empirical relationship between leaf wax n alkane δd and altitude in the wuyi shennongjia and tianshan mountains china implications for paleoaltimetry article i nfo estimating past elevation not only provides evidence for vertical movements of the earth s lithosphere but also increases our understanding of interactions between tectonics relief and climate in geological history development of biomarker hydrogen isotope based paleoaltimetry techniques that can be applied to a wide range of sample types is therefore of continuing importance here we present leaf wax derived n alkane d dwax values along three soil altitudinal transects at different latitudes in the wuyi shennongjia and tianshan mountains in china to investigate dwax gradients and the apparent fractionation between leaf wax and precipitation ewax p we findthatsoil dwax trackaltitudinal variationsof precipitation d along the three transects that span variable environment conditions and vertical vegetation spectra an empirical dwax altitude relation is therefore established in which the average dwax lapse rate of 2 27 0 38 100 m is suitable for predicting relative paleoelevation change relative uplift the application of this empirical gradient is restricted to phases in the mountain uplift stage whenthe atmospheric circulation had not distinctly changed and to when the climate was notarid anempirical dwax latitude altitudeformulaisalsocalculated dwax 3 483lat 0 0227alt 261 5 which gives the preliminary spatial distribution pattern of dwax in modern china meanvalue of ewax p intheextreme humid wuyimountainsisquite negative 154 compared to the humid shennongjia 129 and the arid but with abundant summer precipitation tianshan mountains 130 which suggests aridity or water availability in the growing season is the primary factor controlling soil sediment ewax p along the tianshan transects values of ewax p are speculated to be constant with altitude while along the wuyi and shennongjia transects ewax p are also constant at the low mid altitudes but become slightly more negative at high altitudes which could be attributed to overestimates of precipitation d or the vegetation shift to grass conifer additionally a reversal of altitude effect in the vertical variation of dwax was found in the alpine zone of the tianshan mountains which might be caused by atmospheric circulation change with altitude this implies that the paleo circulation pattern and its changes should alsobe evaluated whenstable isotope based paleoaltimetry is applied

late glacial stage and holocene tropical ice core records from huascaran peru two ice cores from the col of huascaran in the north central andes of peru contain a paleoclimatic history extending well into the wisconsinan wurm glacial stage and include evidence of the younger dryas cool phase glacial stage conditions at high elevations in the tropics appear to have been as much as 8 to 12 c cooler than today the atmosphere contained about 200 times as much dust and the amazon basin forest cover may have been much less extensive differences in both the oxygen isotope ratio 18o 8 per mil and the deuterium excess 4 5 per mil from the late glacial stage to the holocene are comparable with polar ice core records these data imply that the tropical atlantic was possibly 5 to 6 c cooler during the late glacial stage that the climate was warmest from 8400 to 5200 years before present and that it cooled gradually culminating with the little ice age 200 to 500 years before present a strong warming has dominated the last two centuries

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

a lacustrine gdgt temperature calibration from the scandinavian arctic to antarctic renewed potential for the application of gdgt paleothermometry in lakes quantitative climate reconstructions are fundamental to understand long term trends in natural climate variability and to test climate models used to predict future climate change recent advances

effects of aridity and vegetation on plant wax δd in modern lake sediments we analyzed the deuterium composition of individual plant waxes in lake sediments from 28 watersheds that span a range of precipitation d h vegetation types and climates the apparent isotopic fractionation ea between plant wax n alkanes and precipitation differs with watershed ecosystem type and structure and decreases with increasing regional aridity as measured by enrichment of 2 h and 18 o associated with evaporation of lake waters the most negative ea values represent signatures least affected by aridity these values were 125 5 for tropical evergreen and dry forests 130 for a temperate broadleaf

a miocene to pleistocene climate and elevation record of the sierra nevada california orographic precipitation of pacific sourced moisture creates a rain shadow across the central part of the sierra nevada california that contrasts with the southern part of the range where seasonal monsoonal precipitation sourced to the south obscures this rain shadow effect orographic rainout systematically lowers the hydrogen isotope composition of precipitation dppt and therefore dppt reflects a measure of the magnitude of the rain shadow hydrogen isotope compositions of volcanic glass dglass hydrated at the earth s surface provide a unique opportunity to track the elevation and precipitation history of the sierra nevada and adjacent basin and range province analysis of 67 well dated volcanic glass samples from widespread volcanic ash fall deposits located from the pacific coast to the basin and range province demonstrates that between 0 6 and 12 1 ma the hydrogen isotope compositions of meteoric water displayed a large 40 decrease from the windward to the leeward side of the central sierra nevada consistent with the existence of a rain shadow of modern magnitude over that time evidence for a miocene to recent rain shadow of constant magnitude and systematic changes in the longitudinal climate and precipitation patterns strongly suggest that the modern first order topographic elements of the sierra nevada characterized the landscape over at least the last 12 million years

tropical climates at the last glacial maximum a new synthesis of terrestrial palaeoclimate data i vegetation lake levels and geochemistry palaeodata in synthesis form are needed as benchmarks for the palaeoclimate modelling intercomparison project pmip advances since the last synthesis of terrestrial palaeodata from the last glacial maximum lgm call for a new evaluation especially of data from the tropics here pollen plant macrofossil lake level noble gas from groundwater and delta 18 o from speleothems data are compiled for 18 2 ka c 14 32 degrees n 33 degrees s the reliability of the data was evaluated using explicit criteria and some types of data were re analysed using consistent methods in order to derive a set of mutually consistent palaeoclimate estimates of mean temperature of the coldest month mtco mean annual temperature mat plant available moisture pam and runoff p e cold month temperature mat anomalies from plant data range from 1 to 2 k near sea level in indonesia and the s pacific through 6 to 8 k at many high elevation sites to 8 to 15k in s china and the se usa mat anomalies from groundwater or speleothems seem more uniform 4 to 6 k but the data are as yet sparse a clear divergence between mat and cold month estimates from the same region is seen only in the se usa where cold air advection is expected to have enhanced cooling in winter regression of all cold month anomalies against site elevation yielded an estimated average cooling of 2 5 to 3 k at modern sea level increasing to approximate to 6 k by 3000m how ever neotropical sites showed larger than the average sea level cooling 5 to 6 k and a non significant elevation effect whereas w and s pacific sites showed much less sea level cooling 1 k and a stronger elevation effect these findings support the inference that tropical sea surface temperatures ssts were lower than the climap estimates but they limit the plausible average tropical sea surface cooling and they support the existence of climap like geographic patterns in sst anomalies trends of pam and lake levels indicate wet lgm conditions in the w usa and at the highest elevations with generally dry conditions elsewhere these results suggest a colder than present ocean surface producing a weaker hydrological cycle more arid continents and arguably steeper than present terrestrial lapse rates such linkages are supported by recent observations on freezing level height and tropical ssts moreover simulations of greenhouse and lgm climates point to several possible feedback processes by which low level temperature anomalies might be amplified aloft

