oxygen and hydrogen isotope ratios in tree rings how well do models predict observed values we have measured annual oxygen and hydrogen isotope ratios in the cellulose of the latewood of oak quercus robur l growing on well drained ground in norfolk uk we compare the observed values of isotope ratios with those calculated using equations that allow for isotopic fractionation during the transfer of oxygen and hydrogen from source water taken by the tree to cellulose laid down in the cambium the equations constitute a model in which isotopic fractionation occurs during evaporative enrichment within the leaf and during isotopic change between carbohydrates and water in the trunk during cellulose synthesis from the relationship between isotope ratios in precipitation and cellulose we deduce that the source water used by the tree comprises a constant mixture of groundwater and precipitation chiefly from the months of may june and july of the growth year by selection of isotopic fractionation factors and the degree of isotope exchange within the trunk we are able to model the observed annual values of oxygen isotope ratios of cellulose to a significant level r 0 77 p 0 01 when we apply the same model to hydrogen isotope ratios however we find that although we can predict the average value over the time series we can no longer predict the year to year variation we suggest that this loss of environmental signal in the hydrogen isotopes is caused by differences in the kinetic isotope effects of the biochemical reactions involved in the fixation of hydrogen in different positions of the glucose molecule owing to these effects the hydrogen isotope ratios of cellulose can vary in a way not anticipated in current models and hence may induce non climatic noise in the hydrogen isotope time series

textures of syntaxial quartz veins synthesized by hydrothermal experiments syntaxial quartz veins were synthesized by hydrothermal flow through experiments using rock blocks metachert sandstone and granite containing slits based on analyses of vein textures using birefringence imaging microscopy we identified two stages of crystal growth during stage 1 quartz grain growth occurs without an increase in grain width during stage 2 quartz grains develop facets and grow preferentially parallel to the c axis orientation and the aspect ratio of quartz grains shifts toward 2 9 competitive growth occurs significantly at stage 2 and the transition from stage 1 2 occurs at a critical distance from the vein wall being approximately equal to the host rock grain size crystal growth in the slits produce various textures controlled by the ratio of slit aperture h to host rock grain size d in high h d cracks elongate blocky texture develops by grain impingement during stage 2 whereas in low h d cracks crystals that bridge the crack form without competitive growth by grain impingement at stage 1 heterogeneous structures of fracture porosity are produced during syntaxial vein formation due to the anisotropy in the growth rate of quartz such incompletely sealed cracks may act as important fluid pathways and as weak planes in the upper crust

model evaluation for reconstructing the oxygen isotopic composition in precipitation from tree ring cellulose over the last century the oxygen isotope composition of tree rings is controlled by many factors including temperature amount of precipitation and changes in relative humidity in this study we present a modified leaf water model from dongmann et al radiation and environmental biophysics 11 1974 41 that can be used to calculate the isotopic composition of the source water and thus of precipitation that a tree used during the growing season the calibration of the model was accomplished by comparing a previously measured oxygen isotope tree ring chronology from central switzerland with the swiss network for isotopes in the hydrologic cycle station at bern from 1971 to 1995 and integrating temperature relative humidity data and ring width in particular our efforts focused on understanding the significance of the dampening factor f which we relate to changes in humidity and its variability over both the calibration period 1971 to 1995 and the study period 1913 to 1995 our results indicate that f ranging between 0 27 to 0 49 is variable based on correlation with relative humidity average daily temperature and ring width index using this model we have constructed a record of the oxygen isotope composition of precipitation during the growing season may through september for the last century in central western europe this approach can be potentially used in other locations where isotopic and meteorological data are available to extend records of the isotopic composition of precipitation back in time beyond observational records

climate variability in the early pliocene arctic annually resolved evidence from stable isotope values of sub fossil wood ellesmere island canada abstract tree ring analyses have contributed significantly to investigations of past climate stable isotope climate proxies 18o d and 13c values enhance traditional ring width data although poor preservation of ancient wood has tended to limit development of stable isotope proxy records to the holocene and the late pleistocene here we apply stable isotope techniques to wood that represent the remains of mixed coniferous boreal vegetation preserved in early pliocene 4 5 ma deposits at strathcona fiord ellesmere island canada ca 78 n four well preserved tree trunks identified through wood anatomical characteristics as larix larch from this high arctic site provide annually resolved sequences of up to 250 years from which we developed a high resolution record of pliocene climate stable oxygen isotope values in conjunction with ring width measurements were used to derive annually resolved temperature records for this site our ring width and isotope based reconstructions provide an annually resolved record up to 250 years of temperature and indicate growing season jj temperatures 15 8 5 0 c 11 8 5 1 c and mean annual temperatures mat 1 4 4 0 c 18 3 4 1 c warmer than present estimated isotope values of precipitation of 16 3 2 18o and 150 1 8 9 d were calculated from the isotopic values of wood cellulose relative humidity estimated from both 13c and d records ranged from 60 to 80 paleotemperature source water and humidity estimates are comparable to those of a modern boreal forest growing ca 15 20 south of modern ellesmere island

complex fringes around magnetite porphyroclasts growth and deformation history abstract deformed strain fringes in iron formation rocks show complex quartz fiber patterns that grew alongside magnetite porphyroclasts embedded in a matrix of quartz and iron oxides during coaxial to non coaxial deformation these rocks have been deformed by a combination of processes involving microfracturing pressure solution and dislocation glide at temperatures of approximately 300 c detailed microstructural observation and crystallographic analysis show that quartz fiber growth is not controlled by the crystal faces quartz c axis orientations of fibrous quartz indicate that these grains initially grew with their c axes parallel to the fiber length late solid state deformation of crystallized fibers comprised dislocation glide along basal plane and subsequent recrystallization this produces aggregates of recrystallized grains consisting of equant to elongated quartz grains with straight and orthogonal grain boundaries

annual climate variability in the holocene interpreting the message of ancient trees abstract over vast areas of the world s landmasses where climate beats out a strong seasonal rhythm tree growth keeps unerring time in their rings trees record many climate melodies played in different places and different eras recent years have seen a consolidation and expansion of tree ring sample collections across the traditional research areas of north america and europe and the start of major developments in many new areas of eurasia south america and australasia from such collections are produced networks of precisely dated chronologies records of various aspects of tree growth registered continuously year by year across many centuries their sensitivities to different climate parameters are now translated into ever more detailed histories of temperature and moisture variability across expanding dimensions of time and space with their extensive coverage high temporal resolution and rigid dating control dendroclimatic reconstructions contribute significantly to our knowledge of late holocene climates most importantly on timescales ranging from 1 to 100 years in special areas of the world where trees live for thousands of years or where subfossil remnants of long dead specimens are preserved work building chronologies covering many millennia continues apace very recently trees have provided important new information about major modes of general circulation dynamics linked to the el nino southern oscillation and the north atlantic oscillation and about the effect of large volcanic eruptions as for assessing the significance of 20th century global warming the evidence from dendroclimatology in general supports the notion that the last 100 years have been unusually warm at least within a context of the last two millennia however this evidence should not be considered equivocal the activities of humans may well be impacting on the natural growth of trees in different ways making the task of isolating a clear climate message subtly difficult

identifying bias in cold season temperature reconstructions by beetle mutual climatic range methods in the pliocene canadian high arctic abstract well preserved beetle elytra from the fossil and subfossil record are used by palaeoclimatologists to estimate past temperatures beetle derived estimates of temperature across the pliocene arctic are consistently lower than those derived from other palaeoclimate proxies here we test if that pattern is attributable to either the modern dataset or specific mutual climatic range method mcrm we used a global dataset of observations global biodiversity information facility for modern beetles as opposed to a north american regional dataset and a consistent mcrm for comparison to vegetation derived estimates termed cracle climate reconstruction analysis using coexistence likelihood estimation rather than different mcrm methods for each analysis beetle derived estimates from one site beaver pond are consistently much lower than the vegetation derived estimates stable isotope results from flora and fauna and summer temperatures from bacterial tetraethers the reanalysis of beetle data produced a small reduction in proxy estimate mismatch overall we found good agreement among proxy estimates of maximum temperature of the warmest month for two of the three sites in the canadian arctic but increasingly poorer agreement for warmest quarter coldest quarter and minimum temperature of the coldest month this pattern may be due to beetles avoidance mechanisms and a climate space different from modern calibration sets during the pliocene beetle derived temperature estimates especially cold season should be interpreted with caution when reconstructing palaeoclimates

determination of fabric and strain ellipsoids from measured sectional ellipses implementation and applications abstract geologists examine fabrics to constrain models of formation or of deformation of rocks and it is often convenient to summarise the results by a fabric ellipsoid as fabric data are commonly collected on planar sections through the rock estimating a fabric ellipsoid from sectional ellipses often with arbitrary orientations is an important task an algebraic method to calculate such an ellipsoid presented in an earlier paper has been implemented with the program ellipsoid it is used here on examples that illustrate questions and issues that arise when collecting selecting and processing sectional fabric data and when assessing the results the quality of fit of the ellipsoid to the data is assessed in all cases examples include a case in which the average sizes of markers on individual sections can be used in the determination of the ellipsoid and other cases in which such sizes are not useful a case in which sectional ellipses are not obtained from closed markers and a case in which data scatter and insufficient coverage of section orientations lead to a hyperboloid instead of an ellipsoid

a global synthesis of the marine and terrestrial evidence for glaciation during the pliocene epoch abstract the pliocene climate is globally warm and characterised by high atmospheric carbon dioxide concentrations yet the terrestrial and marine scientific communities have gathered considerable evidence for substantial glaciation events in both the northern and southern hemisphere prior to the quaternary evidence on land is fragmentary but marine records of glaciation present a more complete history of pliocene glaciation here we present a global compilation of the terrestrial and marine glacial evidence for the pliocene and demonstrate four glaciation events that can be identified in the southern and or northern hemisphere prior to the latest pliocene intensification of northern hemisphere glaciation there are two globally recognisable glacial events in the early pliocene c 4 9 4 8 ma and c 4 0 ma one event around the early late pliocene transition c 3 6 ma and one event during marine isotope stage m2 c 3 3 ma long term climate cooling decreasing carbon dioxide concentrations in the atmosphere and high climate sensitivity in the pliocene probably facilitated each glaciation event however the mechanisms behind the early pliocene glacial events are unclear the global glaciation at c 3 3 ma may be caused by changes in ocean gateways whereas the decline in carbon dioxide concentrations is important for the latest pliocene intensification of northern hemisphere glaciation

