uranium series ages of travertines and timing of the last glaciation in the northern yellowstone area wyoming montana uranium series age determinations by mass spectrometric methods were done for travertines and associated carbonate veins related to clastic deposits of the last glaciation pinedale in the northern yellowstone area dramatic variations in the hydrologic head are inferred from variations in the elevation of travertine deposition with time and are consistent with the expected hydrologic effects of glaciation we determine the following chronology of the pinedale glaciation with the key assumption that travertine deposits and associated carbonate veins perched high above present thermal springs were deposited when glaciers filled the valley below these perched deposits 1 the early pinedale outlet glacier advanced well downvalley between 47 000 and 34 000 yr b p 2 the outlet glacier receded to an interstadial position between 34 000 and 30 000 yr b p 3 an extensive pinedale ice advance occurred between 30 000 and 22 500 yr b p 4 a major recession occurred between 22 500 and 19 500 yr b p 5 a minor readvance deckard flats culminated after 19 500 yr b p and 6 recession from the deckard flats position was completed before 15 500 yr b p this chronology is consistent with the general trend of climatic changes in the northern hemisphere as revealed by recent high resolution ice core records from the greenland ice sheet

oxygen isotopes in iron iii oxides abstract quartz sio 2 and hematite fe 2 o 3 possess considerably different gram formula weights and different stoichiometric coefficients for their oxygen these differences mean that the numerical values of sio 2 and fe 2 o 3 compositions when reported as weight percent are not the same as the numerical values of x o i e oxygen in the mineral as a mole percent of the total oxygen in a binary quartz hematite system consequently end member quartz and hematite 18 o values which are determined from linear extrapolations of 18 o vs weight percent fe 2 o 3 data from binary mixtures can be in error by as much as several per mil extrapolation to end member 18 o values in binary quartz hematite systems should always be performed using mole fraction of oxygen as the compositional variable the hematite water fractionation curve of yapp and the quartz water curve of knauth and epstein were used together with the kinetic isotope exchange model of criss et al to constrain the depositional environment of the late proterozoic quartz hematite banded iron formation deposits of urucum brazil the depositional temperatures permitted by the model assumptions employed here range from 0 to 35 c or 54 c the permitted range of depositional water 18 o values is from 6 6 or 8 9 to 0 0 while the range of permitted depositional conditions is rather large it does encompass the possible cool temperatures and brackish or fresh waters which are indicated by sedimentologic evidence in these deposits

isotopic evidence of holocene climatic change in the san juan mountains colorado abstract the d of cellulose from 14c dated wood collected in the san juan mountains of southwestern colorado decreased by about 45 from 9600 to 3100 yr b p and an additional 25 to the present the wood samples are from trees that grew above present day tree line and reflect a time of warmer average summer temperatures these changes in d are interpreted to indicate a major change during the holocene in the sources of moisture in the seasonality of precipitation or in both

oxygen isotope records of goethite from ferricrete deposits indicate regionally varying holocene climate change in the rocky mountain region u s a oxygen isotopes of goethite from ferricrete deposits were measured from both northern and southern rocky mountain localities to assess geographic variability in regional holocene paleoclimate change a f3 7xincrease in oxygen isotope values of 14 c dated goethites in the northern rocky mountains suggests a regional scale relative increase in amounts of isotopically heavy summer precipitation since the early holocene in contrast oxygen isotope values from the southern rocky mountains increase abruptly f2 1xat f6200 14 c yr b p then decrease f2 4xbetween f2000 14 c yr b p and the present we interpret this period of relatively high y 18 o values as evidence for a middle holocene warm period combined with a relatively strong summer monsoon these variable climate records suggest that the rocky mountains of the western united states have had a spatially heterogeneous holocene climate history d 2003 university of washington all rights reserved

