bog iron ore as a resource for prehistoric iron production in central europe a case study of the widawa catchment area in eastern silesia poland abstract spreading from the near east in the declining bronze age from the 2nd millennium bce onwards the technique of iron smelting reached eastern silesia poland in approximately the 2nd century bce pre roman iron age at this time the region of the widawa catchment area was inhabited by the przeworsk culture while the older moraine landscape of the study area lacks ores from geological rock formations bog iron ores were relatively widespread and due to their comparatively easy accessibility were commonly exploited for early iron production this paper investigates the mineralogical and elemental composition of local bog iron ore deposits and iron slag finds as a by product of the smelting process also taking into account the state of the art in research regarding the formation distribution and utilization of bog iron ores and considering data from comparative studies the crystalline mineralogical composition of local bog iron ores is dominated by quartz sio 2 and goethite feo oh in contrast to slag samples in which fayalite fe 2 sio 4 wustite feo and quartz with traces of goethite represent the main minerals ores and slags are both characterized by notable hematite fe 2 o 3 magnetite fe 3 o 4 and maghemite fe 2 o 3 contents analyzed bog iron ore samples show iron contents of up to 64 9 mass fe 2 o 3 equivalent to 45 4 mass fe whereas the iron contents of bloomery slags vary between 48 7 and 72 0 mass feo equivalent to 37 9 and 56 0 mass fe a principal component analysis of the element contents which were quantified by portable energy dispersive x ray fluorescence spectrometry indicates local variations in the elemental composition the results of this study show that bog iron ores are relatively widely distributed with spatially varying iron contents along the widawa floodplain but present day formation conditions such as changed groundwater levels are negatively affected by modern land use practices such as agriculture and melioration measures

lake level and climate changes between 42 000 and 18 000 c 14 yr bp in the tengger desert northwestern china multiple lines of stratigraphic geochemical and fossil data suggest that fresh mesohaline paleolakes were widespread in the tengger desert of northwestern china and underwent major fluctuations during the late pleistocene the paleolakes started to develop at ca 42 000 c 14 yr b p the lake levels were the highest between 35 000 and 22 000 c 14 yr b p during which megalake tengger dominated the landscape the climatic conditions at this time were unique for this area and have no modem analogue after an episode of decline between 22 000 and 20 000 c 14 yr b p and an episode of rebound between 20 000 and 18 600 c 14 yr b p the paleolakes started to desiccate and completely disappeared around 18 000 c 14 yr b p the environmental proxy data indicate that the megalake tengger formed under warm humid climates the reconstructed climatic variations appear to be correlative with the abrupt climatic events reconstructed for the north atlantic c 2002 university of washington

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

depleted mantle source for the ulungur river a type granites from north xinjiang china geochemistry and nd sr isotopic evidence and implications for phanerozoic crustal growth abstract the ulungur river granites from north xinjiang china display two petrological trends 1 a peralkaline trend composed of alkali amphibole and alkali pyroxene bearing granites and dykes and 2 an aluminous trend represented by alkali granites monzogranites and aluminous granite dykes within the peralkaline granites rb sr whole rock isochron dating yielded an age of 300 ma for the emplacement of the peralkaline granites and 270 ma for the aluminous granites the ulungur river granites share all the geochemical features common to a type granites of the world the ulungur river granites are post orogenic and emplaced in a post collisional extensional environment the peralkaline and aluminous rocks have indistinguishable nd isotopic compositions they have unusually positive and relatively uniform nd t values ranging from 5 1 to 6 7 for the peralkaline rocks at 300 ma and from 5 5 to 5 9 for the aluminous rocks at 270 ma the initial 87sr 86sr ratios cannot be determined precisely by the whole rock isochron technique mainly because most samples are highly radiogenic and have high rb sr ratios in addition the large variation in sr isotopic compositions can partly be explained by crustal contamination during magma differentiation the nd isotopic data clearly indicate that both the peralkaline and aluminous rocks were derived from a long lived depleted mantle reservoir the formation of the ulungur river a type granites is hypothesized as follows 1 a depleted mantle was first metasomatised then subjected to partial melting leading to the generation of basic magmas now represented by the kalatongke mafic ultramafic complex in the ulungur river area 2 the basic magmas have undergone high degrees of fractional crystallisation with separation of biotite hornblende plagioclase potassium feldspar and other accessory phases such as apatite and ilmenite with the residual magmas forming the peralkaline granites during the magmatic differentiation the liquids were probably contaminated by crustal materials as evidenced by nb depletion and nd sr isotopic systematics on the other hand the formation of aluminous granites involved a replenishment of new mantle derived magmas into the differentiating magma chamber and followed by fractional crystallisation with retention of hydrous phases hornblende and biotite the petrological evolution of the ulungur river granites is thus from peralkaline to calc alkaline and not from calc alkaline to peralkaline as more often observed elsewhere the ulungur river granites in common with the voluminous granitoids occurring in the central asian orogenic belt represent a significant juvenile addition of the continental crust in the phanerozoic

palaeo moisture evolution in monsoonal central asia during the last 50 000 years abstract the late quaternary climate history of monsoonal central asia was inferred from 75 palaeoclimatic records which provide information about moisture conditions in the last 50 ka or part of this period wet conditions occurred during middle and late marine isotope stage 3 while the last glacial maximum lgm was characterized by dry climate conditions in the region a stepwise climate amelioration is suggested by the climate records following the lgm several climate signals of this period which were reported from high latitude ice core records are preserved in archives from monsoonal central asia as well during the early holocene high effective moisture was inferred from most records from the area dominated by the indian monsoon e g the tibetan plateau suggesting that holocene optimal climate conditions occurred there during this period in contrast areas which are dominated by the south east asian monsoon se monsoon and the westerlies in north western and north central china mongolia do not uniformly show an early holocene climate optimum for this area optimal conditions prevailed during the mid holocene these apparent contradictions can possibly be explained by the regional uplift and descent of air masses in the holocene during the early holocene strengthened insolation possibly caused an enhanced low level convergence over the tibetan plateau which led to the intensification of the summer monsoon the strong air uplift caused intensified precipitation and air divergence in the upper troposphere over the tibetan plateau the areas adjacent to the north therefore experienced an intensified descent of air masses and consequently increased aridity the majority of the palaeoclimatic records suggest reduced effective moisture since the late holocene in the region

electromagnetic and geoelectric investigation of the gurinai structure inner mongolia nw china abstract in three field campaigns between the years 2000 and 2004 geophysical measurements were conducted in the ejina basin nw china research work in the year 2004 which is described in this paper was concentrated on the gurinai structure 101 25 e 41 n situated in the southeastern part of the ejina basin in transition to the dune fields of the badain jaran shamo on satellite images the gurinai structure can be identified by two almost 100 km long subparallel n s striking lineaments which may indicate tectonic deformations of late quaternary sediments to get a coherent picture of the structure a geophysical survey employing three electromagnetic methods magnetotellurics mt transient electromagnetics tem and geoelectrics dc has been conducted to map the subsurface resistivity at different depth scales the geophysical data interpretation for shallow and intermediate depth down to a few hundred meters links the subsurface distribution of electric resistivity to geomorphological units known from field work in reference with satellite images the westerly lineament of the gurinai structure coincides with a subvertical change in electric resistivity together with geomorphological indications from fieldwork and the analysis of elevation data srtm a tectonic deformation of unconsolidated sediments along a fault with an extensional component is interpreted in the central and eastern part of the gurinai structure a shallow resistive subsurface layer can be traced into the first dunes of the badain jaran shamo this resistive subsurface layer is linked to the presence of fresh water indicating infiltration from the dune field also in the eastern part of the gurinai structure a resistive approximately ene striking feature can be seen at intermediate depth which is interpreted as a crystalline basement ridge towards the southern margin of the gurinai structure a trough shaped unit with low resistivities and a thickness of about 1 km is identified and can be explained by a sediment package saturated with fluids of high salinity or substantial amounts of clay the strike direction of the structure can be connected to the regional pattern of tectonic faults and seismicity the interpretation of electromagnetic data at various depth scales contributes to the general understanding of the ejina basin s buildup and tectonic setting in the vicinity of the gurinai structure

formation and palaeozoic evolution of the gorny altai altai mongolia suture zone south siberia zircon u pb constraints on the igneous record abstract the altai sayan fold belt epitomises how phanerozoic island arc continental crust contributed to the growth of the palaeo eurasian continent its formation is dominated by the closure of the palaeo asian ocean pao when island arc systems and gondwana derived terranes accreted to the siberian margin relics of the pao related tectonic units and associated granitoids occur along the ophiolitic charysh terekta ulagan sayan suture ctuss between gorny altai and altai mongolia zircon la icp ms u pb dating of this igneous record constrains the multi stage geodynamic pao evolution primitive kuznetsk altai island arc crust formed at the siberian margin during the ediacaran early cambrian 525 555 ma this island arc matured during the middle late cambrian 510 ma and was consumed by pao subduction in the late cambrian early ordovician 480 490 ma forming the siberian early caledonian accretion collision belt south of the ctuss granitic magmatism occurred within gondwana derived altai mongolia during the middle late ordovician 450 470 ma palaeo kazakhstan assembly and during a silurian early devonian 400 425 ma andean type collision middle late devonian 360 395 ma granitoids were emplaced as a result of the collision of altai mongolia with siberia during final pangaea amalgamation the suture was strike slip reactivated associated magmatism 295 ma the youngest 220 255 ma sampled granitoids originated in an intra plate setting

hydrogeology of the oak ridges moraine aquifer system implications for protection and management from the duffins creek watershed the oak ridges moraine aquifer feeds the headwaters of major rivers in the greater toronto area and is an important source of domestic water supply recognizing the rapid rate of urban growth in the region there is a concern that changing land use along the moraine must be strictly controlled if groundwater is to be adequately protected to date efforts to incorporate groundwater protection into the land use planning process have been hampered by an inadequate quantitative hydrogeological understanding of the aquifer system focusing on the duffins creek watershed comprehensive hydrogeological studies including a numerical flow model now provide a quantitative insight into the hydrogeologic function of the moraine these studies demonstrate that 60 of the entire basin groundwater discharge to streams occurs along the south flank of the moraine and 60 of this headwater discharge occurs below the 275 m above sea level contour one of the commonly accepted planning boundaries of the moraine the remaining discharge is contributed by aquifers within and underlying deposits that extend to the south of the moraine while 75 80 of the watershed discharge to streams is received from the uppermost aquifer 20 25 is contributed by deeper aquifers underlying the extensive northern newmarket till aquitard this work shows that the moraine sediments represent just one component of a regional flow system that extends beyond the morphological boundary of the moraine this has important implications for groundwater protection as it demonstrates the need for management strategies that incorporate the regional groundwater flow system and not the moraine in isolation

