed linking half graben development to the initial stages of extension in the future labrador sea and subsequent inversion to the kinematic decoupling of the labrador sea from the canadian landmass by the ungava fault zone

macusani obsidian from southern peru a characterization of its elemental composition with a demonstration of its ancient use transparent obsidian artifacts have been reported for the northern lake titicaca basin based on instrumental neutron activation analysis inaa of these artifacts a distinct chemical group was identified yet the location of the source of transparent obsidian in the southern andes remained unreported in the archaeological literature this paper reports on the chemical composition and geographic location of a source of transparent obsidian from the macusani region of peru through the use of inaa and portable x ray fluorescence pxrf we demonstrate that macusani obsidian or macusanite comprises at least two chemical groups one of these groups was used for making artifacts during the archaic period artifacts made of this obsidian were found more than 120 km from the source and yet one third of the obsidian artifacts encountered at macusani were from the non local source of chivay which is 215 km to the southwest

tongan and samoan volcanic glass pxrf analysis and implications for constructs of ancestral polynesian society a provenance study of volcanic glass specimens from 12 archaeological sites in the kingdom of tonga is carried out employing pxrf portable x ray fluorescence analysis to accomplish this volcanic glass samples from previously identified sources in northern tonga and the adjacent islands of samoa are analyzed results indicate inter island voyaging and interaction over a 600 km linear distance along the tongan island chain from first lapita settlement ca 2900 bp throughout later prehistory tongan volcanic glass however is not found in samoa and with the exception of one late prehistoric specimen samoan volcanic glass is not present in tonga this distribution challenges current concepts of an integrated ancestral society and homeland common to tonga and samoa from the lapita period onward

chemical soil surveys at the bremer site dakota county minnesota usa measuring phosphorous content of sediment by portable xrf and icp oes abstract the bremer site lies along the shores of spring lake in southeastern minnesota and excavations in the 1950s uncovered evidence of woodland and mississippian occupation phases in 2011 a new program of systematic survey and excavation began to better understand cultural patterning and diachronic changes at the bremer site the investigations came to include microarcheaological methods including sediment micromorphology and soil chemistry no element has received more archaeological attention than p which can reflect human and animal waste organic refuse burials and ash there has been interest in integrating soil chemistry into the workflow of fieldwork and in the potential of portable analytical instruments to yield data within the timeframe of an excavation season the last few years have seen the rise and proliferation of portable xrf pxrf instruments in archaeological studies the newest generation of pxrf instruments is able to quantify p at low concentrations and our focus here is developing effective methods to do so in archaeological soils and sediments using sediments from the bremer site we evaluate two preparation techniques in order to find which one best balances analytical quality and preparation time to analyze as many specimens as possible during an excavation season it is desirable to identify adequate preparation methods as well as the smallest number of analyses needed to attain reasonable confidence levels regarding repeatability we show that to attain p values with a standard error better than 10 or 20 of the mean one or two analyses per specimen are sufficient in a majority of cases regarding reproducibility we compare the pxrf data to two independent icp oes datasets ultimately these tests aid in establishing methods that enable archaeologically significant pxrf analyses of soil p concentrations even when working far from an analytical laboratory

hydroclimatic changes in china and surroundings during the medieval climate anomaly and little ice age spatial patterns and possible mechanisms abstract investigating hydroclimatic changes during key periods such as the medieval climate anomaly mca 1000 1300 ad and the little ice age lia 1400 1900 ad is of fundamental importance for quantifying the responses of precipitation to greenhouse gas induced warming on regional and global scales this study synthesizes the most up to date and comprehensive proxy moisture precipitation records during the past 1000 years in china and surroundings the proxy data collected include 34 records from arid central asia aca and 37 records from monsoonal asia our results demonstrate a pattern of generally coherent regional moisture variations during the mca and lia in mid latitude asia north of 30 n monsoonal northern china north china and northeast china was generally wetter while aca northwest china and central asia was generally drier during the mca than in the lia a west east mode the boundary between wetter northern china and drier aca was roughly consistent with the modern summer monsoon boundary in monsoonal china to the east of 105 e the northern part was generally wetter while the southern part was generally drier during the mca than in the lia a north south mode with a boundary roughly along the huai river at about 34 n these spatial patterns of moisture precipitation variations are also identified by instrumental data during the past 50 years in order to understand the possible mechanisms related to the moisture variations during the mca and lia we investigate the major sst and atmospheric modes e g the el nino southern oscillation enso the atlantic multidecadal oscillation amo and the north atlantic oscillation nao which affect the moisture precipitation variations in the study region using both the instrumental data and the reconstructed time series it is found that the enso may play an important role in determining hydroclimatic variability over china and surroundings on a multi centennial time scale and that the foregoing spatial patterns could be attributed to the la nina like el nino like condition during the mca lia in addition amo and nao may also have their own contributions

comparison of surface and shipborne gravity data with satellite altimeter gravity data in hudson bay several free satellite altimetry models in the public domain may be used to study the earth s gravity field in this study we compare the bouguer anomaly map of the hudson bay region calculated from the satellite derived v18 model of d sandwell scripps institution of oceanography and w smith national oceanic and atmospheric administration with one compiled from measurements gsc data set made on the ice shelf and by ship noise exists in both data sets and takes the form of linear anomalies along ship tracks on the gsc map and of random high frequency anomalies on the map derived from satellite altimetry spectral analysis of both maps indicates a good correspondence for anomalies wider than 15 km in central hudson bay the mean difference between the two maps is 1 6 mgal indicating only a small offset between the two data sets standard deviation of the difference is 2 35 mgal the correspondence between anomaly shapes on profiles indicates that satellite derived gravimetry is certainly good en

