a 100 kyr periodicity in the flux of extraterrestrial 3he to the sea floor most of the helium 3 in oceanic sediments comes from interplanetary dust particles idps and can therefore be used to infer the accretion rate of dust to the earth through time 3he records from slowly accumulating pelagic clays indicate that the accretion rate varies considerably over millions of years probably owing to cometary and asteroidal break up events muller and macdonald have proposed that periodic changes in this accretion rate due to a previously unrecognized 100 kyr periodicity in the earth s orbital inclination might account for the prominence of this frequency in climate records of the past million years here we report variations in the 3 he flux to the sea floor that support this idea we find that the flux recorded in rapidly accumulating quaternary sediments from the mid atlantic ridge oscillates with a period of about 100 kyr we cannot yet say however whether the 100 kyr climate cycle is a consequence of a cause of or an effect independent of these periodic changes

geochemical mapping of magmatic gas water rock interactions in the aquifer of mount etna volcano abstract systematic analysis of major and minor elements in groundwaters from springs and wells on the slopes of mt etna in 1995 1998 provides a detailed geochemical mapping of the aquifer of the volcano and of the interactions between magmatic gas water bodies and their host rocks strong spatial correlations between the largest anomalies in pco2 ph and alkalinity k rb mg ca and sr suggest a dominating control by magmatic gas co2 and consequent basalt leaching by acidified waters of the shallow meteoric etnean aquifer most groundwaters displaying this magmatic type interaction discharge within active faulted zones on the s sw and e lower flanks of the volcanic pile but also in a newly recognised area on the northern flank possibly tracking a main n s volcano tectonic structure in the same time the spatial distribution of t c tds na li cl and b allows us to identify the existence of a deeper thermal brine with high salinity high content of b cl and gases co2 h2s ch4 and low k na ratio which is likely hosted in the sedimentary basement this hot brine reaches the surface only at the periphery of the volcano near the village of paterno where it gives rise to mud volcanoes called salinelle di paterno however the contribution of similar brines to shallower groundwaters is also detected in other sectors to the w bronte maletto sw adrano and se acireale suggesting its possible widespread occurrence beneath etna this thermal brine is also closely associated with hydrocarbon fields all around the volcano and its rise generally masked by the high outflow of the shallow aquifer may be driven by the ascent of mixed sedimentary magmatic gases through the main faults cutting the sedimentary basement

late quaternary paleoclimatic and geomorphological evolution at the interface between the menyuan basin and the qilian mountains northeastern tibetan plateau abstract the tibetan plateau is regarded as an amplifier and driver of environmental change in adjacent regions because of its extent and high altitude however reliable age control for paleoenvironmental information on the plateau is limited osl appears to be a valid method to constrain the age of deposits of glacial and fluvial origin soils and periglacial structures in the menyuan basin on the northeastern tibetan plateau dating results show glaciers advanced extensively to the foot of the qilian mountains at 21 ka in agreement with the timing of the global last glacial maximum lgm recorded in northern hemisphere ice cores comparison with results from the eastern tibetan plateau suggests that the factor controlling glacial advance in both regions was decreased temperature not monsoon related precipitation increase the areas of the menyuan basin occupied by glacio fluvial deposits experienced continuous permafrost during the lgm indicated by large cryoturbation features interpreted to indicate that the mean annual temperature was 7 c lower than at present glacio fluvial systems in the menyuan basin aggraded and terraces formed during cold periods penultimate glaciation lgm and possibly the younger dryas as a response to increased glacial sediment production and meltwater runoff then

quaternary glaciations and glacial landform evolution in the tailan river valley tianshan range china abstract the tailan river originates on the southern slope of tumur peak the largest center of modern glaciation in the tianshan range five moraine complexes and associated fluvioglacial deposits in this valley record a complex history of quaternary glacial cycles and landform evolution electron spin resonance esr dating of glacial sediments was carried out using germanium ge centers in quartz grains which are sensitive to both sunlight and grinding based on the dating results as well as geomorphic and stratigraphic data the piyazilike end moraines the second moraine complex were deposited during neoglaciation the largest glacial advances during the last 3 4 ka in western china and an early holocene glacial advance the third set of moraines was deposited in marine isotope stage mis 2 4 and the glacial landforms of the tailan glaciation the fourth moraine complex which include hummocky moraines on the piedmont were formed in mis 6 penultimate glaciation the end moraines of the innermost moraine complex the first moraine complex are inferred to have been deposited during the little ice age lia thus the landforms and dates indicate compound valley glaciers from the lia to mis 2 4 and piedmont glaciers during mis 6 the oldest tills studied belong to the kokdepsang glacial stage and occur on a high plateau based on similar glacial landforms glacial deposits on a high plateau and a high glacial terrace and their esr ages in adjacent valleys on the southern slope of tumur peak the kokdepsang glacial stage is assigned to mis 12