kinematics and significance of a poly deformed crustal scale shear zone in central to south eastern madagascar the itremo ikalamavony thrust across the crystalline basement of madagascar late archaean rocks of the antananarivo block are tectonically overlain by proterozoic predominantly metasedimentary units of the ikalamavony and itremo groups of the southwest madagascar block the generally west dipping tectonic contact can be traced for more than 750 km from nw to se and is referred to here as the itremo ikalamavony thrust the basal units of the sw madagascar block comprise metasedimentary quartzites with the potential to preserve a multistage deformation history in their microstructures previous studies suggest contrasting structural evolutions for this contact including eastward thrusting top to the west directed extension and right lateral strike slip deformation during the late neoproterozoic ediacaran in this study we integrate remote sensing analyses structural and petrological fieldwork as well as microstructural investigations of predominantly quartz mylonites from the central southern segment of the contact between ankaramena and maropaika in this area two major phases of ductile deformation under high grade metamorphic conditions occurred in latest neoproterozoic early phanerozoic times a first andreaba phase produces a penetrative foliation which is parallel to the contact between the two blocks and contemporaneous with widespread magmatism a second ihosy phase of deformation folds andreaba related structures the investigated micro structures indicate that a juxtaposition of both blocks possibly already occurred prior to the andreaba phase b re activation with top to the east thrusting took place during the latest stages of the andreaba phase c the ihosy phase resulted in regional scale open folding of the tectonic contact and d reactivation of parts of the contact took place at distinctively lower temperatures post dating the major ductile deformations

magma flow inferred from preferred orientations of plagioclase of the rio ceara mirim dyke swarm ne brazil and its ams significance

pliocene and early pleistocene paleoenvironmental conditions in the pannonian basin hungary slovakia stable isotope analyses of fossil proboscidean and perissodactyl teeth abstract stable carbon and oxygen isotope values of structural carbonate 13c 18oco3 and phosphate 18opo4 in bio apatite were measured for fossil mammalian teeth from slovakia and hungary oxygen isotope compositions of enamel provide new quantitative records of the pliocene and early pleistocene paleoclimate in the pannonian basin pb the 18opo4 values were used to study the temporal variations in the oxygen isotope compositions of precipitation and the changes in temperature over the pb the new o isotope data suggest that surface air temperatures between 4 5 and 2 0 ma were 1 to 4 c warmer with about 700 mm yr more precipitation compared to the present c isotope analyses of samples from proboscideans anancus sp mammut sp and perissodactyls stephanorhinus sp tapirus sp from the pliocene mn15 mn16 and early pleistocene mn17 suggest that they were primarily c3 browsers the mean 13c value is high at 4 5 to 3 7 ma mn14 15 during the pliocene warm period and decreases at about 3 5 to 3 0 ma mn16 mid pliocene warm period with the onset of more humid conditions in europe the 13c values return to higher values from 2 5 ma onwards mn17 most likely reflecting more arid conditions as a consequence of the onset of the northern hemisphere glaciation

orthogonal microscopy image acquisition analysis technique for rock sections in polarizer angle domain abstract the microscopic identification of rock sections is one of the most basic research methods of petromineralogy which is important to the research of mineral composition pore throat characteristics interstitial filling etc the traditional manual identification method was time consuming and also burdened with errors due to the subjective nature of human judgment which can bring some uncertainties to the further results therefore this paper proposes a technique for image acquisition and analysis of rock sections based on sequential images of rock sections in angle domain under polarizing microscope the analysis includes the following three steps firstly based on the multi angles extinction feature of rock section the direction adaptive correlation coefficient method was used to characterize the edge of the rock sections and segment the rock grains a series of parameters including grain size roundness convexity flatness and roughness were also extracted to characterize the morphological features of rock grains quantitatively secondly the variation characteristics of multi channel parameters rgb and gray channel with angle domain were analyzed for different minerals and then the mineral composition was accurately identified on the basis of grain segmentation the pore structures including intergranular pores dissolved pores and throat were extracted and the parameters of pore structure were also obtained finally the distribution of the interstitials was characterized based on the change of the extinction characteristics of the interstitials in the pores image analysis technique based on rock sections with polarizing microscope provides an effective and convenient method for grain segmentation mineral composition classification pore identification and interstitial analysis

a cold supergene zinc deposit in alaska the reef ridge case the reef ridge deposit is a typical supergene nonsulfide zinc mineralization located in the yukon koyukuk region of west central alaska usa it is hosted in sedimentary rocks of the farewell terrane a continental fragment sandwiched between the siberian and laurentian cratons during the early paleozoic the mineralization occurs in lower middle devonian shallow water dolomite of a paleozoic carbonate platform succession belonging to the nixon fork tectonic unit the mineralization consists of oxidized minerals associated with minor remaining sulfides pyrite marcasite and sphalerite in the oxidation zone smithsonite is the predominant mineral mixed with fe hydr oxides goethite and hematite a complete petrographic and mineralogical study was performed samples were analyzed by x ray diffraction inductively coupled plasma mass spectrometry and emission spectrometry energy dispersive scanning electron microscopy and qemscan quantitative evaluation of minerals by scanning electron microscopy the most abundant mineral in the nonsulfide ore is smithsonite similar to other nonsulfide zn deposits worldwide the first generation of smithsonite has replaced both primary sphalerite and the host carbonates a second smithsonite generation precipitated as cement in vugs cavities and fractures minor zinc amounts also occur in the fe hydr oxides and zinc traces have been identified in clay minerals the carbon and oxygen isotope values of smithsonite at reef ridge vary from 0 7 to 2 1 relative to vienna peedee belemnite vpdb and 19 1 to 21 9 relative to vienna standard mean ocean water vsmow the 13 c values are similar to those of the host rock suggesting that the predominant carbon source for smithsonite was the host carbonates with only a limited contribution from organic carbon the oxygen isotope ratios of reef ridge smithsonite are more depleted in 18 o compared to supergene nonsulfides from other parts of the world formed under warm humid temperate or semiarid climates the oxygen isotope fractionation between water and smithsonite which relates the 18 o value of the mineralizing solution the formation temperature of smithsonite and its 18 o composition indicates that the 18 o composition of reef ridge smithsonite is related to very low formation temperatures 10 c and strong depletion in 18 o of the precipitating waters the 18 o smithsonite composition the strong 18 o depletion and the relationship of the formation of the reef ridge nonsulfide deposit with the development of the sleetmute upland surface which started in the late tertiary and continues to the present indicate that the formation of the reef ridge nonsulfide deposit is probably related to cold humid weathering episodes during a period comprised between late tertiary and holocene the traditional interpretation on the genesis of zn nonsulfide deposits in warm humid temperate or semiarid conditions should be questioned where other climate zones are indicated

isotopic composition δ13c δ18o in wood and cellulose of siberian larch trees for early medieval and recent periods 1 we related tree ring width trw and isotopic composition 13c 18o of wood and cellulose from four larch trees larixcajanderi mayr to climate parameters the material was sampled in northeastern yakutia 70 n 148 e for the recent ad 1880 2004 and early medieval ad 900 1000 periods during the recent period june july and august air temperatures were positively correlated with 13c and 18o of wood and cellulose while july precipitation was negatively correlated furthermore the vapor pressure deficit vpd of july and august was significantly correlated with 13c of wood and cellulose but vpd had almost no influence on 18o comparative analyses between mean isotope values for the ad 900 1000 and ad 1880 2004 periods indicate similar ranges of climatic conditions with the exception of the period ad 1950 2004 while isotopic ratios in cellulose are reliably related to climatic variables during some periods those in whole wood showed even stronger relationships strong positive correlations between 18o of cellulose and greenland ice core gisp2 data were detected for the beginning of the medieval period r 0 86 p 0 05 indicating the reliability of isotope signals in tree rings for large scale reconstructions

a contourite drift system on the baffin bay west greenland margin linking pliocene arctic warming to poleward ocean circulation terrestrial records from the canadian arctic archipelago indicate that a temperate and moist climate prevailed during the pliocene i e before the intensification of northern hemisphere glaciations but the controlling factors causing these conditions remains elusive here we present marine seismic reflection evidence of contiguous kilometer scale sedimentary drifts or contourites buried below the west greenland shelf which relates high latitude pliocene warmth to intense geostrophic currents along the eastern baffin bay margin seismic to borehole correlation indicates that enhanced current induced deposition began during the middle miocene ca 17 15 ma and terminated during the late pliocene onset of global cooling the transition from along slope sediment transport to trough mouth fan progradation designates the onset of greenland ice sheet glaciers advancing across the continental shelf and coincides with increasing iceberg productivity in baffin bay and the nordic seas from 3 3 to 2 7 ma our results suggest that the baffin bay west greenland margin formed a late neogene passageway for persistent ocean boundary currents and we infer that the pliocene high latitude warmth was to a significant extent caused or enhanced by advection of subtropical heat and moisture to the arctic regions attenuation of the poleward heat flux conveyed by the paleo current system may have been critical for allowing glacial buildup in the canadian arctic and northern greenland during the late pliocene we further surmise that vertical tectonic adjustments of the continental margin played a role in this attenuation which eventually caused the demise of meridional ocean circulation through baffin bay

modeling of middle pliocene climate with the ncar genesis general circulation model abstract a climate modeling study was carried out which used boundary conditions created by the usgs prism group the model used for this study is the national center for atmospheric research ncar genesis climate model genesis is an atmospheric general circulation model gcm that is coupled to a land surface model and contains submodels for snow and soil boundary conditions incorporated into the model which were specific to the middle pliocene 3 ma are 1 present day continent configuration modified by a 35 m rise in sea level 2 modified present day elevations 3 reduced continental ice cover on both greenland and antarctica 4 pliocene vegetation and 5 pliocene sea surface temperatures ssts and sea ice distribution atmospheric pco 2 and orbital parameters were set at current values the greatest influence of the specified warm ssts upon the resulting climate was occurrence of warmer and more humid high latitudes than observed in the current climate especially in the winter season the global mean surface temperature was 3 6 c warmer than in a present day control case and global mean precipitation increased by 5 relative to the control case with most excess precipitation occurring over the african continent and the oceans zonal winds weakened slightly in the pliocene case but hadley cell extent and jet stream locations were unchanged relative to the control case model results predict specific areas in which middle pliocene climate should have differed substantially from the present climate which can be tested with paleoclimate data

environment and paleoecology of a 12 ka mid north american younger dryas forest chronicled in tree rings abstract until now availability of wood from the younger dryas abrupt cooling event yde in n america ca 12 9 to 11 6 ka has been insufficient to develop high resolution chronologies for refining our understanding of yde conditions here we present a multi proxy tree ring chronology ring widths events evidenced by microanatomy and macro features stable isotopes from a buried black spruce forest in the great lakes area liverpool east site spanning 116 yr at ca 12 000 cal yr bp during this largely cold and wet period the proxies convey a coherent and precise forest history including frost events tilting drowning and burial in estuarine sands as the laurentide ice sheet deteriorated in the middle of the period a short mild interval appears to have launched the final and largest episode of tree recruitment ultimately the tops of the trees were sheared off after death perhaps by wind driven ice floes culminating an interval of rising water and sediment deposition around the base of the trees although relative influences of the continental ice sheet and local effects from ancestral lake michigan are indeterminate the tree ring proxies provide important insight into environment and ecology of a n american yde boreal forest stand