holocene vegetation and climate of the alashan plateau nw china reconstructed from pollen data a set of 55 recent pollen spectra from the alashan plateau and the qilian mountains qilianshan northwestern china has been analyzed the established relationships between the pollen spectra and modern vegetation and precipitation patterns of the studied area have been applied to 65 fossil pollen spectra from a 825 cm long sediment record collected in the topographic depression formerly occupied by eastern juyan palaeolake 41 89 n 101 85 e 892 m a s l several qualitative approaches e g indicator plant species artemisia chenopodiaceae and ephedra fragilis type s l ephedra distachya type pollen ratios and quantitative methods of vegetation and climate reconstruction have been tested with the surface pollen and then applied to the eastern juyan pollen record fossil pollen data reveal pronounced environmental changes in the studied area of the alashan plateau between ca 10 700 and 1700 cal yr b p desert taxa as chenopodiaceae nitraria calligonum reaumuria were abundant in the vegetation cover around the study site through the whole record pollen spectra dated to ca 10 700 5400 cal yr b p are characterised by highest values of chenopodiaceae e fragilis type and other desert indicating taxa suggesting rather dry climate most favourable conditions are reconstructed between 5400 and 3900 cal year b p on the basis of relative increase in abundance of artemisia pollen a return to dry conditions occurred at about 3900 cal yr b p the lake finally desiccated after 1700 cal yr b p reconstructed dry climate oscillations between 5900 and 5400 and 3100 cal yr b p correlate well with similar events found in the published records from northern and western china and central mongolia however eastern juyan record does not show the early holocene humidity maximum as suggested by the sedimentary data from monsoon influenced areas of china

late quaternary glacial interglacial cyclicity models of the red sea the benthic foraminiferal faunas from samples of two piston cores retrieved along a north south transect in the red sea were studied the northern core was collected during meteor cruise m 31 2 while the southern one was collected during the sonne cruise 121 benthic foraminiferal faunas from both sites exhibit large variability with respect to density diversity species composition and assemblages combined with stable oxygen and carbon isotope records of planktic and benthic foraminifera one hundered thirty benthic foraminiferal species were identified in the investigated cores the faunal data set of the northern core was reduced to five assemblages factors while the southern one was reduced to four assemblages all assemblages were ranked according to their ecological significance besides relative abundance of major benthic foraminiferal suborders textulariina agglutinating foraminifera miliolina and rotaliina in addition to infaunal epifaunal relative abundance were used as paleoenvironmental proxies allowing the reconstruction of past changes in deep water salinity ventilation and organic carbon fluxes at the sea floor four distinct glacial interglacial cycle during the past 380 kyr have been recognized in the red sea the identified four cycles reveal deviation in deep sea ecosystem between the northern and southern red sea in the northern red sea salinity fluctuations productivity and deep water ventilation and formation had the major impact on benthic foraminiferal pattern corresponding to glacial interglacial cycles and glacio eustatic sea level changes coupled with the impact of mediterranean climate regime on the otherhand in the southern red sea region the oscillation trend of benthic foraminiferal pattern within the glacials and interglacials stages indicates a high frequency environmental alternation this alternation is consistent with the extent of ne monsoonal wind that controls the intensity and extension of the productivity which in turn determine organic matter fluxes and oxygen level at the sea floor

synchronism of holocene east asian monsoon variations and north atlantic drift ice tracers eighteen radiocarbon dated eolian and paleosol profiles within a 1500 km long belt along the arid to semi arid transition zone of north central china record variations in the extent and strength of the east asian summer monsoon during the holocene dated paleosols and peat layers represent intervals when the zone was dominated by a mild moist summer monsoon climate that favored pedogenesis and peat accumulation brief intervals of enhanced eolian activity that resulted in the deposition of loess and eolian sand were times when strengthened winter monsoon conditions produced a colder drier climate the monsoon variations correlate closely with variations in north atlantic drift ice tracers that represent episodic advection of drift ice and cold polar surface water southward and eastward into warmer subpolar water the correspondence of these records over the full span of holocene time implies a close relationship between north atlantic climate and the monsoon climate of central china

a general cooling trend on the central tibetan plateau throughout the holocene recorded by the lake zigetang pollen spectra abstract a 741 cm long laminated sediment core covering the last 10 800 years was collected from lake zigetang central tibetan plateau 90 9 e 32 0 n 4560 m a s l and analysed palynologically at 69 horizons biome reconstruction suggests a dominance of temperate steppe vegetation mainly artemisia and poaceae on the central tibetan plateau during the first half of the holocene 10 8 4 4 cal ka bp while alpine steppes with desert elements mainly cyperaceae poaceae chenopodiaceae and characteristic high alpine herb families tend to dominate the second half 4 4 0 cal ka bp the artemisia cyperaceae ratio a semi quantitative measure for summer temperature indicates a general cooling trend throughout the holocene dense temperate steppe vegetation and maximum desert plant withdrawal however indicate that a suitable balance of wet and warm conditions for optimum vegetation growth likely occurred during the middle holocene 7 3 4 4 cal ka bp severe early holocene cold events have been reconstructed for 8 7 8 3 and 7 4 cal ka bp

mafic magmatic enclaves and mafic rocks associated with some granitoids of the central sierra nevada batholith california nature origin and relations with the hosts abstract the calc alkaline granitoids of the central sierra nevada batholith are associated with abundant mafic rocks these include both country rock xenoliths and mafic magmatic enclaves mme that commonly have fine grained and less commonly cumulate textures scarce composite enclaves consist of either xenoliths enclosed in mme or of mme enclosed in other mme with different grain size and texture enclaves are often enclosed in mafic aggregates and form meter size polygenic swarms mostly in the margins of normally zoned plutons enclaves may locally divert schlieren layering mafic dikes which also occur in swarms are undisturbed composite or largely hybridized in central sierra nevada with the exception of xenoliths that completely differ from the other rocks host granitoids mafic aggregates mme and some composite dikes exhibit a bulk compositional diversity and at the same time important mineralogical and geochemical including isotopic similarities mme and host granitoids display distinct major and trace element compositions however strong correlations between mme host granitoid pairs indicate interactions and parallel evolution of mme and enclosing granitoid in each pluton identical mafic mineral compositions and isotopic features are the result of these interactions and parallel evolution mafic dikes have broadly the same major and trace element compositions as the mme although variations are large between the different dikes that are at distinctly different stages of hybridization and digestion by the host granitoids the composition of the granitoids and various mafic rocks reflects three distinct stages of hybridization that occurred respectively at depth during ascent and emplacement and after emplacement the occurrence and succession of hybridization processes were tightly controlled by the physical properties of the magmas the sequential thorough or partial mixing and mingling were commonly followed by differentiation and segregation processes unusual mme that contain abundant large crystals of hornblende resulted from disruption of early cumulates at depth whereas those richer in large crystals of biotite were formed by disruption of late mafic aggregates or schlieren layerings at the level of emplacement mme and host granitoids are considered cogenetic because both are hybrid rocks that were produced by the mixing of the same two components in different proportions the felsic component was produced by partial melting of preexisting crustal materials whereas the dominant mafic component was probably derived from the upper mantle however in the lack of a clear mantle signature the origin of the mafic component remains questionable

groundwater recharge history and hydrogeochemical evolution in the minqin basin north west china the minqin basin is a type area for examining stress on groundwater resources in the gobi desert and has been investigated here using a combination of isotopic noble gas and chemical indicators the basin is composed of clastic sediments of widely differing grain size and during the past half century over 10 000 boreholes have been drilled with a groundwater decline of around 1 m a 1 modern diffuse recharge is unlikely to exceed 3 mm a 1 as determined using unsaturated zone profiles and cl mass balance a small component of modern 50 a groundwater is identified in parts of the basin from 3h 3he data probably from irrigation returns a clear distinction is found between modern waters with median 18o values of 6 5 0 5 and most groundwaters in the basin with more depleted isotopic signatures radiocarbon values as pmc range from 0 6 to 85 modern but it is difficult to assign absolute ages to these although a value of 20 modern c probably represents the late pleistocene to holocene transition the 13c compositions remain near constant throughout the basin median value of 8 1 13c and indicate that carbonate reactions are unimportant and also that little reaction takes place there is a smooth decrease in 14c activity accompanied by a parallel increase in 4he accumulations from s n across the basin which define the occurrence of a regional flow system noble gas temperatures indicate recharge temperatures of about 5 6 c for late pleistocene samples which is some 2 3 c cooler than the modern mean annual air temperature and the recharge temperature obtained from several holocene samples groundwaters in the minqin basin have salinities generally below 1 g l and are aerobic containing low fe but elevated concentrations of u cr and se mean values of 27 5 5 8 and 5 3 g l 1 respectively nitrate is present at baseline concentrations of around 2 mg l 1 but there is little evidence of impact of high no3 from irrigation returns strontium isotope and major ion ratios suggest that silicate reactions predominate in the aquifer the results have important implications for groundwater management in the minqin and other water stressed basins in nw china a region so far destined for rapid development the large proportion of the water being used at present is in effect being mined and significant changes are urgently needed in water use strategy

environmental conditions in the donggi cona lake catchment ne tibetan plateau based on factor analysis of geochemical data abstract we present a methodological approach for the characterization of spatial variations of environmental and transport conditions based on geochemical data we analyzed the geochemical characteristics of terrestrial sediments on an alluvial fan and adjacent areas in the eastern part of the donggi cona catchment the geochemical characteristics of the sediment samples were measured using x ray fluorescence spectroscopy a factor model based on nine elements sr rb zn fe mn v ti ca and k gave the best results using factor analysis our results show that factor analysis of geochemical data can explain spatial variations in the catchment even within a relatively small area with more or less constant climatological conditions the four most important factors of our model explain 68 4 of the total variance within the dataset the four factors represent a carbonate weathering and two redox condition signals respectively the spatial distribution of factor loadings points to regions with specific environmental conditions these regions show a certain carbonate input or production factor 1 specific weathering rates factor 2 or specific redox conditions factors 3 and 4 the factor loadings of the first and second factor are used to reclassify the data into four groups being dune loess lake and fluvial gravel sediments this reclassification confirms or improves the prior field classification in 70 of all cases for 23 of the samples the model gave a different interpretation the factor loadings in these cases represent the origin of the material rather than its present sediment type thereby giving valuable information about sediment provenance since the third and fourth factor seem more dependent on location they do not differentiate between different sediment types multivariate statistics of the geochemistry of terrestrial sediments i allows the subdivision of samples into different sediment types ii indicates dominant regions for weathering carbonate production and manganese washout and iii gives suggestions about the provenance of the sediments this is the first detailed study of geochemical parameters on the tibetan plateau not focusing on lake cores resulting in a spatial characterization of the local geochemistry this gives insight in the sediment transport connections between the catchment and the lake illustrating the value of terrestrial sediments as additional indicator of environmental variations

the holocene salinity history of bosten lake xinjiang china inferred from ostracod species assemblages and shell chemistry possible palaeoclimatic implications abstract a sediment core from bosten lake the largest freshwater lake in the tianshan mountains and in the northwesternmost province of china provided a high resolution record of environmental change covering the last 8500 cal a bp higher salinity levels of bosten lake were reconstructed from assemblages the stable isotope composition and sr ca and mg ca ratios of ostracod shells between 7800 and 5600 cal a bp a period of low and moderate salinities between 5600 and 4900 cal a bp was followed by the re establishment of higher salinities between 4900 and 4300 cal a bp since then bosten lake has recorded fluctuating conditions with a number of multi centennial phases of low and moderate salinities although the salinity lake level relationship of bosten lake is not fully understood a higher salinity at the core site seems to correspond to periods of higher lake levels this contradictory interpretation is explained tentatively by the changing distance of the core site to the freshwater providing river mouth with changing lake levels and potentially resulting lateral shifts of the salinity distribution pattern within the lake assuming this explanation is correct the record from bosten lake reflects higher moisture availability and a strong climatic influence of the indian monsoon in the early mid holocene until about 4000 cal a bp and more unstable drier conditions susceptible to minor changes in the regional circulation patterns and temperature variations afterwards

