the interaction of the madden julian oscillation with the maritime continent in a gcm previous studies using the hadley centre coupled model hadcm3 have shown that the islands of the maritime continent act as an unrealistic block to the eastward propagation of the madden julian oscillation mjo this blocking effect is investigated using a simplified aqua planet version of this gcm with various idealized configurations of the maritime continent islands placed on the equator and an mjo like convective signal forced by a propagating sea surface temperature anomaly dipole results suggest that it is the orography of the islands rather than the presence of the islands themselves which results in the blocking of the mjo although the peak elevation of the orography in the gcm is very much lower than in reality it appears to act as effective block to the eastward propagation of the low level kelvin wave signal which accompanies the mjo in particular the representation of sumatra in the gcm as a north south oriented ridge straddling the equator seems to be particularly effective at blocking the kelvin wave signal which in a full gcm would result in the weakening or complete extinction of the mjo signal to the east of the maritime continent

neogene and quaternary history of vegetation climate and plant diversity in amazonia the neotropical amazonian and andean plant diversity developed mainly during the tertiary in amazonia miocene oral diversity seems considerably higher than today during the neogene tropical taxa entered newly created montane area and montane taxa entered the tropical lowlands the general decrease of temperature during the upper neogene and especially during the quaternary glacial periods may have caused considerable extinctions in the lowlands representation of pollen of apparently principally montane taxa podocarpus hedyosmum in miocene pliocene and quaternary sediments of amazonia and surroundings is still di cult to interpret in terms of temperature decrease at low elevation changes in precipitation may have profound impact on the composition of vegetation communities ilex and melastomataceae increase signi cantly in many glacial pollen records increase of weinmannia in amazonian pollen records seems the best indicator of downward migration of montane vegetation belts a temperature lowering at sea level of 4 5 13c during the last glacial maximum lgm seems reasonable it may have caused a downslope migration of some 700 m of the lower montane vegetation belt lower montane arboreal species may have been able to grow in higher elevation areas 500 m of amazonia increasing background pollen values of montane taxa in the area di erence between a cool and wet middle pleniglacial 60 28 ka bp and a cold and dry upper pleniglacial 28 14 ka bp thus including the lgm is evident in andean and amazonian records statements about environmental conditions of the ice age amazon should be speci ed chronologically the middle pleniglacial is a time of accumulation of uvial sediments the upper pleniglacial is a time of incision of the rivers in their sediments sedimentation started again in the lateglacial since ca 13 ka bp and the holocene when lake levels rose again based on simpli ed considerations of precipitation changes and evaporation we estimate that lgm rainfall may have been reduced by values of ca 45 10 amazonian and cordilleran lakes dried up dry rain forest was locally replaced by savanna savanna forest or cerrado type vegetation dry rain forest savanna forest and pure savanna was locally replaced by extensive semi desert dune formations lower rio branco area in present day central amazonia the present day centers of higher rainfall 2500 mm surrounded by areas of lower rainfall are refuge areas of the very wet rain forest and of the very high plant diversity 300 plant species per 0 1 ha and they should have been that equally or more during the dry climate intervals plant diversity of drier forests is in the order of 100 150 species per 0 1 ha both extinction and speciation in isolation under precipitation and temperature stress may have taken place in these refugia 2000 elsevier science ltd all rights reserved

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

crustal scale block tilting during andean trench parallel extension structural and geo thermochronological insights despite a long history of plate convergence at the western margin of the south american plate that has been ongoing since at least the early paleozoic the southern peruvian fore arc displays little to no evidence of shortening in the light of this observation we assess the deformation history of the southern peruvian fore arc and its geodynamic implications to accomplish this we present a new structural and geo thermochronological data set zircon u pb mica 40ar 39ar apatite and zircon fission track and zircon u th he analyses for samples collected along a 400 km long transect parallel to the trench our results show that the mesoproterozoic gneissic basement was mainly at temperatures 350 c since the neoproterozoic and was later intruded by jurassic volcanic arc plutons along the coast a peculiar apatite fission track age pattern coupled with field observations and a synthesis of available geological maps allows us to identify crustal scale tilted blocks that span the coastal peruvian fore arc these blocks bounded by normal faults that are orthogonal to the trench suggest post 60 ma trench parallel extension that potentially accommodated oroclinal bending in this region block tilting is consistent with the observed and previously described switch in the location of sedimentary sources in the fore arc basin our data set allows us to estimate the cumulative slip on these faults to be less than 2 km and questions the large amount of trench parallel extension suggested to have accommodated this bending

stable isotope paleoaltimetry and the evolution of landscapes and life abstract reconstructing topography of our planet not only advances our knowledge of the geodynamic processes that shape the earth s surface equally important it adds a key element towards understanding long term continental moisture transport atmospheric circulation and the distribution of biomes and biodiversity stable isotope paleoaltimetry exploits systematic decreases in the oxygen 18o or hydrogen d isotopic composition of precipitation along a mountain front when the interaction of topography and advected moist air masses induces orographic precipitation these changes in 18o or d can be recovered from the geologic record and recent geochemical and modeling advances allow a broad range of proxy materials to be evaluated over the last 10 yr stable isotope paleoaltimetry has witnessed rapidly expanding research activities and has produced a broad array of fascinating tectonic and geomorphologic studies many of which have concentrated on determining the elevation history of continental plateau regions these single site studies have greatly expanded what used to be very sparse global paleoaltimetric data the challenge now lies in disentangling the surface uplift component from the impact of climate change on 18o and d in precipitation the robustness of stable isotope paleoaltimetry can be enhanced when high elevation 18o or d data are referenced against low elevation sites that track climate modulated sea level 18o or d of precipitation through time approach analysis of central andean paleosols documents that differences in 18o of soil carbonate between the subandean foreland and the bolivian altiplano are small between 11 and 7 ma but rise rapidly to ca 2 9 after 7 ma corroborating the magnitude of late miocene change in 18o on the altiplano future advances in stable isotope paleoaltimetry will greatly benefit from addressing four key challenges 1 identifying topographically induced changes in atmospheric circulation and associated teleconnections in the global climate system that affect 18o or d of precipitation 2 evaluating on a case by case basis if temporal and spatial changes in isotope lapse rates influence interpretations of paleoelevation 3 interfacing with phylogenetic techniques to evaluate competing hypotheses with respect to the timing of surface uplift and the diversification of lineages 4 characterizing feedbacks between changes in surface elevation and atmospheric circulation as these are likely to be equally important to the diversification of lineages than changes in surface elevation alone tackling these challenges will benefit from the accelerating pace of improved data model comparisons and rapidly evolving geochemical techniques for reconstructing precipitation patterns most importantly stable isotope paleoaltimetry has the potential to develop into a truly interdisciplinary field if innovative tectonic paleoclimatic and evolutionary biology phylogenetic approaches are integrated into a common research framework it therefore opens new avenues to study the long term evolution of landscapes and life

uplift history of the central and northern andes a review the elevation of the andean cordillera is a crucial boundary condition for both climatic and tectonic studies the andes affect climate because they form the only barrier to atmospheric circulation in the southern hemisphere and they intrigue geologists because they have the highest plateau on earth formed at a noncollisional plate margin the altiplano puna yet until recently few quantitative studies of their uplift history existed this study presents both 1 a review of the quantitative paleoelevation estimates that have been made for the central and colombian andes and 2 an examination of the source and magnitude of error for each estimate in the central andes paleobotanical evidence suggests that the altiplano puna had attained no more than a third of its modern elevation of 3700 m by 20 ma and no more than half its modern elevation by 10 7 ma these data imply surface uplift on the order of 2300 3400 m since the late miocene at uplift rates of 0 2 0 3 mm yr paleobotanical and geomorphological data suggest a similar uplift history for the eastern cordillera namely no more than half the modern elevation present by 10 ma no evidence exists for an exponential increase in uplift rate as has been interpreted from fissiontrack data these uplift rates mostly reflect mean surface uplift rather than rock uplift that is uplift of material points because little dissection of the western eastern cordillera has occurred south of lat 19 s and of the altiplano puna thus the central andean plateau appears to be young in the colombian andes paleobotanical data imply rapid uplift of the eastern cordillera between 2 and 5 ma at rates on the order of 0 6 3 mm yr however some of this uplift is likely rock uplift due to erosion driven isostatic rebound rather than mean surface uplift

effect of regional topography and hydrology on the lacustrine isotopic record of miocene paleoclimate in the rocky mountains drummond c n wilkinson b h lohmann k c and smith g r 1993 effect of regional topography and hydrology on the lacustrine isotopic record of miocene paleoclimate in the rocky mountains palaeogeogr palaeoclimatol palaeoecol 101 67 79 oxygen isotopic compositions of upper miocene 9 2 m y lacustrine limestone from northwestern wyoming range from 21 5 to 35 2 0 pdb and are the lightest yet reported for a non marine carbonate sequence these values require that lake water was greatly depleted in 180 relative to modern meteoric precipitation and indicate that most inflow was sourced as meltwater from glaciers in the adjacent gros ventre range assessment of climatic factors influencing the isotopic composition of global meteoric water indicates either that nearly all of miocene precipitation in the southern rocky mountains was derived from large lake systems in the snake river plain and northern great basin to the west or that gros ventre catchment elevations were up to 2300 m higher than at present because erosion rates in modern alpine regions suggest that subaerial denudation could only account for up to 1200 m of post miocene elevation reduction any additional lowering must reflect the influence of post laramide epeirogeny during basin and range extensional tectonism lacustrine isotopic data therefore provide boundary conditions on the timing and magnitude of changes in late cenozoic paleoclimate topography hydrology and tectonism in the western wyoming portion of the rocky mountains

refinement of eocene lapse rates fossil leaf altimetry and north american cordilleran surface elevation estimates abstract estimates of continental paleoelevation using proxy methods are essential for understanding the geodynamic climatic and geomorphoric evolution of ancient orogens fossil leaf paleoaltimetry one of the few quantitative proxy approaches uses fossil leaf traits to quantify differences in temperature or moist enthalpy between coeval coastal and inland sites along latitudes these environmental differences are converted to elevation differences using their rates of change with elevation lapse rate here we evaluate the uncertainty associated with this method using the eocene north american cordillera as a case study to do so we develop a series of paleoclimate simulations for the early 55 49 ma and middle eocene 49 40 ma period using a range of elevation scenarios for the western north american cordillera simulated eocene lapse rates over western north america are 5 c km and 9 8 kj km close to moist adiabatic rates but significantly different from modern rates further using linear lapse rates underestimates high altitude 3 km temperature variability and loss of moist enthalpy induced by non linear circulation changes in response to increasing surface elevation ignoring these changes leads to kilometer scale biases in elevation estimates in addition to these biases we demonstrate that previous elevation estimates of the western cordillera are affected by local climate variability at coastal fossil leaf sites of up to 8 c in temperature and 20 kj in moist enthalpy a factor which further contributes to elevation overestimates of 1 km for early eocene floras located in the laramide foreland basins and underestimates of 1 km for late middle eocene floras in the southern cordillera we suggest a new approach for estimating past elevations by comparing proxy reconstructions directly with simulated distributions of temperature and moist enthalpy under a range of elevation scenarios using this method we estimate mean elevations for the north american cordillera of 2 km using proxy temperatures and 3 km using proxy moist enthalpy this discrepancy is likely related to an inconsistency between the proxy data for temperature and moist enthalpy the combination of temperature and moist enthalpy estimates implies a warm and dry environment which is inconsistent with geological evidence for humid conditions our study emphasizes that lapse rates in warm climate were likely much different than today s and highlights the advantages of using climate models to understand past climate states and regional circulation patterns to derive more accurate paleoelevation estimates using proxy temperature and moist enthalpy

