terrestrial and marine extinction at the triassic jurassic boundary synchronized with major carbon cycle perturbation a link to initiation of massive volcanism mass extinction at the triassic jurassic tr j boundary occurred about the same time 200 ma as one of the largest volcanic eruptive events known that which characterized the central atlantic magmatic province organic carbon isotope data from the uk and greenland demonstrate that changes in flora and fauna from terrestrial and marine environments occurred synchronously with a light carbon isotope excursion and that this happened earlier than the tr j boundary marked by ammonites in the uk the results also point toward synchronicity between extinctions and eruption of the first central atlantic magmatic province lavas suggesting a causal link between loss of taxa and the very earliest eruptive phases the initial isotopic excursion potentially provides a widely correlatable marker for the base of the jurassic a temporary return to heavier values followed but relatively light carbon dominated the shallow oceanic and atmospheric reservoirs for at least 600 k y

baltic sea ice sar segmentation and classification using modified pulse coupled neural networks a method for segmentation and classification of baltic sea ice synthetic aperture radar sar images based on pulse coupled neural networks pcnns is presented also automated training which is based on decomposing the total pixel value distribution into a mixture of class distributions is presented and discussed the algorithms have been trained and tested using logarithmic scale radarsat 1 scansar wide mode images over the baltic sea ice before the decomposition into mixture of class distributions an incidence angle correction specifically designed for these baltic sea ice sar images is applied because the data distributions in the uniform areas of these images are very close to gaussian distributions the data are decomposed into a mixture of gaussian distributions using the expectation maximazation algorithm only uniform image areas are used in the decomposition phase the mixture of distributions is compared to the distributions of the baltic sea ice classes based on earlier scatterometer measurements and visual video interpretations of the sea ice classes the parameter values for the pcnn segmentation are defined based on this mixture of distributions the pcnn segmentation results are also compared to the operational sea ice information of digitized ice charts and to visual interpretation of the sea ice class

discrimination of open water from sea ice in the labrador sea using quad polarized synthetic aperture radar abstract a method to differentiate open water from sea ice using quad polarization c band synthetic aperture radar sar imagery is presented based on the roughness properties of the sea surface scattering facets and the polarization ratio pr between vv and hh polarization backscatter from the sar images in quad polarization sar images the normalized radar cross section nrcs which is linked to sea surface roughness can be used to derive the orientation angle shift and its standard deviation as well as to compute the measured polarization ratio pr an x bragg backscatter model is explored to calculate a theoretical look up table for the polarization ratio as a function of incidence angle dielectric constant orientation angle shift and its standard deviation thus ocean surface backscatter can be identified as open water or sea ice by comparing the measured pr with a theoretical model for pr the proposed method is validated by comparison to collocated optical video images and manual visual interpretations estimates of the size shape and locations of open water from our method are shown to be in good agreement with observed data the overall accuracy of our algorithm is about 96 the classification accuracy for sea ice and open water is about 96 and 94 respectively

new constraints on atmospheric co2 concentration for the phanerozoic earth s atmospheric co2 concentration ca for the phanerozoic eon is estimated from proxies and geochemical carbon cycle models most estimates come with large sometimes unbounded uncertainty here we calculate tightly constrained estimates of ca using a universal equation for leaf gas exchange with key variables obtained directly from the carbon isotope composition and stomatal anatomy of fossil leaves our new estimates validated against ice cores and direct measurements of ca are less than 1000 ppm for most of the phanerozoic from the devonian to the present coincident with the appearance and global proliferation of forests uncertainties obtained from monte carlo simulations are typically less than for ca estimates from other approaches these results provide critical new empirical support for the emerging view that large 2000 3000 ppm long term swings in ca do not characterize the post devonian and that earth s long term climate sensitivity to ca is greater than originally thought key points a novel co2 proxy calculates past atmospheric co2 with improved certainty co2 is unlikely to have exceeded 1000 ppm for extended periods post devonian earth s long term climate sensitivity to co2 is greater than originally thought

predicting of uniaxial compressive strength of some igneous and metamorphic rocks by block punch index and cylindrical punch index tests abstract uniaxial compressive strength ucs of rock materials is a crucial parameter in designing of engineering structures to be constructed in on rock masses although the suggested methods for determination of ucs are well known and required relatively simple procedures preparation of standard core specimens may not be easy for rock materials of heavily jointed rock and or thinly stratified rock masses in order to overcome these difficulties to be encountered during sample preparation the studies on the alternative equations based on results of simple index tests for predicting of ucs of rock materials have been popular a linear correlation with conversion factor of 5 1 was suggested in literature for predicting of ucs from block punch index bpi considering a wide variety of rock types in this study the relations were investigated to be used for predicting of ucs from bpic and also cylindrical punch index cpi based on experimental studies employed on seven different igneous and metamorphic rocks collected from different locations in hamedan province west of iran the linear regression analysis showed that the conversion factor between ucs and bpic was obtained as 5 7 for the tested rocks which is already higher than the proposed value of 5 1 a conversion factor equal to 7 4 was derived for relation between ucs and cpi in addition the prediction performance of some well known equations on the test results obtained in this study for determination of ucs from bpic and also cpi were evaluated moreover the coefficients of determination of logarithmic and power functions were higher than any other functions for ucs bpic and ucs cpi relations respectively

reconstruction of seasonal precipitation in hawai i using high resolution carbon isotope measurements across tree rings abstract determination of carbon isotope 13 c values of tree ring tissue is a well established method to reconstruct past climate variability at annual resolution but such records are limited in tropical latitudes due to the lack of well defined annual growth bands recent work has demonstrated the potential for high resolution intra ring 13 c records to help define ring boundaries in tropical environments and provide additional climate information at sub annual resolution here we present a high resolution intra ring carbon isotope 13 c record of the hawaiian endemic species sophora chrysophylla also known as m mane in order to assess the ability to extract seasonal climate information from these drought tolerant trees tree cores were sampled from high elevation m mane trees growing on the west side of mauna kea big island across our entire dataset 1986 2008 we identified a notable decreasing linear trend in the 13 c record of 0 061 year that can be attributed to changes in the 13 c value of atmospheric co 2 and p co 2 concentration associated with fossil fuel burning correcting for these affects yields a nearly flat 13 c record with a slope of 0 0075 year suggesting no long term trends in climate across the study period we observe a quasi periodic change in the 13 c values 13 c measured within each ring that averages 1 09 0 50 1 n 23 in amplitude these variations are interpreted as the intra annual isotopic signal in tree photosynthesis the 13 c variability correlates with the visible ring structure of the sample suggesting the presence of annual growth rings at this tropical high elevation site we applied these data to a model that relates the 13 c value to seasonal changes in precipitation in order to reconstruct annual changes in total summer may through october and winter november through april precipitation at the site across the 23 year record 1986 2008 n 579 13 c measurements reconstructed values for the ratio of summer to winter precipitation total summer precipitation and total winter precipitation correlate well with rainfall data collected from a nearby weather station r 0 65 0 36 and 0 70 respectively these results support application of this model to reconstruct inter annual changes in seasonal precipitation from long term tree ring chronologies they also demonstrate the potential of using m mane 13 c for future long term climate reconstructions