reduced early holocene moisture availability in the bayan har mountains northeastern tibetan plateau inferred from a multi proxy lake record abstract a late glacial and holocene lake sediment record from the northeastern tibetan plateau was investigated using ostracod and geochemical analysis after lake koucha was established about 16 cal ka bp oligohaline conditions gradually converted to mesohaline conditions about 10 cal ka bp clearly suggesting that the water body was a closed basin lake from about 10 cal ka bp the salinity of the lake rose continuously until hyperhaline levels were reached about 7 5 cal ka bp this increase in salinity was accompanied by a falling lake level extreme rainfall and flooding events in a generally dry climate hit the shallow saline lake around 8 5 cal ka bp causing a unique thin gravel containing layer within the continuous fine grained lake sediments the age control of our record does not allow us to correlate this event exactly to the widely recorded 8 2 cal ka bp event however the recovered sediments from lake koucha provide strong evidence that climate changes around 8 5 cal ka bp had significant environmental implications in northeastern tibet after about 7 3 cal ka bp the available moisture significantly increased causing a continuous salinity decline until the present day freshwater conditions of a through flow lake were established about 6 5 cal ka bp in lake koucha this major shift from a shallow saline to a deeper freshwater lake was probably accompanied by a fundamental change from a macrophyte dominated to a phytoplankton dominated lake a slight reduction in available moisture in comparison to the periods before and afterward was recorded between 4 3 and 2 0 cal ka bp in phase with numerous records from monsoonal asia the reconstructed overall change in moisture availability from dry conditions before about 7 3 cal ka bp to wetter conditions afterwards contradicts most palaeoclimate records from the tibetan plateau and its surroundings which show that wetter conditions in the early holocene were replaced by drier and probably cooler conditions in the mid and late holocene however in the semi arid region of lake koucha with a mean annual precipitation of about 500 mm the insolation driven strengthened monsoon in the early holocene may have resulted in a temperature rise and higher evaporation rates which outweighed the increase in precipitation and therefore led to significantly lower moisture availability our record provides further evidence for a regionally non uniform response of the available moisture evolution to the overall monsoonal signal in the holocene climate history of central asia

ten seconds in the field rapid armenian obsidian sourcing with portable xrf to inform excavations and surveys armenia has one of the most obsidian rich natural and cultural landscapes in the world and the lithic assemblages of numerous palaeolithic sites are predominantly if not entirely composed of obsidian recent excavations at the middle palaeolithic cave of lusakert 1 recovered on average 470 obsidian artifacts daily after sourcing more than 1700 artifacts using portable xrf pxrf in our field house our team sought to shift pxrf based obsidian sourcing into the field itself believing that the geological origins of artifacts would be useful information to have on site during an excavation or survey despite increasing use of portable instruments previous studies have principally focused on collections in museums and other archives and as a result obsidian sourcing has remained embedded in post excavation studies one critical factor in the uptake of obsidian sourcing in the field is the time needed to measure each artifact frequently 2 6 min in previous studies here we report our two methods of obsidian sourcing including source matching done automatically by the pxrf instrument s onboard software in only 10 s our tests with armenian geological specimens and palaeolithic artifacts demonstrate the high efficacy of our two methods which are sufficiently fast to become syncopated with our excavation and survey activities by reducing measurement times from a mode of 300 s in recent studies to just 10 s here we show how and why to shift pxrf based obsidian sourcing from the context of white lab coats to that of muddy boots

non destructive geochemical and magnetic characterisation of group xviii dolerite stone axes and shaft hole implements from england thirty five polished stone axes and shaft hole implements which had been previously assigned by petrographic partially destructive study to group xviii assumed to be from the whin sill dolerite source in northern england were characterised non destructively using a combination of portable x ray fluorescence analysis pxrf and magnetic susceptibility measurements all the implements were compared with the whin sill and with other petrologically and or visually similar rock sources in the north of england and in scotland using a database of chemical elements constructed from the published literature and statistical atypicality testing twenty nine of the implements are good matches for the whin sill as expected but three do not match whin sill rocks and may therefore need to be re assessed as members of group xviii a further three implements have ambiguous characteristics perhaps as a result of surface weathering one axe an axe hammer and an adze that had not previously been assigned to implement groups were also analysed as a test of the robustness of the non destructive methods all three implements could be distinguished from group xviii on the basis of chemical and magnetic characteristics most of the distribution of group xviii implements is best explained by the opportunistic use of glacial erratics rather than trade from the primary source possible alternative sources for the non group xviii implements include the scottish old red sandstone age lavas which could also have been obtained as erratics the chemical and magnetic characteristics established in this paper provide a non destructive alternative to thin section study of potential group xviii artefacts

methanogenic pathways 13c isotope fractionation and archaeal community composition in lake sediments and wetland soils on the tibetan plateau 1 lakes are a significant source of atmospheric ch4 and play an important role in the global carbon cycle little information on methane production in high altitude lakes is available we determined the methanogenic archaeal community composition the methanogenic pathways and carbon isotope fractionation in lake sediments and wetland soils on the tibetan plateau at about 4000 m above sea level asl we measured ch4 production rates and the 13c of co2 ch4 and acetate in the presence and absence of methyl fluoride an inhibitor of acetotrophic methanogenesis in sediments of five lakes awong co bangong co gongzhu co daze co and ranwu and wetland soils adjacent to bangong co and ranwu methane in bangong co sediment and in the wetland soil near ranwu was mainly produced by acetotrophic methanogenesis whereas methane in the sediments of the two saline lakes awong co and gongzhu co was mainly generated by hydrogenotrophic methanogensis chemolithotrophic acetogenesis and methanol dependent methanogenesis may also have played a role the stable carbon isotope fractionation during ch4 production from co2 was relatively large average e 78 the methanogenic communities were similar to those found in lowland lake sediments but those of saline and nonsaline tibetan lakes differed hydrogenotrophic methanogens were dominant in lake sediments while acetotrophic methanogens were dominant in wetland soils our results revealed diversity in the methanogenic communities and their methanogenic pathways and indicated that they are affected by sediment characteristics such as salinity however the ch4 production rates ranging from 6 to 122 nmol day 1 g dry weight 1 showed no relationship to environmental characteristics and were not limited by microbial abundance

pxrf characterisation of obsidian from central anatolia the aegean and central europe the obsidian sources of central anatolia the aegean and central europe have been studied in detail over the past 50 years various analytical techniques have been employed to discriminate artefacts from each of these and to reconstruct their zones of distribution this paper presents a pxrf method that allows mass sampling of artefacts focusing on three neighbouring regions particularly where these zones overlap successful discrimination of the obsidian source for products could be achieved using three dimensional scatter plots of trace elements rb sr zr pxrf can thus be appreciated as a powerful tool in the region enabling non destructive on site analyses in contexts where the export of artefacts is often difficult if not impossible the ability to rapidly process large assemblages also has major implications for generating data sets of sufficient resolution to transform archaeological interpretation