a novel proxy for terrestrial organic matter in sediments based on branched and isoprenoid tetraether lipids we propose a novel tracer for terrestrial organic carbon in sediments based on the analysis of tetraether lipids using high performance liquid chromatography mass spectrometry hplc ms analysis of terrestrial soil and peats shows that branched tetraether lipids are predominant in terrestrial environments in contrast to crenarchaeol the characteristic membrane lipid of non thermophilic crenarchaeota which is especially abundant in the marine and lacustrine environment based on these findings an index was developed the so called branched and isoprenoid tetraether bit index based on the relative abundance of terrestrially derived tetraether lipids versus crenarchaeol this bit index was applied to surface sediments from the angola basin where it was shown to trace the outflow of the congo river furthermore analyses of particulate organic matter from the north sea showed relatively higher bit indices in water column particulate organic matter near large river inputs a survey of globally distributed marine and lacustrine surface sediments shows that the bit index in these environments correlates with the relative fluvial input of terrestrial organic material making this index generally applicable the new proxy allows the rapid assessment of the fluvial input of terrestrial organic material in immature sediments up to 100 ma old

influence of climate change and uplift on colorado plateau paleotemperatures from carbonate clumped isotope thermometry the elevation history of earth s surface is key to understanding the geodynamic processes responsible for the rise of plateaus we investigate the timing of colorado plateau uplift by estimating depositional temperatures of tertiary lake sediments that blanket the plateau interior and adjacent lowlands using carbonate clumped isotope paleothermometry a measure of the temperature dependent enrichment of 13 c 18 o bonds in carbonates comparison of modern and ancient samples deposited near sea level provides an opportunity to quantify the influence of climate and therefore assess the contribution of changes in elevation to the variations of surface temperature on the plateau analysis of modern lake calcite from 350 to 3300 m elevation in the southwestern united states reveals a lake water carbonate temperature lct lapse rate of 4 2 0 6 c km analysis of miocene deposits from 88 to 1900 m elevation in the colorado river drainage suggests that the ancient lct lapse rate was 4 1 0 7 c km and temperatures were 7 7 2 0 c warmer at any one elevation than predicted by the modern trend the inferred cooling is plausible in light of pliocene temperature estimates off the coast of california and the consistency of lapse rates through time supports the interpretation that there has been little or no elevation change for any of the samples since 6 ma together with previous paleorelief estimates from apatite u th he data from the grand canyon our results suggest most or all of the plateau s lithospheric buoyancy was acquired 80 60 ma and do not support explanations that ascribe most plateau uplift to oligocene or younger disposal of either the farallon or north american mantle lithosphere

an environmental reconstruction of the sediment infill of the bogota basin colombia during the last 3 million years from abiotic and biotic proxies abstract the lacustrine sediments of the intramontane basin of bogota 4 n 2550 m altitude were collected in a 586 m deep core funza 2 absolute datings show sediment infill started c 3 2 ma and continued almost without interruptions as a result of the balance between tectonic subsidence and sediment infill analysis of downcore changes in lithology grain size facies loss on ignition loi and hydrosere vegetation at 20 cm intervals along the core produced a 2200 sample record of basin dynamics and lake level changes with a temporal resolution from c 800 years during the last 1 5 ma to c 2000 years from 1 5 to 3 2 ma we recognized 11 discrete sedimentary facies that reflect 4 different depositional environments facies 1 and 2 correspond to lacustrine environment where the loi is 20 a fluvio lacustrine environment is represented by the facies 3 4 5 7 and 9 a fluvial environment is reflected by facies 6 8 and 10 basin infill started with accumulation in a fluvio lacustrine environment between 586 and 530 m below the present day sediment surface of the basin in the 530 to 325 m interval c 3 1 5 ma the basin contained mainly shallow water and swamps in combination with some fluvial activity the 325 5 m interval 1 5 0 028 ma shows almost uninterrupted lacustrine paleoenvironmental conditions the uppermost 5 m reflect a fluvial paleoenvironment deposited by the bogota river and its tributaries the downcore changing ratio between shallow water aquatics myriophyllum ludwigia polygonum cyperaceae and aquatics of deeper water isoetes is indicative of lake level changes isoetes as an indicator of high water levels is not consistent with fluvial and fluvio lacustrine depositional regimes several lithological discontinuities evidenced by the sharp transition from swamp deposits to fluvio lacustrine and fluvial deposits are present in the core in the interval from 530 to 325 m in particular it is plausible that swamp deposits have been eroded during episodes during which the water table quickly raised or during events of sudden coarse fluvial input into the basin

pollen corrected leaf wax d h reconstructions of northeast african hydrological changes during the late miocene abstract plant leaf wax hydrogen isotope dwax reconstructions are increasingly being used to reconstruct hydrological change this approach is based upon the assumption that variations in hydroclimatic variables and in particular the isotopic composition of precipitation dp dominate dwax however modern calibration studies suggest that offsets between plant types may bias the dwax hydrological proxy at times of vegetation change in this study i pair leaf wax analyses with published pollen data to quantify this effect and construct the first vegetation corrected hydrogen isotopic evidence for precipitation dcorrp in marine sediments from deep sea drilling program site 231 in the gulf of aden spanning 11 4 3 8 ma late miocene and earliest pliocene i find 77 swings in dwax that correspond to pollen evidence for substantial vegetation change similarities between dp and dcorrp imply that the hydrological tracer is qualitatively robust to vegetation change however computed vegetation corrections can be as large as 31 indicating substantial quantitative uncertainty in the raw hydrological proxy the resulting dcorrp values quantify hydrological change and allow us to identify times considerably wetter than modern at 11 09 7 26 5 71 and 3 89 ma more generally this novel interpretative framework builds the foundations of improved quantitative paleohydrological reconstructions with the dwax proxy in contexts where vegetation change may bias the plant based proxy the vegetation corrected paleoprecipitation reconstruction dcorrp represents the best available estimate as proof of concept for an approach that i hope will be refined and more broadly applied

