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

eocene tibetan plateau remnants preserved in the northwest himalaya in the northwest himalaya deeply incised mountain ranges contrast with high elevation low relief areas such as the deosai plateau in northern pakistan thermochronology data from the deosai plateau together with thermal history modelling suggest that this plateau along with other morphologically similar surfaces is a remnant of an eocene southwestern tibetan plateau

nd and sr isotopic variations in chinese eolian deposits during the past 8 ma implications for provenance change a record of changes in nd and sr isotopic composition of the eolian deposits from the central loess plateau has been determined for the past 8 ma the isotopic records of the silicate fraction of the quaternary and tertiary eolian deposits allow interpreting the interplay between the sr isotopic variations in the eolian deposits and the late cenozoic tectonic and climatic changes the results indicate that the temporal variations of nd and sr isotopes show remarkable changes around the beginning of the quaternary the lower values of the 143 nd 144 nd and the decreasing trend of the 87 sr 86 sr ratios after 2 58 ma ago are attributed to the additions of relatively younger crust materials in response to the climatic cooling and the late cenozoic uplift induced glacial grinding in the high orogenic belts in central asia in this context the substantial changes in climate and tectonics have modified dust sources significantly and the quaternary loess forming processes are preferentially sampling relatively younger and high relief crust materials than that of the tertiary red clay d 2005 elsevier b v all rights reserved

evidence for enhanced aridity in the tarim basin of china since 5 3 ma abstract thick cenozoic deposits formed from the erosion of the northern evolving edge of the tibetan plateau provide opportunities to study the exhumation history and climatic changes within the region such deposits are important because they are located in an actively deforming mountain belt as well as in a rain shadow of the tibetan plateau multi proxy studies indicate that hyperarid climate has prevailed since 5 3 ma ago within the basin this information together with the geometry analysis of syntectonic deposits of the sanju anticline which indicate tectonic deformation at 5 3 ma enable us to better understand the interlay between climatic changes and tectonic uplift our results suggest that the tectonic uplift of the kunlun mountains at 5 3 ma must have been one of the significant regional tectonic events and the uplifted elevation of the kunlun mountains more effectively blocks the penetration of moisture from the indian monsoon into the tarim basin and thus enhances the rain shadow effect this can account for the increasing aridity as well as the formation of the world s second largest active sand desert the taklimakan desert in the tarim basin initiated at 5 3 ma ago

high precision isotopic characterization of usgs reference materials by tims and mc icp ms the pacific centre for isotopic and geochemical research pcigr at the university of british columbia has undertaken a systematic analysis of the isotopic sr nd and pb compositions and concentrations of a broad compositional range of u s geological survey usgs reference materials including basalt bcr 1 2 bhvo 1 2 andesite agv 1 2 rhyolite rgm 1 2 syenite stm 1 2 granodiorite gsp 2 and granite g 2 3 usgs rock reference materials are geochemically well characterized but there is neither a systematic methodology nor a database for radiogenic isotopic compositions even for the widely used bcr 1 this investigation represents the first comprehensive systematic analysis of the isotopic composition and concentration of usgs reference materials and provides an important database for the isotopic community in addition the range of equipment at the pcigr including a nu instruments plasma mc icp ms a thermo finnigan triton tims and a thermo finnigan element2 hr icp ms permits an assessment and comparison of the precision and accuracy of isotopic analyses determined by both the tims and mc icp ms methods e g nd isotopic compositions for each of the reference materials 5 to 10 complete replicate analyses provide coherent isotopic results all with external precision below 30 ppm 2 sd for sr and nd isotopic compositions 27 and 24 ppm for tims and mc icp ms respectively our results also show that the first and second generation usgs reference materials have homogeneous sr and nd isotopic compositions nd isotopic compositions by mc icp ms and tims agree to within 15 ppm for all reference materials interlaboratory mc icp ms comparisons show excellent agreement for pb isotopic compositions however the reproducibility is not as good as for sr and nd a careful sequential leaching experiment of three first and second generation reference materials bcr bhvo agv indicates that the heterogeneity in pb isotopic compositions and concentrations could be directly related to contamination by the steel mortar pestle used to process the materials contamination also accounts for the high concentrations of certain other trace elements e g li mo cd sn sb w in various usgs reference materials

oligocene slow and miocene quaternary rapid deformation and uplift of the yumu shan and north qilian shan evidence from high resolution magnetostratigraphy and tectonosedimentology

tracing dust sources and transport patterns using sr nd and pb isotopes continental dust transported through the atmosphere can be a tracer of atmospheric circulation and transport as well as being a source of information about climate in the dust s source area this information about the provenance of dust transported from desert areas and deposited elsewhere on the oceans and continents can be evaluated using several observational techniques satellite imagery has been used to this end in recent decades and air mass back trajectories have been calculated to trace dust deposits back to their source area another method consists of analysis of the concentration and composition of certain tracers in the dust itself and comparing them to soils and sediments from possible source areas this method has the advantage of being useable for paleo atmospheric circulation and paleo dust transport studies whereas satellite imagery and air mass back trajectories are restricted to relatively recent times we review here different kinds of isotopic tracers that have been used to trace dust provenance but special attention is focused on the use of sr nd and pb isotopes we evaluate their use in studies of both spatially as well as temporally varying continental dust source and transport

chronology and paleoenvironmental records of a drill core in the central tengger desert of china abstract the desertification history of inland asia provides most direct evidence for asian drying history but the formation ages of the most asian deserts are not clear due to the lack of outcrops the tengger desert one of the main proximal deserts of the chinese loess plateau clp is of special paleoclimatic significances for its dust emission and environmental affection here we report lithofacies paleomagnetic ages and paleoenvironmental proxy indexes of the first drill core wedp01 from the central tengger desert paleomagnetism measurements reveal that the core spans from 3 55 ma to present consistent with the electron spin resonance esr dating results the strata of the central desert consist of alluvial fluvial deposits lacustrine fluvial deposits mixed with dust and eolian sand from bottom to top sedimentary analysis reveals that continuous eolian sand started by 0 9 ma marking the initial formation of the tengger desert and the domination of eolian sand in the strata with similar characters of the modern desert appeared by 0 68 ma indicating expansion of the tengger desert the proximal deserts formation and simultaneous increase of dust accumulation in the clp and the north pacific ocean in mid pleistocene demonstrate the role of proximal deserts for the dust loading of northern china and even northern hemisphere our analysis suggests the uplift of tibetan plateau in the mid pleistocene probably played the main role for this drying event and desert formation while global cooling may strength the arid environment of the proximal deserts