the contribution by interplanetary dust to noble gases in the atmosphere of mars interplanetary dust particles accumulate significant concentrations of noble gases implanted by the solar wind and solar energetic particles while they are in space when these dust particles enter the atmosphere of a planet they are heated and decelerated depositing some of the implanted noble gases directly into the atmosphere and if the particle survives atmospheric entry emplacing the remainder on the surface of the planet where it can be released by particle decomposition or by episodic surface heating because of the low mass of the atmosphere of mars compared to the atmospheres of venus and earth the atmosphere of mars is more severely influenced by the addition of noble gases by interplanetary dust the contribution of noble gases to mars has been modeled using estimates of the interplanetary dust flux at mars and measurements of the noble gas contents of interplanetary dust collected from the atmosphere of the earth over the past 3 6 b y interplanetary dust particles have contributed quantities of 3he 4he 20ne and 22ne comparable to the current total atmospheric inventories of these isotopes in the present era the rates of addition of 3he 20ne 22ne 36ar and 38ar to the atmosphere of mars by interplanetary dust range from about 2 to 20 of the modeled rates of addition by planetary outgassing pepin 1994 krasnopolsky and gladstone 1996 and the isotopic compositions of the he and ne added by interplanetary dust are distinctly different from those assumed for planetary outgassing 3he 4he 2 8 10 4 in the interplanetary dust nier and schlutter 1992 versus almost pure 4he for outgassing of u and th decay products and 20ne 22ne 11 8 in the interplanetary dust niert 1994 versus 20ne 22ne 13 7 assumed for planetary outgassing in pepin s 1994 model since the actual outgassing rate of mars in the present era is not well constrained by observations the contributions of ne and ar to the atmosphere of mars by the interplanetary dust must serve at least as a lower limit on the current sources of these noble gases

late glacial 10be ages for glacial landforms in the upper region of the taibai glaciation in the qinling mountain range china abstract glacial landforms are well preserved on taibai mountain 3767 m the main peak of the qinling mountain range located south of the loess plateau and east of the qinghai tibet plateau the timing and extent of quaternary glaciation in the study area is important for reconstructing quaternary environmental change however numerical ages for glaciation in this study area have not previously been well resolved using terrestrial in situ cosmogenic nuclides we dated four samples collected from two glacially eroded rock steps in the upper part of a valley near the main peak in an area previously identified as having been occupied by ice during the taibai glaciation the 10be results are all late glacial in age 18 6 1 1 ka 16 9 1 0 ka 16 9 1 1 ka and 15 1 1 0 ka the spatial pattern of ages in the valley suggests fast retreat with horizontal and vertical retreat rates estimated to be on the order of 0 4 and 0 09 m a 1 respectively a simple extrapolation of these retreat rates from the ages at the two sample sites suggests that the glacier retreat began during last glacial maximum and that glaciers disappeared from the main peak by about 15 ka

glacial geomorphology and glacial history of the muzart river valley tianshan range china abstract the muzart river originates on the southeastern slope of tumur peak the largest center of modern glaciation in the tianshan range glacial landforms and sediments indicate that there are four major quaternary glaciations in this drainage the glacial landforms contain considerable information about the changes of the ancient glaciers dating the landforms allows the temporal and spatial variations of the ancient glaciers in this valley to be understood and provides essential information in reconstructing the paleoenvironment in this region electron spin resonance esr dating of a well exposed section the multiple end moraines of the pochengzi glaciation the third set of moraines and the local outwash and fluvial sediments on the kezibulake glacial plain the fourth set of moraines was carried out using germanium ge centers in the glacial quartz grains which are sensitive to both sunlight and grinding eleven depositional ages have been determined based on the dating results the principle of superposition and the glaciations pattern reported in the adjacent valley the pochengzi end moraines were determined to be deposited during the major glacial intervals that are equivalent in age to marine oxygen isotope stages mis 2 mid mis 3 and mis 4 and the kezibulake glacial deposits were determined to be equivalent in age to mis 6 furthermore the tugaibieliqi end moraine the second set of moraines was deposited during the neoglaciation a cold period between 3 and 4 ka and the 3 4 end moraines located at the terminuses of the modern glacier were deposited during the little ice age the ages of the pochengzi glacial deposits can be subdivided into three clusters they are 13 6 25 3 ka 39 5 40 4 ka and 64 2 71 7 ka respectively the largest local last glacial maximum lgm l occurred during mis 4 rather than the global last glacial maximum lgm g of mis 2 furthermore a glacier that is slightly larger than that of mis 2 developed in this drainage during mid mis 3 the ancient muzart glaciers were compound valley glaciers during the neoglaciation mis 2 and mid mis 3 and piedmont glaciers during mis 4 and mis 6

timing and style of late quaternary glaciation in northeastern tibet glacial successions in the anyemaqen and nianbaoyeze mountains of northeastern tibet are reassessed and new glacial chronologies are presented for these regions cosmogenic radionuclide and optically stimulated luminescence dating indicates that two glacial advances occurred in marine isotope stage mis 3 and mis 2 in the anyemaqen mountains a third advance occurred in the early holocene we suggest that glaciation was synchronous in the anyemaqen and nianbaoyeze mountains as well as in other glaciated areas of tibet and the himalaya that are influenced by the asian monsoon the maximum extent of glaciation occurred early in the last glacial cycle mis 3 during a time of increased insolation when the monsoon intensified and supplied abundant precipitation as snow at high altitude to feed high altitude glaciers this suggests that precipitation as snow is fundamental in controlling glaciation in these regions however the occurrence of glacial advances during the insolation minimum of mis 2 suggests that despite reduced precipitation at this time the annual temperatures were cold enough to maintain positive glacier mass balances the numerically defined chronologies for the anyemaqen and nianbaoyeze mountains presented here provide a framework for comparing glacial advances in other parts of high asia