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

paleoelevation records from lipid biomarkers application to the tropical andes new results from two novel lipid biomarker based proxies help to constrain the late cenozoic surface elevation history of the eastern cordillera in the tropical northern andes of colombia previous well known studies have suggested rapid latest miocene pliocene 6 3 ma uplift on the basis of an abrupt shift in pollen species assemblages within sedimentary basin fill of the elevated bogota plateau from resampling of these original study localities we provide a revised chronology based on magnetic polarity stratigraphy and we evaluate paleotemperatures using the mbt cbt indices methylation of branched tetraethers cyclization of branched tetraethers and hydrogen isotopic composition d of leaf waxes as two independent proxies of past surface elevation reconstructed paleotemperatures from the mbt cbt proxy show a more gradual cooling trend from ca 7 6 ma to present consistent with less than 1000 m of elevation gain since latest miocene pliocene time and in agreement with geologic evidence for accelerated shortening and exhumation at this time the leaf wax isotopic data on the other hand lack a systematic trend potentially due to fractionation changes associated with uplift induced turnover in floral populations such changes could obscure isotopic variations in meteoric water suggesting that leaf wax isotopic compositions may not provide a direct proxy for elevation in this particular situation involving uplift in a heterogeneous tropical environment more promising in this case is the mbt cbt proxy which may offer a suitable alternative to carbonate based paleoelevation proxies in tropical regions where year round high precipitation rates prevent formation of soil carbonates

the pliocene and quaternary of the high plain of bogota colombia a history of tectonic uplift basin development and climatic change abstract the high plain of bogota in the eastern cordillera of colombia represents a large tectonic basin that is filled with hundreds of metres of lacustrine and fluvial sediments in the centre of the basin the sediment sequence attains a thickness of nearly 600 m and covers a time span of the last 3 ma late pliocene quaternary still older sediments of mainly fluvial origin cover the adjacent mountain slopes the age of these sediments reaches back into the late miocene to 6 ma and older the sediment sequence of the bogota area has been the subject of extensive stratigraphical and palynological studies for decades the results of these studies have provided a unique picture of the pliocene quaternary geological history of a tropical montane region three main factors have influenced the evolution of the landscape sedimentation and vegetation development these are the tectonic uplift of the andes between ca 5 and 3 ma the development of the large tectonic sedimentary basin of bogota after ca 3 5 ma and the quaternary climatic fluctuations and glaciations starting shortly after ca 2 7 ma

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

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

high temperature environments of human evolution in east africa based on bond ordering in paleosol carbonates many important hominid bearing fossil localities in east africa are in regions that are extremely hot and dry although humans are well adapted to such conditions it has been inferred that east african environments were cooler or more wooded during the pliocene and pleistocene when this region was a central stage of human evolution here we show that the turkana basin kenya today one of the hottest places on earth has been continually hot during the past 4 million years the distribution of 13c 18o bonds in paleosol carbonates indicates that soil temperatures during periods of carbonate formation were typically above 30 c and often in excess of 35 c similar soil temperatures are observed today in the turkana basin and reflect high air temperatures combined with solar heating of the soil surface these results are specific to periods of soil carbonate formation and we suggest that such periods composed a large fraction of integrated time in the turkana basin if correct this interpretation has implications for human thermophysiology and implies a long standing human association with marginal environments

spatial patterns of soil n alkaneδd values on the tibetan plateau implications for monsoon boundaries and paleoelevation reconstructions 1 between 2010 and 2011 this project collected and analyzed forty nine superficial soil samples for wax derivedn alkane d values dwax along a south to north transect of the tibetan plateau from the southern plateau and nepalese himalayas passing through the nam co basin to qilian mountains twenty two paired river water samples were also collected from northeastern tibet during this period and analyzed for d drw the drw and dwaxvalues become progressively more negative northward from 27 5 n and reach a minimum at 30 6 n nam co basin north of the nam co basin to 35 n isotope values increase due to increasing contributions from the year round westerlies and recycled moisture from the plateau relatively high and constant dwax and drw values prevail in areas north of 35 n in northeastern tibet results show that these dwaxvalues vary considerably with location and relate closely to the influences of the summer monsoon and circulation changes these changes track the spatial variability of isotopes from modern river water and precipitation at large spatial scales paleoelevation reconstructions should take into account the impact of mixing between continental and monsoon derived moisture on the relationships with elevation and dwax and linear isotopic lapse rates for central northeastern tibet based on extended and more sensitive relative to 18o dwax and drw values we infer that in the past the westerlies reached further south to the north piedmont of the nyainqentanglha range and that indian summer monsoon moisture pushes across the tanggula mountains and approaches the kunlun mountains

soil n alkane δd vs altitude gradients along mount gongga china the altitude effect on the isotopic composition of precipitation and its application to paleoelevation reconstruction using authigenic or pedogenic minerals have been intensively studied however there are still no studies on variations in biomarker d along altitude transects to investigate its potential as a paleoelevation indicator although it has been observed that d of higher plant lipid may record changes in precipitation d dp here we present d values of higher plant derived c27 c29 and c31n alkanes from surface soil along the eastern slope of mount gongga china with great changes in physical variables and vegetation over a range from 1000 to 4000 m above sea level the weighted mean d values of these n alkanes dwax show significant linear correlations with predicted dp values r2 0 76 with an apparent isotopic enrichment ewax p of 137 9 indicating that soil dwax values track overall dp variation along the entire altitudinal transect leaf dwax is also highly correlated with mountain altitude by a significant quadratic relationship r2 0 80 evapotranspiration is found declining with altitude potentially lowering dwax values at higher elevations however this evapotranspiration effect is believed to be largely compensated by the opposing effect of vegetation changes resulting in less varied ewax p values over the slope transect this study therefore confirms the potential of using leaf dwax to infer paleoelevations and more generally to infer the d of precipitation

calibration of the clumped isotope geothermometer in soil carbonate in wyoming and nebraska usa implications for paleoelevation and paleoclimate reconstruction abstract recent work has shown that soil carbonates typically form as the soil dries after seasonal rainfall and therefore record seasonal aspects of climate rather than mean annual conditions because soil carbonate formation is closely related to the timing of local rainfall and drying it is necessary to understand the formation seasonality and temperature and soil water o 18 values recorded in modern soil carbonate before accurate estimates of stable isotope based paleoelevation and paleoclimate can be made here we study carbonate clumped isotope 47 and oxygen isotope o 18 compositions of modern soil carbonates and seasonal variations of soil moisture and temperature of nearby climate stations in wyoming and western nebraska usa to understand the seasonality of soil carbonate formation in semi arid to arid temperate montane settings we find that soil carbonate clumped isotope temperatures t 47 are 3 5 c higher than mean summer air temperature and are similar to or higher than average summer soil temperature at depths 40 cm soil moisture dramatically decreases in early summer following the cessation of spring rains and snowmelt and shows only brief increases after major mid late summer rain events soil water o 18 values calculated using carbonate o 18 and t 47 values are similar to the o 18 values of local mean summer precipitation these lines of evidence suggest that soil carbonates in our study area formed during times of soil dewatering in early summer and after major summer storm events in mid late summer and in or near equilibrium with mean summer precipitation o 18 values t 47 values of modern soil carbonates are inversely correlated with elevation with a lapse rate 4 0 c km similar to the modern air and soil temperature lapse rates calculated soil water o 18 values also are inversely correlated with elevation with a lapse rate of 3 7 km sample elevations can be reconstructed using both t 47 values and calculated soil water o 18 values between 900 m and 2600 m in our studied area with an accuracy of 0 5 km or less however o 18 values of precipitation and soil water reflect the complex interaction of climatic environmental and topographic conditions prior to carbonate formation whereas t 47 values may be influenced by site specific conditions we suggest that both soil carbonate t 47 values and calculated soil water o 18 values should be used to corroborate paleoelevation reconstruction and the seasonal nature of soil carbonate formation should be considered when soil carbonate t 47 values and o 18 values are applied for paleoclimate reconstruction