grain size of fine grained windblown sediment a powerful proxy for process identification abstract dust transport by the wind is not a uniform process but may occur in different modes according to source area conditions and transport height and distance subsequently these differences are expressed in terms of grain size and fluxes of the aeolian deposits transport distances may vary from several tens of meters to thousands of kilometers while the height accordingly may vary from meters to more than thousand meters a relation with grain size distributions may be established on the base of type occurrences of different loess facies three main loess populations and several subpopulations of primary windblown origin may be defined according to their grain size dominated by fine sand to very coarse silt silt and very fine silt to clay respectively each of them reflects a specific aeolian process and transport conditions it follows that the grain size distribution of a loess deposit is an excellent proxy for the reconstruction of aeolian processes and wind circulation patterns apart from primary pure wind deposition loess may also be affected by secondary post depositional processes examples are settling of loess particles in a lacustrine setting and reworking by rivers or surface runoff although the primary loess characteristics are maintained reworking processes leave also their imprint in the grain size distribution as a useful tool for secondary process identification

unmixed loess grain size populations along the northern qilian shan china relationships between geomorphologic sedimentologic and climatic controls abstract grain size analysis provides a useful tool in reconstructing aeolian transport processes and allows deductions about environmental evolution however the sedimentological mechanisms driving the investigated imprint are often underrepresented in the interpretation of loess sections and may therefore lead to erroneous conclusions we present a study from the north eastern margin of the tibetan plateau qilian shan hexi corridor in which 11 mainly holocene loess sections up to 2 20 m depth and a set of surface samples were analysed for their grain size distribution a three end member mixing model yields grain size populations with modes of 63 m 33 m and 9 m respectively representing the major contributing transport processes from different sources these processes were identified in short term suspension and saltation from fluvial storages low level suspension driven by dust storms and high level suspension from distant sources sedimentology supply availability site specific geomorphology distance to potential sources and climate conditions such as effective moisture controlling dust trapping vegetation covers set up a complex system loess deposition and preservation depend on these steering factors large sediment supply from the last glacial cycle became available for deflation during early holocene moisture optimum this phase is represented by a high contribution of the coarsest grain size population in the late glacial early holocene loess record when climate amelioration allowed the establishment of a dust trapping vegetation cover comparable to mis 3 conditions the mid holocene loess deposits formed under more stable landscape conditions represented by much lower contributions from local sources accordingly relative contribution of far travelled dust was at its climax during the mid holocene the late holocene exhibits a relative increase in dust storm contribution which is in accordance to increasingly drier climatic conditions hence this study suggests a thorough consideration of the different system components when interpreting grain size records obtained from loess deposits

a thermochronological perspective on the morphotectonic evolution of the southeastern tibetan plateau a large part of the southeastern tibetan plateau tp is characterized by low relief surfaces at high elevations 3 5 km the origin of these landscapes and their geodynamic implications with regard to evolution of the southeastern tp has been the subject of considerable debate focusing on this topic this study utilizes fission track and u th he thermochronology to reconstruct the thermal history of the late triassic daocheng granite on which a low relief high elevation landscape has developed results suggest that the plateau surface experienced widespread late jurassic to early cretaceous cooling at a rate of 1 2 c ma followed by minimal regional cooling 0 3 c ma and early miocene enhanced cooling 2 3 c ma along deep valleys at the southern edge of the landscape given the subdued late jurassic to early cretaceous crustal deformation in the study area we relate the coeval cooling to crustal refrigeration and exhumation triggered by northward subduction of the meso tethys ocean along the bangong suture subsequent late cretaceous to cenozoic minimal cooling supports arguments for the formation of a low elevation landform prior to uplift of the southeastern tp the enhanced cooling commenced at the early miocene 15 22 ma along deep valleys and heralded the onset of river incision and surface uplift of the southeastern tp this finding does not support previous proposals claiming that high elevations of the southeastern tp were formed in late miocene time resulting from lower crustal flow but rather supports a model highlighting continental subduction and extrusion along the large tanggula yushu batang red river fault system

the environmental effects of the uplift of the qinghai xizang plateau the intense upheaval of the qinghai xizang plateau took place 2 ma bp the terraces of the yellow river in the lanzhou region and its upper sections provide a record of the uplift of the plateau the interaction of glaciation cycles resulting from climatic changes and pulsating tectonic upheavals are both involved in the record of environmental change across the plateau three tectonic climatic events which are termed respectively the qinghai xizang movement the huanghe yellow river movement and the gonghe movement occurred 2 1 5 1 0 and 0 15 ma bp the upheaval of the qinghai xizang plateau was the trigger mechanism of the asian monsoon the loess plateau was formed in the monsoon triangle of east asia human origins and human evolution may have been stimulated by the uplift of the qinghai xizang plateau

grain size of loess palaeosol and red clay deposits on the chinese loess plateau significance for understanding pedogenic alteration and palaeomonsoon evolution abstract to assess pedogenic modification to grain size distributions of loess palaeosol and red clay deposits on the chinese loess plateau and to understand long term evolution of the east asian palaeomonsoon since the late miocene we investigate a continuous loess palaeosol red clay sequence at lingtai south chinese loess plateau and another parallel red clay sequence at zhaojiachuan central chinese loess plateau by analyzing the grain size distributions of bulk samples and chemically isolated quartz samples the relative intensity of pedogenic alteration of the loess palaeosol and red clay deposits can be quantified comparisons of the grain size distributions and contents of different grain size fractions between the bulk and the quartz samples suggest that pedogenic alteration is apparently stronger in the red clay sequence than in the overlying loess palaeosol deposits furthermore grain size parameters derived from the bulk and the quartz samples such as mean grain size coarse fraction content and u ratio exhibit similar variations in the loess palaeosol sequence quaternary 0 2 6 ma whereas these grain size parameters of quartz samples show different variability from those of bulk samples in the red clay sequence late miocene to pliocene 2 6 7 ma grain size of quartz from the loess palaeosol and red clay deposits exhibits distinct and persistent oscillations from the late miocene to the pleistocene implying that significant fluctuations of the palaeomonsoon climate in east asia might have occurred at least since late miocene time

tracing the provenance of fine grained dust deposited on the central chinese loess plateau eolian dust deposits in north china provide an excellent means of determining past variations in continental paleoclimate and atmospheric circulation however debate still exists on which deserts in east asia are the dominant sources of chinese loess and whether the dust provenance has shifted significantly at different time scales here we present new constraints on the provenance of fine grained dust deposited on the central chinese loess plateau clp by combining electron spin resonance signal intensity and crystallinity index of fine grained quartz contained in samples from two loess paleosol sequences our results show that the fine grained dust deposits on the clp originate mainly from the gobi desert in southern mongolia and the sandy deserts in northern china primarily the badain juran and tengger deserts rather than from the taklimakan desert in western china at least during the last climatic cycle the dominant source of fine grained dust varied significantly from southern mongolia during cold periods to northern china during warm periods the glacial interglacial provenance fluctuations are strongly coupled with changes in the intensity of the near surface northwesterly winter monsoon

mongolian summits an uplifted flat old but still preserved erosion surface in gobi altay and altay mongolia several flat surfaces worn through basement rocks and uplifted during the ongoing tectonic episode to a similar altitude of 4000 m suggests disruption of a single large scale surface new thermochronology and field data show that the plateau surfaces represent uplifted parts of an ancient peneplain that formed during jurassic time the gobi altay and altay flattopped massifs are tectonically and geomorphologically unique their preservation for 150 m y implies that no further tectonic movements occurred before the onset of the last deformation episode 5 3 m y ago it also suggests that very low erosion rates were maintained by a dry climate over millions of years

