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

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

timing of late quaternary glaciations in the himalayas of northern pakistan optically stimulated luminescence dating of late quaternary glaciogenic sediments was undertaken in critical areas of the himalayas of northern pakistan in order to examine the timing of glaciation the dates demonstrate that several glaciations occurred during the last glacial cycle in swat the grabral 2 stade and the kalam i stade were dated at ca 77 ka and ca 38 ka respectively the error on the former date is large and it is conceivable that the moraines may have formed during the early part of oxygen isotope stage 3 rather than during oxygen isotope stage 4 the kalam i stade however clearly represents a glaciation during oxygen isotope stage 3 the oldest moraines and those at the lowest altitude in the indus valley at shatial have an age of ca 60 ka these also relate to a major glacial advance during oxygen isotope stage 3 a younger series of moraines the jalipur tillite and glaciofluvial sands at liachar in the indus valley and moraines at rampur tarshing have ages of ca 27 ka ca 21 23 ka and ca 15 ka respectively these dates show that glaciers also occupied parts of the indus valley during oxygen isotope stage 2 these dates and the morphostratigraphy show that glaciation in the pakistani himalaya was more extensive during the early part of the last glacial cycle and that the local last glacial maximum in pakistan was asynchronous with the maximum extent of northern hemisphere ice sheets copyright 2000 john wiley sons ltd

reconstruction of the late quaternary glaciation of the macha khola valley gorkha himal nepal using relative and absolute 14c 10be dendrochronology dating techniques abstract late quaternary glacier fluctuations in the macha khola valley gorkha himal nepal were reconstructed using relative and absolute dating techniques our results indicate that younger moraine complexes were left by late holocene

a 13 000 year climate record from western tibet although the tibetan plateau is important in influencing the atmospheric circulation of the northern hemisphere1 3 there are only a few continuous palaeoclimate records available and these are limited to the plateau s northeastern margin4 6 here we present a 13 000 yr record from sumxi co western tibet constructed from both lake core and shoreline studies which shows that conditions in the early middle holocene were warmer and wetter than at present these results confirm model predictions of an intensified monsoon over the region at 9 000 yr bp owing to an orbitally induced increase in summer insolation7 8 we also find evidence for warm humid pulses at 12 500 and 10 000 yr bp in phase with the steps of the last deglaciation and for a return to cold dry conditions at 11 10 000 yr bp none of which can be explained by orbital variations the existence of the cold episode confirms that the cooling associated with the younger dry as event occurred in continental china6 9 and provides further evidence of the global nature of this event10

hf isotope geochemistry of the galapagos islands 1 we report 176hf 177hf ratios determined by multicollector inductively coupled plasma mass spectrometry on 49 basalts from the galapagos islands the hf values range from about 8 a value typical of many oceanic island basalts to about 15 a value typical of mid ocean ridge basalt the hf shows the expected correlation with nd and inverse correlations with sr and pb isotope ratios the range of values and correlations observed is consistent with galapagos mantle plume asthenosphere mixing inferred from previous geochemical studies while oceanic island basalt isotopic arrays suggest that multicomponent mixing is common in the sources of such basalts the galapagos is unusual in that depleted upper mantle appears to be a principal component thermal and dynamic interaction between the galapagos mantle plume and the lithosphere and shallow asthenosphere is the most likely cause of mixing and of the geographic pattern of geochemical variation the galapagos hf nd sr pb isotopic array diverges toward the plume end indicating the plume is heterogeneous this heterogeneity is geographic with distinct northern central and southern components the central component and to a lesser degree the northern component are compositionally similar to the common component of plumes variously called phem fozo and c while the southern component is unique with relatively high hf and 206pb 204pb compared to 87sr 86sr and nd

reconstruction of the 2 4 million km2 late pleistocene ice sheet on the tibetan plateau and its impact on the global climate during 20 expeditions new data were obtained on the maximum extent of glaciation in tibet and the surrounding mountains evidence was found of moraines at altitudes as low as 460 m on the southern flank of the himalayas and 2300 m on the northern slope of the tibetan plateau in the qilian shan on the northern slopes of the karakorum aghil and kuen lun moraines occurred as far down as 1900 m in southern tibet radiographic analyses of erratics document former ice thicknesses of at least 1200 m glacial polishing and knobs in the himalayas and karakorum are proof of glaciers as thick as 1200 2000 m on the basis of this evidence a 1100 1600 m lower equilibrium ela line was reconstructed for the ice age which would mean 2 2 4 million km2 of ice covering almost all of tibet since the equilibrium ela line was far below the average altitude of tibet on mount everest and k2 radiation was measured up to 6650 m yielding values of 1200 1300 w m2 because of the subtropical latitude and the high altitude solar radiation in tibet is 3 4 times greater than the energy intercepted between 60 and 70 n or s with an area of 2 2 4 million km2 and an albedo of 90 the tibetan ice sheet caused the same heat loss on the earth as a 6 9 6 million km2 sized ice sheet at 60 70 n because of its proximity to the present day equilibrium ela line tibet must have undergone large scale glaciation earlier than other areas being subject to intensive radiation the tibetan ice must have performed an amplifying function during the onset of the ice age