environmental memory and a possible seasonal bias in the stable isotope composition of u th he dated goethite from the canadian arctic abstract goethite ax 2 from axel heiberg island 80 n on the margin of the arctic ocean is the dominant mineral in a sample of petrified eocene wood but u th and he measurements suggest that the goethite feooh crystallized in the latest miocene pliocene ca 5 5 to 2 8 ma measured d and 18 o values of ax 2 are 221 6 and 9 6 0 5 respectively the inferred d and 18 o values of the ancient water were about 139 and 18 6 respectively with a calculated temperature of crystallization of 3 5 c which compares with the modern summer j j a temperature of 3 c and contrasts with a modern mat of 19 c published results from various biological proxies on nearby ellesmere island indicate a pliocene 4 ma mat of either 6 or 0 4 c and corresponding seasonal amplitudes of about 18 or 13 c a conductive heat flow model suggests that a temperature of 3 c could represent goethite crystallization at depths of 100 200 cm for mat 6 c or 250 450 cm for mat 0 4 c over seasonally restricted intervals of time the 18 o value of the ax 2 water 18 6 is more positive than the modern j j a precipitation 22 in combination the paleotemperatures and 18 o values of ancient waters from ax 2 and published results from three eocene or pliocene proxy sites on axel heiberg and ellesmere islands are consistent with a warm season bias in those isotopic proxies the results are also consistent with higher proportions of j j a precipitation in the annual total if so this emphasizes the importance of seasonality at high latitudes even in times of warmer global climates and suggests that the arctic hydrologic cycle as expressed in the seasonal distribution and isotopic composition of precipitation perhaps modified by a warmer arctic ocean differed from modern the 13 c value of the fe co 3 oh component in the ax 2 goethite is 6 6 which is much more positive than expected if crystallizing goethite incorporated co 2 derived primarily from oxidation of relict eocene wood with 13 c values of about 24 this apparent paradox may be resolved if the goethite is a product of oxidation of 13 c rich siderite which had previously replaced wood in an eocene methanogenic burial environment thus the goethite retains a carbon isotope memory of a diagenetic eocene event but a d and 18 o record of the latest miocene pliocene arctic climate

oxygen and hydrogen isotope variations among goethites α feooh and the determination of paleotemperatures abstract a plot of d vs 18o values from a diverse group of natural goethites defines a data array which is approximately parallel to the meteoric water line the 18o values range from 9 5 to 4 4 per mil while the corresponding d values vary from 202 to 94 per mil there is considerable scatter in the d vs 18o array which can be attributed primarily to different temperatures of mineral formation as determined previously yapp and pedley 1985 and confirmed in this study the goethite water d h fractionation factor is essentially independent of temperature over the range from 25 c to 145 c however the goethitewater 18 o 16 o fractionation factor does vary with temperature as indicated by initial goethite synthesis experiments conducted at 25 c 44 c and 62 c the synthetic goethite 18 g w values suggest that the natural goethites in this study formed at temperatures that may range from about 8 c to 66 c support for the validity of these approximate calculated temperatures is provided by a natural goethite sample from the atlantis ii deep in the red sea these results suggest that goethite can be used as a single mineral low temperature geothermometer perhaps more importantly goethite can be used in low temperature oxygen isotope mineral pair geothermometers such as chert goethite calcite goethite phosphate goethite etc

an assessment of isotopic equilibrium in goethites from a bog iron deposit and a lateritic regolith abstract hydrogen and oxygen isotope ratios have been measured in goethites from a lateritic regolith in the eastern amazon basin of brazil and a young bog iron deposit in new jersey usa the presence of exchangeable hydrogen and admixed minerals required the use of material balance calculations to determine relevant d and 18o values for the brazilian goethite d is 121 and 18o of 1 2 adjusted for al content these values yield a calculated temperature of formation of 24 3 c which is in good agreement with the modern average annual temperature in that locale goethite from the new jersey bog has a d of 134 and 18o of 0 9 its calculated temperature of formation 23 3 c resembles summer temperatures in southeastern new jersey bacterially mediated rates of precipitation of ferric hydroxide appear to be higher in the bog during the summer months crerar et al 1979 thus the temperature calculated for the new jersey goethite could indicate that the conversion of ferric hydroxide to goethite also occurs predominantly in the summer 13c values of the fe co3 oh component in goethite 21 7 for brazil and 19 3 for new jersey reflect the 13c values of the associated organic carbon 28 4 for brazil and 26 3 for the new jersey values of pco2 in the regolith 0 063 bar and bog 0 039 bar were calculated from the measured abundances of the fe co3 oh component the values of 13c and pco2 obtained from the goethites suggest that the ambient co2 in these systems originated primarily from oxidized organic matter in the low ph high pco2 waters characteristic of bogs and laterites isotopic equilibrium may be closely approached during the formation of goethite from ferric hydroxide ferrihydrite even if the initial precipitation of the ferric hydroxide precursor is bacterially mediated therefore meaningful paleotemperatures might commonly be calculated from stable isotope ratios of nonexchangeable oxygen and hydrogen in geothites from such environments

