cenozoic topographic and climatic response to changing tectonic boundary conditions in western north america abstract this study presents an oxygen isotopic record from the paleocene to the pliocene based on the analysis of predominantly paleosol carbonate from intermontane basins in southwestern montana and eastern idaho 18 o values of calcite decrease by 7 to 10 between 50 and 47 ma in southwestern montana and idaho most likely as a result of an increase in elevation of 2 5 to 3 5 km this rise in elevation is roughly contemporaneous with the emplacement of the nearby challis volcanics and the formation of metamorphic core complexes in the hinterland of the sevier thrust belt moreover when compared to previous oxygen isotopic studies that show oxygen isotopic shifts of similar magnitude occurring later in the late eocene to early oligocene in northeastern nevada and late oligocene to miocene in southern nevada the results of this study add to a growing body of evidence for a spatial and temporal migration of high surface elevations from north to south in the great basin of western united states this surface uplift history supports tectonic models calling for north to south removal of the farallon slab or delamination of the mantle lithosphere

ice moraine and landslide dams in mountainous terrain we review recent work on ice moraine and landslide dams in mountainous terrain thus complementing several comprehensive summaries on glacier dams in intracontinental and arctic areas of low relief we discuss the roles of tectonic and climatic forcing on ice moraine and landslide dam formation and sudden drainage and focus on similarities and differences between their geomorphic impacts on confined valleys drained by steep bedrock and gravel bed rivers despite numerous reported failures of natural dams in mountain belts throughout the world their relevance to long term dynamics of mountain rivers remains poorly quantified all types of dams exert local base level controls thus trapping incoming sediment and inhibiting fluvial bedrock incision pervasive geomorphic and sedimentary evidence of outburst events is preserved even in areas of high erosion rates suggesting that sudden dam failures are characterized by processes of catastrophic valley floor aggradation active channel widening and downstream dispersion of sediment during which little bedrock erosion seems to be achieved we find that in the absence of direct evidence of former dams a number of similarities among the geomorphic and sedimentologic characteristics of catastrophic outburst flows may give rise to ambiguous inferences on the dam forming process this is especially the case for tectonically active mountain belts where there is ample and comparable potential for the formation and failure of ice moraine landslide and polygenetic dams concomitant with climatic oscillations or earthquake disturbance hence the palaeoclimatic implications of erroneously inferring the cause of dam formation may be significant we recommend that future research on natural dams in mountainous terrain addresses a climate and earthquake controlled systematics in the pattern of formation and failure b quantification of response of mountain rivers to catastrophic outburst events and their concomitant process sequences c elaboration of a comprehensive classification of natural dams in mountainous terrain with special attention to polygenetic dams d physical based modelling of dam formation failure and routing of water and sediment outbursts and e quantitative controls on the contribution of natural dams to sediment budgets in mountainous terrain

quaternary glaciation of the himalayan tibetan orogen glacial geological evidence from throughout the himalayan tibetan orogen is examined to determine the timing and extent of late quaternary glaciation in this region and its relation to similar changes on a global scale the evidence summarised here supports the existence of expanded ice caps and extensive valley glacier systems throughout the region during the late quaternary however it cannot yet be determined whether the timing of the extent of maximum glaciation was synchronous throughout the entire region or whether the response was more varied the lack of organic material needed for radiocarbon dating has hindered past progress in glacial reconstruction however application of optically stimulated luminescence and terrestrial cosmogenic radionuclide methods has recently expanded the number of chronologies throughout the region limits to the precision and accuracy available with these methods and more importantly geological uncertainty imposed by processes of moraine formation and alteration both conspire to limit the time resolution on which correlations can be made to milankovitch timescales several ka in order to put all studies on a common scale well dated sites have been re evaluated and all the published terrestrial cosmogenic nuclide ages for moraine boulders and glacially eroded surfaces in the himalayan tibetan orogen have been recalculated locally detailed studies indicate that there are considerable variations in the extent of glaciation from one region to the next during a glaciation glaciers throughout monsoon influenced tibet the himalaya and the transhimalaya are likely synchronous both with climate change resulting from oscillations in the south asian monsoon and with northern hemisphere cooling cycles in contrast glaciers in pamir in the far western regions of the himalayan tibet orogen advanced asynchronously relative to the other regions that are monsoon influenced regions and appear to be mainly in phase with the northern hemisphere cooling cycles broad patterns of local and regional variability based on equilibrium line altitudes have yet to be fully assessed but have the potential to help define changes in climatic gradients over time copyright 2008 john wiley sons ltd

paleobotanical evidence for near present day levels of atmospheric co2 during part of the tertiary understanding the link between the greenhouse gas carbon dioxide co 2 and earth9s temperature underpins much of paleoclimatology and our predictions of future global warming here we use the inverse relationship between leaf stomatal indices and the partial pressure of co 2 in modern ginkgo biloba and metasequoia glyptostroboides to develop a co 2 reconstruction based on fossil ginkgo and metasequoia cuticles for the middle paleocene to early eocene and middle miocene our reconstruction indicates that co 2 remained between 300 and 450 parts per million by volume for these intervals with the exception of a single high estimate near the paleocene eocene boundary these results suggest that factors in addition to co 2 are required to explain these past intervals of global warmth

cosmic ray labeling of erosion surfaces in situ nuclide production rates and erosion models a number of in situ cosmogenic radionuclides and stable nuclides have been measured in natural exposed rock surfaces with a view to study their in situ production and rock erosion rates 1 the in situ radionuclides can be used for a high resolution tomography of the erosional history of an exposed surface two stable nuclides 3he 21ne and five radionuclides 10be 26al 36cl 14c 39ar having half lives in the range of 300 1 5 106 yr half life are measurable in many rock types a prerequisite for the application of the in situ nuclides for the study of erosional histories of surfaces is a knowledge of their production rates under different irradiation conditions altitude latitude irradiation geometry and shielding relative nuclide production rates can be determined fairly accurately using the extensive available data on cosmic ray neutrons 2 absolute nuclide production rates cannot generally be predicted with any accuracy because of lack of data on excitation functions of nuclides unless some normalization is possible as was done in the case of several cosmic ray produced isotopes in the atmosphere 3 based on a recent natural calibration experiment in which erosion free surfaces exposed to cosmic radiation for 11 000 yrs were sampled the absolute production rates of 10be and 26al in quartz have been accurately estimated for mountain altitudes in sierra nevada 4 the absolute production rates of 10be and 26al in quartz can therefore be estimated fairly accurately for any given latitude and altitude some measurements of 14c in rocks of low erosion rate 5 similarly allow an estimate of its production rate attempts made to measure the in situ production rates of 3he in rocks have not yet led to a convergent production rate in view of the importance of knowing the production rates of isotopes of he ne and ar i present here theoretical estimates of their production rates based on available cross section data i discuss the information that can be extracted from the study of the in situ nuclides in rocks useful parameters characterizing the exposure history of a rock surface are 1 the effective surface exposure age and 2 the time averaged erosion rate the implications of these parameters for single and multiple nuclide studies are discussed in terms of the erosion models considered

pedogenic carbonate proxies for amount and seasonality of precipitation in paleosols the depth to carbonate nodular bk horizon in soils d in cm is correlated with mean annual precipitation p in mm so that bk horizons are deep in subhumid regions but shallow in semiarid regions previous quantifications of this relationship are unchanged by this new compilation of 807 soils p 137 24 6 45 d 0 013 d 2 where r 2 0 52 and standard error s e 147 mm in most north american postglacial soils the bk horizon is thin and well defined whereas in monsoonal tropical soils of pakistan and kenya the bk horizon is thick and diffuse data from 675 modern soils define the relationship between the thickness of soil with nodules t in cm and mean annual range of precipitation m in mm difference between monthly means of wettest and driest months m 0 79 t 13 71 where r 2 0 58 and s e 22 mm the relationship between carbonate nodule size s in cm and soil age a in ka is quantified by 9 radiocarbon dated soils from las cruces new mexico a 3 92 s 0 34 where r 2 0 57 and s e 1 8 k y these transfer functions are applied to reconstructing paleoclimatic change from paleocene eocene paleosols of the north horn formation and flagstaff limestone of axhandle canyon utah the terminal paleocene spike of warmth recorded by fossil plants in nearby wyoming was coincident with a brief peak in both mean annual precipitation and mean annual range of precipitation in utah

luminescence dating of glacial deposits near the eastern himalayan syntaxis using different grain size fractions abstract numerical dating of glacial deposits is important for understanding quaternary glacial evolution optically stimulated luminescence osl dating is one of the techniques widely used on such sediments owing to the short distances traveled before deposition the incomplete bleaching of luminescence signals in glacial sediments may introduce serious dating problems vis a vis glacial and any associated sediments here we report a comparison of osl ages obtained from the fine 4 11 m and medium 38 63 m grain size fractions of quartz extracted from glaciofluvial sediments and from glacial tills in the basongcuo catchment near the eastern himalayan syntaxis initially four glacial stages were identified based on field observations of moraine distribution and geomorpho stratigraphic relations a total of 39 osl samples were then collected from glaciofluvial sand layers or lenses and from till quartz grains in the fine 4 11 m and medium 38 63 m size fractions were extracted from each sample and dated using the single aliquot regeneration sar protocol the modern supraglacial sediment sample was dated to 0 2 fine grain to 0 7 medium grain ka suggesting that the sediment was not completely bleached on deposition contrary to previous experience suggesting that coarse grains are usually better bleached than fine grains prior to deposition our results show that estimated osl ages for fine grains are generally younger than those for medium grains this suggests that the two fractions may have come from different sources and thus have different bleaching histories and that fine grained quartz may be more suitable for osl dating of these materials applying the minimum age model to data from medium grained quartz yields ages close to those obtained from fine grained quartz suggesting that both can be used for dating glacial advances the osl dates suggest that glaciers in the studied area advanced at 0 1 1 3 ka 7 5 ka and 11 13 ka and were furthest advanced between 16 and 30 ka the timing of the local last glacial maximum lgm is broadly consistent throughout the eastern and central himalaya and frequent glacial advances after the lgm all suggest that glaciers in the humid eastern himalayan syntaxis are sensitive to global cooling