extent and spatial distribution of pleistocene glaciations in eastern tibet as a contribution to the controversial discussion regarding the nature and extent of the pleistocene glaciation on the tibetan plateau additional observations and results were obtained during several chinese german joint expeditions in the investigation area of the eastern and central tibetan plateau it will be shown that the maximum extent of the last glaciation was limited to the glaciation of isolated mountain groups or smaller plateau glaciations these glaciations are characterized by glacial erosional features such as u shaped valleys in the inner mountain massifs and cirques in the higher summit areas accumulation forms such as terminal and lateral moraines less common than basal moraines are marked by granitic and basaltic erratics using two examples from the eastern margin of the tibetan plateau nianbaoyeze shan and northern chola shan the extent of pleistocene glaciations can be mapped by the distribution of terminal and lateral moraines and erratic granite boulders on the slopes of the surrounding schists two to three main pleistocene glaciations can be separated using weathering criteria paleosols and the overlying stratum on the moraines and associated terrace sequences overlying stratum consist of aeolian sandy silt or solifluction debris the younger moraines are found to be characterized by large erratics were therefore named big boulder moraine and can be found over the investigated area the ice free areas are characterized by pleistocene terraces along the main rivers loess deposits with sand and ice wedges at higher elevations e g the basin of zoige and paleosols in the basins below 3500 m a s l e g aba basin or garze basin the hypothesis of an extensive plateau glaciation could not be verified for this region a rising snowline equilibrium line altitudes elas is revealed in two cross sections during the last glacial maximum lgm at the eastern and northern margin of the tibetan plateau snowlines migrated from about 4000 m in the east minshan to 4300 m in the nianbaoyeze and to about 4700 m in the west bayan har shan a rise was also recorded from about 3800 m in the north central qilian shan up to a range of 4300 4950 m different exposures in the kunlun shan to approximately 5200 m in the tanggula shan in the center of the tibetan plateau the general increase of modern and lgm snowlines or elas towards the plateau corresponds with a decrease of precipitation from east to west and from north to south respectively precipitation was more pronounced at the eastern margin during glacial times than compared to present

holocene glacier fluctuations a global overview of glacier advances and retreats grouped by regions and by millennia for the holocene is compiled from previous studies the reconstructions of glacier fluctuations are based on 1 mapping and dating moraines defined by 14 c tcn osl lichenometry and tree rings discontinuous records time series and 2 sediments from proglacial lakes and speleothems continuous records time series using 189 continuous and discontinuous time series the long term trends and centennial fluctuations of glaciers were compared to trends in the recession of northern and mountain tree lines and with orbital solar and volcanic studies to examine the likely forcing factors that drove the changes recorded a general trend of increasing glacier size from the earlyemid holocene to the late holocene in the extra tropical areas of the northern hemisphere nh is related to overall summer temperature forced by orbitally controlled insolation the glaciers in new zealand and in the tropical andes also appear to follow the orbital trend i e they were decreasing from the early holocene to the present in contrast glacier fluctuations in some monsoonal areas of asia and southern south america generally did not follow the orbital trends but fluctuated at a higher frequency possibly triggered by distinct teleconnections patterns during the neoglacial advances clustered at 4 4e4 2 ka 3 8e3 4 ka 3 3e2 8 ka 2 6 ka 2 3e2 1 ka 1 5e1 4 ka 1 2e1 0 ka 0 7e0 5 ka corresponding to general cooling periods in the north atlantic some of these episodes coincide with multidecadal periods of low solar activity but it is unclear what mechanism might link small changes in irradiance to widespread glacier fluctuations explosive volcanism may have played a role in some periods of glacier advances such as around 1 7e1 6 ka coinciding with the taupo volcanic eruption at 232 5 ce but the record of explosive volcanism is poorly known through the holocene the compilation of ages suggests that there is no single mechanism driving glacier fluctuations on a global scale multidecadal variations of solar and volcanic activity supported by positive feedbacks in the climate system may have played a critical role in holocene glaciation but further research on such linkages is needed the rate and the global character of glacier retreat in the 20th through early 21st centuries appears unusual in the context of holocene glaciation though the retreating glaciers in most parts of the northern hemisphere are still larger today than they were in the early and or mid holocene the current retreat

local and regional controls on the lateral emplacement of the ben hiant dolerite intrusion ardnamurchan nw scotland abstract sub volcanic and related satellite intrusions record the delivery storage and accommodation of magma before eruption however when several volcanic centres are in close proximity the relationship between centre and satellites may be ambiguous here we examine the structure of the ben hiant dolerite satellite intrusion discuss its relationship with the ardnamurchan central complex located 2 km to the northwest and explore the possibility of a genetic connection with the next nearest centre the mull central complex 35 km to the southeast structural field observations and anisotropy of magnetic susceptibility ams fabric analyses reveal that the ben hiant dolerite was emplaced as a series of lobes in a sequence of stacked sheets the ams fabric data further indicate that the ben hiant dolerite intruded laterally and may have been sourced from either the ardnamurchan central complex or the mull central complex testing either model and discriminating between these two possible source reservoirs remains an outstanding challenge however the potential implications of the lateral movement of magma over many 10 s of kilometres between upper crustal magmatic centres suggests hidden complexities associated with volcanic plumbing systems that must be tested structurally as well as geochemically

cosmogenic radionuclide dating of glacial landforms in the lahul himalaya northern india defining the timing of late quaternary glaciation the timing of glaciation in the lahul himalaya of northern india was ascertained using the concentrations of cosmogenic 10be and 26al from boulders on moraines and drumlins and from glacially polished bedrock surfaces five glacial stages were identified sonapani i and ii kulti batal and chandra of these cosmogenic exposure ages were obtained on samples representative of the batal and kulti glacial cycles stratigraphical relationships indicate that the sonapani i and ii are younger no age was obtained for the chandra glacial advance batal glacial stage deposits are found throughout the valley indicating the presence of an extensive valley glacial system during the kulti stage glaciers advanced ca 10 km beyond their current positions moraines produced during the batal stage ca 12 15 5 ka are coeval with the northern hemisphere late glacial interstadial bolling allerod deglaciation of the batal glacial stage was completed by ca 12 ka and was followed by the kulti glacial stage during the early holocene at ca 10 11 4 ka on millennial time scales glacier oscillations in the lahul himalaya apparently reflect periods of positive mass balance coincident with times of increased insolation during these periods the south asian summer monsoon strengthened and or extended its influence further north and west thereby enhancing high altitude summer snowfall copyright 2001 john wiley sons ltd