sr nd isotopic and ree geochemical constraints on the provenance of fine grained sands in the ordos deserts north central china surface sands and sandstones in the ordos region alluvial sands from the surrounding mountains and fluvial sands in the yellow river are systemically collected for granulometric mineralogical geochemical and isotopic analyses fine grained fractions are small for the ordos desert sands as well as alluvial sands of the surrounding mountains whereas they are abundant for fluvial sands of the yellow river quartz feldspar and muscovite are common minerals but their relative proportions are variable for various sediments ree geochemical compositions are roughly identical but isotopic compositions particularly end 0 values of fine grained sands vary significantly in the ordos deserts based on the integrated sr nd isotopic data the possible source areas are isotopically divided into four regions for fine grained sands in the ordos deserts region a the helan yin mountain ranges region b the ordos sandstone areas region d the tarim basin the alxa plateau the hexi corridor the northern qinghai xizang plateau and the yellow river drainage and region e the jungger basin and the southern mongolia through geochemical and particularly isotopic comparisons in combination with expert meteorological and geographical knowledge fine grained sands in the ordos deserts originated both from weathering of local sandstones and from blowing of fine sediments in region d the input from region d is subordinate to the local source for fine grained sands in the ordos deserts contributions from weathering of local sandstones might be roughly homogeneous from the west to the east of the ordos region as well as the input of fine grained sediments from remote areas such as the tarim basin the qinghai xizang plateau and the alxa plateau geographical nd isotopic variations of fine grained sands in the ordos deserts might be caused by the input from adjacent places such as the yellow river drainage due to the near surface winds

mineralogical variation of sr nd isotopic and elemental compositions in loess and desert sand from the central loess plateau in china as a provenance tracer of wet and dry deposition in the northwestern pacific we determined sr and nd isotopic compositions and major trace and rare earth element ree compositions of evaporite and detrital minerals in loess and desert sand from the central loess plateau clp where 80 of the loess deposits in china are found the loess exhibited a narrow range of variation in 87sr 86sr 0 715 0 001 a sequential extraction experiment on the loess however showed that water and acetic acid hoac soluble minerals mainly halite and calcite hydrochloric acid hcl soluble minerals chlorite and phosphate and hcl insoluble minerals illite kaolinite smectite vermiculite feldspar and quartz have distinct 87sr 86sr ratios approximately 0 7111 0 0004 0 7141 0 0004 and 0 7195 0 0010 respectively the water and hoac soluble ratios were regionally uniform and were close to the 87sr 86sr value of river water from the huanghe yellow river and the maximum 87sr 86sr value of spring rainwater in japan suggesting selective solution of eolian halite and calcite into the chinese river water and into the japanese rainwater the mineralogical elemental and sr nd isotopic compositions of hcl soluble and insoluble minerals in the clp loess were different from those of the northern desert sand but were indistinguishable from those of its fine grained fraction supporting the view that the loess is composed of the fine grained fraction of desert sand that was transported to the southeast in the atmosphere the 87sr 86sr end and gd yb values of hcl insoluble minerals in the clp loess were almost identical to those of airborne dust soil minerals and deep sea sediments in the northwestern pacific considered to be of eolian origin suggesting dissolution of the loess evaporite minerals during atmospheric transportation these relationships demonstrate the usefulness of sr isotopes of water and hoac soluble minerals and sr and nd isotope ratios and ree compositions of acid insoluble minerals in loess as provenance markers for wet and dry deposition respectively

bimodal grain size distribution of chinese loess and its palaeoclimatic implications grain size analysis indicates that chinese loess generally shows a bimodal distribution with a coarse and a fine component the coarse component comprising the main part of the loess has pronounced kurtosis and is well sorted which is interpreted to be the product of dust storms generated by low altitude northwesterly winds its grain size reflects the strength of the low altitude circulation in the dust seasons of the year and its percentage provides an indicator of the source area aridity and the frequency of dust storms conversely the fine component has a wide grain size range and is poorly sorted sedimentary illustrations based on the grain size distribution characteristics of bulk samples and of detrital quartz suggest that the fine component probably represents the background dust load of the atmosphere and is mainly transported by high altitude westerly airstreams its grain size provides an estimate of the westerly air stream intensity the coarse and fine components of a loess sample can be mathematically separated by fitting a designated mathematical distribution function to the measured grain size data and this procedure constitutes an approach for reconstructing the palaeowind system of northern china c 2003 elsevier b v all rights reserved

provenance of loess material and formation of loess deposits on the chinese loess plateau abstract results of a multiple isotopic chemical and mineralogical analysis of loess from the three northwestern inland basins the junggar basin the tarim basin and the qaidam basin and the loess plateau region of china are summarized they suggest a qualification of the conventional views that the three northwestern basins were the important source areas of the loess plateau and that the sand deserts were the primary single source of the chinese loess it is argued that the gobi stony desert in southern mongolia and the adjoining gobi and sand deserts the badain jaran desert tengger desert ulan buh desert hobq desert and mu us desert in china rather than the three inland basins are the dominant source areas of the loess plateau however although these gobi and sand deserts are regarded as the main source regions they serve as dust and silt holding areas rather than dominant producers the mountain processes including glacial grinding frost weathering salt weathering tectonic processes and some fluvial comminution in the gobi altay mts hangayn mts and the qilian mts have played an important role in producing the vast amounts of loess sized material for forming the loess plateau

wind blown origin of the pliocene red clay formation in the central loess plateau china abstract in order to determine the depositional processes of the pliocene red clay formation deposited directly beneath the plio pleistocene loess in the chinese loess plateau four red clay sections spanning over 400 km are studied grain size analysis of closely spaced samples in the sections shows that the particles of the red clay are very fine with the sand fraction 63 m being negligible and that all the curves indicating changes in different grain size parameters have a similar pattern the grain size records in the upper part of the four sections are almost identical with the median grain size centered at 4 8 m the ree patterns of 28 samples from the jiaxian red clay section are all characterized by lree enrichments relatively flat hree and slight negative eu anomaly being similar to those of eolian loess and the average upper continental crust these lines of evidence point to a wind blown origin of the red clay deposits accumulation of the loess soil sequences in the chinese loess plateau during the past 2 6 ma can be therefore regarded as the continuation of the pliocene atmospheric dust deposition observations of spatial grain size changes in the loess plateau suggest that the eolian red clay might be transported mainly by the westerlies differing significantly from the overlying loess that was transported essentially by the east asia winter monsoonal winds

magnetostratigraphic record of the late miocene onset of the east asian monsoon and pliocene uplift of northern tibet abstract widespread eolian red clay underlying the plio pleistocene loess palaeosol succession in northern china has been dated magnetostratigraphically back to 8 35 ma indicating that the east asian monsoon started at about the same time as the indian monsoon an initial sedimentation rate of 11 m myr increased gradually to 17 5 m myr by 6 ma and then decreased to 6 m myr between 5 ma and 3 5 ma a marked increase in sedimentation rate and grain size beginning between 3 5 ma and 3 1 ma indicates that the east asian winter monsoon strengthened at this time and intensified further after 2 6 ma the temporal coincidence of the stronger winter monsoon and the pliocene uplift of northwestern tibet just before the onset of the northern hemisphere glaciation indicate that the three events could be causally linked