stability of climate signal in carbon and oxygen isotope records and ring width from scots pine pinus sylvestris l in finland four hundred year long records of carbon and oxygen stable isotope ratios and ring width were measured from scots pine pinus sylvestris l from sites in northern and eastern finland responses of isotope ratios to temperature and precipitation were analysed for the 20th century carbon isotope ratios responded strongly to summer temperature at both sites whereas an influence of precipitation on the record was observed only at the site in eastern finland oxygen isotope ratios were less responsive to climatic variation than carbon at the high frequency level to shed light on the role of the possible divergence problem during last decades the climate responses were studied separately in the first and in the second half of the 20th century the responses to temperature were stable in the north but in eastern finland the significant period of summer occurred earlier during the later half of the century relationships between records were studied during the 400 a period all proxies correlated positively with each other although temporal changes occurred common forcing discovered in northern finland between carbon isotope and ring width records was weaker in the earlier period studied three climate reconstructions were created temperature reconstruction for northern finland and temperature and precipitation reconstructions for eastern finland copyright 2009 john wiley sons ltd

performance and applications of an automated c axis ice fabric analyzer a completely automated instrument for ice fabric analysis has been built tested and applied the analysis of a thin section is performed in two steps first the section is loaded into the machine and is automatically imaged in about 16 min then at a later time and convenient location the grains in the section are identified from a stored image either automatically or by the user and the c axis orientation of each grain is calculated at a rate of 1200 grains h 1 comparison of automated results with manual rigsby stage results shows excellent agreement diagnostics indicate that the accuracy of the new technique is 0 5 in the c axis orientation two specific applications are demonstrated 1 the ability to measure internal grain orientations that may reveal internal stress and 2 the ability to measure very thin thin sections the latter combined with the ability to zoom in on small regions of section will be useful for examining the fabric of fine grained 1 mm size grains ice

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

stratospheric modulation of the boreal response to pliocene tropical pacific sea surface temperatures variations in the sea surface temperature of the eastern equatorial pacific usually associated with the el nino southern oscillation have a global impact previous work has shown that the stratosphere modulates the northern hemisphere response to these temperature anomalies here we show that the stratosphere also plays a major role in modulating the response to tropical sea surface temperature anomalies representative of the mean state of the pliocene era approximately four million years ago key to the response is a predominance of sudden stratospheric warmings during boreal winter which cause a large anomalous surface pressure response over the north atlantic ocean the stratospheric modulation results in relatively cold winter spring eurasian surface temperatures and relatively warm surface temperatures in greenland and north america the implications of these results for simulating and understanding the climate of the pliocene era are discussed

13c 18o isotope signatures and clumped isotope thermometry in foraminifera and coccoliths accurate constraints on past ocean temperatures and compositions are critical for documenting climate change and resolving its causes most proxies for temperature are not thermodynamically based appear to be subject to biological processes require regional calibrations and or are influenced by fluid composition as a result their interpretation becomes uncertain when they are applied in settings not necessarily resembling those in which they were empirically calibrated independent proxies for past temperature could provide an important means of testing and or expanding on existing reconstructions here we report measurements of abundances of stable isotopologues of calcitic and aragonitic benthic and planktic foraminifera and coccoliths relate those abundances to independently estimated growth temperatures and discuss the possible scope of equilibrium and kinetic isotope effects the proportions of 13c 18o bonds in these samples exhibits a temperature dependence that is generally similar to that previously been reported for inorganic calcite and other biologically precipitated carbonate containing minerals apatite from fish reptile and mammal teeth calcitic brachiopods and molluscs aragonitic coral and mollusks most species that exhibit non equilibrium 18o 16o 18o and 13c 12c 13c ratios are characterized by 13c 18o bond abundances that are similar to inorganic calcite and are generally indistinguishable from apparent equilibrium with possible exceptions among benthic foraminiferal samples from the arctic ocean where temperatures are near freezing observed isotope ratios in biogenic carbonates can be explained if carbonate minerals generally preserve a state of ordering that reflects the extent of isotopic equilibration of the dissolved inorganic carbon species

modelling pliocene warmth contribution of atmosphere oceans and cryosphere the relative role of the atmosphere oceans and cryosphere in contributing towards middle pliocene warmth ca 3 ma bp is investigated using the hadcm3 coupled ocean atmosphere general circulation model the model was initialised with boundary conditions from the usgs prism2 data set and a pliocene atmospheric co2 level of 400 ppmv and run for 300 simulated years the simulation resulted in a global surface temperature warming of 3degreesc compared to present day in contrast to earlier modelling experiments for the pliocene surface temperatures warmed in most areas including the tropics 1 5degreesc compared with present day the model predicts a general pattern of ocean warming 1 5degreesc in both hemispheres to a depth of 2000 m below which no significant differences are noted sea ice coverage is massively reduced up to 90 the flow of the gulf stream north atlantic drift is up to 100 mm s 1 greater in the pliocene case analysis of the model predicted meridional streamfunction suggests a global pattern of reduced outflow of antarctic bottom water aabw up to 5 sv a shallower depth for north atlantic deep water formation and weaker thermohaline circulation 3 sv the decrease in aabw occurs mainly in the pacific rather than atlantic ocean model diagnostics for heat transports indicate that neither the oceans nor the atmosphere are transporting significantly more heat in the pliocene scenario rather these results indicate that the major contributing mechanism to global pliocene warmth was the reduced extent of high latitude terrestrial ice sheets 50 reduction on greenland 33 reduction on antarctica and sea ice cover resulting in a strong ice albedo feedback these results highlight the need for further studies designed to improve our knowledge regarding pliocene terrestrial ice configurations

glaciation of north america in the james bay lowland canada 3 5 ma glaciers expanded in the northern hemisphere during the middle pliocene however whether they extended into the midlatitude lowlands remains unknown a pliocene sequence from a buried deep bedrock trench in the midlatitude james bay lowland canada 52 49 5 n 83 52 5 w contains a till and an overlying lacustrine deposit rich in fossil pollen magneto stratigraphy together with pollen derived biostratigraphy constrains it to a time span from 3 6 to 3 0 ma based on multiple lines of evidence we are able to prove the deposition of the till by an early ice sheet and hence glaciation of the lowland at ca 3 5 ma 3 6 3 4 ma after glaciation rapid warming permitted thermophilic trees now exotic to this area to grow which include oak sweetgum and cypress furthermore pollen analysis indicates alternating carolinian deciduous and boreal evergreen forests under a climate that oscillated and cooled gradually during a prolonged postglacial period from 3 5 to 3 0 ma

humidity estimate for the middle eocene arctic rain forest the exquisite preservation of fossilized metasequoia trees that grew near 808n latitude during the middle eocene ca 45 ma in nunavut canada allowed for dd and d 18 o analyses of cellulose techniques previously restricted to wood 30 000 yr old from the isotopic results we determined that the middle eocene arctic atmosphere contained 23 the water found in the region s atmosphere today this water vapor contributed to a middle eocene greenhouse effect that insulated the polar region during dark polar winters

deformation mechanisms in second phase affected microstructures and their energy balance based on the relationship zener parameter z second phase size second phase volume fraction vs calcite grain size dg second phase controlled aggregates and microstructures that are weakly affected by second phases are discriminated the latter are characterized by large but constant grain sizes high calcite grain boundary fractions and crystallographic preferred orientations cpo while calcite grain size and calcite grain boundary fraction decrease continuously and cpo weakens with decreasing z in second phase controlled microstructures these observations suggest that second phase controlled microstructures predominantly deform via granular flow because pinning of calcite grain boundaries reduces the efficiency of dynamic recrystallization favoring mass transfer processes and grain boundary sliding in contrast the balance of grain size reduction and growth by dynamic recrystallization maintains a steady state grain size in microstructures that are only weakly affected by second phases promoting a predominance of dislocation creep with increasing temperature the relationship between z and dg persists but the calcite grain size increases continuously based on microstructures the energy of each modifying process is calculated and its relative contribution is compared with energies of the competing processes surface energy dragging energy dynamic recrystallization energy the steady state microstructures result from a temperature dependent energy minimization procedure of the system

spatial and temporal oxygen isotope trends at the northern tree line in eurasia 1 the oxygen isotope ratio of ice cores and sea sediments is an extremely useful source of information on long term climatic changes a similar approach has been applied to the oxygen isotope ratio of tree rings to enable a pattern based reconstruction of the isotope variations on the continents we present an oxygen isotope map for northern eurasia spanning from norway to siberia that reflects the isotope distribution in the late 19th century and compare it with an equivalent map for the present day situation the average isotope values of 130 trees show a large east to west gradient and are highly correlated with the isotope distribution of precipitation surprisingly the 18o 16o ratio of the wood has been decreasing in the interior of the continent since the late 19th century in contrast to the strong temperature increase recorded by meteorological data from this isotope trend over time a change in the seasonality of precipitation can be inferred

annually resolved temperature reconstructions from a late pliocene early pleistocene polar forest on bylot island canada abstract here we use 18o ratios measured in tree rings of crossdated sub fossil wood to reconstruct an annually resolved record of temperature and 18o of meteoric water for an interglacial late pliocene early pleistocene fossil forest found on bylot island nunavut canada our record represents the first crossdated record of pliocene wood mean annual temperatures determined in this study average 3 4 3 8 c which is 11 4 4 4 c warmer than present day bylot island 14 8 2 2 c june july temperatures average 13 5 1 1 c approximately 12 6 1 6 c warmer than present day meteoric water 18o values average 15 5 2 9 2 6 more enriched than present values of precipitation 18o our temperatures are comparable to mid pliocene modeled temperatures for the arctic 3 5 c warmer than present suggesting that interglacial warm periods in the late pliocene early pleistocene may have been as warm as the mid pliocene warm period that both the bylot island forest deposit and the kap kobenhavn deposit represent the remains of northern tree line vegetation that lived during warm interglacial periods within the overall cool plio pleistocene suggests that forest deposits in the arctic capture a snapshot of interglacial conditions during the plio pleistocene rather than the average pliocene climate and may not be suitable records to study pliocene cooling

tree ring growth curves as sources of climatic information abstract regional growth curves rgcs have been recently used to provide a new basis for removing nonclimatic trend from tree ring data here we propose a different use for rgcs and explore their properties along two transects one meridional and the other elevational rgcs consisting of mean ring width plotted against cambial age were developed for larch samples from 34 sites along a meridional transect 55 72 n in central siberia and for 24 sites on an elevational gradient 1120 and 2350 m a s l in tuva and neighboring mongolia at approximately 51 n there are systematic gradients of the parameters of the rgcs such as i 0 maximum tree ring width near pith and i min the asymptotic value of tree ring width in old trees they are smaller at higher latitude and elevation annual mean temperature and mean may september temperature are highly correlated with latitude here and hence rgc parameters are correlated with these climatic variables correlations with precipitation are more complex and contradictory between meridional and elevational transects the presence of a similar gradient in the elevational transect is consistent with temperature being the causal factor for both gradients rather than for example latitude dependent patterns of seasonal photoperiod change taking ring measurements from collections of relict and subfossil wood the rgc latitude and rgc temperature relationships are used to estimate paleo temperatures on centennial time scales these estimates are consistent with earlier traditional dendroclimatic approaches and with independent information on the northern extent of forest growth in the early mid holocene it may be possible to use this same approach to make estimates of century scale paleo temperatures in other regions where abundant relict wood is present