pliocene orographic barrier uplift in the southern central andes sedimentary basin fills along the windward flanks of orogenic plateaus are valuable archives of paleoenvironmental change with the potential to resolve the history of surface uplift and orographic barrier formation the intermontane basins of the southern central andes contain thick successions of sedimentary material that are commonly interbedded with datable volcanic ashes we relate variations in the hydrogen isotopic composition of hydrated volcanic glass delta d g of neogene to quaternary fills in the semiarid intermontane humahuaca basin eastern cordillera northwest argentina to spatiotemporal changes in topography and associated orographic effects delta d values from volcanic glass in the basin strata 117 parts per thousand to 98 parts per thousand show two main trends that accompany observed tectonosedimentary events in the study area between 6 0 and 3 5 ma delta d g values decrease by similar to 17 parts per thousand this is associated with surface uplift in the catchment area after 3 5 ma delta d g values show abrupt deuterium enrichment which we associate with 1 the attainment of threshold elevations for blocking moisture transport in the basin bounding ranges to the east and 2 the onset of semiarid conditions in the basin such orographic barriers throughout the eastern flanks of the central andes have impeded moisture transport into the orogen interior this has likely helped maintain aridity and internal drainage conditions on the adjacent andean plateau

modern and long term evaporation of central andes surface waters suggests paleo archives underestimate neogene elevations abstract central andean paleoelevations reconstructed from stable isotope and paleofloral data imply a large magnitude 2 km miocene to modern surface uplift however the isotopic relationships between precipitation surface waters and soil waters upon which these reconstructions are based remain poorly constrained for both past and in many cases modern conditions we quantify the relationships between central andean precipitation and surface waters by measuring the isotopic composition of 249 stream water samples 18o and d collected between april 2009 and october 2012 the isotopic compositions of stream waters match precipitation along the eastern flank in contrast altiplano surface waters possess a lower d 18o slope 4 59 vs 8 for meteoric waters not observed in precipitation which signals heavy isotope evaporative enrichment in surface waters paleoclimate models indicate that highly evaporative conditions have persisted on the plateau throughout andean uplift and that conditions may have been more evaporative when the andes were lower thus more ancient proxy materials may have a greater evaporative bias than previously recognized and paleoelevation reconstructions from stable isotope based central andean plateau proxy materials likely overstate miocene to present surface uplift we propose altiplano paleoelevations of 1 2 km at 24 5 ma 1 5 2 9 km by 11 45 ma and modern elevations by 6 ma based on the lightest isotopic compositions observed in altiplano proxy materials which are least likely to be influenced by evaporation these constraints limit total late miocene to modern uplift to

influence of andean uplift on climate and paleoaltimetry estimates article i nfo article history recent elevation reconstructions of the andean plateau suggest a rapid 2 5 1 0 km rise of the central andes between 10 and 6 ma this rapid rise has been attributed to a catastrophic removal of a dense lithospheric mantle root beneath the andes however these findings are based on the assumption that climate did not change during deposition of paleoaltimetry proxies here we evaluate south american climate change due to andean uplift and its influence on interpretations of plateau elevation from climate sensitive paleoaltimetry data a series of experiments are presented using the regcm3 regional general circulation model rcm to characterize changes in andean precipitation amount surface temperature and wind direction vapor source as a function of changing plateau elevation results indicate that south american and andean climate changed significantly in response to plateau growth more specifically rising of the plateau results in up to a 900 mm increase in rainy season december january february precipitation over the plateau plateau uplift also results in a decrease in non adiabatic surface temperature of up to 6 5 c in addition to adiabatic cooling directly related to elevation change through the lapse rate finally the prevailing wind direction and the vapor source for precipitation switches from the south pacific ocean to the equatorial atlantic as plateau elevation increases above of its present day elevation taken together these changes in paleoclimate would have substantially depleted the oxygen isotopic concentration of paleoprecipitation through the cenozoic unless this climatic effect is taken into consideration paleoaltimetry reconstructions based on stable isotope methods may overestimate the rapid rise of the andes by up to several kilometers we conclude that some or all of the apparent rapid rise of the andean plateau from paleoaltimetry data could be an artifact of large changes in paleoclimate

modern precipitation δ18o and trajectory analysis over the himalaya tibet orogen from echam5 wiso simulations variations in oxygen isotope ratios 18o measured from modern precipitation and geologic archives provide a promising tool for understanding modern and past climate dynamics and tracking elevation changes over geologic time in areas of extreme topography such as the tibetan plateau the interpretation of 18o has proven challenging this study investigates the climate controls on temporal daily and 6 h intervals and spatial variations in present day precipitation 18o 18op across the tibetan plateau using a 30 year record produced from the european centre hamburg echam5 wiso global atmospheric general circulation model gcm results indicate spatial and temporal agreement between model predicted 18op and observations large daily 18op variations of 25 to 5 occur over the tibetan plateau throughout the 30 simulation years along with interannual 18op variations of 2 analysis of extreme daily 18op indicates that extreme low values coincide with extreme highs in precipitation amount during the summer monsoon vapor transport from the north and southwest of the plateau generally corresponds with high 18op whereas vapor transport from the indian ocean corresponds with average to low 18op thus vapor source variations are one important cause of the spatial temporal differences in 18op comparison of gcm and rayleigh distillation model rdm predicted 18op indicates a modest agreement for the himalaya region averaged over 86 94 e confirming application of the simpler rdm approach for estimating 18op lapse rates across himalaya

high level surfaces plateau uplift and foreland development bolivian central andes newly dated tertiary strata in the bolivian central andean plateau and synthesis of the tertiary record in the adjacent subandean fold thrust belt constrain the age of deformation in both regions age of deformation within the plateau is determined by dated crosscutting relations associated with a regionally extensive high level surface known as the san juan del oro surface new 40 ar 39 ar dates on undeformed strata above the high level surface preclude significant upper crustal shortening within the eastern cordillera after 10 ma tertiary strata within the adjacent subandean region demonstrate that formation of the fold thrust belt occurred after 10 ma on the basis of these data we propose a two stage model of late cenozoic andean growth that links plateau uplift to the development of the fold thrust belt in the first stage early plateau uplift occurred in response to widespread compressional deformation of the plateau eastern cordillera and altiplano during the second stage beginning after 10 ma upper crustal deformation within the plateau terminated and the subandean fold thrust belt developed crustal scale eastward thrusting along the eastern margin of the eastern cordillera drove subandean folding and thrusting the eastern cordillera served as the bulldozer for the deforming subandean wedge

the inverse altitude effect of leaf wax derived n alkane δd on the northeastern tibetan plateau the response of soil wax derived n alkane hydrogen isotope values ddwax the abundance weighted average dd values of the c29 and c31 n alkanes and isotopic lapse rates the average change in ddwax with elevation to factors other than elevation change should be assessed and taken into account for quantitative elevation reconstructions to shed more light on how plant wax derived n alkanes may be used for this purpose soil and gramineae samples analyzed for ddwax values those were derived from the foreland basin the mountain vegetation zone and glacier catchment areas along the beida river a tributary in the heihe river basin up to the headwaters of the qiyi glacier and the xiying river catchment up to the headwaters and glaciated areas of the lenglong range located on the northeastern tibetan plateau for comparison this study analyzed surface soils from the maxian mountains for ddwax as a whole the trend in ddwax in the study regions seems to primarily reflect ddrw dd values of river water and or ddp dd values of precipitation these data show good inverse linear relationships between gramineae and soil ddwax values and elevation altitude effect in the mountain vegetation zone of the xiying river catchment 2200 3500 m and maxian mountains 2800 3700 m where the elevation effect becomes the main control factor even in the dry qilian mountains however at the low elevation sites soil and gramineae ddwax values from the xiying river 1750 2200 m and maxian mountains 2060 2800 m show the inverse altitude effect the recycled fraction and trajectory of water vapor may result in these positive ddwax elevation gradients in dry continental settings the inverse altitude effect has also been observed in periglacial regions below the qiyi glacier and from the lenglong range we interpret this effect as evidence of stronger fractionation processes occurring in the freeze thaw mass exchange between the solid and liquid phases at high elevations thus the inverse altitude effect can be attributed to the decrease of precipitation amount in the upper valley and to marked fractionation in soil water and the residual or melting snow in periglacial regions which may complicate the isotope thermometry when interpreting changes of long term dd and d 18

giant landslide triggerings and paleoprecipitations in the central western andes the aricota rockslide dam south peru abstract the central part of the western andes holds an exceptional concentration of giant paleolandslides involving very large volumes of rock material v km3 while those gravitational slope failures are interpreted consensually as an erosional response to the geodynamic activity of the andes relief formation and tectonic activity the question of their triggering mechanisms remains enigmatic to clarify the respective roles of climatic versus seismic forcing on the andean landslides new temporal constraints on paleo movements are essential here we focus on one of those giant slope failures the aricota giant rockslide that damned the locumba valley in southern peru we conducted fieldwork high resolution dem analysis and cosmogenic nuclide dating to decipher its development history and failure mechanisms our results point to the occurrence of two successive events a giant failure mobilizing a rock volume of ca 2 km3 first produced a dam at 17 9 0 7 ka considering its height of ca 600 m the aricota rockslide dam is one of the three largest landslide dams worldwide at 12 1 0 2 ka a second event produced ca 0 2 km3 of material and the rock avalanche debris spread out over the dam as the chronology of those two events is pointing to the two main paleoclimatic pluvial periods in this region heinrich stadial 1a and younger dryas we favor the interpretation of a climatic forcing at a regional scale the concomitant aggradation of alluvial terraces and fan systems along the nearby valleys highlights higher regional erosion sediments supply and mass wasting events during those paleoprecipitation events and strengthens this conclusion

late cenozoic topographic evolution of the eastern cordillera and puna plateau margin in the southern central andes nw argentina abstract the andes constitute an important orographic barrier in the southern hemisphere impacting atmospheric circulation the amount and distribution of rainfall and earth surface processes in a highly asymmetric manner in the central andes of nw argentina the andean plateau puna and the intermontane basins of the adjacent eastern cordillera constitute geological archives that furnish spatiotemporal information on surface uplift and associated paleo environmental change today rainfall in nw argentina is focused along the windward flanks of the eastern cordillera while its intermontane basins and the puna constitute high elevation regions with strongly reduced rainfall the present day influence of these topographic characteristics on precipitation patterns is reflected by systematic changes in the hydrogen stable isotope ratios of meteoric water proxy archives from basin strata record past environmental conditions and provide insight into the nature of topographic growth through time we present 34 new hydrogen isotopic compositions of volcanic glass dg extracted from tuffs interbedded with the sedimentary deposits of three different regions across the eastern andean margin between ca 24 s and 25 s latitude combined with new zircon u pb geochronology our data show clear spatiotemporal variations in dg correlating with topographic growth and ensuing orographic effects during the miocene and pleistocene in particular variations in dg indicate that the pastos grandes puna and the toro eastern cordillera basins had attained modern elevations by ca 8 and 6 ma respectively a strong positive shift in the dg record of the toro basin after 840 ka coincides with deposition of thick fluvial alluvial conglomerates suggesting orographically induced aridification due to progressive range uplift to the east other dg records from the eastern cordillera show similar but diachronous events emphasizing the importance of regional tectonics for environmental change with implications for the formation of orogenic plateaus

realistic initiation and dynamics of the madden julian oscillation in a coarse resolution aquaplanet gcm 1 the main mechanisms for the initiation and propagation of the madden julian oscillation mjo are still widely debated the capacity of operational global climate models gcms to correctly simulate the mjo is hindered by the inadequacy of the underlying cumulus parameterizations here we show that a coarse resolution gcm coupled to a simple multicloud model parameterization mimicking the observed dynamics and physical structure of organized tropical convection simulates the mjo in an idealized setting of an aquaplanet without ocean dynamics we impose a fixed nonhomogeneous sea surface temperature replicating the indian ocean western pacific warm pool this results in a succession of mjos with realistic phase speed amplitude and physical structure each mjo event is initiated at a somewhat random location over the warm pool and dies sometimes near the eastern boundary of the warm pool and sometimes at a random location way beyond the warm pool also occasionally the mjo events stall at the center of maximum heating this is reminiscent of the fact that in nature some mjos stall over the maritime continent while others reach the central pacific ocean and beyond the initiation mechanism in the model is believed to be a combination of persistent intermittent convective events interacting with observed large scale flow patterns and internal tropical dynamics the large scale flow patterns are associated with planetary scale dry kelvin waves that are triggered by preceding mjo events and circle the globe while congestus cloud decks on the flanks of the warm pool are believed to force rossby gyres which then funnel moisture toward the equatorial region

stable carbon isotopic variation of long chain n alkanoic acids in the equatorial pacific sediments over the last 40 ma implications for expansion of c4 grassland in south america abstract the stable carbon isotope ratio 13 c values of sedimentary long chain c 20 n alkanoic acids from the equatorial pacific iodp sites u1331 1338 were measured for historical reconstruction of c 4 plant contribution from south america over the last 40 ma the values for c 30 and c 32 acids ranged between 36 9 and 25 4 suggesting that they likely originated from higher plant wax associated with c 3 dominated vegetation the molecular distribution of alkanoic acids in the sediments showed a marked change across the intertropical convergence zone itcz indicating a potential contribution from the northern hemisphere to the sediments located at 10 n in contrast the abundances of n alkanoic acids significantly decreased in the sediments at 13 c values suggest that the differences in the core locations possibly caused north and southward shifts of ca 1 0 n and ca 0 5 s from the equator respectively the corrected 13 c values of c 30 and c 32 acids did not cross the c 3 end member threshold until 1 7 ma despite the onset of c 4 plants in central south america at ca 7 ma this implies that vegetation in the low latitudes of south america was less affected by hydrological changes induced by the uplift of the andes during the late miocene