considerations on strength of intact sedimentary rocks abstract this study presents the results of laboratory testing of sedimentary rocks under point loading as well as in uniaxial and triaxial compression from the statistical analysis of the data different conversion factors relating uniaxial compressive and point loading strength were determined for soft to strong rocks additionally the material constant mi an input parameter for the hoek and brown failure criterion was also estimated for different limestone samples by analysing the results from a series of triaxial compression tests under different confining pressures the uniaxial compressive strength ucs of intact rocks as estimated from the point load index using conversion factors together with the hoek brown constant mi and the geological strength index gsi constitute the parameters for the calculation of the strength and deformability of rock masses

prediction of engineering properties of a selected litharenite sandstone from its petrographic characteristics using correlation and multivariate statistical techniques abstract the determination of rock strength and elastic parameters in laboratory tests requires high quality core samples which are not always available from fractured and or weathered strata the purpose of this study is to apply a correlation analysis in conjunction with multivariate statistical techniques to petrographical and laboratory geomechanical data for the investigation of correlations that exist between these properties of a selected sandstone and to suggest inexpensive predictive models in a preliminary investigation sandstone samples from a borehole drilled for a preliminary investigation of a shaft location at a hard coal region black sea turkey were tested to determine uniaxial compressive strength elastic parameters unit weight porosity point load index and quality index secondly fifteen selected samples were subjected to petrographic examination which included fifteen parameters and modal analysis based on the statistical analysis results polynomial prediction equations were developed for estimating mechanical properties from petrographic characteristics and index properties the study revealed that the influence of textural characteristics appear to be more important than mineralogy for predicting engineering properties it is also noted that type of contacts grain shape and size rock fragments with packing density and proximity are the petrographic characteristics which have significant influence upon engineering properties of the sandstones results of this study were presented in the form of correlation coefficient models and predictive models

comparison of stable carbon isotope ratios in the whole wood cellulose and lignin of oak tree rings abstract the stable carbon isotope ratios 13c of whole wood cellulose and acid insoluble lignin from annual latewood increments of quercus robur l from modern and sub fossil wood were measured and their potential use as palaeoenvironmental indicators examined the resulting time series demonstrate a very high degree of coherence with 13c of cellulose isotopically enriched by approximately 3 compared to 13c of lignin the 13c values of all three components are influenced by the climate of july and august modern whole wood retains the strongest climate signal perhaps because its composition is closest to that of leaf sugars in sub fossil wood there is no evidence that differential decay leads to fractionation of carbon within either cellulose or lignin but differential decay can alter the cellulose to lignin ratio

the transitional climate of the late miocene arctic winter dominated precipitation with high seasonal variability the late miocene 11 6 5 3 ma was an important transitional period following the greenhouse conditions of the eocene in order to gain insight into the arctic paleoclimate of the time we performed high resolution intraring 13 c analyses on fossil wood collected from the late miocene khapchansky sediments of northeastern siberia 69 n from these data we quantified the ratio of summer to winter precipitation ps pw and compared it to current values for the region determined from modern wood samples and instrumental records we observed much greater frequency of winter dominated precipitation ps pw 1 and much greater variability in ps pw during the miocene than today specifically years with ps pw 1 occurred three times more often and years with at least three times as much precipitation in summer or winter 0 33 ps pw 3 0 occurred approximately twice as often during the miocene than today we attribute the high interannual variability in precipitation to an inconsistent moisture source associated with the relatively unstable and incomplete ice cover in the arctic ocean during the late miocene our result highlights the potential for enhanced variability in arctic precipitation in response to arctic sea ice decline caused by anthropogenic co 2 induced warming

the determination of uniaxial compressive strength from point load strength for pyroclastic rocks abstract the point load test has often been reported as an indirect measure of compressive strength it has been used widely in practice due to easy testing the simplicity of specimen preparation and possible field applications many researchers have investigated the relation between uniaxial compressive strength ucs and point load index is for different rock types however there are limited studies in the literature for soft rocks such as pyroclastic rocks in this study the relation between ucs and is was investigated for pyroclastic rocks having ucs values are less than 50 mpa very strong exponential relations were found for dry rocks saturated rocks and both dry and saturated rocks the results were also compared to the studies in the literature

carbon isotope behaviour in wood and cellulose during artificial aging abstract modern wood was subjected to an artificial decay process to investigate its behaviour with respect to the stable carbon isotope composition of wood and the corresponding cellulose four different woods were used namely oak quercus robur beech fagus sylvatica pine pinus sylvestris sequoia sequoiadendron giganteum and pure spruce cellulose the process of decay was simulated by heating samples in water at 180 c from minutes to months during the decay period the carbon content of wood increased to almost 70 while the cellulose content decreased gradually to zero the degradation proceeds according to a two stage process an initial very fast break down is followed by a rather slow degradation after a strong discrimination against 13 c during the initial phase the 13c 12c ratio increases again mostly up to its initial value the carbon isotope trend for cellulose shows a similar pattern though it is less pronounced maximum discrimination was 1 relative to the untreated wood 13c values of cellulose decreased by up to 0 3 the 13 c depletion is presumably a consequence of the preferential decomposition of cellulose as compared to lignin data on fossil trees are compared with the results obtained from this treatment of aging the 13 c decrease is in line with observations from these fossil woods but the ensuing 13 c enrichment is at most weakly to be seen

the point load test for weak rock in dredging applications abstract the point load test is shown useful for weak saturated rocks which are commonly encountered in mechanical dredging operation to support the dredging use of the point load test orginally intended to obtain a field strenth index for hard rock materials a comparative testing program was initiated which included more than four hundred rock tests the resulting data base system provides test a summary of test data and comparison calculations the data base contains point load and unconfined compressive strength tests and some wet versus dry strength comparison tests applicability of the point load test was shown for the weak rock materials typical of many coastal deposits a correlation with unconfined compressive strength was demonstrated for several dredge sites and for a low strength rock simulant however correlation factors were consistently much lower than the generalized or target average values cited in testing standards which are consistent with results in hard rock tunneling and mining applications

incidence angle correction of sar sea ice data based on locally linear mapping radar backscatter variations that occur because of incidence angle effects constrain the application of scanning synthetic aperture radar scansar data for sea ice monitoring and observations in this paper a class based correction is proposed for normalizing each class in scansar data to a nominal incidence angle two tested sea ice synthetic aperture radar sar data sets were acquired a data set for the gulf of saint lawrence which was obtained by the radarsat 2 satellite and a data set for the bohai sea which was obtained by the envisat advanced synthetic aperture radar an unsupervised classification is performed on each image block prior to normalization and the incidence angle range of each image block is approximately 5 because the distribution of the backscatter coefficients in the azimuth band is discrete and nonlinear the class based locally linear mapping llm technique is implemented based on the assumption that a small quantity of sorted backscatter coefficients is locally linear this algorithm is a transplantable and easily applied method that requires limited ground data and it is also a semiautomated technique because nearly all of its parameters can be adaptively determined during the image analysis the results demonstrate that llm corrected scansar images appear to have more detailed textures and the natural signal variability in the radar data is preserved which indicates that the llm produces better results compared with the histogram based alike hist alike technique when correcting the incidence angle in the sea ice sar data the results of the data analysis in this paper show that the width of the azimuth band should be selected based on the extent of variation in the incidence angle and the reference band can be calculated based on the maximum interclass distance principle the intercomparisons also reveal that the proposed algorithm can improve the accuracy of supervised classifications