the age of the taklimakan desert the taklimakan desert is located in the foreland basin of the tibetan plateau we report here the results of stratigraphic investigations of a 1626 meter thick sequence with interbedded wind blown silt from the southern marginal taklimakan desert because the studied section is located downwind of the desert the eolian silt accumulation is closely linked to desert formation our new evidence indicates that shifting sand dunes prevailed in the tarim basin by at least 5 3 million years ago as they do today we attribute this event to late cenozoic climatic deterioration as well as to changes in atmospheric circulation induced by tibetan plateau uplift

natural and anthropogenic sources of east asian dust nd sr isotopic signatures of loess modern dust and their potential source materials are systematically investigated to discriminate the natural and anthropogenic sources of eastern asian dust chinese loess is an eolian deposit that has accumulated over the past few million years and is characterized by a negative nd sr isotopic correlation that implies binary sources for the natural background of eastern asian dust loess in northeastern china shows the highest end 0 value while loess in western china has the lowest end 0 considering the nd sr isotopic signatures of the potential sources we propose that the high end 0 end member is derived from the arid lands around the northern boundary of china while the low end 0 end member originates from the deserts on the northern margin of the tibetan plateau chinese loess plateau deposits are dominated by northern margin tibetan plateau dust suggesting a strong link between the thick eolian deposit in this region and the evolution of the tibetan plateau the long range transported spring dust in both nanjing south china and japan has an nd sr isotopic composition similar to that of loess however spring dust in beijing north china has a much lower end 0 value indicating an additional anthropogenic contribution of low end 0 material possibly from the sandy lands in the adjacent north and west

high resolution magnetostratigraphy of the neogene huaitoutala section in the eastern qaidam basin on the ne tibetan plateau qinghai province china and its implication on tectonic uplift of the ne tibetan plateau abstract the closed inland qaidam basin in the ne tibetan plateau contains possibly the world s thickest 12 000 m continuous sequence of cenozoic fluviolacustrine sedimentary rocks this sequence contains considerable information on the history of tibetan uplift and associated climatic change however work within qaidam basin has been held back by a paucity of precise time constraints on this sequence here we report on a detailed paleomagnetic study of the well exposed 4570 m huaitoutala section along the keluke anticline in the northeastern qaidam basin where three distinct faunas were recovered and identified from the middle miocene through pliocene constrained by these faunal ages the observed thirty three pairs of normal and reversed polarity zones can be readily correlated with chrons 2n 5br of the gpts this study assigns the age of the section to the interval between ca 15 7 ma to 1 8 ma in addition the widely used stratigraphic units the xia youshashan shang youshashan the shizigou and qigequan formations were formed at 15 3 ma 15 3 8 1 ma 8 1 2 5 ma and

re arrangement of atmospheric circulation at about 2 6 ma over northern china evidence from grain size records of loess palaeosol and red clay sequences abstract recent studies have shown that the red clay sequence underlying the quaternary loess of the chinese loess plateau is wind blown in origin continuous atmospheric dust deposition in the past 7 0 ma has been documented to address the wind system that transported the tertiary red clay two north south transects were studied in the chinese loess plateau one of the transects was designed to study spatial changes in grain size of the last glacial interglacial loess records and the other to observe particle changes of the tertiary red clay underlying the quaternary loess the loess transect consists of nine sections and the red clay transect of four sections analyses of closely spaced samples show that there is a strong southward decrease in grain size of both loess and palaeosol horizons of the late pleistocene which is consistent with the idea that the aeolian materials of the quaternary in the loess plateau are transported by the northerly winter monsoonal winds grain size distribution of the red clay sequences however does not show such a change from north to south along the red clay transect the particle size distribution is almost identical in the four sections suggesting that the winter monsoonal winds might have played a less important role in transporting the red clay material it is suggested that the red clay may have been transported by the westerlies from the dust source regions of northwestern china onto the loess plateau a remarkable re arrangement of atmospheric patterns at about 2 6 ma therefore has been recorded by the red clay loess shift it is speculated that this re arrangement of atmospheric patterns may have been caused by the onset of glaciation in the northern hemisphere

kongur shan normal fault type example of mountain building assisted by extension karakoram fault eastern pamir the northernmost segment of the karakoram fault is an active normal dextral wrench fault that bounds the muji tashgurgan pliocene quaternary basin eastern pamir the kongurshan 7719 m and mustaghata 7546 m mountains are interpreted as twin crustal ramp anticlines formed en echelon on the eastern side of the karakoram fault by subduction of the tarim lithosphere under the pamir west dipping s c mylonitic gneisses that have downdip stretching lineations form the western flank of kongur mountain kinematic criteria consistently indicate a top to the west sense of shear the mylonitic foliation is cut by a steeper active normal fault which is marked by prominent triangular facets on west facing spurs the ductile normal shearing deformation occurred during the interval 5 1 ma therefore like the himalayas the pamir mountain range shows the coeval development of frontal thrusting and rear normal faulting the kongur fault thus appears to be an excellent example of synorogenic extension where normal faulting contributes to relief

glacial and interglacial patterns for asian dust transport abstract particle size distributions and depositional fluxes were investigated for present day asian dust and for the late quaternary loess palaeosol sequences from central china the regional scale transport of asian dust during interglacial stages is mainly attributable to non dust storm processes and is dominated by northwesterly surface winds conversely during glacial stages the impact of dust storms on the accumulation of loess is enhanced these regional effects are in contrast to the global dispersal of dust which is associated with transport by upper level westerly winds and is mainly the result of desert dust storms during both glacial and interglacial conditions temporal differences in the dust transport patterns to the loess plateau suggest that the variability in the coarse particle fraction 20 m during interglacial times is not directly attributable to the strong dust storms and dust fall events that have been linked to a strengthening of east asian winter monsoonal winds this is in contrast to the dust deposition rates which are strongly influenced by the monsoonal circulation