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

propagating and nonpropagating mjo events over maritime continent abstractthe observed outgoing longwave radiation olr and era interim data during 1979 2008 from november to april were analyzed to reveal fundamental differences between eastward propagating ep and nonpropagating np mjo events across the maritime continent mc it was found that when the maximum mjo convection arrives near 120 e a positive moisture tendency lies in a longitudinal zone 10 s 10 n 130 170 e for the ep cases whereas a negative tendency appears in the same region for the np cases in the latter cases there are clearly detectable westward propagating rossby wave type dry signals over the equatorial central western pacific the dry rossby wave signal may hinder the development of new convection to the east of the mjo convective center preventing the eastward propagation of the mjo a moisture budget analysis shows that the positive tendency of specific humidity in the ep composite is mainly attributed to the advection of the mean moisture by an intraseasonal ascending motion ano

temporal variation in the stress field of the aegean region we use a forward numerical model to analyse the intra plate stress field in an area of active extension of continental lithosphere the aegean region recent tomographic images of the hellenic subduction zone offer the unique opportunity to address the relation between the evolving aegean stress field and temporal variations in the subduction process to this extent we apply our model to both the present day and the late pliocene situation regarding the current situation it is found that subduction related forces largely explain the observed pattern of tension results obtained for the pliocene indicate that detachment of the slab subducted below western greece may have controlled the observed temporal variation in the pattern of tension

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

tectonic evolution of the central andean plateau and implications for the growth of plateaus current end member models for the geodynamic evolution of orogenic plateaus predict a slow and steady rise during crustal shortening and ablative subduction i e continuous removal of the lower lithosphere or b rapid surface uplift following shortening which is associated with punctuated removal of dense lower lithosphere and or lower crustal flow this review integrates results from recent studies of the modern lithospheric structure geologic evolution and surface uplift history of the central andean plateau to evaluate the geodynamic processes involved in forming it comparison of the timing magnitude and distribution of shortening and surface uplift in combination with other geologic evidence highlights the pulsed nature of plateau growth we discuss specific regions and time periods that show evidence for end member geodynamic processes including middle late miocene surface uplift of the southern eastern cordillera and altiplano associated with shortening and ablative subduction latest

spatial and temporal uplift history of south america from calibrated drainage analysis a multi disciplinary approach is used to analyze the cenozoic uplift history of south america residual depth anomalies of oceanic crust abutting this continent help to determine the pattern of present day dynamic topography admittance analysis and crustal thickness measurements indicate that the elastic thickness of the borborema and altiplano regions is 10 km with evidence for sub plate support at longer wavelengths a drainage inventory of 1827 river profiles is assembled and used to investigate landscape development linear inverse modeling enables river profiles to be fitted as a function of the spatial and temporal history of regional uplift erosional parameters are calibrated using observations from the borborema plateau and tested against continent wide stratigraphic and thermochronologic constraints our results predict that two phases of regional uplift of the altiplano plateau occurred in neogene times regional uplift of the southern patagonian andes also appears to have occurred in early miocene times the consistency between observed and predicted histories for the borborema altiplano and patagonian plateaux implies that drainage networks record coherent signals that are amenable to simple modeling strategies finally the predicted pattern of incision across the amazon catchment constrains solid sedimentary flux at the foz do amazonas observed and calculated flux estimates match suggesting that erosion and deposition were triggered by regional andean uplift during miocene times

87sr 86sr in recent accumulations of calcium sulfate on landscapes of hyperarid settings a bimodal altitudinal dependence for northern chile 19 5 s 21 5 s an elevation dependent relationship of the 87sr 86sr ratio of holocene surface accumulations of sulfate salts is demonstrated for a continental margin hyperarid setting in the atacama desert of northern chile gypsum and anhydrite of multiple origins exist widely on superficial materials that originated during the last 10 000 years an important source of calcium sulfate is from offshore generated stratocumulus clouds that are advected onto the continent where they generate fog that transfers water droplets to the ground surface which upon evaporation leaves calcium sulfate crystals meteorological measurements of the cloud base and top altitudes average 400 m and 1100 m above sea level masl respectively the seawater ratio of 87sr 86sr 0 70917 is distinctively higher than that reported for weathered mean andean rock less than 0 70750 samples of 28 modern surface salt accumulations for locations between 200 and 2950 masl and between 19 30 and 21 30 s verify that 87sr 86sr varies as a function of site altitude sites below 1075 masl and above 225 masl display calcium sulfate 87sr 86sr of mean value 0 70807 0 00004 while the ratio outside this altitudinal domain is 0 70746 0 00010 thus the 87sr 86sr ratio of holocene salt accumulations differentiates two altitudinal domains

can stable isotopes ride out the storms the role of convection for water isotopes in models records and paleoaltimetry studies in the central andes abstract globally changes in stable isotope ratios of oxygen and hydrogen o 18 and d in the meteoric water cycle result from distillation and evaporation processes isotope fractionation occurs when air masses rise in elevation cool and reduce their water vapor holding capacity with decreasing temperature as such o 18 and d values from a variety of sedimentary archives are often used to reconstruct changes in continental paleohydrology as well as paleoaltimetry of mountain ranges based on 234 stream water samples we demonstrate that areas experiencing deep convective storms in the eastern south central andes 22 28 s do not show the commonly observed relationship between o 18 and d with elevation these convective storms arise from intermontane basins where diurnal heating forces warm air masses upward resulting in cloudbursts and raindrop evaporation especially at the boundary between the tropical and extra tropical atmospheric circulation regimes where deep convective storms are very common 26 to 32 n and s the impact of such storms may yield non systematic stable isotope elevation relationships as convection dominates over adiabatic lifting of air masses because convective storms can reduce or mask the depletion of heavy isotopes in precipitation as a function of elevation linking modern or past topography to patterns of stable isotope proxy records can be compromised in mountainous regions and atmospheric circulation models attempting to predict stable isotope patterns must have sufficiently high spatial resolution to capture the fractionation dynamics of convective cells

long term stability of hydrogen isotope ratios in hydrated volcanic glass abstract the advancement of conceptual and numerical geodynamic models necessitates quantitative orogen scale paleoelevation data felsic volcanic glasses which record the hydrogen isotope compositions d of meteoric water shortly after deposition provide several advantages as a paleoelevation proxy questions remain however about the reliability of this relatively new proxy including the effect of hydrofluoric hf acid abrasion in the preparation of glass shards for hydrogen isotope analysis and the stability of hydrogen isotope ratios in hydrated glass shards over geologic time 10 6 10 7 years hf acid abrasion of natural ancient glass shards results in systematic shifts in glass d values away from modern water d values to evaluate the effectiveness of hf acid abrasion we treated 70 150 m glass shards separated from various natural tephras with deuterium labeled water dlw d 18 205 for up to 400 days for all glasses this treatment resulted in elevated d values in comparison to untreated samples hf acid abrasion after dlw exposure however removed this effect and restored glass shards to their original untreated d values in samples older than 10 4 years hf acid abrasion removes hydrous alteration precipitates at the glass surface without measurably changing the d values of the underlying hydrated glass regardless of abrasion duration or glass composition additionally 45 34 ma glasses record d values that directly reflect their depositional environments as determined by stratigraphy glasses from tuffs deposited in demonstrably evaporative lacustrine environments have relatively high d values compared to glasses from contemporaneous tuffs deposited in nearby fluvial environments which have much lower d values the preservation of d values that systematically vary with original depositional environment despite 30 myr of post hydration exposure to the same meteoric water indicates that these volcanic glasses resisted measurable h isotope exchange on geologic timescales this research supports the use of natural felsic glass separates for paleoaltimetry and demonstrates the necessity of hf acid abrasion and glass shard isolation in sample preparation methods

seasonality in the madden julian oscillation abstract this study using observational data and global reanalysis products synthesizes existing knowledge on the seasonality in the madden julian oscillation mjo and discusses its possible dependence on the mean background state the seasonality in the mjo is documented in terms of its components in low level zonal wind and precipitation a single peak season boreal winter exists near the equator in the indian and western pacific oceans for the broad tropical region however the seasonality in the mjo is featured by a latitudinal migration across the equator between two peak seasons the primary peak season is in boreal winter december march during which mjo signals are mainly confined to the indian and western pacific ocean and reach their maxima in the south pacific convergence zone the secondary peak season is boreal summer june september during which the strongest mjo occurs north of the equator from the bay of bengal to the south china sea and another separated region of strong mjo

simulations of warm tropical conditions with application to middle pliocene atmospheres during the early and mid pliocene the period from 5 to 3 million years ago approximately the earth is believed to have been significantly warmer than it is today but the reasons for the higher temperatures are unclear this paper explores the impact of recent findings that suggest that at that time cold surface waters were absent from the tropical and subtropical oceanic upwelling zones el nino was in effect a perennial rather than intermittent phenomenon and sea surface temperatures in low latitudes were essentially independent of longitude when these conditions are specified as the lower boundary condition for an atmospheric gcm we find that the trade winds along the equator and hence the walker circulation collapse the low level stratus clouds in low latitudes diminish greatly thus reducing the albedo of the earth the atmospheric concentration of water vapor increases and enhanced latent heat release due to stronger evaporation warms up the tropical atmosphere particularly between 40 s and 20 n moreover teleconnection patterns from the pacific induce a warming over north america that is enhanced by surface albedo feedback a process that may have helped to maintain this region ice free before 3 ma the results presented here indicate that the suggested absence of cold surface waters from the tropical and subtropical oceanic upwelling zones could have contributed significantly to the pliocene warmth

topographic development of the southern alps recorded by the isotopic composition of authigenic clay minerals south island new zealand abstract the southern alps are developing as a consequence of oblique collision between the pacific and australian plates the southern alps lie on the west side of the south island of new zealand and create a massive rain shadow where greater than 12 m year of rain falls on the west coast and semiarid conditions exist to the east the rain out effect across the mountains causes precipitation west of the southern alps to have d and 18 o values averaging 30 and 5 5 whereas precipitation in the rain shadow to the east is isotopically lighter d 72 and 18 o 9 8 such large differences in the isotopic composition of precipitation would not have existed prior to the development of significant topography we have examined the topographic evolution of the southern alps using oxygen isotope analyses of authigenic kaolinites formed in the rain shadow to the east of the mountains between the cretaceous low topography and the pleistocene changes in the isotopic composition of authigenic clay minerals forming in equilibrium with meteoric water in the stratigraphic sequence record the development of southern alps topography and the resultant rain shadow our oxygen isotope analyses of authigenic kaolinites show a 5 6 decrease in the early pliocene from 18 2 in older rocks to 12 3 in younger rocks in addition smectite is abundant in all samples from the late miocene to recent but is conspicuously absent in most older rocks suggesting a change to a generally drier climate roughly coincident with the isotopic shift in kaolinites this method may be useful in unraveling timing of development of mountain belts elsewhere in the world