estimating the wet rock p wave velocity from the dry rock p wave velocity for pyroclastic rocks seismic methods are widely used for the geotechnical investigations in volcanic areas or for the determination of the engineering properties of pyroclastic rocks in laboratory therefore developing a relation between the wet and dry rock p wave velocities will be helpful for engineers when evaluating the formation characteristics of pyroclastic rocks to investigate the predictability of the wet rock p wave velocity from the dry rock p wave velocity for pyroclastic rocks p wave velocity measurements were conducted on 27 different pyroclastic rocks in addition dry rock s wave velocity measurements were conducted the test results were modeled using gassmann s and wood s theories and it was seen that estimates for saturated p wave velocity from the theories fit well measured data for samples having values of less and greater than 20 practical equations were derived for reliably estimating wet rock p wave velocity as function of dry rock p wave velocity

characterization and quality assessment of granitic building stone deposits a case study of two different portuguese granites abstract several factors determine building stone exploration in order to maximize the extraction processing and application of these natural materials some factors are intrinsic to stones such as their physical mechanical properties while others are related to their exploitability such as quarry reserves or fracturing density during an exploration campaign these factors are not always considered or properly weighed in terms of the negative consequences on quarry activities or rock behaviour under particular conditions in this study two well known portuguese granites are assessed to highlight the main factors these granites have different characteristics weathered and sound and are exploited in quarries with different joint densities the most relevant physical mechanical properties were evaluated and related to the specific petrophysical features of each granite the fracture patterns were identified in the quarries and then modelled in order to compute the quarry yield the weathered granite shows an important microcrack network and a general alteration of the rock forming minerals which has an important impact on its physical mechanical properties and on the resistance to environmental factors moreover the extreme differences in the degree of weathering require careful choices for the possible applications in both quarries the joint sets are similar to the regional faulting but some random joints can be found and consequently diminish the quarry yield the development of horizontal sheet joints during the exploitation process could have a great influence on the quarry productivity if they are not used do delimitate the extracted blocks the modelling of the natural fracture pattern allows us to determine the potential volume of blocks that could be exploited however the quality of the information gathered could lead to an over estimation of the quarry production this example shows the importance of the exhaustive researches during a building stone assessment campaign

the effects of early diagenesis on the chemical and stable carbon isotopic composition of wood abstract studies of modern and ancient buried wood show that there is a linear correlation between carbohydrate content and the stable carbon isotope composition as carbohydrates are preferentially degraded during early diagenesis as the carbohydrate content decreases the 13 c value of the degraded wood decreases 1 to 2 per mil approaching the value of the residual lignin these results indicate that carbohydrate degradation products are lost and not incorporated into the aromatic structure as lignin is selectively preserved during early diagenesis of wood these results also indicate that attempts to quantify terrestrial inputs to modern sedimentary organic matter based on 13 c values should consider the possibility of a 1 to 2 per mil decrease in the 13 c value of degraded wood

the mid oxfordian late jurassic positive carbon isotope excursion recognised from fossil wood in the british isles the carbon isotope ratios of fossil wood have recently been confirmed as a proxy for changes in the isotopic composition of palaeoatmospheres carbon isotope data from fossil wood samples collected from the jurassic oxfordian staffin shale formation on the isle of skye scotland boreal sub boreal ammonite zonation reveal a long term positive carbon isotope excursion of at least 3 this excursion reaches a maximum in the mid oxfordian and closely matches the carbon isotope ratios previously reported from belemnites collected from the same section and carbon isotope data from carbonates in other european sections this confirms that the mid oxfordian positive carbon isotope excursion affected the total exchangeable carbon reservoir fossilised wood samples collected at a higher stratigraphic resolution but over a shorter interval from the corallian group in dorset england antecedens parandieri and cautisnigrae subzones nw european ammonite zonation show considerable scatter in their carbon isotope ratios and no trends are discernable the combined isle of skye and dorset dataset shows that the long term oxfordian positive carbon isotope trend coincides with a long term relative sea level change and that the most positive carbon isotope ratios occur across the plicatilis transversarium biozonal boundary sub mediterranean ammonite zonation this implies that the carbon isotope excursion was not caused by the well documented rise in sea level in the transversarium zone although very low carbon isotope ratios from fossil wood samples are recorded from the nodular rubble member parandieri subzone of dorset there is not a sufficiently coherent signal to ascribe these values to the gas hydrate dissociation event previously hypothesized from the carbon isotope ratios of tethyan marine carbonates a microscopal analysis of the charcoalified debris from the staffin shale formation indicates a prevalence of the wood genus cupressinoxylon derived from a cheirolepidiaceaen conifer

carbon isotope record of the early jurassic toarcian oceanic anoxic event from fossil wood and marine carbonate lusitanian basin portugal thetoarcianoceanicanoxicevent oae intheearlyjurassic 183maago wascharacterizedbywidespreadnear synchronous deposition of organic rich shales in marine settings as well as perturbations to several isotopic systems characteristically two positive carbon isotope excursions in a range of materials are separated by an abrupt negative shift carbon isotope profiles from toarcian fossil wood collected in england and denmark have previously been shown to exhibit this large drop 7 i n 13 c values interpreted as due to an injection of isotopically light co2 into the ocean atmosphere system however the global nature of this excursion has been challengedonthebasisofcarbon isotopedatafromnektonicmarinemolluscs belemnites whichexhibitheavierthanexpectedcarbonisotope values here we present new data principally from fossil wood and bulk carbonate collected at centimetre scale from a hemipelagic section at peniche coastal portugal this section is low in organic carbon average toc 0 5 and the samples should not have suffered significant diagenetic contamination by organic carbon of marine origin the carbon isotope profile based on wood shows two positive excursions separated by a large and abrupt negative excursion which parallels exactly the profile based on bulk carbonate samples from the same section albeit with approximately twice the amplitude 8 in wood versus 3 5 in carbonate these data indicate thatthe negative carbon isotope excursion affected the atmosphereand by implication the global ocean as well the difference in amplitude between terrestrial organic and marine carbonate curves can be explained by greater water availability in the terrestrial environment during the negative excursion for which there is independent evidence from marine osmiumisotope records and plausibly changes in atmospheric co2 content for which independent evidence is also available the peniche succession is also notable for the occurrence of re deposited sediments their lowest occurrence coincides with the base of the negative excursionandtheirhighestoccurrencecoincideswithitstop thus slopeinstabilityandsedimentsupplycouldhavebeenstronglylinked to the global environmental perturbation an association that may misleadingly simulate the effects of sea level fall