late cenozoic deformation and uplift of the ne tibetan plateau evidence from high resolution magnetostratigraphy of the guide basin qinghai province china the cenozoic intramontane gonghe guide basin in qinghai province china is tectonically controlled by the sinistral strike slip framework of the kunlun and altyn tagh south qilian faults in the northeastern tibetan plateau the basin is filled with thick cenozoic clastic sedimentary formations which provide important evidence of the deformation of this part of the plateau although they have long lacked good age constraints detailed magnetostratigraphic and paleontologic investigations of five sections in the guide basin and their lithologic and sedimentary characteristics allow us to divide a formerly undifferentiated unit the guide group into six formations where ages are now magnetostratigraphically well established they are given in parentheses the amigang 1 8 2 6 ma ganjia 2 6 3 6 ma and herjia formations 3 6 to ca 7 0 7 8 ma and the older miocene ashigong garang and guidemen formations these rocks document a generally upward coarsening sequence characterized by increasing accumulation rates increasing gravel content and sizes of its components changes of bedding dips and source rock types and marginal growth faults collectively reflect accelerated deformation and uplift of the ne tibetan plateau after 8 ma punctuated by a sharp increase in sedimentation rate at ca 3 2 ma that reflects the boulder conglomerates of the ganjia formation interestingly much of the vergence of the compressional deformation in the basin is to the south accommodated by a sequence of six thrusts f1 f6 which become active one by one progressively later toward the south undoubtedly contributing to the uplift of this part of the plateau f1 likely initiated the guide basin due to crustal flexure in the oligocene f2 was active in the early miocene f4 and f5 at ca 3 6 ma and f6 was active in the early pleistocene the detailed late miocene and younger magnetostratigraphy allows us to place much improved time constraints on the deformation and hence uplift of northeastern tibet which when compared with ages for events on other parts of the plateau provides important boundary conditions for the geodynamical evolution of tibet

late cenozoic eolian deposition in the north pacific asian drying tibetan uplift and cooling of the northern hemisphere a newly constructed record of eolian dust accumulation from the central north pacific shows that dust deposition increased by an order of magnitude quite rapidly at 3 6 ma we associate this sudden drying with the uplift of at least the northern portion of the tibetan plateau shutting off the indian ocean moisture source to central and western china this ten fold increase in atmospheric dust loading appears to be associated with the 1 m y long shift toward heavy 18o values that occurred at 3 6 2 6 ma the dust grain size record of wind intensity begins its late cenozoic coarsening a million years before the drying event at 4 5 ma the northern hemisphere cooling that results in intensification of the subpolar westerly winds may have as its ultimate cause the drawdown of atmospheric co2 in the latest miocene and the early pliocene closing of the panamanian seaway

sensitivity of east asian monsoon climate to the uplift of the tibetan plateau abstract using the cola center for ocean land atmosphere studies general circulation model a series of numerical experiments were conducted to examine the impact of uplift of the tibetan plateau on the evolution of the monsoon climate in east asia an attempt was made to isolate the effect of the plateau uplift from the changes in other forcing mechanisms we examined the spatial and temporal variation patterns of a variety of climatic variables and indices including monsoon intensity sea level pressure surface and upper air winds temperature at different levels precipitation air humidity and soil moisture our results suggest that the evolution of the east asia monsoon may be more sensitive to the uplift of the tibetan plateau than that of the south asia monsoon moreover the effect of the plateau uplift on the east asia winter monsoon is more significant than that on the summer monsoon in the northern part of east asia north china the formation of the monsoon climate is marked mainly by the establishment of the northerly winds in winter or the winter monsoon system corresponding to the uplift of the plateau when the height reaches approximately 50 of its current elevation on the other hand the establishment of the monsoon climate in the southern part of east asia the yangtze river valley and the area south of it may be much earlier than that in the northern part

neodymium isotopic variations in north pacific modern silicate sediment and the insignificance of detrital ree contributions to seawater the neodymium isotopic composition of the silicate fraction of holocene pelagic sediments from the north pacific define two provinces a central north pacific province characterized by unradiogenic and remarkably homogeneous end 10 2 0 5 and a narrow circum pacific marginal province characterized by more radiogenic and variable end 4 2 3 8 the silicate fraction in the central north pacific is exclusively eolian based on prevailing wind patterns meteorological data and neodymium isotopic data the only significant sediment source is chinese loess leaching experiments on chinese loess confirm that leachable nd is isotopically indistinguishable from bulk and residual silicate nd silicates in the circum north pacific marginal province comprise eolian loess volcanic ash and hemipelagic sediments derived from volcanic arcs a compilation of pacific seawater and mn nodule end data shows no clear spatial variation except for a general decrease from surface to deep waters from 3 to 4 and slightly lower end in bottom waters along the western north pacific due to the incursion of antarctic bottom water the relative homogeneity of bottom water end which contrasts sharply with the distinctive variation in sediment end plus the large difference between the average end of bottom waters and the central north pacific eolian silicates 4 vs 10 suggests that any contribution of ree to seawater from eolian materials is insignificant furthermore leaching of ree from eolian particles as they sink though the water column must be insignificant because nd in shallow waters is more radiogenic than nd in deeper waters that there is no contrast in the nd isotopic composition of bottom waters that overlie the central and marginal sediment provinces suggests that the ash and hemipelagic sediments derived from pacific rim volcanic arcs also contribute minimal ree to seawater the elimination of eolian ash and hemipelagic sediments leaves only near shore riverine particulates as a possibly significant particulate source of ree to seawater

acoustic tomography in the canary basin meddies and tides an acoustic propagation experiment over 308 km range conducted in the canary basin in 1997 1998 was used to assess the ability of ocean acoustic tomography to measure the flux of mediterranean water and meddies instruments on a mooring adjacent to the acoustic path measured the southwestward passage of a strong meddy in temperature salinity and current over nine months of transmissions the acoustic arrival pattern was an initial broad stochastic pulse varying in duration by 250 to 500 ms followed eight stable identified ray arrivals small scale sound speed fluctuations from mediterranean water parcels littered around the sound channel axis caused acoustic scattering internal waves contributed more modest acoustic scattering based on simulations the main effect of a meddy passing across the acoustic path is the formation of many early arriving near axis rays but these rays are thoroughly scattered by the small scale mediterranean water fluctuations a meddy decreases the deep turning ray travel times by 10 30 ms the dominant acoustic signature of a meddy is therefore the expansion of the width of the initial stochastic pulse while this signature appears inseparable from the other effects of mediterranean water in this region the acoustic time series indicates the steady passage of mediterranean water across the acoustic path tidal variations caused by the mode 1 internal tides were measured by the acoustic travel times the observed internal tides were partly predicted using a recent global model for such tides derived from satellite altimetry

formation and evolution of the badain jaran desert north china as revealed by a drill core from the desert centre and by geological survey abstract the deserts in north china are regarded as direct records of the process of inland asian aridification amongst these deserts those proximal to the chinese loess plateau clp are especially important because of their role as sediment source areas in order to investigate the formation history of the badain jaran desert the largest desert proximal to the clp a 310 m long drill core was obtained from the desert centre which reached the underlying basement rock the lithology of the core consists of an upper layer of aeolian sand with three intercalated layers of lacustrine sediments overlying alluvial fluvial deposits which are developed unconformably over red coloured basement rock a geological survey indicates that the lower red coloured basement rock is of late cretaceous age and is cut by a mesozoic erosion surface widely developed over the badain jaran area on the basis of optically stimulated luminescence and electron spin resonance dating and stratigraphic correlation a preliminary chronological framework was established which was improved by tuning the aeolian sand proportion of the drill core to earth orbital obliquity and precession this final chronology suggests that 1 the basal age of the desert strata is at least 1100 ka corresponding to the formation of the badain jaran desert and 2 that the formation of the erosion surface terminated and the surface had begun to subside by at least 1200 ka the formation of the desert can be summarized as follows the alluvial fluvial fan formed by the heihe river draining the qilian mountains provided sufficient sedimentary material to form the desert under an arid climate while the asian winter monsoon and the westerlies entrained the clastic sediments from the fan area which finally accumulated downwind more distant sediment transport was prevented by the intervening mountainous terrain these coupled processes were driven by tibetan plateau uplift and ongoing global climatic cooling after initial formation of the desert three humid phases occurred in mis 13 15 mis 5 and the holocene during which extensive lakes developed the sequential drying out of the lakes may reflect inter relationships between global climate and the intensity of the asian summer monsoon and the westerlies