equilibrium line altitudes of the last glacial maximum for the himalaya and tibet an assessment and evaluation of results abstract contemporary equilibrium line altitudes elas for glaciers in the high mountains of the himalaya and tibet have considerable variation because the region is influenced by two major climatic systems the mid latitude westerlies and the south asian summer monsoon and glaciers are subject to strong topographic controls reconstructions of past elas based on the former extent of glaciers are numerous but were estimated using a variety of methods some of which are not appropriate for high altitude glaciers which are strongly influenced by topography and have extensive supraglacial debris cover furthermore few of the reconstructions have adequate chronological control because of the difficulty of dating glacial landforms in high altitude regions where organic matter for radiocarbon dating is sparse or absent cosmogenic radionuclide surface exposure and optically stimulated luminescence dating are providing data to define the timing of glaciation and these together with objective analysis of glacier dynamics may allow better estimates of ela changes in the future however there are currently only two regions the hunza valley and the khumbu himal which are sufficiently well dated to allow reconstructions of last glacial maximum glacier extent and hence elas these two regions cannot provide an adequate assessment of ela changes for the himalayan tibetan region

a comparative study of accumulation rates derived by he and th isotope analysis of marine sediments abstract we present a detailed down core analysis of helium isotope ratios and concentrations for bulk sediments from the central equatorial pacific that span the last two glacial interglacial cycles measured 3 he 4 he ratios range from 1 0 10 5 to 2 1 10 4 or 7 4 to 149 times the atmospheric ratio the 3he from interplanetary dust particles idps constitutes virtually all of the 3he measured within the sediment because carbonate accumulation rates are high in the equatorial pacific the measured 3he concentrations are lower than have been measured elsewhere and range from 4 7 10 13 to 3 0 10 12 cm3stp g 1 if the cosmic dust 3he flux is constant with time sediment mass accumulation rates can be determined from the 3he concentration in sediments the excess 230th technique is an entirely independent method for calculating sediment mass accumulation rates because its source is in situ decay of 234u in seawater to first order initial excess 230th activities correlate with 3he concentrations within this core based on the 230th results we estimate the 3he flux to the earth s surface as 9 6 2 0 10 16 cm3stp cm 2 a 1 if this flux has remained constant over extended periods of time it can be used to determine sediment accumulation rates beyond the 230th range 300 000 yr

quaternary glaciations recorded by glacial and fluvial landforms in the shaluli mountains southeastern tibetan plateau abstract the shaluli mountains a tectonically controlled mountain range between the jinsha and yalong river rifts are located in southeastern tibetan plateau in the central shaluli mountains an ice cap of 3600 km 2 once developed on the haizi shan abundant glacial landforms are present on the haizi shan and in the surrounding river valleys together with the outwash terraces in the yazheku river the northeastern part of the haizi shan provides an ideal site to examine the quaternary glacial history of the region sedimentological and morphostratigraphical analysis field mapping and dating by electron spin resonance esr define at least seven major glacier advances in the haizi shan area six major glacier advances likely occurred during marine oxygen isotope stage mis 16 mis 14 12 mis 6 mis 3 early mis 2 and the global last glacial maximum these can be defined on the basis of esr dating and stratigraphical analysis of the glacial landforms in front of the kuzhaori glacial trough on the southern slope of the haizi shan the outwash terraces in the yazheku river also record four major glacier advances which occurred during mis 16 mis 12 mis 6 and mis 2 in addition the moraines preserved on the southwestern part of the haizi shan suggest that a glacial advance likely occurring during the lateglacial the extent of glaciation on the haizi shan decreased with time

quaternary glacial chronology of the kanas river valley altai mountains china the kanas river originates on the southern slope of youyi peak the largest center of modern glaciation in the altai mountains in central asia glaciers advanced and retreated repeatedly during quaternary glacialeinterglacial cycles in the kanas river valley and four moraine complexes and associated glaciofluvial deposits are preserved in the valley optically stimulated luminescence osl dating has been used to determine ages of glaciofluvial deposits sand lenses sandwiched between tills in moraines using a single aliquot regenerative dose sar protocol based on dating results from this and previous studies including 14 c electron spin resonance esr and osl dates and geomorphic relationships the innermost moraine complex was concluded to deposit during the little ice age lia the second akekule moraine complex was deposited during the neoglacial the third kanas moraine complex was deposited during the last glacial cycle marine oxygen isotope stage mis 2e4 and the outermost set of moraines is mis 6 in ages penultimate glaciation the kanas moraine complex could be divided into three subsets iii1 iii2 and iii3 with inferred ages of mis 2 mid mis 3 and mis 4 respectively which is consistent with moraine records from other areas in central asia and climate reconstructions from the guliya ice core the glaciers in the kanas valley at their maximum extents during the lia neoglacial last glaciation and penultimate glaciation were 13 8 km 32 km w100 km and w120 km long respectively

review of the timing and extent of glaciers during the last glacial cycle in the bordering mountains of tibet and in east asia new accelerator mass spectrometry 14c ams14c electron spin resonance esr and thermoluminescence tl dates for glacial successions in tibetan bordering mountains and in east asia show that glacier extent during the early middle mis3 4 parts of the last glacial cycle was larger than that of the late stage mis2 in last glacial cycle glaciation was not synchronous with the north hemisphere ice sheet maxima and changes in oceanic circulation that predominately control global climate there exist three seasonal precipitation patterns that control the accumulation and ablation on glaciers in the study areas areas dominated by westerlies including the east asia coastal islands experience glacier advance mainly because of increased winter precipitation these glaciers expand during glacial stages in contrast in areas dominated by summer precipitation in the interior of mainland except in the monsoonal high precipitation zone in southeast tibet and the hengduan mountain range tend not to develop large glaciers during major glacial stages