correlation between indian ocean summer monsoon and north atlantic climate during the holocene there has been a number of investigations for the correlation between the asia monsoon and the north atlantic climate for the last glacial however little research has been done for the present interglacial the holocene here we present for the first time a high resolution composite proxy record for the indian ocean summer monsoon spanning around 12 000 years based on the 13c time series of both a single plant species carex mulieensis remains cellulose and the total plant assemblage cellulose in the hongyuan peat bog from the tibet plateau the records show that the strength of the indian ocean summer monsoon had abrupt variations during the last 12 000 years the weakest monsoon occurred in the younger dryas period following rapid strengthening from around 11 200 to 10 800 a bp the monsoon kept a generally strong level for around 5300 years from around 5500 a bp onwards the monsoon strength tended to gradual decrease in addition there are a series of abrupt variation events of the monsoon strength on centennial to millennial time scales which superimpose the general tendency of the monsoon variation in every case when the ice rafted debris events in the north atlantic occurred the summer monsoon strength decreased correspondingly these evidences show that teleconnection between the indian ocean summer monsoon and the north atlantic climate is present not only in the last glacial but also in the holocene which may be linked to abrupt reorganizations of the ocean thermohaline circulation leading to redistribution of energy changing temperature and moisture gradient over the southern subtropical indian ocean and eventually controlling the variability of the indian ocean summer monsoon

millennial scale holocene climate variability in the nw china drylands and links to the tropical pacific and the north atlantic abstract a loess paleosol sequence and a lake sediment record from the central hexi corridor in the drylands of nw china show patterns of persistent millennial to centennial scale climate variability during the holocene epoch which can be well correlated with abrupt climatic events reported from the north atlantic and the asian monsoon dominated regimes our results show that the drylands in nw china might have been regulated both by the westerlies and by the east asian summer monsoon easm in a roughly synchronous manner it seems that cold dry intervals in the central hexi corridor may generally correspond to cooling phases in high latitudes of the northern hemisphere and that cold warm wet intervals largely correlate with relatively warm phases in northern high latitudes a candidate mechanism involving nao ao and enso dynamics is tentatively proposed to account for this synchroneity climatic patterns may be spatially different in the nw china drylands in response to the changing predominant control of either the westerlies or the easm depending on the contrast of their relative strengths glacier meltwater discharges associated with alpine warming may be partly responsible at least for the two records discussed in this paper for such spatial heterogeneity of climatic changes during the holocene more work is needed to evaluate the individual roles and combined impacts of the easm the westerlies and alpine glacier meltwater regulation on the nw china dryland dynamics

isotope provinces mechanisms of generation and sources of the continental crust in the central asian mobile belt geological and isotopic evidence abstract the available geological geochronological and isotopic data on the felsic magmatic and related rocks from south siberia transbaikalia and mongolia are summarized to improve our understanding of the mechanisms and processes of the phanerozoic crustal growth in the central asian mobile belt camb the following isotope provinces have been recognised precambrian t dm 3 3 2 9 and 2 5 0 9 ga at the microcontinental blocks caledonian t dm 1 1 0 55 ga hercynian t dm 0 8 0 5 ma and indosinian t dm 0 3 ga that coincide with coeval tectonic zones and formed at 570 475 420 320 and 310 220 ma continental crust of the microcontinents is underlain by or intermixed with juvenile crust as evidenced by its isotopic heterogeneity the continental crust of the caledonian hercynian and indosinian provinces is isotopically homogeneous and was produced from respective juvenile sources with addition of old crustal material in the island arcs or active continental margin environments the crustal growth in the camb had episodic character and important crust forming events took place in the phanerozoic formation of the camb was connected with break up of the rodinia supercontinent in consequence of creation of the south pacific hot superplume intraplate magmatism preceding and accompanying permanently other magmatic activity in the camb was caused by influence of the long term south pacific plume or the asian plume damping since the devonian

late glacial and holocene environmental change reconstructed from floodplain and aeolian sediments near burdukovo lower selenga river valley lake baikal region siberia abstract floodplain and aeolian sediments near burdukovo reveal a detailed record of holocene environmental change in the lower selenga river valley lake baikal region siberia during the late pleistocene and early holocene fine grained alluvium accumulated on the floodplain followed by a period of increased landform stability and subsequent pedogenic formation this part of the stratigraphical sequence yielded rich assemblages of terrestrial molluscs which increase in species diversity from early pioneer communities with about ten taxa to levels containing over twice that number the land snail assemblages also record an episode of relatively drier local habitats prior to 9 2 ka bp with subsequent wetter conditions lasting until 8 0 ka bp this was followed by an abrupt and sustained change in floodplain deposition shifting from overbank alluvium to aeolian sedimentation within which a series of weakly developed soil horizons formed during the middle and late holocene periods the onset of aeolian processes and relatively drier conditions in the middle holocene at burdukovo coincides with major changes observed both in other regional palaeoenvironmental proxy records and in local archaeological sequences although it is still not clear how the two are linked

hf isotopes in zircon reveal contrasting sources and crystallization histories for alkaline to peralkaline granites of temora southeastern australia peralkaline granites exhibit the hallmark features of a type igneous rocks but strongly differentiated chemistry and intense hydrothermal alteration camouflage their ultimate origins we present the first in situ hf isotope data from zircons of peralkaline granites aimed at clarifying the protoliths of these plutons and their genetic relationship to associated metaluminous weakly peraluminous granites this study used rocks of the devonian narraburra complex in southeastern australia and found that correlations between hf isotopes and trace element ratios reveal fundamentally different origins for the nonperalkaline and peralkaline granites the latter have a depleted mantle like ancestry whereas a weakly peraluminous rock formed from melts of older arc crust that were modified by interaction with juvenile probably alkaline magmas juxtaposition of crust and mantle derived magmas reflects the high heat flow and lithosphere scale faults associated with continental extension and explains the diversity of a type granites

groundwater discharge to a gobi desert lake during mid and late holocene dry periods abstract high levels of lake eastern juyanze and a wetter climate in the gobi desert nw china were recorded between 5100 and 4100 cal year bp from ostracod distribution shell geochemistry sedimentology and palynological data after about 4100 cal year bp lake levels decreased and groundwater discharge became dominant source of water during short term regressive events at about 4000 3800 and 3500 cal year bp as suggested by a significant difference in modern river water and groundwater chemistry and the geochemical signal of fossil ostracod shells the overall trend towards lower lake levels culminated in repeated episodes of desiccation of lake eastern juyanze between 3200 and 2900 cal year bp individual regressive events as well as the rapid environmental fluctuations of lake eastern juyanze at about 3000 cal year bp were likely caused by mid to late holocene temperature fluctuations recorded by the dunde ice core yao t thompson l g 1992 trends and features of climatic changes in the past 5000 years recorded by the dunde ice core annals of glaciology 16 21 24 and shifts of the southeastern asian monsoon

holocene environmental changes in bangong co basin western tibet part 4 discussion and conclusions abstract a 12 4 m core taken in lake bangong provides a continuous holocene climatic record we summarize information on changes in stable isotope and radiocarbon balances in the lake hydrobiology and vegetal cover in the catchment deduced from detailed analytical results given in the three preceding papers the bangong record is then compared with the environmental history of the neighbouring lake sumxi also constructed from multidisciplinary analyses the two records show a major environmental change at 10 9 5 ka b p attributed to a rapid strengthening of the summer monsoonal circulation which led to wet warm conditions this event was followed by a long term trend toward aridity which culminated around 4 3 ka b p in western tibet maximum monsoon rainfall seems to have occurred from 9 5 to 8 7 ka b p and from 7 2 to 6 3 ka b p as two wet pulses separated by a reversal event centered on 8 0 7 7 ka b p our results broadly agree with the records from lake seling in central tibet and lake qinghai at the plateau s northeastern margin and with palaeoclimatic studies in western china which document conditions wetter and warmer than those of today during the early middle holocene the environmental fluctuations recorded in western tibet appear in phase with climatic changes recognized in tropical north africa suggesting that the 8 0 7 7 ka b p and the 4 0 3 0 ka b p dry events were caused by abrupt disequilibrium in the climatic system

regional unconformities and the sedimentary architecture of the oak ridges moraine area southern ontario seismic stratigraphy geometry and sediment facies within the oak ridges moraine orm area of ontario record major structural elements and surfaces of the quaternary sedimentary sequence the derived stratigraphic architecture can be used to identify the key elements of a regional erosional surface represented by an unconformity in the subsurface and associated overlying channel sediments the erosional surface unconformity forms a distinct time datum in the quaternary sequence which provides an important aid to lithostratigraphic correlation the architecture also gives improved understanding of the effects of erosion on the late glacial landscape the surfaces of erosional drumlins and intervening troughs and the beds and banks of meltwater channels in the orm area define the regional unconformity highlighted by seismic profiles linked to continuously cored boreholes these features are attributed to regional scale subglacial meltwater flow events the sculpted surfaces which are analogous to water eroded forms the presence of boulder lags and coarse grained deposits on the regional erosional surface and the channels with undulating profiles provide the vital supporting evidence for a meltwater interpretation the inter regional extent of the unconformity is inferred from the coherence of regional paleoflows and the extent of drumlinized uplands tunnel channels and scoured bedrock terrain across 75 of the landscape from the orm area east and south to the finger lakes new york the implied magnitude of erosion suggests a pressing need for directed sedimentological study in those ocean basins that were probable depositional sites for flood deposits

dry or humid mid holocene humidity changes in arid and semi arid china abstract spatial changes of effective moisture during the mid holocene have been reconstructed based on the compilation of recently published paleoclimate records including ice core lake level pollen assemblage and loess paleosol records both geological data and the spatial pattern indicate that it was dry in deserts during the mid holocene but the timing of the beginning and end of dry intervals differs from place to place deserts having higher aridity index values remain dry longer dry intervals during the mid holocene are more possibly asynchronous than synchronous in arid and semi arid china in the xinjiang region except in sites located in deserts the climate is generally wet during 7000 5000 a bp in the northern qinghai tibetan plateau effective moisture in most sites began to decrease after 5000 a bp the climate became dry after 4000 a bp except in the deserts in the loess plateau and the inner mongolia plateau

holocene climatic instability a prominent widespread event 8200 yr ago the most prominent holocene climatic event in greenland ice core proxies with approximately half the amplitude of the younger dryas occurred 8000 to 8400 yr ago this holocene event affected regions well beyond the north atlantic basin as shown by synchronous increases in windblown chemical indicators together with a significant decrease in methane widespread proxy records from the tropics to the north polar regions show a short lived cool dry or windy event of similar age the spatial pattern of terrestrial and marine changes is similar to that of the younger dryas event suggesting a role for north atlantic thermohaline circulation possible forcings identified thus far for this holocene event are small consistent with recent model results indicating high sensitivity and strong linkages in the climatic system