climatic forcing of asymmetric orogenic evolution in the eastern cordillera of colombia new apatite fission track data paleoelevation estimates from paleobotany and recently acquired geological data from the eastern cordillera of colombia document the onset of increased exhumation rates in the northeastern andes at ca 3 ma the eastern cordillera forms an efficient orographic barrier that intercepts moisture laden winds sourced in the amazon lowlands leading to high rainfall and erosion gradients across the eastern flank of the range in contrast the drier leeward western flank is characterized by lower rates of deformation and exhumation in light of the geological evolution of the eastern cordillera the combination of these data sets suggests that the orographic barrier reached a critical elevation between ca 6 and ca 3 ma which ultimately led to protracted yet more focused erosion along the eastern flank sequentially restored structural cross sections across the eastern flank of the eastern cordillera indicate that shortening rates also have increased during the past 3 ma from fission track and structural cross section balancing we infer that accelerated exhumation led to increasing tectonic rates on the eastern flank creating a pronounced topographic and structural asymmetry in the eastern cordillera the tectonic and climatic evolution of this orogen thus makes it a prime example of the importance of climatic forcing on tectonic processes

a new approach to stable isotope based paleoaltimetry implications for paleoaltimetry and paleohypsometry of the high himalaya since the late miocene the change in oxygen isotopic composition of precipitation is modeled using equilibrium fractionation during rayleigh distillation linked to the thermodynamics of atmospheric ascent and water vapor condensation the primary controllers of the vertical variation in isotopic composition with elevation are the low elevation temperature and relative humidity as these control the vertical distribution of condensation an empirical fit of precipitation versus model condensation based on alpine stations is derived this fit is represented in the model as the weighted mean composition of condensation within a 1000 m thick air parcel 1500 500 m above the ground surface and is used for all other regions comparison of model versus observed modern precipitation reveals a close fit particularly of more highly elevated sites comparison of modern waters in the himalayas and southern tibet with model predictions particularly as revealed by comparison of observed and predicted hypsometry provides additional support to the validity of the model finally application of this model to estimates of paleo waters in the himalayas and southern tibet reveals that this region had already achieved its present hypsometry by the late miocene about 10 ma ago fl 2001 published by elsevier science b v

magnetic polarity and fission track chronology of a late pliocene pleistocene paleoclimatic proxy record in the tropical andes abstract two sections exposing a late pliocene pleistocene sedimentary sequence in the marginal valleys of the bogota basin colombian andes south america were sampled for paleomagnetic analysis magnetostratigraphy and fission track dates of tephra beds provide a detailed geochronologic calibration for the sedimentary basin measurements of magnetic susceptibility complement the regional environmental record provided by lithological and palynological evidence sedimentation in the bogota basin started in the early part of the gauss chron at ca 3 2 myr the oldest recorded sediments belong to the guasca member of the upper tilata formation they were deposited in a lacustrine paludal environment near the end of the tectonic uplift in the bogota area and or under pliocene climatic conditions that were warmer than today repeated climate cooling associated with glaciations in the surrounding mountains resulted in the deposition of a fluvial lacustrine complex referred to as the subachoque formation the first glaciation is placed near the gauss matuyama polarity reversal at 2 6 myr a lithologic change in the subachoque formation marked by coarser grained fluvial deposits and a possible increase in amplitude of the magnetic susceptibility signal occurs near the matuyama brunhes boundary at 0 8 myr indicating a shift toward higher magnitude climate oscillations

strong plate coupling along the nazca south america convergent margin the force balance in plate tectonics is fundamentally important but poorly known here we show that two prominent and seemingly unrelated observations trench parallel gravity anomalies along the nazca south america margin that coincide with the rupture zones of great earthquakes and a rapid slowdown of nazca south america convergence over the past 10 m y provide key insights both result from rapid miocene pliocene uplift of the andes and provide quantitative measures of the magnitude and distribution of plate coupling along the nazca south america margin we compute the plate tectonic force budget using global models of the faulted lithosphere coupled to high resolution mantle circulation models and find that andean related plate margin forces are comparable to plate driving forces from the mantle and they have sufficient magnitude to account for pronounced bathymetry variations along the trench our results suggest that plate coupling gravity anomalies and bathymetry variations along a given trench are all controlled by long term stress variations in the upper portion of plate boundaries and that an explicit budget of driving and resisting forces in plate tectonics can be obtained for the convergent margin considered here spatial variations in the effective coefficient of friction associated with the distribution of lubricating sediments entering the trench are by comparison of minor importance

δd values of n alkanes in tibetan lake sediments and aquatic macrophytes a surface sediment study and application to a 16 ka record from lake koucha abstract a set of lake surface sediment samples and aquatic macrophytes from the eastern and central tibetan plateau and a sediment core from koucha lake northeastern tibetan plateau were analysed for hydrogen isotope signals of aliphatic lipid biomarkers the d values of n alkanes were correlated with those of meteoric water in the summer months and showed increasing pearson correlation coefficients with increasing n alkane chain length r 0 80 for n c 31 while in samples from the most humid regions southeastern tibetan plateau the apparent enrichment factors between meteoric water and lipids are close to those reported for other humid sites e 135 for mid chain and 125 for long chain n alkanes they become smaller e 118 to 41 mean value 86 at sites with a negative moisture balance northeastern and central tibetan plateau and qaidam basin this might be caused by enrichment in deuterium of the source water used for lipid synthesis as a result of lake water evaporation and soil and leaf water evapotranspiration in the core from lake koucha decreasing d values of all n alkanes between 15 and 10 cal ka bp give evidence for an intensification of the asian summer monsoon at ca 9 cal ka bp a ca 15 shift towards higher d values of mid chain n alkanes suggests enhanced evaporation of the lake water which outweighs higher precipitation amounts because of a temperature increase during the early holocene monsoonal maximum only a few surface sediment samples show a significant offset between d values of mid chain n alkanes and n c 31 d mid n c31 and no systematic dependence between this offset and environmental parameters such as mean annual precipitation was found in the core available data for most samples also do not show a significant offset only a slight increase 15 of d mid n c31 at ca 10 0 cal ka bp and a decrease 17 at ca 6 8 cal ka bp might indicate wetter and drier conditions respectively however interpretation of d mid n c31 throughout the record is difficult because of a lack of reliable data for n c 31 in key sections of the core so more records are necessary to further test the potential applicability of d mid n c31 as a proxy for palaeo hydrological conditions