biomarker and stable carbon isotope systematics of fossil wood from the second lusatian lignite seam of the lubstow deposit poland abstract decay of fossil wood gelification collected from the middle miocene 2nd lusatian lignite seam at the lubstow open cast mine poland is characterised by its maceral variety fluorescence intensity and cellulose content cellulose decomposition leads to lower molar h c ratio values of the organic matter as indicated by higher total organic carbon toc content of samples characterised by low cellulose content biochemical formation of hydrocarbons in the wood due to enhanced microbial activity is evidenced by higher hydrocarbon content in the extracts higher relative proportions of n alkanes and hopanoids are observed in the hydrocarbon fractions of wood remains characterised by low cellulose yield the results provide evidence for the formation of these compounds during biogeochemical transformation of organic matter hopanoid contents are considered to reflect the activity of aerobic bacteria and or fungi because of enhanced perylene content in the hydrocarbon fractions from gelified wood samples fungi are considered as the major precursor carriers of this polycyclic aromatic hydrocarbon the results provide evidence that biomarker composition of fossil wood can be used to trace biochemical transformation processes chemotaxonomical classification of fossil wood fragments as gymnosperms most probably species of the coniferales families taxodiaceae cupressaceae are based on the molecular composition of terpenoid hydrocarbons and a mean 13 c value of 24 5 depletion of gelified samples in 13 c as compared to ungelified wood is caused by the effect of progressive decomposition of cellulose the data indicate that cellulose 13 c data mean 13 c 20 8 are also affected by wood decomposition and so only samples with comparable cellulose content should be used for the reconstruction of environmental changes inter species as well as intra plant variation in carbon isotope differences and of decay resistance between cellulose and lignin have to be taken into account

carbon isotope ratio of cenozoic co2 a comparative evaluation of available geochemical proxies 1 the carbon isotope ratio 13c of plant material is commonly used to reconstruct the relative distribution of c3 and c4 plants in ancient ecosystems however such estimates depend on the 13c of atmospheric co2 13cco2 at the time which likely varied throughout earth history for this study we use benthic and planktonic 13c and 18o records to reconstruct a long term record of cenozoic 13cco2 confidence intervals for 13cco2 values are assigned after careful consideration of equilibrium and non equilibrium isotope effects and processes as well as resolution of the data we find that benthic foraminifera better constrain 13cco2 compared to planktonic foraminiferal records which are influenced by photosymbiotes depth of production seasonal variability and preservation furthermore sensitivity analyses designed to quantify the effects of temperature uncertainty and diagenesis on benthic foraminifera 13c and 18o values indicate that these factors act to offset one another our reconstruction suggests that cenozoic 13cco2 averaged 6 1 0 6 1 while only 11 2 million of the last 65 5 million years correspond to the pre industrial value of 6 5 with 90 confidence here 13cco2 also displays significant variations throughout the record at times departing from the pre industrial value by more than 2 thus the observed variability in 13cco2 should be considered in isotopic reconstructions of ancient terrestrial plant ecosystems especially during the late and middle miocene times of presumed c4 grassland expansion

ice flow of the antarctic ice sheet we present a reference comprehensive high resolution digital mosaic of ice motion in antarctica assembled from multiple satellite interferometric synthetic aperture radar data acquired during the international polar year 2007 to 2009 the data reveal widespread patterned enhanced flow with tributary glaciers reaching hundreds to thousands of kilometers inland over the entire continent this view of ice sheet motion emphasizes the importance of basal slip dominated tributary flow over deformation dominated ice sheet flow redefines our understanding of ice sheet dynamics and has far reaching implications for the reconstruction and prediction of ice sheet evolution

reducing uncertainties in δ13c analysis of tree rings pooling milling and cellulose extraction recent developments of on line methods have provided another boost to the determination of stable isotope ratios in organic material along with a significant increase in sample throughput the sample sizes decrease both of which are necessary conditions to acquire long time series from limited wood amounts in view of this new technique we reconsidered the most important factors influencing the measured isotopic signature which are 1 pooling 2 homogeneity and 3 cellulose extraction in most cases pooling i e mixing wood of the same year from different trees can be made in a simple way by mixing the whole wood available because mass weighted and unweighted isotope measurements were the same within the error more attention must be paid in homogenizing the sample theoretical considerations underpinned by experimental results suggest a fineness of 0 15 mm 115 mesh if cellulose is extracted and 0 1 mm 165 mesh for direct wood analysis many of previous studies did not achieve this fineness we find that wood is as good a climate proxy as cellulose this is shown by comparing correlations of wood and corresponding cellulose isotope values with meteorological data which are identical within the uncertainty

annual patterns within tree rings of the arctic middle eocene ca 45 ma isotopic signatures of precipitation relative humidity and deciduousness the spectacular preservation of middle eocene ca 45 ma wood allows for intra season sampling of stable carbon oxygen and hydrogen in order to reconstruct the paleoseasonal environment of this arctic forest paleolatitude 78 6 1 6 n present latitude 80 n carbon isotopes in bulk organics and cellulose reveal striking annual patterns interpreted as the seasonal switchover from stored to actively acquired carbon associated with deciduous growth in these unusual conifers oxygen and hydrogen stable isotopes of cellulose and cellulose nitrate allow for the calculation of changes in relative humidity and in the isotopic value of plant available water clear annual patterns of increasing relative humidity resulting from tissue growth and concomitant transpiration are apparent as is the systematic increase in the reconstructed oxygen isotope value of environmental water refl ecting progressively increasing temperatures during the growing season

sea ice motion tracking from sequential dual polarization radarsat 2 images a new sea ice motion tracking algorithm that operates with two sequential synthetic aperture radar sar radarsat 2 scansar images is presented the feature tracking approach is based on the combination of the phase correlation and cross correlation methods an algorithm for selecting control points a matching technique an approach for filtering out error vectors and a confidence levels setting for output drift vectors were specifically developed in order to increase the system s robustness and accuracy we evaluated ice motion tracking results derived from hh and hv channels of radarsat 2 scansar imagery and formulated a condition where the hv channel is more reliable than the hh channel for ice tracking furthermore we found that the ice motion tracking from the hv channel is not affected by noise floor stripes which are prominent in the cross polarization radarsat 2 scansar images the developed sea ice tracking technology was implemented at the canadian ice service environment canada for operational use the system was successfully run to provide operational support of field work in the arctic ocean in compliance with the united nations convention on the law of the sea in the spring of 2010

incidence angle dependence of hh polarized c and l band wintertime backscatter over arctic sea ice synthetic aperture radar sar incidence angle has a significant effect on the microwave backscatter from sea ice this paper investigates the incidence angle dependence of c and l band hh polarized microwave backscatter coefficient over arctic first year sea ice fyi and multiyear sea ice myi in winter advanced land observation satellite phased array type l band sar l band and radarsat 2 c band images are used to derive ice type specific incidence angle dependencies calculated using linear regression models for l band mean ice type specific incidence angle dependencies for fyi and myi are 0 21 and 0 30 db 1 respectively and for c band they are 0 22 and 0 16 db 1 respectively to validate our results we calculated root mean square deviation rmsd by comparing the ice type specific dependence from 2010 with individual dependencies from 2009 based on ice types and frequencies the rmsd is found to be smaller than the standard deviation of ice type specific dependencies for both frequencies the rmsd values for the l band incidence angle dependencies are 0 03 and 0 04 db 1 for fyi and myi respectively for c band the rmsd values for the fyi and myi dependencies are 0 03 and 0 01 db 1 respectively subsequently we demonstrate that after applying incidence angle normalization the variability of c and l band sar backscatter reduces and separability of ice types increase substantially