petrogenetic interpretation of granitoid rock series using multicationic parameters abstract granitoid rock compositions from a range of tectonic environments are plotted on a multicationic diagram devised by de la roche and his coworkers this shows that there is a systematic change through an orogenic cycle which leads progressively to the ultimate development of alkaline magmas possible source materials and mechanisms of magma generation are considered from analysis of mineral compositional vectors these suggest that most granitoid series result from a two stage process first fractional crystallisation of clinopyroxene olivine and calcic plagioclase from a basic source with tholeiitic affinities produces a magma of intermediate composition this magma then undergoes periodic mixing with a felsic magma followed by in situ fractionation to generate individual intrusions within granitoid series

late quaternary palaeolake levels in tengger desert nw china comprehensive field investigations and laboratory analyses show that palaeolakes including the megalake tengger and other semi connected and isolated water bodies during late pleistocene covered an area of more than 20 000 km 2 this is an area more than half the size of the tengger desert in nw china stratigraphic correlations and chronological evidence indicate that the palaeolakes started to develop around 42 000 14 c year bp uncalibrated all throughout the paper but their extent was limited until 37 000 14 c year bp based on the chronology of representative lacustrine deposits it can be deduced that the megalake tengger was established around 35 000 14 c year bp and maintained until 22 000 14 c year bp leading to the formation of the baijian hu terraces which are regarded as firm evidence of the existence of palaeolakes the formation mechanism is unclear and the climate situation at the time is still an open question the holocene palaeolakes started to develop around 12 000 14 c year bp the baijian hu terraces indicate that the high water levels in the area occurred around 8500 5400 5100 3500 and 1860 1370 14 c year bp the extent of the holocene palaeolakes primarily migratory lakes was smaller than that of the late pleistocene palaeolakes d 2004 elsevier b v all rights reserved

co2 h2o and orbitally driven climate variability over central asia through the holocene small variations in earth s orbit have a direct impact on global climate with the greatest changes occurring over large land masses such as asia orbitally driven climate signals are therefore likely to be identifiable in climate proxy records derived from sediment sections in the continental interior proxy records derived from temperature dependent variables are also likely to display a signal due to temporal variability of atmospheric co2 and related climatic parameters such as water vapour content to determine the magnitude of climate anomalies associated with shortwave and longwave radiative forcing over asia a suite of numerical atmospheric simulations is performed that spans most of the holocene from 10 000 to 2500 years bp at 500 year intervals over central asia the amplitude of the summer winter seasonal cycle is greater than today in all simulations but exhibits two distinct maxima at 9000 and 6000 bp simulated precipitation and snow accumulation over central asia are markedly higher during the early mid holocene and are oscillatory exhibiting peaks at 8000 7500 and 4500 bp the atlantic and subboreal times respectively co2 h2o forcing and orbital forcing combine to drive temperature oscillations over central asia which in turn regulate relative humidity and changes in surface hydrology correlation between simulated results and proxy records from across asia suggest that co2 h2o and orbital forcing are dominant factors driving fluctuations of large scale central asian climate through the holocene

questioning fe isotopes as a provenance tool insights from bog iron ores and alternative applications in archeometry abstract provenancing metal artifacts with scientific methods is an established tool in archeometry to identify the metal deposits which were exploited for the production of ancient metal objects it is thus an important method to reconstruct ancient exchange networks and the socio economic organization of past societies previously introduced isotope based approaches pb sr os and chemical analyses of slag inclusions have severe limitations concerning their application or the amount of sample required fe isotopes were previously suggested in a quite early stage of investigation as a potential provenance tracer and it was postulated that they would not fractionate during the smelting procedure however previously published analytical data from iron ores indicate a wide overlap between deposits further the earlier studies on fe isotopes did not included bog iron ores despite their high importance in ancient metallurgy as geochemical reactions during ore formation are complex and fractionation cannot be generally excluded the applicability of fe isotopes as an alternative provenance tracer still asks for further investigation this purely methodological study focuses on specimens from two sites of the formerly mined bog iron ore deposit eyller bruch germany which are analyzed together with products of a smelting experiment based on these ores the fe isotopic composition of the bog iron ore from the investigated region suggests an intra deposit zonation caused by environmental parameters and its overall variation is comparable with that of other deposits the bog iron ore isotope signature largely overlaps with the isotope range of mineralizations in other regions as a consequence of this and although the absence of fe isotope fractionation during the smelting procedure is confirmed the study demonstrates the lack of discriminatory power of fe isotopes for provenance studies potential applications for archeometry can rather be found in the environmental parameters especially organic matter which seems to have a strong influence on fe isotope compositions of bog iron ores zonations within deposits might be identified and could help to reconstruct the exploitation history of the deposit or to reconstruct past bog landscapes

asynchronous holocene climatic change across china a review of holocene climatic variations in different parts of china shows that they were asynchronous proxy data from ice cores pollen loess lacustrine sediments and changes of sea and lake levels demonstrate that many warm and cold oscillations have occurred in china during the holocene including a most important climatic event known as the holocene optimum a milder and wetter period and that the duration and amplitude of the optimum period as well as its start and end times differed in different parts of china uplift of the tibetan plateau over the past millions of years led to the development of the monsoon climate and to complex atmospheric circulation over continental china during the holocene as a result the holocene optimum began and terminated earlier in high altitude regions of western china than at lower elevations in eastern china and the amplitude of the variations was lower in the east this suggests that the western higher altitude areas were more sensitive to climatic change than were the eastern lower altitude areas holocene climatic records in the dunde and guliya ice cores do not correspond inverse 18o variations between the two cores indicate that the effects of climate and atmospheric processes on the stable isotopes at the two sites differed the correlation between the isotopic composition of carbonates in lake deposits in western china and climatic variations is similar to that in the ice cores the climatic resolution in ice cores and lake sediments is higher than that in other media the lack of precise correspondence of climatic records constructed on the basis of proxy data from different parts of china is a result of the different locations and elevations of the sampling sites the different resolutions of the source material and the varied climatic conditions within china further work is needed to confirm both the conclusions and the inferences presented here

paleozoic crustal growth and metallogeny of central asia evidence from magmatic hydrothermal ore systems of central kazakhstan abstract the ore deposit spectrum of central kazakhstan reflects a range of lithospheric magmatism controlled by the polycyclic geodynamic evolution of an active continental margin which develops from back arc oceanic settings volcanic hosted massive sulphide cu au ore deposits to subduction controlled calcalkaline magmatism copper porphyries with subsequent stages of crust differentiation of low degree partial melting and extended intramagmatic fractionation molybdenum porphyries on to continental rifting peralkaline ree zr nb rich systems mesothermal gold deposits mark transcrustal shear zone controlled fluid conduits formed during arc slicing and thermal relaxation in a post orogenic setting the ore deposits characterize successive and spatially overlapping stages of crustal growth and consolidation the general subduction setting of this range of ore deposits is reflected by calc alkaline trends in the associated subalkaline high k felsic rocks with a wide range in silica contents the predominant metal spectrum of au cu and mo indicates relatively oxidized magmatic hydrothermal systems in accordance with the metaluminous i type nature of their igneous host rocks i e oxidized igneous precursor material despite of presumably highly variable ratios of mantle crust components in individual magmatic systems gabbros to leucogranites most rocks have very similar positive initial e nd values of 0 to 5 5 and depleted mantle model ages in the range of 500 800 ma the ubiquitous relatively young mantle extraction age is likely to characterize the lower crust of central kazakhstan this basement is interpreted as back arc oceanic crust that formed behind oceanwards drifting continental margin slivers during the initial stages of the active continental margin evolution of the late precambrian angara baltica supercontinent the early back arc oceanic crust was transformed into the present lower crust during the paleozoic orogenic evolution in which the back arc crust was buried by magmatic arc and sedimentary material and recurrently affected by high grade metamorphism basaltic melt injection underplating and granitic melt extraction anorogenic rift related permian peralkaline riebeckite granites with ree zr nb mineralization have very high positive e nd of 5 to 8 which is probably inherited from young subcrustal lithosphere at the mantle crust boundary that was affected by partial remelting due to asthenospheric upwelling during rifting

accretionary growth and crust formation in the central asian orogenic belt and comparison with the arabian nubian shield kroner a windley b f badarch g tomurtogoo o hegner e jahn b m gruschka s khain e v demoux a and wingate m t d 2007 accretionary growth and crust formation in the central asian orogenic belt and comparison with the arabian nubian shield in hatcher r d jr carlson m p mcbride j h and martinez catalan j r eds 4 d framework of continental crust geological society of america memoir 200 p 181 209 doi 10 1130 2007 1200 11 for permission to copy contact editing geosociety org 2007 the geological society of america all rights reserved kroner kroener mail uni mainz de windley brian windley btinternet com tomurtogoo igmr magicnet mn hegner hegner lmu de jahn jahn earth sinica edu tw khain khain ginras ru demoux demoux uni mainz de wingate mwingate tsrc uwa edu au

late cenozoic transpression in southwestern mongolia and the gobi altai tien shan connection the gobi altai region of southwestern mongolia is a natural laboratory for studying processes of active transpressional intracontinental mountain building at different stages of development the region is structurally dominated by several major e w left lateral strike slip fault systems the north gobi altai fault system is a seismically active right stepping left lateral strike slip fault system that can be traced along the surface for over 350 km the eastern two thirds of the fault system ruptured during a major earthquake m 8 3 in 1957 whereas degraded fault scarps cutting alluvial deposits along the western third of the system indicate that this segment did not rupture during the 1957 event but has been active during the quaternary the highest mountains in the gobi altai are restraining bend uplifts along the length of the fault system detailed transects across two of the restraining bends indicate that they have asymmetric flower structure cross sectional geometries with thrust faults rooting into oblique slip and strike slip master faults continued ne directed convergence across the fault system coupled with left lateral strike slip displacements will lead to growth and coalescence of the restraining bends into a continuous sublinear range possibly obscuring the original strike slip fault system this may be a common mountain building process the largely unknown gobi tien shan fault system is a major left lateral strike slip fault system 1200 km long that links the southern ranges of the gobi altai with the barkol tagh and bogda shan of the easternmost tien shan in china active scarps cutting alluvial deposits are visible on satellite imagery along much of its central section indicating quaternary activity the total displacement is unknown but small parallel splays have apparent offsets of 20 km suggesting that the main fault zone has experienced significantly more displacement field investigations conducted at two locations in southwestern mongolia indicate that late cenozoic transpressional uplift is still active along the fault system the spatial relationship between topography and active faults in the barkol tagh and bogda shan strongly suggests that these ranges are large coalescing restraining bends that have accommodated the fault s left lateral motion by thrusting oblique slip displacement and uplift thus from a mongolian perspective the easternmost tien shan formed where it is because it lies at the western termination zone of the gobi tien shan fault system the gobi tien shan fault system is one of the longest fault systems in central asia and together with the north gobi altai and other smaller subparallel fault systems is accommodating the eastward translation of south mongolia relative to the hangay dome and siberia these displacements are interpreted to be due to eastward viscous flow of uppermost mantle material in the topographically low e w trending corridor between the northern edge of the tibetan plateau and the hangay dome presumably in response to the indo eurasian collision 2500 km to the south