can sedimentary leaf waxes record d h ratios of continental precipitation field model and experimental assessments abstract d h ratios of leaf waxes d wax derived from terrestrial plants and preserved in lake sediments can provide important information on past continental hydrology ideally d wax can be used to reconstruct precipitation d h ratios d p which is a well established paleoclimate proxy however many other factors such as vegetation and relative humidity rh also affect d wax variation how the combination of these factors affects sedimentary d wax is unclear here we use a transect of 32 lake surface sediments across large gradients of precipitation relative humidity and vegetation composition in the southwestern united states to study the natural factors affecting sedimentary d wax d values of c 28 n alkanoic acids show significant correlation with d p values r 2 0 76 with an apparent isotopic enrichment of 99 8 indicating that sedimentary d wax values track overall d p variation along the entire transect leaf waxes produced by plants grown under controlled conditions rh 80 60 40 show a small increase in d h ratios as rh decreases consistent with prediction from the craig gordon model however the isotopic effect of rh on d wax along the natural transect is partially countered by the opposing influence of vegetation changes the correlation between d wax and d p values is significantly higher r 2 0 84 in the drier portions of the transect than in the wetter regions r 2 0 64 this study suggests that d h ratios of sedimentary leaf waxes can be used as a proxy for precipitation d variations with particularly high fidelity in dry regions although more studies in other regions will be important to further test this proxy

climate driven bedrock incision in an active mountain belt measurements of fluvial bedrock incision were made with submillimeter precision in the east central range of taiwan where long term exhumation rates and precipitation driven river discharge are independently known they indicate that valley lowering is driven by relatively frequent flows of moderate intensity abrasion by suspended sediment is an important fluvial wear process and channel bed geometry and the presence of widely spaced planes of weakness in the rock mass influence erosion rate and style

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

distributions of branched gdgts in a tropical lake system implications for lacustrine application of the mbt cbt paleoproxy branched glycerol dialkyl glycerol tetraether gdgt lipids are abundant and ubiquitous in lake sediments potentially allowing for a paleolimnological application of the so called mbt cbt proxy methylation index of branched tetraethers cyclization ratio of branched tetraethers to investigate the origin and characteristics of these compounds in lacustrine environments we examined the distributions of gdgts in soils river sediments and lake sediments from lake towuti on the island of sulawesi indonesia we found significant differences in the degree of methylation and cyclization expressed by way of the mbt and cbt indices between the soil samples and the aquatic samples suggesting that there may be in situ production of gdgts in the aquatic environment based on these findings we urge caution in the application of the mbt cbt paleoproxy to lake sediments and encourage more rigorous study of these compounds in freshwater environments

cenozoic contractional reactivation of mesozoic extensional structures in the eastern cordillera of colombia 1 the eastern cordillera of colombia is key to understanding the role of inherited basement anisotropies in the evolution of active noncollisional mountain belts in particular the rio blanco guatiquia region of the eastern cordillera is exemplary in displaying a variety of phenomena that document the importance of the orientation geometry and segmentation of preorogenic anisotropies we document the first unambiguous evidence that extensional basement structures played an important role in determining the locus of deformation during contractional reactivation in the eastern cordillera detailed structural field mapping and analysis of industry seismic reflection profiles have helped to identify the inherited san juanito naranjal and servita normal faults and associated transfer faults as important structures that were inverted during the cenozoic andean orogeny apparently the more internal faults in the former rift basin were not properly oriented for an efficient reactivation in contraction however these faults have a fundamental role as strain risers as folding is concentrated west of them in contrast reactivated normal faults such as the more external servita fault are responsible for uplifting the eastern flank of the eastern cordillera in addition these structures are adjacent and intimately linked to the development of thin skinned faults farther east in part the superimposed compression in this prestrained extensional region is compensated by lateral escape the dominant presence of basement involved buckling and thrusting and the restricted development of thin skinned thrusting in this inversion orogen makes the eastern cordillera a close analog to the intraplate atlas mountains of morocco and other inverted sectors of the andean orogen farther south

pleistocene to present north andean escape abstract this study compiles 20 published field geologic estimates of displacement rates for the northern andes such as displaced glacial moraines and offset pyroclastic flow and compares them to published global positioning system gps measurements dated displacements compiled in this study were obtained from the gulf of guayaquil pallatanga chingual la sofia and cayambe afiladores sibundoy fault systems in ecuador and southern colombia and the bocono fault system in venezuela right lateral slip estimates on the individual fault segments range from 2 mm a to 10 mm a the mean estimated geologic slip rate for the last 86 000 years is 7 6 mm a this estimate is very similar to the gps measurements of present day motion at the 2 sigma level published gps results suggest that a large part of the northern andes is escaping to the northeast relative to stable south america at a rate of 6 2 mm a the gps displacement rates of seven sites in venezuela colombia and ecuador are statistically identical at the 95 confidence level four geologic estimates indicate that slip rates of 4 to 10 mm a continued back to 1 8 ma no geologic slip estimates have been reported for ecuador prior to that time period the escape of the north andes is believed to be a result of increased coupling between the obliquely subducting nazca plate and the overriding south american plate due to the subduction of the carnegie ridge in the ecuador colombia trench if this is correct the slip estimates for the north andes suggest that the carnegie ridge arrived at the trench prior to 1 8 ma in the eastern cordillera of colombia strike slip crustal earthquakes reflect slip partitioning on high angle faults located above crustal detachment ramps across a 200 km wide zone intermediate depth mantle earthquakes indicate that brittle shearing extends to the base of the lithosphere

sources of local and regional variability in the mbt cbt paleotemperature proxy insights from a modern elevation transect across the eastern cordillera of colombia abstract distributions of brgdgts branched glycerol dialkyl glycerol tetraethers in soils have been utilized in the literature as a proxy for temperature and ph via the mbt and cbt indices methylation of branched tetraethers and cyclization of branched tetraethers respectively however there is substantial scatter in the empirical relationships between the global mbt cbt index and modern temperature resulting in uncertainty as large as 5 0 c in reconstructed paleotemperature in this study we sought to determine the magnitude of several sources of calibration error using a new set of samples spanning a large gradient in elevation ca 3000 m and temperature ca 16 c across an andean transect in the eastern cordillera of colombia using in situ temperature monitoring this field study of an equatorial montane location provided an opportunity to investigate several potential confounding factors affecting the mbt cbt paleothermometer including the mismatch between air temperature and actual soil temperature and the effect of soil moisture on brgdgt production in the well constrained environment of our study we determined the rmse root mean squared error for a local calibration of the mbt cbt proxy to be 3 0 c in contrast to the 5 0 c value reported in the most recent global calibration a comparison between in situ soil temperature measurements at our soil sampling locations and interpolated weather station temperature data indicates that errors in interpolation schemes are not likely to be a significant contributor to the observed scatter in the mbt cbt temperature relationship rather we conclude that the majority of the 3 c scatter in this calibration for the northern andes arises from transient site specific variation in factors such as soil moisture and nutrient availability with several cases showing a difference of up to 7 8 c between closely spaced sites