the quaternary glacial history of the zanskar range north west indian himalaya abstract three glacial stages and a minor advance are recognised from the zanskar range of the north western indian himalaya a glaciated palaeosurface 280 m above river level a r l with associated erratics represents the oldest and most extensive glaciation the chandra stage this ice covered a landscape of broad gentle valleys probably as an ice cap with an erratic distribution indicating that the ice shed lay to the south over the high himalaya a change in valley form from broad glacial troughs to narrow v shaped gorges along with large subdued moraine ridges delimits a separate later extensive valley glaciation the batal stage with its maximum at 78 0 12 3 ka bp distinct sets of moraine ridges represent a less extensive younger glaciation the kulti stage which dates close to the global last glacial maximum a minor advance the sonapani is represented by sharp crested moraine ridges within 2 km of current ice bodies possibly belonging to the little ice age glacier elevation indexes geis calculated for this and adjacent areas show a rise in elevation from the south west to the north east but dip again to the indus valley for both the batal and kulti stages reflecting attenuation of the south westerly monsoon and possible channelling of westerly depressions along the broad upper indus valley gei depression are 500 and 300 m for the batal and kulti stages respectively the change in extent and style from the chandra stage to the later glaciations may be related to uplift of more southerly ranges blocking monsoon precipitation and incision of the landscape such that ice reached lower altitudes over shorter horizontal distances why ice extent was greater during oxygen isotope stage ois 4 than 2 is not clear although recent high resolution plaeomonsoon records show complex peaks in monsoon intensity and it is possible that there was a more favourable combination of precipitation and temperature earlier rather than later during the last glaciation

pedogenic studies in eastern nepal new aspects about the last glaciation abstract soil development of high mountain soils was studied in eastern nepal with regard to new aspects about the quaternary history of landscape and climate the soils were developed in quaternary glacial deposits i e the lowest clearly identified terminal and lateral moraines of 5 high valleys of the khumbu and solu region all located between 3800 and 4300 m asl particle size analysis pedogenic iron oxides and weathering indices were used to obtain information on soil development of the different sites except for one site no significant differences were found in the extent of soil development indicating that all soils and their corresponding glacial deposits are of similar relative age in combination with recently published numerical datings of the terminal moraines in one of the high valleys the age of the deposits could be narrowed down partly correcting former findings the maximum extent of the last glaciation if accepted as more or less synchronous to the global last glacial maximum was less pronounced than previously assumed however morphological and pedological findings give evidence of an early phase of late pleistocene glaciation further down valley corresponding to new results from high asia the japanese alps north siberia and the kamchatka peninsula

the role of the indian summer monsoon and the mid latitude westerlies in himalayan glaciation review and speculative discussion new dates for late quaternary glaciations in the himalayas show that during the last glacial cycle glaciations were not synchronous throughout the region rather in some areas glaciers reached their maxima at the global glacial maximum of c 18 20 ka bp whereas in others glaciers were most extensive at c 60 30 ka bp comparison of these data with palaeoclimatic records from adjacent regions suggest that on millennial timescales himalayan glacier fluctuations are controlled by variations in both the south asian monsoon and the mid latitude westerlies

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

combined use of relative and absolute dating techniques for detecting signals of alpine landscape evolution during the late pleistocene and early holocene article i nfo a combination of three relative and two absolute numerical dating techniques applied on nine soil profiles in an alpine environment located in val di rabbi trentino northern italy was used to improve the investigation methodology of alpine sites in response to climate change and to reconstruct the chronology of late pleistocene and early holocene landscape evolution the degree of podzolisation clay mineral evolution and the element mass balances of each site were investigated furthermore the stable fraction of the soil organic matter som was extracted with 10 h2o2 and 14 c dated the age of the organic residues was compared with the age of charcoal fragments found in one of the studied soils and with the age of rock boulders obtained by surface exposure dating sed with cosmogenic 10 be numerical dating and weathering characteristics of the soils showed a fairly good agreement and enabled a relative and absolute differentiation of landscape elements the combination of 14 c dating of som and sed indicated that deglaciation processes in val di rabbi were already far advanced by around 14000 cal bp and that glacier oscillations affected the highest part of the region until about 9000 cal bp the development of clay minerals is time dependent and reflects weathering intensity we found a close link between secondary clay minerals like smectite or vermiculite and soil age as obtained by the dating of the organic residues after the h2o2 treatment calculated element mass balances strongly correlated with the ages derived from 14 c measurements old soils have lost a major part of base cations up to 75 compared to the parent material fe and al which indicates a continuous high weathering intensity results of the chemical and mineralogical analyses were in good agreement with numerical dating techniques showing the dynamics of an alpine landscape within a relatively small area the combination of relative and absolute dating techniques is a promising tool for the reconstruction of landscape history in high elevation alpine areas on siliceous substrates

on the problem of quaternary glaciations and the extent and patterns of pleistocene ice cover in the qinghai xizang tibet plateau abstract data accumulated during investigations since the 1960s indicate that up to four pleistocene glaciations can be recognized in the qinghai xizang tibet plateau and the adjacent himalaya mountains in order of decreasing age these are the xixabangma nyanyaxungla guxiang and baiyu glacial episodes the history of pleistocene glacial evolution in various areas throughout the plateau differs and the pattern is very complex throughout the early pleistocene the elevation of the qinghai xizang plateau was approximately 2000 m above sea level during the xixabangma glacial episode recorded at higher elevations the climate and topographical conditions on the plateau were largely unfavourable for the development of glaciers present investigations have revealed that the oldest till is only found at isolated localities on the plateau glaciofluvial or alluvial deposits such as the gongba conglomerate dating from 2 4 to 0 73 ma bp and the fluvial lacustrine deposits of the qiantang group dating from 2 4 to 1 7 ma bp are present rather than glacial till therefore the postulate of a large early pleistocene ice sheet proposed previously has been disproves during the most recent glaciation uplift of the plateau and the himalayas continued the majority of the qinghai xizang plateau reached 4000 m a s l and the great himalaya were approximately 6000 m a s l the mountains formed a barrier against the incursion of the indian monsoon so that precipitation decreased sharply on the northern flank of the himalayas and the climate to the north became cold and dry all of the glaciers on the qinghai xizang plateau underwent extensive retreat thus during the pleistocene no unified glacial cover existed over the qinghai xizang plateau similarly the source area of the hwang he yellow river did not support a local ice sheet

controversy regarding the existence of a large ice sheet on the qinghai xizang tibetan plateau during the quaternary period

geophysics mediating plate convergence movement of earth s tectonic plates generates low frequency seismic events these events are not background noise but represent slower and deeper earthquakes