evolving sources of eolian detritus on the chinese loess plateau since early miocene tectonic and climatic controls abstract the thick deposits of eolian dust on the chinese loess plateau provide a rare opportunity to explore the past changes of surface processes in response to climatic and tectonic oscillations here we report a 22 ma long nd and sr isotopic records of the eolian sources decreasing e nd values and increasing 86 sr 87 sr ratios of the eolian deposits has been observed from early miocene to about 7 ma which indicates growing material contribution from qilian mountains relative to the gobi altay mountains the source shift during 22 7 ma is interpreted to reflect the erosional response of the qilian mountains to its surface uplift between 7 ma and 1 2 ma the results show relative constant nd and sr isotopic compositions of the eolian deposits and thus suggest a constant source contribution between qilian mountains and gobi altay mountains synchronized uplift of the two mountain ranges during this period may explain the constant ratio of source contribution since 1 2 ma nd and sr isotopic records indicate that the relative debris input from qilian mountains drops rapidly as large scale topographic changes would not be expected in such a short time period the source shift since 1 2 ma might be by the differing erosional responses in qilian mountains and gobi altay mountains to the development of full glacial climate after the middle pleistocene transition this work shows that combined nd and sr isotopic signatures of the dust records are valuable proxies to monitoring past surface processes on the million years time scale

geochemistry of the xining xifeng and jixian sections loess plateau of china eolian dust provenance and paleosol evolution during the last 140 ka abstract loess and paleosol samples from three distant sections xining xifeng jixian of the chinese loess plateau were analyzed for chemical and nd sr isotopic compositions in order to obtain information about the paleoclimatic variation during the last 140 ka these three sections represent three different climatic conditions from arid in the west xining to more humid in the east jixian across the loess plateau isotopic analyses show that all the three sections display a restricted range of 143 nd 144 nd ratios or e nd 10 0 5 indicating the dominance of relatively young and uniform upper crustal sources for the eolian dust the loess and paleosol samples have typical upper crustal 87 sr 86 sr ratios 0 714 0 718 and their variation can partly be attributed to different carbonate silicate ratios in the samples ree data from the three sections are indistinguishable from each other they show typical upper crust patterns characterized by la yb n 10 and eu eu 0 65 the high degree of chemical and isotopic homogeneity suggests that the dust source region must have undergone multiple recycling and thorough sedimentary mixing processes various chemical indicators have been used to monitor the pedogenetic intensity in these sections although results for the jixian section agree reasonably well with the known climatic conditions on the loess plateau the other two sections yield results not in agreement with some well accepted proxies like magnetic susceptibility or grain size distribution some chemical proxy indicators established in our previous work on the luochuan section such as the systematic u depletion and negative ce anomalies in ree patterns in soils are not clearly recorded in the present case the discrepancy between different climatic proxies could be related to the effective soil water budget temperature as well as the rate of development of each proxy

cenozoic paleo environmental evolution of the pamir tien shan convergence zone abstract the retreat of the tethys sea and the uplift of the tibetan plateau play the critical roles in driving asian climatic changes during the cenozoic in the pamir tien shan convergence zone over 3000 m of cenozoic successions consisting of marine deposits in the lower continental clay and fine sand in the middle and molasse in the upper part record the evolution of the tethys sea the asian aridification and the deformation of the pamir in this work the existing biostratigraphic subdivisions and new electronic spinning resonance dating results were used to assign ages to formations within the ulugqat section sedimentary facies analysis and multi proxy indices were used to reconstruct the paleo environmental evolution the results show 1 the pamir tien shan convergence zone has undergone progressive environmental changes from shallow marine before 34 ma to arid land at 23 ma and finally to inter mountain basin by 5 3 ma 2 the overall increase in mean size of grains decrease in redness in magnetic susceptibility and in proportion of the ultrafine component of the sediments studied revealed a long term strengthening in potential energy to transporting medium cooling and enhanced continental aridity respectively 3 the easternmost edge of the tethys sea prevailed in the western tarim basin from late cretaceous to early cenozoic and finally retreated from this region around the eocene oligocene transition which in turn strengthened the asian aridification 4 accumulation of molasse with an upper age of 1 ma suggests that the deformation front of the pamir migrated to this area at or before that time

the sr and nd isotopic variations of the chinese loess plateau during the past 7 ma implications for the east asian winter monsoon and source areas of loess abstract 143 nd 144 nd and 87 sr 86 sr ratios of the acid insoluble residues of the red clay and overlying loess paleosols from the lingtai profile of the loess plateau china were investigated the results show that variations of the 87 sr 86 sr ratios of the lingtai profile can be divided into two stages from 7 ma b p to 2 5 ma b p the acid insoluble residues in the red clay rc formation are characterized by higher 87 sr 86 sr ratios with an average of 0 7230 from 2 5 ma b p to the present the acid insoluble residues in the wuchen loess wl4 ws1 lishi loess l15 s1 malan loess l1 and holocene loess s0 have relatively lower 87 sr 86 sr ratios and display an overall descending trend from 0 7223 at 2 5 ma b p to 0 7182 at the present among three possible interpretations for the variations of 87 sr 86 sr ratios of acid insoluble residues of the loess provenance change chemical weathering change or grain size distribution change only grain size distribution change provides a satisfactory interpretation this implies that the east asian winter monsoon strength was weak and relatively stable from 7 ma b p to 2 5 ma b p but became continuously enhanced from 2 5 ma b p to the present all the red clay and the overlying loess paleosols in the lingtai profile have generally identical e nd 0 implying that the source regions of these eolian deposits of the chinese loess plateau may be relatively stable and has not changed since 7 ma b p

uplift age and rates of the gurvan bogd system gobi altay by apatite fission track analysis abstract the dating of the uplift onset of the mongolian mountain ranges the northernmost relief associated with the india eurasia convergence is a fundamental issue to better understand the mechanisms of propagation of the cenozoic transpressive deformation in central asia using apatite fission tracks we determined the timing and strain rates of the tectonics affecting the gurvan bogd system in the gobi altay since the middle mesozoic to the late cenozoic the region was firstly affected by a lower middle jurassic tectonic phase characterized by a vertical crustal movement larger than 2 km then followed a protracted period without major crustal vertical movements until the last uplift phase the peneplanation of the jurassic relief produced an erosional surface that has undergone negligible denudation or sedimentation for more than 100 ma this same surface corresponds to the present summit plateaux of the massifs standing about 2000 m above the surrounding region which corresponds to the vertical movement produced by the ongoing uplift modelling of fission track data from the massifs of ih bogd and baga bogd shows that this uplift phase probably started at 5 3 ma the gobi altay mountain range appears therefore as one of the youngest mountain ranges in central asia which is consistent with the idea of a northward propagation of the transpressional deformation from the himalayan front to the siberian craton the cenozoic uplift rate of the massifs is estimated to be between 0 25 and 1 mm yr which is slightly higher than the upper pleistocene vertical slip rates of the bordering faults this suggests that thrust faults observed within the massifs would increase the uplift rate inside the massifs compared to the uplift rate determined at their boundaries