cool tropical temperatures shift the global δ18o t relationship an explanation for the ice core δ18o borehole thermometry conflict the discrepancy between central greenland borehole temperatures and the isotopic composition of last glacial maximum ice can be explained by a shift in the 5180 t relationship for the hydrological cycle linked to cooler tropical temperatures this concept is illustrated using a simple rayleigh distillation model an estimate for o a 5180 at lgm holocene of 0 37 o oc is determined with a simple graphical technique

intracrystalline site preference of oxygen isotopes in goethite a single mineral paleothermometer abstract the crystal structure of goethite feo oh has two distinct oxygen sites one with exclusively fe o bonds the other with bonds to both iron and hydrogen we developed a method to assess the oxygen isotope contrast between these sites by measuring both the bulk goethite and the oxygen released in the conversion of goethite to hematite the method involves collecting the water released by dehydroxylation fluorinating that population of extracted atoms and measuring the resulting oxygen isotope composition extracted o 18 then on a separate aliquot all structural oxygen is fluorinated and measured bulk o 18 using synthetic goethite precipitates grown under controlled environmental conditions we found significant temperature dependent fractionation e bulk extracted 5 51 0 26 10 6 t 2 44 5 2 8 t in kelvin this intracrystalline fractionation forms the basis of a single phase paleothermometer with an estimated uncertainty of 2 3 c the temperature dependence appears to be independent of the isotopic composition of the parent fluid from which the goethite formed and the ph of that fluid this intracrystalline thermometer can be used to simultaneously determine the formation temperature of a goethite and the isotopic composition of the water from which it formed natural goethites analyzed with this technique yield geologically reasonable formation temperatures of between 15 and 41 c

laser oxygen isotope analysis of weathering goethite from the lateritic profile of yaou french guiana paleoweathering and paleoclimatic implications abstract oxygen isotopic compositions of weathering goethite pseudomorphs after pyrite in the lateritic profile of yaou french guiana were measured by laser fluorination the laterite at yaou is composed of a 25 m thick saprolite overlain by a 3 m thick latosol petrographic observations indicate that the pseudomorphic replacement of pyrite by goethite occurs at or near the weathering front and is complete the goethite pseudomorphs are essentially devoid of al and are progressively dissolved and partially replaced by a microcrystalline plasma of kaolinite and goethite in the upper horizons latosol of the profile the laser technique used in this study permitted the determination of the 18 o value of individual grains of goethite and the investigation of grain to grain variation within a single sample horizon as well as vertical variation with depth in the latosol the goethite 18 o values range from 0 8 to 3 2 and exhibit significant grain to grain and vertical variation this most likely reflects undetected intragrain contamination with microcrystalline kaolinite in the saprolite the goethite 18 o values are consistent ranging from 1 0 to 1 8 between 3 and 18 m depth and from 2 5 to 3 3 between 23 m depth and the weathering front at 28 m oxygen isotope compositions of present groundwater soil water and rainfall at yaou were also measured and compared with calculated isotopic compositions for goethite forming waters goethite pseudomorphs in the lower part of the saprolite are in isotopic equilibrium with present groundwater indicating that they may be forming today or that they formed in the recent past under climatic conditions similar to present conditions in contrast goethite pseudomorphs found higher in the profile are not in isotopic equilibrium with present water but with a water depleted in 18 o by 1 50 relative to present groundwater it is suggested that these low 18 o pseudomorphs are probably older and formed under different paleoclimatic conditions at a time when climatic regimes were possibly more monsoonal than today this is in agreement with models of climatic evolution derived from pedological considerations the results of this study suggest that goethite pseudomorphs in ancient saprolites may preserve their original o isotopic composition acquired at the weathering front and may therefore be used as indicators of changes in weathering climatic conditions during the evolution of a profile