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

timing of late quaternary glaciations south of mount everest in the khumbu himal nepal moraines south of mount everest in the khumbu himal were dated using optically stimulated luminescence clustering of ages and morphostratigraphy allowed three advances to be dated 1 the periche glacial stage ca 18 25 ka 2 the chhukung glacial stage ca 10 ka and 3 the lobuche stage ca 1 2 ka the periche stage is coincident with oxygen isotope stage 2 the chhukung stage represents a late glacial or early holocene glacial advance and the lobuche stage is a late holocene glacial advance that predates the little ice age

reconstruction of climate and landscape changes in a high mountain lake catchment in the gorkha himal nepal during the late glacial and holocene as deduced from radiocarbon and compound specific stable isotope analysis of terrestrial aquatic and microbial biomarkers abstract we present both conventional proxies total organic carbon and n 14 c 13 c 15 n and compound specific stable isotope data for terrestrial aquatic and microbial biomarkers combined with an in depth interpretation of their environmental meaning for a sediment core from lake rukche at 3500 m a s l in the gorkha himal nepal a region with a paucity of palaeoclimate data compound specific 13 c values of terrestrial sugars and n alkanes indicate a predominance of c 4 grasses during the late glacial while the holocene was dominated by c 3 vegetation

early ordovician orogenic event in galicia nw spain evidence from u pb ages in the uppermost unit of the ordenes complex new u pb data zircon monazite and rutile obtained from rocks of the uppermost allochthon in the variscan belt of nw spain indicate that the hangingwall to the suture includes an allochthonous unit with a pre variscan tectonothermal evolution this evolution is characterised by an early ordovician 498 500 ma bimodal magmatism followed almost immediately 493 498 ma by a barrovian style metamorphism up to the granulite facies the metamorphism subsequent to the igneous intrusions requires convergence and crustal thickening in order to generate the barrovian facies pattern shown by the lithologies of the uppermost allochthon the almost coeval magmatism and metamorphism and the chemistry of the metabasites suggest an accretionary complex probably related to a volcanic arc as the most probable setting for the origin of the uppermost unit the implications of the existence of early ordovician convergent plate boundaries are discussed in the context of gondwana laurentia avalon interactions

a note on the extent of glaciation throughout the himalaya during the global last glacial maximum abstract quantitative chronologies for the impressive glacial successions that occur throughout the himalaya have until recently been almost totally lacking within the last decade two new techniques have promised to remedy this situation these techniques optically stimulated luminescence and cosmogenic nuclide surface exposure dating enable the age of many glacial features to be determined and have allowed us to study the extent and timing of himalayan glaciation in the late quaternary new data show that the local last glacial maximum lgm occurred during the early part of the last glacial cycle in most areas during marine isotope stage 3 mis 3 mis 3 was a time of increased insolation when the south asian summer monsoon strengthened and penetrated further north into the himalaya the concomitant increased precipitation occurring as snow at high altitudes produced positive glacier mass balances thereby allowing glaciers to advance on the other hand during the global lgm 18 24 ka himalayan glaciation was very restricted in extent generally extending

asynchronous maximum advances of mountain and continental glaciers the last maximum glacier advance in many mountain ranges appears to have predated the last maximum advance of the wisconsinan continental ice sheets 20 000 years b p published evidence from widely spaced localities in north and south america europe asia and hawai i suggests that some mountain glaciers extended farther during one or more stades early in the last glaciation roughly 115 000 30 000 years b p than at its end when low global temperature and high precipitation presumably were most favorable for the growth of glaciers variations in the timing of glacier advances in different mountain ranges suggest that alpine glaciers are dependent on regional climate as well as global conditions their study might provide sensitive tests for theories of global climate change glacial deposits are often used as time markers in neotectonic and geomorphic studies and their ages sometimes are inferred from distant measurements or from proxy histories of global climate change undated geomorphic features such as moraines sharply incised streams and river terraces which commonly have been associated with the last maximum glacier advance 20 000 years b p or last deglaciation 13 000 years b p may actually be older by a factor of 2 to 4 or more conversely deposits assigned to the maximum advances of the penultimate global glaciation 130 000 years b p may actually date from early in the most recent glacial cycle and be younger by a comparable factor rates of faulting or folding estimated from displacements or deformation and the assumed ages of such geomorphic features might be too great or too small by corresponding factors

pleistocene paleoenvironmental changes in the high mountain ranges of central china and adjacent regions abstract during several joint chinese german expeditions the quaternary landscape and paleoclimatic evolution of the mountain ranges and grabens surrounding the loess plateau of central china was studied the results are compared with proxy data from the interior loess plateau to help reconstruct atmospheric circulation during late pleistocene times middle to late pleistocene alluvial terraces and fans capped with loess units and paleosols show that aggradational episodes correlate with periods of glaciation and increased loess accumulation in turn degradation correlates with interglacials or interstadials and increased soil formation this implies that climate is the primary control on quaternary paleohydrology and alluvial sedimentation and erosion the high mountains which barely reached the last glacial ela were only glaciated during the most favourable climatic period of glaciation the glaciation the glacial and alluvial forms point to a cool early to maximum glacial period with increased precipitation and to a maximum to final period with cold dry conditions during the last glaciation the maximum advance of the small glaciers took place towards the end of a relatively humid and cold period between ca 32 and 23 ka the following dry cold stage between ca 23 and 13 ka was rather unfavourable for glacial advance proxy data from the loess plateau supports the view that glaciations were more or less dominated by cold dry winter monsoon climate whereas during the interglacial interstadials a warmer and more humid climate prevailed implying a strengthening of the summer monsoon influence the results prove variations of the monsoon that in turn modulates paleohydrology periglacial dynamics glacier advances dust flux and soil formation