hf isotopic compositions of the standard zircons and baddeleyites used in u pb geochronology abstract zircon and baddeleyite u pb geochronological dating is widely used in solid earth sciences and the advent of rapid in situ methods of analysis such sims and icp ms has re emphasized the importance of having uniform standards recently it has been shown that hf isotopic data can provide important information on these minerals since they contain high concentrations of hf but have low lu hf ratios which results in negligible age correction however the complex internal structures that result from multiple thermal events such as inherited cores and metamorphic overgrowths require that the hf isotopic data be measured with high spatial resolution however the isobaric interferences of 176 yb and 176 lu on 176 hf hamper the precise determination of the 176 hf 177 hf ratio during in situ laser ablation mc icpms analysis it is shown here that mass biases of yb yb and hf hf change with time during analyses and behave differently for solutions and solid material therefore it is suggested that the mean yb value of the individual spot be used to obtain the precise isotopic composition for in situ zircon and baddeleyite hf isotopic analyses for low yb hf 176 yb 177 hf yb value have little effect on the accuracy of the hf isotopic composition however the appropriate yb isotopic abundance is necessary for high yb hf 176 yb 177 hf 0 001 zircons and baddeleyites since the interference of 176 yb on 176 hf is significant using the mean yb value of the individual spot and newly published yb isotopic abundance data six standard zircons and two standard baddeleyites have been investigated using a neptune mc icpms with 193 nm laser for zircons the obtained 176 hf 177 hf ratios are 0 282307 31 2sd for 91500 0 282680 31 2sd for temora 0 281729 21 2sd for cz3 282177 17 2sd for cn92 1 0 282983 17 2sd for fm0411 and 281234 11 2sd for phalaborwa the baddeleyites from phalaborwa and sk10 2 have 176 hf 177 hf ratios of 0 281238 12 and 0 282738 13 2sd these results agree well with the values obtained by the solution method and indicate that these standards have different hf isotopic compositions in which the extremely low 176 lu 177 hf and 176 yb 177 hf values of cz3 zircon and phalaborwa baddeleyite make them excellent standards for machine calibration during in situ zircon hf isotopic measurement with the other standards being more suitable for the development of the correction method

hydrological changes and holocene climate variations in nw china inferred from lake sediments of juyanze palaeolake by factor analyses abstract the eastern juyanze palaeolake in hyperarid north western china 41 75 42 n 101 5 102 e provides evidence of a complex hydrological pattern during the holocene multivariate statistics based on lithological geochemical and mineral data from the reference site g36 in the centre of the lake were performed to reconstruct the interrelation between lake hydrology and climate variability of the last 11 000 yr principal component analyses pca analyses enabled us to extract the three system variables runoff lake level water budget and salinity as the major factors which have influenced the lake history during a highly variable holocene climate we can also demonstrate that the independent variable total organic carbon toc is not only a function of bio productivity in lakes under warm wet climate conditions but more frequently related to surface runoff processes which can result in over estimation of pollen types used for climate reconstructions a combined consideration of all system variables with lithological parameters catchment characteristics and the local groundwater situation show that lake formation and its persistence strongly depended on local rainfall runoff and the status of the underlying aquifer our results indicate remarkable differences between the early holocene and mid to late holocene lake formation owing to changes in the aquifer system beneath the lake at about 10 700 cal bp freshwater lake formation starts with extreme runoff events under a wet climate repeated dry climate spells of reduced runoff the overall climate during the early holocene points to wet conditions with frequent phases of very high runoff and highest lake levels until about 8900 cal bp extremely low runoff occurred between 8900 and 8100 cal bp indicating already dry climate conditions some hundred years prior to the worldwide recorded responses of the 8 2 ka cold dry event a second period of major dry climate conditions with generally low but fluctuating runoff unstable water budget and deposition of aeolian sand lasted for about 2100 yr between 7500 and 5400 cal bp these climate conditions corroborate previous assumptions of a mid holocene dry period in arid north western china increased runoff after 5400 cal bp under wet climate conditions led to a complete refill of the aquifer at about 5000 cal bp and favoured the development of a saline lake for about 3500 yr in terms of hydrology the time between 5400 and 4000 cal bp appears to be the climate optimum compared with the early holocene wet climate the mid to late holocene local rainfall was less pronounced and displays a general decreasing trend towards complete desiccation of the lake our results indicate an extremely variable moisture availability in arid regions of north western china during the entire holocene owing to the interplay of the east asian summer monsoon with the westerly waves at the boundary of the summer monsoon limit variations from dry to wet climate conditions seem to have been more pronounced than in other monsoon regions of china

formation of the highest sand dunes on earth characterization of dune morphology has historically been based on relationships between dune forms and wind regimes with dune height shown to be sensitive to atmospheric boundary layer depth sand availability and sediment properties while these parameters have been used in numerical simulations to model the occurrences of some types of dunes they cannot alone explain the great diversity in form and size seen on earth and on other solar system bodies here we present results from our studies of dune formation in the badain jaran desert in western china where earth s tallest dunes occur we measured the variability of the dune morphology in this desert on the basis of landsat etm data and we detected the bedrock landforms beneath the aeolian sands by applying gravity methods wind records from stations at the periphery of the desert and srtm topographical data were examined also to augment the interpretation our studies demonstrate that in addition to average wind parameters dune height is highly sensitive to local geology subsurface characteristics and topography and interactions between changing climate conditions and aeolian and fluvial processes these additional factors need to be considered in the interpretation and simulation of dunes on earth we anticipate that analysis of anomalous dune heights like those seen in the badain jaran may also provide critical information on subsurface characteristics and environmental conditions on earth and on other planetary bodies

a holocene sedimentary record from bosten lake china abstract a 9 24 m long sediment record from the kaidu river delta margin of bosten lake northwestern china provides evidence for changes in water balance of the lake during the past 8600 calendar years quantitative and qualitative analyses of detrital components authigenic calcite toc and sr ca molar ratios as well as comparisons with selected ostracod assemblages show that lake level fluctuations at minimum 5 6 m display changes in effective moisture supply mainly driven by the west wind system distinct periods of negative water balances and thus dry conditions are dated to 8 5 8 1 7 3 7 1 around 6 0 at 5 4 5 0 4 6 4 3 3 9 3 6 3 4 3 2 2 6 2 5 1 9 1 1 0 5 0 3 and 0 18 0 05 cal ky bp and match the regional and global pattern of climate shifts during the holocene temporal shifts of moisture availability during mid holocene time were recognised as well and may be attributed to regionally different airflow conditions the last 150 years of rising lake levels are accompanied by strong eutrophication as a result of increased human impact

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

low slip rates and long term preservation of geomorphic features in central asia in order to understand the dynamics of the india asia collision zone it is important to know the strain distribution in central asia whose determination relies on the slip rates for active faults1 2 3 4 5 many previous slip rate estimates of faults in central asia were based on the assumption that offset landforms are younger than the last glacial maximum 20 kyr ago 6 7 8 9 10 11 in contrast here we present surface exposure ages of 40 to 170 kyr obtained using cosmogenic nuclide dating for a series of terraces near a thrust at the northern margin of the tibetan plateau combined with the tectonic offset the ages imply a long term slip rate of only about 0 35 mm yr 1 for the active thrust an order of magnitude lower than rates obtained from the assumption that the terraces formed after the last glacial maximum our data demonstrate that the preservation potential of geomorphic features in central asia is higher than commonly assumed

petrogenesis and tectonic setting of the huhetaoergai granitic pluton in the northern ya gan fault zone northern alxa china constraints from whole rock geochemistry zircon u pb ages and hf isotope compositions this study presents a new data set that contains zircon u pb ages whole rock geochemistry and hf isotopes of the huhetaoergai granitic pluton in the northern ya gan fault zone northern alxa chi

holocene climate development on the central tibetan plateau a sedimentary record from cuoe lake abstract we present a climate record for central tibet spanning the time between 10500 and 1600 cal years bp from a 5 3 m long sediment core from cuoe lake the analyses show that high sr concentration high toc content high c n ratio and enriched 13c of lake sediments corresponded to stronger chemical weathering high productivity high lake level and warmer wetter climate and vice versa as revealed by the variations of these proxies the climatic evolution during this period can be divided into five stages and several substages these are a cold dry stage before 10140 cal years bp a transition stage from 10140 to 8560 cal years bp an optimum stage warm wet from 8560 to 5750 cal years bp a cool dry stage from 5750 to 4000 cal years bp a transition stage from 4000 to 3000 cal years bp and a drying up stage after 3000 cal years bp these changes are presumably reflections of variations in indian monsoon intensity which according to that interpretation should have been enhanced from 8560 cal years bp slightly weakened after 5750 cal years bp and gradually diminished since 3000 cal years bp in this region

impact of tectonics on alluvial landforms in the hexi corridor northwest china abstract the hexi corridor is a cenozoic foreland basin system on the northeast margin of the qinghai tibet plateau the structure is characterised by reverse faults trending nnw or wnw rivers have been affected by sinistral offset by wnw trending faults and dextral offset by nnw trending faults the cenozoic sinistral offset reaches 24 km on the north front fault trending wnw of the qilian mountains on the northeast front fault trending nnw of the yumu mountains a bluff of the hei river terrace has been dextrally offset by 12 m with a rate of 1 2 m ka the vertical movement of the faults has caused the deformation of river terraces and controlled the distribution and migration of the alluvial fans three terraces of the hei river have been vertically dislocated 9 m 4 m and 2 m respectively by a reverse fault with uplift rates of 0 4 1 7 m ka two reverse faults have caused the older alluvial fans to be dissected and the younger fans to be deposited more towards the centre of the jiuquan basin the dislocation of terraces and the migration of alluvial fans suggests that tectonic activity was more intense around 160 and 40 ka bp

a review of current testate rhizopod thecamoebian research in canada thecamoebians are a diverse group of testate rhizopods present in a variety of lacustrine and terrestrial habitats among this group certain agglutinating forms primarily arcellacea have tests that are highly resistant to decay and thus fossilize well although the canadian fossil record of thecamoebians extends back as far as the carboniferous the group is particularly common in quaternary lacustrine and peatland environments from temperate to arctic regions of the country research on thecamoebians during the past few years has resulted in great progress on realizing the potential of this group as an important new class of paleoenvironmental indicator applied research on thecamoebian faunas in canada has emphasized aspects of paleolimnology e g eutrophication ph temperature oxygen levels monitoring of land use changes monitoring effectiveness of remediation efforts in contaminated substrates paleo sea level reconstruction paleo water table assessment and paleoclimatic reconstruction 2002 elsevier science b v all rights reserved