massive dissociation of gas hydrate during a jurassic oceanic anoxic event in the jurassic period the early toarcian oceanic anoxic event about 183 million years ago is associated with exceptionally high rates of organic carbon burial high palaeotemperatures and significant mass extinction heavy carbon isotope compositions in rocks and fossils of this age have been linked to the global burial of organic carbon which is isotopically light in contrast examples of light carbon isotope values from marine organic matter of early toarcian age have been explained principally in terms of localized upwelling of bottom water enriched in 12c versus 13c refs 1 2 5 6 here however we report carbon isotope analyses of fossil wood which demonstrate that isotopically light carbon dominated all the upper oceanic biospheric and atmospheric carbon reservoirs and that this occurred despite the enhanced burial of organic carbon we propose that as has been suggested for the late palaeocene thermal maximum some 55 million years ago the observed patterns were produced by voluminous and extremely rapid release of methane from gas hydrate contained in marine continental margin sediments

object based landfast sea ice detection over west antarctica using time series alos palsar data abstract landfast sea ice fast ice is an important feature prevalent around the antarctic coast which is affected by climate change and energy exchanges with the atmosphere and ocean this study proposed a method for detection of the west antarctic fast ice using the advanced land observing satellite phased array l band sar alos palsar images the algorithm has combined image segmentation image correlation analysis and machine learning techniques i e random forest rf extremely randomized trees ert and logistic regression lr we used sar images with a baseline of 5 days that are not in the same orbit but overlap each other as overlaps between swaths in adjacent orbits are often available in the polar regions the underlying assumption for the proposed fast ice detection algorithm is that fast ice regions in sar images with a time interval of 5 days are highly correlated the object based approach proposed in this study was well suited to high resolution sar images in deriving spatially homogeneous fast ice regions the image segmentation results using the optimized parameters showed a distinct difference in the backscatter temporal evolution between fast ice and pack ice regions correlation and std of backscattering coefficients were found to be the most significant variables for the object based fast ice detection from two temporally separated images in overall the quantitative and qualitative evaluation demonstrated that the algorithm was an effective approach to detect fast ice with high accuracies the models well detected various fast ice regions in the west antarctica but misclassified some objects the misclassifications occurred toward the edge of fast ice regions with relatively rapid changes in backscattering between both data acquisitions on the other hand few fast ice objects were misclassified as uniform backscattering over time occurred by chance on very small objects far from the coast very old multi year fast ice regions with high backscattered signals were also a source for some misclassifications this may be due to the sensitivity of l band to snow structure to some extent and a thinner ice over the region with either ice growth no deformation or closing slight deformation between both images heavy snow load on the ice could be another error source for some misclassification as well the approach allowed for the reliable detection of fast ice regions by using l band sar images with a small local incidence angle difference

predictive model for uniaxial compressive strength for grade iii granitic rocks from macao abstract determination of the uniaxial compressive strength ucs of rocks is an important task for rock and geotechnical engineering applications direct measurement is expensive time consuming and even infeasible in some circumstances due to the difficulty in obtaining core samples therefore empirical models are particularly favorable to engineers especially in the preliminary design stage however there is a lack of predictive ucs model for granite of weathering grade iii but it is well recognized to be crucial to the design of pile foundations on granitic bedrocks in this study a reliable predictive model will be developed under the bayesian framework an extensive experimental program was performed in this study to construct a comprehensive database of the measurements of uniaxial compressive strength point load index schmidt rebound hammer value p wave velocity effective porosity specific gravity and dry density it has been proven that the proposed model possesses satisfactory predictive performance

carbon isotope analysis of fossil wood and dispersed organic matter from the terrestrial wealden facies of hautrage mons basin belgium pedogenic nodules calcitic shells dispersed organic carbon and bulk rocks affected by low diagenesis are judged to be reliable tools for carbon isotope chemostratigraphy up to now no systematic study has been carried out to check the reliability of fossil wood material for carbon isotope chemostratigraphy in terrestrial settings the 235 m thick wealden facies sediments of the danube bouchon quarry at hautrage hautrage clays formation mons basin belgium encompass dark to grey clays and sands rich in organic matter and coalified charcoalified fragments of fossil wood deposited in an alluvial plain during middle barremian to earliest aptian we measured and compared the carbon isotope ratios of 110 levels of the stratigraphic succession for dispersed organic carbon delta c 13 doc and fossil wood delta c 13 wood collected in the same geological level in the whole succession the averages of delta c 13 doc and delta c 13 wood have a significant difference of about 0 9 the delta c 13 wood is usually heavier than the delta c 13 doc which is consistent with measurements on different constituents of modern trees branches versus leaves and tissues in one single stratigraphic level the variability of delta c 13 wood is much higher up to 7 3 parts per thousand than that of delta c 13 doc 0 4 parts per thousand four main causes may explain these results firstly the delta c 13 doc averages the isotopic signal of different compounds and tissues such as leaves seeds cuticles as they become mixed and dispersed the delta c 13 wood reflects the carbon isotope ratio of a small part only of one single tree which is a complex system with delta c 13 variations over a range of 4 parts per thousand secondly there is strong delta c 13 variability between different species of plants in hautrage several gymnosperm genera were collected including podocarpoxylon taxodioxylon brachyoxylon and thujoxylon and numerous fern taxa thirdly coalification and charcoalification can affect the delta c 13 of the doc and the various kinds of woods in a different way fourthly the wood fragments may be reworked several times from more ancient geological levels especially in the alluvial plain environment of hautrage where thick levels of fluviatile coarse sand deposits are observed however in the whole succession both delta c 13 wood and delta c 13 doc curves show similar trends this suggests that carbon isotope curves on fossil wood can be matched to carbon isotope curves on doc for the whole trend fossil wood is a relatively good chemostratigraphic tool when sufficient samples are measured in the succession whenever possible both control of the wood taxa and estimation of degree of char coalification are however recommended in one single level charcoal has more stable delta c 13 wood values than delta c 13 wood of coalified fragments the delta c 13 positive trend can be due to several causes including global pco 2 variations and or regional changes and or local environmental conditions in the alluvial plain if global the dating of the hautrage succession may be refined to the late early barremian early late barremian by matching palynological and carbon isotope chemostratigraphical data c 010 elsevier b v all rights reserved