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

an alternative emplacement model for the classic ardnamurchan cone sheet swarm nw scotland involving lateral magma supply via regional dykes abstract sub volcanic intrusive networks of which cone sheets are recognised as a major constituent partially control volcano growth and eruption style the accepted cone sheet model is that these confocally dipping intrusions originate from an unexposed central magma chamber through dip parallel magma flow however the emplacement mechanism of cone sheets remains poorly understood the 58 ma cone sheet swarm of ardnamurchan nw scotland offers an excellent opportunity to further resolve the emplacement dynamics of cone sheets through studying magma flow and their importance in volcanic edifice construction structural measurements and anisotropy of magnetic susceptibility ams analyses have constrained a lateral magma flow pattern consistently oriented nw se in the majority of the ardnamurchan cone sheets field observations also highlight the importance of host rock structure and interference between competing local and regional stress fields in controlling intrusion geometry our observations suggest cone sheet formation may be linked to laterally propagating nw se trending regional dykes sourced from laterally adjacent magmatic systems likely the palaeogene mull central complex which are deflected around the central complex by stress field interference implicitly edifice construction and potential eruption precursors observed at a volcano may instigate or result from magmatic activity in laterally adjacent volcanic systems

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

correction of in situ cosmogenic nuclide production rates for geomagnetic field intensity variations during the past 800 000 years we present integrated relative production rates for cosmogenic nuclides in rock surfaces which take into account reported variations of the geomagnetic field intensity during the past 800 000 yr the calculations are based on the model simulating cosmic ray particle interactions with the earth s atmosphere given by masarik and beer simulation of particle fluxes and cosmogenic nuclide production in the earth s atmosphere j geophys res 104 d10 12099 12111 1999 corrections are nearly independent on altitude between sea level and at least 5000 m the correction factors are essentially identical for all stable and radioactive cosmogenic nuclides with half lives longer than a few hundred thousand years at the equator integrated production rates for exposure ages between 40 000 to 800 000 yr are 10 to 12 higher than the present day values whereas at latitudes 40 geomagnetic field intensity variations have hardly influenced in situ cosmogenic nuclide production correction factors for in situ 14c production rates differ from those of longer lived nuclides they are always smaller than 2 because the magnetic field intensity remained rather constant during the past 10 kyr when the major fraction of the 14c extant today was produced

deglaciation and landscape history around annapurna nepal based on 10be surface exposure dating abstract the high himalaya is a key area for tectonic geomorphological and climate studies because of its extreme relief and location at the transition zone between areas with abundant monsoonal precipitation and the arid semiarid tibetan plateau we present 10be surface exposure ages on 22 boulders from the annapurna area in nepal the ages improve understanding of the late quaternary landscape history and the geomorphological processes operating in this part of the himalaya although our study is reconnaissance in nature it highlights the importance of catastrophic events such as landslides and debris flows for denudation of high mountains holocene exposure ages for the dhampu chooya landslide 4 1 0 6 ka and for 600 m of alluviation in kali gandaki valley 2 1 0 6 ka for example indicate the frequent occurrence and extent of catastrophic events and their implications for natural hazards we also offer an explanation for the differences in late quaternary glacial chronologies at closely spaced study sites in the nepal himalaya topographically controlled and spatially variable precipitation in the himalaya determines the sensitivity of glaciers to changes in temperature and precipitation accordingly some glaciers advanced in phase with northern hemisphere ice sheets whereas others reached their maximum extent at times of increased monsoonal precipitation during marine isotope stage 3 and the early holocene

the sequence of quaternary glaciation in the bayan har mountains four periods of quaternary glaciation in the pleistocene have been found in the area of the bayan har mountains they represent respectively the two stages of the last glacial age the penultimate ice age and an earlier ice age during the late stage of the last glacial age glaciers developed only near the mountain ridges of the bayan har in the earlier stage glaciers expanded down to the piedmont of the bayan har mountains and were as much as 40 km long in the penultimate ice age an extensive ice cover developed depositing an areally widespread till sheet erratics were transported 60 km from bayan har peak to qingshuihe town to the south and to yematan land to the north granitic erratics are also distributed over elevated geomorphological positions such as chalaping ridge the area of ice cover encompassed up to 50 000 km2 furthermore evidence including glacial landforms and sediments shows that a larger glaciation existed in this area in an earlier time possibly during the third most recent ante penultimate glaciation the scale of this glaciated area is greater than those of the more recent events in the qinghai xizang plateau extending over 80 000 km2 this glaciation covered the source area of the yellow river from xingsuhai in the west to duogerangtan in the east including the areas of gyaring and ngoring lakes based on the extent and locations of the glaciations the bayan har stage and galalahai stage of the last glacial age the yematan ice age and the huanghe glacial age can be recognized

geomagnetic poles over the past 10 000 years locations of the geomagnetic pole over the past 10 000 years have been calculated by averaging the vgp positions obtained from paleomagnetic data the distribution of the geomagnetic pole was elongated to the direction parallel to the meridian of 45 and 225 longitude and westward movement of the pole was predominant throughout this period the time sequence of the polar motion can be divided into three intervals the intervals between ca 10 000 b p and ca 7000 b p between ca 7000 b p and ca 3700 b p and between ca 3700 b p and the present during the period between ca 7000 and ca 3700 b p the range of the movement of the geomagnetic pole was limited within 5 degrees around the geographical pole before and after this period the movement was very active fluctuating over 10 degrees the results of the last 2000 years show good consistency with the geomagnetic pole calculated from archaeomagnetic data by merrill and mcelhinny 1983