wetland evolution in the qinghai lake area china in response to hydrodynamic and eolian processes during the past 1100 years abstract the daotanghe riverine wetland in close proximity to the qinghai lake was investigated to demonstrate the interrelationships between qinghai lake hydrodynamic processes eolian mobility and ecological conditions during the past 1100 years in response to climate change we used ostracod assemblages from various sites east of qinghai lake and from the sediment core qw15 of daotanghe pond and combined them with grain size and geochemical data from the same core the statistical extraction of grain size endmembers em revealed three different transportation processes responsible for pond related fluvio lacustrine pure fluvial and eolian deposits identified seasonal effects eolian mobility phase and timing of ice cover are possible tracers for the competing influence between the asian summer monsoon and the westerlies in the daotanghe wetland and surrounding area our results show that ostracod associations and sediment properties are evidence of a fluvio lacustrine fresh water environment without ingression of qinghai lake into the wetland hydrodynamic variations coupled with phases of eolian input indicate highly variable water budgets in response to climate induced effective moisture supply the medieval warm period mwp until about 1270 ce displays generally moist and warm climate conditions with minor fluctuations likely in response to variations in summer monsoon intensity the three partite period of the little ice age lia shows hydrologically unstable conditions between 1350 and 1530 ce with remarkably colder periods assigned to a prolonged seasonal ice cover pond desiccation and replacement by fluvial deposits occurred between 1530 and 1750 ce superimposed by eolian deposits the phase 1730 1900 ce is recorded by the re occurrence of a pond environment with reduced eolian input principal component analysis pca on ostracod abundances shows similar trends all three phases of the lia developed during a weak summer monsoon influence favoring westerly derived climate conditions until ca 1850 ce in accordance with records from the adjacent regions seasonal freezing periods in excess of the average time of frozen water bodies also occurred in periods of the well known grand solar minima and indicate stronger seasonality possibly independent from variations in summer monsoon strength but with links to global northern hemispheric climate

characterization of new zealand obsidian using pxrf abstract new zealand has some of the most active areas of rhyolitic volcanism in the world and this has produced numerous obsidian sources in the northern half of the north island in total archaeologists have recognized 27 named locations from which obsidian can be obtained scattered across 4 geological source regions shortly after colonization in the late 13th century ad polynesian settlers began transporting this material some thousands of kilometers throughout the country and across the sea in small quantities to distant neighbors in the kermadecs and chatham islands although considerable research has been conducted on obsidian sourcing in new zealand the complexity of geochemical source discrimination and the lack of a practical method of non destructive geochemical analysis has hindered progress we present the results of our use of pxrf to provide geochemical data on new zealand obsidian sources and to compare the use of discriminant analysis and classification tree analysis to discriminate among sources and attribute archaeological samples to sources our research suggests that classification tree analysis is superior to discriminant analysis in sourcing studies a large case study using an important settlement phase site s11 20 from the auckland region demonstrates the utility of the methods and the results support a model of high degrees of mobility and interaction during the early settlement of new zealand

new gravity data in the arctic ocean comparison of airborne and ers gravity new gravity fields from airborne gravimetry and from ers 1 and 2 satellite altimetry cover extensive portions of the arctic ocean these two data sets may constitute as much as 60 of the data contributions to the arctic gravity project compilation here we evaluate the accuracy and resolution of these data and quantify their impact on the compilation both gravity determinations compare favorably with geological survey of canada surface measurements in the beaufort sea airborne 1 86 2 09 mgal rms ers 2 64 3 11 mgal rms comparisons between the airborne and ers data over the chukchi borderlands reveal a 4 38 mgal rms difference over the smoother region of the field and 7 36 mgal rms over the rugose field generated by the shallow ridges and deep troughs coherency between the two data sets in the chukchi region implies a resolution of 19 km comparison with science ice expedition submarine measurements over chukchi plateau suggests that the ers field resolves even shorter wavelength signal than the airborne data whereas in the beaufort sea the airborne data showed better coherence to ground truth data long wavelength differences exist between the two data sets expressed as a 2 3 mgal offset over the chukchi region this study highlights the respective strengths of the two data sets the ers gravity field has the advantage of ubiquitous coverage of the ocean south of 81 5 degreesn a denser sampling of the gravity field and a recovery of signal down to similar to 15 km the airborne data cover a significant portion of the polar hole in the satellite coverage have lower measurement noise and recover somewhat higher anomaly amplitudes in the 25 100 km wavelength range

geomorphological and palaeoclimate dynamics recorded by the formation of aeolian archives on the tibetan plateau abstract aeolian sediments are an important archive for palaeoclimate reconstructions on the tibetan plateau the accumulation of aeolian sediments and the formation of palaeosols are used as a proxy for dry and wet phases respectively during the last decade the number of osl optically stimulated luminescence ages of aeolian sediments has been rapidly increasing this study summarises the results from more than 300 individual osl ages despite the widespread occurrence of aeolian sediments on the tibetan plateau nearly all osl samples are located on the northeastern and the southern part in most regions the strongest accumulation occurred during the late glacial and in the early holocene this coincides with the strengthening of the asian summer monsoon on the tibetan plateau and wetter climate conditions after the relatively dry glacial times the development of a sufficient vegetation cover acting as a sediment trap seems to be an important requirement for the preservation of aeolian archives short dry periods like the younger dryas led to a more enhanced aeolian accumulation without destruction of previously formed archives in some regions the formation of palaeosols occurred mainly during the wet early and mid holocene but the number of ages is relatively small in contrast a second phase of aeolian accumulation during the late holocene was related to the weakening of the asian summer monsoon and drier climate conditions this indicates that the reaction of aeolian accumulation on the tibetan plateau depends on the previous climate state a comparison between the osl ages from aeolian sands and loess deposits yields a different timing of deposition of these two sediment types while the sand deposits in different basins resemble wet and dry phases loess deposits show no common signal between the analysed areas this indicates an influence of local factors such as varying source areas and erosive processes on the slopes in general the aeolian archives in the high mountain environment are governed by numerous factors besides the climatic influence