petrology of upper amphibolite facies marbles from the east humboldt range nevada usa evidence for high temperature retrograde hydrous volatile fluxes at mid crustal levels

arctic north american seasonal temperatures from the latest miocene to the early pleistocene based on mutual climatic range analysis of fossil beetle assemblages late tertiary and early quaternary fossil beds in the arctic regions of north america have yielded abundant well preserved remains of plants and arthropods documenting the existence of coniferous forests in the high arctic latitudes nearly all of the beetle coleoptera specimens in these fossil assemblages represent extant species we have applied the mutual climatic range mcr method of paleotemperature analysis to fossil beetle assemblages from 11 sites to estimate mean summer t max and winter t min temperatures we found that arctic t min values during the latest miocene and pliocene were substantially warmer than they are today the mcr estimates therefore support the scenario derived from the paleobotanical data namely that arctic pliocene climates were far less continental several pliocene age assemblages from the high arctic yielded t max estimates 9 10 c warmer than modern values at the sites this is the same degree of warming required to allow coniferous forests to grow in the high arctic by 3 million years bp a cooling trend is marked in the paleobotanical and fossil beetle evidence from alaska all assemblages dating between 5 7 and 2 million years bp yielded calibrated t max values between 12 4 and 13 8 c regardless of location thus the insect fossil data support the theory that there was far less latitudinal gradation in temperatures during the late pliocene than there is today our reconstructions suggest regional climatic cooling especially winter temperatures began by at least 2 million years bp

late paleocene arctic coastal climate inferred from molluscan stable and radiogenic isotope ratios abstract characterizing polar climates during past warm intervals is important for understanding greenhouse climate dynamics because high latitude surface temperatures and precipitation patterns are extremely sensitive to global climatic conditions model data comparisons of high latitude climates during past warm intervals cretaceous eocene pliocene are currently at odds specifically simulations of past warm climates produce polar regions characterized by sub freezing temperatures and significant seasonality whereas limited fossil proxy data indicate higher mean annual temperatures and low seasonality i e an equable climate we have constructed a data set to infer northern hemisphere polar marine temperatures during the late paleocene seasonal and mean annual temperature and the oxygen isotopic composition of precipitation are reconstructed for an arctic coastal setting during the thanetian 57 58 ma using fossil shell stable isotope profiles we estimate that coastal water temperatures varied between 10 and 15 c during the seasons of growth presumably spring summer and fall these findings support paleontological evidence implying northern hemisphere polar climates were seasonally warm during the late paleocene in addition estuarine fossil oxygen isotope profiles show periodic excursions to low values as low as 19 vpdb which indicate seasonal pulses of isotopically depleted freshwater

estimates of arctic land surface temperatures during the early pliocene from two novel proxies during the pliocene 2 6 to 5 ma ago atmospheric co 2 levels have been estimated as similar to or slightly above present levels tripati et al 2009 pagani et al 2010 and yet earth s climate was considerably different recent evidence suggests that although global temperatures were 2 3 c warmer than pre industrial arctic warming may have been amplified during the pliocene thus precise temperature records of this interval are required to assess the sensitivity of earth s climate to persistent levels of co 2 between 365 and 415 ppm we present records of two independent proxies for terrestrial growing season temperatures at the early pliocene beaver pond site on ellesmere island 18 o values of cellulose from well preserved peat constrain the 18 o values of meteoric water to 20 7 0 3 which we combined with 18 ovalues of aragonitic freshwater molluscs found within the peat in order to calculate mollusc growth temperatures this approach results in an average growing season temperature of 14 2 1 3 c temperatures were independently derived by applying carbonate clumped isotope thermometry to mollusc shells from the same site indicating an average growing season temperature of 10 2 1 4 c a one way anova indicates that the differences between the two techniques are not significant as the difference in mean temperatures between both methods is no different than the difference between individual shells using a single technique both techniques indicate temperatures 11 16 c warmer than present may sept temperature 1 6 1 3 c and represent the first thermodynamic proxy results for early pliocene ellesmere island

the environmental water of the middle eocene arctic evidence from δd δ18o and δ13c within specific compounds abstract the extensive vertical exposure 150 m of terrestrial sediments on axel heiberg island which contain thick fossiliferous lignites presents an exceptional opportunity to follow the establishment and re establishment of arctic metasequoia forests during the middle eocene we compared d values in n alkanes of chain length 23 25 27 and 29 with 18 o values in phenylglucosazone p g derived from cellulose we also analyzed abundance of ferns gymnosperms and angiosperms using pollen and spores isolated from each lignite our results showed that forest composition was altered upon uplift as gymnosperms became more abundant within the relatively well drained upland sediments this was also reflected in the small 1 but significant increase in the 13 c value of tom from lowland to upland environments however neither the d values of n alkanes nor the 18 o in p g were statistically different in the upland sediments as compared to the lowland sediments from this we inferred that the oxygen isotope signature of environmental water available to the forests for plant growth was relatively uniform throughout the time of the fossil forests the d value of environmental water implied by both n alkanes and p g ranged from 168 to 131 and was considerably enriched compared to all environmental water samples available from the modern arctic region

oxygen isotope ratios in fossil wood cellulose isotopic composition of eocene to holocene aged cellulose abstract we measured the 18 o of cellulose 18 o cel extracted from fossil wood collected at 9 sites in the northern and southern hemispheres as a potential source of information about precipitation 18 o 18 o ppt in the past and paleotemperatures the samples had been buried in fluvial sediments for periods of time ranging from ca 45 million to 250 years at the oldest localities high latitude eocene through pliocene age sites in canada and russia mean annual temperature mat estimates derived from the modern relationship between mat and 18 o cel are 6 16 c lower than the mat estimates derived from other biological proxies estimates of pleistocene and holocene mean annual temperatures are close to the modern values at those sites these results are consistent with other recent findings that the mat 18 o ppt relationship across north america was not constant throughout the cenozoic paleo 18 o ppt estimates derived from fossil cellulose and the modern north american relationship between 18 o cel and 18 o ppt are within the current annual range of 18 o ppt values at all locations the middle eocene 18 o ppt we determined from arctic cellulose samples 21 9 is consistent with river water 18 o determined in two other studies 19 1 to 22 these findings provide some evidence that a precipitation 18 o signal may be retained in wood cellulose during millions of years of burial and that latitudinal patterns in 18 o ppt may not have changed much during the past 45 ma these interpretations depend of course on the assumption that the isotopic composition of the cellulose has not changed during burial an assumption for which it is difficult to gather direct evidence xrd analysis shows that the crystalline form of the fossil cellulose we used to estimate paleoprecipitation 18 o and paleo mat is the same as that of modern cellulose and that the samples are free of quartz and iron oxide contaminants that result in negative errors in measured 18 o cel

an experimental setup for the analysis of analogue deformation experiments using the rotating polariser stage a new experimental setup for the analysis of deformation of rock analogues is presented the hardware component consists of a rotating polariser stage and the software component includes several specialised pieces of software during experiments the software is able to construct data sets in the form of specialised images that contain information on grain shape and crystallographic orientations several different types of movies with frames spaced as close as 2 min apart can be created during the experiment which convey crystallographic and shape information in a semi continuous form this setup can be adapted to a variety of optical deformation rigs

oxygen isotope ratios of oak in east england implications for reconstructing the isotopic composition of precipitation annual latewood 18o values from oak quercus robur l are presented for the period 1895 1994 for four trees growing in eastern england we demonstrate using the 18o values of precipitation from wallingford 1982 1994 and the longer time series from groningen 1965 1994 that the 18o values of winter precipitation had the strongest influence on the 18o values of tree ring cellulose the influence of winter precipitation on the spring summer formed latewood may be explained by several factors most soil water is replenished during the winter water may take several months to penetrate the unsaturated zone and oaks may sample water from lower in the profile during times of water stress the 18o values of oak latewood cellulose were also significantly p 0 01 correlated with summer relative humidity therefore although precipitation 18o values may be altered by partial isotopic exchange with xylem water and the influence of stomatal conductance upon evapotranspiration some of the original 18o signature remains

fluid assisted grain boundary sliding in bedding parallel quartz veins deformed under greenschist metamophic grade abstract iron formation rocks of quadrilatero ferrifero brazil were deformed at greenschist facies quartz grains in bedding parallel veins were sheared and deformed by a combination of mechanisms assisted by aqueous fluids veins in the outcrop appear to be stretched parallel to the compositional layering the overall vein shapes resemble those of boundinage and pinch and swell in thin sections veins show microstructures similar to those observed in hand samples where domains of large quartz crystals are pulled apart for several millimeters the voids between quartz fragments are filled with domains of polycrystalline quartz the microstructural and orientation data show that the strain imposed on the vein as a rigid and competent layer was not accommodated in the quartz polycrystals exclusively by crystal plastic deformation or dynamic recrystallization the new grains are strain free with straight boundaries and with weak to random crystallographic fabrics we interpret these features to have resulted from a combination of processes which included grain boundary sliding accomplished by solution transfer we propose that the coeval operation of both mechanisms allows the aggregate to deform at higher strain rates without necking of the vein layer in a type of flow similar to those described in superplastic regimes

pliocene arctic temperature constraints from the growth rings and isotopic composition of fossil larch instrumental records reveal that the current rate of arctic warming greatly exceeds mean global warming however arctic temperatures during the pliocene were considerably warmer than present making it an excellent time period for investigating potential consequences of current warming trends here we focus on an early pliocene 4 to 5 ma peat deposit from ellesmere island characterized by a remarkable fossil assemblage representative of a modern boreal forest among the fossils are wellpreserved samples of an extinct larch larix groenlandii which were exploited as an archive of paleoclimatic information we reconstruct pliocene terrestrial temperatures in the high arctic using a novel approach that combines measurements of ring width and oxygen isotopes this technique was calibrated by analyzing modern analog larch growing at the northern extent of their range and accounting for biotic fractionation of oxygen isotopes using a global database of modern trees based on this approach we estimated mean annual temperature in the arctic during the pliocene to be 5 5 1 9 c indicating that arctic temperatures were 14 2 c warmer than today this more precise multi proxy estimate is slightly warmer than previous estimates derived from empirical evidence and general circulation models our results also demonstrate that the biotic fractionation of oxygen isotopes in cellulose is non linear and dependent upon regional factors affecting aridity such as latitude and elevation therefore the simultaneous measurement of oxygen isotopes and morphological characteristics in paleovegetation can be useful in constraining climatic variables of earth s past