illegitimate magmas of the galapagos insights into mantle mixing and magma transport roughly 1 2 of the flows erupted from flank vents of the western galapagos shield volcanoes have anomalous compositions we call these illegitimate magmas because of their uncertain parentage because some illegitimate magmas are compositionally indistinguishable from lavas of an adjacent volcano and erupt from the flank facing the adjacent volcano such magmas apparently result from lateral intrusion of magma from the adjacent volcano other illegitimate magmas come from parts of the galapagos plume that have incompletely mixed or result from unusually advanced melting of part of the mantle

mass balance and equilibrium line altitudes of glaciers in high mountain environments abstract the mass balance characteristics of glaciers in high mountain environments complicate the relationship between glacier equilibrium line altitudes elas and climatic variables such as precipitation and air temperature therefore methods of ela reconstruction employed in low relief environments are commonly not applicable in high mountains or require some modification we review the concept of the ela with reference to the mass balance of a range of glacier types found in high mountain regions we examine the applicability of several commonly used methods of ela reconstruction for different glacier types and propose some general principles to guide the choice of appropriate methods

comparison of late pleistocene and modern glacier extents in central nepal based on digital elevation data and satellite imagery abstract late pleistocene and modern ice extents in central nepal are compared to estimate equilibrium line altitude ela depressions new techniques are used for determining the former extent of glaciers based on quantitative objective geomorphic analyses of a 90 m resolution digital elevation model dem for every link of the drainage network valley form is classified as glacial or fluvial based on cross valley shape and slope statistics down valley transitions from glacial to fluvial form indicate the former limits of glaciation in each valley landsat multispectral scanner imagery for the same region is used to map current glacier extents for both full glacial and modern cases elas are computed from the glacier limits using the dem and a toe to headwall altitude ratio of 0 5 computed ela depressions range from 100 900 m with a modal value of 650 m and a mean of 500 m values consistent with previously published estimates for the central himalaya but markedly smaller than estimates for many other regions we suggest that this reflects reduced precipitation rather than a small temperature depression consistent with other evidence for a weaker monsoon under full glacial conditions

wolf volcano galapagos archipelago melting and magmatic evolution at the margins of a mantle plume wolf volcano an active shield volcano on northern isabela island in the galapagos archipelago has undergone two major stages of caldera collapse with a phase of partial caldera refilling between wolf is a typical galapagos shield volcano with circumferential vents on the steep upper carapace and radial vents distributed in diffuse rift zones on the shallower sloping lower flanks the radial fissures continue into the submarine environment where they form more tightly focused rift zones wolf s magmas are strikingly monotonous estimated eruptive temperatures of the majority of lavas span a total of only 22 c this homogeneity is attributed to buffering of magmas as they ascend through a thick column of olivine gabbroic mush that has been deposited from a thin shallow 2 km deep subcaldera sill that is in a thermochemical steady state wolf s lavas have the most depleted isotopic compositions of any historically active intraplate ocean island volcano on the planet and have isotopic compositions except for he he indistinguishable from midocean ridge basalt erupted from the galapagos spreading center gsc 250 410 km away from the peak of influence of the galapagos plume wolf s lavas are enriched in incompatible trace elements and have systematic major element differences relative to gsc lavas however wolf s magmas result from lower extents of melting deeper melt extraction and a greater influence of garnet compared with gsc magmas but wolf and the gsc share the same sources these melt generation conditions are attributed to melting in a thermal and mechanical boundary layer of depleted asthenosphere at the margins of the galapagos plume the lower degrees of melting and extraction from deeper levels result from a thicker lithospheric cap at wolf than exists at the gsc

late pleistocene late glacial and holocene glacier advances on the tibetan plateau abstract many end moraine sequences in various mountain areas of the tibetan plateau have already been investigated in detail but a homogeneous chronostratigraphy is still lacking the ice marginal limits are commonly given local names and often the classification does not seem to be secure this is one reason for controversial discussions on the ice extent at the lgm because most organic material in tibet developed at the beginning of the holocene only a few older radiocarbon dates are available up to now late glacial terminal moraines have been found in the western kunlun shan and in the tian shan their radiocarbon ages ca 15 ka bp correspond to a glacier advance south of the qaidam basin which can be correlated with late glacial lacustrine sediments in eastern tibet different ages of peat development in different tongue like basins have been obtained even the bases of peat bogs in basins at nianbaoyeze mountains enclosed by apparent lgm end moraines gave holocene ages three main holocene intervals have been radiocarbon dated from palaeosols and basal peat layers in the area except for a younger glacier re advance at about 3000 bp and those of the little ice age the age of many last glaciation glacier advances on the tibetan plateau are constrained only on the basis of organic matter lying on top of the moraines and therefore might be of late glacial or pleistocene age

asynchronous glaciation at nanga parbat northwestern himalaya mountains pakistan we present a new glacial chronology demonstrating asynchroneity between advances of himalayan glaciers and northern hemisphere ice sheet volumes glaciers at nanga parbat expanded during the early to middle holocene ca 9 0 5 5 ka no major advances at nanga parbat during the last global glacial stage of marine oxygen isotope stage 2 mis 2 between 24 and 11 ka were identified preliminary evidence also indicates advances between ca 60 and 30 ka these periods of high ice volume coincide with warm wet regional climates dominated by a strong southwest asian summer monsoon the general lack of deposits dating from mis 2 suggests that nanga parbat was too arid to support expanded ice during this period of low monsoon intensity advances during warm wet periods are possible for the high altitude summer accumulation glaciers typical of the himalayas and explain asynchronous behavior however the holocene advances at nanga parbat appear to have been forced by an abrupt drop in temperature ca 8 4 8 0 ka and an increase in winter precipitation ca 7 5 5 ka these results highlight the overall sensitivity of himalayan glaciation to orbital forcing of monsoon intensity and on millennial or shorter time scales to changes in north atlantic circulation