hot summers in the bighorn basin during the early paleogene during the early paleogene climate in continental interiors is thought to have been warmer and more equable than today but estimates of seasonal temperature variations during this period are limited global and regional climate models of the paleogene predict cooler temperatures for continental interiors than are implied by proxy data and predict a seasonal range of temperature that is similar to today here we present a record of summer temperatures derived from carbonate clumped isotope thermometry of paleosol carbonates from paleogene deposits in the bighorn basin wyoming united states our summer temperature estimates are 18 c greater than mean annual temperature estimated from analysis of fossil leaves when coupled these two records yield a seasonal range of temperature similar to that in the region today with winter temperatures that are near freezing these data are consistent with our high resolution climate model output for the early eocene in the bighorn basin we suggest that temperatures in continental interiors during the early paleogene greenhouse were warmer in all seasons but not more equable than today if generally true this removes one of the long standing paradoxes in our understanding of terrestrial climate dynamics under greenhouse conditions

tracing soil organic carbon in the lower amazon river and its tributaries using gdgt distributions and bulk organic matter properties abstract in order to trace the transport of soil organic carbon oc in the lower amazon basin we investigated the distributions of crenarchaeol and branched glycerol dialkyl glycerol tetraethers gdgts by analyzing riverbed sediments and river suspended particulate matter spm collected in the solimoes amazon river mainstem and its tributaries the branched and isoprenoid tetraether bit index a proxy for river transported soil oc into the ocean was determined from the distributions of these gdgts the gdgt derived parameters were compared with other bulk geochemical data i e c n ratio and stable carbon isotopic composition the gdgt derived and bulk geochemical data indicate that riverine spm and riverbed sediments in the lower amazon river and its tributaries are a mixture of c3 plant derived soil oc and aquatic derived oc the branched gdgts in the spm and riverbed sediments did not predominantly originate from the high andes soils 2500 m in altitude as was suggested previously however further constraint on the soil source area of branched gdgts was hampered due to the deficiency of soil data from the lower montane forest areas in the andes our study also revealed seasonal and interannual variation in gdgt composition as well as soil oc discharge which was closely related to the hydrological cycle by way of a simple binary mixing model using the flux weighted bit values at obidos the last gauging station in the amazon river we estimated that 70 80 of the poc pool in the river was derived of soil oc however care should be taken to use the bit index since it showed a non conservative behaviour along the river continuum due to the aquatic production of crenarchaeol further investigation using a continuous sampling strategy following the full hydrological cycle is required to fully understand how soil derived gdgt signals are transformed in large tropical river systems through their transport pathway to the ocean

cenozoic tectonic and topographic evolution of the northern sierra nevada california through stable isotope paleoaltimetry in volcanic glass we determine the paleoelevation of the northern sierra nevada california in the oligocene based on hydrogen stable isotope compositions of meteoric water preserved within volcanic glass from ignimbrites sampled across the range a 48 decrease in the isotopic composition of hydrated glass from ignimbrites located near paleosea level to ignimbrites 100 km to the east refl ects the effect of ancient high topography on precipitation these data show that 31 28 ma ago the northern sierra nevada had a steep western gradient and elevations similar to the present this study placed in the context of other paleoaltimetry studies suggests that the range was a high topographic feature throughout the cenozoic and that the majority of uplift occurred in the late cretaceous to early cenozoic much earlier than some studies have proposed

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

stable isotope paleoaltimetry a critical review stable isotope paleoaltimetry makes use of systematic trends in the distribution and isotopic composition of modern precipitation with climate and topography and of the potential to estimate the isotopic composition of paleoprecipitation from authigenic in situ formed minerals to illustrate the usefulness as well as potential limitations of this method we review 1 processes controlling the isotopic composition of modern precipitation 2 stable isotope data from modern precipitation across regions of high topography and 3 stable isotope data from authigenic minerals that have been used to infer paleotopography from this we conclude that stable isotope studies of authigenic minerals can permit useful inferences on paleotopography with uncertainties that critically depend on a detailed understanding of local to global scale paleoclimate during the time interval of interest

microbial lipid records of highly alkaline deposits and enhanced aridity associated with significant uplift of the tibetan plateau in the late miocene saline alkaline sediments and soils are widespread in arid and semiarid regions but their occurrence in ancient dry periods remains unknown due to the lack of a suitable proxy on the basis of investigations of modern chinese soils with a wide ph range of 3 5 9 1 we suggest that the microbial lipid ratio r i b i e the abundance ratio of archaeal isoprenoid gdgts glycerol dialkyl glycerol tetraethers to bacterial branched gdgts indicates the presence of drought induced alkaline deposits in terrestrial settings the r i b is invariant in modern soils with ph 600 mm but it increases sharply at higher ph values and lower mean annual precipitation i b ratio in a fluviolacustrine section in the zhada basin of the southwestern tibetan plateau covering the time period 9 2 2 6 m y ago the r i b ratio remains relatively stable in most intervals but exhibits maxima in some horizons indicative of the occurrence of severe drought and alkaline deposits in the basin catchment these occur in fluvial sediments deposited 9 m y ago a critical time with respect to the intensification of the east asian and indian monsoons and the significant uplift of the plateau that has previously been associated with enhanced aridity in central asia

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

δd values of individual n alkanes from terrestrial plants along a climatic gradient implications for the sedimentary biomarker record abstract the compound specific hydrogen isotope composition d of sedimentary n alkanes is increasingly used as a palaeoclimate proxy to explore the origin of the hydrogen isotope signal of n alkanes from higher terrestrial plant biomass in sedimentary organic matter of small lakes we have analysed the n alkane composition and d values of 31 plant biomass samples birch betula beech fagus oak quercus alder alnus hornbeam carpinus and myrtle myrtus as well as non stomata containing sphagnum cladonia and moss from 14 sites along a climatic gradient from northern finland to southern italy eleven of the sites were previously investigated for the n alkane d values in adjacent lake sediments and are compared to the leaf wax n alkane d values the distribution of terrestrial n alkanes in lake sediments was not found to be characteristic of the dominant vegetation around the lake evidently n alkane distributions within the same species at different sites were found to be variable these findings complicate the use of certain n alkane distributions in sediments as a palaeoenvironmental indicator d values of plant biomass n alkanes show a significant positive correlation with the precipitation d values biomass n alkane d values are in general less negative than the associated sedimentary n alkanes of terrestrial origin possibly due to the stronger evapotranspiration during the summer when sampling took place this suggests that n alkanes in leaves show seasonal variations and the sedimentary organic matter receives the lighter isotope signal of the autumn when most leaves are incorporated into the sediment the variability of the d values from non stomata containing plants is much higher than for broadleaf trees since stomata can regulate water loss through evapotranspiration the average chain length acl of n alkanes from deciduous tree leaves increases from north to south with increasing acl the hydrogen isotopic fractionation e between source water and n alkanes also increases our results prove that terrestrial n alkane d values record the d value of precipitation modified by the amount of isotope enrichment in the leaf water due to plant anatomy stomata vs no stomata and site specific meteorological conditions such as evapotranspiration relative humidity and soil moisture therefore terrestrial n alkanes in lake sediments can deliver information on changes in these parameters over geological timescales in lake sediments where aquatic n alkanes such as n c 17 record the lake water d value the isotopic difference between terrestrial and aquatic n alkanes could therefore be used to reconstruct changes in evapotranspiration

