stable isotope based paleoaltimetry abstractthe quantitative estimation of paleoaltitude has become an increasing focus of earth scientists because surface elevation provides constraints on the geodynamic mechanisms operating in mountain belts as well as the influence of mountain belt growth on regional and global climate the general observation of decreasing 18o and 2h values in rainfall as elevation increases has been used in both empirical and theoretical approaches to estimate paleoelevation these studies rely on the preservation of ancient surface water compositions in authigenic minerals to reconstruct the elevation at the time the minerals were forming in this review we provide a theory behind the application of stable isotope based approaches to paleoaltimetry we apply this theory to test cases using modern precipitation and surface water isotopic compositions to demonstrate that it generally accords well with observations examples of the application of paleoaltimetry techniques to himalaya tibet and the andes are discussed

hydrogen isotopes in eocene river gravels and paleoelevation of the sierra nevada we determine paleoelevation of the sierra nevada california by tracking the effect of topography on precipitation as recorded in hydrogen isotopes of kaolinite exposed in gold bearing river deposits from the eocene yuba river the data compared with the modern isotopic composition of precipitation show that about 40 to 50 million years ago the sierra nevada stood tall 2200 meters a result in conflict with proposed young surface uplift by tectonic and climatic forcing but consistent with the sierra nevada representing the edge of a pre eocene continental plateau

a high resolution stable isotopic record from the junggar basin nw china implications for the paleotopographic evolution of the tianshan mountains this study presents high resolution oxygen and carbon isotopic records of paleosol carbonates from fluvial sediments and lacustrine carbonates sampled from the jingou he and kuitun he stratigraphic sections located in the northern tianshan piedmont these sections expose remarkable outcrops of junggar foreland basin sediments that have been previously dated by high resolution magnetostratigraphy to between 23 6 and 1 ma and 10 5 and 3 1 ma a total of 216 samples of fluvio lacustrine sediments were collected from which isotopic analyses yield 18o smow values that range from 13 7 to 29 9 in the jingou he section and 16 3 to 21 0 in the kuitun he section 13c pdb values range from 12 9 to 3 0 in the jingou he section and from 7 8 to 4 0 in the kuitun he section 18o values decrease between 25 and 23 ma and then remain relatively steady with the exception of one period that contains samples with higher oxygen isotope values at 16 ma during the periods when there are samples that overlap in time from the kuitun he and jingou he sections we observe a difference of 1 7 between values from the two locales the 13c values also decrease between 25 and 23 ma and then remain relatively steady until 10 ma with again one short period of higher values at 16 ma then between 10 and 3 1 ma carbon isotope values progressively increase we interpret that 18o and 13c isotopic values during lacustrine periods 25 23 ma and 16 ma as largely controlled by evaporation and opening closing of the lake to external inputs we interpret the 18o values of paleosol carbonate in the junggar basin to be influenced by the hypsometry of the high tianshan range while the 13c values may record the uplift history of the depositional area in the foreland basin itself as well as the isotopic composition of plants consequently we conclude that the jingou he and kuitun he drainage basins in the central tianshan have remained at relatively unchanged elevations for the past 20 ma we also suggest that the elevation of the southern part of the foreland basin increased between 10 and 3 1 ma probably as a result of tectonic deformation in the piedmont and sedimentary filling of the sedimentary basin the carbon isotope record remains relatively stable through time and isotopic values suggest that there was little or no expansion of c4 plants in this region in the late miocene

empirical relationships between elevation and the stable isotope composition of precipitation and surface waters considerations for studies of paleoelevation change a compilation of 68 studies from throughout many of the world s mountain belts reveals an empirically consistent and linear relationship between change in elevation and change in the isotopic composition of precipitation along altitudinal transects the isotopic composition of precipitation decreases linearly with increasing elevation in most regions of the world except in the himalayas and at elevations 5000 m there are no significant differences in isotopic lapse rates from most regions of the world 0 28 permil 100 m except at the extreme latitudes where isotopic lapse rates are higher given information on past changes in the isotopic composition of precipitation preserved in pedogenic or authigenic minerals this global isotopic lapse rate can be used to place numerical constraints on the topo graphic development of some ancient mountain belts or plateaus there are many complicating factors that can confound interpretation of paleoel evation change based on stable isotopes and many of these are unique to specific mountain belts or time periods relevant to all stable isotope based paleoelevation change studies is the temperature dependent isotope fractionation between a pedo genic or authigenic mineral and the water from which it forms in cases where isotopic proxy minerals are sampled from localities where temperature will change simulta neously with elevation change the apparent change in the isotopic composition of precipitation may be dampened by several permil this suggests that samples taken from the rainshadow side of an emerging orographic barrier may be more likely to preserve isotopic changes resulting from mountain uplift than samples taken from atop a rising mountain range or plateau