andean elevation control on tropical pacific climate and enso late cenozoic marine proxy data record a long term transition in the tropical pacific from el nino like conditions with reduced zonal sea surface temperature sst gradient deepened thermocline and reduced upwelling in the eastern equatorial pacific eep to conditions similar to modern this transition coincides with kilometer scale uplift of the central andes to understand whether the rise of the andes contributed to tropical pacific climate evolution we performed experiments with the national center for atmospheric research s community climate system model version 4 to quantify changes in tropical pacific climate and el nino southern oscillation as a function of andean elevations our results demonstrate that uplift increases the equatorial east west sst gradient and walker circulation the rise of the andes from 1 to 3 km increases the sst gradient by 0 8 c and walker circulation by 60 due to strengthened radiative cooling by enhanced low cloud formation in the eep this cooling effect is largest in the southeastern tropical pacific and accounts for about one half of the reconstructed sst cooling along the peru coast the uplift also strengthens upwelling north of the eep consistent with documented increases in biological productivity in this region and decreases the frequency of el nino southern oscillation and the number of strong el nino events simulated responses to andean uplift are generally consistent with the late cenozoic proxy records but too small in magnitude taken together our results indicate that andean uplift was likely one of the multiple factors that contributed to the long term evolution of both the mean climate state and the interannual variability in the tropical pacific

neogene climate change and uplift in the atacama desert chile the relationship between andean uplift and extreme desiccation of the west coast of south america is important for understanding the interplay between climate and tectonics in the central andes yet it is poorly understood here we use soil morphological char acteristics salt chemistry and mass independent fractionation anomalies 17 o values in dated paleosols to reconstruct a middle miocene climatic transition from semiaridity to extreme hyperaridity in the atacama desert paleosols along the southeastern margin of the calama basin change from calcic vertisols with root traces slickensides and gleyed horizons to an extremely mature salic gypsisol with pedogenic nitrate we interpret this transition which occurred between 19 and 13 ma to represent a change in precipitation from 200 mm yr to 20 mm yr this drastic reduction in precipitation likely resulted from uplift of the central andes to elevations 2 km the uplift blocked moisture from the south american summer monsoon from entering the atacama the mid miocene gyp sisol with pedogenic nitrate is located at elevations between 2900 and 3400 m in the cal ama basin significantly higher than modern nitrate soils which occur below 2500 m modern and quaternary soils in this elevation zone contain soil carbonate and lack ped ogenic gypsum and nitrate we infer that 900 m of local surface uplift over the past 10 m y displaced these nitrate paleosols relative to modern nitrate soils and caused a return to wetter conditions in the calama basin by decreasing local air temperatures and creating an orographic barrier to pacific air masses

impact of topography climate and moisture sources on isotopic composition δ 18 o δ d of rivers in the pyrenees implications for topographic reconstructions in small orogens understanding how orogenic topography controls the spatial distribution and isotopic composition of precipitation is critical for paleoaltitudinal reconstructions here we determine the isotopic composition o and d of 82 small rivers and springs from small catchments in the pyrenees calculation of the deuterium excess d excess parameter allows the distinction of four distinct isotopic provinces with d excess values of between 15 and 22 in the northwest between 7 and 14 in the central northern pyrenees and between 3 and 11 in the northeast the southern pyrenees have a homogenous d excess signature ranging from 7 to 14 our results show significant local moisture recycling and or rain amount effect in the northwestern pyrenees and control by evaporation processes during rainfall events in the southern pyrenees and for low elevated samples of the northeast of the range based on the distribution of d excess values we estimate contrasting isotope lapse rates of 2 9 21 4 km o d in the northwest 2 7 21 4 km o d in the north central and 3 7 31 7 km o d in the northeastern pyrenees the southern pyrenees show distinctly higher lapse rates of 9 5 77 5 km o d indicating that in this area the altitudinal effect in not the only parameter driving isotopic composition of rivers despite their relatively low topographic gradient the pyrenees exert a direct control on the isotopic composition of river waters especially on their northern side the variations in isotopic composition elevation relationships documented along the strike of the range are interpreted to reflect an increasing continentality effect driven by wind trajectories parallel to the range and mixing with mediterranean air masses despite these effects the measurable orographic effect on precipitation in the pyrenees proves that the isotopic composition approach for reconstructing past topography is applicable to low elevation orogens

onset of convective rainfall during gradual late miocene rise of the central andes a decrease in the ratio of 18o to 16o 18o of sedimentary carbonate from the bolivian altiplano has been interpreted to indicate rapid surface uplift of the late miocene andean plateau ap here we report on paleoclimate simulations of andean surface uplift with an atmospheric general circulation model gcm that tracks oxygen isotopes in vapor the gcm predicts changes in atmospheric circulation and rainfall that influence ap isotopic source and amount effects on eastern ap slopes summer convective precipitation increases by up to 6 millimeters per day 500 for plateau elevations that are greater than about 2000 meters high precipitation rates enhance the isotope amount effect leading to a decrease in precipitation 18o at high elevations and an increase in 18o lapse rate our results indicate that late miocene 18o depletion reflects initiation and intensification of convective rainfall

late cenozoic surface uplift of the southern sierra nevada california usa a paleoclimate perspective on lee side stable isotope paleoaltimetry late cenozoic surface uplift of the southern sierra nevada sierra california united states is widely debated recent interpretations of lee side isotope records from the southern sierra suggest that the elevation of the southern sierra has been sufficiently high to induce atmospheric flow patterns similar to modern patterns since the mid miocene at ca 12 ma the tendency for flow to deflect around a topographic barrier can be determined by the atmospheric stability barrier height and incoming wind speed we test the sensitivity of flow deflection to elevation to determine what elevation would have been sufficiently high to establish modern flow patterns in the mid miocene using global paleoclimate models and idealized regional weather models we find that the miocene atmosphere was more stable than modern we suggest that in a miocene climate flow patterns similar to modern pat terns could have been achieved for elevations as low as 2 km and that while miocene lee side isotope records from the southern sierra may indicate that the southern sierra has been a longstanding topographic feature they may not have changed significantly in response to proposed late cenozoic surface uplift of the southern sierra

propagation of the madden julian oscillation through the maritime continent and scale interaction with the diurnal cycle of precipitation the convectively active part of the madden julian oscillation mjo propagates eastward through the warm pool from the indian ocean through the maritime continent the indonesian archipelago to the western pacific the maritime continent s complex topography means the exact nature of the mjo propagation through this region is unclear model simulations of the mjo are often poor over the region leading to local errors in latent heat release and global errors in medium range weather prediction and climate simulation using 14 northern winters of trmm satellite data it is shown that where the mean diurnal cycle of precipitation is strong 80 of the mjo precipitation signal in the maritime continent is accounted for by changes in the amplitude of the diurnal cycle additionally the relationship between outgoing long wave radiation olr and precipitation is weakened here such that olr is no longer a reliable proxy for precipitation the canonical view of the mjo as the smooth eastward propagation of a large scale precipitation envelope also breaks down over the islands of the maritime continent instead a vanguard of precipitation anomalies of 2 5 mm day 1 over 10 6 km 2 jumps ahead of the main body by approximately 6 days or 2000 km hence there can be enhanced precipitation over sumatra borneo or new guinea when the large scale mjo envelope over the surrounding ocean is one of suppressed precipitation this behaviour can be accommodated into existing mjo theories frictional and topographic moisture convergence and relatively clear skies ahead of the main convective envelope combine with the low thermal inertia of the islands to allow a rapid response in the diurnal cycle which rectifies onto the lower frequency mjo hence accurate representations of the diurnal cycle and its scale interaction appear to be necessary for models to simulate the mjo successfully

role of topography on the mjo in the maritime continent a numerical case study the role of topography on a madden julian oscillation mjo event in the maritime continent mc is explored using a regional model four simulations are conducted lower resolution 12 km simulations using cumulus parameterization in the presence lr and absence lr flat of topography and higher resolution 4 km simulations without cumulus parameterization in the presence hr and absence hr flat of topography in the lr simulation the mjo remains unorganized with no clear eastward propagation while the lr flat simulation captures the mjo and its eastward propagation across the mc in the absence of cumulus parameterization both hr and hr flat capture the mjo and show several similarities and differences compared to the lr and lr flat simulations to better understand these differences a moisture budget analysis is conducted during the passage of the mjo in the lr flat simulation vertical advection of moisture is increased to the east of the islands leading to continuity in mjo associated convection continuity that was not present in the lr simulation the increase in vertical advection in the absence of topography is due to an increase in the mean moisture advection by the anomalous vertical winds in the middle of the mc horizontal advection seems to be the most important for an uninterrupted eastward propagation of the mjo the increase in the horizontal advection in the absence of topography is primarily due to an increase in the anomalous moisture advection by the mean zonal winds to what extent the mjo was influenced by the upstream effect from the new guinea topography was also explored these results indicate that the important physical processes for mjo associated convection may be different in different parts of the mc further implications of these results in the context of other recent studies on mjo propagation across the mc are discussed

stable isotope composition of precipitation across the southern patagonian andes 1 a surface water and precipitation transect across the southern patagonian andes at 47 48 s was conducted to assess how mountains affect the isotopic composition of precipitation this westerly wind region derives its moisture that falls as precipitation from the pacific orographic uplift of air over the andes causes pseudoadiabatic cooling and orographic precipitation on the western side and a strong rain shadow on the eastern side of the mountains these processes also produce a profound isotopic rain shadow with 18o values 4 lower in the east compared to the west on the windward western side of the andes the isotope values of precipitation and surface waters show weak although systematic trends with elevation but a pronounced correlation with distance from the main source of moisture pacific ocean a rayleigh simulation of precipitation 18o values as a function of condensation altitude matches our data well suggesting that other processes such as mixing of water sources and postcondensation evaporation are negligible and that topography is the dominant control on the isotope ratio of precipitation in contrast isotope ratios of waters on the leeward eastern side of the southern patagonian andes vary neither with elevation nor with distance from the mountains consistent with much of the precipitation on the leeward side being derived from precipitation carried over the andes by winds thus paleoprecipitation isotopic composition on the leeward side of orogens in similar climatic settings single moisture source and cool climate yield useful estimates of the elevation of these orogens but not local elevation

impacts of andean uplift on the humboldt current system a climate model sensitivity study 1 using both an atmospheric global circulation model and a regional oceanic model we assess the impact of the andes uplift on the humboldt current system hcs with three topographic scenarios for the andes we show that the uplift played a crucial role in shaping the lower troposphere dynamics over the pacific ocean and in turn affected the physical characteristics of the system our results show that the uplift has triggered a marked southward shift of the hcs changing the latitudinal position of coastal upwelling areas as well as the strength of the south pacific gyre our oceanic modeling experiments show that the latitudinal pattern of sea surface temperatures is dramatically modified with reduced andes with anomalies reaching up to 3 c we discuss the feedbacks of these changes on south american climate as well as the potential onset of an altitudinal threshold that would have had triggered these changes

response of meteoric δ18o to surface uplift implications for cenozoic andean plateau growth abstract the timing and magnitude of surface uplift provide important constraints on geodynamic models of orogen formation oxygen isotope 18 o and mass 47 isotopolog 47 compositions from terrestrial carbonate sediments have been used with modern isotope and temperature lapse rates to infer past surface elevations of the andes however these paleoaltimetry interpretations are contentious because variations in the oxygen isotope composition in meteoric water 18 o p are caused by changes in elevation orographic and regional climate here we use a limited domain isotope tracking general circulation model to simulate changes in 18 o p and isotopic lapse rates in response to andean surface uplift and to re evaluate 18 o and 47 changes in late miocene carbonates previously associated with rapid andean growth results indicate that andean surface uplift leads to changes in low level atmospheric circulation and an increase in precipitation along the eastern andean flank which influences isotopic source and amount effects simulated changes in andean 18 o p are not systematic with an increase in surface elevation but are instead a function of orographic thresholds that abruptly change regional climate a 18 o p decrease of 5 over the central andes and an increase in isotopic lapse rates up to 0 8 km 1 coincide with andean surface uplift from 75 to 100 of modern elevation these changes in the isotopic signature could account for the entire 3 4 18 o depletion in late miocene carbonate nodules and suggest an andean paleoelevation of 3000 m 75 of modern elevations before 10 ma