esr dating of glacial tills and glaciations in the urumqi river headwaters tianshan mountains china abstract electron spin resonance esr dating of the shangwangfeng the xiawangfeng and the gaowangfeng tills in the headwaters of the urumqi river was carried out using ge centers in quartz grains the shangwangfeng till is dated at 35 3 5 ka bp three dates from the lower portion of the xiawangfeng till are 171 1 17 176 18 and 184 7 18 ka bp respectively and the age of the gaowangfeng till is 459 7 46 ka bp considering the available ages i e 14 c tl and esr and the principles of geomorphology and stratigraphy the shangwangfeng till is determined to be deposited in marine isotopic stage 2 3 mis2 3 the upper part of the xiawangfeng till was formed in mis4 and the lower part was deposited in mis6 the gaowangfang till is the oldest at the head of the urumqi river corresponding to mis12 the age of the gaowangfang till also demonstrates that the tianshan mountains lay at a suitable altitude for a glacial climate at that time when the glaciers on this segment of the mountain began to develop

late pleistocene lake and glaciation evolution on the northeastern qinghai tibetan plateau a review late pleistocene paleoclimatic history on northeastern qinghai tibetan plateau qtp has been reconstructed mainly from lake sediments however data regarding dry wet climate changes reported in this region are still not clear and controversial based on shoreline features and highstand lacustrine sediments around lakes on the qtp high lake level histories in this paper were summarized and compared with paleoclimatic records from lake sediments ice core and glaciation evolution surrounding mountains on the ne qtp during late pleistocene the results indicate that periods of high lake level occurred at mis 5 mis 3 and early middle holocene and most likely corresponding to warm and wet climate periods while periods of low lake level existed in intervening intervals corresponding to cold and dry climate periods which most likely coincide with glacial advances surrounding high mountains with an exception no wide glacial advance in study area was found during mis 3 possibly suggesting that effective moisture is lower than that in the other region of ne qtp in this period

a preliminary study on timing of the oldest pleistocene glaciation in qinghai tibetan plateau abstract the qinghai tibetan plateau consists of broad planation surfaces basins and mountain ranges research in the past several decades has argued that quaternary glaciations developed only around the high mountains on the plateau not the whole plateau surface in recent years we and other researchers have dated the oldest moraines in several mountain ranges using esr the relative age of these moraines was first confirmed based on their geomorphological position and degree of weathering the results show that the oldest glaciation the zhonglianggan glaciation in the qilian mountains occurred at about 463 ka and the high elevation moraines of the wangfeng glaciation the oldest ones in the tianshan mountains was dated at 477 and 460 ka the oldest glaciation in the hengduan mountains the daocheng glaciation which is characterized by moraines with deeply weathered red soils was dated at 570 ka this is reconfirmed by an age of 590 ka on the oldest moraine at yulong shan in the southern hengduan mountains the wangkun glaciation the oldest in the kunlun shan pass was dated at 710 ka using esr this is similar to the 36cl age of the bottom ice layer of a 309 m ice core of guliya ice cap western kunlun shan these dates of the oldest moraines in several mountain ranges suggest that glaciers began to develop during mis 12 in the qilian and tianshan mountains mis 16 in the hengduan mountains and perhaps mis 18 in the kunlun and nyainqentanglha mountains a widespread rapid uplift of qinghai tibetan plateau kunlun huanghe tectonic movement was determined to have occurred between 1 1 and 0 6 ma thus it is reasonable that uplift of mountain ranges on the tibetan plateau during this time initiated widespread mountain glaciations in ice ages

a review of glacial sequences of the kunlun pass northern tibetan plateau abstract in the kunlun pass area of northern tibet glacial landforms and sediments provide evidence for three major quaternary glaciations esr and tl dating suggest that they date to 600 700 ka wangkun glaciation 260 ka yakou glaciation and 61 13 ka yuzhufeng glaciation the last glacial each glaciation is less extensive than its predecessor the wangkun glaciation is the largest quaternary glaciation the extent of the glaciers during the wangkun glaciation was 3 5 times larger than that of the present glaciers during the last glacial glaciers advanced several times the moraines near the modern glaciers are probably the products of neoglaciation and little ice age

osl dating of glacier extent during the last glacial and the kanas lake basin formation in kanas river valley altai mountains china the kanas river originates on the southern slope of youyi peak the largest center of modern glaciers in altai mountains china three sets of moraines and associated glacial sediments are well preserved near the kanas lake outlet recording a complex history and landscape evolution during the last glacial dating the moraines allows the temporal and spatial glacier shift and climate during the last glacial to be determined and then constrains when and how the kanas lake basin was formed dating of the glacial tills was undertaken by utilizing the optically stimulated luminescence osl method results date four samples from the three sets of moraines to 28 0 34 4 38 1 and 49 9 ka and one sample from outwash sediment to 6 8 ka the kanas lake basin is a downfaulted basin and was eroded by glacier before 28 0 ka and the glacial moraines blocked the glacier melt water after the glacier retreat which made the present day kanas lake eventually form at least before 6 8 ka bp in altai mountains the glacier advance was more extensive in marine isotope stage mis 3 than mis 2 probably because the mid latitude westerlies shifted northward and or intensified during the mis 3 resulting in a more positive glacier mass balance nevertheless the siberian high dominated the altai mountains in mis 2 resulting in a relative decrease in precipitation