recent climatic significance of chemical signals in a shallow firn core from an alpine glacier in the south asia monsoon region abstract there are 19 sub tropical temperate glaciers on mount yulong the southernmost currently glacier covered area in eurasia controlled by the south western monsoon climate in the summer of 1999 a firn core 10 10 m long extending down to glacier ice was recovered in the accumulation area of the largest glacier baishui no 1 periodic variations of climatic signals above 7 8 m depth were apparent and net accumulation of four years was identified by the annual oscillations of isotopic and ionic composition the boundaries of annual accumulation were confirmed by higher values of electrical conductivity and ph and by dirty refreezing ice layers at the levels of summer surfaces calculated mean annual net accumulation from 1994 95 to 1997 98 was about 900 mm water equivalent the amplitude of isotopic variations in the profile decreased with increasing depth and isotopic homogenization occurred below 7 8 m as a result of meltwater percolation variations of 18 o above 7 8 m showed an approximate correlation with the winter climatic trend at lijiang station 25 km away concentrations of ca 2 and mg 2 were much higher than those of na and k indicating that the air masses for precipitation were mainly from a continental source and that the core material accumulated during the winter period the close correspondence of cl and na indicated their common origin the decreasing trend of na cl ratios with increasing depth further reflects a progressive homogenization process caused by meltwater percolation concentrations of so 4 2 and no 3 in the core are quite low the mean annual net accumulation in the core and the estimated ablation indicate that the average annual precipitation above the glacier s equilibrium line is 2400 3100 mm but this needs to be confirmed by long term observation of mass balance

latest pleistocene and holocene glacier fluctuations in the himalaya and tibet abstract the timing and extent of latest pleistocene and holocene alpine glacier fluctuations in the himalaya and tibet are poorly defined due to the logistical and political inaccessibility of the region and the general lack of modern studies of the glacial successions nevertheless renewed interest in the region and the aid of newly developing numerical dating techniques have provided new insights into the nature of latest pleistocene and holocene glacier oscillations these studies provide abundant evidence for significant glacial advances throughout the last glacial cycle in most high himalayan and tibetan regions glaciers reached their maximum extent early in the last glacial cycle however true last glacial maximum glacier advances were significantly less extensive notable glacier advances occurred during the lateglacial and the early holocene with minor advances in some regions during the mid holocene there is abundant evidence for multiple glacial advances throughout the latter part of the holocene although these are generally very poorly defined and were less extensive than the early holocene glacier advances the poor chronological control on latest pleistocene and holocene glacial successions makes it difficult to construct correlations across the region and with other glaciated regions in the world which in turn makes it hard to assess the relative importance of the different climatic mechanisms that force glaciation in this region the lateglacial and holocene glacial record however is particularly well preserved in several regions notably in muztag ata and kongur and the khumbu himal these successions have the potential to be examined in detail using newly developing numerical dating methods to derive a high resolution record of glaciation to help in paleoclimatic reconstruction and understanding the dynamics of climate and glaciation in the himalaya and tibet

fukushima derived radionuclides in the ocean and biota off japan the t hoku earthquake and tsunami of march 11 2011 resulted in unprecedented radioactivity releases from the fukushima dai ichi nuclear power plants to the northwest pacific ocean results are presented here from an international study of radionuclide contaminants in surface and subsurface waters as well as in zooplankton and fish off japan in june 2011 a major finding is detection of fukushima derived 134cs and 137cs throughout waters 30 600 km offshore with the highest activities associated with near shore eddies and the kuroshio current acting as a southern boundary for transport fukushima derived cs isotopes were also detected in zooplankton and mesopelagic fish and unique to this study we also find 110mag in zooplankton vertical profiles are used to calculate a total inventory of 2 pbq 137cs in an ocean area of 150 000 km2 our results can only be understood in the context of our drifter data and an oceanographic model that shows rapid advection of contaminants further out in the pacific importantly our data are consistent with higher estimates of the magnitude of fukushima fallout and direct releases stohl et al 2011 atmos chem phys discuss 11 28319 28394 bailly du bois et al 2011 j environ radioact 10 1016 j jenvrad 2011 11 015 we address risks to public health and marine biota by showing that though cs isotopes are elevated 10 1 000 over prior levels in waters off japan radiation risks due to these radionuclides are below those generally considered harmful to marine animals and human consumers and even below those from naturally occurring radionuclides

paleoglaciation of the tibetan plateau and surrounding mountains based on exposure ages and ela depression estimates the tibetan plateau holds an ample record of past glaciations and there is an extensive set of glacial deposits dated by exposure dating here a compilation is presented of 10be exposure ages from 485 glacial deposits with 1855 individual samples on the tibetan plateau and ela depression estimates for the glacial deposits based on a simple toe to headwall ratio approach to recalculate the tibetan plateau exposure ages 10be production rates from 24 calibration sites across the world are compiled and recalibrated yielding an updated global reference 10be production rate the recalculated exposure ages from the tibetan plateau glacial deposits are then divided into three groups based on exposure age clustering to discriminate good well clustered from poor scattered deglaciation ages a major part of the glacial deposits have exposure ages affected by prior or incomplete exposure complicating exposure age interpretations the well clustered deglaciation ages are primarily from mountain ranges along the margins of the tibetan plateau with a main peak between 10 and 30 ka indicating glacial advances during the global lgm a large number of deglaciation ages older than 30 ka indicates maximum glaciation predating the lgm but the exposure age scatter generally prohibits accurate definition of the glacial chronology the ela depression estimates scatter significantly but the main part is remarkably low average ela depressions of 337 197 m for the lgm and 494 280 m for the pre lgm indicate restricted glacier expansion

influence of secular variation of the geomagnetic field on production rates of in situ produced cosmogenic nuclides abstract scaling factors are presented that allow a full description of the cosmic ray flux modulation during secular variation of the geomagnetic field these scaling factors are analogous to those determined in a similar work dunai t j earth planet sci lett 2000 176 157 169 that were accurate for field strengths equivalent to present day field strength but cannot accommodate field strength variations strategies to derive the relevant geomagnetic field parameters are discussed and are tested with existing production rate calibrations for 3 he a production rate of 103 4 2 atoms g olivine yr sea level and for zero cutoff rigidity was derived from calibration sites from hawaii western usa and canary islands covering the time range of 2 281 kyr

cosmogenic nuclide burial ages and provenance of the xigeda paleo lake implications for evolution of the middle yangtze river abstract hundred meter thick lacustrine sediments are widespread along the middle yangtze river the distribution of these sediments suggests that an event blocked the river forming a lake stretching 160 km from east to west and 110 km north to south with a depth of 500 m using the cosmogenic nuclides 10 be and 26 al we have dated the time of burial of the lacustrine sediments and fluvial gravels beneath the sediments our results indicate a deposition age for these sediments between 1 34 and 1 58 ma studies of zircon u pb age distributions within lacustrine sediments and fluvial sands related to the paleo lake formation show diverse provenances from the upper yangtze river and yalong river a major tributary of the yangtze river these deposits contain geologic fingerprints that allow identification of the source region of the lacustrine deposits and fluvial sands our results support the reversal of the middle yangtze river before the paleo lake formation we hypothesize that the geologic event that dammed the originally southward flow was the lateral movement of chenghai fault in the dali fault system initiated in early quaternary water eventually cut through the spillway and flowed to the east

the earthquake triggered rock avalanche of cui hua qin ling mountains p r of china the benefits of a lake damming prehistoric natural disaster abstract this paper deals with an investigation of cui hua rock avalanche in the qin ling mountains in the dong cha valley an eastern branch of taiyi river some 30 km south of xi an province of shaanxi p r of china the landslide originated on lithotectonic structures along seismic active fault systems its occurrence could be correlated with an earthquake in 780 bc that must have triggered the landslide due to a stabilizing human input the landslide area in front of the dammed tianchi lake became an area of settlement for native people of this area which used this rapidly geomorphologic changing system for their needs over the past 2780 years nowadays the lake is considered to be a reservoir for drinking water agriculture and a hydropower plant even more the deposit of the cui hua rock avalanche has become a touristic place for sightseeing and vacation

the formation and failure of natural dams of the numerous kinds of dams that form by natural processes dams formed from landslides glacial ice and late neoglacial moraines present the greatest threat to people and property landslide dams form in a wide range of physiographic settings the most common types of mass movements that form landslide dams are rock and debris avalanches rock and soil slumps and slides and mud debris and earth flows the most common initiation mechanisms for dam forming landslides are excessive rainfall and snowmelt and earthquakes landslide dams can be classified into six categories based on their relation with the valley floor type i dams 11 of 184 landslide dams from around the world that we were able to classify do not reach from one valley side to the other type ii dams 44 span the entire valley floor in some cases depositing material high on opposite valley sides type iii dams 41 move considerable distances both upstream and downstream from the landslide failure type iv dams 1 are rare and involve the contemporaneous failure of material from both sides of a valley type v dams 1 also are rare and are created when a single landslide sends multiple tongues of debris into a valley and forms two or more landslide dams in the same reach of river type vi dams 3 involve one or more failure surfaces that extend under the stream or valley and emerge on the opposite valley side many landslide dams fail shortly after formation in our sample of 73 documented landslide dam failures 27 of the landslide dams failed less than 1 day after formation and about 50 failed within 10 days over topping is by far the most common cause of failure the timing of failure and the magnitude of the resulting floods are controlled by dam size and geometry material characteristics of the blockage rate of inflow to the impoundment size and depth of the impoundment bedrock control of flow and engineering controls such as artificial spill ways diversions tunnels and planned breaching by blasting or conventional excavation glacial ice dams can produce at least nine kinds of ice dammed lakes the most dangerous are lakes formed in main valleys dammed by tributary glaciers failure can occur by erosion of a drainage tunnel under or through the ice dam or by a channel over the ice dam cold polar ice dams generally drain supraglacially or marginally by downmelting of an outlet channel warmer temperate ice dams tend to fail by sudden englacial or subglacial breaching and drainage late neoglacial moraine dammed lakes are located in steep mountain areas affected by the advances and retreats of valley glaciers in the last several centuries these late neoglacial dams pose hazards because 1 they are sufficiently young that vegetation has not stabilized their slopes 2 many dam faces are steeper than the angle of repose 3 these dams and lakes are immediately downslope from steep crevassed glaciers and near vertical rock slopes and 4 downstream from these dams are steep canyons with easily erodible materials that can be incorporated in the flow and increase flood peaks the most common reported failure mechanism is overtopping and breaching by a wave or series of waves in the lake generated by icefalls rockfalls or snow or rock avalanches melting of ice cores or frozen ground and piping and seepage are other possible failure mechanisms natural dams may cause upstream flooding as the lake rises and downstream flooding as a result of failure of the dam although data are few for the same potential energy at the dam site ownstream flood peaks from the failure of glacier ice dams are smaller than those from landslide moraine and structed earth fill and rock fill dam failures moraine dam failures appear to produce some of the largest downstream flood peaks for potential energy at the dam site greater than 1011 1012 joules differences in flood peaks natural dam failures appear to be controlled by dam characteristics and failure mechanisms