the orbital tuned marine oxygen isotope record applied to the middle and late pleistocene pollen record of funza colombian andes abstract assuming that orbital variations are the main external cause of the succession of late pleistocene ice ages deep sea stratigraphers developed an orbital tuned chronology of the marine oxygen isotope record the pollen record of funza eastern cordillera colombia displays in great detail long range altitudinal shifts of the forest line being also an expression of long range fluctuating global temperatures both records of palaeotemperature were visually correlated 48 isotopic events are assumedly reflected in the pollen record this enables an orbital tuning of the initial time frame of the pollen record which was based on 14 dated volcanic ash horizons and provides a detailed record of changes in sediment accumulation in the sedimentary basin of bogota inferences for the time frame of the pollen record of paramo de agua blanca from the same area are discussed

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

geodynamics of the northern andes subductions and intracontinental deformation colombia new regional seismological data acquired in colombia during 1993 to 1996 and tectonic field data from the eastern cordillera ec permit a reexamination of the complex geodynamics of northwestern south america the effect of the accretion of the baudo panama oceanic arc which began 12 myr ago is highlighted in connection with mountain building in the ec the istmina and ibague faults in the south and the santa marta bucaramanga fault to the northeast limit an e se moving continental wedge progressive indentation of the wedge is absorbed along reverse faults located in the foothills of the cordilleras northward of 5 n and transpressive deformation in the santander massif crustal seismicity in colombia is accurately correlated with active faults showing neotectonic morphological evidences intermediate seismicity allows to identify a n ne trending subduction segment beneath the ec which plunges toward the e se this subduction is interpreted as a remnant of the paleo caribbean plateau pcp as suggested by geological and tomographic profiles the pcp shows a low angle subduction northward of 5 2 n and is limited southward by a major e w transpressive shear zone normal oceanic subduction of the nazca plate np ends abruptly at the southern limit of the baudo range northward the np subducts beneath the choco block overlapping the southern part of the pcp cenozoic shortening in the ec estimated from a balanced section is 120 km stress analysis of fault slip data in the ec northward of 4 n indicates an e se orientation of 1 in agreement with the pcp subduction direction northward near bucaramanga two stress solutions were observed 1 a late andean n80 e compression and 2 an early andean nw se compression

palaeo altimetry of the late eocene to miocene lunpola basin central tibet the elevation history of the tibetan plateau provides direct insight into the tectonic processes associated with continent continent collisions here we present oxygen isotope based estimates of the palaeo altimetry of late eocene and younger deposits of the lunpola basin in the centre of the plateau which indicate that the surface of tibet has been at an elevation of more than 4 kilometres for at least the past 35 million years we conclude that crustal but not mantle thickening models combined with plate kinematic solutions of india asia convergence are compatible with palaeo elevation estimates across the tibetan plateau

clastic deposition provenance and sequence of andean thrusting in the frontal eastern cordillera and llanos foreland basin of colombia sedimentological provenance and detrital thermochronological results for basin fill at the modern deformation front of the northern andes 6 n latitude provide a long term eocene to pliocene record of foreland basin sedimentation along the eastern cordillera llanos basin boundary in colombia lithofacies assemblages and paleocurrent orientations in the upward coarsening 5 km thick succession of the nunchia syncline reveal a systematic shift from craton derived shallow marine distal foreland back bulge accumulation in the mirador formation to orogen sourced deltaic and coastal influenced sedimentation of the distal to medial foreland foredeep in the carbonera and leon formations to anastomosing fluvial and distributive braided fluvial megafan systems of the proximal foreland foredeep to wedge top basin in the lower and upper guayabo formation these changes in depositional processes and sediment dispersal are supported by up section variations in detrital zircon u pb and u th he ages that record exhumation of evolving compartmentalized sediment source areas in the eastern cordillera the data are interpreted in terms of a progressive eastward advance in fold and thrust deformation with late eocene oligocene deformation in the axial zone of the eastern cordillera along the western edge of floresta basin soapaga thrust early miocene reactivation inversion of the eastern margin of the mesozoic rift system pajarito and guaicaramo thrusts and middle late miocene propagation of a footwall shortcut fault yopal thrust that created the nunchia syncline in a wedge top piggyback setting of the eastern foothills along the transition from the eastern cordillera to llanos foreland basin collectively the data presented here for the frontal eastern cordillera define a general in sequence pattern of eastward advancing fold and thrust deformation during cenozoic east west shortening in the colombian andes

influence of terrestrial vegetation on leaf wax δd of holocene lake sediments abstract the hydrogen isotope composition of terrestrial plant leaf wax in sediments is increasingly used as a paleoclimatic indicator modern calibration studies suggest that paleoclimatic interpretation of leaf wax d values requires consideration of the differences in the apparent fractionation of hydrogen isotopes among different groups of plants however it is not common that paleoecological data are used to help interpret leaf wax d profiles here we assess the relative importance of factors influencing millennial scale shifts in d values of n alkanoic acids at steel lake minnesota usa an extensively studied site with independent records of vegetation composition d of input water to the lake and evaporation the d values of the n c 28 alkanoic acid d c28 vary between 190 and 168 and do not correlate with d of input water or the extent of evaporation however d c28 is negatively correlated with the 13 c values of the n c 28 alkanoic acid 13 c c28 the correlation along with pollen assemblage and carbonate 13 c records suggests that holocene shifts between forest and grassland and or in the water use efficiency of c 3 plants influenced the stratigraphic variation in leaf wax d thus paleoecological information such as that inferred from pollen assemblages and carbon isotopes of plant derived compounds may aid paleoclimatic interpretation of leaf wax d profiles from lake sediments