electrical resistivity image of the jingsutu graben at the ne margin of the ejina basin nw china and implications for the basin development 1 magnetotelluric and transient electromagnetic data reveal the graben geometry of a nne striking depression within crystalline basement at the ne margin of the ejina basin we interpret this structure as a late mesozoic pull apart basin which is delineated by nne striking normal faults to the east and west satellite imagery srtm elevation data and previously published geophysical data of our work group suggest that the graben is part of normal fault system that continues at least 140 km farther to the south thus forming the eastern margin of the ejina basin nne striking normal faults are atypical in a regional context where nw striking and ene striking fault systems prevail thus this feature marks a distinct difference of the ejina basin when compared to other basin structures in the china mongolia border region

the dry holocene megathermal in inner mongolia the paleoclimate since 14 kyr bp 14c age was reconstructed based on a 16 22 m long sediment core collected from lake yanhaizi a saline lake located near the northern limit of the east asian summer monsoon in inner mongolia coarse sediments were deposited there during a shrinkage phase of the lake when sand dunes reactivated these sediments have low organic carbon contents but high maturity indices indicating that they were deposited in an arid environment by contrast based on high organic contents and low maturity indices fine sediments were deposited during periods of high lake stand in a humid environment it was in general dry between 8 0 and 4 3 kyr bp the above dry and wet phases are consistent with those recovered from the arid semiarid transition zone elsewhere but are unlike the widely perceived humid holocene megathermal reported in east china and the newly reconstructed record in the alpine retreat lake in taiwan the discrepancy may be due to a relative insensitivity to humidity changes in these two areas since they have both been under the total influence of the summer monsoon on the other hand much enhanced evaporation over higher monsoon precipitation at lake yanhaizi reduces the effective humidity in the warm climate near the northern boundary of the summer monsoon this also accounts for the fact the high temperature holocene megathermal as revealed in the okinawa trough and the northern south china sea is correlated to the dry phases at lake yanhaizi conversely the 4 2 kyr bp coldest period in the holocene corresponds to a wet phase at lake yanhaizi

quaternary environmental changes in the drylands of china a critical review abstract this paper reviews our current understanding of quaternary climate and landscape changes in the desert areas of northern china a key portion of the middle latitude drylands on earth combining earlier studies with our recent research and experience we offer a comprehensive picture of the state of chinese deserts during the quaternary and in the interest of enhancing future research identify knowledge gaps and areas of uncertainty lacustrine deposits found over an area ranging from china s western taklamakan desert to the eastern hunshandake sandy lands suggest that extensive lakes occurred in china s deserts during the pleistocene analysis of digital elevation models from srtm shuttle radar topography mission data supports this interpretation and shows the significant extent of these former lakes new estimates of mean annual evaporation of ca 1000 mm from lake surfaces and ca 100 mm from land surfaces confirms that local and regional rainfall is critical for maintenance of desert lakes in this temperate zone especially during intervals when the mean annual rainfall is more than 100 mm rapid shifts between sand seas and lakes in geologically and environmentally diverse settings suggest that the drylands of china are very sensitive ephemeral systems and not long lasting as previously thought available chronologies suggest that there were large lakes in the western taklamakan desert and the chadamu basin during mis marine isotope stage 3 at 30 ka probably related to a period of strong influence of northern hemispheric westerly winds channels and elevation models revealed by srtm data and remains of lacustrine sediments also indicate that there was a large lake in the hunshandake sandy lands in the eastern portion of the desert belt during the quaternary there is significant evidence that during the middle holocene strong summer monsoons led to a relatively large increase in moisture availability in the entire desert belt of northern china lacustrine records from the badain jaran desert in western inner mongolia suggest that it was generally dry before 10 cal ka becoming wetter from 10 to 4 cal ka and dry again afterwards study of palaeosols widely occurring in dune stratigraphy in the eastern portion of the desert belt suggests that there was a period of wet and warm climate in this region during the mid holocene optimum at a minimum between 6 ka and 4 ka but possibly lasting longer recent observations dealing with the generation and transport of dust from central asia indicate that the causal relationship between sand seas and loess sequences is not as close as previously assumed these results suggest that there is an urgent need to examine whether the frequency and amplitude of climatic variation in chinese deserts are somehow similar to that having occurred in the sahara desert of north africa deserts in northern china were also important focal regions for neolithic cultures during intervals when environmental conditions supported a denser vegetative cover there is evidence that some areas of woody vegetation to the west of badain jaran desert were deforested by humans by ca 4000 yr b p although it is still debatable whether humans have had a significant impact in other areas at that time opinions on the severity of desertification vary and are sometimes contradictory due to the lack of long term field based investigations

magma mixing in granitic rocks of the central sierra nevada california abstract the el capitan alaskite exposed in the north american wall yosemite national park was intruded by two sets of mafic dikes that interacted thermally and chemically with the host alaskite comparisons of petrographic and compositional data for these dikes and alaskite with published data for sierra nevada plutons lead us to suggest that mafic magmas were important in the generation of the sierra nevada batholith specifically we conclude that 1 intrusion of mafic magmas in the lower crust caused partial melting and generation of alaskite rhyolitic magmas 2 interaction between the mafic and felsic magmas lead to the observed linear variation diagrams for major elements 3 most mafic inclusions in sierra nevada plutons represent chilled pillows of mafic magmas related by fractional crystallization and granitoid assimilation that dissolve into their felsic host and contaminate it to intermediate granodioritic compositions 4 vesiculation of hydrous mafic magma upon chilling may allow buoyant mafic inclusions and their disaggregation products to collect beneath a pluton s domed ceiling causing the zoning mafic margins to felsic core that these plutons exhibit

asynchronous holocene optimum of the east asian monsoon abstract the spatial and temporal distribution of summer monsoon precipitation or effective moisture during the holocene has been reconstructed on the basis of geological data including lake levels pollen profiles and loess paleosol records in addition the summer july precipitation increment effective precipitation and monsoon strength index have been obtained from numerical modeling experiments both geological data and numerical modeling indicate that the holocene optimum as defined by peak east asian summer monsoon precipitation was asynchronous in central and eastern china reaching a maximum at different times in different regions e g ca 10 000 8000 yr ago in northeastern china 10 000 7000 yr ago in north central and northern east central china ca 7000 5000 yr ago in the middle and lower reaches of the yangtze river and ca 3000 yr ago in southern china in southwestern china the maximum appeared ca 11 000 yr ago but probably was related to the maximum landward extension of the indian summer monsoon the regional shift in the maximum precipitation belt from northwest to southeast over the past 10 000 yr is interpreted as a response to changing seasonality related to orbital forcing of the climate the southeastward shift of the east asian summer monsoon maximum is consistent with the progressive weakening of the summer monsoon as the summer solar radiation anomaly decreased progressively through the holocene and the east asian monsoon index declined while the early maximum in southwestern china matches the maximum of the indian monsoon index

nd sr isotopic mapping of the chinese altai and implications for continental growth in the central asian orogenic belt article i nfo the chinese altai orogen is a typical domain of the central asian orogenic belt and in previous syntheses was divided into six tectonic units or terranes in this paper 41 new and 36 published whole rock nd and sr isotopic data for granitoid intrusions and mafic dykes within units 2 and 3 of the central altai and units 4 to 6 of the southern altai were used for isotopic mapping the age of the samples used is known from u pb zircon dating end t values range from 4 to 2 in the central altai units 2 and 3 and from 1 4 to 6 in the southern altai units 4 and 5 and up to 8 4 in unit 6 correspondingly nd model ages tdm decrease from 1 6 1 1 ga in the central altai to 1 0 0 5 ga in the southern altai except for a continental fragment in unit 4 isr is elevated in the central units decreasing to b0 705 in the southern units 5 and 6 these results demonstrate that the central altai contains widespread old crustal components in its basement whereas the southern altai comprises a higher proportion of juvenile crust when integrated with published u pb zircon ages our data show that new crust grew southwards in the chinese altai in addition our data suggest that units 2 and 3 are a single tectonic unit whereas the southern altai unit 4 which previously was regarded as a single young accretionary terrane should be subdivided into two units a younger arc and an older continental fragment the granitoids in the chinese altai can be divided into syn and post non orogenic groups the syn orogenic granitoids have ca 50 80 mantle derived component whereas the post non orogenic granitoids contain ca 70 90 the generation of syn and post non orogenic granitoids represents horizontal lateral and vertical crustal growth which contributed ca 18 28 and 7 8 respectively to the area of the chinese altai this work shows that isotopic mapping is an effective approach to elucidate terrane composition in the central asian orogenic belt and thereby better constrain palaeozoic crustal growth

palynology of indian and european forest clearance and farming in lake sediment cores from awenda provincial park ontario palynologic analyses of four short cores collected along shallow to deep water transects in second and gignac lakes indicate two periods of forest clearance for farming the first deforestation was by huron indians between a d 1450 and 1650 when a maple acer beech fagus and oak quercus forest was cleared and corn zea planted this disturbance is identified by decreased tree pollen and increased pteridium artemisia and other herbs and is confirmed by zea pollen in gignac lake from 1650 to 1875 there was a forest succession to oak birch betula and pine pinus following this recovery european loggers and farmers cleared this forest and attempted farming besides a reduction in tree pollen a product of this deforestation includes the pollen of weedy ambrosia gramineae and introduced european rumex and plantago during the last 25 years an increase in tree pollen indicates local forest recovery consistent with present land use by relating upland vegetation successions to lacustrine alg

growing pattern of mega dunes in the badain jaran desert in china revealed by luminescence ages abstract sand dunes up to 400 m high are common in the badain jaran desert in china but how and why mega dunes grow remains unclear timing is the most critical to clarify this issue the chronological data are still limited with only a few 14 c ages from carbonate not the direct age of the dune and a few thermoluminescence tl ages whose unbleachable residual signals may result in uncertainty in age optically stimulated luminescence osl dating uses quartz or feldspars and thus directly dates the sands it could also be completely reset by daylight with no residual signals we here report for the first time a batch of osl ages and discuss the pattern of the mega dune growth field observation showed that wet sand layers could be exposed in the slope surface and could be easily seen due to its wetness and calcareous cement causing stronger resistance to wind deflation relative to the adjacent sands wet sand layers are normally situated on the mega dune windward slope and sometimes could even be seen near the top of a mega dune with well preserved original bedding layers making them the ideal locations for collecting luminescence samples our four osl samples collected from the barunbaoritaolegai sand mountain bsm show that osl ages are 4 4 0 5 5 6 0 5 11 9 0 9 and 125 11 ka respectively from top to bottom these ages are concentrated in the early to middle holocene and the last inter glaciation corresponding to mis 5e based on field observation and osl ages we propose that the mega dunes grow mostly during humid periods with water as cementing agents to build up the sands the issues such as the source of the water how the water seeps into the high sand dunes how the loose sands could build up to mega height etc require further study

a 2000 year geochemical record of palaeoclimate and hydrology derived from dune sand moisture abstract chloride concentrations in the interstitial water of the unsaturated zone in dune sands of the badain jaran desert northwestern china have been used to examine the recharge history over the last 2000 years using a chloride mass balance approach the estimated 0 9 mm yr 1 recharge represents approximately 1 of annual precipitation in the western part of the desert and this low but finite infiltration allows preservation of this record the 30 m deep profile yields a total archive equivalent to 2050 years with well preserved climatic events of 30 50 years duration periods of relatively dry years occurred during ad 100 250 350 600 870 1220 1330 1450 1570 1720 1780s and 1900 1970 the unsaturated zone profile provides a robust climate record with a resolution of 20 yr comparable favourably to tree ring and ice core records in this region