andean scale highlands in the late cretaceous cordillera of the north american western margin from the late jurassic through the cretaceous collision between the north american and farallon plates drove extensive thin skinned thrusting and crustal shortening that resulted in substantial relief in the north american cordillera the elevation history of this region is tightly linked to the tectonic climatic and landscape evolution of western north america but is not well constrained here we use an atmospheric general circulation model with integrated oxygen isotope tracers isocam3 to predict how isotope ratios of precipitation would change along the north american cordillera as the mean elevation of orogenic highlands increased from 1200 m to 3975 m with increases in mean elevation highland temperatures fall monsoonal circulation along the eastern front of the cordillera is enhanced and wet season generally spring and summer precipitation increases simulated oxygen isotopic ratios in that precipitation are compared to those obtained from geologic materials e g fossil bivalves authigenic minerals quantification of match between model and data derived 18o values suggests that during the late cretaceous the best approximation of regional paleoelevation in western north america is a large orogen on the scale of the modern andes mountains with a mean elevation approaching 4000 m and a north south extent of at least 15 of latitude

rapid late miocene rise of the bolivian altiplano evidence for removal of mantle lithosphere abstract the oxygen isotopic compositions of carbonates deposited in the northern altiplano demonstrate a rapid change in late miocene time which we attribute to an increase in elevation rainfall samples over an elevation transect adjacent to the altiplano of northern bolivia display a systematic decrease in mean annual 18 o values and define a local 18 o vs altitude gradient r gonfiantini m a roche j c olivry j c fontes g m zuppi the altitude effect on the isotopic composition of tropical rains chem geol 181 2001 147 167 which we apply to paleo meteoric water values determined from carbonates age constraints from magnetostragraphy and paleoelevation estimates suggest surface uplift of 2 5 to 3 5 km occurred between 10 3 ma and 6 8 0 4 ma when the altiplano rose to its current elevation only the removal of dense eclogitic lower crust and mantle lithosphere can generate a change of this magnitude and rapidity this change coincides with an 30 decrease in the rate of convergence between the south america and nazca plates and the propagation of deformation into the eastern subandean zone which we infer to have resulted from the increase in the force per unit length applied by the elevated andean plateau to the surrounding lowlands

amazon plant diversity and climate through the cenozoic abstract the modern amazon lowlands date from the mid cenozoic when the andean orogeny defined an eastward or northward draining basin of immense size as the andean orogeny continued throughout the neogene and quaternary periods this system approached a steady state with andean flanks eroding to fill subsiding basins along the andean foreland followed by secondary erosion of sediments and transport in rivers across 3000 km to the atlantic ocean pollen data suggest that tropical forests were established on these lowlands at least by the end of the miocene with many modern amazon genera already present such antiquity is consistent with hypotheses that explain high diversity of modern amazon forests as the result of prolonged existence and minimal disturbance or extinction these museum models for amazon diversity came to be challenged by the paradigm of ice age aridity with its claim that the forests of the amazon lowlands were fragmented with each glacial advance into more or less tiny isolates called refugia separated by grass dominated communities like savanna for the latest pleistocene the arid amazon with forest refugia model can be tested by pollen analysis of lake sediments interpretation of amazon pollen data requires recognition both of the vast diversity of pollen types and an understanding of the dispersal of zoophilous pollen in the amazon amazon pollen analysis has been codified into a pollen atlas and this work used to review the available pollen data within the huge expanse of the amazon basin only three lacustrine records long enough and continuous enough to test this model have been published those from lake pata the carajas plateau and the amazon fan the review suggests community stability from all three data sets with no evidence for forest fragmentation in the amazon lowlands the principal response of amazon forest communities to climatic change is in the relative abundance of the more sensitive taxa particularly in response to interglacial warming a summary of geomorphological phenomena finds no evidence for glacial age aridity other than marginal reductions in precipitation within forest cover the amazon historical record is incomplete in time as well as in space there being essentially no paleobotanical data for much of the cenozoic particularly for the early pleistocene the data so far available however suggest stability and continuity of the forest cover over the vast amazon lowlands throughout the cenozoic as the circumstance in which the high amazon plant diversity evolved

late miocene climate variability and surface elevation in the central andes abstract temporal and spatial variations in topography and oxygen stable isotope ratios in precipitation in the central andes have stimulated widespread discussion about the competing roles of mantle and crustal processes and their feedbacks with global scale climatic change in uplifting and shaping the central andes in general one of the major obstacles in assessing the relative contributions of long term 10 5 10 6 a tectonic processes and precipitation as a proxy for climate to the uplift history of the andean orogen is the lack of integrated data sets that record late miocene patterns of uplift and climate radiogenic 87 sr 86 sr sedimentologic and stable isotope 18 o data from subandean foreland deposits of the chaco basin bolivia show a rapid 18 o and 87 sr 86 sr values at 8 5 ma that we interpret to reflect a change in precipitation patterns along the eastern cordillera and the subandean fold thrust belt in agreement with 13 c studies on paleosol carbonates we attribute this change to a southward deflection of the south american low level jet llj that currently exerts the dominant control over the seasonality and amount of precipitation along the eastern flanks of the andes deflection of the llj occurred most likely as the combined effects of readjustment of relief and topography within the eastern cordillera at 20 22 s and possibly associated surface uplift of the altiplano contemporaneous rapid positive shifts in 18 o and 87 sr 86 sr of pedogenic carbonate in fluvial foreland deposits are consistent with a transition to more seasonal precipitation conditions and critical threshold elevations being attained that affected south american atmospheric circulation patterns a four fold increase in sedimentation rates in the foreland together with a shift to strongly radiogenic 87 sr 86 sr ratios in paleo river water and sediment load as well as river incision into the well preserved san juan del oro paleo surface directly reflects a rapid change in moisture distribution along the eastern flank of the central andes at 8 5 ma and associated rearrangement of the drainage systems collectively the data presented here strongly suggest that between 12 and 8 ma the amount oxygen isotopic composition spatial distribution and seasonality of precipitation along the eastern flank of the bolivian andes changed dramatically which in turn require changes in trans andean moisture flux and isotopic composition of precipitation on the uplifting plateau region

direction and timing of uplift propagation in the peruvian andes deduced from molecular phylogenetics of highland biotaxa abstract physical paleoaltimetric methods are increasingly used to estimate the amount and timing of surface uplift in orogens because the rise of mountains creates new ecosystems and triggers evolutionary changes biological data may also be used to assess the development and timing of regional surface uplift here we apply this idea to the peruvian andes through a molecular phylogeographic and phylochronologic analysis of globodera pallida a potato parasite nematode that requires cool temperatures and thus thrives above 2 0 2 5 km in these tropical highlands the peruvian populations of this species exhibit a clear evolutionary pattern with deeper more ancient lineages occurring in andean southern peru and shallower younger lineages occurring progressively northwards genetically diverging g pallida populations thus progressively colonized highland areas as these were expanding northwards demonstrating that altitude in the peruvian andes was acquired longitudinally from south to north i e in the direction of decreasing orogenic volume this phylogeographic structure is recognized in other independent highland biotaxa and point to the central andean orocline cao as the region where high altitudes first emerged moreover molecular clocks relative to andean taxa including the potato tomato group consistently estimate that altitudes high enough to induce biotic radiation were first acquired in the early miocene after calibration by geological and biological tie points and intervals the phylogeny of g pallida is used as a molecular clock which estimates that the 2 0 2 5 km threshold elevation range was reached in the early miocene in southernmost peru in the middle and late miocene in the abancay segment nw southern peru and from the latest miocene in central and northern peru although uncertainties attached to phylochronologic ages are significantly larger than those derived from geochronological methods these results are fairly consistent with coeval geological phenomena along the peruvian andes they strongly suggest that orogenic volume initially developed in the cao during most of the miocene until a breakthrough in the latest miocene allowed the northward propagation of crustal thickening into central and northern peru possibly by ductile crustal flow from the cao such a combined phylogeographic and phylochronologic approach to regional uplift opens perspectives to estimate the direction s and timing of acquisition of altitude over other cenozoic orogens

response to comment on rapid uplift of the altiplano revealed through 13 c 18 o bonds in paleosol carbonates clumped isotope thermometry measurements of carbonate samples deposited in the bolivian altiplano as early as 28 5 million years ago and buried up to 5000 meters deep exhibit no relationship between burial depth and apparent temperature and largely yield temperatures within error of plausible earth surface conditions these results counter the predictions of sempere et al and support our previous conclusions regarding the uplift of the altiplano

strain accumulation controls failure of a plate boundary zone linking deformation of the central andes and lithosphere mechanics 1 we make use of observations on orogenic strain accumulation and deformation partitioning in the central andes to explore the backarc strength evolution at the lithospheric scale in plan view the altiplano puna plateaux experienced rapid initial increase of surface area undergoing active deformation during the cenozoic beyond the maximum lateral extent reached around 10 15 ma 40 50 of entire proto andes undergoing deformation at 10 20 total strain rapid localization initiated at the eastern flank of the altiplano inter and subandean thrust belt but not at the puna latitude localization was associated with a significant increase in bulk shortening rate average fault slip rates equally increased by an order of magnitude following a protracted period of stable average rates estimates of strength evolution based on force balance calculations and critical wedge analysis suggest significant backarc weakening driving this change after the middle miocene strain accumulation led to localization and weakening with development of a detachment propagating through crust and upper mantle we find that lithosphere scale failure resulting from strain weakening beyond a critical strain threshold c 20 and fault coalescence with formation of a weak detachment in shales effective coefficient of friction 0 1 plays a key role in the evolution of the andes strain related lithosphere weakening appears to dominate over the impact of external forcing mechanisms such as variations of plate convergence mantle assisted processes or erosion comparison of these orogen scale observations with experimental rock rheology indicates substantial similarity of deformation behavior with similar weakening thresholds across a wide range of scales

andean uplift ocean cooling and atacama hyperaridity a climate modeling perspective abstract located along the west coast of subtropical south america the atacama desert features an extremely dry climate in sharp contrast with relatively wet conditions over the central andes and farther east the atacama s hyperaridity has been attributed to its subtropical location the cold waters over the adjacent southeast pacific ocean and the presence of the andes cordillera although geological evidence reveals less dry conditions in the remote past the timing of the arid to hyperarid transition is a matter of controversy several studies suggest that such transition occurred between 19 and 13 ma fostered by the concurrent uplift of the andes during the lower middle miocene other studies however suggest a much earlier 25 ma or later 2 1 ma transition associated with global or regional ocean cooling here we use plasim a simple global climate model to study the effect of the andean surface uplift and sea surface temperature changes upon atacama aridity in one set of experiments the continental topography was scaled by a factor ranging from 0 9 to 0 1 decreasing the height of the andes did not increase precipitation over the atacama region but rather decrease the precipitation over the central andes and the interior of the continent these results consistent with previous modeling studies suggest that the andean uplift was not an important ingredient in the onset of atacama hyperaridity even if both events overlapped in time a globally uniform sea surface warming does not result in a significant increase of precipitation over the atacama in contrast a regional warming over the subtropical southeast pacific very effectively increase precipitation along the west coast of south america by decreasing the subsidence and the dry advection at low levels it suggested that a reinforcement of the humboldt current since the late miocene and particularly during the pliocene pleistocene transition was crucial in the drying of the atacama desert that culminated with the present day hyperarid conditions