deuterium and oxygen isotopes paleoelevations of the sierra nevada and cenozoic climate although geomorphic observations suggest that the sierra nevada has tilted so that the crest has risen 1 2 km since late miocene time deuterium and oxygen 18 isotope concentrations in cenozoic geologic materials decrease eastward across california and nevada similarly to those in modern orographically induced precipitation as if little change in sierra nevadan elevations has occurred since eocene time orographic precipitation however depends on the amount of moisture in the atmosphere which in turn can be much larger in warm air as in eocene or oligocene time and in summer than in the cooler air characteristic of present day dominantly winter precipitation moreover the integrated rainout of vapor and hence presumably in stable isotope concentrations in the remaining vapor depends largely on the difference in heights traversed by air masses not slopes of mountain ranges thus if due simply to orographically induced rainout both eocene and oligocene variations in deuterium isotopes across the sierra nevada and miocene quaternary differences in deuterium and oxygen isotopes between the great valley of california and the basin and range place only weak constraints on the slope or past elevations of the sierra nevada they do not necessarily contradict the inference that the crest of the sierra nevada has risen 1000 m or more since late miocene time

distributions and temperature dependence of branched glycerol dialkyl glycerol tetraethers in recent lacustrine sediments from china and nepal 1 glycerol dialkyl glycerol tetraether gdgt membrane lipids in surface sediments from 24 lakes in china and nepal were analyzed the result shows that branched gdgt lipids occur widely in the studied lake sediments the different distribution of branched gdgts between the chinese soils from weijers et al 2007b and the chinese lake sediments indicates that the branched gdgts in the lacustrine sediment are the mixture of allochthonous and autochthonous branched gdgts our result supports the suggestion that temperature is the principal factor affecting the distribution of gdgts seasonality sources and precipitation increase the uncertainty of the correlation between the methylation index of branched tetraethers mbt cyclization ratio of branched tetraethers cbt proxy and the temperature the correlations of the mbt cbt index with mean annual air temperature t for the global lakes are t 6 803 7 062 cbt 37 090 mbt n 139 p 0 0001 r2 0 62 and rmse 5 24 c for the global lakes with ph 8 5 t 3 949 5 593 cbt 38 213 mbt n 100 p 0 0001 r2 0 73 and rmse 4 27 c the significant correlation suggests that the mbt cbt proxy might be used as a potential paleotemperature proxy in the limnic environment the mbt cbt proxy provides an independent way to evaluate and verify the sensitivities of the different proxies for paleotemperature reconstruction from lacustrine sediments

paleoelevation estimates for the northern and central proto basin and range from carbonate clumped isotope thermometry 1 quantitative paleoelevation histories can help explain both why and how widespread cenozoic extension occurred in the basin and range province of western north america we present new estimates of preextensional paleoelevations for the northern and central basin and range using clumped isotope 47 thermometry of lacustrine carbonates collected from each region comparison of carbonate 47 derived mean annual air temperature maat estimates 16 c 20 c for the late cretaceous eocene sheep pass basin of east central nevada with published maat estimates for the eocene coastal northern sierra nevada 20 c 25 c suggests that the early paleogene sheep pass basin had a paleoelevation of 2 km such a modest paleoelevation suggests that either 1 the proto northern basin and range did not attain maximum paleoelevations of 3 4 km until the late eocene early oligocene or 2 the sheep pass basin was a local high relief 1 km setting contained within a 3 km orogenic highland nevadaplano similarity of 47 derived maat estimates 17 c 24 c for carbonates from the central basin and range and the near sea level southern sierra nevada bena basin indicate that middle miocene paleoelevations in the death valley region were 1 5 km these fairly low paleoelevations are incompatible with preextensional crustal thicknesses 52 km and indicate that mean elevation change was minor 500 m and lithospheric mass was not conserved during 100 neogene extension of the central basin and range but was instead likely compensated by synextensional magmatic additions to the crust

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

the paleoaltimetry of tibet an isotopic perspective stable isotopes provide a valuable perspective on the timing of elevation change of the tibetan plateau we begin our paper by looking in depth at isotopic patterns in modern tibet we show that the 18 o value of surface waters decreases systematically up the himalayan front in central nepal by about 2 8 km in agreement with the patterns documented and modeled by previous research on the tibetan plateau itself there is no apparent correlation between elevation and the 18 o value of flowing surface waters both surface waters and soil carbonates display a northward increase in 18 o values of about 1 5 north of the himalayan crest even though elevation increases modestly the isotopic increase with latitude reduces the isotope elevation gradient for water in the northernmost plateau to 1 to 2 km carbonates in both soils and lakes form at higher temperatures than assumed by previous studies on the plateau temperature estimates from clumped isotope 47 analyses of modern soil carbonates significantly exceed mean annual air t and modeled maximum summer soil temperatures by 15 8 2 8 and 9 7 2 5 c respectively similarly elevated temperatures best account for the 18 o values observed in modern soil and lake carbonates we recalculated paleoelevations from previous studies on the plateau using both higher formation temperatures and latitude corrected isotopic values with one notable exception our revised model produces paleoelevation estimates very close to previous estimates the exception is the reconstruction from late eocene age deposits at xoh xil for which we calculate elevations that are higher and much closer to the current elevation than previously reconstructed therefore there is no evidence for northward progression through time of tibetan elevation change instead the available but admittedly very scanty evidence suggests that much of tibet attained its modern elevation by the mid eocene a truly robust test of the various geodynamic models of uplift await expansion and replication of isotopic records all across tibet especially in the center and north and for 15 ma

controls on the isotopic composition of surface water and precipitation in the northern andes colombian eastern cordillera abstract empirical datasets provide the constraints on the variability and causes of variability in stable isotope compositions d or 18 o of surface water and precipitation that are essential not only for models of modern and past climate but also for investigations of paleoelevation this study presents stable isotope data for 76 samples from four elevation transects and three iaea gnip stations in the eastern cordillera of colombia and the northern andean foreland these data are largely consistent with theories of stable isotope variability developed based on a global dataset on a monthly basis the precipitation amount effect exerts the dominant control on d p and 18 o p values at the iaea gnip stations at the bogota station 2547 m the d p and 18 o p values vary seasonally with isotopic minima correlating with maxima in precipitation amount although surface water samples from eastern cordilleran streams and rivers fall on the global meteoric water line samples from three of four lakes 2842 3459 m have evaporatively elevated d sw and 18 o sw values the iaea gnip station data averaged over multiple years combined with stream and river water data define vertical lapse rates of 1 8 km 1 for 18 o and 14 6 km 1 for d and are a close fit to a common thermodynamically based rayleigh distillation model elevation uncertainties for these relationships are also evaluated comparison of this colombian dataset with the elevation uncertainties generated by the thermodynamically based model shows that the model underestimates uncertainty at high 18 o and d values while overestimating it for low 18 o and d values this study presents an independent empirical assessment of stable isotope based elevation uncertainties for the northern andes based on a dataset of sufficient size to ensure statistical integrity these vertical lapse rates and associated uncertainties form the basis for stable isotope paleoelevation studies in the northern andes

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

is there any evidence of mega lake manly in the eastern mojave desert during oxygen isotope stage 5e 6 a comment on hooke r l 1999 lake manly shorelines in the eastern mojave desert california quaternary research52 328 336