palaeoclimatic changes in the qinghai lake area during the last 18 000 years abstract multi proxy analysis of a sediment core from qinghai lake including pollen carbonate toc tn and 13 c of organic matter was used to document regional climatic changes during the last 18 000 years climate was very cold and dry before 16 9 cal kyr bp the warm and wet period which began at about 14 1 cal kyr bp culminated at 6 5 cal kyr bp and came to its end at about 4 5 cal kyr bp after that the climate gradually became colder and drier during the transitional period from the late glacial to the holocene the climate fluctuated frequently the short term climatic oscillations including the bolling allerod younger dryas and the cooling event at ca 8 2 cal kyr bp appear to be recorded in the qinghai lake sedimentary record the climatic evolution in the qinghai lake area during the past 18 000 years indicates that solar insolation changes on the ten thousand year scale are the likely driving force of the east asia monsoon

early to mid holocene lake high stand sediments at lake donggi cona northeastern tibetan plateau china comment to the paper published by dietze et al quaternary research 79 2013 325 336

testing the accuracy of portable x ray fluorescence to study aztec and colonial obsidian supply at xaltocan mexico abstract this article demonstrates the accuracy of non destructive portable x ray fluorescence p xrf for the study of obsidian in central mexico obsidian sources were identified for a sample of 103 artifacts from the site of xaltocan which spanned the rise and fall of the aztec empire and the first centuries of spanish colonial rule ad 900 1700 sources were assigned by comparing p xrf measurements with previously published source data and were verified using the standard techniques of laboratory xrf l xrf and instrumental neutron activation analysis inaa additional tests of potentially confounding factors show that neither length of read time presence of surface residue nor incomplete detector coverage due to small artifact size compromised our ability to attribute sources to artifacts concave surfaces did decrease the accuracy of readings because of the greater distance between the artifact and the detector our results provide new insight into the stability of supply networks and markets well into the colonial period as well as the homogenizing tendencies of the aztec market system

satellite derived gravity having an impact on marine exploration converting sea surface height variations derived from satellite altimetry to free air gravity is not new in the early 1980s william haxby lamont doherty geological observatory produced the first global marine gravity map from seasat satellite altimeter data using interorbital track spacing of about 180 km haxby s map had a significant impact on plate tectonic theory because marine free air gravity data were able for the first time to uniformly image the tectonic fabric of the earth s oceanic crust since that time much effort has been applied to improving satellite derived gravity resolution a major advance occurred in 1995 when the altimeter data from geodetic missions gm of geosat and ers 1 satellites were released table 1 gives details of these satellites

lake level variations of qinghai lake in northeastern qinghai tibetan plateau since 3 7 ka based on osl dating abstract qinghai lake is the largest internally drained lake in china and its unique location makes it sensitive to climate changes late glacial climate changes associated with variation in qinghai lake levels have been intensively investigated for the past 40 years with particular attention paid to lake level fluctuation histories between the last interglacial and the holocene however the details of lake level fluctuations during the holocene are still unclear using both optically stimulated luminescence osl dating of quartz for 22 samples and infra red stimulated luminescence irsl of feldspars only for sample hyw1 whose irsl age is 37 15 years a total of 23 samples are dated from paleoshoreline deposits fluvial sediments and aeolian sands a total of 13 sections near the modern lake shore with ages from 37 15 to 3710 350 years these ages are used to reconstruct the lake level fluctuation history spanning the last 3700 years the results indicate that 1 the youngest irsl age of 37 15 years is in agreement with the independent age of 39 29 years suggesting that luminescence dating is able to date decadal samples for sediments from the study area 2 the lake experienced several oscillations imposed on an overall regressive trend during the past 3700 years 3 the dated paleoshoreline deposits are generally related to warm and wet periods suggesting that those shoreline deposits formed during cold and dry periods if any may have been modified by later transgressions 4 lake level fluctuations during the period of 3700 240 years ago are generally consistent with the climate conditions identified in other proxies with the highest lake level occurring about 1770 years ago and 5 after 240 years ago the lake level dropped more rapidly which is inconsistent with the proxy records showing a warmer and wetter phase

evaluation of oxygen isotopes in carbonate as an indicator of lake evolution in arid areas the modern qinghai lake qinghai tibet plateau abstract the oxygen isotopic composition of carbonate in lakes has been used as a useful indicator in palaeolimnological research and has made some important contributions to our understanding of lacustrine systems for modern lakes in arid or cold areas however there are few data available to test the effect of lake salinity and temperature on the oxygen isotopic composition of various carbonate sources such as ostracod bulk carbonate and fine grained carbonate for arid high altitude lake qinghai our results suggest that variations in the 18o values of carbonate in lake qinghai are mainly controlled by the oxygen isotope ratio of the lake water changing with water salinity as a secondary effect increasing water depth leads to cooler bottom and surface water which may result in more positive 18o values of ostracod and bulk carbonate

realising the potential of portable xrf for the geochemical classification of volcanic rock types abstract the ability to geologically classify stone artefact materials is crucial because it is the first step in provenance allocation and geochemical grouping that inform archaeological models used for understanding exchange systems within prehistoric social networks geochemical analyses have revolutionised exchange studies by making it possible to match stone artefacts back to quarry sources sometimes hundreds or thousands of kilometres away most archaeological basalt characterisation and provenance studies have relied on destructive sampling techniques to obtain the major trace elements nao2 k2o and sio2 wt to identify volcanic rock types on the total alkali silica tas diagram to overcome this limitation this paper presents an alternative method the pearce w f diagram that determines volcanic rock type and alkalinity using elements tio2 zr y and nb that are accurately detected by non destructive portable x ray fluorescence pxrf this new method is proven to be effective in a comparison with recent xrf archaeological basalt studies in the pacific the power to classify volcanic rock types non destructively with pxrf significantly increases the number of artefacts and museum objects available for inclusion in archaeological exchange studies