plagioclase sub species in chinese loess deposits implications for dust source migration and past climate change plagioclase mineral sub species in the lingtai section in central chinese loess plateau are examined using mineral liberation analyzer techniques showing that loess and paleosol samples exhibit similar patterns in terms of plagioclase feldspar sub species content this suggests that both loess and paleosol units have preserved their primary ca bearing plagioclase compositions of loess source regions weighted average cao in ca bearing plagioclase lies within a narrow range and is equivalent to the average plagioclase composition for upper continental crust this fact supports the hypothesis that chinese loess deposits are the result of a thorough mixing of dust sources the sum of ca bearing plagioclase content exhibits a general increasing trend superimposed by glacial interglacial oscillations in combination with observed plagioclase data in the deserts the variations of ca bearing plagioclase minerals might be used as a proxy for dust source migration and climate changes in the loess source regions furthermore linear relationship between lithogenic magnetic susceptibility ms component input and contents of ca bearing plagioclase in loess units revises a ms proxy for reconstructing paleo monsoon precipitation history the revised ms and plagioclase sub species records help in understanding the mechanism of glaciation across northern tibetan plateau

cenozoic variations in the flux of interplanetary dust recorded by 3he in a deep sea sediment helium 3 concentrations and 3he 4he ratios in modern pelagic sediments are known to be far in excess of terrestrial values as a result of micrometeorite fallout here i report that extraterrestrial helium is easily detected in a pelagic clay core dating back more than 70 myr the remarkable preservation of the extraterrestrial signature arises from high retention of 3he within interplanetary dust particles coupled with loss of radiogenic 4he from terrestrial mineral grains the core provides a continuous record of the fallout of extraterrestrial helium for the cenozoic era this record suggests that there have been significant variations in the influx of interplanetary dust through time probably related to asteroidal breakup events or the passage of comets through the inner solar system the results also show 3he to be a far more sensitive tracer of the interplanetary dust flux than is iridium

quaternary glacial chronology of the ateaoyinake river valley tianshan mountains china abstract the ateaoyinake river originates on the southern slope of the tumur peak the largest center of modern glaciation in the central tianshan mountains in china six sets of moraines and associated glacial sediments are well preserved in the ateaoyinake river drainage recording a complex history of quaternary glacial cycles and landscape evolution dating the landforms allow the temporal and spatial shifts of past cryosphere and climate to be determined dating of the tills and outwashes was undertaken with electron spin resonance esr and optically stimulated luminescence osl two osl ages date outwash and till to 7 3 0 8 ka and 12 3 1 2 ka respectively the esr ages date six sets of moraines to 3 4 ka 14 27 ka 40 54 ka 55 62 ka 134 4 12 6 ka and 219 7 20 5 ka 440 6 41 7 ka if these are correct ages of deposition they suggest that glaciers advanced during the neoglacial and during marine oxygen isotope stages mis 2 3b 4 6 and 12 the mis 3b moraine was created by a glacier nearly as large as or possibly larger than those of the global last glacial maximum of mis 2 the oldest till belongs to the qingshantou glacial stage its single age is consistent with two published esr ages 459 7 46 and 471 1 ka from the gaowangfeng till near the headwaters of the urumqi river in the eastern tianshan mountains these dates suggest that the central and the eastern segments of the tianshan mountains were high enough to be glaciated by mis 12 the geochronology of the glacial landforms in this valley is the first step towards understanding glacial and landscape evolution in this region furthermore this geochronology and previously published geochronology near the headwaters of the urumqi river provide a temporal framework for examining the rates of landscape evolution in the glaciated regions of the tianshan mountains

deep source co2 in natural waters and its role in extensive tufa deposition in the huanglong ravines sichuan china abstract the aqueous geochemistry of huanglong ravine sichuan china where tufa is being deposited extensively is discussed using chemical composition data together with the carbon and oxygen stable isotope ratios the water quality of tufa depositing surface streams in this area is basically controlled by the mixing of two source waters fault bounded spring water and snow and or glacier melt water the spring water contains high concentrations of co 2 supplied via faults the resulting high concentration of dissolved co 2 gives rise to much greater dissolution of carbonate rocks than is usual in karst springs and also to the dissolution of silicate rocks upstream spring waters in the ravine are close to equilibrium with respect to calcite concentrations of dissolved inorganic carbon dic and their 13 c values result from the interaction of about 0 02 mol l 1 co 2 aq of 13 c 3 with carbonate rocks of 13 c 3 under closed system conditions about 70 of the co 2 is estimated to be supplied from the upper mantle the data for all the springs fall in the kaolinite stability field in agreement with observed dissolutional aggressiveness towards na and ca feldspar and that the dissolution rates of these minerals are too slow to move the composition of these waters into the feldspar stability field the dic species in the surface streams are in isotopic equilibrium variations in 13 c dic found at different sites are mainly due to differences in the degree of co 2 degassing from the water there is a linear relationship between 18 o values and the altitude at which samples were collected the oxygen isotope composition of surface stream water in this area is controlled by evaporation water chemistry in daytime and nighttime and daily change of ph in the surface water flowing on the tufa deposition indicate that biological activities contribute to the carbonate precipitation although their extent is not great the daily precipitation rate in this area is estimated to be 4300 kg as caco 3 day 1 over a surface area of 0 9 km 2 i e 0 1 cm year 1

the potential of crinoids as u th sm he thermochronometers abstract u th sm he dating of crinoid fossils from late paleozoic rocks from a variety of sites in north america suggest that this material can be used as a useful low t thermochronometer under certain conditions available data suggest that common he is present in crinoids and at the low production rates typical of calcite this common he will be sufficient to produce spurious ages in crinoid samples of any age heating of samples to temperatures in excess of the opening temperature will expel all he common and radiogenic with all subsequent he accumulation being exclusively radiogenic such samples have potential for being robust thermochronometers sensitive to temperatures in the range of 60 110 c without common he analysts can take advantage of the large size of crinoid columnals and produce reliable ages even when young miocene or with low production rates eu 0 1 ppm samples not subjected to post depositional heating above the opening temperature burial to depths of 2 to 4 km depending on geothermal gradient sedimentation rate and residence time at peak t will likely retain common he and be unsuitable for thermochronologic studies