provenance and time constraints on the formation of the first bend of the yangtze river 1 the upper yangtze river flows southward on the southeastern tibet characterizing by uniquely low and continuous relief the river makes a sharp turn at shigu heading northeast and forms the first bend of the yangtze river many previous studies assumed southward flow of the ancestral yangtze river from shigu to the south china sea however field evidence of southward flow of the paleo yangtze is lacking in this paper we report our identification based on detrital zircon u pb age distributions of a range of fluvial sands left by the paleo yangtze in tongdian madeng and nanjian basins cosmogenic10be and 26al burial dating provides burial ages for these fluvial sands from 1 7 to over 8 7 ma rerouting of the yangtze river therefore occurred within the last 1 7 ma postdating the major uplift of the central tibet we attribute the rerouting of the yangtze river to response to activation of the dali fault system and in a larger scale initiation of crustal deformation by clockwise rotation around eastern himalayan syntaxis 2 4 ma ago reorganization of the yangtze drainage pattern most likely reflects regional uplift and displacement due to lower crust flowing beneath major faults in the southeastern tibet and yunnan

cosmogenic beryllium 10 and neon 21 dating of late pleistocene glaciations in nyalam monsoonal himalayas we present cosmogenic 10be and 21ne chronologies from 21 erratic boulders on three moraine sequences in nyalam county monsoonal himalayas southern margin of the tibetan plateau the surface exposure ages provide evidence for at least two distinct glacial advances during the late stage of the last glacial cycle and for one or more significantly older glaciations the distribution of cosmogenic ages from the three ridges of the old moraine sequence is inconsistent with their stratigraphic order because exposure periods of the erratics prior to deposition on the moraine surface is shown to be small the chronology stratigraphy mismatch suggests that the cosmogenic ages do not date moraine deposition but most likely significant moraine ridge denudation and related boulder exhumation after initial deposition of the moraines during the penultimate glacial cycle or earlier the surface exposure ages based on various currently accepted production rate scaling protocols yield age differences of up to 35 reflecting the poor knowledge of terrestrial cosmogenic production rates at low latitude high altitude sites even within this conservative uncertainty range our results do not yield evidence for late pleistocene glaciations in monsoonal tibet to be asynchronous to those in mid latitudes on both hemispheres there is an urgent need to improve the knowledge of terrestrial cosmogenic nuclide production rates and their scaling to low latitude regions to fully exploit the climate information archived in tropical moraine sequences

plutonium in the western north pacific transport along the kuroshio and implication for the impact of fukushima daiichi nuclear power plant accident abstract this study examined pu source terms in the western north pacific wnp based on data collected in 2014 and 2015 the basin wide 240pu 239pu atom ratios ranged from 0 227 to 0 263 with an average value of 0 244 0 011 consistently higher than that of global fallout 0 180 the spatial distribution of 240pu 239pu atom ratios showed higher values within the kuroshio region the main western ocean boundary current as compared to the zone off of the kuroshio there was also an overall decreasing trend of 240pu 239pu along the kuroshio path to its extensions 239 240pu activities in surface seawater exhibited a wide range from 1 15 to 4 30 mbq m 3 and their spatial distribution showed an increasing trend with latitude unlike the 240pu 239pu atom ratios which had heavier isotopic compositions in the kuroshio mainstream compared to the zone off of the kuroshio the 239 240pu activities were higher outside the kuroshio than within the kuroshio these patterns in both pu isotopic ratios and activities point towards a unique close in fallout source which levels down in its source term and has a high degree of scavenging during its transport along the kuroshio and can be traced back to a precursor the north equatorial current which originates near the pacific proving grounds ppg with characteristically higher 240pu 239pu atom ratios high 240pu 239pu atom ratios found in the zone outside the kuroshio were transported from the kuroshio via the formation and circulation of north pacific intermediate water we further revealed using a simple two end member mixing model that the ppg source contributed 60 13 of the pu in the kuroshio zone and 45 10 in the zone off of the kuroshio both the comparison of pu isotopic composition in the wnp within a radius of 500 km or 1000 km off the fukushima daiichi nuclear power plant fdnpp between prior to and post the accident and a simple first order mass balance calculation in terms of atmospheric deposition and release suggest that the pu originating from the fdnpp accident if any was either negligible or the input flux of 239 240pu was too small to significantly alter the pu isotopic composition in the ambient seawater this article is part of a special issue entitled cycles of trace elements and isotopes in the ocean geotraces and beyond edited by tim m conway tristan horner yves plancherel and aridane g gonzalez

tertiary deformation and metamorphism se of tibet the folded tiger leap decollement of nw yunnan china the yulong haba xue shan range in the northwestern part of yunnan china is a large n s antiform that folds the paleozoic series of the yangzi platform the upper yangzi river jinsha jiang has cut a 3500 m deep valley hu tiao gorge across this antiform thus exposing folded bedding parallel ductile shear zones decollements with transport toward the ssw in the present geographical coordinates the large finite shear strain implies tens of kilometers of transport pointing to the regional significance of these decollements rb sr radiometric dating of phlogopites that crystallized in marbles within the foliation planes yields the age of the metamorphic and deformation event 35 9 0 3 2 ma the age derives from an internal rb sr isochron made on different size fractions of the same mineral which provides a novel demonstration of the feasibility of such plots transport on the decollement and related shortening occurred prior to or at the onset of extrusion of indochina along the ailao shan red river shear zone 80 km west of the yulong shan the 39ar 40ar age spectra of k feldspar from the core of the yulong shan suggest uplift by antiformal folding around 17 ma as indochina s extrusion came to an end we infer that other large scale cenozoic decollements such as that exhumed in the yulong shan underlie some of the vast folded areas that surround the eastern himalayan syntaxis transport on such decollements first toward the south and then toward the east and folding above them might have occurred during two principal shortening phases whose ages bracket indochina s escape toward the se

glacial interglacial scale paleoclimatic change without large ice sheets in the oligocene of central oregon abundant late oligocene paleosols in eastern oregon compose a paleoclimatic archive rivaling the resolution of deep sea cores recording 105 milankovitch scale cycles over the 5 1 m y duration of the middle john day formation paleoclimatic cycles are apparent from the fossil record of snails mammals trace fossils soil structure depth to calcic horizon of paleosols and carbon and oxygen isotopic composition of pedogenic carbonate interpreted oligocene alternation between semiarid sagebrush steppe and subhumid wooded grassland has the same amplitude as that inferred during accumulation of the quaternary palouse loess in washington and oregon this similar amplitude is surprising because large ice caps like those of the quaternary did not extend across north america or europe during the oligocene thus ice albedo amplification of milankovitch scale insolation variation cannot explain the similar magnitude of oligocene paleoclimatic fluctuation weak orbital signals were more likely amplified by greenhouse gases such as co 2 and ch 4 due to changing carbon budgets in the sea and on land

long lived radionuclides as chronometers and tracers of environmental processes at the xi an accelerator mass spectrometry center abstract long lived radionuclides with half lives ranging from 103 to 108 years have wide applications in geochronology and environmental tracer studies a wide range of climatic geologic and environmental records preserved in diverse natural archives can be characterized by measuring their concentrations using accelerator mass spectrometry ams the purpose of this paper is to highlight some representative works on 14c 10be 26al and 129i in these two aspects at the xi an ams center in the past ten years since a dedicated ams facility was established the improvement of the sample preparation procedures the development of the new mathematical analysis method and related applications are summarized

wind driven currents in the tropical pacific abstract an analysis is made of the ensemble mean ageostrophic near surface circulation measured by 1503 lagrangian drifters drogued to 15 m depth in the tropical pacific between 1987 and 1994 it was found that the physical model of the wind driven currents in a weakly stratified upper layer in which the richardson number remains near unity accounts for 40 of the vector variance of the observations in such a model the amplitude of the current is proportional to u n f 1 2 and the depth scale of the wind driven layer is proportional to u n f 1 2 when the ageostrophic currents at 15 m depth are binned by the scaled ekman depth a net rotation of 0 87 radians was observed through the layer depth these measurements suggest that the vertical austausch coefficient of the upper ocean is proportional to u2 n ekman proposed such a model based on two reports of wind driven currents in 1905 at widely separated latitudes