temperature and stable isotope variations in different water masses from the alboran sea western mediterranean between 250 and 150 ka 1 mg ca sr ca and stable isotope measurements have been performed on tests from the planktonic foraminifers globigerinoides ruber white globigerina bulloides and neogloboquadrina pachyderma right coiling in samples from ocean drilling program site 977a in the alboran sea western mediterranean the evolution of different water masses between 250 and 150 ka is described warm substages were characterized by strong seasonality and thermal stratification of the water column by contrast less pronounced seasonality and basin stratification seem to prevail during cold substages several periods of stratification due to the low salinity of the upper water mass occurred during the formation of organic rich layers and also during a possible heinrich like event at 220 ka the three foraminifer species studied show a common and large shell sr ca variability in short timescales suggesting changes in the global ocean sr ca ratio as one of the main causes of variations in shell composition

stability of holocene climate regimes in the yellowstone region abstract a 12 500 yr pollen record from loon lake wyoming provides information on the climate history of the southwestern margin of yellowstone national park the environmental reconstruction was used to evaluate hypotheses that address spatial variations in the holocene climate of mountainous regions loon lake lies within the summer dry winter wet climate regime an increase in xerophytic pollen taxa suggests drier than present conditions between ca 9500 and 5500 14 c yr b p this response is consistent with the hypothesis that increased summer radiation and the expansion of the east pacific subtropical high pressure system in the early holocene intensified summer drought at locations within the summer dry winter wet regime this climate history contrasts with that of nearby sites in the summer wet winter dry region which were under the influence of stronger summer monsoonal circulation in the early holocene the loon lake record implies that the location of contrasting climate regimes did not change in the yellowstone region during the holocene the amplitude of the regimes however was determined by the intensity of circulation features and these varied with temporal changes in the seasonal distribution of solar radiation

radiocarbon dated ferricrete provides a record of natural acid rock drainage and paleoclimatic changes ancient deposits of ferricrete stratified iron oxyhydroxide or clastic sediment cemented by stratified iron oxyhydroxide are present in headwater streams draining an historic mining district in the rocky mountains usa these deposits which form under conditions of low ph and high metal concentrations are present in streams draining many other mineralized areas radiocarbon dating of wood fragments entombed within the ferricrete indicates dates of deposition as old as 8840 50 years before present b p the ferricrete deposits provide evidence that natural metal rich acid rock drainage has been occurring in this mineralized region for thousands of years due to the weathering and oxidation of exposed or near surface massive sulfide ore deposits the dating and chemical composition of the ferricrete deposits have applications to the environmental remediation of historic mining sites and to environmental issues related to natural background chemistry in addition the radiocarbon dates of the ferricrete deposits correlate closely with warm wet periods in the holocene record showing that ferricrete deposits may represent a previously untapped source of paleoclimatic information

paleoenvironment and the oxygen isotope geochemistry of ironstone of the upper ordovician neda formation wisconsin usa geological evidence suggests that the goethite dominated oolitic ironstone of the upper ordovician neda formation in the north central united states was subaerially weathered in the late ordovician the oxygen isotope ratios of the goethites in the open quotes hard close quotes and open quotes soft close quotes ores of this deposit are rather uniform with a delta sup 18 o value of about minus 1 0 per thousand this delta sup 18 o value indicates the presence of meteoric water at the time of goethite formation and supports the idea that the goethites in hard and soft ores were formed in the same chemical weathering environment 440 million years ago the delta sup 18 o value of accessory phosphate in some soft ore goethite rich ooids was measured and combined with the goethite delta sup 18 o value to calculate a temperature of formation of about 23 degrees c the corresponding delta sup 18 o value of the ancient water was calculated to have been minus 7 3 per thousand the relatively open quotes cool close quotes temperature calculated for the low altitude tropical site occupied by the neda ironstone in the late ordovician is consistent with published evidence from fossil marine invertebrates for global cooling at that time the delta sup 18 o value of minus 7 3 per thousand for the ancient tropical precipitation could indicate intense rainfall ofmore a seasonal perhaps monsoonal character 27 refs 7 figs 3 tabs less