comparison of models for estimating uniaxial compressive strength of some sedimentary rocks from qom formation to estimate uniaxial compressive strength of some sedimentary rock types from a set of index test results selected soft computing methods were employed consequent comparative performances of these methods were also evaluated some selected sedimentary rock types i e grainstone wackestone mudstone boundstone gypsum and silty marl collected from the qom formation in the vicinity of qom city central iran were examined four indices i e block punch index point load strength schmidt hammer rebound number and ultrasonic p wave velocity and uniaxial compressive strength ucs of these samples were determined a multidisciplinary approach including multiple linear regression analysis fuzzy inference system artificial neural network and adaptive neuro fuzzy inference system based models were used to estimate ucs from these index test results various statistical parameters vaf rmse and r 2 were determined to check the predictive performances of these models the rmse vaf and r 2 values for anfis model were 0 99 3 77 and 0 99 respectively in a comparative sense anfis gives better predictive results accordingly this method is being inferred as a predictive approach to estimate preliminary rock engineering purposes in comparison with alternate methods

stable carbon isotope record of terrestrial organic materials for the last 450 ma yr abstract the timing and magnitude of carbon isotope excursions is essential for understanding the global transfer of carbon among the oceansland and atmosphere numerous studies have focused on data collection of stable carbon isotopes 13c from marine sediments and by extension to the atmosphere but many fewer systematic studies have been conducted on land plants over long time intervals we pursued three approaches to determining stable carbon isotope trends for the past 450 ma yr from c3 plants 13cp in 5 ma yr time steps first a compilation of 6888 13cp values from ten carbon sources from the literature average 24 6 1 7 isoorg data base the second approach assumes the 13cp is controlled primarily by the 13c of atmospheric co2 13ca and subsequent isotopic fractionation from diffusion and carboxylation during photosynthesis mod1 the third approach assumes changes in atmospheric co2 concentration pco2 causes physiological driven isotopic fractionation during photosynthesis when pco2 is greater than average holocene conditions mod2 compared to isoorg and mod1 mod2 reveals lower 13cp by up to 6 during periods when pco2 is elevated as secular governors of 13cp the 13ca and pco2 are most influential when they are directional and amplify the isotopic signal despite potential influences from local and regional environmental conditions and averaging the 13cp of multiple plant sources in many of the 5 ma yr age bins ten positive carbon isotopic excursions pcies are identified in isoorg of this study most of the excursions occurred during cool to glacial conditions or ocean anoxic events one prominent negative isotopic excursion ensued from 260 to 240 ma yr which may have been a response to oxidation of light c methane outbursts volcanic eruptions or bolide impact

global increase in plant carbon isotope fractionation following the last glacial maximum caused by increase in atmospheric pco2 changes in the carbon isotope composition of terrestrial plant tissue 13c are widely cited for evidence of shifts in climate vegetation or atmospheric chemistry across a wide range of time scales a global compilation of 13c data from fossil leaves and bulk terrestrial organic matter tom spanning the past 30 k y however shows wide variability and no discernable trend here we analyze these data in terms of a relative change in net carbon isotope fractionation between the 13c value of plant tissue and that of atmospheric co2 13c 13cco2 13c 1 13c 1000 and identify a global 2 1 shift in leaf and tom 13c that is synchronous with a global rise in p co2 documented from ice core data we apply a relationship describing the effect of p co2 on 13c to the global record of 13c change documented here to reconstruct p co2 levels across the past 30 k y our reconstructed p co2 levels are in excellent agreement with the ice core data and underscore the potential of the global terrestrial 13c record to serve as an accurate p co2 proxy

paleoenvironmental implications from biomarker and stable isotope investigations on the pliocene velenje lignite seam slovenia a pliocene lignite seam up to 160 m thick occurs in the velenje basin slovenia the seam originated in a topogenous mire and evolved within a non marine transgressive setting differences in soluble organic matter yield and hydrocarbon content of borehole samples from the lignite are related to differences in the composition of free lipids of microbial origin and or hydrocarbons derived from the biogeochemical degradation of plant tissue variations of the redox conditions within the mire are reflected by pristane phytane ratios the abundance of terpenoid biomarkers indicates the predominance of gymnosperms over angiosperms which is consistent with palynomorphic spectra dominated by pollen of the sequoia taxodium metasequoia plant community rather than by angiosperms evidence is also provided that the content of land plant derived biomarkers and the preservation of plant tissue is controlled by the input of resin rich decay resistant conifers sections of the seam characterized by a high degree of gelification of humotelinite gelification index show high contents of hop 17 21 ene but low hopane concentrations the results suggest that the gelification of plant tissue may be governed by the activity of anaerobic rather than aerobic bacteria despite the minor variation in the proportions of gymnosperms versus angiosperms in the peat forming vegetation a general influence of the floral assemblage on carbon isotopic composition of the coals 13c 25 3 to 27 0 is proposed carbon cycling during biogeochemical decomposition of plant tissue by bacteria is assumed to affect the 13c value of the lignite petrographic and geochemical data of gelified and ungelified fossil wood provide evidence that gelification may be governed by microorganisms e g anaerobic bacteria different from those responsible for decreasing cellulose contents during early diagenetic aerobic degradation of wood based on the molecular composition of terpenoid biomarkers the wood fragments are identified as derived from gymnosperms the relative proportions of saturated versus aromatic hydrocarbon fractions of fossil gymnosperms display a general tendency towards lower values in gelified wood remains this indicates that bacteria involved in gelification of plant tissue may also be involved in aromatisation of diterpenoid hydrocarbons the chemotaxonomical classification of the macrofossils as gymnosperms is corroborated by the mean carbon isotopic compositions of the macrofossils 13c 24 5 and the extracted cellulose 13c 22 0 the higher isotopic difference of about 2 5 between cellulose and fossil wood compared to that found in modern trees can most probably be explained by the smaller effect of 13c discrimination for cellulose when compared with wood during decomposition chem geol 158 1999 121 compared with the coals the 13c values of wood and extracted cellulose are affected to a minor extent by microbial activity

carbon isotope fractionation during decomposition of organic matter in soils and paleosols implications for paleoecological interpretations of paleosols abstract stable isotope ratios reported as 13c of organic carbon preserved in paleosols have potential utility as a valuable paleoecological indicator if the isotopic composition of paleobiomass is preserved in the paleosol organic carbon without fractionation however soil organic matter is in a constant state of decomposition in an open system and frequently decomposes further during alteration after burial of the paleosol during this decomposition kinetic fractionation of 13c 12c in an open system results in concentration of 13c in the residual organic matter preserved in the soil and paleosol this paper summarizes studies of modern soils which show that this 13c enrichment follows a rayleigh distillation process whereby the 13c 12c ratio is a function of the natural logarithm of the fraction of remaining soil organic carbon leaving soil organic carbon 13c enriched by up to 6 with respect to the original biomass if the fraction of original biomass carbon remaining during these decomposition processes deviates significantly from 1 the soil organic carbon can be 13c enriched by several per mil and thus not a good paleoecological indicator of the 13c value of the original biomass therefore effective paleoecological studies of 13c preserved in paleosol organic carbon must therefore demonstrate that the measured concentration of organic carbon in the paleosol is near its maximum concentration during soil formation or that the paleosol organic matter does not include the 13c enriched products of microbial decomposition suggestions are made for interpreting the effects of carbon isotope fractionation of organic matter and for materials and methods most useful for paleoecological studies from bulk paleosol organic carbon