quantifying the role of paleoclimate and andean plateau uplift on river incision 1 river incision over geologic timescales can be a valuable indicator of regional surface uplift however extracting the timing of surface uplift relative to the onset of incision is complicated by changes in precipitation commensurate with topographic development evidence of large scale river incision on the flanks of the andean plateau has been cited in support of a rapid and recent surface uplift event recent climate modeling studies demonstrate large magnitudes of regional climate change associated with surface uplift of the andes which may have influenced river incision processes here we present an analysis of mid miocene 16 ma to present river incision of the southwest peruvian ocona river a monte carlo approach with 1 6 105 different simulations is used to explore the range of surface uplift and paleoclimate histories that are compatible with the modern river profile and geological constraints on the incision timing and magnitude a range of channel properties including the erodibility coefficient and erosion threshold are considered results indicate that deep canyon incision on the plateau flanks may not be as diagnostic of rapid surface uplift as previously thought more specifically the evolution of the ocona river is consistent with local plateau elevations of 1 3 km at 16 ma and either a steady or punctuated uplift of 1 5 3 5 km since then the range of acceptable uplift histories is sensitive to the long term magnitude and temporal evolution of precipitation similar paleoprecipitation changes are expected to have modified river profile evolution elsewhere in the andes

mean annual temperature estimation based on leaf morphology a test from tropical south america abstract are models that predict mean annual temperature mat from leaf morphology applicable globally fifteen models that predict mat from leaf morphology were tested on thirty floral samples from tropical south america to determine the degree to which models based on published data that are primarily from other regions are applicable to floras from tropical south america the models included are based on regional data from north america south america and asia of the fifteen models tested five are simple linear regressions six are multiple linear regressions two are canonical correspondence analyses and two are correspondence analyses followed by nearest neighbor analyses for the seven modern floras with mat 21 c every model overestimates mat for the 23 modern floras with mat 21 c all models produce variable results without a systematic error the range of average model errors is 2 7 7 3 c while the absolute extremes of error are 0 and 15 1 c average 95 predictive confidence intervals range from 1 6 to 6 9 c predicted mat falls within the published standard error of the model for 0 67 of the south american test floras evaluating the seven sites with mat 21 c separately from the 23 sites with mat 21 c shows that no equation accurately estimates mat of the majority of low temperature sites but that four equations accurately estimate 50 of high temperature sites the results suggest that at least for sites of unknown or high elevation mean annual temperature of fossil floras from tropical south america may be better predicted from models based on the leaf morphology of tropical south american floras

paleoelevation reconstruction using pedogenic carbonates paleoelevation reconstruction using stable isotopes although a relatively new science is making a significant contribution to our understanding of the recent growth of the world s major orogens in this review we examine the use of both light stable isotopes of oxygen and the new clumped isotope 47 carbonate thermometer in carbonates from soils globally the oxygen isotopic composition 18 o of rainfall decreases on average by about 2 8 km of elevation gain this effect of elevation will in turn be archived in the 18 o value of soil carbonates and paleoelevation can be reconstructed provided 1 temperature of formation can be estimated 2 the effects of evaporation are small 3 the effects of climate change can be accounted for and 4 the isotopic composition of the carbonate is not diagenetically altered we review data from modern soils to evaluate some of these issues and find that evaporation commonly elevates 18 o values of carbonates in deserts an effect that would lead to underestimates of paleoelevation some assessment of paleoaridity using qualitative indicators or carbon isotopes from soil carbonate is therefore useful in evaluating the oxygen isotope based estimates of paleoelevation sampling from deep 50 cm in paleosols helps reduce the uncertainties arising from seasonal temperature fluctuations and from evaporation the new clumped isotope 47 carbonate thermometer expressed as 47 offers an independent and potentially very powerful approach to paleoelevation reconstruction in contrast to the use of 18 o values nothing need be known about the isotopic composition of water from which carbonate grew in order to estimate of temperature of carbonate formation from 47 values using assumed temperature lapse rates with elevation paleoelevations can thereby be reconstructed case studies from the andes and tibet show how these methods can be used alone or in combination to estimate paleoelevation in both cases the potential for diagenetic alteration of primary carbonate values first has to be assessed clear examples of both preservation and alteration of primary isotopic values are available from deposits of varying ages and burial histories 47 values constitute a relatively straightforward test since any temperature in excess of reasonable surface temperatures points to diagenetic alteration for 18 o values preservation of isotopic heterogeneity between different carbonate phases offers a check on diagenesis results of these case studies show that one area of south central tibet attained elevations comparable to today by the late oligocene whereas 2 7 0 4 km of uplift occurred in the bolivian altiplano during the late miocene

rise of the andes the surface uplift of mountain belts is generally assumed to reflect progressive shortening and crustal thickening leading to their gradual rise recent studies of the andes indicate that their elevation remained relatively stable for long periods tens of millions of years separated by rapid 1 to 4 million years changes of 1 5 kilometers or more periodic punctuated surface uplift of mountain belts probably reflects the rapid removal of unstable dense lower lithosphere after long term thickening of the crust and lithospheric mantle

role of the atmospheric mean state on the initiation of the madden julian oscillation in a tropical channel model tropical channel models defined as models that are global in the zonal direction but bounded in the meridional direction are particularly useful for simulating the madden julian oscillation mjo and understanding its physical and dynamical basis influences from the extratropics through the lateral boundaries have been found to be essential to the reproduction of the initiation of certain mjo events this led to a hypothesis that multi year simulations using a tropical channel model would reproduce reasonable mjo statistics under the influence of prescribed lateral boundary conditions derived from global reanalyses interestingly the mjo statistics in such a multi year simulation by a high resolution tropical channel model are not better than those from global climate models the error in the atmospheric mean state is found to be a possible reason for the poor mjo statistics in the simulation nevertheless even with a large error in the mean state the multi year simulation captures two mjo events previously found to be initiated by extratropical influences however the model does not reproduce a third event whose initiation is not directly influenced by the extratropics this implies that in the absence of dynamical interactions between the mjo and the lateral boundary conditions the error in the mean state could be sufficient to prevent the mjo initiation to explore this third mjo event further a series of sensitivity tests are conducted these tests show that the simulation of this event is neither critically influenced by the cumulus parameterization employed nor the initial conditions when the model is integrated 2 weeks prior to the mjo initiation the model captures this event when the mjo signal is already present in the initial conditions the use of high resolution sea surface temperature does not improve the simulation of the third mjo event a higher resolution nested domain covering the indo pacific warm pool region and including a cloud system resolving domain over the indonesian maritime continent has little effect on the mjo initiation over the indian ocean in 2 weeks the error in the simulation is comparable to the climate error the role of the simulated mjo on the mean state is also explored implications and limitations of these results are discussed

origin of the high plateau in the central andes bolivia south america the bolivian altiplano in the central andes of south america is part of the second largest high plateau on earth it is an elongate region of subdued relief 1 2 105 km2 and 4 km above sea level bounded by the eastern cordillera and volcanic arc western cordillera here the crust is up to 75 km thick we describe the cenozoic geological evolution of this region using a revised chronostratigraphy and an analysis of the crustal and lithospheric structure crustal shortening and magmatic addition and locally sedimentation are the main mechanisms of cenozoic crustal thickening leading to nearly 4 km of surface uplift since the paleocene addition of mafic melts appears to be a first order mechanism of cenozoic crustal growth contributing 40 of the crustal thickening beneath the volcanic arc removal of the basal part of the lithosphere may have caused two episodes of widespread arc and behind arc mafic volcanism at 23 ma and 0 5 ma contributing to the surface uplift the altiplano originated as a sedimentary basin several hundred kilometers wide between the proto western cordillera and a narrow zone of uplift proto eastern cordillera farther east the latter zone formed by inversion of the center of a wide lacustrine or marine cretaceous paleocene basin close to sea level at 45 ma a thickness of 2 4 km of paleogene continental elastics accumulated in the proto altiplano basin subsequently in the oligocene we estimate that this region and the western margin of the eastern cordillera were technically shortened 22 65 km resulting in 9 km of average crustal thickening the altiplano basin was rejuvenated at 25 ma and subsequently flooded with up to 8 km thickness of detritus eroded from the uplifting eastern and western cordilleras between 25 and 5 ma folding and thrusting in the western margin of the eastern cordillera migrated westward into the center of the altiplano basin essentially terminating deposition except in local subbasins and accommodating 13 30 km of shortening and an estimated 7 km of average crustal thickening subsequently there has been strike slip deformation and limited local thrusting 5 km of shortening geomorphological and geochronological evidence for 1 5 2 km of surface uplift of this region since the late miocene suggests 14 km of lower crustal thickening beneath an essentially rigid lid and can be explained by 100 150 km of underthrusting of the brazilian shield and adjacent regions beneath the eastern margin of the central andes the present subdued relief in the altiplano may be a result of ductile flow in the lower crust and sedimentation and erosion in an internal drainage basin

how systematic is organized tropical convection within the mjo 1 recent theories of the dynamics of the madden julian oscillation mjo have been building on its multiscale structure while it is observed that much of the convection within the mjo envelope is related to higher frequency equatorial waves it is not known to what extent this organization is systematic from one mjo event to another for instance it is of interest to know whether mjo favors waves of particular types and propagation direction and how this variability changes seasonally this work presents a wavenumber frequency spectral analysis of the mjo convective envelope which indicates that there is no strong preferred scale of high frequency organization that is ubiquitous to the mjo this null finding supports the use of convective parametrizations in modeling the mjo since while moist convection is likely critical to its initiation and maintenance the particular details of that organization may not be critical for its prediction and simulation

central andean crustal structure from receiver function analysis abstract the central andean plateau 15 27 s is a high plateau in excess of 3 km elevation associated with thickened crust along the western edge of the south america plate in the convergent margin between the subducting nazca plate and the brazilian craton we have calculated receiver functions using seismic data from a recent portable deployment of broadband seismometers in the bolivian orocline 12 21 s region and combined them with waveforms from 38 other stations in the region to investigate crustal thickness and crust and mantle structures results from the receiver functions provide a more detailed map of crustal thickness than previously existed and highlight mid crustal features that match well with prior studies the active volcanic arc and altiplano have thick crust with moho depths increasing from the central altiplano 65 km to the northern altiplano 75 km the eastern cordillera shows large along strike variations in crustal thickness along a densely sampled sw ne profile through the bolivian orocline there is a small region of thin crust beneath the high peaks of the cordillera real where the average elevations are near 4 km and the moho depth varies from 55 to 60 km implying the crust is undercompensated by 5 km in comparison a broader region of high elevations in the eastern cordillera to the southeast near 20 s has a deeper moho at 65 70 km and appears close to isostatic equilibrium at the moho assuming the modern day pattern of high precipitation on the flanks of the andean plateau has existed since the late miocene we suggest that climate induced exhumation can explain some of the variations in present day crustal structure across the bolivian orocline we also suggest that south of the orocline at 20 s the thicker and isostatically compensated crust is due to the absence of erosional exhumation and the occurrence of lithospheric delamination

testing the analytical protocols and calibration of volcanic glass for the reconstruction of hydrogen isotopes in paleoprecipitation in this study we investigate the foundations of the hydrated volcanic glass paleoelevation paleoenvironment proxy by testing 1 the sensitivity of volcanic glass d values to laboratory procedures 2 the reliability of young glass reconstructions of observed meteoric water values and 3 the paleoenvironmental reconstructions based on volcanic glass in comparison to those of other proxies volcanic glass d values are insensitive to variations in laboratory pretreatments displaying no signifi cant shift in d values with variations in duration of drying rinsing the temperature at which glass is dried or with the grain size that is analyzed however clay adhering to the glass particles may skew d results by 10 and hf acid pretreatment can cause signifi cant isotopic shifts parent water d values calculated from young 0 3 ma glass d values are in close accord with modern surface water d values across 3000 m of elevation in the central andes combined glass d values pedogenic carbonate 18 o values and clumped isotope paleothermometry from the 16 3 ma los cristales tuff provide a key test of resistance to resetting of d values in ancient glass hydration layers these proxies indicate hydrated volcanic glass preserves its stable isotopic information over geologic time and that the climatic patterns of the high and dry puna plateau were already in place by 16 3 ma