holocene glacier fluctuations and migration of neolithic yak pastoralists into the high valleys of northwest bhutan abstract here we present geomorphologic palaeoenvironmental and archaeo botanical data which elucidate the late pleistocene and holocene glacial history of the high mountain locked himalayan valleys in northwest bhutan and provide one of the earliest proofs of human activity yet known for the high himalaya range in this area difficult to access close linkage between climatic change glacier fluctuations and human migration patterns has been discovered glacier systems in the studied area are characterized by avalanching and debris mantled glacier snouts with the significant local influence of the indian summer monsoon causing decoupling of glacier responses from temperature changes but supporting the idea of monsoonal forcing geomorphologic mapping together with optically stimulated luminescence osl and radiocarbon dating of ice proximal sediments has been used to construct a local glacial chronology local ice stream networks developed during the early holocene ca 10 000 9000 a ago and during the early part of the mid holocene 6710 90 4680 155 cal a bp at which times there were ice advances of about 5 km from the modern glacier termini at such times the intensity of pro and periglacial processes would have intensified and ice dammed lakes were probably common as well rendering human colonization of the high valleys in northwest bhutan impossible an abrupt shift to dry climatic conditions on the tibetan plateau between 5000 and 4500 a bp coincided with glacial decay and the onset of morphodynamically stable conditions on the broad valley floors of the high valleys in this part of the himalaya palynological data suggest that the sudden disappearance of juniper and rhododendron pollen the immediate onset of pollen input from cereals confirmed by detailed sem analysis and a clear pattern of over grazing trampling and peat deterioration can be linked to human arrival in the valleys at ca 4280 130 cal a bp extensive charcoal horizons dating to 4745 250 and 4680 155 cal a bp are interpreted as evidence for human use of fire and forest clearances and agree spatially and temporally with the pollen based picture charcoal occurrences as old as 6710 90 cal a bp might be linked to yet earlier exploration of these himalayan valleys during phases of low glacial activity we provide an account of the colonization of these high valleys in response to glacial and monsoonal change and argue that the most likely founder societies come from the tibetan plateau where yak and barley based pastoralism and neolithic settlements are known to have existed since the mid holocene

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

eruptive stratigraphy of the tatara san pedro complex 36 s southern volcanic zone chilean andes reconstruction method and implications for magma evolution at long lived arc volcanic centers

plume ridge interaction lithospheric stresses and the origin of near ridge volcanic lineaments 1 in many hot spot ridge systems formation of off axis volcanic chains or lineaments occurs between the hot spot centers and nearby mid ocean ridges in some cases such as galapagos kerguelen and possibly the mid pac mountains and tristan these lineaments appear to meet in a focus zone near the hot spot and fan outward in the direction of the ridge axis the origins of these lineaments are not well known and do not easily fit into typical conceptual models of ridge or hot spot volcanism it has been proposed for the galapagos region that such lineaments are caused by channeling of hot asthenosphere from off axis mantle plumes toward mid ocean ridges where enhanced volcanism initiates island formation morgan 1978 alternatively other workers suggest that these lineaments are controlled by patterns of stress in the lithosphere we examine this latter hypothesis by considering the effects of buoyant uplift and asthenospheric shear on the base of the lithosphere induced by an expanding mantle plume using thin plate theory we calculate the two dimensional plan view pattern of depth integrated stresses in a plate of varying thickness both a straight continuous ridge and a ridge transform ridge system are simulated by a displacement discontinuity boundary element model ridge and transform segments have imposed normal and zero shear tractions and we test different idealized tectonic or far field stress conditions assuming that volcanism is promoted by lithospheric tension and aligns along lineaments parallel to trajectories of least tensile stress calculations reproduce the rough fan shaped pattern of lineaments between the galapagos archipelago and the galapagos spreading center the focus of the fan shape is over the plume center when it interacts with a straight ridge but the fan focus appears closer to a segmented ridge offset by a transform fault if the ridge segments are more tensile than the far field stress this condition provides a plausible explanation for the apparent focus at the galapagos north of the hot spot center the width of the fan pattern along the ridge axis is predicted to increase as the plume ridge separation increases and as the far field stress becomes more tensile parallel to the ridge the observed width along the galapagos spreading center is consistent with a nearly isotropic remote stress models predict the lithospheric tension caused by plumes to promote lineament formation on only young lithosphere in support of this prediction a compilation of data from 23 hot spots shows that lineament formation is common near hot spots with plume ridge separations of 1250 km or on lithosphere of 25 ma but not on older lithosphere

quaternary glaciation of tibet the geological evidence the question of the number and extent of pleistocene glaciations on the qinghai xizang tibet plateau remains contentious there has been considerable research activity in tibet by chinese scientists since the late 1950s and their principal findings including data on glacial and periglacial geomorphology sedimentology tectonics stratigraphy and lake history have been used to reconstruct ice margins and palaeosnowlines three and in places four distinct glaciations have been recognised the most extensive occurring in the later middle pleistocene valley and piedmont glacial systems with some mountain ice caps and a small ice sheet on the upper reaches of the huang he have been recognised but there is no evidence of a single tibetan ice sheet as the plateau and the himalaya karakoram underwent accelerating uplift through the quaternary there occurred progressive desiccation in the interior as the influx of indian ocean moisture was constrained equilibrium line elevations in the last glacial maximum were 4000 m in the south east and northeast plateau margins rising to 5500 m in the northwest interior the heat island provided by the plateau the progressive reduction in precipitation most marked during the glacials and the strong southeast to northwest precipitation gradients produced a glacier distribution pattern dominated by the trans tibetan mountain ranges tectonics and periglacial including aeolian processes have played an equal role with glaciation in generating the plateau s quaternary sedimentary succession