spatial variations of holocene climatic change in the yellowstone region abstract the paleoecologic record of the northern rocky mountains shows considerable spatial variability which has been difficult to explain as a unified response to large scale changes in effective moisture or temperature through time comparison of past and present climatic patterns suggests that the spatial heterogeneity in the fossil record arises from a local response to the effects of greater summer solar radiation during the early holocene solar radiation directly determines evapotranspiration and indirectly controls the strength of the summer monsoon and the eastern pacific subtropical high pressure system the yellowstone region provides an example of an area where the indirect effects of solar radiation are manifest by the juxtaposition of two contrasting climatic regimes today and where these regimes were amplified during the early holocene fossil pollen data suggest that central and southern yellowstone the summer dry area became drier in the early holocene while northern yellowstone the summer wet area became wetter the boundary between regimes however is controlled by topography and has not changed significantly in the holocene the spatial variations of holocene vegetation and climatic changes in the northern rocky mountains may therefore be explained as a trade off between strengthened monsoonal circulation and a stronger subtropical high in the early holocene and the relative importance of these precipitation regimes on a topographically complex landscape

unraveling weathering episodes in tertiary regoliths by kaolinite dating western ghats india abstract secondary minerals in soils can record climatic changes affecting continental surfaces over geological times their dating should refine our present knowledge about their potential periods of formation as well as their relations with the ongoing change of climate and erosion weathering regimes in the present study twenty kaolinite samples from two lateritic profiles of the karnataka plateau an intensively studied area in the southern india have been dated using electron paramagnetic resonance epr spectroscopy kaolinite ages vary between 0 229 0 24 ma to 40 73 15 37 ma four different groups of age can be identified with ages clustered around 1 0 3 5 9 0 and 39 0 ma these groups of age indicate local preferential weathering periods that coincide with distinct indian climatic events described in independent studies such as monsoon strengthening thus regional or subcontinental factors likely prevailed over global forcing in the imprint of climatic events in the regolith profiles these results confirm that despite their simple mineralogy laterites can contain several relictual and coexisting generations of secondary minerals and that epr dating of kaolinite contributes to unraveling the complex history of continental surfaces over geological periods

chemical weathering and lithologic controls of water chemistry in a high elevation river system clark s fork of the yellowstone river wyoming and montana seasonal analyses of surface water geochemistry were conducted in the clark s fork of the yellowstone watershed to determine whole rock weathering rates the clark s fork of the yellowstone is a high elevation catchment with distinct bedrock lithologies using dissolved solute concentrations and stream flow data we calculated cation denudation rates of 119 g m 2 yr 1 65 900 eq ha 1 yr 1 for carbonate rich sedimentary rocks 16 6 g m 2 yr 1 8200 eq ha 1 yr 1 for andesitic volcanics and 9 8 g m 2 yr 1 5300 eq ha 1 yr 1 for granitic gneisses ca na ratios indicate that chemical weathering of disseminated calcite in granitic rocks contributes to the total solute load in these subcatchments removal of this c 2100 eq ha 1 yr 1

isotopic evidence for holocene climate change in the northern rockies from a goethite rich ferricrete chronosequence abstract climate proxy records often show regional heterogeneity due to the complex interplay of large scale atmospheric circulation patterns and local topographic features this is especially prevalent in the mountainous regions of the western united states where the interaction of two seasonally distinct weather systems can result in locally abrupt climate boundaries here we establish oxygen isotope ratios of goethite from ferricrete chronosequences formed by natural acid rock drainage as a new source of spatially small scale holocene climate information systematic study of these deposits may prove useful in understanding regional variations in response to global holocene climate change oxygen isotope ratios of goethites from the mountainous northeastern yellowstone region show an increase of 3 over the past 9000 years we attribute this isotopic change to a local increase of isotopically heavier summer precipitation since the early holocene possibly augmented by seasonal temperature differences brought on by orbitally forced insolation changes over the past 9000 years our interpretation is compatible with palynology studies as well as holocene climate simulations which indicate a decrease in monsoon intensity from 9000 years b p to the present unlike the southwestern united states this change may have resulted in wetter summers in our study area