high times on the tibetan plateau paleoelevation of the thakkhola graben nepal east west extension in the tibetan plateau is generally assumed to have resulted from gravitational collapse following thickening and uplift on the basis of this assumption several studies have dated east west extensional structures to determine when the plateau attained its current high elevation however independent estimates of elevation are needed to determine whether extension occurred before during or after the plateau achieved its current elevation because the isotopic composition of meteoric water decreases with increasing elevation significant change in local elevation throughout the thakkhola graben depositional history should be recorded by change in 18 o values of fluvial and lacustrine carbonates the 18 o values of 16 to 23 of thakkhola graben carbonates reflect meteoric water values similar to modern values and suggest that the southern tibetan plateau attained its current elevation prior to eastwest extension initiation of thakkhola graben extension is constrained between 10 and 11 ma based on magnetostratigraphy of the older tetang formation the 13 c values of soil carbonates suggest an age younger than 8 ma for the base of the thakkhola formation

stable isotope evidence for multiple pulses of rapid surface uplift in the central andes bolivia paleoelevation histories from mountain belts like the central andes of bolivia provide important constraints on the timing and geodynamic mechanisms associated with surface uplift we present new oxygen and carbon isotope data 18 o 13 c and 47 from oligocene miocene strata exposed in the eastern cordillera of the bolivian central andes in order to reconstruct both the deformation and paleoelevation history of the region prior to late miocene time paleosol carbonate in strata 24 ma have 18 o c values between 5 7 and 9 7 and 47 values indicating paleotemperatures of 32 42 c paleosol carbonate in strata ca 17 ma have 18 o c values between 11 6 and 13 8 and 47 values indicating paleotemperatures of 15 23 c these data interpreted within the context of recent paleoclimate topography models suggest oligocene early miocene 29 24 ma paleoelevations were between 0 and 1 5 km a s l while middle miocene ca 20 15 ma paleoelevations were 2 5 km a s l oligocene and miocene strata are relatively undeformed and overlap folded and faulted paleozoic rocks in this portion of the bolivian eastern cordillera indicating much of the change in elevation occurred after upper crustal deformation collectively data from the area record an initial period of upper crustal deformation and exhumation a subsequent period of sediment deposition and overlap and then an episode of surface uplift accompanied by negligible upper crustal deformation the disconnect between the timing of upper crustal deformation and the timing of surface uplift requires geodynamic processes other than upper crustal thickening to explain the oligocene miocene basin and elevation history in the eastern cordillera we propose accommodation for oligocene miocene strata was created in response to the formation and removal of negatively buoyant material in the lowermost crust and mantle lithosphere and the subsequent increase in surface elevation between ca 24 and 15 ma resulted from its removal other locations in the central andes record similar geological histories over different time periods suggesting spatial and temporal variation in the removal of lithospheric mantle documenting basin extent age and elevation history provides important constraints on the size and timescale of the geodynamic processes that control surface uplift

nonuniform surface uplift of the andean plateau revealed by deuterium isotopes in miocene volcanic glass from southern peru abstract proposals for rapid late miocene surface uplift driven by large scale lithospheric removal beneath the central andean plateau have been based largely on temperature sensitive paleoaltimeters both the magnitude and mechanism of this proposed pulse of uplift have been challenged first climatic general circulation models support protracted uplift with predicted temperature and isotopic shifts enhanced by attainment of threshold elevations second tectonic models in which surface elevations are compensated by regional contraction and crustal thickening question the need for lithospheric removal and predict broadly coeval uplift of the entire plateau we present hydrogen isotope data using a novel temperature insensitive volcanic glass proxy from continuous well dated lower to middle miocene basin fill in the western cordillera of the northern plateau that show a rapid decrease in d values 62 8 at 19 16 ma with extremely negative values continuing into the pliocene we propose that the basin reached its current elevation by 16 ma 6 myr earlier than proposed for the central plateau the rapid decrease in d values is consistent with punctuated surface uplift of 2 2 3 7 km between 19 and 16 ma whereas the 3 7 km upper estimate assumes a static climate similar to modern the 2 2 km lower estimate conservatively incorporates modeled changes in the isotopic composition of precipitation associated with elevation change comparison of these results to existing paleoelevation estimates from the andean plateau facilitates a tentative reconstruction of earliest middle miocene paleotopography showing a central depression with flanking hinterland and thrust belt highlands this apparent pattern of nonuniform plateau uplift contradicts shortening proportional topographic growth over tens of myr we propose that temporally and spatially irregular surface uplift may be linked to pronounced local variability in crustal shortening and or piecemeal removal of dense mantle lithosphere insofar as these irregularities reflect the scale of heterogeneity for surface uplift processes available paleoelevation estimates point to a principal uplift mechanism that varies over relatively short