assessing the applicability of portable x ray fluorescence spectrometry for obsidian provenance research in the maya lowlands recent innovations in portable energy dispersive x ray fluorescence pxrf spectrometry have increased its utility for the geochemical characterization of obsidian artifacts for archaeological provenance research however concerns over the utility of pxrf instrumental analyses have been raised focused on the validity and reliability of the geochemical data produced here we adopt the framework of richard hughes on reliability validity and scale in obsidian sourcing research 1998 whereby reliability addresses instrument stability and issues of measurement while validity pertains to an instrument s ability to discern geochemical source provenance this is done in order to test the utility of pxrf instruments for archaeological provenance research k means cluster analysis was used to test the accuracy of pxrf through statistical comparison of data acquired via laboratory and portable energy dispersive xrf instruments multivariate analysis was employed to demonstrate obsidian source representation at two classic maya archaeological sites in southern belize uxbenka and ek xux and to test the validity of data obtained from a pxrf instrument in answering archaeological research questions pertaining to regional interactions between lowland maya polities results suggest that portable xrf instruments produce internally consistent results however data acquired from a pxrf instrument are not statistically equivalent to other xrf instruments this is to say that while pxrf is not a reliable technique it is valid for questions pertaining to geochemical source representation

comparison of xrf and pxrf for analysis of archaeological obsidian from southern peru abstract chemical sourcing is becoming an increasingly important component of archaeological investigation instruments used for elemental analysis generally must be operated in a controlled laboratory environment further many methods require destruction of a small portion of the objects under investigation these facts inhibit the application of chemical sourcing studies in a number of research contexts use of portable non destructive instruments would resolve these issues sixty eight obsidian artifacts from the site of jiskairumoko in southern peru were examined by x ray fluorescence spectrometry xrf and portable x ray fluorescence spectrometry pxrf results were compared for consistency in terms of source determination and individual element concentrations both instruments determined that the same sixty six artifacts derived from the chivay obsidian source and both identified the same two artifacts that could not be assigned to source individual element comparisons showed significant differences but these can be resolved through instrument cross calibration and differences had no bearing on source identification pxrf was found suitable for determining obsidian sources in southern peru and for identifying specimens that require more sensitive analytical methods such as instrumental neutron activation analysis inaa regular use of chivay at jiskairumoko suggests consistent trade relationships developed during the archaic

evaluating effects of chemical weathering and surface contamination on the in situ provenance analysis of building stones in the cuzco region of peru with portable xrf as the only type of instrument capable of determining artifact geochemistry in a wide variety of settings portable x ray fluorescence pxrf may be frequently utilized as probably the best option for collecting data when removal of objects in part or in whole is unfeasible however using pxrf in circumstances where sample selection and preparation diverge from standards developed for lab based instrumentation requires assessing the impact of new and potentially limiting factors to establish the validity of the method in these new contexts here we examine the effects of surface contamination and chemical weathering on the ability to assess provenance of igneous building stones used in the cuzco region of peru surface contamination was assessed through comparing low impact cleaning methods on diorite and andesite blocks and weathering was examined by comparing weathered vs fresh surfaces of samples from two andesite quarries in general the lightest elements were most impacted by contamination and weathering while measurements of many of the heavier elements commonly used in provenance studies were relatively unaffected concentrations of pb and zn were problematic in the urban context of cuzco because of pollution ability to determine provenance of building stones within those limitations i e the validity of this application of pxrf was demonstrated in a preliminary study by comparing measurements from uncleaned exposed building stones in the region to fresh quarry samples

holocene moisture evolution in arid central asia and its out of phase relationship with asian monsoon history we synthesize palaeoclimate records from the mid latitude arid asian region dominated today by the westerlies arid central asia aca to evaluate spatial and temporal patterns of moisture changes during the holocene sediment records from i i takes with reliable chronologies and robust proxies were selected to reconstruct moisture histories based on a five class ordinal wetness index with assigned scores from the driest to wettest periods at individual sites for 200 year time slices the proxies used in these records include pollen and diatom assemblages sediment lithology lake levels and geochemistry mainly isotope data the results of our synthesis show that aca as a whole experienced synchronous and coherent moisture changes during the holocene namely a dry early holocene a wetter less dry early to mid holocene and a moderately wet late holocene during the early holocene most of the lakes experienced very low water levels and even dried out before ca 8 ka 1 ka 1000cal a bp hence the effective moisture history in aca is out of phase with that in monsoonal asia as documented by numerous palaeoclimate records in monsoonal asia a strong summer monsoon and humid climate characterized the early holocene and a weakened summer monsoon and drier climate prevailed during the late holocene which were mainly controlled by changes in low latitude summer insolation in contrast we propose that the pattern of holocene effective moisture evolution in the westerly dominated aca was mainly determined by north atlantic sea surface temperatures ssts and high latitude air temperatures that affect the availability amount and transport of water vapor also topography of the tibetan plateau and adjacent asian highlands could have contributed to the intensification of dry climate in aca during the early holocene as a result of strengthening the subsidence of dry air masses associated with stronger uplift motion on the plateau by intense heating under a stronger summer insolation summer insolation might have played a key role in directly controlling moisture conditions in aca but only after the northern hemisphere ice sheets had disappeared in the mid and late holocene c 2007 elsevier ltd all rights reserved

dry periods on the ne tibetan plateau during the late quaternary abstract environmental conditions on the tibetan plateau are changing rapidly this study reconstructs late quaternary environmental changes on the northeastern tibetan plateau based on sand deposits the study area is located close to the present maximum extent of the east asian summer monsoon and is likely to register shifts in monsoon extent furthermore different sediment deposits are available that allow reconstruction of sediment pathways between the different archives sediment deposition in the catchment is dominated by deposition of sand sandy deposits in the form of dune fields and sand sheets are widespread on the northeastern tibetan plateau and are an important archive for paleoclimatic reconstruction this study shows that sand deposits on the northeastern tibetan plateau are local phenomena that still bear the sedimentological and geochemical fingerprint of their source materials reconstruction of transport processes in the local sediment cascade shows that local sand deposits are the main source of tibetan mountain loess six long sections were sampled and analysed for their geochemical and sedimentological characteristics showing that both sand and loess deposits have a local source a special focus was placed on the manganese concentration and the related environmental implications in several sections an increase in mn concentration from 318 44 to 878 294 ppm was found independent of concentrations in fe and organic compounds since the increase in mn is caused by solid mn3 and mn4 alone it is interpreted as increased dust input the synchronicity with climatic variations on the northeastern tibetan plateau confirms the climatic interpretation of the variations in mn sand and dust transport both took place around 11 ka followed by a period of fixation or even erosion of sediments although increased sand transport in the catchment already started around 3 ka the increased dust input did not take place before 0 7 ka therefore the mn concentrations are interpreted as an indication of increased dust transport during the very late holocene related to colder and drier circumstances during that time the use of manganese as a proxy for dust is a valuable addition to the toolbox of paleoclimate reconstruction since it is a direct proxy of dust in deposits however further validation and testing should be performed before general acceptation of mn as a paleoclimate proxy in terrestrial sediments