twentieth century trends in tree ring stable isotopes δ13c and δ18o of larix sibirica under dry conditions in the forest steppe in siberia 1 tree ring width density and ratio of stable isotopes 13c 12c and 18o 16o in wood and cellulose were determined for larch larix sibirica ledeb growing under water deficit conditions in the forest steppe zone in central siberia 54 24 n 89 57 e for the period 1850 2005 dendroclimatic analysis of the chronologies indicated precipitation to be the most important factor determining indicated parameters precipitation of june is significantly correlated with tree ring width and maximum density r 0 36 and 0 43 p 0 05 respectively relations of 13c and 18o to precipitation are similar but the most important month is july r 0 47 p 0 05 for 13c r 0 29 p 0 05 for 18o further 18o is positively related to the mean temperatures of july r 0 30 p 0 05 carbon and oxygen isotope ratios in wood and cellulose showed strong negative trends for the last 100 years the reason for this decrease could be the observed shift of the beginning of the vegetation period to earlier dates up to 1 week in spring and the increased use of precipitation water stored in the soil from october of the previous year although other explanations cannot be excluded in particular the physiological effect of increasing atmospheric co2 also responsible for lower 13c values thus an earlier start of the vegetation period could lead to tree ring formation during a period with higher water availability resulting in stronger isotopic fractionation and 13c depletion also reflected in a higher earlywood to latewood ratio at the same time highly 18o depleted water from october precipitation of the previous year is absorbed the incorporation of this isotopically lighter water during photosynthesis is reflected in the wood and cellulose of tree rings

modeling the influence of a reduced equator to pole sea surface temperature gradient on the distribution of water isotopes in the early middle eocene proxy based climate reconstructions suggest the existence of a strongly reduced equator to pole temperature gradient during the azolla interval in the early middle eocene compared to modern changes in the hydrological cycle as a consequence of a reduced temperature gradient are expected to be reflected in the isotopic composition of precipitation d 18o the interpretation of water isotopic records to quantitatively reconstruct past precipitation patterns is however hampered by a lack of detailed information on changes in their spatial and temporal distribution using the isotope enabled version of the national center for atmospheric research ncar atmospheric general circulation model community atmosphere model v 3 isocam3 relationships between water isotopes and past climates can be simulated here we examine the influence of an imposed reduced meridional sea surface temperature gradient on the spatial distribution of precipitation and its isotopic composition in an early middle eocene setting as a result of the applied forcings the eocene simulation predicts the occurrence of less depleted high latitude precipitation with d values ranging only between 0 and 140 compared to present day 0 to 300 comparison with early middle eocene age isotopic proxy data shows that the simulation accurately captures the main features of the spatial distribution of the isotopic composition of early middle eocene precipitation over land in conjunction with the aspects of the modeled early middle eocene climate hence the included stable isotope module quantitatively supports the existence of a reduced meridional temperature gradient during this interval

on the causes of 18 o depletion and 18 o 16 o homogenization during regional metamorphism the east humboldt range core complex nevada previous stable isotope studies at lizzies basin revealed that metasedimentary rocks are 18o depleted relative to protolith values particularly in the lower parts of the section lower zone where the rocks are also isotopically homogeneous on a scale of hundreds of meters quartz 18o 9 0 to 9 6 per mil in contrast metasedimentary rocks at higher levels at lizzies basin upper zone are less 18o depleted and more heterogeneous in 18o in order to understand more fully the isotopic evolution of this terrane a series of detailed meter scale traverses across various metamorphic and igneous lithologies were completed at lizzies basin and at the structurally higher angel lake locality traverses in the lizzies basin lower zone and in the lower parts of angel lake angel lake lower sequence across various silicate lithologies including abundant granitoids reveal similar degrees of homogeneity although the average 18o values are higher at angel lake in contrast traverses which include substantial thicknesses of marble and calc silicate gneiss and very little granitoid have more heterogeneous quartz 18o values 11 9 to 13 4 per mil and also have a higher average 18o 12 9 per mil than observed elsewhere the scale of 18o 16o homogeneity in quartz observed at lizzies basin and angel lake meters to hundreds of meters requires fluid mediated isotope exchange which accompanied tertiary metamorphism there is a correlation between the degree of 18o depletion in metasedimentary rocks 18o 16o homogenization between lithologies and the proportion of granitoids leucogranites in particular within any part of the section and a corresponding anticor relation with the proportion of marble this points to a causal relationship whereby the leucogranites as well as the tertiary hornblende diorite and biotite monzogranite acted as both a relatively low 18o reservoir and a source of fluids to enhance exchange while the marbles hindered isotope deplction and homogenization by acting as relatively high 18o reservoirs and impermeable layers material balance calculations help delineate the plausible mechanisms of exchange between granitoids and metasediments single pass infiltration of magmatic fluids from the granitoids is not capable of reproducing all of the observations fluidmediated exchange by convective recirculation of magmatic fluids on a scale of meters is the mechanism which explains all of the observations the generalized model for the isotopic evolution of the east humboldt range core complex provides and excellent opportunity to establish the main causes and controlling factors of 18o depletion and 18o 16o homogenization during regional metamorphism

dating and palaeoenvironmental reconstruction of the sediments around the miocene pliocene boundary in yermak plateau odp hole 911a using marine palynology abstract the late neogene evolution of the arctic to subarctic region is poorly understood due to few available records and poor age control at the margin of the arctic ocean yermak plateau ocean drilling program odp hole 911a is strategically located for establishing a stratigraphic framework for the arctic here we present dinoflagellate cyst and acritarch data from 24 stratigraphic levels in the lower part 474 26 505 64 metres below the seafloor of odp hole 911a the marine palynomorphs indicate a latest miocene to earliest pliocene age between 5 8 and 5 0 ma for the base of the hole based on the co occurrence of the dinoflagellate cyst barssidinium evangelineae and acritarch lavradosphaera crista our age estimate can possibly be further refined to 5 0 5 33 ma based on the presence of achomosphaera andalousiensis suttonensis which apparently has a range restricted to the pliocene an age close to the miocene pliocene boundary agrees with the planktonic foraminifer data together with recently available magnetostratigraphic data the base of the hole is likely to be placed at 5 2 ma this new chronostratigraphy is a first step towards a better understanding of the late neogene palaeoenvironment for the yermak plateau and also for the wider arctic to the subarctic region the terrestrial and fresh water palynomorphs were most likely redistributed and or displaced from the shelf towards deeper parts of the basin during contourite deposition under the influence of the west spitsbergen current the in situ marine dinoflagellate cyst assemblage contains a mixture of cool water and thermophilic taxa indicating sea ice free cool temperate and warmer than present conditions at the yermak plateau rivers were likely the source for the freshwater influence warmer than present conditions may have occurred due to northward warm water transport via the west spitsbergen current but also the absence of sea ice and consequent lower albedo could have played a role

late cenozoic deep weathering patterns on the fennoscandian shield in northern finland a window on ice sheet bed conditions at the onset of northern hemisphere glaciation abstract the nature of the regolith that existed on the shields of the northern hemisphere at the onset of ice sheet glaciation is poorly constrained in this paper we provide the first detailed account of an exceptionally preserved deeply weathered late neogene landscape in the ice sheet divide zone in northern finland we mine data sets of drilling and pitting records gathered by the geological survey of finland to reconstruct regional preglacial deep weathering patterns within a gis framework using a large geochemical data set we give standardised descriptions of saprolite geochemistry using a variant of the weathering index of parker wip as a proxy to assess the intensity of weathering we also focus on mineral prospects and mines with dense pit and borehole data coverage in order to identify links between geology topography and weathering geology is closely linked to topography on the preglacial shield landscape of northern finland and both factors influence weathering patterns upstanding resistant granulite granite gabbro metabasalt and quartzite rocks were associated with fresh rock outcrops including tors or with thin fines values above 3000 and 4000 beneath valley floors developed along mineralised shear and fracture zones weathering penetrated locally to depths of 50 m and included intensely weathered kaolinitic clays with wip fines values below 1000 late neogene weathering profiles were varied in character tripartite clay gruss saprock profiles occur only in limited areas bipartite gruss saprock profiles were widespread with saprock thicknesses of 10 m weathering profiles included two discontinuities in texture materials and resistance to erosion between saprolite and saprock and between saprock and rock limited core recovery when drilling below the soil base in mixed rocks of the tana belt indicates that weathering locally penetrated deep below upper fresh rock layers such deep seated weathered bands in rock represent a third set of discontinuities incipient weathering and supergene mineralisation also extended to depths of 100 m in mineralised fracture zones the thin weathering crusts found extensively beneath till may represent types of early or middle pleistocene palaeosols we confirm that glacial erosion has been very limited

extraction of α cellulose from mummified wood for stable isotopic analysis abstract stable isotope ratios of carbon 13c and oxygen 18o from tree ring cellulose can provide valuable paleoclimatic information at annual and subannual resolution from time periods long before instrumental climate records recently mummified non permineralized wood was discovered within canadian subarctic kimberlites inviting paleoclimatic investigations of the time in which the trees grew in the mummified wood polysaccharides hemicellulose cellulose are frequently preferentially degraded in the low silica anaerobic burial environment of the kimberlites resulting in a lignin rich material however some samples from the ekati panda kimberlite pipe ca 53 3 ma contain remnant cellulose demonstrating the extraordinary preservation potential of kimberlites preservation of cellulose is important because it allows for the construction of stable isotopic proxy records of deep time paleoclimates at annual to subannual resolution established cellulose extraction methods i e using a 17 5 sodium hydroxide naoh solution were unsuitable for this material because all holocelluloses were dissolved therefore we tested variants of two cellulose extraction methods i e brendel et al 2000 and jayme wise leavitt and danzer 1993 loader et al 1997 to optimize a procedure for extraction of a consistent yield of mummified wood cellulose for stable isotopic analysis stable carbon 13c and oxygen 18o isotopes were measured from cellulose from each extraction method as well as extractive free wood and unextracted mummified wood vitrinite reflectance used to assess thermal alteration of the unextracted material to estimate post burial temperatures within the kimberlite suggested low post burial peak temperatures tpeak 60 c we detected no mineral contaminants i e iron oxides in the material using energy dispersive x ray spectroscopy edx despite low cellulose yield

paleoclimatic implications of the relationship between oxygen isotope ratios of moss cellulose and source water in wetlands of lake superior abstract groundwater dominated wetlands contain abundant peat deposits but few studies have addressed the potential of using the oxygen isotopic composition 18 o of fen peat cellulose to evaluate past changes in climate here we investigated the relationship between 18 o values of pond water and those of moss cellulose from species inhabiting different micro environments in three different swales near lake superior united states isotope results over two growing seasons indicate a negligible effect of evaporation on the studied fens and the strong control of groundwater on the isotopic composition of swale water isotopic values for groundwater show a small seasonal variability and their low values suggest the influence of snowmelt our results show a consistent offset of 27 1 between average swale water 18 o and cellulose 18 o values for hollow sphagnum species reflecting the fractionation associated with cellulose biosynthesis when sphagnum species from hummocks are included the offset shows a larger variability 27 3 pointing to evaporative effects affecting hummock species this evaporative effect is more pronounced in emerged mosses which show the largest difference 30 relative to their source water the smaller variability associated with hollow species points to the possibility of performing species specific analyses from peat cellulose for improved paleoclimatic reconstructions