multi iteration approach to studying tracer spreading using drifter data abstracta novel multi iteration statistical method for studying tracer spreading using drifter data is introduced the approach allows for the best use of the available drifter data by making use of a simple iterative procedure which results in the statistically probable map showing the likelihood that a tracer released at some source location would visit different geographical regions along with the associated arrival travel times the technique is tested using real drifter data in the north atlantic two examples are considered corresponding to sources in the western and eastern north atlantic ocean that is massachusetts bay like and irish sea like sources respectively in both examples the method worked well in estimating the statistics of the tracer transport pathways and travel times throughout the entire north atlantic the role of eddies versus mean flow is quantified using the same technique and eddies are shown to significantly broaden the spread of a tracer the sensitivity of the results

use of carbon isotopes in paleosols as an indicator of the p co2 of the paleoatmosphere measurements of carbon isotopic composition of coexisting paleosol organic matter and carbonate results in improved estimates of the paleo p co2 content of the paleoatmosphere measurements from tertiary paleosols indicate that the levels of co2 in the early eocene middle and late miocene and pliocene were less than 1000 ppmv early cretaceous levels of p co2 were significantly higher of the order of 1500 to 3000 ppmv

incision and differential bedrock uplift along the indus river near nanga parbat pakistan himalaya from 10be and 26al exposure age dating of bedrock straths abstract well preserved river cut bedrock surfaces straths abandoned by the progressive incision of the indus river in northern pakistan were dated using in situ cosmogenic 10 be and 26 al exposure age dating measurements on young and modern straths show no significant ingrowth of 10 be and 26 al implying that strath exposure ages closely approximate their abandonment age strath exposure ages range up to 65 ka and increase with height above the river the straths can be divided into two groups low straths dated at about 7 ka which yield very rapid bedrock incision rates 9 12 m ka and high straths 7 ka in age which yield somewhat slower incision rates 1 6 m ka incision rates for both groups increase by 1 3 m ka downstream toward an active reverse fault the raikot fault that forms the western border of the nanga parbat haramosh massif nphm the downstream increases in incision rates for the low straths mimic downstream increases in the modern gradient suggesting that bedrock incision rates have been proportional to stream power over the last 7 ka gradient increases are probably the result of the creation of knickpoints by bedrock uplift along the raikot fault the longitudinal profile and steep gorge of the indus river in the study area indicate that bedrock incision appears to keep pace with differential vertical motions between the nphm and surrounding regions thus the 1 3 m ka difference in incision rates likely reflects the differential bedrock uplift rate between the nphm and the skardu basin the differential incision rate is consistent with differential exhumation rates obtained from apatite fission track ages assuming geotherms of 80 90 c km in the nphm and 35 c km in the skardu basin this relation suggests that rapid bedrock incision of at least 1 3 m ka has persisted within the nphm for the last 0 5 ma the acceleration of incision rates throughout the study area since 15 ka is likely to be a climatic signal that records an increase in the discharge and or sediment load of the indus river in the study area related to deglaciation of the surrounding terrane

quantitative uncertainty analyses of ancient atmospheric co2 estimates from fossil leaves the relationship between atmospheric co 2 and ancient climate is of fundamental importance for gauging the climate sensitivity of the earth system to a changing co 2 regime one of the most widely adopted paleobiological co 2 proxies for reconstructing earth s atmospheric co 2 history exploits the inverse relationship between leaf stomatal index the fraction of leaf epidermal cells that are stomatal structures and atmospheric co 2 however fossil leaf based co 2 reconstructions make a prioii assumptions about the form of the empirical relationship between si and co 2 required for transfer functions and have failed to correctly propagate error terms these effects can translate into erroneous interpretations that undermine the value of the proxy here we report the development and application of a rigorous generalized statistical framework overcoming these limitations that generates probability density functions for each atmospheric co 2 estimate the utility of our statistical tools is demonstrated by showing how they revise earlier atmospheric co 2 estimates from fossil cuticles of ginkgo and metasequoia trees during the early eocene and middle miocene warm periods upwards by 150 to 250 ppm to 450 to 700 ppm the revised co 2 reconstructions therefore help to resolve the paradox of warm paleogene and neogene greenhouse climates co existing with near present day levels of co 2 and support the emerging view from independent paleoclimate studies for a high climate sensitivity of the earth system the statistical tools presented are sufficiently versatile to permit their use in other investigations of paleoco 2 estimates from fossil leaves

shallow marine deposits associated with the 2011 tohoku oki tsunami in sendai bay japan little is known about offshore tsunami deposits although they have the potential to improve palaeotsunami reconstructions especially in areas with limited preservation of onshore tsunami deposits we analysed 44 sediment cores collected in 2012 at water depths of 14 30 m in sendai bay north eastern japan to identify the deposits of the 2011 tohoku oki tsunami with the aid of 134cs released from the fukushima daiichi nuclear plant the preserved tsunami deposits in the inner shelf are interbedded with very fine sand and mud showing similar features to storm deposits in the shoreface a distinct layer of coarse sand overlies fine sand appearing to have originated as beach sand transported offshore by the tsunami backwash the coarse sand fades offshore around the boundary between the shoreface and inner shelf many of the core sites show evidence that surface sediment was reworked probably by post tsunami storm waves suggesting that further reworking would make the ultimate preservation of the tsunami deposits unlikely

high frequency holocene glacier fluctuations in the himalayan tibetan orogen abstract holocene glacial chronostratigraphies in glaciated valleys spread throughout the himalayan tibetan orogen including the himalaya tibet pamir and tian shan are developed using a landsystems approach detailed geomorphic mapping and new and published 10be surface exposure dating new studies in the kulti valley of lahul and the parkachik valley of the nun kun massif of the himalaya of northern india define three glacier advances at 14 7 12 2 0 5 ka in addition to one historically dated late 19th century advance in the kulti valley and one late holocene advance at 0 2 ka in the parkachik valley three major climatic groups subdivided into five climatic zones are defined across the orogen using cluster analysis ca and principal component analysis pca to identify glaciated regions with comparable climatic characteristics to evaluate the timing and extent of holocene glacier advances across these regions our regional analyses across the himalayan tibetan orogen suggest at least one lateglacial 15 3 11 8 ka and five himalayan tibetan holocene glacial stages hths at 11 5 9 5 8 8 7 7 7 0 3 2 2 3 1 0 and

refining the pedogenic carbonate atmospheric co2 proxy and application to miocene co2 abstract quantifying uncertainty is essential for any paleoenvironmental proxy recent work on propagating error through the equation used to determine atmospheric co 2 concentrations from paleosol carbonates yields conflicting results small magnitude uncertainty from gaussian error propagation contrasts with larger magnitude uncertainty from monte carlo error propagation the discrepancy is reconciled here by revising partial differential equations for the gaussian approach uncertainties calculated using the two approaches are compared and applied to miocene calcic paleosols monte carlo propagated errors are asymmetrical but otherwise agree with gaussian errors three methods for assigning soil respired co 2 concentrations s z to paleosols are also compared a revised calibration of depth to the bk horizon as a direct proxy for s z is presented and although it results in lower atmospheric co 2 concentrations than the original calibration it results in significantly higher calculated atmospheric co 2 than the use of mean annual precipitation as a proxy for s z or assigning s z values based on soil order averaging atmospheric co 2 concentrations calculated using soil order based s z values from 10 penecontemporaenous and independent paleosols will likely result in useful constraints on earth system sensitivity the improvement of proxies for s z is needed to increase the accuracy and precision and to resolve potential volatility in co 2 time series

evidence for holocene megafloods down the tsangpo river gorge southeastern tibet lacustrineandalluvialterracesandsedimentsrecordtheextentofatleasttwoholoceneglaciallydammedlakesimmediatelyupstreamofthe tsangpo rivergorge at the eastern syntaxis of the himalaya the larger lake covered 2835 km 2 with a maximum depth of 680 m and contained an estimated 832 km 3 of water the smaller lake contained an estimated 80 km 3 of water radiocarbon dating of wood and charcoal yielded conventional radiocarbon ages of 8860 f 40 and 9870 f 50 14 c yr b p for the higher set of lake terraces and 1220 f 40 and 1660 f 40 14 cy r b p forsedimentsfromthelowerterraces catastrophicfailureoftheglacialdamsthatimpoundedthelakeswouldhavereleasedoutburstfloods down the gorge of the tsangpo river with estimated peak discharges of up to 1 to 5 10 6 m 3 s 1 the erosive potential represented by the unit stream power calculated for the head of the gorge during such a catastrophic lake breakout indicates that post glacial megafloods down the tsangpo river were likely among the most erosive events in recent earth history d 2004 university of washington all rights reserved

extensive glacial advances during the last glacial maximum near the eastern himalayan syntaxis abstract climatically the eastern himalaya are mainly controlled by the indian summer monsoon ism and important region for understanding the relationship between ism and glacial change this region is therefore useful for studies of the relation between glacial changes and ism using a geomorpho stratigraphic method combined with gis we investigated and mapped the outmost lateral frontal moraine of the most extensive glaciations that occurred in the basongcuo bsc catchment near the eastern himalayan syntaxis using optically stimulated luminescence osl and 10 be surface exposure dating technique we dated five boulders and 23 sediment samples the resultant osl and 10 be ages show that the region s glaciers were at their most extensive positions between 16 and 31 ka glacial coverage was 507 5 km 2 9 9 times greater than it is today 51 5 km 2 with an equilibrium line altitude ela depression of 690 m the rapidity with which the last glacial maximum lgm glacial advance and retreat occurred suggests that temperature was the dominant control on glacial change

accuracy of cosmogenic ages for moraines analyses of all published cosmogenic exposure ages for moraine boulders show an average age range of 38 between the oldest and youngest boulders from each moraine this range conflicts with the common assumption that ages of surface boulders are the same as the age of the landform the wide spread in boulder ages is caused by erosion of the moraine surface and consequent exhumation of fresh boulders a diffusion model of surface degradation explains the age range and shows that a randomly sampled small set of boulders n 3 7 will always yield a lower age limit for the moraine the model indicates that for identical dating accuracy six to seven boulders are needed from old and tall moraines 40 000 100 000 yr 50 100 m initial height but only one to four boulders from small moraines 20 000 100 000 yr 10 20 m by following these guidelines the oldest obtained boulder age will be 90 of the moraine age 95 probability this result is only weakly sensitive to a broad range of soil erosion rates our analysis of published boulder ages indicates that 3 of all moraine boulders have prior exposure and 85 of these boulders predate the dated moraine