size frequency distributions of rocks on mars and earth analog sites implications for future landed missions the size frequency distribution of rocks at the viking landing sites and a variety of rocky locations on the earth that formed from a number of geologic processes all have the general shape of simple exponential curves which have been combined with remote sensing data and models on rock abundance to predict the frequency of boulders potentially hazardous to future mars landers and rovers rock data from the near field of the viking landers where dimensions can be measured accurately in stereo images and estimates from the far field of viking 1 have convex up curved shapes on log log graphs of cumulative frequency per square meter or cumulative fractional area versus diameter the rock data show a sharp drop off at large diameters and a progressive approach to a plateau with decreasing diameter approaching the total rock coverage which can be fit well with simple exponential functions similar shaped size frequency distributions of rocks are found at a wide variety of rocky surfaces on the earth and can be fit well with simple exponential functions this distribution is compatible with fracture and fragmentation theory which provides a physical basis for its wide application a combined fit to rock area data at both viking sites was made with a general exponential function in which the pre exponential is the total area covered by rocks simple linear height versus diameter relationships were also derived from height diameter ratios at the viking sites which suggest that rockier areas on mars have higher standing rocks than less rocky areas height was then substituted into the general exponential function derived for diameter yielding the cumulative fractional area of rocks versus height for any given total rock coverage on mars results indicate that most of mars is rather benign with regard to hazards from landing on large rocks for total rock coverage of 8 equivalent to modal rock coverage on mars and the viking 1 site without the outcrops about 1 of the surface is covered by 20 cm or higher rocks a lander designed to accommodate landing on 0 5 m high boulders such as the mars pathfinder airbag system could land on a surface covered by about 20 rocks similar to the viking 2 site which is rockier than 95 of the planet with 1 of the surface covered by rocks of 0 5 m or higher

nd and sr isotopic characteristics of chinese deserts implications for the provenances of asian dust silicate nd sr isotopes of the fine grained fractions of the 10 major deserts and sandy lands in north china and the loess in chinese loess plateau were systematically investigated wide ranges in nd sr isotopic compositions have been observed the results of the 7 0 b the deserts on the northern margin of tibetan plateau with end 0 ranging from 11 9 to 7 4 and c the deserts on the ordos plateau with the lowest end 0 11 5 the distribution of the threes isotopic regions is controlled by the tectonic setting in north china which implies that the materials of the deserts are derived from the locally eroded rocks from the surrounding mountains and the nd sr isotopic signatures of these deserts could be quit stable over the past million years on the sub tectonic time scales if there is any desert at those times the nd sr isotopic compositions of the loess are mostly close to those of the deserts in isotopic region b suggesting that the main source regions of the last glacial loess in the chinese loess plateau are badain jaran desert tengger desert and qaidam desert also the comparison between the nd sr isotopes of the 5 lm silicate fractions of the deserts and the ancient dust falls in the north pacific and greenland show that the asian end members of these dust falls are derived most from the deserts in the isotopic region b and less from those in the isotopic region c

late miocene quaternary rapid stepwise uplift of the ne tibetan plateau and its effects on climatic and environmental changes abstract the way in which the ne tibetan plateau uplifted and its impact on climatic change are crucial to understanding the evolution of the tibetan plateau and the development of the present geomorphology and climate of central and east asia this paper is not a comprehensive review of current thinking but instead synthesises our past decades of work together with a number of new findings the dating of late cenozoic basin sediments and the tectonic geomorphology of the ne tibetan plateau demonstrates that the rapid persistent rise of this plateau began 8 1 ma followed by stepwise accelerated rise at 3 6 ma 2 6 ma 1 8 1 7 ma 1 2 0 6 ma and 0 15 ma the yellow river basin developed at 1 7 ma and evolved to its present pattern through stepwise backward expansion toward its source area in response to the stepwise uplift of the plateau high resolution multi climatic proxy records from the basins and terrace sediments indicate a persistent stepwise accelerated enhancement of the east asian winter monsoon and drying of the asian interior coupled with the episodic tectonic uplift since 8 ma and later also with the global cooling since 3 2 ma suggesting a major role for tectonic forcing of the cooling

nd sr isotope geochemistry of fine grained sands in the basin type deserts west china implications for the source mechanism and atmospheric transport abstract the basin type deserts of west china are among the greatest dust emission areas in the world mineral dust that is emitted from the deserts is transported and deposited in east central china and even in far east regions this study investigates the nd sr isotopic compositions of fine grained surface sands nd 0 10 9 to 15 and 87 sr 86 sr 0 714 to 0 718 while those of the dune sands from the gurbantunggut desert range from e nd 0 4 5 to 6 and 87 sr 86 sr 0 711 to 0 713 the isotopic compositions of the fine grained surface sands are not spatially uniform within each desert and are controlled by the lithological characteristics of the tectonic units in which the deserts are located the isotopic comparison of the dune sands with other sediments indicates that tectonic denudation and fluvial processes are the main mechanisms of fine particle production of the modern desert sands in terms of isotope analyses and forward trajectory results it is further found that the mineral dust is deposited not only in proximal areas such as the hexi corridor the chinese loess plateau and the tibet qinghai plateau but also in distal regions such as japan the pacific ocean and greenland once it is blown out of the taklimakan desert however the transport and sinks of mineral dust vary with the atmospheric currents

an astronomically tuned 8 1 ma eolian record from the chinese loess plateau and its implication on the evolution of asian monsoon the chinese loess paleosol sequences have led to a great understanding of the evolution of the east asian monsoon eam in the quaternary however evolution of the eam in the late miocene and pliocene is quite blurry hindering our understanding of the mechanisms driving the eam thus we obtained high resolution grain size records of 8 1 ma from the thickest eolian red clay sequence at chaona on the chinese central loess plateau and astronomically tuned the grain size records to the orbital variation with a time resolution of 1 5 ka to 5 8 ka the variability of coarse size fraction a recognized proxy for the east asian winter monsoon eawm indicates a persistent but stepwise intensification of the eawm at ca 5 5 ma 3 6 ma 2 6 ma and 1 ma filtering of this proxy record at 100 41 and 21 ka bands was conducted to trace the evolution of the eawm in a frequency domain over 8 1 ma temporal variations of these three cycles show a remarkable simultaneous enhancement at ca 5 5 ma indicating a synchronous intensification of high and low latitude signals in the eawm record we suggest that the closure of panama seaway to form the north atlantic thermohaline circulation and the high latitude cooling during this time might collectively trigger such a response copyright 2011 by the american geophysical union