paleosalinity from trace metals in fossil ostracodes compared with observational records at devils lake north dakota usa abstract the chemistry of closed basin lakes responds directly to the hydrologic budget through evaporative concentration of dissolved salts and the sediments of these basins contain several excellent fossil and geochemical proxies for past changes in water chemistry and salinity the trace metal content of ostracode shells among the most promising of these paleosalinity methods is further explored in this study of mg and sr partitioning in candona rawsoni a widespread ostracode of the north american great plains the molar distribution coefficients kd mg and kd sr for this species k d mg ca caco 3 0 004 mg 2 ca 2 h 2 o 9 68 10 5 t c k d sr sr ca caco 3 sr 2 ca 2 h 2 oz 0 406 are determined from laboratory experiments in which c rawsoni are cultured under controlled temperatures and salinities our formulation of kd mg contains a correction term for excess mg that is incorporated into the shell during early calcification the accuracy of the distribution coefficients is tested against field collections of live ostracodes from a suite of 12 dakota lakes the kd inferred values for mg2 ca2 h2o and sr2 ca2 h2o are in close accord with the same ratios measured in the lakes a comparison of ostracode reconstructed and historically measured salinities for devils lake north dakota shows good agreement within the salinity range preferred by c rawsoni 1 10 0 although salinity excursions beyond this optimum are poorly represented in the sedimentary record in most lakes salinity is more readily inferred from mg ca h2o than sr ca h2o because sr solubility is a complex function of several carbonate phases as shown for devils lake sr ca h2o may not vary systematically with the salinity of some brines

global marine gravity field from the ers 1 and geosat geodetic mission altimetry satellite altimetry from the geosat and the ers i geodetic missions provide altimeter data with very dense spatial coverage therefore the gravity field may be recovered in great detail as neighboring ground tracks are very closely distributed cross track variations in the sea surface heights are extremely sensitive to sea surface variability to avoid errors in the gravity field caused by such effects sea surface variability needs to be carefully eliminated from the observations initially a careful removal of gross errors and outliers was performed and the tracks were fitted individually to a geoid model and crossover adjusted using bias and tilt subsequently sea surface heights were gridded using local collocation in which residual ocean variability was considered the conversion of the heights into gravity anomalies was carried out using the fast fourier transform fft in this process filtering was done in the spectral domain to avoid the so called orange skin characteristics comparison with marine gravity was finally carried out in three different regions of the earth to evaluate the accuracy of the global marine gravity field from ers 1 and geosat

total organic carbon isotopes a novel proxy of lake level from lake qinghai in the qinghai tibet plateau china abstract the isotopic compositions of total organic carbon toc in lakes have been widely used to interpret paleoclimatic changes and the depositional environments of lake sediments however the main factors that affect the carbon isotopes of toc source of organic material water condition and others may vary in different lake sediment records which have limited the applicability of organic carbon isotopes in explaining biogeochemical and environmental changes in lakes in this study the organic carbon isotopic compositions of aquatic plants and surface sediments from lake qinghai and the living terrestrial plants and surface soils around the lake were systematically investigated to identify the sources of toc in the sediments and the significance of the organic carbon isotopes of sedimentary toc we found that the aquatic plants in the deep water areas 10 m were primarily dominated by cladophora but submerged plants potamogeton and ruppia l are the dominant species in shallow water 13 c org values 33 6 to 28 6 that are caused by c 3 like photosynthesis but the submerged plants have enriched 13 c org values 17 8 to 15 4 that are caused by c 4 like photosynthesis in addition the 13 c org values of cladophora become more negative with increasing water depth because of the slow photosynthetic rate caused by the weak light intensity at depth the isotopic data indicate that the carbon isotopes of organic material in the surface sediments are primarily controlled by the types of aquatic plant and that the 13 c org values of toc can be used to indicate the variation of the water depth lake level the organic carbon isotopic data from the 1f core showed that the water was shallow