climatic and topographic controls on the style and timing of late quaternary glaciation throughout tibet and the himalaya defined by 10be cosmogenic radionuclide surface exposure dating abstract temporal and spatial changes in glacier cover throughout the late quaternary in tibet and the bordering mountains are poorly defined because of the inaccessibility and vastness of the region and the lack of numerical dating to help reconstruct the timing and extent of glaciation throughout tibet and the bordering mountains we use geomorphic mapping and 10 be cosmogenic radionuclide crn surface dating in study areas in southeastern gonga shan southern karola pass and central western nyainqentanggulha shan and tanggula shan tibet and we compare these with recently determined numerical chronologies in other parts of the plateau and its borderlands each of the study regions receives its precipitation mainly during the south asian summer monsoon when it falls as snow at high altitudes gonga shan receives the most precipitation 2000 mm a 1 while near the margins of monsoon influence the karola pass receives moderate amounts of precipitation 500 600 mm a 1 and in the interior of the plateau little precipitation falls on the western nyainqentanggulha shan 300 mm a 1 and the tanggula shan 400 700 mm a 1 the higher precipitation values for the tanggula shan are due to strong orographic effects in each region at least three sets of moraines and associated landforms are preserved providing evidence for multiple glaciations the 10 be crn surface exposure dating shows that the formation of moraines in gonga shan occurred during the early mid holocene neoglacial and little ice age on the karola pass during the lateglacial early holocene and neoglacial in the nyainqentanggulha shan date during the early part of the last glacial cycle global last glacial maximum and lateglacial and on the tanggula shan during the penultimate glacial cycle and the early part of the last glacial cycle the oldest moraine succession in each of these regions varies from the early holocene gonga shan lateglacial karola pass early last glacial western nyainqentanggulha shan and penultimate glacial cycle tanggula shan we believe that the regional patterns and timing of glaciation reflect temporal and spatial variability in the south asian monsoon and in particular in regional precipitation gradients in zones of greater aridity the extent of glaciation has become increasingly restricted throughout the late quaternary leading to the preservation of old 100 ka glacial landforms in contrast in regions that are very strongly influenced by the monsoon 1600 mm a 1 the preservation potential of pre lateglacial moraine successions is generally extremely poor this is possibly because lateglacial and holocene glacial advances may have been more extensive than early glaciations and hence may have destroyed any landform or sedimentary evidence of earlier glaciations furthermore the intense denudation mainly by fluvial and mass movement processes which characterize these wetter environments results in rapid erosion and re sedimentation of glacial and associated landforms which also contributes to their poor preservation potential

rayleigh distillation and the depth profile of 13c 12c ratios of soil organic carbon from soils of disparate texture in iron range national park far north queensland australia a depth and particle size specific analysis of soil organic carbon soc and its isotopic composition was undertaken to investigate the effects of soil texture or particle size on the depth profile of stable carbon isotopic composition of soc 13csoc in two tropical soils depth specific samples from two soil profiles of markedly different texture coarse grained and fine grained were separated into particle size classes and analyzed for the mass mass concentration of soc c and 13csoc within 1 m of the soil surface 13csoc in the coarse textured soil increases by 1 3 to 1 6 while 13csoc from the fine textured soil increase by as much as 3 8 to 5 5 this increasing depth trend in the coarse textured soil is approximately linear with respect to normalized c while the increase in the fine textured soil follows a logarithmic function with respect to normalized c a model of rayleigh distillation describing isotope fractionation during decomposition of soil organic matter som accounts for the depth profile of 13csoc in the fine textured soil but does not account for the depth profile observed in the coarse textured soil despite their similar climate vegetation and topographic position these results suggest that kinetic fractionation during humification of som leads to preferential accumulation of 13c in association with fine mineral particles or aggregates of fine mineral particles in fine textured soils in contrast the coarse textured soil shows very little applicability of the rayleigh distillation model rather the depth profile of 13csoc in the coarse textured soil can be accounted for by mixing of soil carbon with different isotopic ratios

too young or too old evaluating cosmogenic exposure dating based on an analysis of compiled boulder exposure ages cosmogenic exposure dating has greatly enhanced our ability to define glacial chronologies spanning several global cold periods and glacial boulder exposure ages are now routinely used to constrai

carbon isotope ratio of cenozoic co2 a comparative evaluation of available geochemical proxies 1 the carbon isotope ratio 13c of plant material is commonly used to reconstruct the relative distribution of c3 and c4 plants in ancient ecosystems however such estimates depend on the 13c of atmospheric co2 13cco2 at the time which likely varied throughout earth history for this study we use benthic and planktonic 13c and 18o records to reconstruct a long term record of cenozoic 13cco2 confidence intervals for 13cco2 values are assigned after careful consideration of equilibrium and non equilibrium isotope effects and processes as well as resolution of the data we find that benthic foraminifera better constrain 13cco2 compared to planktonic foraminiferal records which are influenced by photosymbiotes depth of production seasonal variability and preservation furthermore sensitivity analyses designed to quantify the effects of temperature uncertainty and diagenesis on benthic foraminifera 13c and 18o values indicate that these factors act to offset one another our reconstruction suggests that cenozoic 13cco2 averaged 6 1 0 6 1 while only 11 2 million of the last 65 5 million years correspond to the pre industrial value of 6 5 with 90 confidence here 13cco2 also displays significant variations throughout the record at times departing from the pre industrial value by more than 2 thus the observed variability in 13cco2 should be considered in isotopic reconstructions of ancient terrestrial plant ecosystems especially during the late and middle miocene times of presumed c4 grassland expansion

cosmogenic nuclide chronology of pre last glacial maximum moraines at lago buenos aires 46 s argentina at lago buenos aires argentina 10 be 26 al and 40 ar 39 ar ages range from 190 000 to 109 000 yr for two moraines deposited prior to the last glaciation 23 000 16 000 yr ago two approaches maximum boulder ages assuming no erosion and the average age of all boulders and an erosion rate of 1 4 mm 10 3 yr both yield a common estimate age of 150 000 140 000 yr for the two moraines the erosion rate estimate derives from 10 be and 26 al concentrations in old erratics deposited on moraines that are n760 000 yr old on the basis of interbedded 40 ar 39 ar dated lavas the new cosmogenic ages indicate that a major glaciation during marine oxygen isotope stage 6 occurred in the mid latitude andes the next five youngest moraines correspond to stage 2 there is no preserved record of a glacial advance during stage 4 the distribution of dated boulders and their ages suggest that at least one major glaciation occurred between 760 000 and n200 000 yr ago the mid latitude patagonian glacial record which is well preserved because of low erosion rates indicates that during the last two glacial cycles major glaciations in the southern andes have been in phase with growth and decay of northern hemisphere ice sheets especially at the 100 000 yr periodicity thus glacial maxima are global in nature and are ultimately paced by small changes in northern hemisphere insolation d 2005 university of washington all rights reserved

bedrock incision rock uplift and threshold hillslopes in the northwestern himalayas the topography of tectonically active mountain ranges reflects a poorly understood competition between bedrock uplift and erosion dating of abandoned river cut surfaces in the northwestern himalayas reveals that the indus river incises through the bedrock at extremely high rates 2 12 mm yr 1 in the surrounding mountains the average angles of hillslopes are steep and essentially independent of erosion rate suggesting control by a common threshold process in this rapidly deforming region an equilibrium is maintained between bedrock uplift and river incision with landsliding allowing hillslopes to adjust efficiently to rapid river down cutting

glacial advances and stability of the moraine dam on mount namcha barwa since the last glacial maximum eastern himalayan syntaxis abstract the tibetan plateau and indian plain exhibit the largest altitudinal difference between two geographically contiguous areas on earth but the eastern margin of the plateau has not experienced headward erosion of the yarlung zangbo river yzr since 2 5 ma in the past some scientists have argued that moraine dams on mount namcha barwa in the eastern himalayan syntaxis frequently blocked the yzr thus keeping the plateau s margin intact at this point in this study three sets of moraines were identified in the pai valley alongside namcha barwa and were dated using optically stimulated luminescence osl and 10be exposure dating the resultant ages would suggest that three glaciations occurred at 22 2 4 7 and 1 3 ka respectively comparison of osl and 10be ages for glacial advances with local paleoclimatic proxies would suggest that temperature was the dominant factor controlling glacial change because of the paleoglacial advance frequency coupling with rapid fluvial incision moraine dams were cut through by the yzr thus any moraine dams that lost their efficacy in impacting upon knickpoint migration instead similarities between rock uplift and fluvial incision rather than moraine dams might have been the main control impeding headward erosion of the yzr thereby keeping this part of the eastern tibetan plateau margin intact

new constraints on the late quaternary landscape evolution of the eastern tibetan plateau from 10be and 26al in situ cosmogenic nuclides abstract based on terrestrial cosmogenic nuclide tcn constraints from depth profiles of one granitic regolith from wumingshan and five fluvial terraces from xianshuihe and zagunao rivers we discuss the timing of the last deglaciation the landscape scale denudation and fluvial incision rates across the eastern tibetan plateau in relation to previous work we present a three dimensional graph visualization approach and corresponding constraints to better assess the feasibility and applicability of cosmogenic nuclides depth profile dating the exposure age older than 19 4 ka of the wumingshan regolith corresponds to the retreat of the palaeo daocheng ice cap which covered the yidun terrane during the last glacial maximum lgm most basin wide denudation rate data in the eastern tibetan plateau are lower than 130 mm ka 47 n 90 which is consistent with the wumingshan regolith denudation rate lower than 52 8 mm ka and thus indicate that the landscape scale denudation has been stabilized after the last deglaciation considering the reduction of integrated bulk density due to the accumulation of lower density loess we estimate mean exposure ages of xianshuihe and zagunao river terraces of 4 0 0 7 ka 5 9 0 3 ka 13 4 2 0 ka and 16 6 1 4 ka the observed increase in incision rate from 0 39 mm yr over long timescale 600 ka to 5 88 mm yr over the last 15 ka at the xianshuihe river site is probably due to the transition from glacial to interglacial climatic conditions the fewer abandoned terraces along the zagunao river after the heinrich event 1 h1 indicates that the climate change during the latest glacial interglacial transition impacted less the landscape evolution in a relatively lower elevation area comparison with previously reported fluvial incision rates elsewhere across the eastern margin of the tibetan plateau indicates that incision rates are mainly influenced by abrupt climate change or intensified summer monsoon since the early holocene but probably controlled by regional tectonic uplift or fluvial headward retreat as the timescale increases overall we propose a synthetic pattern of landscape evolution mainly dominated by long term tectonic uplift together with fluvial headward erosion episodically influenced by climatic change throughout the late quaternary