the isotopic composition of meteoric water along altitudinal transects in the tian shan of central asia abstract the tian shan in central asia are a unique mountain range in that they are in the world s most continental location seasonal precipitation in the northern tian shan is segregated into distinct elevation bands where high elevations receive precipitation primarily during summer and low elevations to the north receive precipitation primarily during the late winter and spring in this study we sampled stream water along multiple altitudinal transects to determine the effect unique seasonal patterns of precipitation have on the isotopic composition of surface water our results suggest that the northern tian shan exhibits an isotopic lapse rate for waters sampled in late spring but not for those sampled in late summer when stream water budgets are dominated by high elevation precipitation and snow melt deuterium excess results suggest that subcloud evaporation significantly affects the isotopic composition of precipitation at low elevations in spring and that sublimation of snow has a minor impact on 18o values of summer melt water because high and low elevation 18o values are similar conventional paleoaltimetry based on rayleigh distillation of an air mass is not applicable to the kyrgyz tian shan stream water proxies from the rock record are likely to reflect changes in the seasonal distribution of precipitation which occur on the same spatial scale as altitudinal changes these results highlight the need to understand modern controls on local stable isotopes of meteoric water in reconstructions of past climate or topography using geologic proxy materials

groundwater δ18o and δd from central indian peninsula influence of the arabian sea and the bay of bengal branches of the summer monsoon abstract results of oxygen and hydrogen isotopic investigations of shallow groundwater and river water samples from the central indian peninsula are reported the study was undertaken to isotopically characterise the near surface water sources and identify the influence of the two branches of the indian summer monsoon june september in this region the western part of the study area receives vapour flux largely from the arabian sea branch whereas the eastern part receives significant vapour flux from the bay of bengal branch no significant rainfall occurs in the study area during northeast winter monsoon period of october december or the remaining part of the year therefore the isotopic character of shallow groundwater from this region could be used to study the relative influence of the vapour sources from the arabian sea and the bay of bengal the study shows that i the northeast part receiving significant rainfall from the bay of bengal branch has a distinctly depleted isotopic composition 18 o 5 2 compared to areas receiving dominant rain from the arabian sea branch 18 o 1 1 ii in the west coastal belt the average 18 o in groundwater is close to the average 18 o of precipitation at bombay 1 4 1 1 but groundwater samples in the entire deccan plateau region show signatures of evaporative enrichment in the form of a low slope 6 5 of 18 o d regression line b low d excess 0 5 and c slightly enriched 18 o values 1 1 compared to those expected from the limited precipitation data from stations in maner basin approximately in the middle of the study area iii depleted ground waters along the central indian east coast could arise due to continental rainout of the arabian sea vapour source as the moisture laden monsoon winds crossover to the bay of bengal alternatively it is necessary to postulate that the surface waters of the bay of bengal contributing to inland vapour flux are significantly more depleted during the monsoon period than the known depletion of 1 it is also possible that both factors are operative