influence of the andes mountains on south american moisture transport convection and precipitation mountain ranges are known to have a first order control on mid latitude climate but previous studies have shown that the andes have little effect on the large scale circulation over south america we use a limited domain general circulation model regcm3 to evaluate the effect of the andes on regional scale atmospheric dynamics and precipitation we present experiments in which andean heights are specified at 250 m and 25 50 75 and 100 of their modern values our experiments indicate that the andes have a significant influence on moisture transport between the amazon basin and the central andes deep convective processes and precipitation over much of south america through mechanical forcing of the south american low level jet llj and topographic blocking of westerly flow from the pacific ocean when the andes are absent the llj is absent and moisture transport over the central andes is mainly northeastward as a result deep convection is suppressed and precipitation is low along the andes above 50 of the modern elevation a southward flowing llj develops along the eastern andean flanks and transports moisture from the tropics to the subtropics moisture drawn from the amazon basin provides the latent energy required to drive convection and precipitation along the andean front large northerly moisture flux and reduced low level convergence over the amazon basin leads to a reduction in precipitation over much of the basin our model results are largely consistent with proxy evidence of andean climate change and have implications for the timing and rate of andean surface uplift

uplift of the central andes of nw argentina associated with upper crustal shortening revealed by multiproxy isotopic analyses this study contributes to the uplift history of the andes which has received increasing attention in recent years because of its implications for geodynamic models and climate feedbacks shortening resulting in crustal thickening and removal of gravitationally unstable mantle lithosphere has been proposed to control deformation and uplift of cordillera type orogenic systems such as the puna plateau of the central andes and its eastern margin the eastern cordillera we present new clumped isotope 47 18o and 2 data from carbonate nodules marlstone spring deposits and volcanic ashes from the puna plateau and eastern cordillera of nw argentina when combined with other geological evidence our data indicate that the puna plateau was near its present elevation since at least 10 ma whereas the eastern cordillera rose 1 5 km between 14 and 7 ma this history of uplift correlates with active shortening in the eastern cordillera and with incorporation of a regional foreland into the propagating orogenic wedge our study suggests that the elevation of the puna plateau changed little during the miocene pliocene whereas the margin experienced significant uplift associated with active deformation and crustal thickening

rapid regional surface uplift of the northern altiplano plateau revealed by multiproxy paleoclimate reconstruction the central altiplano is inferred to have experienced 2 5 1km surface uplift between 10 and 6 ma while the southern altiplano experienced a similar magnitude of surface uplift that began earlier between 16 and 9 ma to properly constrain the along strike timing of the altiplano plateau surface uplift it is necessary to know how and when the northernmost part of the altiplano plateau evolved we reconstruct the paleoclimate and infer the corresponding paleoelevation from the miocene pliocene deposits of the descanso yauri basin 14 15 s in the northernmost part of the altiplano plateau using 4 different proxies including carbonate clumped isotope composition i e 47 values carbonate 18 o c leaf wax d wax and pollen assemblages from paleosol lacustrine and palustrine carbonates and organic rich sediments the isotopic signatures reflect past climate conditions of mean annual air temperature 47 and meteoric water isotope values 18 o c d wax our results show that the northernmost plateau remained at low elevation 0 9 0 8 to 2 1 0 9km until late miocene time 9 ma characterized by 15 c warmer than modern temperature mean annual air temperature of 23 4 c 2 low elevation vegetation and precipitation signature with reconstructed 18 o mw vsmow of 8 3 2 0 2 from carbonate 18 o c and 8 6 1 8 2 from leaf wax d wax modern elevations of 4 km were not reached until 5 4 1 0ma as indicated by a negative shift in d wax vsmow from 143 4 12 8 2 to 209 2 21 1 2 between 9 1 0 7 and 5 4 1 0ma the timing of surface uplift of the northernmost altiplano is consistent with the evidence for late miocene surface uplift of the central altiplano 16 19 s between 10 and 6 ma and indicates that regional scale uplift in the northern central plateau significantly postdates the onset of surface uplift in the southern altiplano 19 22 s between 16 and 9 ma these results are consistent with piecemeal removal of the lower dense lithosphere combined with possible lower middle crustal flow from south to north in the plateau acting as the main mechanisms for the formation of the altiplano plateau

sedimentology based reconstructions of paleoclimate changes in the central andes in response to the uplift of the andes arica region between 19 and 21 s latitude northern chile we focus on the sedimentological record of the middle miocene to modern deposits in the andes of northern chile between 19 and 21 s these sediments deposited at the western escarpment of the central depression indicate successively more moisture on the western margin of the altiplano and the western cordillera where the sources are at the pacific coast 20 ma old exposure ages and salic gypsisols reflect an existing and ongoing hyperarid climate we interpret the increased divergence of climates between the coast and the altiplano as consequence of the andean rise to elevations higher than approximately 2 500 m a s l when the topography of the altiplano was sufficiently high and areally extensive to attract atlantic moisture accordingly the inferred general increase in run off was closely coupled with the uplift of the andes if the steady rise model applies in case that the rapid rise model for andean uplift is correct the inferred changes in sediment transport would have occurred independently of uplift requiring an alternative yet unknown driver

widening of the andes an interplay between subduction dynamics and crustal wedge tectonics shortening of the continental lithosphere is generally accommodated by the growth of crustal wedges building above megathrusts in the mantle lithosphere we show that the locus of shortening in the western margin of south america has largely been controlled by the geometry of the slab numerical models confirm that horizontal subduction favors compression far from the trench above the asthenospheric wedge and steeply dipping segment of the subducting slab as a result a second crustal wedge grows in the hinterland of the continent and widens the andes in the bolivian orocline this wedge corresponds to the eastern cordillera whose growth was triggered by a major episode of horizontal subduction when the slab returned to a steeper dip angle shortening and uplift pursued facilitated by the structural and thermo chemical alteration of the continental lithosphere we review the successive episodes of horizontal subduction that have occurred beneath south america at different latitudes and show that they explain the diachronic widening of the andes we infer that the present day segmented physiography of the andes results from the latitudinally variable transient interplay between slab dynamics and upper plate tectonics over the cenozoic we emphasize that slab flattening or absence thereof is a major driving mechanism that sets the width of the andes at any latitude

impacts of cenozoic global cooling surface uplift and an inland seaway on south american paleoclimate and precipitation δ18o stable isotope records of precipitation 18 o 18 o prec have been used as paleoclimate and paleoelevation archives of orogens however interpretation of these records is limited by knowledge of how 18 o prec responds to changes in global and regional climate during mountain building events in this study the influence of atmospheric co 2 levels the extent of the antarctic ice sheet changes in andean surface elevation and the presence of the south american inland seaway on climate and 18 o prec in south america are quantified using the genesis v3 atmospheric general circulation model with isotope tracking capabilities results are presented in the context of cenozoic south american climate and 18 o prec changes more specifically we find 1 precipitation rates in the andes are sensitive to andean surface elevation the seaway and to a lesser extent co 2 levels increasing andean elevations and the presence of a seaway both cause large increases in precipitation but in different parts of the andes the growth of the antarctic ice sheet is found to have a small influence on south american precipitation 2 the stable isotopic composition of precipitation is sensitive to all of the parameters investigated an increase in 18 o prec of up to 8 is found in simulations with higher atmospheric co 2 in agreement with previous studies 18 o prec decreases with increasing andean elevation by an amount greater than that predicted by the modern adiabatic lapse rate furthermore the presence of an inland seaway causes a decrease in 18 o prec of 1 8 in the northern and central andes the amount of depletion is dependent on the isotopic composition of the seaway simulations without the antarctic ice sheet result in 18 o prec that is 0 3 lower than the modern finally time specific simulations for the miocene and eocene show that 18 o prec has decreased during the cenozoic and that local geographical gradients of 18 o prec have increased particularly in regions of high modern elevation we demonstrate that in addition to andean uplift and associated climate change co 2 levels and an inland seaway are likely to have influenced 18 o carb records from south america consideration of these global and paleogeographic changes is necessary when interpreting paleoclimate or paleoelevation from stable isotope records of 18 o prec

clumped isotope evidence for diachronous surface cooling of the altiplano and pulsed surface uplift of the central andes spatially extensive paleoelevation records of the altiplano plateau are critical to determining the geodynamic mechanisms that formed and support high elevations over a broad area prior stable isotope data reveal a climate history for the northern bolivian altiplano that has been interpreted to show rapid surface uplift of 2 5 1 0 km between 10 and 6 ma this study applies clumped isotope paleothermometry to paleosol carbonates formed at both a low elevation site and temporally overlapping high elevation sites in the southern altiplano eastern cordillera during the middle to late miocene surface paleotemperature decreased by 14 c in the southern altiplano eastern cordillera relative to stable low elevation paleotemperatures implying surface elevation increase of 1 9 0 7 km between 16 and 13 ma and an additional 0 7 0 6 km between 13 and 9 ma both the large magnitude of surface temperature decrease and earlier onset 7 4 myr in the south as compared to the north suggest rapid elevation increase by piecemeal removal of lower lithosphere beneath the plateau and possible northward lower crustal flow

early cenozoic evolution of topography climate and stable isotopes in precipitation in the north american cordillera paleoelevation reconstructions of the north american cordillera in ferred from the oxygen delta 18o and hydrogen delta d isotope ratios of terrestrial paleoclimate proxy materials soils ashes lake sediments suggest rapid north to south migration of topography in the early cenozoic pre 49 ma to 28 ma the validation of this reconstruction relies on an accurate understanding of the delta 18op and the associated regional climate change in response to the uplift of the western north america here we study this response using a global climate model gcm with explicit delta 18op diagnostics echam5 wiso focusing on the isotopic effects of different types of precipitation vapor mixing recycling and moisture source and compare the response against estimates made using a rayleigh distillation models of moist adiabatic condensation rdm four experiments are performed with eocene topography inferred from terrestrial stable isotope paleoaltimetry records to investigate how southward propagation of topography affects regional climate temperature precipitation and circulation pattern and dela 18op over north america our experiments predict delta 18op patterns that are broadly consistent with maps of temporally binned proxy delta 18o and generally support an early cenozoic north to south propagation of high topogra phy in the north american cordillera they do not support the commonly made assumption that isotopic fractionation occurs primarily through rainout following rayleigh distillation nor the application of modern empirical delta 18op lapse rates to past environments in our gcm simulations precipitation processes and climate changes that are not captured by rdms substantially affect delta 18op these processes include shifts in local precipitation type between convective and large scale rain and between rain and snow intensification of low level vapor recycling particularly on leeward slopes develop ment of air mass mixing and changes in wind direction and moisture source each of these processes can have significant 2 influences on delta 18op that are comparable in magnitude to surface uplift of hundreds or even thousands of meters in many regions these processes fortuitously compensate each other explaining the apparent agreement between echam5 wiso and proxy delta 18o and more broadly between rdm estimates and observed delta 18o elevation relationships in some regions compensation is incomplete and as a result echam5 wiso delta 18op does not agree with estimates from the rdm in these regions including the interior of the northern cordillera and the eastern flank of the southern cordillera moderate adjustments of paleoelevations may be in order