moraine dam related to late quaternary glaciation in the yulong mountains southwest china and impacts on the jinsha river abstract the yulong mountain massif is tectonically active during quaternary and contains the southernmost glacierized mountains in china and all of eurasia past glacial remnants remain preserved on the east and west sides of the yulong mountains a ridge of moraine protruded into the jinsha river at the daju basin damming the river and forming a lake at the head of the jinsha river cosmogenic 10 be and 26 al provide exposure age dates for the moraine based fluvial terraces left behind after the dam breached and for moraine boulders on both the eastern and western sides of the yulong mountains our results yield exposure ages for the terraces that range from 29 ka to 8 ka and a downcutting rate of 7 6 m ka the preservation of the remaining dam for over 10 000 years suggests stability of the moraine dam and gradual erosion of the dam during drainage of the dammed lake from the relationship between exposure ages and elevations of the fluvial terraces located in different walls of the daju fault we obtain a late quaternary dip slip rate of about 5 6 m ka for the daju fault the exposure ages of 10 2 ka and 47 ka for moraine boulders located in the east and west sides of the yulong mountains respectively coincide with warm periods in the late quaternary this implies that precipitation provides the major control for glaciations on the yulong mountains a domain of the southwest asian monsoon

nature and timing of quaternary glaciation in the himalayan tibetan orogen abstract much effort has been made in recent years to define the timing and extent of quaternary glaciation throughout the himalayan tibetan orogen these studies are challenging because of the logistical and political inaccessibility of the region and the inherent problems associated with the application of numerical dating techniques nevertheless the studies are providing abundant evidence for significant glacial advances throughout the last several glacial cycles and are beginning to accurately define the extent and timing of glaciation in selected regions studies are showing that himalayan tibetan glaciers in arid regions during the last glacial cycle reached their maximum extent early in the cycle and that global last glacial maximum glacier advances were significantly less extensive however along the more monsoonal influenced greater himalaya there is increasing evidence to suggest that glaciation was more extensive later in the last glacial cycle but this has yet to be fully assessed in addition the new studies are showing that throughout most himalayan tibetan regions significant glacier advances occurred during the lateglacial and early holocene with minor advances in some regions during the mid holocene the still relatively poor chronological control in the himalayan tibetan orogen however makes it difficult to construct correlations across the region and with regions elsewhere in the world this in turn makes it hard to assess the relative importance of the different climatic mechanisms that force glaciation across the himalayan tibetan orogen and to quantify paleoclimate change in this high altitude subtropical region the lateglacial and holocene glacial records however are particularly well preserved in several himalayan tibetan regions glacial successions such as these have the greatest potential to be examined in detail using newly developing numerical dating and geomorphic and sedimentologic methods to derive high resolution terrestrial records of glaciation that will help in paleoclimatic reconstruction for high altitude subtropical regions

late pleistocene glacial advances in the western tibet interior it has long been observed that the timing of glacial advances is asynchronous across the himalaya karakoram tibet plateau hktp but the climatic implications if any remain unclear resolving this question requires additional glacial chronologies from unique spatial and climatic regimes as well as an analysis of how glaciers within different regimes are likely to have responded to past climate changes this study presents a 10be 21ne chronology from the mawang kangri range of western tibet 34 n 80 e an arid high elevation site we identify advances at 123 83 and 56 kyr which agree reasonably well with sites in the immediate vicinity but are asynchronous relative to sites across the entire hktp and relative to sites in the western hktp to evaluate hktp wide asynchroneity we compile dated glacial chronologies and classify them by the approximate timing of their maximum recent advance this result shows a strong spatial clustering of young mis 1 2 relative to older mis 3 5 maximum advances further comparison with modern precipitation temperature and topographic data show that the pattern of hktp wide asynchroneity is broadly independent of topography and can potentially be explained by local responses to changes in temperature at either very warm wet or cold dry sites sites that receive intermediate amounts of precipitation are more ambiguous although spatial clustering of mis 1 2 vs mis 3 5 advances is suggestive of past variations in precipitation at these sites in western tibet no spatial or climatic correlation is observed with the timing of maximum glacial advances we suggest this could arise from mis interpretation of disparate boulder ages generated by a prolonged mis 3 4 glacial advance in the western hktp

quaternary paleolake formation and cataclysmic flooding along the upper yenisei river abstract a suite of geomorphological and sedimentological features in the catchment of the upper yenisei river in the sayan mountains of southern siberia testifies to the occurrence of cataclysmic floods that flowed down the river evidence of large scale high energy flood events includes 1 gravel dunes up to a few meters high and spaced 50 to 80 m apart in the kyzyl basin 2 landforms such as hanging valleys and paleochannels and 3 flood sediments in a tributary valley the origins of the yenisei floods were likely diverse due to complex hydrological processes operating in the sayan mountains the possibilities include failures of multiple variably impounded ice sedimentary tectonic scarp and lava flow dams paleolakes in the two large intermontane basins of darkhadyn khotgor and todza and other minor basins in the upper yenisei river catchment dating techniques applied to the paleolakes in the darkhadyn khotgor and todza basins revealed their formation during various periods in the middle late pleistocene and holocene flooding from the darkhadyn khotgor appears to explain many of the inferred flood features although contributions by flooding from other paleolake basins cannot be ruled out computer simulation of the flooding caused by a darkhadyn khotgor paleolake ice dam failure indicates a probable peak discharge of 3 5 10 6 m 3 s 1 approximately one fifth that of the floods that formed the channeled scabland in the u s a many of the outburst events probably occurred in the late quaternary but earlier floods could also have occurred

timing and climatic drivers for glaciation across monsoon influenced regions of the himalayan tibetan orogen abstract mapping and thirty eight 10 be terrestrial cosmogenic nuclide tcn ages help define the timing of glaciation in the monsoon influenced greater himalaya in central garwhal india glacial landforms in central garwhal are present only within a few kilometers of the present glaciers and all date to less than 12 5 ka this suggests that the lateglacial and or holocene glacial advances were more extensive than their predecessors and hence destroyed or buried evidence for earlier glaciation or that other processes such as intensive fluvial erosion and or hillslope mass movements have destroyed evidence of earlier glaciation prominent laterofrontal moraines date to the lateglacial the early holocene and the neoglaciation moraines next to the active ice and boulders on contemporary glaciers date to 10 1 10 2 years before present this suggests only a minor glacial advance during the little ice age occurred in central garhwal these young ages indicate that inheritance of tcns in areas that were recently glaciated is very small and likely has little effect when considering tcn ages on moraines older than the global last glacial maximum the new 10 be ages are combined with 1081 recalculated 10 be ages from previous studies to develop a regional framework of glaciation across the monsoon influenced and adjacent regions of the himalayan tibetan orogen we separate what appears to be continuous glaciation into 27 regional glacial stages plus 2 tentative glacial stages that are termed monsoonal himalayan tibetan stages mohits the regional glacial stages cover a wide chronologic range that includes five regional glacial stages older than the last glacial cycle mohits 13 at 483 38 ka to mohits 5e at 122 15 ka thirteen regional glacial stages within the last glacial cycle mohits 5b at 91 15 ka to mohits 2a at 12 9 0 9 ka and eleven regional glacial stages during the holocene mohits 1k at 11 4 0 7 ka to mohits 1a at 0 4 0 1 ka there are strong correlations both with periods of strong monsoons and northern hemisphere events throughout the entire chronologic range with 16 stages linked to the monsoon 11 stages linked to the mid latitude westerlies and two unassigned because of large age uncertainties overall we see a complex pattern of glaciation influenced by two climatic systems throughout the mid late quaternary

quantifying and understanding the uncertainty of atmospheric co2 concentrations determined from calcic paleosols 1 a computer program pbuq that uses monte carlo simulations to propagate uncertainty through regression equations and the equation for the paleosol carbonate co2 paleobarometer is presented pbuq includes options for all of the common approaches to determining values for input variables and incorporates several recent advancements relevant to determining values for soil respired co2 concentrations 13c values of respired co2 13c values of atmospheric co2 and temperatures of soil carbonate formation pbuq is intended to improve confidence in paleoatmospheric co2 research by helping researchers draw statistically significant conclusions pbuq can also be used to attribute and partition error among various sources and thereby advance this technique sensitivity analysis indicates that s z is the largest source of uncertainty for most paleosols and that uncertainty is minimized for soils in which co2 is an evenly balanced mixture between soil derived and atmospheric components evenly balanced mixtures are most likely for paleosols formed in deserts and for weakly developed paleosols development of proxies for soil respired co2 concentrations and 13c values of soil respired co2 specifically for such soils is perhaps the most crucial next step for improving this technique currently calcic paleosols are best used to test the significance of trends and or differences among time slices in paleoatmospheric co2 concentration application to quantifying earth system sensitivity will require large scale averaging of determinations from individual paleosols and or reduced uncertainty associated with input variables