seasonal bias in the formation and stable isotopic composition of pedogenic carbonate in modern soils from central new mexico usa in order to better calibrate pedogenic carbonate as a proxy for past environments we compared the stable isotopic composition of soil co 2 soil water and pedogenic carbonate in young soils from central new mexico usa seasonal changes in the 13 c value of soil co 2 the 18 o value of soil water and the soil temperature were monitored to establish the timing of isotopic equilibrium with the carbonate calcite solubility was calculated from measured temperatures and co 2 concentrations in the soil this approach allowed us to determine the conditions associated with pedogenic carbonate formation carbon isotope equilibrium oxygen isotope equilibrium and minimum calcite solubility all occurred simultaneously during warm dry conditions in may 2008 when soil co 2 concentrations were low it is therefore concluded that pedogenic carbonate forms during warm dry periods and does not record mean growing season conditions as typically assumed the seasonal bias in pedogenic carbonate formation may explain the occurrence of pedogenic carbonate in monsoon climates and its absence in regions where annual precipitation is more uniformly distributed the implications of the seasonal bias for stable isotope based paleoenvironmental reconstructions are that paleoelevations may have been previously over or underestimated paleoatmospheric co 2 concentrations likely have been signifi cantly overestimated and pedogenic carbonate provides a c 4 biased record of paleovegetation especially in dry soils

isotopic measurements of precipitation on central asian glaciers southeastern tibet northern himalayas central tien shan the glacial regions of central asia considered in our study are influenced by tropical monsoons and western extratropical cyclones isotopic 18o and d data were obtained over 3 years in three climatic regions gongga massif of southeastern tibet windward slope of summer monsoon xixibangma massif on the northern slope of the himalayas leeward of summer monsoon and the massifs of pobeda khan tengry in the central tien shan exposed to western airstreams the survey reported here provides information from atmospheric precipitation snow pits and a 23 m ice core the significant differences of oxygen isotopic ratios from 25 1 per mil to 9 5 per mil indicate that the indian and pacific oceans as well as the atlantic ocean are sources of moisture on the northern slope of the himalayas and southeastern tibet sharply changing isotopic ratios in precipitation corresponded to changing wind direction and were associated with different sources of air masses on the northern slope of the himalayas and southeastern tibet steady isotopic ratios in atmospheric precipitation and the absence of changing 18o composition in a 23 m ice core suggest only one source of moisture in central tien shan the relatively heavier oxygen isotopic ratios in atmospheric precipitation and ice core indicate the moisture from which the precipitation was derived originated over the caspian or mediterranean seas within the eurasian continent air masses developed over the atlantic ocean advance farther than those from the pacific and indian oceans

climatic and hydrologic changes in the tien shan central asia abstract the authors analyze climatic and hydrologic data from 110 sites collected from the middle of the twentieth century to the present in the tien shan one of the largest mountain systems of central asia in spite of a few confounding interregional variations in the temporal changes of surface air temperature precipitation runoff glacier mass and snow thickness in the tien shan it has been possible to establish statistically significant long term trends in these key hydroclimatic variables the average rise in air temperature was 0 01 c yr 1 over the range with slightly lower values below 2000 m elevation the precipitation in the tien shan increased 1 2 mm yr 1 over the past half century the precipitation increase is larger at low altitudes in the northern and western regions than at altitudes above 2000 m a decrease in snow resources occurred almost everywhere in the tien shan the maximum snow thickness and snow duration have decreased on average 10 cm and 9 days respectively the annual

the hydrogen and oxygen isotope geochemistry of pedogenic clay minerals principles and theoretical background abstract the 18 o 16 o and d h ratios of the structural oxygen and hydrogen of naturally occurring clay minerals carry information about the conditions under which the minerals formed clays generally form in isotopic equilibrium with the environment and hence have isotopic compositions that reflect the temperature of formation and the 18 o 16 o and d h ratios of water in the micro environment the isotopic signature of water in the weathering environment is a reflection of the climate once formed clays are resistant to isotopic alteration under surface and near surface conditions except when they undergo subsequent mineralogical alteration in some instances this alteration may be subtle as in the case of conversion of kaolinite with a high degree of crystalline order as measured by the hinckley index to kaolinite of low crystalline order in a pedogenic profile isotopic studies of pedogenic clays may be expected to yield more information about pedogenesis and paleoclimate when both 18 o 16 o and d h ratios of the clays are measured however few studies have incorporated the use of the two isotope ratios