fluid rock history of granulite facies humite marbles from ambasamudram southern india an extensive humite bearing marble horizon within a supracrustal sequence at ambasamudram southern india was studied using petrological and stable isotopic techniques to define its metamorphic history and fluid characteristics at peak metamorphic temperatures of 775 73 c based on calcite graphite carbon isotope thermometry the mineral assemblages suggest layer by layer control of fluid compositions clinohumite calcite bearing assemblages suggest xco2 0 9 at 790 c and local wollastonite scapolite grossular bearing zones formed at xco2 of c 0 3 retrograde reaction textures such as scapolite quartz symplectites after feldspar and calcite and replacement of dolomite diopside or tremolite dolomite after calcite forsterite or calcite clinohumite are indicative of retrogression under high xco2 conditions calcite preserves late proterozoic carbon and oxygen isotopic signatures and the marble lacks evidence for extensive retrograde fluid infiltration while during prograde metamorphism the possible infiltration of aqueous fluids did not produce significant isotopic resetting isotopic zonation of calcite and graphite grains was likely produced by localized co2 fluid infiltration during retrogression contrary to the widespread occurrence of humite marbles related to retrograde aqueous fluid infiltration the ambasamudram humite marbles record a prograde to peak metamorphic humite formation and retrogression under conditions of low xh2o

clumped isotope geochemistry the study of naturally occurring multiply substituted isotopologues clumped isotope geochemistry is concerned with the state of ordering of rare isotopes in natural materials that is it examines the extent to which rare isotopes d 13 c 15 n 18 o etc bond with or near each other rather than with the sea of light isotopes in which they swim abundances of isotopic clumps in natural materials are influenced by a wide variety of factors in most cases their concentrations approach within ca 1 relative the amount expected for a random distribution of isotopes deviations from this stochastic distribution result from enhanced thermodynamic stability of heavy isotope clumps slower kinetics of reactions requiring the breakage of bonds between heavy isotopes the mass dependence of diffusive and thermo gravitational fractionations mixing between components that differ from one another in bulk isotopic composition biochemical and photochemical fractionations that may reflect combinations of these simpler physical mechanisms and in some cases other processes we do not yet understand although clumped isotope geochemistry is a young field several seemingly promising applications have already emerged most importantly it appears that proportions of 13 c 18 o bonds in carbonate minerals are sensitive to their growth temperatures independent of bulk isotopic composition thus clumped isotope analysis of ancient carbonates can be used as a quantitative paleothermometer that requires no assumptions about the 18 o of waters from which carbonates grew this approach has been used to reconstruct marine temperatures across the phanerozoic reaching back to the silurian terrestrial ground temperatures across the cenozoic thermal histories of aqueously altered meteorites among other applications clumped isotope geochemistry is also placing new constraints on the atmospheric budget and stratospheric photochemistry of co 2 and should be capable of placing analogous new constraints on the budgets of other atmospheric gases finally this field could be extended to encompass sulfates volatile hydrocarbons organic moieties and other materials

two and three dimensional shape fabric analysis by the intercept method in grey levels the count intercept is a robust method for the numerical analysis of fabrics launeau and robin 1996 it counts the number of intersections between a set of parallel scan lines and a mineral phase which must be identified on a digital image however the method is only sensitive to boundaries and therefore supposes the user has some knowledge about their significance the aim of this paper is to show that a proper grey level detection of boundaries along scan lines is sufficient to calculate the two dimensional anisotropy of grain or crystal distributions without any particular image processing populations of grains and crystals usually display elliptical anisotropies in rocks when confirmed by the intercept analysis a combination of a minimum of 3 mean length intercept roses taken on 3 more or less perpendicular sections allows the calculation of 3 dimensional ellipsoids and the determination of their standard deviation with direction and intensity in 3 dimensions as well the feasibility of this quick method is attested by numerous examples on theoretical objects deformed by active and passive deformation on bse images of synthetic magma flow on drawing or direct analysis of thin section pictures of sandstones and on digital images of granites directly taken and measured in the field

cross bedded woody debris from a pliocene forested river system in the high arctic beaufort formation meighen island canada abstract cross bedding the inclined internal stratification that records the migration of certain transverse sedimentary bedforms is nearly ubiquitous in current transported bedload sediments although examples of the structure are known from inorganic clastic sediments and sedimentary rocks from practically all depositional environments and intervals of geologic history here we report cross bedded lenses that are composed wholly or significantly of woody debris in pliocene alluvium of the beaufort formation in the canadian high arctic the uniqueness of cross bedded woody debris has hitherto been overlooked but we demonstrate that in the entire phanerozoic record it is apparently restricted to alluvium deposited during a warm climatic interval that permitted the growth of boreal type forests within 10 latitude of the north pole the marked spatiotemporal restriction of cross bedded woody debris implies that there may be environmental factors unique to polar forests which promote the subaqueous transport of large amounts of fine woody debris as fluvial bedload we propose a non uniformitarian conceptual model for the formation of cross bedded woody debris in forested polar rivers whereby an exceptional abundance of woody debris could accumulate and become saturated and denser than water due to reduced decomposition on forest floors that were subject to prolonged periods of darkness and subzero temperatures

crustal structure in the elko carlin region nevada during eocene gold mineralization ruby east humboldt metamorphic core complex as a guide to the deep crust the deep crustal rocks exposed in the ruby east humboldt metamorphic core complex northeastern nevada provide a guide for reconstructing eocene crustal structure 50 km to the west near the carlin trend of gold deposits the deep crustal rocks in the footwall of a west dipping normal sense shear system may have underlain the pinon and adobe ranges about 50 km to the west before tertiary extension close to or under part of the carlin trend eocene lakes formed on the hanging wall of the fault system during an early phase of extension and may have been linked to a fluid reservoir for hydrothermal circulation the magnitude and timing of paleogene extension remain indistinct but dikes and tilt axes in the upper crust indicate that spreading was east west to northwest southeast perpendicular to a paleozoic and mesozoic orogen that the spreading overprinted high geothermal gradients associated with eocene or older crustal thinning may have contributed to hydrothermal circulation in the upper crust late eocene eruptions upper crustal dike intrusion and gold mineralization approximately coincided temporally with deep intrusion of eocene sills of granite and quartz diorite and shallower intrusion of the harrison pass pluton into the core complex rocks stacked mesozoic nappes of metamorphosed paleozoic and precambrian rocks in the core complex lay at least 13 to 20 km deep in eocene time on the basis of geobarometry studies in the northern part of the complex the presently exposed rocks had been even deeper in the late mesozoic to 30 km depths before losing part of their cover by eocene time nappes in the core plunge northward beneath the originally thicker mesozoic tectonic cover in the north part of the core complex mesozoic nappes and tectonic wedging likely occupied the thickened midlevel crustal section between the deep crustal core complex intrusions and nappes and the overlying upper crust these structures as well as the subsequent large displacement cenozoic extensional faulting and flow in the deep crust would be expected to blur the expression of any regional structural roots that could correlate with mineral belts structural mismatch of the mineralized upper crust and the tectonically complex middle crust suggests that the carlin trend relates not to subjacent deeply penetrating rooted structures but to favorable upper crustal host rocks aligned within a relatively coherent regional block of upper crust

fluid rock interaction and thermal evolution during thrusting of an alpine metamorphic complex tinos island greece this study examines the fluid rock interaction and thermal evolution along a thrust that juxtaposes calcite rich marbles of high p t metamorphic unit of the attic cycladic massif greece on top of a lower grade dolomite marble unit the tertiary thrust represents a major phase of tectonic movement related to the decompression of the alpine orogen in the hellenides the stable isotope signatures of the thrust plane and adjacent sections of the footwall and hanging wall rocks are characterized by significant carbon and oxygen isotope depletions the depletion is most pronounced in calcite but is almost entirely missing in coexisting dolomite the isotopic patterns in the thrust zone can be explained by the infiltration of an externally derived water rich h2o co2 ch4 fluid x c x co 2 x ch 4 0 05 at water rock ratios on the order of 0 1 to 0 5 by weight the fluid induced calcite recrystallization is viewed as an important rheological control during thrusting the temperature evolution of the footwall hanging wall and mylonitic tectonic contact was determined by calcite dolomite solvus thermometry histograms of calcite dolomite temperatures are interpreted as indicating a heating of the footwall dolomite marble during the thrusting of the hotter upper plate conversely the hanging wall marble unit was cooled during the thrusting the calcite dolomite thermometry of the thrust plane gives temperatures intermediate between the initial temperatures of the lower and upper marble units and this leads to the conclusion that conductive heat transfer rather than fluid infiltration controlled the thermal evolution during thrusting

an illustration of the advantages of a complete texture analysis described by the orientation distribution function odf using quartz pole figure data abstract the preferred orientation of eight crystal directions of quartz was measured with an x ray texture goniometer for selected quartz bearing tectonites with a clear pattern of c axis preferred orientation the advantages of data analysis by means of calculations of the orientation distribution function and other forms of data presentation derived from the odf are demonstrated

variations of 18o 16o in plants from temperate peat bogs switzerland implications for paleoclimatic studies despite the great potential of peat bogs as climatic archives to date only few studies have focused on the climatic controls on cellulose isotopic composition in modern bog plants this study attempts to calibrate plant climate relationships by sampling a set of modern plant species both vascular plants and mosses and bog surface waters along an altitude transect in switzerland isotopic analyses of water samples show that the 18o values of surface bog waters follow the trend of precipitation despite significant scatter in the data set detailed sampling of surface waters within one bog shows that 18o values vary widely and are closely related to the micro topography of the bog surface more enriched 18o 16o ratios in water samples collected from small raised hummocks than the ones collected from hollows are documented in both horizontal and vertical profiles a 18o d plot indicates that the process leading to the isotopic enrichment of the uppermost surface waters is evaporation greater above sphagnum covered hummocks than above open pools to investigate the implications of such high variability of source water for plant cellulose 18o values a detailed study of both surface water and cellulose 18o values within one site is conducted the large 18o variability observed in surface waters is found to be considerably smoothed in cellulose by a factor of 5 10 depending on the plant species this indicates that the water used by plant photosynthetic processes reflects the isotopic composition of the average annual precipitation this points to a source water level for plants of a few decimeters where the variations are smaller than at the air water interface the response of the cellulose 18o to the environmental gradient along the altitude transect varies considerably from species to species for most of the species studied the 18o values decrease with altitude following the trends of 18o values in precipitation and in surface water samples some species the cotton sedge eriophorum vaginatum and the moss sphagnum capillifolium show statistically significant 18o relationships to an altitude of 1 8 km and 2 9 km respectively however some other plant species calluna vulgaris vaccinium uliginosum andromeda poliflora carex pauciflora sphagnum cuspidatum and sphagnum magellanicum do not or only partially reflect changes in climatic parameters associated with an altitude increase furthermore changes in relative humidity which are not correlated with altitude are found to explain a large part of the variability in 18o values for the sedge carex pauciflora and the moss sphagnum cuspidatum therefore this study confirms the importance of species specific studies when interpreting 18o 16o ratios of macrofossils along a fossil peat sequence as a record of past climate changes our study allows to extend the mechanistic model that isotopically links source water and cellulose to the physiological specificities of sedges and mosses a comparison of the modeled and calculated net biological fractionation factors for eriophorum vaginatum and sphagnum capillifolium reveals that these two species appear to have a more homogeneous leaf reservoir than trees