tectonic and climatic controls on the spatial distribution of denudation rates in northern chile 18 s to 23 s determined from cosmogenic nuclides in the arid region of northern chile the environmental conditions are favorable for measuring tectonic and climatic influences on catchment denudation rates in the absence of vegetation previous studies of denudation rates from cosmogenic 10be and 26al concentrations are limited to single drainages in this study we examine catchment to orogen scale spatial variation in denudation rates between 18 23 s in the coastal and western cordilleras of northern chile 10be and 26al data were obtained from 33 catchments to examine the relative roles of tectonics and climate on catchment averaged denudation rates at broader scales we examine whether denudation rates and orogen topography reflect the 3d plate geometry of the region cosmogenic nuclide derived denudation rates range from 0 4 0 5 to 20 6 1 5 m myr in the coastal cordillera and from 1 4 0 7 to 168 0 19 8 m myr in the western cordillera the controls on the denudation rates are evaluated using a statistical factor analysis of ten selected catchment parameters denudation rates indicate a strong linear relationship with channel steepness indices but insignificant correlations and covariation with mean annual precipitation rates drainage area stream order mean elevation mean local relief mean basin slope and analyzed grain size of the sampled sediments moreover denudation rates are better correlated with tectonic controls at catchment scale than orogen scale plate tectonics in the western and coastal cordillera

the occurrence soil parameters and genesis of rubified soils fuchserden of northeastern germany abstract the local occurrence of red subsoils on the late pleistocene sandy deposits of the northern european lowlands invites investigation into the formation and paleoenvironmental significance of these soils according to the world reference base for soil resources wrb these soils are classified as rhodic brunic arenosols or chromic brunic arenosols however because of their unclear origins these soils are still not considered in the german guidelines for soil mapping we aim to characterize the genesis of these rubified soils by combining pedological findings with chemical analyses and micromorphological studies at four sites in southeastern brandenburg germany our novel analytical approach differentiates pedogenic iron hydr oxides using a combination of fourier transform infrared multiple internal reflection ftir mir spectroscopy and sequential sample heating from 21 c to 100 c 250 c 500 c and 950 c together with a comparison of synthetic iron hydr oxides the results of this analytical approach demonstrate that the mineralogy of these rhodic brunic arenosols and chromic brunic arenosols are characterized mainly by hematite some goethite and minor amounts of maghemite are also present our results confirm recent findings from jankowski 2013 that rubification is not primarily a relict process in central european soils consequently the german guidelines for soil mapping require revision the high total iron contents in the rubified soils suggest strongly that the iron is allochthonous in origin emphasizing the importance of lateral inputs of iron compounds in the genesis of these soils this finding is highly consistent with the translocation catena concept sommer and schlichting 1997 i e the rhodic brunic arenosols and chromic brunic arenosols studied here formed due to inputs of allochthonous compounds these rubified soils examined in this study share some genetic features with other soils described from central europe such as the lockerbraunerden or the ockererden further research should focus on these commonalities and compare the genetic pathways of such soils to support the argument that these soils should be considered in a separate soil class in the german guidelines for soil mapping

lake evolution in the tengger desert northwestern china during the last 40 000 years climatic changes inferred from lacustrine deposits and lake level fluctuations in northwestern and central china are mainly based on paleoclimatic records from the tibetan plateau while there is still a lack of data relating to the semiarid arid desert regions of inner mongolia in the tengger desert different paleolake levels at baijian hu are documented by six paleoshorelines and stratified lake carbonates the highest lake level occurred ca 39 000 14c yr b p and prevailed over about 16 000 km2 from sediment structure geochemical composition and ostracods we infer humid cool conditions until 23 000 14c yr b p in the northern badanjilin desert at gaxan nur sogu nur high lake levels can be deduced from mollusc bearing paleobeaches and lake carbonates which have been dated to 34 000 14c yr b p and indicate a lake that covered some 32 000 km2 after ca 20 000 yr b p the climate became dry with increased eolian activity and decreasing lake levels reestablishment of wet conditions occurred ca 13 000 yr b p the holocene is represented by stratified lake deposits that alternate with fluvial and eolian deposits indicating a longterm oscillating trend toward arid conditions the existence of widespread freshwater lakes during the late pleistocene indicates a semihumid climate without an accompanying fall in temperature to arctic conditions

late quaternary lake evolution in the gaxun nur basin central gobi desert china based on quartz osl and k feldspar pirir dating of paleoshorelines paleoenvironmental changes in the gobi desert of mongolia are of global significance because fluvial and lacustrine deposits in the region constitute one of the dominant sources of northern hemisphere dust a series of well preserved geomorphic shoreline features at different elevations around the gaxun nur basin central gobi desert indicate past fluctuations of the basin s terminal lake we measured the exact elevation of shorelines in the basin using a differential global positioning system and found six shorelines at similar to 24 similar to 20 similar to 18 similar to 16 similar to 15m and similar to 8m above the modern basin floor quartz optically stimulated luminescence and k feldspar postinfrared infrared stimulated luminescence methods were used to date these shoreline features the reliability of the dates was confirmed using internal checks of luminescence characteristics and by comparing the quartz and kfeldspar ages our results suggest a lake developed in the gaxun nur basin by at least similar to 121 ka lake levels increased from similar to 8 to similar to 24m from similar to 121 to similar to 85 ka a 20 13 m deep lake again formed in the basin between similar to 8 4 and 0 8 ka monsoonal precipitation and temperature variations during marine isotope stage 5 and the mid late holocene were the likely causes of paleolake formation and lake level fluctuations copyright c 2017 john wiley sons ltd

holocene east asian monsoonal precipitation pattern revealed by grain size distribution of core sediments of daihai lake in inner mongolia of north central china abstract two sediment cores recovered in the central part of daihai lake in north central china were analysed at 2 to 4 cm intervals for grain size distribution grain size distributions of the lake sediments are inferred to be a proxy for past changes in east asian monsoon precipitation such that greater silt size percentage and higher median grain size reflect increased monsoonal precipitation rates the grain size record of daihai lake sediments spanning the last ca 10 000 yr indicates that the monsoonal precipitation in the lake region can be divided into three stages the early middle and late holocene during the early holocene before ca 7900 cal yr bp the median grain size md and the silt fraction content were relatively low and constant suggesting relatively low precipitation over the lake region the middle holocene between ca 7900 and 3100 cal yr bp was marked by intensified and highly variable monsoonal precipitation as indicated by high and variable md values and silt contents of the lake sediments during this period average precipitation rate gradually increased from ca 7900 to 6900 cal yr bp displayed intense oscillations between ca 6900 and 4400 cal yr bp and exhibited a decreasing trend while fluctuating from ca 4400 to 3100 cal yr bp although generally high during the middle holocene both the md and the silt content assumed distinctly low values at the short intervals of ca 6500 6400 6000 5900 5700 5600 4400 4200 cal yr bp implying that monsoonal precipitation might have been significantly reduced during these intervals during the late holocene since ca 3100 cal yr bp grain size values suggest that precipitation decreased however during the late holocene relatively higher md values and silt contents occurring between ca 1700 to 1000 cal yr bp may denote an intensification of hydrological cycles in the lake area changes in the east asian monsoonal precipitation were not only directly linked with the changing seasonality of solar insolation resulting from progressive changes in the earth s orbital parameters but also may have been closely related to variations in the temperature and size of the western pacific warm pool in the intensity of the el nino southern oscillation and in the path and strength of the north equatorial current in the western pacific

late pleistocene and holocene aeolian dust deposition in north china and the northwest pacific ocean abstract rates of dust deposition in the north pacific and the central loess plateau of china show a poor correlation during the last 30 000 yr although in both cases the dust was derived from deserts in northern china loess accumulation rates were high at the time of the last glacial maximum while dust flux to the north pacific was low at this time maximum dust flux to the north pacific is recorded in the mid holocene but holocene rates of loess accumulation have been low these differences are shown to reflect the different nature of the wind conditions responsible for dust transport to the loess plateau and the north pacific dust transport responsible for formation of the loess occurred mainly in the lower 1 5 km of the atmosphere and was accomplished by cold low level northwesterly winds associated with cold waves emanating from the mongolian anticyclone at present such conditions occur quite frequently in winter but during the coldest phases of the pleistocene they probably also occurred in the spring and summer long range dust transport from northern china to the north pacific requires that the dust is lifted to high levels above 3 km where it can be incorporated into the strong mid latitude westerlies strong vertical motions of the atmosphere occur most frequently in the spring when the mongolian anticyclone begins to weaken and frontal depressions move across the deserts of northern china such frontal depressions were probably more frequent during the climatic optimum of the mid holocene and during previous interglacials changes in continental aridity have probably played a minor role in controlling the magnitude of the dust flux to the north pacific

the paleolimnology of haynes lake oak ridges moraine ontario canada documenting anthropogenic and climatic disturbances haynes lake is a small kettle lake located on the oak ridges moraine and is within the greater metropolitan area of toronto ontario canada s most populous region lake sedimentation flux rates diatoms and thecamoebians extracted from a benthic core were used as biological proxies to evaluate changes in water quality through time as a function of anthropogenic activity and changing climate there were two periods of disturbance to the haynes lake ecosystem from ca 8 500 years before present ybp through to ca a d 2003 which were significant enough to cause changes in lake sedimentation the diatom flora and thecamoebian fauna the first disturbance was concomitant with the decline in global temperatures following the hypsithermal climate optimum ca 4 700 ybp the most significant disruption to haynes lake over the last 8 500 years however was the settlement of europeans and subsequent urban development ca a d 1875 including the construction of a road immediately adjacent to the lake anthropogenic disturbance of inorganic clays in the recent paleosediment record 5 cm is indicative of more recent eutrophication events

slag inclusions in iron objects and the quest for provenance an experiment and a case study slag inclusions are found within most archaeological bloomery iron artefacts and are remainders of slag created during the smelting and smithing processes although they are widely believed to provide data with the potential for provenancing iron artefacts previous slag inclusion studies have mostly proven inconclusive the main aim of the work reported here is to analyse experimental smelting and smithing assemblages including ore furnace lining fuel and slag to compare these to slag inclusions in the resulting bloom and worked objects and then explore the relationships between ore slag and slag inclusions this study has revealed that the composition of slag inclusions most closely relates to the smelting slag produced whereas provenance to a specific ore would be difficult due to the chemical variability derived from furnace lining fuel and any fluxes used some compounds in the slag inclusions are particularly affected during smithing of the artefact i e those present in the sand flux and fuel used however trends are observed in the k2o mgo mno sio2 al2o3 sio2 al2o3 mgo al2o3 k2o and al2o3 cao ratios that allow comparison between slag inclusions and smelting slag in these experiments and may therefore be used during other provenancing attempts the knowledge gained from the experimental assemblages was subsequently applied to an archaeological case study examining objects from the 900 cal bc smithing site of tel beth shemesh israel and the 930 cal bc smelting site of tell hammeh jordan the analyses suggest that none of the artefacts examined derived from the hammeh smelting system c 2009 elsevier ltd all rights reserved