stable isotopic variations in west china a consideration of moisture sources 1 in this study individual precipitation samples collected over 2 years at stations in different climatic regions of west china tibetan plateau region tianshan region and altay were analyzed for the stable isotopes of precipitation to improve our understanding of how vapor transport impacts the modern stable isotopic distribution our results identify regional patterns in both 18o and deuterium excess d excess defined as d 8 18o and in particular we have identified the northward maximum extent of the southwest monsoon over the tibetan plateau this demarcation is also the boundary for the fractionation effect of temperature on stable isotopes in precipitation the patterns we have identified are as follows 1 in the southern tibetan plateau along the southern slope of the himalayas our results show a distinct seasonality for both 18o and d excess as a result of the shift of summer monsoon moisture and winter westerly moisture transport the signals of 18o in the western tibetan plateau reveal that the region receives southwest monsoonal moisture in the east of the plateau stable isotopic variation shows alternation between monsoon intrusion and recycling of northern moisture 2 in contrast in tianshan there is an apparent temperature effect in 18o with enriched values occurring in summer and depleted values occurring in winter seasonal d excess values opposite to those observed in the southern tibetan plateau are controlled by differing seasonal evaporation conditions 3 in altay the most northern mountain region the seasonal 18o shows the same variation with that in tianshan region however d excess shows no apparent seasonal variation

subglacial environments an introduction abstract this volume contains papers discussing various aspects of the subglacial environment most of which were presented at the vth international drumlin symposium at the xivth inqua congress in berlin germany 1995 the common goal of the research presented is to shed more light on the dynamics of the interface between glacier ice and its substratum this is approached by studying the relationships between subglacial sediments landforms and their formation processes special attention is devoted to drumlins spectacular and intriguing glacial bedforms whose origin must be comprehended if mechanisms governing ice motion over soft sediments and ultimately processes controlling the course of glaciation are to be better understood

a model for the present stress field along the xian shui he fault belt northwest sichuan china abstract along the left lateral strike slip fault on the eastern border of the tibetan plateau 22 m 6 earthquakes have occurred since 1725 the fault is divided into three segments with two aseismic gaps between the segments using the elasticity theory of dislocations the spatial and temporal variations in stress are calculated using source parameters from the earthquakes such as epicenter time length of surface rupture mean coseismic displacement and magnitude further a total slip rate is assumed in order to calculate the stress increase due to plate motion the model is optimized towards the smallest variations in the preseismic stresses under this constraint the present stress field is calculated by varying the spatial distribution of the ratio of seismic slip to total slip and the unknown initial stress field the greatest seismic hazard is found in the central segment if a spatially constant slip rate is assumed however different seismic slip rates for different fault segments lead to the southern segment as the region where the next large earthquake may occur

seasonality and interannual variability of the westerly jet in the tibetan plateau region abstract in this study 40 yr ecmwf re analysis era 40 data are used for the description of the seasonal cycle and the interannual variability of the westerly jet in the tibetan plateau region to complement results based on the analysis of monthly mean horizontal wind speeds an occurrence based jet climatology is constructed by identifying the locations of the jet axes at 6 hourly intervals throughout 1958 2001 thus a dataset describing the highly transient and localized features of jet variability is obtained during winter and summer the westerly jet is located respectively to the south and north of the tibetan plateau during the spring and autumn seasons there are jet transitions from south to north and vice versa the median dates for these transitions are 28 april and 12 october the spring transition is associated with large interannual variations while the fall transition occurs more reliably within a 3 week period the strength of the jet exhibits a peculiar seasonal cycle during northw

water balance of the indus river basin and moisture source in the karakoram and western himalayas implications from hydrogen and oxygen isotopes in river water 1 stable isotope measurements of hydrogen and oxygen for surface waters from the indus river basin irb together with historical records for river discharge annual precipitation and groundwater levels are used to assess water balance for the basin the indus river presently drains 53 km3 yr 1 or roughly one eighth of the 398 km3 water that annually falls on the basin in the form of rain and snow with the remainder returned to the atmosphere by evapotranspiration monthly samples for the indus river close to its mouth for the water year march 1994 to february 1995 show a tight correlation in d and 18o space the slope of the linear regression is 7 5 which is not significantly different from the slopes of the local meteoric water lines lmwl 7 3 and 7 1 this observation argues against significant loss of water by direct evaporation from river surfaces or from soils in hydrologic continuum with surface waters an upper limit for evaporation from poorly drained soils is calculated to be 10 km3 yr 1 or only 2 5 of the annual precipitation flux groundwater storage in the entire canal command area received a maximum of 23 km3 yr 1 or 5 8 of the annual precipitation during the early stages of irrigation but modern recharge is probably balanced by discharge to rivers and well exploitation transpiration by natural vegetation and crops annually returns 83 of the precipitation flux and constitutes the largest pathway for the loss of water from the basin deuterium excess d excess in the irb ranges between 4 and 28 with values for 95 of the sample population exceeding 10 the indus main channel close to its mouth varies in d excess between 12 and 20 during low and high water stands respectively with a discharge weighted average of 18 these values are distinctly higher than the long term average for the indian monsoon 8 and reflect contributions from water vapor originating in the mediterranean 22 or other inland seas using these end member compositions and the discharge weighted average d excess isotope balance calculations require that up to 72 of the indus discharge close to its mouth must be derived from the mediterranean end member and implies that bulk of the indus discharge is the result of delayed runoff from the karakoram and the himalayas