pliocene climate variability northern annular mode in models and tree ring data the northern annular mode nam and its regional expression the north atlantic oscillation nao are the primary interannual oscillatory systems in the northern hemisphere in the modern climate nam has been linked with a number of weather extremes including large terrestrial temperature increases and extreme snowfalls its connection to climate is more controversial although a change in its behaviour between 1970 and 2000 coincided with rapid temperature increases in the northern hemisphere the north atlantic and nordic seas are a key component in pliocene climate showing the largest increases from modern sea surface temperature to understand these changes and the ability of climate models to reproduce them we must consider simulations of the nam here we show that existing mid pliocene simulations exhibit large changes to the mean state and variability in the north atlantic and a significant dampening of the nao through sensitivity experiments this change is primarily attributed to the impact of the lowering of the rocky mountains as the timing of rocky mountains uplift is still disputed simulations of the north atlantic region contain significant uncertainty particularly relating to interannual variability and its climate feedbacks new high temporal resolution climate proxy data is required to test these model reconstructions here we report new annual resolution data and an analysis of climate variability from fossil tree rings these fossils from sites in the canadian arctic provide support for a strong north atlantic oscillation during the pliocene

quartz c axes orientation determination using the rotating polarizer microscope abstract a fast and accurate optical method to calculate quartz c axis orientations using the rotating polarizer stage and standard thin sections is presented c axis orientations are calculated for each pixel and achsenverteilungsanalyse ava can easily be constructed to study problems that would normally require a prohibitive amount of tedious work the computer controlled rotating polarizer stage replaces the polarizer and analyzer of the standard petrographic microscope and allows a thin section to remain fixed while the polarizing filters are rotated by stepper motors data are collected by stepping the polarizers through a 180 rotation capturing a frame at each step and extracting information on the intensity of the pixel and position of the polarizers the position data are used to calculate the trend or trend 180 of the quartz c axes while a simple mathematical relationship between intensity and plunge is derived which allows the plunges of c axes to be calculated

high temperature retrogression of granulite facies marbles form the reynolds range group central australia phase equilibria isotopic resetting and fluid fluxes reynolds range group rocks underwent granulite facies metaintroduction morphism m2 at 1 6 ga 5 kbar 750 800 c and were the uplift history of high grade metamorphic belts comsubsequently retrogressed in narrow strike parallel zones at 1 59 monly involves partial re equilibration of mineral as1 57 ga within these zones metacarbonates that initially equisemblages to lower temperature and pressure conditions librated at x 2 0 8 during m2 were mineralogically reset this re equilibration is facilitated by fluid rock interby the infiltration of water rich fluids x 2 0 02 0 3 at action and new mineral assemblages are often best 650 700 c and 3 4 kbar do carb values of the retrogressed developed in discrete zones of extensive retrogression metacarbonates were variably reset during fluid infiltration with the e g van reenen 1986 cartwright 1988 peters lowest values 10 13 suggesting that the fluids that caused wickham 1994 cartwright buick 1995 petrological retrogression were exsolved from segregated partial melts themselves studies of retrograde mineral assemblages may provide derived from the underlying granulite facies metapelites minimportant information about the tectonics and hydroeralogical and isotopic resetting were locally accompanied by silica geology of the lower and middle crust metasomatism the mineralogically reset marbles record time inhowever although there have been many recent quantegrated fluid fluxes of typically 10 10 m m and metasomatic titative studies of metamorphic fluid rock interaction in rocks record time integrated fluid fluxes as high as 10 10 m contact aureoles cartwright valley 1991 ferry m for upward flow of high temperature fluids through the marbles dipple 1991 young morrison 1992 jamveit et al over a distance of 200 m in 18 ma the observed mineralogical 1992 davis ferry 1994 and during prograde regional and isotopic resetting and metasomatism require intrinsic permetamorphism bickle baker 1990a 1990b ferry meabilities between 10 and 10 m that vary across strike 1992 stern et al 1992 leger ferry 1993 cartwright on a centimetre to metre scale indicating that fluid flow was strongly et al 1995 buick cartwright 1996 there have been channelled relatively few studies of high temperature retrogression vennemann stuart smith 1992 peters wickham 1994 cartwright buick 1995 therefore the origins of the retrograde fluids and the absolute timing of

crustal structure of the ruby mountains and southern carlin trend region nevada from magnetotelluric data abstract we have collected about 150 magnetotelluric mt soundings in northeastern nevada in the region of the ruby mountains metamorphic core complex uplift and southern carlin mineral trend in an effort to illuminate controls on core complex evolution and deposition of world class gold deposits the region has experienced a broad range of tectonic events including several periods of compressional and extensional deformation which have contributed to the total expression of electrical resistivity most of the soundings reside in three east west profiles across increasing degrees of core uplift to the north bald mountain harrison pass and secret pass latitudes one short cross line was also taken to assess an east west structure to the north of the northern profile model resistivity cross sections were derived from the mt data using a 2 d inversion algorithm which damps departures of model parameters from an a priori structure geological interpretation of the resistivity combines previous seismic potential field and isotope models structural and petrological models for regional compression and extension and detailed structural stratigraphic interpretations incorporating drilling for petroleum and mineral exploration to first order the resistivity structure is one of a moderately conductive phanerozoic sedimentary section fundamentally disrupted by intrusion and uplift of resistive crystalline rocks late devonian and early mississippian shales of the pilot and chainman formations together form an important conductive marker sequence in the stratigraphy and show pronounced increases in conductance conductivity thickness product from east to west these increases are attributed to graphitization caused by elko sevier era compressional shear deformation and possibly by intrusive heating the resistive crystalline central massifs adjoin the host stratigraphy across crustal scale steeply dipping fault zones the zones provide pathways to the lower crust for heterogeneous upper crustal induced electric current flow resistive core complex crust appears steeply bounded under the middle of the neighboring grabens and not to deepen at a shallow angle to arbitrary distances to the west the numerous crustal breaks imaged with mt may contribute to the low effective elastic thickness t e estimated regionally for the great basin and exemplify the mid crustal steeply dipping slip zones in which major earthquakes nucleate an east west oriented conductor in the crystalline upper crust spans the east humboldt range and northern ruby mountains the conductor may be related to nearby graphitic metasediments with possible alteration by middle tertiary magmatism lower crustal resistivity everywhere under the profiles is low and appears quasi one dimensional it is consistent with a low rock porosity

on the temperature correlation of δ18o in modern precipitation reevaluation of modern precipitation temperature and isotope data permits reconciliation of previous disparate values for the correlation between 18o of modern precipitation and surface temperature past analysis has used the mean surface temperature over the time interval of sample collection e g mean weekly monthly or annual temperature to calculate temperature coefficients and different approaches at mid latitudes yield different temperature coefficients 18o t spatial correlations among geographically distinct sites yield 0 55 k seasonal variations at single sites yield 0 2 0 4 k and 12 month running averages yield 0 5 1 k however there are systematic differences in temperature during precipitation events vs time averaged surface temperature means correction for this bias using hourly weather and monthly isotope data from u s sites yields a single value of 0 55 k for all three approaches revised temperature coefficients based on surface observations are also commensurate with coefficients obtained using cloud base temperatures and with theoretical distillation models 0 5 0 7 k these coefficients provide a consistent basis for validation of general circulation models that incorporate stable isotopes of precipitation and for comparison to independent estimators of the isotopic response to climate change

climate signals in tree ring width density and δ13c from larches in eastern siberia russia abstract we present the first and longest 413 years dataset on stable carbon isotope ratios in tree ring cellulose 13c tree ring width trw and maximum latewood density mxd obtained from larch trees growing on permafrost under continental climate in the suntar khayata mountain ridge in eastern siberia russia with this first study we calibrate tree ring parameters against climate quantities and based on these results assess the potential added value of mxd and especially of 13c complementing trw analysis for future climate reconstruction purposes 13c chronologies were corrected for human induced changes in atmospheric co2 since ad 1800 two different approaches were compared i a correction referring merely to the decline in atmospheric 13c 13catm and ii a correction additionally accounting for the increase in atmospheric partial pressure of co2 13c chronologies are characterized by strong signal strength with only 4 trees representing the population signal at the site mean inter series correlation 0 71 and eps 0 90 13c variation shows low similarity to trw and mxd while correlation between trw and mxd is highly significant correlation analysis of tree ring parameters with gridded instrumental data climate research unit cru ts 2 1 over the ad 1929 2000 calibration period demonstrates that trw and mxd react as reported from other sites at cold and humid northern latitudes precipitation plays no significant role but strong dependencies on monthly mean maximum and minimum temperatures particularly of the current summer june to august are found up to r 0 60 p

an investigation of the common signal in tree ring stable isotope chronologies at temperate sites we observed a strong common high frequency interannual signal for thed 13 c chronologies whereas the low frequency decadal scale signal was more similar among thed 18 o chronologies for both carbon and oxygen isotopes we found significant positive relationships with annual and growing season temperatures and negative relationships with precipitation again of similar magnitude for all species except forfraxinus which contained only minor climatic information averaging of all chronologies resulted in an increase in the climatic signal of the mean chronology the combinedd 18 o record reflected decadal scale temperature variations remarkably well r 0 72 however the relationship between climate and carbon isotopes declined over the last 3 decades of the 20th century probably related to the steep increase in atmospheric co 2 concentrations resulting in strongly divergingd 13 c trends of the different chronologies our study indicates that combining chronologies from different species enhances the potential of isotope studies for extending climate reconstructions into areas of temperate climate