trace element partitioning in pantellerites and trachytes abstract in order to investigate the effect of increasing melt peralkalinity on partitioning partition coefficients have been determined using neutron activation analyses of coexisting phenocrysts and glass of five samples from pantelleria spanning the range trachyte to pantellerite alkali feldspar partition coefficients for fe rb ba sr and eu vary with melt peralkalinity due to changes in melt polymerization and to the systematic increase in xor and decrease in xan of the feldspar in going from trachyte to pantellerite fe partition coefficients increase from 0 04 to 0 10 presumably because fe 3 increasingly substitutes in the feldspar tetrahedral site as melt activity of al declines and fe concentrations increase partition coefficients for trivalent light rees decrease and the partitioning pattern becomes flatter the most evolved samples having some of the lowest published values for feldspar the hundredfold decline in eu partition coefficients 2 5 to 0 024 and the decrease in the size of the positive partitioning anomaly are attributed to increasing eu3 eu2 in the melt as it becomes more peralkaline as well as to concomitant decrease in the ca content of feldspar as a result the behavior of eu during fractional crystallization of peralkaline suites is fundamentally different from that in metaluminous suites absolute abundances rise and the size of the negative eu anomaly changes little with fractionation beyond pantelleritic trachyte barium and strontium do not decline to extremely low concentrations in pantellerites as they do in highly evolved metaluminous rhyolites because the feldspar partition coefficients drop precipitously with peralkalinity similarly rb contents do not get large because the partition coefficient increases slightly 0 11 to 0 25 with peralkalinity and is sufficient to make rb only weakly incompatible in the feldspar dominated assemblage partition coefficients calculated for sr and ba from natural phenocryst matrix pairs can be gross over estimates in these feldspar rich felsic rocks if phenocrysts are zoned this effect is severe for assemblages with bulk distribution coefficients d greater than 4 even at very small crystal contents and for 4 d 2 it is significant if crystal contents exceed about 25 some of the very high values and much of the variability reported in the literature for ba and sr feldspar partition coefficients may be a result of this effect in contrast to feldspar partition coefficients for apatite and mafic phases change little with peralkalinity partition coefficients for rees and the compatible elements sc co and cr are all less than half those in fe rich clinopyroxene and olivine of similar composition in high silica rhyolite although absolute levels of partition coefficients are a function of melt polymerization the shapes of the ree partitioning patterns appear to be related to the composition of the clinopyroxene scandium is most strongly concentrated in clinopyroxene partition coefficient 27 60 having larger values in more fe rich compositions apatite shows a wide range in composition within the suite the concentrations of si fe rees and y increasing and mg ca and p decreasing in more evolved samples these trends however parallel those in coexisting glasses so that partition coefficients are essentially constant in peralkaline suites cs is the most incompatible of commonly analyzed elements but its great mobility during alteration and weathering limits its use as a differentiation index next in order of incompatibility are th u hf zr and ta which have small but finite values of d due to the partitioning of th and u into apatite 2 the accommodation of zr and hf by clinopyroxene 0 4 and titanomagnetite 0 2 and relatively high concentrations of ta in cossyrite and fe ti oxides the next most incompatible are the lightest and the heaviest rees and finally the middle trivalent rees and rb plots of pairs of relatively incompatible elements form straight line trends over large compositional ranges in peralkaline suites because the replacement of olivine titanomagnetite by cossyrite as the melt becomes more peralkaline causes little change in d the ree patterns of titanomagnetite and cossyrite are both approximately flat at values less than 0 1 and the relatively high titanomagnetite partition coefficients for ta 2 zr and hf when combined with the very low partition coefficients for these elements for olivine approximate the moderate partition coefficients for cossyrite

validity of off the shelf handheld portable xrf for sourcing near eastern obsidian chip debris handheld portable xrf hhpxrf has received considerable recent attention in archaeology especially for obsidian sourcing published studies largely suggest a high potential for success hhpxrf though has been met with debate and scepticism concerns fall into three categories 1 low accuracy and precision 2 data correction schemes and calibration and 3 ignorance of fundamental xrf issues such as specimen size limits and morphology effects the result is that archaeological interpretations in hhpxrf based studies are cast into doubt should interpretations be believed if authors did not follow the perceived best practices to address such questions the validity of hhpxrf for near eastern obsidian sourcing was tested under deliberately sub optimal conditions irregular obsidian debitage near the minimum size limits was sourced with a success rate of 94 based on a rank matches to 100 based on a and b rank matches even under conditions chosen to mimic off the shelf operation

initial source evaluation of archaeological obsidian from the kuril islands of the russian far east using portable xrf obsidian artifacts recently have been recovered from 18 archaeological sites on eight islands across the kuril island archipelago in the north pacific ocean suggesting a wide ranging distribution of obsidian throughout the island chain over the last 2 500 years although there are no geologic sources of obsidian in the kurils that are known to have been used prehistorically sources exist in hokkaido japan and kamchatka russia the southern and northern geographic regions respectively from which obsidian may have entered the kuril islands this paper reports on the initial sourcing attempt of kuril islands obsidian through the analysis of 131 obsidian artifacts data from this research were generated through the application of portable xrf technology and are used to address research questions concerning prehis toric mobility exchange and social networking in the kuril islands

on the provenance of prehistoric obsidian artifacts in south korea abstract using a series of geochemical data from obsidian samples taken from unmodified rocks and prehistoric sites we investigated the provenance of some obsidian artifacts found in south korea by using la icp ms and shrimp methods we analyzed rare earth elements rees and lead pb isotopic ratios of obsidian samples from the north korean side of the baekdusan mountain nk and artifacts from a neolithic site in gadeokdo southeast coast of south korea bg published accounts on the elemental correlation of previously analyzed samples were re examined in consideration of their geological compatibility it appears that the prehistoric artifacts from the middle to northern part of south korea have a genetic relationship with obsidians from the baekdusan area whereas those of the southern part are related to kyushu japan ree patterns of the bg and the nk samples demonstrate a prominent contrast between them suggesting their different provenances presumably the bg obsidians are related to the volcanic rocks of kyushu given that pb isotopic ratios are indicative of the relative contribution of crust versus mantle component to the volcanic magma they indicate the addition of a crustal component to the volcanic magma for the baekdusan volcanic rocks and the nk obsidians the kyushu volcanics and the bg obsidians have a relative affinity to the mantle component the geochemical approach adopted in the current research may be regarded as an accurate and effective means to discriminate and isolate obsidian sources helpful for provenance and other archaeological study of obsidian artifacts

petrography geochemistry and hf nd isotope evolution of drill core samples and target rocks from the el gygytgyn impact crater ne chukotka arctic russia el gygytgyn in northeast chukotka russia is a 3 6 ma 18 km diameter impact structure the impact crater was recently drilled in the framework of a project sponsored by the international continental scientific drilling program icdp target rocks at the el gygytgyn area are dominated by the felsic members of the late cretaceous okhotsk chukotka volcanic belt ocvb such a target lithology is unique among terrestrial impact craters thereby providing the opportunity to study shock metamorphism in siliceous volcanic rocks here we present a petrographic geochemical and isotopic study of the section of the drill core underneath the lacustrine sediments extending from 316 m to 517 m below the lake bottom blb the drill core stratigraphy includes 80 m of suevite and a cross section through a volcanic suite which consists of 1 a middle section 390 423 mblb with dominant felsic tuffs and a few mafic members and 2 a welded rhyolitic dacitic ignimbrite 423 517 mblb the melt fragments embedded in the suevite are interpreted as being impact related by comparison with impact glasses from the crater and in opposition to the target rock which does not include similar melts a suevitic dyke crosscuts the lower section of the core at the depth 471 40 mblb evidence for shock metamorphism is concentrated in the upper 10 m of the drill core and almost limited to the suevitic breccia the geochemical and isotope nd and hf composition of samples from the target and the drill core reveals relationships to the berlozhya magmatic assemblage bma arguing for similar source magmas the primitive upper mantle pum normalized trace element plot of rocks investigated here confirms a subduction related signature as previously proposed for rocks from both ocvb and bma