stable isotopic constraints on the tectonic topographic and climatic evolution of the northern margin of the tibetan plateau abstract this study presents oxygen and carbon isotopic records from lacustrine paleosol alluvial and fluvial carbonate sampled in thirteen cenozoic sedimentary sections that span the northern margin of the tibetan plateau isotopic analyses of 1475 carbonate samples yield 18 o values that range from 13 1 to 38 9 smow and 13 c values range from 11 5 to 3 7 pdb based on these analyses we see two isotopic trends regionally we interpret a paleogene decrease in average oxygen isotope values to result from an increase in the mean elevation of the study region s drainages as they tapped waters from a growing tibetan plateau to the south of the study area we interpret a neogene increase in both carbon and oxygen isotope values to result from the initiation of local mountain building in the study area and the withdrawal of marine waters which increased basin isolation aridity and temperatures the timing of inferred initiation of uplift in this region is consistent with structural thermochronological and sedimentological evidence for a tectonic transition in the early and middle miocene from accommodation of india eurasia convergence through extrusion along the altyn tagh fault to accommodation of convergence through active shortening and mountain building in this region this study also supports tectonic models for the differential uplift of the tibetan plateau in that mountain building in this study region significantly postdates estimates for the attainment of high elevation from isotopic studies of the central tibetan plateau

changes in groundwater induced by water diversion in the lower tarim river xinjiang uygur nw china evidence from environmental isotopes and water chemistry summary the lower tarim river in nw china is under severe ecosystem degradation due to stopped stream flow and diminished groundwater recharge since year 2000 eight water diversions from the upper stream and from the neighboring kaidu kongque river have been implemented to alleviate the ecosystem disaster in order to assess the effectiveness of the water diversion project and to identify proper tracers of groundwater dynamics we sampled the riparian groundwater system in 2007 and 2008 along the 350 km long river channel through the 40 monitoring wells situated along nine transects perpendicular to the river and three soil profiles measurements on the samples have included environmental isotopes 18 o 2 h 3 h and water chemistry the results show that remarkable changes have been induced by the water diversions the observed response of riparian groundwater system includes general decrease in total dissolved solid tds and rise of water table scope with greater than 1 m rise in water table is within 700 m from the riverbank in the upper segments and 300 m in the lower ones greater rise of water table occurs near the river bank tritium data show that the extent of modern recharge since 1960s including that from the diverted water is limited to 600 m from the riverbank at the upper segments and 200 m at the lower ones stable isotopes show that groundwaters regardless of modern or pre modern are enriched in heavy isotopes and are plotted in parallel to the meteoric water line in the d d plot attributed to evaporation during recharge groundwater is generally of na mg cl so4 type and is formed by dissolution of minerals such as halite sulfate and carbonates based on component correlation matrices analysis the salinity of groundwater is mainly affected by that of the diverted water and of the local antecedent groundwater salts in the unsaturated zone evapotranspiration during recharge as the zone of smaller groundwater depth less than 5 m suitable for the most existing populus euphratica and tamarix ramosissima the main species targeted by the rescue effort restricts to 200 m from the riverbank and narrows down towards downstream long term stability of the ecosystem cannot be achieved by the current water diversion scheme and regulating saving water in source streams and the upper middle tarim river is crucial for continuing water diversion

reconstructing the paleotopography of mountain belts from the isotopic composition of authigenic minerals the paleorelief of mountain belts can be estimated from the 18 o value of authigenic minerals development of relief during mountain building often creates lee side rain shadows in which precipitation is depleted in 18 o and d the magnitude of this rain shadow effect is strongly correlated to relief a compilation of 18 o data from surface waters throughout the globe shows a linear relationship between net elevation change and 18 o r 2 0 79 through the use of this relationship we investigated the timing and magnitude of elevation change in the southern alps of new zealand and the sierra nevada of california the 18 o values of kaolinites from new zealand show an 6 decrease in the early pliocene that corresponds to an 2 km elevation change in the southern alps the 18 o of smectites from the sierra nevada show little change since 16 ma suggesting that these mountains have been a long standing topographic feature