end member models for andean plateau uplift abstract diverse techniques have been applied over the past decade to quantify the uplift history of the central andean plateau ap in this study opposing models for surface uplift are evaluated including a rapid rise of 2 5 km 10 6 ma and a slow and steady rise since 40 ma these end member models are evaluated by synthesizing observations of the ap lithosphere and the history of deformation sedimentation exhumation magmatism uplift and fluvial incision structural and geophysical studies estimate variable shortening magnitudes 530 150 km involving cover to basement rocks an isostatically compensated thick crust 80 65 km high heat flow and zones of variable velocity and attenuation in the crust and mantle these observations have invoked interpretations such as a hot weak lithosphere partial melt crustal flow and perhaps current localized delamination but do not provide strong support for massive delamination required by the rapid uplift model deformation and associated exhumation began 60 40 ma and generally migrated eastward with consistent long term average shortening rates 12 8 mm yr in bolivia favoring the slow uplift model volcanic and helium isotope evidence show an ap wide zone of shallow mantle melting and thin lithosphere that has existed since 25 ma which is inconsistent with the rapid rise model that suggests lithospheric thinning occurred 10 6 ma paleoaltimetry data suggest a rapid 2 5 km elevation gain 10 to 6 ma but are equally consistent within error with a linear rise since 25 ma widespread fluvial incision 2 5 1 km occurred along the western flank since 11 8 ma and may be associated with surface uplift as proposed by the rapid rise model however the paleoaltimetry and incision data can also be explained by regional climate change associated with plateau uplift implications of these results for reconstructions of ap evolution are that 1 substantial deformation of a weak lithosphere is essential 2 ap growth has taken significantly longer 40 myr and was more uniform along strike 1500 km than previously appreciated and 3 the slow and steady uplift model is most consistent with available constraints we conclude that the rapid uplift model may be an overestimate and that a more protracted cenozoic uplift history is tenable

middle miocene climatic change in the atacama desert northern chile evidence from supergene mineralization at la escondida geochronology and paleotopographic reconstruction of the porphyry copper deposit at la escondida chile are used to calculate long term erosion rates and to deduce the timing of tertiary climatic change for a portion of the atacama desert region hypogene hydrothermal alteration and protore mineralization at la escondida took place between 33 7 1 4 and 31 0 1 4 ma based on k ar dating of hydrothermal biotite and sericite supergene weathering and copper sulfide en richment processes were active from 18 0 0 7 to 14 7 0 6 ma based on k ar dating of supergene alunite distinguished from hypogene alunite by grain size color and sulfur isotopic composition reworked lenses of volcanic ash in the vicinity of la escondida provide useful time stratigraphic markers at 8 7 0 4 6 5 0 2 and 4 2 0 2 ma within present soil profiles long term average rates of erosion are determined by these age dates and quantitative calculation of eroded leached capping thickness at la escondida using mass balance analysis of geochemical profiles coupled with an estimate of unmineralized lithocap thickness based on alteration petrology and fluid inclusion geobarometry at similar deposits the observed trend of decreasing long term average erosion rates with time is consistent with arid to semiarid conditions in the early miocene changing to hyperarid conditions during the middle miocene this climatic desiccation caused termination of significant supergene copper suffide enrichment at la escondida and elsewhere in the atacama region and preservation of surficial features including the ash horizons and the leached capping middle miocene climatic desiccation in northern chile and southern peru was probably related to a pronounced decrease in temperature of coastal waters supplied by an ancestral humboldt current and an increase in upwelling intensity as the antarctic ice cap became established at approximately 15 to 13 ma the central andes cordillera which now provides a rain shadow protecting the atacama region from precipitation from the east must have attained at least half its present elevation prior to about 15 ma to have played a similar role in the middle miocene

comment on rapid uplift of the altiplano revealed through 13c 18o bonds in paleosol carbonates based on stable isotope measurements ghosh et al reports 27 january 2006 p 511 concluded that the bolivian altiplano uplifted 3 to 4 kilometers between 10 3 and 6 7 million years ago as a result of gravitational loss of dense lithosphere this result stands at odds with current geological knowledge of the central andes and we propose a test for the reliability of the paleoaltimetry method

a stable isotope record of late cenozoic surface uplift of southern alaska abstract although the timing of an acceleration in late cenozoic exhumation of southern alaska is reasonably well constrained as beginning 5 6 ma the surface uplift history of this region remains poorly understood to assess the extent of surface uplift relative to rapid exhumation we developed a stable isotope record using the hydrogen isotope composition d of paleo meteoric water over the last 7 ma from interior basins of alaska and yukon territory our record which is derived from authigenic clays dclay in silicic tephras documents a 50 60 increase in d values from the late miocene 6 7 ma through the plio pleistocene transition 2 3 ma followed by near constant values over at least the last 2 ma although this enrichment trend is opposite that of a rayleigh distillation model typically associated with surface uplift we suggest that it is consistent with indirect effects of surface uplift on interior alaska including changes in aridity moisture source and seasonality of moisture we conclude that the dclay record documents the creation of a topographic barrier and the associated changes to the climate of interior alaska and yukon territory

stable isotopes of surface water across the longmenshan margin of the eastern tibetan plateau characterization of the stable isotope compositions 18o and d of modern day surface waters traversing mountain ranges and bordering continental plateaus is important for refining climate models and establishing modern isotope elevation gradients along mountain ranges the longmenshan margin of the tibetan plateau is a steep 4 km topographic front situated near the boundaries between westerlies and asian monsoon moisture sources and is previously unexplored with respect to the variation in water isotopic composition with elevation this study reports stable isotope data from 101 water samples collected from streams springs and ponds along the min river minjiang watershed which traverses the longmenshan margin local meteoric water lines d excess values and surrounding precipitation and river water data sets suggest that precipitation across the longmenshan margin is dominated by the east asian summer monsoon the increase in d excess values with increasing catchment elevation breaks down as local moisture recycling becomes important at elevations 3 km a s l along the min river however the 18ow and dw values decrease with increasing catchment elevation which fit second order polynomial curves and are well approximated by a simple rayleigh fractionation processes the temperature corrected oxygen values in authigenic carbonates from the pleistocene zoige basin north of the min river watershed yield elevations equivalent to present by the oxygen isotope elevation relationship of the longmenshan margin

canyon incision chronology based on ignimbrite stratigraphy and cut and fill sediment sequences in sw peru documents intermittent uplift of the western central andes abstract based on an 40ar 39ar and u pb based chronostratigraphy of ignimbrite sheets and the geomorphological features of watersheds river profiles and slope deposits in the ocona cotahuasi maran ocm and colca valleys of southwest peru we reconstruct the valley incision history of the western central andes over the last c 25 myr we further document the pleistocene and holocene evolution of deep valleys on the basis of 14 10be surface exposure ages obtained on debris avalanche deposits and river straths the data suggest that uplift was gradual over the past 25 myr but accelerated after c 9 ma valley incision started around 11 9 ma and accelerated between 5 and 4 ma incision was followed by several pulses of valley cut and fill after 2 3 ma evidence presented suggest that the post 5 ma sequence of accelerated canyon incision probably resulted from a combination of drainage piracy from the cordilleran drainage divide towards the altiplano accentuated flexural tilting of the western cordillera towards the se and increased rainfall on the altiplano after late miocene uplift of the eastern cordillera the valley deepening and slope steepening driven by tectonic uplift gave rise to large occurrences of rockslope failure the collapsed rock masses periodically obstructed the canyons thus causing abrupt changes in local base levels and interfering with the steadiness of fluvial incision as a result channel aggradation has prevailed in the lower gradient u shaped pacific rim canyons whereas re incision through landslide deposits has occurred more rapidly across the steeper v shaped upper valleys existing canyon knickpoints are currently arrested at the boundary between the plutonic bedrock and widespread outcrops of middle miocene ignimbritic caprock where groundwater sapping favouring rock collapse may be the dominant process driving headward erosion

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

large along strike variations in the onset of subandean exhumation implications for central andean orogenic growth abstract plate tectonics drives mountain building in general but the space time pattern and style of deformation is influenced by how climate geodynamics and basement structure modify the orogenic wedge growth of the subandean thrust belt which lies at the boundary between the arid high elevation central andean plateau and its humid low elevation eastern foreland figures prominently into debates of orogenic wedge evolution we integrate new apatite and zircon u th he thermochronometer data with previously published apatite fission track data from samples collected along four subandean structural cross sections in bolivia between 15 and 20 s we interpret cooling ages vs structural depth to indicate the onset of subandean exhumation and signify the forward propagation of deformation we find that subandean growth is diachronous south 11 3 ma vs north 6 2 ma of the bolivian orocline and that subandean exhumation magnitudes vary by more than a factor of two similar north south contrasts are present in foreland deposition hinterland erosion and paleoclimate these observations both corroborate diachronous orogenic growth and illuminate potential propagation mechanisms of particular interest is an abrupt shift to cooler more arid conditions in the altiplano hinterland that is diachronous in southern bolivia 16 13 ma vs northern bolivia 10 7 ma and precedes the timing of subandean propagation in each region others have interpreted the paleoclimate shift to reflect either rapid surface uplift due to lithosphere removal or an abrupt change in climate dynamics once orographic threshold elevations were exceeded these mechanisms are not mutually exclusive and both would drive forward propagation of the orogenic wedge by augmenting the hinterland backstop either through surface uplift or spatially variable erosion in summary we suggest that diachronous subandean exhumation was driven by piecemeal hinterland uplift orography and the outward propagation of deformation

rapid uplift of the altiplano revealed through 13c 18o bonds in paleosol carbonates the elevation of earth s surface is among the most difficult environmental variables to reconstruct from the geological record here we describe an approach to paleoaltimetry based on independent and simultaneous determinations of soil temperatures and the oxygen isotope compositions of soil waters constrained by measurements of abundances of 13 c 18 o bonds in soil carbonates we use this approach to show that the altiplano plateau in the bolivian andes rose at an average rate of 1 03 0 12 millimeters per year between 10 3 and 6 7 million years ago this rate is consistent with the removal of dense lower crust and or lithospheric mantle as the cause of elevation gain

linking orography climate and exhumation across the central andes quantifying interactions between uplift climate deformation and exhumation remains difficult in many cases due to a paucity of data relevant to all processes we synthesize new and existing data to understand the orogen scale orographic changes across the central andes bolivia we use a regional climate model and geo thermochronologic data to identify the correlations between changes in precipitation due to surface uplift and spatiotemporal patterns of deformation and erosional exhumation mean orographic rainfall patterns do not reach near present day gradients and values until the topography grows to 75 modern elevations new fission track data near the orocline apex indicate that rapid exhumation moved eastward beginning in the eastern cordillera ca 50 15 ma the interandean zone ca 18 6 ma and in the subandes ca 7 3 ma throughout bolivia exhumation is consistent with deformation until ca 15 11 ma after which the pattern corresponds better with the increased rainfall toward modern values these linked observations suggest that ca 15 11 ma regional elevations reached threshold values 75 modern necessary to generate near present day enhanced rainfall gradients these gradients have resulted in variable exhumation implied by the structural level of rocks exposed across the thrust belt and confirmed by fission tracks in apatite the main insight is that the climate induced middle miocene recent exhumation varies over scales of a few hundred kilometers across bolivia and implies that high mean rainfall 3 m yr and long time scales 10 m y may be necessary for climate to induce orographically driven exhumation patterns recorded by fission tracks

climate change imprinting on stable isotopic compositions of high elevation meteoric water cloaks past surface elevations of major orogens stable isotope paleoaltimetry has been widely used to estimate cenozoic surface elevation of major orogens the influence of global climate change on stable isotope paleoaltimetry is uncertain with proposals that warming could cause either overestimates or underestimates of past surface elevations in this study we increase atmospheric p co 2 by two and four times in an isotope tracking atmospheric general circulation model to investigate the effect of global warming on oxygen isotopic compositions of precipitation 18 o p over the continents as in other climate models the response in the genesis version 3 model to global warming is an amplification of upper troposphere temperatures through enhanced infrared absorption and a reduction in the surface to upper level temperature gradient due to the temperature dependence of isotopic fractionation vapor 18 o 18 o v follows suit leading to a reduction in the surface to upper troposphere 18 o v gradient in regions of subsidence including the major orogens and deserts downward mixing of 18 o enriched vapor from the troposphere to the near surface further reduces the lapse rate of 18 o v as a consequence of these effects the isotopic composition of precipitation in high elevation regions including the tibetan plateau rocky mountains european alps and andean plateau increases by 3 6 relative to that at low elevations neglect of this climate effect on high elevation 18 o p has likely led to underestimates of the surface elevation of cenozoic orogens