a high resolution absolute dated holocene and deglacial asian monsoon record from dongge cave china abstract we present a continuous record of the asian monsoon over the last 16 ka from 18o measurements of stalagmite calcite over 900 oxygen isotopic measurements providing information on shifts in monsoon precipitation are combined with a chronology from 45 precise 230th dates 18o and therefore asian monsoon intensity generally follows changes in insolation although changes in 18o are generally accommodated in abrupt shifts in contrast to smoothly varying insolation indicating that threshold effects may be important 18o decreased dramatically 3 at the start of the holocene 11 5 ka and remained low for 6 ka four positive 18o events centered at 11225 97 yr bp 1 05 10880 117 yr bp 1 15 9165 75 yr bp 1 4 and a double event centered at 8260 64 yr bp 1 1 and 8080 74 yr bp 1 0 punctuated this period of high monsoon intensity all four events correlate within error with climate changes in greenland ice cores thus the relationship between the asian monsoon and the north atlantic observed during the glacial period appears to continue into the early holocene in addition three of the four events correlate within error with outburst events from lake agassiz the decline of monsoon intensity in the mid late holocene is characterized by an abrupt positive shift in 18o which occurs at 3550 59 yr bp 1 1 in 100 yr in addition the holocene is punctuated by numerous centennial and multi decadal scale events amplitudes 0 5 to 1 up to half the amplitude of the glacial interstadial events seen in the last glacial period thus holocene centennial and multi decadal scale monsoon variability is significant although not as large as glacial millennial scale variability the monsoon shows a strong connection with northern south american hydrological changes related by changes in itcz position spectral analysis of the 18o record shows significant peaks at solar periodicities of 208 yr and 86 yr suggesting variation is influenced by solar forcing however there are numerous other significant peaks including peaks at el nino frequencies observed for high resolution portions of the record between 8110 and 8250 yr which suggest that changes in oceanic and atmospheric circulation patterns in addition to those forced by solar changes are important in controlling holocene monsoon climate in addition for this high resolution portion we observe a distinctive biennial oscillation of the asian monsoon which has been associated with the tropospheric biennial oscillation tbo

a holocene climatic record from arid northwestern china abstract the history of climatic changes during the interval 8500 3000 cal yr b p has been reconstructed from stratigraphical and chronological studies and the results of total organic carbon toc total inorganic carbon tic element composition pollen and stable isotope analyses of a section along the hongshui river in the southern tengger desert nw china the record suggests that from 8450 bottom of the studied section to 7500 yr b p the climate was characterized by instability from 7500 to 5070 yr b p the climatic conditions improved and can be divided into two parts a warm humid spell between 7290 and 6380 yr b p during which the average temperature was 3 4 c higher than that of today and a warm dry spell lasting from 5950 to 5720 yr b p the climate deteriorated between 6380 and 5950 yr b p from 5720 to 5070 yr b p the temperature decreased but humidity increased an abrupt temperature drop occurred between 5340 and 5290 yr b p that indicated the decline of the warmer and humid mid holocene climate from 5070 yr b p onward the climate oscillated significantly and there were three large temperature decreases coinciding with high mountain glacier advances between 5070 4670 yr b p 4300 3740 yr b p and 3410 3230 yr b p top of the section respectively the climatic fluctuations recorded in the southern tengger desert appear in phase with climatic changes recognized in the tibetan plateau suggesting that the period between 7290 and 6380 yr b p was the most warm humid spell one extremely dry event occurred at ca 3000 yr b p and subsequently the fluvial lacustrine depositional process terminated and wind action prevailed in the area both of these features can be attributed to the rapid strengthening and weakening of the summer monsoon circulation which are closely connected with global changes

holocene moisture evolution across the mongolian plateau and its surrounding areas a synthesis of climatic records abstract based on the review of 26 high standard holocene climatic reconstructions mainly pollen based from the mongolian plateau and its surrounding areas temporal and spatial patterns of the holocene moisture evolution are synthesized the regionally averaged moisture history from the summer monsoon influenced semiarid belt in china i e region a demonstrates that the moisture index curve is broadly in agreement with the synthesized east asian monsoon strength curve both following the general trend of the west tropical pacific sst that is in turn the delayed response to the northern hemispheric summer solar insolation the regionally averaged moisture indices from the winter monsoon dominated southern siberia including lake baikal area and the altai mountains i e region b exhibit a general declining trends since 10 6 9 6 cal kyr bp being largely consistent with the trends of the annual precipitation and the warm season temperature in the russian plain the consistency might be attributable to the holocene declining trend of the warm season temperature in north atlantic region the predominant feature of the regionally averaged moisture index from the westerlies affected northern xinjiang i e region c is a persistent increasing trend since 8 cal kyr bp the wetting trend of northern xinjiang during the past 8000 years might be attributable to the increasing trend of winter insolation and to the associated increasing trend of cold season temperature in northwestern europe the chronological correspondences between dry phases and warm intervals in the arid areas of the mongolian plateau i e northern mongolian plateau within mongolia and southern mongolian plateau within china region d lend a support to the proposal that the mid holocene dry phase was most likely the result of mid holocene high warm season temperature

discriminating sediment archives and sedimentary processes in the arid endorheic ejina basin nw china using a robust geochemical approach abstract geochemical characteristics have been intensively used to assign sediment properties to paleoclimate and provenance nonetheless in particular concerning the arid context bulk geochemistry of different sediment archives and corresponding process interpretations are hitherto elusive the ejina basin with its suite of different sediment archives is known as one of the main sources for the loess accumulation on the chinese loess plateau in order to understand mechanisms along this supra regional sediment cascade it is crucial to decipher the archive characteristics and formation processes to address these issues five profiles in different geomorphological contexts were selected analyses of x ray fluorescence and diffraction grain size optically stimulated luminescence and radiocarbon dating were performed robust factor analysis was applied to reduce the attribute space to the process space of sedimentation history five sediment archives from three lithologic units exhibit geochemical characteristics as follows i aeolian sands have high contents of zr and hf whereas only hf can be regarded as a valuable indicator to discriminate the coarse sand proportion ii sandy loess has high ca and sr contents which both exhibit broad correlations with the medium to coarse silt proportions iii lacustrine clays have high contents of felsic ferromagnesian and mica source elements e g k fe ti v and ni iv fluvial sands have high contents of mg cl and na which may be enriched in evaporite minerals v alluvial gravels have high contents of cr which may originate from nearby cr rich bedrock temporal variations can be illustrated by four robust factors weathering intensity silicate bearing mineral abundance saline alkaline magnitude and quasi constant aeolian input in summary the bulk composition of the late quaternary sediments in this arid context is governed by the nature of the source terrain weak chemical weathering authigenic minerals aeolian sand input whereas pedogenesis and diagenesis exert only limited influences hence this study demonstrates a practical geochemical strategy supplemented by grain size and mineralogical data to discriminate sediment archives and thereafter enhance our ability to offer more intriguing information about the sedimentary processes in the arid central asia

holocene environmental change inferred from a high resolution pollen record lake zhuyeze arid china a high resolution pollen record c 50 yr sample from terminal lake sediments in the shiyang river drainage basin on the present margin of the summer monsoon was used to reconstruct vegetation and climate history during the holocene forest trees from mountainous areas of the drainage including sabina picea and pinus dominated pollen assemblages in the early holocene 11 6 7 1 cal ka in the mid holocene 7 1 3 8 cal ka desert and steppe shrubs and herbs around the lake including nitraria poaceae compositae and artemisia were dominant the late holocene 3 8 0 cal ka was again dominated by alternation of pinus sabina tree pollen and desert steppe pollen the early holocene forest expansion in the mountains and subsequent increase in the river transport of tree pollen corresponds with maximum precipitation during the east asian summer monsoon maximum the timing of these changes in our record from arid china is different from that of east china where the holocene monsoon maximum appeared in

geochemical indicators in lake sediment of upland erosion caused by indian and european farming awenda provincial park ontario neutron activation analysis loss on ignition loi and x ray diffraction of eight cores collected in second and gignac lakes are correlated with historic and palynologic records to identify elements linked to erosion from deforestation and farming forest disturbance and farming are identified in cores of organic detritus sediment gyttja by decreased loi and increased na mg ba al ti and dy loi is not suitable for identifying forest disturbances in carbonate sediments from neutron activation analysis of carbonate mud only na al and dy indicate erosion elements linked to the quantity of organic matter in sediments include u v and cl whereas mn and i in surface sediments presumably correspond with variations in the oxidation potential and plant productivity respectively sedimentation patterns relate to basin morphology in gignac lake the basin is steep sided and relatively deep clastic detritus entering the lake is carried over the shallow nearshore carbonate bank into deeper water in sec

in situ u pb zircon dating using laser ablation multi ion counting icp ms high resolution in situ u pb zircon geochronology on zoned grains can obtain isotope signatures from multiple growth or thermal events we present a method using laser ablation multicollector inductively coupled plasma mass spectrometry la mc icp ms to overcome complications associated with intricately zoned zircon crystals through in situ sampling of zircon volumes as small as 12 m 25 m and 40 m in diameter by about 10 m in depth high precision u pb age of a series of zircon standard covering a wide age range of 30 to 1 065 ma was acquired using la mc icp ms the precision of measured pb u ratios in homogeneous zircon is about 2 2 resulting in routinely achieved precision of u pb ages obtained by external calibration of 1 2 or better all masses of interest can be simultaneously recorded with a multi ion counting system mic operating in static mode and the short ablation required to achieve such precision results in spatial resolution that is superior to comparable u pb zircon analyses by single collector icp ms the resulting present u pb age for five zircon reference samples and two geological samples show an excellent agreement with the previously reported id tims or shrimp data

holocene monsoonal climate changes tracked by multiproxy approach from a lacustrine sediment core of the subalpine retreat lake in taiwan abstract the aim of this study is to improve the understanding of environmental changes and the linkages with the dynamics of the east asian monsoon eam during the holocene in the western north pacific we analyzed the pollen diatom and weak acid leachable fractions associated with extracted organic compounds of lacustrine sediments retrieved from the subalpine retreat lake in northwestern taiwan during the early holocene 10 100 8600 cal bp cool climate was inferred by the dominance of grass pollen with poor preservation of diatom valves in the record at that time derived biomarkers were also dominated by long chain alkanes originating from herbs the following holocene optimum 8600 6400 cal bp was characterized by a remarkable increase of tree pollen indicating the warmer and humid climate and a stronger summer eam the possible enhanced monsoon driven precipitation resulted in higher contents of total organic carbon buried in sediments however the climate and precipitation of the alpine area in taiwan might have been unstable the high variability of wetland pollen and diatom abundance reveals weak periods of eam during the late holocene optimum 6400 4500 cal bp the hiatus in the deposit during 4500 2100 cal bp suggests the continuously decline of the eam during the last 2100 years dominated wetland plant pollen accompanying stable diatom abundance indicated humid climatic conditions and a stable increase of the eam the climatic condition of study area was similar with modern situation during this late holocene