study on uniaxial compressive strength point load strength index dynamic and physical properties of serpentinites from central greece test results and empirical relations although many studies have been carried out to determine physical dynamic and mechanical properties and to establish relationships among them for several rocks only few have been focused on serpentinites determination of the mechanical properties such as uniaxial compressive strength the most fundamental property in any geotechnical work is usually difficult for these types of rocks because preparation of the standard size cores from serpentinites is quite difficult this paper presents the physical dynamic and mechanical properties investigates the relationships among them and attempts to derive reliable empirical approaches for the determination of uniaxial compressive strength formed from the above mentioned properties for serpentinites for this purpose a variety of serpentinite samples taken from the othrys and kallidromo mts central greece were tested in accordance with astm and isrm standards the same samples were subjected to petrographic studies the results were statistically described and analyzed using the method of least squares regression

estimation of uniaxial compressive strength of rock materials by index tests using regression analysis and fuzzy inference system abstract this paper presents a comparative evaluation of efficacies of different index tests and analysis techniques i e regression analyses and fuzzy inference system in predicting uniaxial compressive strength ucs of granite schist and sandstone ucs and indices such as block punch index point load strength schmidt rebound hardness ultrasonic p wave velocity and physical properties effective porosity and density were determined for the concerned rocks from simple regression analyses it was apparent that for granite and sandstone performances of all six indices are reasonably good in predicting ucs in case of granite block punch index and point load strength are the best indices whereas effective porosity point load strength and schmidt rebound hardness are the most efficient indices for sandstone in case of schist however ultrasonic p wave velocity does not seem to be a competent index unlike other indices where point load strength proves to be the best one from the critical analysis of the tests results it was demonstrated and subsequently concluded that index test results of different rock types with different geology should not be clubbed together for statistical correlation with any rock mechanical parameter like ucs both multiple regression analyses and the fuzzy inference system exhibited better predictive performances for ucs than simple regression analyses in addition to the coefficient of correlation the variance account for vaf and the root mean square error rmse were also calculated to check the predictive performances of these two models and it was found that the predictive performances of both models are comparable however one should be cautious while employing multiple regression analysis in predicting ucs as there is always a chance of cumulating plausible errors that might have remained within individual index test results on the other hand fuzzy inference system seems to be an efficient tool in predicting ucs of rock materials from indices because of its efficacy in handling uncertainties in the test results with transparency

effects of age and environment on stable carbon isotope ratios in tree rings of riparian populus abstract stable carbon isotopes of riparian tree rings are enabling improved reconstruction of past climate variability but this advance is limited by difficulty distinguishing the effects of tree age from those of climate we investigated relative influence of age and climate trends in genus populus which dominates floodplain forests in europe asia and north america we related precipitation and river flow to annual variation in stable carbon isotope ratio 13c in trees with a broad distribution of ages spanning two hundred years on the floodplain of the lightly regulated little missouri river north dakota usa we examined a total of 845 rings from seven specimens of cottonwood tree populus deltoides w bartram ex marshall ssp monilifera aiton eckenwalder cottonwood 13c decreased from pith to bark in whole wood but this trend was almost completely eliminated in purified cellulose the 13c offset between whole wood and cellulose increased from pith to bark consistent with trends of decreasing cellulose and increasing hemicellulose as a proportion of whole wood while annual ring width was correlated with monthly precipitation from april through june 13c showed strong correlations only in june and july suggesting that these complementary proxies allow resolution of seasonal variation in water availability we conclude that past climate can be reconstructed from 13c of purified cellulose from cottonwood without detrending for tree age

paleogene plants fractionated carbon isotopes similar to modern plants the carbon isotope composition 13c 13c of terrestrial plant biomarkers such as leaf waxes and terpenoids provides insights into past carbon cycling the 13c 13c values of modern plant biomarkers are known to be sensitive to climate and vegetation type both of which influence fractionation during lipid biosynthesis by altering plant carbon supply and its biochemical allocation it is not known if fractionation observed in living plants can be used to interpret fossil lipids because plant biochemical characteristics may have evolved during the cenozoic in response to changes in global climate and atmospheric co2 the goal of this study was to determine if fractionation during photosynthesis leaf leaf in the paleogene was consistent with expectations based on living plants to study plant fractionation during the paleogene we collected samples from eight stratigraphic beds in the bighorn basin wyoming usa that ranged in age from 63 to 53 ma for each sample we measured the 13c 13c of angiosperm biomarkers triterpenoids and n alkanes and abundance permitting conifer biomarkers diterpenoids leaf 13c 13c values estimated from different angiosperms biomarkers were consistently 2 lower than leaf 13c 13c values for conifers calculated from diterpenoids this difference is consistent with observations of living conifers and angiosperms and the consistency among different biomarkers suggests ancient elipidelipid values were similar to those in living plants from these biomarker based 13cleaf 13cleaf values and independent records of atmospheric 13c 13c values we calculated leaf leaf these calculated leaf leaf values were then compared to leaf leaf values modeled by applying the effects that precipitation and major taxonomic group in living plants have on leaf leaf values calculated and modeled leaf leaf values were offset by less than a permil this similarity suggests that carbon fractionation in paleogene plants changed with water availability and major taxonomic group to about the same degree it does today further paleoproxy data suggest at least two of the stratigraphic beds were deposited at times when pco2pco2 levels were higher than today biomarker data from these beds are not consistent with elevated leaf leaf values possibly because plants adapted carbon uptake and assimilation characteristics to pco2pco2 changes over long timescales

stable carbon isotopes of wood a clue to palaeoclimate abstract detailed stable carbon isotope and molecular investigations were undertaken on a number of archaeological and fossil wood specimens to provide insights into their use as rigorous independent palaeoclimatic and palaeoenvironmental parameters the isotope data revealed large differences amongst the material with the oldest specimens being least depleted in 13 c although natural variation could account for some of the observed differences the isotope values of the archaeological and tertiary specimens are most probably related to the absolute abundance of polysaccharides present and the degree of lignin alteration the molecular data based on pyrolysis of the antarctic cretaceous conifer specimens revealed only transformed lignin with virtually no intact lignin building blocks 2 methoxyphenols preserved and no evidence of polysaccharides this degree of chemical alteration is suggested here to be one of the main causes for the 13 c enriched values of these conifer specimens these results show the importance of combining detailed molecular information on individual wood components with stable carbon isotope data for palaeoclimatic and palaeoenvironmental studies

carbon cycle perturbation in the middle jurassic and accompanying changes in the terrestrial paleoenvironment abstract carbon isotope analyses of fossil wood from the middle jurassic ravenscar group yorkshire ne england reveal a significant excursion toward light isotopic values 13c change of 3 to 4 at about the aalenian bajocian boundary 174 ma a positive carbon isotopic excursion is also shown for the middle bajocian 170 ma but is less clearly defined these isotopic patterns are very similar to the few published marine carbonate records available for this time in particular one based on belemnites from the hebrides basin nw scotland and others from pelagic limestones in italy the similarity of the terrestrial and marine isotope curves is an indication that the observed isotopic signal is a global phenomenon through parts of the ravenscar group the scarborough formation supplementary data from bulk organic carbon and palynofacies analysis confirm that isotopic curves based on bulk analyses may be strongly influenced by the balance of terrestrial versus marine organic matter present in th