minimal climatic control on erosion rates in the sierra nevada california climate is widely thought to regulate erosion rates but the relationships among precipitation temperature and erosion rate have remained speculative because long term erosion rates have been difficult to measure we used cosmogenic nuclides to measure long term erosion rates at climatically diverse sites in the sierra nevada california spanning 20 180 cm yr in annual precipitation and 4 15 8c in mean annual temperature average erosion rates vary by only 2 5 fold across these sites and are not correlated with climate indicating that climate only weakly regulates nonglacial erosion rates in mountainous granitic terrain

constraining the timing of the most recent cataclysmic flood event from ice dammed lakes in the russian altai mountains siberia using cosmogenic in situ 10be ice dammed lakes were repeatedly formed in intermontane basins in the russian altai mountains throughout the pleistocene these cataclysmic outburst floods caused by ice dam failures were documented as earth9s largest flood waves by other geoscientists using in situ 10 be we successfully dated surfaces of flood associated boulders located in a former lake basin and downvalley from a former ice dam our precise surface exposure ages suggest that all boulders were associated with the most recent out of a number of cataclysmic floods that occurred at 15 8 1 8 ka the field location of the boulders implies that they were deposited by the largest late pleistocene flood that drained the chuya katun lake completely following initial dam failure a published reconstruction of the late glacial paleoenvironment in the vicinity of the former ice dam indicates that dam failure was likely a result of climatically induced downwasting of glaciers the failure of the ice dam provides more evidence for the timing of widespread warming during the late glacial in southern russia this flooding event in the headwaters of the ob river coincides with a freshwater peak as recorded in isotopic records of the kara sea and the arctic ocean

scaling factors for the rates of production of cosmogenic nuclides for geometric shielding and attenuation at depth on sloped surfaces abstract the decrease in rates of production of cosmogenic nuclides occurs because of shielding of cosmic rays by mountains sloped surfaces and local rock formations that block them when a large part of the sky is blocked this correction is large and requires detailed model calculations this paper considers three geometries a rectangular obstruction a triangular obstruction and a sloped surface other geometries can be considered as a combination of these the results are presented in terms of formulas and graphs so that the reader can easily apply them to common field situations any use of cosmogenic nuclides in the study of geomorphic processes or forms must consider factors that introduce variations in the production of nuclides

environmental change in the great plains an isotopic record from fossil horses abstract carbon and oxygen isotope ratios of fossil horse tooth enamel from nebraska and texas show evidence for late neogene environmental changes in the great plains the earliest unambiguous c4 dietary signal among texas equids coincides with the age of the classic late hemphillian age coffee ranch fauna which we suggest is 6 6 ma based on volcanic ash correlations c4 vegetation was present in the diets of a small fraction of late hemphillian equids in nebraska and was thereafter ordinary in the diets of both nebraska and texas equids there is no unequivocal evidence for abundant c4 vegetation in the diets of pre late hemphillian equids and we suggest that the ensuing dietary change reflects c4 biomass expansion in the latest miocene carbon isotope ratios of post hemphillian horses in nebraska can be divided into two statistically distinct populations on the basis of whether tortoise remains co occur with horse remains indicating that the two proxies carbon isotopes and presence absence of tort

paleohydrology of late pleistocene superflooding altay mountains siberia cataclysmic flooding is a geomorphological process of planetary significance landforms of flood origin resulted from late pleistocene ice dammed lake failures in the altay mountains of south central siberia peak paleoflows which exceeded 18 x 10 6 cubic meters per second are comparable to the largest known terrestrial discharges of freshwater and show a hydrological scaling relation to floods generated by catastrophic dam failures these seem to have been earth9s greatest floods based on a variety of reconstructed paleohydraulic parameters

climate change vegetation history and landscape responses on the tibetan plateau during the holocene a comprehensive review abstract numerous studies of changes in the climate vegetation and landscape responses of the tibetan plateau tp during the holocene have been published in recent decades however several conflicting interpretations are evident within these studies and a comprehensive review of the topic is needed to reconcile them and thus to provide an improved understanding of the history and forcing mechanisms of holocene environmental changes within the region here we review the evidence for changes in climate temperature precipitation moisture vegetation and landscape attributes glacier and eolian activity on the tp during the holocene our main conclusions are as follows 1 the patterns of holocene mean annual temperature change on the tp remain controversial however an early to middle holocene summer temperature maximum is evident which coincided with high summer insolation and a strengthening of the indian summer monsoon ism this suggests that the summer land sea thermal gradient impacted by the temperature of the tp may be an important factor driving orbital scale ism changes 2 lake level records indicate an optimum in moisture conditions on the southwestern sw tp in the early holocene while on the northeastern ne tp the optimum occurred in the middle to late holocene this out of phase or anti phased relationship may be linked to the role of the ism in dominating precipitation on the sw tp while the westerlies and east asian summer monsoon dominated the precipitation on the ne tp 3 most of the lake sediment based stable isotope records 18o and leaf wax d exhibit a pattern similar to that of stalagmite 18o records from monsoonal asia reflecting the dominance of large scale patterns of atmospheric circulation rather than localized moisture changes reflected by lake level records 4 a synthesis of pollen records reveals that the extent of forest was maximal in the mid holocene while from the early holocene onwards alpine steppe shrunk and alpine meadow and desert gradually expanded 5 evidence of glacier advance increased slightly during the early holocene decreased during the mid holocene and then increased substantially after 3 ka bp 6 the integrated ages of eolian sand and loess from the ne tp reveal that eolian activity intensified during the early and late holocene site inter comparisons reveal that regional climate change played a major role in modulating changes in vegetation and other landscape attributes overall producing holocene climate reconstructions for the entire tp remains a major challenge even though much progress has been made further improvements in terms of the spatial coverage of high resolution paleoclimatic records with robust chronological control and a deeper understanding of the specific climatic significance of several climatic proxies will facilitate an improved understanding of how the monsoon and the westerlies interacted and their impacts on vegetation and landscape changes on the tp

the huanghe yellow river and changjiang yangtze river deltas a review on their characteristics evolution and sediment discharge during the holocene abstract today asian rivers play an important role in delivering sediment from the land to the oceans however past sediment discharge before human activities modified the landscape is not well known and is estimated to have been roughly one third to one half of the present level chinese rivers have been strongly influenced by human activities and their sediment discharge has changed over the last 6000 years for the study of the long term human impact on rivers and catchment basins chinese rivers provide excellent examples because continuous historical records are available here the characteristics evolution and sediment discharge during the holocene of the deltas of two large chinese rivers huanghe yellow river and changjiang yangtze river are summarized the huanghe and changjiang deltas are different with respect to coastal environments water and sediment discharge the pattern of development of the delta lobe thickness of holocene sediments and basal topography of the incised valleys formed during the last glacial period the huanghe delta is characterized by a high concentration of sediment huge sediment discharge thin holocene deltaic sediments a lateral delta lobe shift and a steep longitudinal profile in its lower reaches the changjiang delta is characterized by a large water discharge a large interseasonal water level change a tide dominated coastal environment continuous seaward progradation with isolated river mouth sand bodies thick holocene sediments and a deep incised valley formed during the last glacial period based on the sediment volume of prograding deltaic sediments over the last 6000 years the sediment discharge of huanghe 1000 years ago is estimated to have been 1 10 8 tons year 1 10 of the present level an abrupt increase occurred at ca 1000 years ago as a consequence of human activities on the loess plateau especially involving cultivation and deforestation moreover the estimated sediment load of huanghe at sanmenxia station prior to 1000 years was 2 7 4 0 10 8 tons year or about 20 15 25 of the present level our recent study estimated that the sediment discharge of changjiang before 2000 years bp was ca 2 4 10 8 tons year total sediment discharge of both rivers before 2000 years bp is estimated to have been 3 4 10 8 tons year or only about 20 of the present level moreover the total sediment load to the lower reaches is estimated to have been 5 6 10 8 tons year or one fourth the present level

cosmogenic nuclide constraints on late quaternary glacial chronology on the dalijia shan northeastern tibetan plateau abstract cosmogenic nuclide cn apparent exposure dating has become a widely used method for determining the age of glacial landforms on the tibetan plateau with 1200 published ages we present the first 10be exposure ages from the dalijia shan the most northeastern formerly glaciated mountain range on the tibetan plateau the moraine groups identified from field and remote sensing imagery mapping record four glacial events at 37 07 3 70 to 52 96 4 70 ka mis 3 20 17 1 79 to 26 99 2 47 ka mis 2 16 92 1 49 to 18 76 1 88 ka mis 2 and 11 56 1 03 to 11 89 1 06 ka younger dryas these ages indicate that glaciation in the northeastern tibetan plateau is much younger than previously thought in addition this record is consistent with many other regions on the tibetan plateau with a local last glacial maximum during mis 3 asynchronous with northern hemisphere last glacial maximum during mis 2 the dalijia shan might also include an event of younger dryas age but this needs to be tested in future studies

observed eastward progression of the fukushima 134cs signal across the north pacific radionuclide samples taken as part of hydrographic surveys at 30 n in the north pacific reveal that the easternmost edge of fukushima derived 134cs observed at 174 3 w in 2012 had progressed eastward across the basin to 160 6 w by 2013 the 2013 30 n observations indicate surface 134cs concentrations of 3 5 bq m3 between 160 e and 160 w slightly lower concentrations west of 160 e and no detectable signal east of 160 6 w profile samples show 134cs penetration to 500 m west of 180 with shoaling penetration depth toward to the east the near uniform vertical distribution of 137cs between 152 w and 121 3 w in the top 500 m is indicative of trace amounts of radionuclides remaining from weapons testing the physical processes responsible for the deep 134cs penetration in the western pacific appear to be related to distinct water mass subduction pathways however the timing and rapidity of deep penetration over the broad scales observed has yet to be clarified