δ18o and δd of streamwaters across the himalaya and tibetan plateau implications for moisture sources and paleoelevation reconstructions abstract this study presents new 18o and d data from 191 streams across the himalaya and tibetan plateau to better constrain the spatial variability of stable isotopes in modern precipitation over this region moisture penetrating into the southeastern tibetan plateau is predominantly derived from monsoonal airmasses originating from the bay of bengal and transported into the eastern himalayan syntaxis along the brahmaputra river progressive rainout during orographic lifting and cooling results in clear relationships between 18o and d and catchment hypsometric elevation on the plateau margin however monsoonal derived moisture is progressively mixed with central asian airmasses in more western and northern parts of the tibetan plateau as a result predicted isotope elevation relationships that are based on empirical lapse rates or thermodynamic models of the isotopic evolution of an airmass produce large 1 3 km misfits between measured and predicted catchment elevations for much of the tibetan plateau including some areas directly north of the central himalayan crest this suggests that changes in the 18o or d of paleoprecipitation on the central and southwestern tibetan plateau may reflect surface uplift along moisture transport pathways or changes in the penetration of monsoonally derived moisture rather than regional surface uplift histories

stable isotope records of cenozoic climate and topography tibetan plateau and tarim basin we seek to better understand growth of the tibetan plateau and associated climate change by presenting the first regionally extensive set of oxygen isotope data obtained from ca 40 m y of cenozoic strata from a 700 000 km2 area ranging from the northern edge of the tibetan plateau northward across the entire tarim basin our results reveal a previously unrecognized large positive isotope shift from eocene to oligocene which we suggest results from initial topographic growth of the himalayan tibetan system and attendant reorganization of climate by this growing mountain belt a negative isotopic shift recorded in miocene strata may reflect retreat of the neotethyan sea from the tarim basin as well as enhanced elevation of the himalaya tibetan plateau region and the rise of the tian shan which diverted moisture bearing westerlies and deepened aridity in the tarim basin and the northern tibetan plateau

tibetan plateau summer monsoon northward extent revealed by measurements of water stable isotopes a program of individual precipitation events and river water sampling and of water isotopic measurements d 18o was carried out during summer 1996 along a northeast southwest transect of the tibetan plateau the spatial distribution of both 18o and deuterium excess d d 8 18o of the precipitation reveals three distinct regions simulations with a simple isotopic model and seasonal isotopic variations measured at two extreme south and north locations support our interpretation in terms of different summer moisture origins 1 south of the himalayan mountains the moisture provided by the indian monsoon has been recycled over the indian peninsula 2 between the himalayas and the tanggula mountains the oceanic moisture is directly transported from the bay of bengal along the brahmaptra river valley 3 north of the tanggula mountains the moisture is not provided by the monsoon anymore but by continental water recycling

spatial temporal changes in andean plateau climate and elevation from stable isotopes of mammal teeth abstract paleoelevation constraints from fossil leaf physiognomy and stable isotopes of sedimentary carbonate suggest that significant surface uplift of the northern andean plateau on the order of 2 5 1 km occurred between 10 3 and 6 4 ma independent spatial and temporal constraints on paleoelevation and paleoclimate of both the northern and southern plateau are important for understanding the distribution of rapid surface uplift and its relation to climate evolution across the plateau this study focuses on teeth from modern and extinct mammal taxa including notoungulates pyrotheres and litopterns spanning 29 ma to present collected from the altiplano and eastern cordillera of bolivia 16 2 s to 21 4 s and lowland brazil tooth enamel of large water dependent mammals preserves a record of surface water isotopes and the type of plants that animals ingested while their teeth were mineralizing previous studies have shown that the 18o of modern precipitation and surface waters decrease systematically with increasing elevations across the central andes our results from high elevation sites between 3600 and 4100 m show substantially more positive 18o values for late oligocene tooth samples compared to