dating of erosion surface and terraces in the eastern qilian shan northwest china the actively deformed foreland of eastern qilian shan mountains contains well preserved geomorphic features such as erosion surfaces river terraces and tectonically uplifted alluvial fans providing suitable archives for research on regional tectonic activities and palaeoclimatic changes these geomorphic surfaces are well dated by using a combination of magnetostratigraphy electron spin resonance thermoluminescence infra red stimulated luminescence radiocarbon dating and correlation with the well established loess palaeosol sequences of china our results show that the erosion surface formed about 1 4 ma ago and the age of river terraces is 1 24 ma 820 860 ka 780 ka 420 440 ka 230 250 ka 140 ka 60 ka and 10 ka respectively valley incision rates of e 0 09 0 25 m ka 1 have been identified the repetitive stratigraphic and geomorphic pattern of these terraces indicates the fluvial sedimentation incision cycles are tightly associated with the 100 ka glacial interglacial climatic cycles copyright c 2006 john wiley sons ltd

an assessment of the meteoritic contribution to the martian soil the addition of meteoritic material to the mars soils should perturb their chemical compositions as has been detected for soils on the moon anders et al 1973 and sediments on earth kyte and wasson 1986 using the measured mass influx at earth and estimates of the mars earth flux ratio we estimate the continuous planet wide meteoritic mass influx on mars to be between 2700 and 59 000 t yr if distributed uniformly into a soil with a mean planetary production rate of 1 m b y consistent with radar estimates of the soil depth overlaying a bouldered terrain in the tharsis region christensen 1986 our estimated mass influx would produce a meteoritic concentration in the mars soil ranging from 2 to 29 by mass analysis of the viking x ray fluorescence data indicates that the mars soil composition is inconsistent with typical basaltic rock fragments but can be fit by a mixture of 60 basaltic rock fragments and 40 meteoritic material clark and baird 1979 the meteoritic influx we calculate is sufficient to provide most or all of the material required by the clark and baird 1979 model particles in the mass range from 10 7 to 10 3 g about 60 200 m in diameter contribute 80 of the total mass flux of meteoritic material in the 10 13 to 106 g mass range at earth hughes 1978 on earth atmospheric entry all but the smallest particles generally 50 m in diameter in the 10 7 to 10 3 g mass range are heated sufficiently to melt or vaporize mars because of its lower escape velocity and larger atmospheric scale height is a much more favorable site for unmelted survival of micrometeorites on atmospheric deceleration we calculate that a significant fraction of particles throughout the 60 1200 m diameter range will survive mars atmospheric entry unmelted thus returned mars soils may offer a resource for sampling micrometeorites in a size range which is not collectable in unaltered form at earth

tropical climate instability the last glacial cycle from a qinghai tibetan ice core an ice core record from the guliya ice cap on the qinghai tibetan plateau provides evidence of regional climatic conditions over the last glacial cycle 36 cl data suggest that the deepest 20 meters of the core may be more than 500 000 years old the 18 o change across termination i is 5 4 per mil similar to that in the huascaran peru and polar ice cores three guliya interstadials stages 3 5a and 5c are marked by increases in 18 o values similar to that of the holocene and eemian 124 000 years ago the similarity of this pattern to that of ch 4 records from polar ice cores indicates that global ch 4 levels and the tropical hydrological cycle are linked the late glacial stage record contains numerous 200 year oscillations in 18 o values and in dust nh 4 and no 3 levels

landscape analysis of the huang he headwaters ne tibetan plateau patterns of glacial and fluvial erosion the large scale geomorphology of the huang he yellow river headwaters centered around the bayan har shan 5267 m asl in the northeastern part of the tibetan plateau is dominated by an uplifted

timing of glacier fluctuations and trigger mechanisms in eastern qinghai tibetan plateau during the late quaternary abstract it is highly debated whether glacial advances on the qinghai tibetan plateau qtp occurred as a response to temperature cooling or whether they were forced by an increase in moisture brought by the intensive indian summer monsoon we here report a case study investigating this issue multiple moraine series in the yingpu valley queer shan ranges of the hengduan mountains and eastern qtp provide an excellent archive for examining the timing and trigger mechanism of glacier fluctuations twenty seven optically stimulated luminescence osl samples of glacial sediments were collected from this valley the quartz osl ages show that the moraine series of y 1 i m and o were formed during the late holocene late glacial the global last glacial maximum lgm and marine oxygen isotope stage mis 3 likely mid mis 3 the youngest y 2 moraines probably formed during the little ice age lia the oldest h moraines formed before mis 3 we found that glacial advances during the late quaternary at the yingpu valley responded to cold stages or cold events rather than episodes of enhanced summer monsoon and moisture as a result glaciers in the monsoonal hengduan mountains were mainly triggered by changes in temperature millennial time scale temperature oscillations might have caused the multiple glacial advances

tropical snowline changes at the last glacial maximum a global assessment snowline reconstructions from the tropics and subtropics 33 s 33 n at the last glacial maximum lgm have been extracted from a new database which provides information on glacier equilibrium line altitudes elas for over 350 glacier valley localities during the late quaternary about 60 of the intra regional variability observed change in ela ela between the lgm and today is related to headwall altitude reflecting the influence of basin morphometry e g catchment size glacier slope on the response to climate change glacier valley aspect which influences the local patterns of radiation and precipitation also causes intra regional variability in ela although this influence varies greatly between regions overall reconstructed elas are smallest in the himalayas relatively small in the southern central andes and east africa and largest in the northern andes mexico and papua new guinea estimates of the temperature change implied by the range of ela within any one region calculated using the cru 10 modern climate database are consistent with high altitude temperature changes projected from reconstructions of temperature changes at lower altitude sites based in vegetation and geochemical data in the 21 ka tropics data set farrera et al 1999 climate dynamics 15 823 856