diatom response to climatic and tectonic forcing of a palaeolake at the southeastern margin of the tibetan plateau during the late pleistocene between 140 and 35 ka bp abstract the heqing basin is located in yunnan province south western china near the southeastern edge of the tibetan plateau a region that is strongly influenced by the asian monsoon its long sedimentary record represents an archive of global importance for palaeoclimate research this study presents the results of diatom analysis of the last 140 35 ka of the record dated using ams 14 c and magnetostratigraphy diatoms are generally well preserved apart at the top of the sequence after 35 ka bp in which diatoms were too few to be counted the diatom data provide a detailed history of palaeoenvironmental changes during the late pleistocene and demonstrate the sensitivity of diatoms to changes in climate and hydrology in particular they provide proxy evidence for water depth and indirect evidence for temperature changes that are characterized by glacial interglacial shifts between planktonic and benthic diatoms and variations in the percentage of the warm water and eutrophic species aulacoseira granulata respectively in the heqing sequence remarkably high proportions of benthic diatoms coincide with warm and wet conditions suggesting that at this site the diatom signal is mediated by climate catchment vegetation processes such as the concentration of nutrient and runoff from the catchment from 132 ka bp however the tectonic uplift of the basin caused a change in the hydrological setting of the lake pollen and geochemical data are then used to help interpreting the diatom sequence and disentangle the direct effects of climate from those mediated by the conditions on the catchment such as the influence of glacier melt water

erosion in northwest tibet fromin situ produced cosmogenic10be and26al in bedrock concentrations of in situ produced cosmogenic nuclides 10be and 26al in quartz were measured by accelerator mass spectrometry for bedrock basalts and sandstones located in northwest tibet the effective exposure ages range between 23 and 134 ka 10be and erosion rates between 4 0 and 24 mm ka 1 the erosion rates are significantly higher than those in similarly arid antarctica and australia ranging between 0 1 and 1 mm ka 1 suggesting that precipitation is not the major control of erosion of landforms comparison of erosion rates in arid regions with contrasting tectonic activities suggests that tectonic activity plays a more important role in controlling long term erosion rates the obtained erosion rates are however significantly lower than the denudation rate of 3000 6000 mm ka 1 beginning at c 5 3 ma in the nearby godwin austen k2 determined by apatite fission track thermochronology it appears that the difference in erosion rates within different time intervals is indicative of increased tectonic activity at c 5 3 ma in northwest tibet we explain the low erosion rates determined in this study as reflecting reduced tectonic activity in the last million years a model of localized thinning of the mantle beneath northwest tibet may account for the sudden increased tectonic activity at c 5 3 ma and the later decrease copyright 2006 john wiley sons ltd

tibetan plateau river incision inhibited by glacial stabilization of the tsangpo gorge much attention has focused on how and when the tibetan plateau formed but far less research has been done on the controls on river incision into the plateau itself oliver korup and david montgomery address this issue which also relates to the question of why the tibetan plateau is still there at all despite hosting one of the deepest gorges on earth the plateau edge is extremely well defined and according to widely accepted stream power theory should be heavily dissected by one of asia s most powerful rivers the yarlung tsangp or yarlung zangbo korup and montgomery propose that the southeastern edge of the plateau was preserved in part by the presence of glaciers that were large enough during the holocene to stall aggressive river downcutting along the plateau margin a considerable amount of research has focused on how and when the tibetan plateau formed in the wake of tectonic convergence between india and asia1 although far less enquiry has addressed the controls on river incision into the plateau itself2 widely accepted theory3 predicts that steep fluvial knick points river reaches with very steep gradients in the eastern himalayan syntaxis at the southeastern plateau margin should erode rapidly4 driving a wave of incision back into the plateau preservation of the plateau edge thus presents something of a conundrum that may be resolved by invoking either differential rock uplift matching erosional decay5 6 7 or other mechanisms for retarding bedrock river incision8 9 in this region where high stream power excludes the potential for aridity as a simple limit to dissection of the plateau10 here we report morphologic evidence showing that quaternary depression of the regional equilibrium line altitude where long term glacier mass gain equals mass loss was sufficient to repeatedly form moraine dams on major rivers such damming substantially impeded river incision into the southeastern edge of the tibetan plateau through the coupled effects of upstream impoundment and interglacial aggradation such glacial stabilization of the resulting highly focused river incision centred on the tsangpo gorge could further contribute to initiating and accentuating a locus of rapid exhumation known as tectonic anaeurysm6

scaling factors for production rates of in situ produced cosmogenic nuclides a critical reevaluation abstract new scaling factors are presented describing the altitude and latitudinal dependence of production rates for in situ produced cosmogenic nuclides the new factors incorporate the influence of the non dipole contributions to the geomagnetic field on the cosmic ray flux the currently used scaling factors of lal earth planet sci lett 104 1991 424 439 are based on the assumption of a dipole field the overall strategy used in deriving the new scaling factors is however very similar to that of lal and relies on the same and or similar nuclear data in this reevaluation data are only used if the effective geomagnetic parameters inclination horizontal field strength can be reconstructed for the time of measurement the absorption free pathlengths for cosmic rays selected for this study are based on observational data at altitudes relevant for exposure age dating sea level to 7000 m at sea level and latitudes between 20 and 40 the new factors are up to 18 lower and at high altitudes more than 30 higher than those of lal in addition to accounting for the influence of the effective geomagnetic field and providing more applicable estimates of the new factors also allow for correction for the significant deviations from the standard pressure altitude relationship that exist in the atmosphere 10

timing of multiple late quaternary glaciations in the hunza valley karakoram mountains northern pakistan defined by cosmogenic radionuclide dating of moraines moraines and associated landforms in the upper hunza valley karakoram mountains northern pakistan provide an excellent record of multiple glaciations during the late quaternary glaciers advanced at least eight times by using 10 be and 26 al surface exposure dating on moraine boulders and scoured bedrock we determined the timing of glaciation for four of these glacial advances ca 54 7 43 2 ka borit jheel glacial stage ca 25 7 21 8 ka ghulkin i glacial stage ca 18 4 15 3 ka ghulkin ii glacial stage and ca 10 8 9 0 ka batura glacial stage for two of the older advances the yunz and shanoz glacial stages our data set a limit of 60 ka although at present the uncertainties in dating make it impossible to describe unequivocally the climate processes controlling glaciations in the hunza valley the results suggest that precipitation changes related to oscillations in the southwest asian monsoonal system combine with cooling that is broadly associated with heinrich events to cause glacial advances in this region

dip slip rate determined by cosmogenic surface dating on a holocene scarp of the daju fault yunnan china abstract the daju and lijiang daju fault zones which bound the yulong mountains on its northern and eastern perimeters respectively are segments of a continuous fault system that bends at daju uplift of the yulong mountains the southernmost glacierized mountain range in eurasia resulted from the normal faulting characteristics of the fault system using cosmogenic surface exposure dating with 10 be and 26 al we have measured bedrock exposure ages as a function of elevation along an exposed bedrock scarp of the daju fault 10 be and 26 al exposure ages increase monotonically with elevation ranging from 2 6 to 9 6 ka over the 51 m scarp length giving an average dip slip rate of 7 5 m ka during the holocene period and a vertical uplift rate of 5 7 m ka the 5 7 m ka holocene uplift rate and supporting geomorphic features suggest that the uplift of the yulong mountains mainly occurred in the quaternary the fast slip rate and seismic quiescence for the recent 2 8 ka call attention to the possible recurrence of large magnitude earthquake events along the fault zone

coupling of co2 and ice sheet stability over major climate transitions of the last 20 million years the co2 content of the atmosphere has varied cyclically between 180 and 280 ppmv over the last 800 000 years closely coupled with temperature and sea level for earlier periods in earth s history pco2 is much less certain and the relationship between pco2 and climate remains poorly constrained we use boron calcium ratios in foraminifera to estimate pco2 during major climate transitions of the last 20 million years myr during the middle miocene when temperatures were 3 to 6 c

links between climate and sea levels for the past three million years the oscillations between glacial and interglacial climate conditions over the past three million years have been characterized by a transfer of immense amounts of water between two of its largest reservoirs on earth the ice sheets and the oceans since the latest of these oscillations the last glacial maximum between about 30 000 and 19 000 years ago approximately 50 million cubic kilometres of ice has melted from the land based ice sheets raising global sea level by approximately 130 metres such rapid changes in sea level are part of a complex pattern of interactions between the atmosphere oceans ice sheets and solid earth all of which have different response timescales the trigger for the sea level fluctuations most probably lies with changes in insolation caused by astronomical forcing but internal feedback cycles complicate the simple model of causes and effects

input of anthropogenic radionuclides into the world ocean abstract since the early 1940s when the nuclear era began the earth has received anthropogenic radioactive contamination the main sources have been fallout from nuclear weapons testing in the atmosphere until 1980 discharges from nuclear reprocessing of spent fuel elements from nuclear reactors with maximum releases in the mid 70s and finally the chernobyl reactor accident which occurred in 1986 as the ocean covers more than 2 3 of the earth s surface a substantial part of the radioactive contamination of our planet is to be found in the marine environment by the year 2000 total inventories of three of the most studied anthropogenic radionuclides in the world ocean were 0 2 ebq 90sr 0 35 ebq 137cs and 0 01 ebq 239 240pu in the case of 137cs the contribution from global fallout is 69 of the total inventory from local fallout 21 from reprocessing 7 and from chernobyl 3 the most contaminated part of the world ocean is the ne atlantic ocean which besides fallout from nuclear weapons testing also has received inputs from reprocessing plants and the chernobyl accident

late quaternary glaciation of the tianshan central asia using cosmogenic 10be surface exposure dating abstract glacial deposits are present at the head of the urumqi river valley tianshan central asia 10be surface exposure ages of 15 boulders from three sites along a 12 km valley transect range from 9 to 21 ka suggesting emplacement by glacial retreat and advance commencing at the global last glacial maximum lgm and most likely abating in the early holocene although the age spread for a given locality is not small perhaps indicating post depositional reworking maximum ages per site are either coeval with or are post lgm and inconsistent with previous pre lgm electron spin resonance ages