asynchronous glaciation at nanga parbat northwestern himalaya mountains pakistan comment we welcome phillips et al s 2000 1 study which substantiates previous evidence for glaciation during global interstadials in the himalaya sharma and owen 1996 2 richards et al 2000 3 we were surprised however to read their criticism of the optically stimulated luminescence osl

quaternary glaciation of gurla mandhata naimon anyi abstract the quaternary glaciation of gurla mandhata naimona nyi an impressive isolated dome shaped massif situated in a remote region of southern tibet was examined using glacial geomorphic methods and dated using 10 be terrestrial cosmogenic nuclides the oldest moraines representing an expanded ice cap that stretched 5 km into the foreland of the gurla mandhata massif likely formed during marine isotope stage mis 10 or an earlier glacial cycle another glacial expansion of coalescing piedmont type occurred during the early part of the last glacial cycle or the penultimate glacial cycle after which glaciers became restricted to entrenched valley types impressive latero frontal moraines at the mouths of most valleys date to the early part of the last glacial cycle and mis 3 a succession of six sets of moraines within the valleys and up to the contemporary glaciers show that glaciers advanced during the lateglacial early holocene neoglacial and possibly little ice age the change of style of glaciation throughout the latter part of the quaternary from expanded ice caps to deeply entrenched valley glaciers might reflect 1 climatic controls with reduced moisture supply to the region over time and or 2 tectonic controls reflecting increase basin subsidence due to detachment faulting and enhanced valley incision

the little ice age in the himalaya a review of glacier advance driven by northern hemisphere temperature change northern hemisphere cooling between 1400 and 1900 in the common era ce resulted in the expansion of glaciers during a period known as the little ice age lia early investigation of recent advances of himalayan glaciers assumed that these events were synchronous with lia advances identified in europe based on the appearance and position of moraines and without numerical age control however applications of quaternary dating techniques such as terrestrial cosmogenic nuclide dating have allowed researchers to determine numerical ages for these young moraines and clarify when glacial maxima occurred this paper reviews geochronological evidence for the last advance of glaciers in the himalaya the 66 ages younger than 2000 years 0 2000 ce calculated from 138 samples collected from glacial landforms demonstrate that peak moraine building occurred between 1300 and 1600 ce slightly earlier than the coldest period of northern hemisphere air temperatures the timing of lia advances varied spatially lik

quaternary paleoenvironmental change on the tibetan plateau and adjacent areas western china and western mongolia abstract this paper summarises the nature of climatic change during the last glacial interglacial cycle on the tibetan plateau and adjacent areas the results are derived from inland glacier fluctuations lake level changes and dust loess records of central asia including tibet these are based on our field investigations from 1988 to 1998 and literature surveys the changing extents of different climatic controlled geomorphic landscapes and vegetation zones help to provide estimates of the magnitude of climatic change features such as ice wedge casts loess and palaeosols ela reconstruction s and palaeobotanical data are used to help reconstruct palaeoprecipitation and palaeotemperatures weathering characteristics the overlying strata and some luminescence dates indicate that there are two main glacial ice advances during the last glacial cycle these correspond to marine oxygen isotope stages ois 2 and 4 in some areas as the eastern or northern margin of the tibetan plateau remnants of older glaciations are preserved higher lake levels in the deserts of central asia and on the tibetan plateau are dated to 40 to 25 ka ois 3 and to late glacial early to mid holocene periods our work supports the view that in many areas of central asia cold phases during the last glacial correspond with the maximum extent of glaciers and the periglacial activity the last glaciation produced large alluvial fans alternating with periods of high lake stands on the tibetan plateau however at the northern margin of the plateau in the qaidam basin and in some particular desert areas in western china high lake levels occurred also during the pleistocene and are related with alluvial fans

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

the limited influence of glaciations in tibet on global climate over the past 170 000 yr extensive ice cover on the tibetan plateau would significantly influence earth s climate in general and the asian monsoon system in particular but extent and timing of quaternary glaciations in tibet remain highly controversial we dated erratics on top of moraines in the climatic key areas of central and east tibet using cosmogenic 10be 26al and 21ne consistent exposure ages obtained by various nuclides indicate a continuous period of exposure since the deposition of the samples our data imply that glacial advances were restricted to a few 10 km during the last 170 kyr in central tibet and during the peak of the last glaciation 24 13 kyr ago in eastern tibet advances of tibetan glaciers were much less prominent than elsewhere in the northern hemisphere most likely due to very arid conditions and high sublimation rates a proposed ice dome covering the entire plateau can be excluded thus albedo increase of tibet most likely did trigger neither northern hemisphere ice ages nor paleomonsoon changes during the last two glacial cycles the glacial advance during marine isotope stage 2 in east tibet and the absence of significant glacial events during the holocene suggest a relation of snowline lowering in east tibet to north atlantic cooling events rather than to periods of high precipitation by an intensified monsoon

anticlockwise p t path of granulites from the monte castelo gabbro ordenes complex nw spain the study of mafic and aluminous granulites from the monte castelo gabbro ordenes complex nw spain reveals an anticlockwise p t path that we interpret as related to the tectonothermal activity in a magmatic arc probably an island arc the p t path was obtained after a detailed study of the textural relationships and mineral assemblage succession in the aluminous granulites and comparing these with an appropriate petrogenetic grid additional thermobarometry was also performed the granulites are highly heterogeneous with distinct compositional domains that may alternate even at thin section scale garnets are generally idiomorphic to subidiomorphic and in certain domains of the aluminous granulites they show overgrowths forming xenomorphic coronas around a more or less idiomorphic core both types of garnets show significant ca enrichment at the crystal rims which together with the other mineralogical and textural characteristics is compatible with a pressure increase with low t variation p t estimations indicate a peak of t 800 c and p 9 5 kbar attained after a significant increase in pressure that took place at high temperatures in the sillimanite field we suggest that this kind of trajectory probably anticlockwise is compatible only with a terrane heated by an intense magmatic activity after or during tectonic crustal thickening magmatic injection at the base and or into the crust which is characteristic of magmatic arcs