geochemistry and mineralogy of travertine deposits of the sw flank of mt etna italy relationships with past volcanic and degassing activity abstract travertine deposits outcropping in the lower sw flank of mt etna were studied for their mapping as well as for their chemical mineralogical and isotopic compositions these deposits are dated to about 24 to 5 ka in the adrano area located at the western limit of the study area in this area travertines show high mg contents and are composed mostly of dolomite thus apparently ruling out any primary deposition in favour of a diagenetic origin travertines outcropping near paterno in the east part of the study area should be younger than 18 ka those located to the ssw of paterno paterno diga show high sr contents and aragonite as dominant mineralogical phase thus suggesting primary deposition those located to the w of paterno paterno simeto stazione are instead poor both in mg and in sr and show calcite as dominant phase carbon isotope composition of travertines indicates a magmatic origin of co2 that formed them based on the estimated volume of travertines between 10 and 20 gg a of co2 were involved in their formation the time span of travertine formation coincided with the eruptive cycles of ellittico and the first part of mongibello which were probably characterised by a greater amount of co2 transported through groundwater circulation widespread travertine deposition probably ceased after the opening of the valle del bove depression that modified the volcanologic and hydrologic conditions in the summit crater area

stratigraphy and palaeoenvironmental implications of pleistocene and holocene aeolian sediments in the lhasa area southern tibet china abstract along the middle and lower reaches of the kyichu river and its tributaries lhasa area southern tibet a multidisciplinary study was carried out in order to investigate the areal distribution sedimentological properties ages and palaeoenvironmental implications of aeolian deposits including intercalated palaeosols this research was initiated to investigate to what extent southern tibet is influenced by past human activity as even recent evaluations perceive the present treeless desertic environment as natural fifteen profiles were recorded at an altitude of 3540 4580 m a s l with subsequent sedimentological geochronological osl ams 14 c and palaeobotanical charcoal analyses sediment properties of both loesses and aeolian sands reveal an origin from aeolian sorting of nearby fluvial deposits the calculated ages are the oldest obtained thus far on aeolian sediments from southern and interior tibet revealing natural aeolian sedimentation before and around the last glacial maximum c 20 ka however a distinct portion of late holocene sandy aeolian sediments also occurs both the evidence for the aeolian dynamics widespread pleistocene loess and aeolian sand deposition local late holocene aeolian sand deposition modern reactivation of widespread pleistocene aeolian sands and the palaeobotanical findings late holocene vegetation change from a tree bearing to a widely treeless landscape provide evidence that the lhasa area was strongly influenced by human activity since at least the late neolithic c 4200 cal yrs bp thus the present day desertic environment might not primarily be a result of the semiarid climate or the high altitude conditions but rather of activities of the humans and their collateral effects however once established this semi natural ecosystem persisted controlled by strong grazing firewood extraction erosion and harsh edaphic conditions preventing the recovery of trees

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

macroscopic and microscopic evidence of quaternary glacial features and esr dating in the daweishan mountain area hunan eastern china whether quaternary glaciers existed in the daweishan mountain area is of great significance to the reconstruction of the quaternary environments in the yangtze valley this study investigated the macroscopic and microscopic features of quaternary glacial features in the daweishan mountain area and applied electron spin resonance esr dating to the clay and gravel sediments to determine their age aster gdem with a resolution of 30 m combined with field investigation recognized the glacial landforms in the daweishan mountain area cirques and firn basins were distinguished using a flat index of f l 2d and a length width ratio of g l w scanning electron microscopy sem identified glacial traces on quartz sand grains of the clay and gravel sediments esr dating of 6 sections showed that the sediments were formed in 2 stages 205 262 ka and 377 425 ka equivalent to the late stage and middle stage of the middle pleistocene respectively there were at least 2 glaciations in the daweishan mountain area in the late stage and middle stage of the middle pleistocene the yangtze valley was influenced by a cold trough and promoted glaciations developed in the daweishan mountain area

accretion rate of extraterrestrial matter iridium deposited 33 to 67 million years ago iridium measured in 149 samples of a continuous 9 meter section of pacific abyssal clay covering the time span 33 to 67 million years ago shows a well defined peak only at the cretaceous tertiary boundary in the rest of the section iridium ranges from a minimum concentration near 0 35 nanograms per gram in the paleocene to a maximum near 1 7 in the eocene between 63 and 33 million years ago the mean iridium accumulation rate is approximately 13 nanograms per square centimeter per million years correction for terrestrial iridium leads to an extraterrestrial flux of9 3 nanograms of iridium per square centimeter per million years and an estimated annual global influx of 78 billion grams of chondritic matter consistent with recent estimates of the influx of dust meteorites and crater producing bodies with masses ranging from 10 13 to 1018 grams combining the recent flux of objects ranging in mass from 106 to 107 grams with the flux of 1014 to 1015 gram objects indicates that the number of objects is equal to 0 54 divided by the radius in kilometers to the 2 1 power periodic comet showers should increase the cometary iridium flux by a factor of 200 to 600 on a time scale of 1 to 3 million years the predicted iridium maxima more than 30 times background are not present in the intervals associated with the cretaceous tertiary boundary or the tektiteproducing late eocene events