dating the detachment fault system of the ruby mountains nevada significance for the kinematics of low angle normal faults 1 the mechanics of low angle normal faulting and metamorphic core complexes continue to be a subject of debate we investigate the conditions timing and kinematics of slip in the late upper crustal stages of core complex evolution of the ruby mountains detachment fault at the well exposed secret pass locality with an x ray diffraction xrd and ar ar study of clay gouge samples from three separate faults two from the low angle detachment system and one from a high angle normal fault that soles into the main detachment fault system xrd analysis and modeling of xrd analysis show that authigenic illite rich illite smectite i s in gouge at secret pass is distinguishable from clay phases in hanging wall rocks because the i s in the gouges contains only one water layer as opposed to the more common two water i s phases found in both the hanging wall and footwall ar ar ages for the monomineralic one water i s found in the hanging wall high angle fault the main detachment and a low angle normal fault structurally above the main detachment are 11 6 0 1 ma 12 3 0 1 ma and 13 8 0 2 ma respectively the not quite flat ar ar spectra indicate the gouge illites grew over some interval of time and not in discrete events the nearly overlapping ages indicate that gouge formation and thus the last major period of activity on the detachment were at 11 13 ma and were active coevally as part of a kinematically linked fault system with the main detachment active at dips 45 and possibly as low as 22

a 500 year record of summer near ground solar radiation from tree ring stable carbon isotopes tree ring stable carbon isotope ratios d13c in environments of low moisture stress are likely to be controlled primarily by photosynthetic rate therefore sunshine rather than temperature represents the more direct controlling factor temperature reconstructions based on tree ring d13c results thus rest on the assumption that temperature and sunshine are strongly coupled this assumption is tested using a d13c series from pine trees in nw norway where there are long 100 yr records of both summer temperature and cloud cover it is demonstrated that when summer temperature and d13c diverge summer temperature and cloud cover also diverge and that cloud cover sunshine may provide a stronger and more consistent parameter with which to calibrate tree ring d13c series in this area when a 500 year reconstruction of summer cloudiness is compared with a published reconstruction of summer temperatures in northern sweden based on tree ring maximum densities the two time series are largely parallel with

calibration of the carbonate clumped isotope paleothermometer for otoliths paleothermometry is an essential tool for understanding past changes in climate the carbonate clumped isotope thermometer is a temperature proxy related to ordering of 13 c and 18 o in the carbonate lattice based on measurements of 13 c 18 o 16 o in co 2 produced by acid digestion of carbonate this thermometer has been previously calibrated for inorganic calcite and aragonitic corals ghosh p adkins j affek h balta b guo w f schauble e a schrag d and eiler j m 2006 c 13 o 18 bonds in carbonate minerals a new kind of paleothermometer geochim cosmochim acta70 6 1439 1456 here we determine the relationship between growth temperatures of aragonitic fish otoliths and abundances of 13 c 18 o 16 o produced by acid digestion of those otoliths our calibration is based on analyses of otoliths from six species from four genera of modern fish sampled from a latitudinal transect of the atlantic ocean between 54 s and 65 n plus one species from the tropical western pacific the temperatures at which fish otoliths precipitated were estimated by the mean temperature in the waters in which they lived averaged over their estimated lifetimes estimated growth temperatures of our samples vary between 2 and 25 c our results show that the abundance of 13 c 18 o 16 o in co 2 produced by acid digestion of fish otolith aragonite is a function of growth temperature following the relationship 47 0 0568x10 6 t 2 where 47 is the enrichment in per mil of 13 c 18 o 16 o in co 2 relative to the amount expected for a stochastic random distribution of isotopes among all co 2 isotopologues and t is the temperature in kelvin this relationship closely approaches that previously documented for inorganic calcite and aragonitic coral ghosh et al 2006

pliocene warmth polar amplification and stepped pleistocene cooling recorded in ne arctic russia understanding the evolution of arctic polar climate from the protracted warmth of the middle pliocene into the earliest glacial cycles in the northern hemisphere has been hindered by the lack of co

a spherical electron channelling pattern map for use in quartz petrofabric analysis electron channelling patterns ecp s are formed in the scanning electron microscope sem by the interaction between the incident electrons and the lattice of crystalline specimens the patterns are unique for a particular crystallographic orientation and are therefore of considerable potential in petrofabric studies provided they can be accurately indexed indexing requires an ecp map of the crystallographic stereogram or unit triangle covering all possible orientations and hence ecp patterns due to the presence of long range distortions in planar ecp maps it is more convenient to construct the maps over a spherical surface this also facilitates the indexing of individual ecp s a spherical ecp map for quartz is presented together with an example of its use in petrofabric analysis

evaluating quartz crystallographic preferred orientations and the role of deformation partitioning using ebsd and fabric analyser techniques quartz crystallographic preferred orientations cpo from three distinct orthogneisses using both the electron back scatter diffraction ebsd and fabric analyser fa techniques reveal a clear trend from basal and rhomb slip for high p t conditions 670 20 degrees c 9 kbar rhomb and basal slip for medium p t 590 15 degrees c 6 kbar and a dominance of prism slip for lower p t conditions 570 degrees c 4 5 kbar the textural variations are interpreted in terms of a temperature field gradient and microscale strain partitioning controlled by a weak feldspar matrix that can locally invert the expected slip system sequences locally quartz cpus are different within one thin section and in comparison to bulk orientation measurements both ebsd and the fabric analyser techniques are ideal to determine such textural heterogeneities while the ebsd is a powerful technique to determine the full cpo measurements from similar locations inside several quartz grains from the orthogneisses and an annealed and undeformed quartzite show that the fa is an accurate tool to determine cpus of c axis orientations in uniaxial materials in a cpo focussed study the fa is a cheap alternative to ebsd as the analysis of whole thin section can be accomplished in a very short time with minimal sample preparation with the fa it is possible to evaluate the cpus of several samples quickly with an accuracy that allows identification of the main slip systems and their homogeneity

climate in southwestern ontario canada between ad 1610 and 1885 inferred from oxygen and hydrogen isotopic measurements of wood cellulose from trees in different hydrologic settings abstract oxygen and hydrogen isotopes were measured in wood cellulose and cellulose nitrate from trees that grew in different hydrologic settings in southwestern ontario canada an isotope model that accounts for isotopic fractionations associated with photosynthesis in plants was applied to the stable isotope data to infer past meteoric water isotopic composition and seasonal air moisture variations the model inferred climate data was rationalized in terms of the trees hydrologic environment and weather characteristics of the great lakes region the result is an account of summer and winter conditions in southwestern ontario for 275 years 1610 to 1885 prior to instrumental climate records conditions between 1610 and 1750 are inferred to have been cooler and drier than present this was followed by a warm moist climate interval between 1750 and 1885 during which there was an increase in winter precipitation cool dry conditions were recorded instrumentally in this region at the end of the nineteenth century

seasonal variability in arctic temperatures during early eocene time abstract as a deep time analog for today s rapidly warming arctic region early eocene 52 53 ma rock on ellesmere island in canada s high arctic 79 n preserves evidence of lush swamp forests inhabited by turtles alligators primates tapirs and hippo like coryphodon although the rich flora and fauna of the early eocene arctic imply warmer wetter conditions than at present the quantification of eocene arctic climate has been more elusive by analyzing oxygen isotope ratios of biogenic phosphate from mammal fish and turtle fossils from a single locality on central ellesmere island we infer early eocene arctic temperatures including mean annual temperature mat of 8 c mean annual range in temperature of 16 5 19 c warm month mean temperature of 19 20 c and cold month mean temperature of 0 3 5 c our seasonal range in temperature is similar to the range in estimated mat obtained using different proxies in particular relatively high estimates of early eocene arctic mat and sst by others that are based upon the distribution of branched glycerol dialkyl glycerol tetraether gdgt membrane lipids in terrestrial soil bacteria and isoprenoid tetraether lipids in marine crenarchaeota fall close to our warm month temperature suggesting a bias towards summer values from a paleontologic perspective our temperature estimates verify that alligators and tortoises by way of nearest living relative based climatic inference are viable paleoclimate proxies for mild above freezing year round temperatures although for both of these reptilian groups past temperature tolerances probably were greater than in living descendants

carbon and oxygen isotopes of lakeshore black spruce trees in northeastern canada as proxies for climatic reconstruction abstract in the boreal zone of northeastern canada paleoclimatic reconstructions of millennial length are rare and long isotopic climatic records are unavailable however millennial tree ring series could be constructed within the region by cross dating sub fossil stems preserved in the littoral part of lakes thus there is a need to evaluate the potential of using stable isotopes of lakeshore black spruce trees picea mariana mill b s p as proxies for climatic reconstruction we collected four living riparian black spruce trees and we investigated the inter and intra tree correlations for four trees at two different sampling heights 1 and 4 m for their carbon 13c and oxygen 18o isotopes as a test for potential long term reconstruction a significant correlation pearson coefficient for the isotopic series was found for the two sampling heights r 0 92 for 13c 0 65 for 18o and between the four trees we further assessed the climatic significance of the mean of the four trees the strongest correlation of the 13c series was with the mean of june to august vapor pressure deficit vpd r 0 50 and the 18o values with the june to august climatic index and june to july maximal temperature r 0 61 and 0 55 respectively this study suggests that 18o series of riparian black spruce trees and eventually their sub fossil counterparts can be used as proxies for reconstructing long climatic series in northeastern canada

cenozoic deep sea temperatures and global ice volumes from mg ca in benthic foraminiferal calcite a deep sea temperature record for the past 50 million years has been produced from the magnesium calcium ratio mg ca in benthic foraminiferal calcite the record is strikingly similar in form to the corresponding benthic oxygen isotope 18o record and defines an overall cooling of about 12 c in the deep oceans with four main cooling periods used in conjunction with the benthic 18o record the magnesium temperature record indicates that the first major accumulation of antarctic ice occurred rapidly in the earliest oligocene 34 million years ago and was not accompanied by a decrease in deep sea temperatures

coupling of co2 and ice sheet stability over major climate transitions of the last 20 million years the co2 content of the atmosphere has varied cyclically between 180 and 280 ppmv over the last 800 000 years closely coupled with temperature and sea level for earlier periods in earth s history pco2 is much less certain and the relationship between pco2 and climate remains poorly constrained we use boron calcium ratios in foraminifera to estimate pco2 during major climate transitions of the last 20 million years myr during the middle miocene when temperatures were 3 to 6 c

significantly warmer arctic surface temperatures during the pliocene indicated by multiple independent proxies temperatures in the arctic have increased by an astounding 1 c in response to anthropogenic forcing over the past 20 years and are expected to rise further in the coming decades the pliocene 2 6 5 3 ma is of particular interest as an analog for future warming because global temperatures were signifi cantly warmer than today for a sustained period of time with continental confi gurations similar to present here we estimate mean annual temperature mat based upon three independent proxies from an early pliocene peat deposit in the canadian high arctic our proxies including oxygen isotopes and annual ring widths mat 0 5 1 9 c coexistence of paleovegetation mat 0 4 4 1 c and bacterial tetraether composition in paleosols mat 0 6 5 0 c yield estimates that are statistically indistinguishable the consensus among these proxies suggests that arctic temperatures were 19 c warmer during the pliocene than at present while atmospheric co 2 concentrations were 390 ppmv these elevated arctic pliocene temperatures result in a greatly reduced and asymmetrical latitudinal temperature gradient that is probably the result of increased poleward heat transport and decreased albedo these results indicate that arctic temperatures may be exceedingly sensitive to anthropogenic co 2 emissions