the impact of regional uplift of the tibetan plateau on the asian monsoon climate abstract the climatic effect of tibetan plateau tp uplift is a hot topic in paleoclimate research in this paper the results of a set of numerical simulations are reported to analyze the impact of regional tp uplift on the asian monsoon climate the focus is on the impact of the regional uplift in the west and east parts on south asian summer monsoon as well as the impact of regional uplift on east asian winter monsoon the results show that the uplifts of the himalaya and the central southern tp have little effect on summer precipitation increasing over south asia whereas the further uplifts of the tp in the west and east parts including the uplifts of both the eastern and western tp have important effects on the strengthening of the south asian summer monsoon the uplift of the eastern tp leads to low level cyclonic circulation anomalies appearing in the bay of bengal accompanied by anomalous upward movement and in turn precipitation markedly increases in the bay of bengal whereas the uplift of the western tp produces low level cyclonic circulation anomalies around the uplifted region and intensifies the moisture transport from the tropical ocean and thus precipitation further increases in south asia especially in the northern arabian sea the strengthened summer monsoon in south asia is coupled with the intensification in diabatic heating and moisture convergence for the east asian winter monsoon the intensification of winter monsoon winds is related more to the regional uplifts than the uplift of the whole tp the uplifts of the central southern tp the northern tp and other northern topography have greater effects on the strengthening of the winter monsoon winds

pliocene warmth polar amplification and stepped pleistocene cooling recorded in ne arctic russia understanding the evolution of arctic polar climate from the protracted warmth of the middle pliocene into the earliest glacial cycles in the northern hemisphere has been hindered by the lack of co

reconstruction of glaciation over the past 6 myr from ice borne deposits in the norwegian sea it is well known that a significant intensification of northern hemisphere glaciation occurred 2 5 myr ago in contrast to the much earlier onset 35 myr of glaciation in antarctica1 3 much less is known about the behaviour of the climate before 2 5 myr and it has remained unclear when sizeable glaciers first started to develop in the northern hemisphere here we deduce the history of high northern latitude glaciation over the past 6 myr from records of ice borne deposits in deep sea sediments of the norwegian sea we find that glaciers large enough to reach sea level were present in the norwegian sea area as early as 5 5 myr three million years before the intensification of glaciation at 2 5 myr fluctuations in ice volume can be deduced from the oxygen isotope record but this provides only a global average which may not reflect the history of ice sheet growth in specific regions from a comparison of the oxygen isotope records with the record of ice rafted material we derive an estimate of the relative contributions of southern and northern hemisphere glaciation to global variations in ice volume

increasing nd isotopic ratio of asian dust indicates progressive uplift of the north tibetan plateau since the middle miocene the time and rate of tibetan uplift is critical in understanding both the geodynamics of plateau growth and the influence of mountain building on climate change models predict that the uplift of the north tibetan plateau ntp occurred later than uplift of the south and central tibetan plateau uplift of the ntp is believed to have initiated the aridity in the interior of asia and to have critically affected the evolution of asian monsoon and ultimately global climate the history of ntp uplift has remained uncertain however scenarios range from early miocene to the past million years this work provides new evidence by relating the nd isotopic evolution of asian dust to ntp uplift the sources of the asian dust are located in the arid lands between the ntp and the central asia orogen mass balance calculations indicate that the decreasing e nd values from 8 2 to 10 4 for pacific dust since 15 ma reflects increasing relative contribution of ntp materials 40 to 70 to the dust source as paleoelevation in the central asia orogen has largely remained constant the increasing relative ntp detritus contribution is interpreted to reflect the progressive surface uplift of the ntp at a rate of at least 0 12 mm yr 1 since 15 ma

grain size distribution function of polymodal sediments in hydraulic and aeolian environments and numerical partitioning of the sedimentary components most continental sediments are polymodal composed of overlapping components of which the grain size generally obeys some type of natural distribution the grain size components and their function types can be determined from frequency and cumulative curve plots in order to define the function formula of the grain size distribution the function parameters can be estimated by fitting a defined function formula to the measured grain size data of the sample which simultaneously achieves numerical partitioning of the sedimentary components genetic analysis of grain size components of hydraulic and aeolian sediments demonstrates the following environmental implications fluvial sediment is composed of isolated saltation and suspension components the sediments in closed lake basins are dominated by a suspension silt clay component with a small proportion of saltation sand the fine sand component makes up the majority of desert sand overlapping with a small proportion of fine dust aeolian loess is composed of two overlapping components a short suspension time silt component and a long suspension time fine component aeolian material in the north pacific deep sea sediments is dominated by long suspension time fine dust the fine component in aeolian sediments shows a consistent grain size distribution and genetic connection from the desert sand loess of northern china to the north pacific ocean which is mainly transported by westerly winds and is dispersed in the atmosphere forming a background dust c 2002 elsevier science b v all rights reserved

significantly warmer arctic surface temperatures during the pliocene indicated by multiple independent proxies temperatures in the arctic have increased by an astounding 1 c in response to anthropogenic forcing over the past 20 years and are expected to rise further in the coming decades the pliocene 2 6 5 3 ma is of particular interest as an analog for future warming because global temperatures were signifi cantly warmer than today for a sustained period of time with continental confi gurations similar to present here we estimate mean annual temperature mat based upon three independent proxies from an early pliocene peat deposit in the canadian high arctic our proxies including oxygen isotopes and annual ring widths mat 0 5 1 9 c coexistence of paleovegetation mat 0 4 4 1 c and bacterial tetraether composition in paleosols mat 0 6 5 0 c yield estimates that are statistically indistinguishable the consensus among these proxies suggests that arctic temperatures were 19 c warmer during the pliocene than at present while atmospheric co 2 concentrations were 390 ppmv these elevated arctic pliocene temperatures result in a greatly reduced and asymmetrical latitudinal temperature gradient that is probably the result of increased poleward heat transport and decreased albedo these results indicate that arctic temperatures may be exceedingly sensitive to anthropogenic co 2 emissions

magnetostratigraphic data on neogene growth folding in the foreland basin of the southern tianshan mountains the tianshan range is one of the longest and highest mountain belts in central asia stretching east west for 2500 km uplift of this late paleozoic orogenic belt resulted from intracontinental deformation caused by the collision of the indian and eurasian plates during the cenozoic era to constrain the timing of cenozoic tectonic deformation of the tianshan range we analyzed the magnetostratigraphy of 3780 m thick neogene deposits from the kuqa foreland basin of southern tianshan the geometry measurements and magnetic fabric data show that syntectonic growth strata began to accumulate at 6 5 ma ago indicating that crustal shortening initiated in the latest miocene the increase in sedimentation rate and an abrupt change of the magnetic fabric parameters also occurred at 6 5 ma accompanied by onset of syntectonic growth strata the latest miocene crustal shortening is a signifi cant tectonic event in the foreland basin of the southern tianshan range in response to the india eurasia collision