quaternary glaciation of the bailang river valley qilian shan abstract the qilian shan on the northeast margin of the qinghai tibetan plateau is weakly influenced by the asian monsoon until recently the quaternary glacial geology of this region has been poorly understood this paper describes a sequence of quaternary glacial deposits in the upper reaches of the bailang river using electron spin resonance esr thermoluminescence tl and radiocarbon dating tills loess buried soils and landforms were dated the oldest till was dated 463 ka bp by esr a younger till and its outwash terrace were dated to 135 and 130 ka bp the loess on this outwash terrace was dated to 141 7 11 4 ka bp at its base and 43 7 3 5 ka bp in its central part by tl dating a buried soil on a younger till was dated at 6920 78 ka bp using 14c the glacial landforms and these dating results show that glacial advances occurred during the little ice age the neoglacial mis 2 4 mis 6 and mis 12 glaciation during mis 12 implies that the qilian mountains were rising coevally with the qinghai tibetan plateau and were probably at a sufficient elevation for glaciation since at least 463 ka bp

late quaternary glacial advances in the eastern qilianshan north eastern tibet as inferred from luminescence dating of fluvioglacial sediments

millennial scale erosion rates in three inland drainage basins and their controlling factors since the last deglaciation arid china abstract in the regions surrounding the qinghai tibet plateau changes in erosion rates have been linked to the tectonics climate and topography over different time scales to understand the mechanisms governing the changes of erosion rates it is important to study erosion rates by different methods and for different time scales in inland drainage basins deposition rates of terminal lake sediments can indicate basin wide erosion rates at the millennial scale this paper presents three lake records of the last deglaciation and holocene huahai lake zhuye lake and yanchi lake from the hexi corridor north of the qilian mountains in arid china organic matter terrestrial pollen concentrates seeds grasses and plant debris are used for conventional and ams 14 c dating on the basis of 66 radiocarbon dates lithology and grain size we infer relatively high basin wide erosion rates during the last deglaciation and early holocene in the three drainage basins when the three lake sediments were seriously affected by reworking the deposition rates were an order of magnitude or greater in these lakes during the last deglaciation and early holocene than during the mid to late holocene during the transition period of the last glacial interglacial cycle significant climatic changes occurred in east and central asia corresponding to the strengthening of the asian summer monsoon and to increasing effective moisture in arid central asia which can have strong impacts on basin wide erosion rates north of the qinghai tibet plateau moreover melting glaciers in the qilian mountains probably also contributed to the high basin wide erosion rates at the same time tectonic activity was not recognizable in the study area during that period in the arid and semiarid regions surrounding the qinghai tibet plateau dramatic changes in erosion rates appear during the transition periods of the glacial interglacial cycles which illustrate the climatic controls on erosion rates at this time scale

re evaluation of mis 3 glaciation using cosmogenic radionuclide and single grain luminescence ages kanas valley chinese altai previous investigations observed a period of major glacial advances in central asia during marine oxygen isotope stage mis 3 57 29 ka out of phase with global ice volume records we have re ex

optically stimulated luminescence dating of a moraine and a terrace in laohugou valley western qilian shan northeastern tibet the qilian shan is one of the most important mountain ranges for understanding quaternary glaciation in the northeastern tibetan plateau however its western part is not well studied a moraine and an outwash terrace in the laohugou valley were mapped using geomorpho stratigraphy and dated by optically stimulated luminescence after analyzing the minimum age and central age of coarse and fine grained quartz most of the minimum ages for coarse grains are consistent with geomorpho stratigraphic sequence indicating they are closest to the true ages of the sediments the lateral moraine was initially formed at 20 2 2 6 ka during the last glacial maximum and was modified between 11 6 2 0 and 12 9 1 3 ka in the late glacial the outwash terrace was formed between 10 0 1 7 and 5 5 0 7 ka and coincides with temperature rise in the early holocene and the holocene optimum at its last glacial maximum the palaeo glacier was similar to 13 6 km long with an area of 45 3 km 2 4 3 km longer and 34 larger than the contemporary glacier the reconstructed palaeo glacier equilibrium line altitude ela was 4600 40 m or 140 m lower than the present ela the glacier advance in the laohugou valley was less extensive and ela depression was less than found in the eastern qilian shan during lgm and late glacial suggesting a drier climate during the last glacial c 2013 elsevier ltd and inqua all rights reserved

late quaternary glaciation in the kyrgyz tien shan the tien shan of kyrgyzstan contains multiple moraines and drift from late quaternary glaciations the spatial temporal distribution of the glaciers inferred from the moraines suggests that the main factor controlling glacier advance here was the availability of moisture the dominant modern climatic signatures in northern central asia include orographic thunderstorms in summer cold and dry siberian high pressure cells in winter and westerly cyclonic storms from the north atlantic and eastern mediterranean in spring and fall changes in any of these systems during the late quaternary would have varied precipitation delivery to and glacier growth in the kyrgyz tien shan geomorphic mapping and reconnaissance level 10be cosmic ray exposure dating of moraine sequences in six drainages indicate that there were multiple maximum advances of similar extents and equilibrium line depressions across the range glaciers in the north and east of the kyrgyz tien shan last advanced to their maximum positions during marine oxygen isotope stage mis 5 and again during mis 4 while in the south and west of the range advance occurred during mis 3 in contrast to maritime europe and north america there is no evidence of a major glacial advance during mis 2 glacier advances during mis 2 and since were restricted to the vicinity of modern glaciers allowing the older glacial record to be preserved well