effects of weathering and lithology on the quality of aggregates in the alluvial fans of northeast rivand sabzevar iran alluvial fans as depositional landforms can be considered as potential sources of aggregates as the age of alluvial fans increases their constituent sediments are exposed to longer periods of weathering and increased mineral alteration resulting in a decrease in aggregate quality in this study physical properties and point load tests were used to assess the aggregate quality on three alluvial fan surfaces relict old and young in the northeastern part of rivand village in west of sabzevar northeast iran differentiating young from old and relict fans was carried out based on geomorphic criteria such as weathering features fan surface morphology and drainage pattern the young alluvial fan is characterized by sub rounded and unvarnished clasts distributary drainage patterns and a relatively flat surface whereas old and relict fans are characterized by incised and rough surfaces tributary drainage pattern and highly weathered and varnished clasts due to their long term exposure to weathering due to a range of rock types occurring across each fan surface lithological studies were performed to eliminate the effect of lithology on aggregate quality a total of 18 rock types comprising comparable lithologies were sampled from each of the three alluvial fans results show that in almost all 18 rock types the point load test values increases from relict to young fans whereas porosity and percentage of water absorption decrease implying that aggregate quality decreases with time as a function of duration of exposure to weathering also the strength of aggregates in all three fans decreases from the fan apex to the fan toe data show that micaceous intrusive igneous rocks tuffs with high porosity and fine grained extrusive igneous rocks with some porosity are more sensitive to physical weathering and therefore have lower strength particularly on the relict and old fans overall variations in aggregate strength on these fans can be attributed to the relative ages of fans with relict and old fans containing lower quality aggregates due to the longer term exposure to weathering

a summertime rainy season in the arctic forests of the eocene the discovery of exceptionally well preserved fossil wood revealed that extensive forests existed north of the arctic circle during the eocene ca 45 55 ma subsequent paleobotanical studies led researchers to suggest eastern asia as a modern analog based on the distribution of nearest living relatives during the last decade proxy based reconstructions of mean annual paleoprecipitation productivity and relative humidity have led workers to characterize the climate of the arctic forests as similar to today9s temperate forests of the pacific northwest using a new model we reconstructed the seasonal timing of paleoprecipitation from high resolution intra ring carbon isotope measurements of fossil wood we showed that the eocene arctic forests experienced on average 3 1 times more precipitation during summer than winter entirely dissimilar to the pacific northwest where summer precipitation is only one half to one sixth of the winter precipitation this new result shows that although mean annual climate conditions may have been similar to the mean annual conditions the pacific northwest consideration of seasonality implies that the temperate forests of eastern asia represent the best overall modern analog for the eocene arctic forests

the paleozoic to mesozoic carbon cycle revisited the carbon isotopic composition of terrestrial organic matter 1 two thousand one hundred forty eight carbon isotope values for terrestrial organic matter plant fossils coal bulk terrestrial organic matter provide a proxy record for temporal changes in the global carbon cycle 13ctom 13ccarb and 13cco2 allow a full evaluation of carbon transfer in the atmosphere ocean system as well as between the marine and the terrestrial realm the temporal evolution of 13ctom parallels respective data sets from marine carbonate carbon thus reflecting the linkage between both reservoirs via atmospheric carbon dioxide on the basis of a comparison between measured and predicted isotope records for 13ctom changes in the carbon isotopic fractionation associated with plant metabolism are discernible this contradicts the notion of an invariable carbon isotopic fractionation associated with c3 plant metabolism in light of results from current plant growth experiments these changes are viewed as dependent on the atmospheric o2 co2 hence 13ctom might serve as a proxy signal for atmospheric composition

distortion of carbon isotope excursion in bulk soil organic matter during the paleocene eocene thermal maximum the paleocene eocene thermal maximum was a period of abrupt transient global warming fueled by a large release of 13c depleted carbon and marked globally by a negative carbon isotope excursion while the carbon isotope excursion is often identified in the carbon isotope ratios of bulk soil organic matter 13corg these records can be biased by factors associated with production degradation and sources of sedimentary carbon input to better understand these factors we compared 13corg values from paleocene eocene thermal maximum rocks in the southeastern bighorn basin wyoming with those derived from leaf wax n alkanes 13c n alk while both 13c n alk and 13corg records indicate an abrupt negative shift in 13c values the carbon isotope excursions observed in bulk organic matter are smaller in magnitude and shorter in duration than those in n alkanes to explore these discrepancies we modeled predicted total plant tissue carbon isotope 13ctt curves from the 13c n alk record using enrichment factors determined in modern c3 plants measured 13corg values are enriched in 13c relative to predicted 13ctt with greater enrichment during the paleocene eocene thermal maximum than before or after the greater 13c enrichment could reflect increased degradation of autochthonous organic matter increased input of allochthonous fossil carbon enriched in 13c or both by comparing samples from organic rich and organic poor depositional environments we infer that microbial degradation rates doubled during the paleocene eocene thermal maximum and we calculate that fossil carbon input increased 28 63 this approach to untangling the controls on the isotopic composition of bulk soil carbon is an important development that will inform not only future studies of global carbon cycle dynamics during the paleocene eocene thermal maximum hyperthermal event but also any study that seeks to correlate or estimate duration and magnitude of past events using soil organic carbon

a comparison of terpenoid and leaf fossil vegetation proxies in paleocene and eocene bighorn basin sediments abstract plant derived terpenoids long recognized as biomarkers can help reveal the major taxonomic groups of land plants present in ancient environments even if rocks and sediments do not preserve plant macro or microfossils previous studies have used simple di to triterpenoid ratios to reconstruct floral changes in the geologic past but few have compared terpenoid ratios with estimates of floral composition from fossils further reconstructions have not taken into account differences in biomarker production i e concentration relative to leaf biomass between different types of plants here we have examined terpenoids from early cenozoic fluvial rocks from the bighorn basin wyoming usa where fossil flora has been studied in detail we analyzed the distributions of diterpenoids triterpenoids and n alkanes from leaf wax in a total of 43 samples from 15 stratigraphic horizons of late paleocene 63 ma to early eocene 53 ma in age in nearly all samples triterpenoids derived from angiosperms were significantly lower in abundance than conifer specific diterpenoids a finding that contrasted with plant fossil evidence for the same rocks this suggests that di to triterpenoid ratios severely underestimate the abundance of angiosperms in paleovegetation angiosperms dominated n alkane production among modern plants and we propose a new paleovegetation proxy based on the ratio of diterpenoids conifers to n alkanes angiosperms corrected for lipid production estimated from extant vegetation using diterpenoids and alkanes we infer the composition of paleovegetation to be similar to that inferred from plant fossils although the approach works well for the bighorn basin we stress the new paleovegetation proxy will need to be evaluated for other time periods communities paleogeography and depositional environments with pollen or megafossil data available