pxrf calibrations for volcanic rocks and the application of in field analysis to the geosciences advances in portable x ray fluorescence pxrf technologies have made such instruments an attractive choice for geologists who wish to collect chemical data in the field the acceptance of pxrf data for research purposes such as for example petrogenetic studies by the geologic community has been hampered by a perception of poor quality here we show that current generation pxrf instruments can yield high quality data when deployed either in the laboratory or as a base camp field instrument we have developed four calibrations for major minor and trace elements in geological materials using minimal sample preparation one for the broad range of geologic compositions 0 100 sio2 using rock powders and three with an emphasis on volcanic rock samples rock billets ranging from primitive basalt to rhyolite basalt rock powder and rhyolitic pumice powder the calibrations use influence coefficients to correct for absorbance and secondary enhancement of one element by x rays of other elements present in the sample nugget effects can have a significant influence over the determination of the concentration of elements such as zr if proper care in sample homogenization is not taken we evaluate data quality for each element in each calibration and find that for several elements ti mn fe ca k p cr ni zn rb sr y zr nb precision and accuracy approach those obtainable from full size wavelength dispersive xrf analysis maximization of data quality is achieved by matching of calibration material types and unknowns

among polynesia s first pots x ray fluorescence spectroscopy and petrographic thin section microscopy are applied to a sample of anomalous appearing lapita pottery sherds from nukuleka the earliest archaeological site in polynesia both analyses indicate non local origins for the ceramic vessels suggesting they were brought on founding canoes mineral inclusions in ceramic tempers eliminate sources to the west of tonga in eastern melanesia rather the temper source is most probably a dacitic high island from a distant island arc of central melanesia polynesian origins and settlement are issues more complex than currently recognized by the orthodox progressive settlement model for lapita expansion across oceania

morphodynamics and lake level variations at paiku co southern tibetan plateau china abstract proxy records from lakes on the tibetan plateau are commonly used to infer monsoon related climatic changes during the late quaternary specific influences of catchment processes and their interaction with the lake basin are seldom utilized based on morphological field investigations supported by remote sensing analyses in combination with radiocarbon dated sediment data from lacustrine sequences along paleoshorelines and terraces we can demonstrate that close relationships exist between glacier dynamics fluvial alluvial fan terrace formation and lake level and lake area changes of paiku co southern tibet our results show that the formation of large scale fluvial alluvial fans f1 predates the maximum advance of the xixiabangma glaciers the latter formed a distinct terminal moraine complex north of the present glaciers during the local lgm llgm at 42 21 cal ky bp a younger fan generation f2 developed from the llgm to the late holocene which was accompanied by lake level fluctuations with a generally decreasing trend the highest morphologically traceable lake level at 4665 m asl existed prior to 25 cal ky bp and induced a potential overflow to the neighboring langqiang co and pengqu river a high level also existed during the llgm followed by a minor decline until ca 15 cal ky bp owing to reduced meltwater discharge under cold and dry climatic conditions a return to the previous level during the late glacial early holocene period between 11 9 and 9 5 cal ky bp is likely caused by climate warming increased meltwater discharge and enhanced indian summer monsoon ism moisture supply afterwards paiku co shrank gradually toward its present level while the youngest fan f3 generation evolved as individual small sized bodies under ephemeral discharge conditions from the mid holocene to the present the formation of four terrace levels t4 1 is likely the result of sequential incision into the fan generations with a mean erosion rate of 50 cm ky caused by lake level lowering tectonic impact cannot be completely ruled out since 1976 the glaciers lost ca 15 in area accompanied by lake area loss of 3 7 between 1972 and june 2014 seasonal lake level variations of about 1 2 m in height occur in response to summer monsoon rainfall our data show a close interaction between glacial dynamics fluvial processes terrace formation and water budget changes throughout the last 25 cal ky bp in response to the well known insolation driven ism effective moisture supply during the late glacial and holocene period temperature driven meltwater dynamics were the controlling factors for variations in water balance of paiku co

an end member algorithm for deciphering modern detrital processes from lake sediments of lake donggi cona ne tibetan plateau china abstract deciphering significant sedimentological processes from a set of sediment samples is an important step in reconstructing environmental changes one approach going beyond classical methods is the unmixing of grain size distributions this paper presents a flexible end member modelling algorithm that is based on eigenspace analysis and considers inherent uncertainties it has been applied to the detrital grain size components of lacustrine surface sediment samples of lake donggi cona qinghai province china it allows up to five grain size end members to be characterised and quantified in an optimal model an end member with a major mode in the clay domain accounts for 34 of variance within the grain size data set it may represent sedimentation of suspension load from linear and laminar runoff during heavy precipitation events in summer three end members in the fine sand to medium silt domains make up 60 of lacustrine sedimentation they may represent local to remote aeolian processes that peak in wintertime a multimodal end member explaining the remaining 6 of variance may represent further fluvial and littoral dynamics or random fluctuations and measurement errors several model runs of different scaling and numbers of end members provided a suitable way to determine uncertainties inherent to the model a comparison of 12 different model runs and their respective uncertainties yielded a distinct model of robust end members the clay and medium silt end members are robust features of detrital sedimentation within lake donggi cona they alone explain 54 4 of total variance in the data however no spatial pattern or relation to water depth is found for any of the grain size end members thus when past detrital sedimentation at lake donggi cona is reconstructed a special focus should be on the robust features attributed to aeolian and suspension related sedimentation processes as well as on effective sediment mixing processes impeding a distinct correlation between grain size and spatial attributes further applications of the end member modelling algorithm to other depositional environments are encouraged to demonstrate its universal applicability