isotopic evidence for shifts in atmospheric circulation patterns during the late quaternary in mid north america wyoming is now at the eastern margin of westerlies originating in the pacific but in the pleistocene appears to have received moisture from elsewhere possibly the gulf of mexico oxygen isotope ratios of pedogenic carbonate in postglacial terraces correspond to ratios in equilibrium with present meteoric waters which show a strong relation to precipitation seasonality and storm sources in contrast the oxygen isotope ratios of all pre holocene soils are significantly more positive even though the carbon isotope composition of coexisting organic matter suggests that the carbonate formed in temperatures cooler than today the oxygen isotope ratios of paleowaters in mid north america appear to be more useful for identifying past storm sources than for estimating paleotemperatures

fire and alluvial chronology in yellowstone national park climatic and intrinsic controls on holocene geomorphic processes we employed a systemwide approach a large and robust set of radiocarbon ages and modern process analogs to interpret the holocene history of forest fire related sedimentation and overall alluvial activity in northeastern yellowstone national park debris flow and flood events following the 1988 fires provided facies models for interpreting the stratigraphic record of fire related sedimentation within valley side alluvial fans of soda butte creek fire related deposits make up approximately 30 of the late holocene fan alluvium fifty 14 c ages on fire related events cluster within the intervals of 3300 2900 2600 2400 2200 1800 and 1400 800 yr b p and suggest earlier episodes of large fires and fan aggradation around 7500 5500 and 4600 4000 yr b p a major pulse of fire related debris flow activity between 950 and 800 yr b p coincided with the height of the widely recognized medieval warm period ca a d 1050 1200 instrumental climate records over the last 100 yr in yellowstone imply that the intensity and interannual variability of summer precipitation are greater during warmer periods enhancing the potential for severe short term drought major forest fires and storm generated fan deposition along lower soda butte creek fill cut terrace treads were created by lateral migration of channels and accumulation of overbank sediments ca 8000 yr b p terrace level t1a 7000 5600 t1b 3100 2600 t2 2000 1300 t3 and post 800 yr b p t4 these periods coincide with overbank sedimentation on slough creek and the lamar river but alternate with intervals of fire related fan deposition implying a strong climatic control local paleoclimatic data suggest cooler effectively wetter conditions during terrace tread formation in warmer drier intervals reduced average runoff in axial streams results in meander belt narrowing concurrent channel incision may be caused by infrequent large floods greater resistance to downcutting however allowed fewer terraces to be formed along slough creek and the lamar river alluvial systems in northeastern yellowstone show a clear response to millennial scale climatic cycles wherein alluvial fans aggrade and prograde over flood plains in drier periods axial streams widen their flood plains and trim back the fans during wetter periods small scale climatic fluctuations of the holocene thus had substantial impact on postglacial landscapes in northeastern yellowstone

simulation of the climate of 18 000 years bp results for the north american north atlantic european sector and comparison with the geologic record of north america abstract the large ice sheets in north america and europe and the extensive sea ice cover in the north atlantic at the time of the last glacial maximum must have greatly modified the surface temperature patterns and in turn the location and intensity of the surface winds and jet streams a general circulation model was used to simulate the january and july patterns of temperature precipitation and wind for 18 ka bp boundary conditions for the model consisting of ice sheet location and height sea ice location and sea surface temperature were prescribed from climap 1981 the model results are illustrated and described for the north american north atlantic european sector the jet stream splits around the north american ice sheet and the southern branch strengthens considerably compared to present over the southern portion of the united states the sea ice margin of the north atlantic and the southern edge of the european ice sheet geologic evidence principally from north america of wind temperature and moisture conditions is assessed from sand dune and loess records estimates of snowline depression pollen records and lake level studies the geologic evidence is generally compatible with the model simulation