the subsidence history of conoco well 15 30 1 central north sea abstract the depth of deposition of the sediments from north sea well conoco 15 30 1 is determined using faunal and sedimentary evidence the effects of sedimentary load corrected for compaction and variations in water depth and sea level are removed to obtain the subsidence of the basement when covered by water only a crustal stretching and lithospheric thinning of 25 35 1 35 can account for both the initial fault controlled subsidence and the later uniform subsidence

volume and velocity changes at mittivakkat gletscher southeast greenland we document changes for mittivakkat gletscher the peripheral glacier in greenland with the longest field based observed mass balance and surface velocity time series between 1986 and 2011 this glacier changed by 15 in mean ice thickness and 30 in volume we attribute these changes to summer warming and lower winter snow accumulation vertical strain compensated for 60 of the elevation change due to surface mass balance smb in the lower part and 25 in the upper part the annual mean ice surface velocity changed by 30 which can be fully explained by the dynamic effect of ice thinning within uncertainty mittivakkat gletscher summer surface velocities were on average 50 60 above winter background values and up to 160 higher during peak velocity events peak velocity events were accompanied by uplift of a few centimeters

estimating response times of vadret da morteratsch vadret da palu briksdalsbreen and nigardsbreen from their length records length records of two pairs of glaciers are used to reconstruct the equilibrium line altitude ela and to estimate glacier response times the method is based on the assumption that neighbouring glaciers should be subject to the same climatic forcing and that differences in the length records are thus caused by differences in response times and climate sensitivities by means of a control method in which the difference between the reconstructed histories of the ela is minimized realistic response times are found the pairs of glaciers studied are i vadret da morteratsch and vadret da paluin the swiss alps and ii briksdalsbreen and nigardsbreen in southern norway in both cases the reconstructed ela histories of the individual glaciers are very similar in spite of the large differences in the length records short e folding response times are found for the steep glaciers 4 4 years for vadret da palii 5 0 years for briksdalsbreen for the larger glaciers with a more gentle slope the response times are substantially larger 33 0 years for vadret da morteratsch 34 8 years for nigardsbreen

the rasc method for ranking and scaling of biostratigraphic events abstract the rasc method for ranking and scaling of biostratigraphic events was developed by the authors and associates during the past 20 years the purpose of ranking is to create an optimum sequence of events observed in different wells or sections subject to stratigraphic inconsistencies in the direction of the arrow of time these inconsistencies which result in crossovers of lines of correlation between sections are due to various sampling errors and other sources of uncertainty including reworking and misclassification they can be resolved by statistical averaging combined with stratigraphic reasoning subsequent scaling of the events can be carried out by estimating intervals between successive events along a relative time scale this results in the scaled optimum sequence either the ranked optimum sequence or the scaled optimum sequence can be used for biozonation and for correlation between sections with error bars to denote precision of the correlation the observed positions in the sections of different biostratigraphic events can have different degrees of precision these differences can be evaluated by analysis of variance other types of stratigraphic events including logmarkers can be integrated and incorporated with the biostratigraphic events the purpose of this review paper is to provide a succinct description of rasc as it is today using the cretaceous microfossil example of gradstein et al gradstein f m kaminski m a agterberg f p 1999 biostratigraphy and paleoceanography of the cretaceous seaway between norway and greenland earth science reviews for illustration

instruments and methods glaciological and volumetric mass balance measurements error analysis over 51 years for glacier de sarennes french alps the mass balance of glacier de sarennes french alps has been measured since 1949 using the glaciological method based on core and ablation stake data and area extrapolations to find the overall glacier balance the cumulative balance obtained in this way is very dependent on systematic errors that can increase linearly with the number n of measurement years whereas random errors rise with the volumetric balance method based on aerial photogrammetry provides results whose errors do not depend on the number of years this method was used to test field measurements for the period 1952 2003 and gives a mass balance of 32 30 1 04 m w e compared to 34 89 1 15 m w e based on field data the discrepancy between the two methods is discussed on the basis of a careful error analysis moreover the possibility of using the volumetric method to detect biases in field measurements is evaluated in terms of two types of errors the number and locations of measurement sites required to account for all the spatial and temporal variabilities of the mass balance is discussed by variance analysis methodological implications and recommendations are presented to provide mass balance measurements of the best possible accuracy

from balance to imbalance a shift in the dynamic behaviour of chhota shigri glacier western himalaya india mass balance and dynamic behaviour of chhota shigri glacier have been investigated between 2002 and 2010 and compared to data collected in 1987 1989 during the period 2002 2010 the glacier experienced a negative glacier wide mass balance of 0 67 0 40 m a w e between 2003 and 2010 elevation and ice flow velocities are slowly decreasing in the ablation area leading to a 24 to 37 reduction in ice fluxes an expected response of the glacier dynamics to its recent negative mass balances the reduced ice fluxes still remain far larger than the balance fluxes calculated from the year 2002 to 2010 average surface mass balances therefore further slow down thinning and terminus retreat of chhota shigri glacier are expected over the next years conversely the 2003 2004 ice fluxes are in good agreement with ice fluxes calculated assuming that the glacier wide mass balance is zero given the limited velocity change between 1987 1989 and 2003 2004 and the small terminus change between 1988 and 2010 we suggest that the glacier has experienced a period of near zero or slightly positive mass balance in the 1990s before shifting to a strong imbalance in the 21st century this result challenges the generally accepted idea that glaciers of western himalaya have been shrinking rapidly for the last decades

sliding velocity fluctuations and subglacial hydrology over the last two decades on argentiere glacier mont blanc area the subglacial observatory beneath the argentiere glacier provides a rare opportunity to study the interactions between glacier sliding velocity and subglacial runoff the sliding velocity has been monitored in this cavity almost continuously since 1997 and the resulting data indicate a decrease in annual sliding velocities over the last two decades we found close relationships between annual surface velocity sliding velocity and ice thickness these relationships indicate that the ice flow velocity changes do not depend on subglacial water runoff changes at the annual timescale the seasonal magnitudes of sliding also show a decrease over the last two decades at the seasonal timescale sliding velocity increases before or simultaneously with the large runoff increase in may indicating a distributed drainage system conversely at the end of the melt season sliding velocity continues to decrease after the runoff returns to low winter values the simultaneous increases of runoff and sliding velocity occur mainly before the spring transition later sliding velocity generally appears not to be related to water inputs coming from the surface except for some large accelerations after midaugust that are always associated with periods of rapidly increasing water inputs to the subglacial drainage system

biostratigraphy and paleoceanography of the cretaceous seaway between norway and greenland abstract the narrow seaway between greenland and norway in cretaceous time was over 1500 km long and 300 km wide and partly of bathyal water depth during aptian through campanian it received a large volume of fine grained siliciclastic sediments with intercalated gravity flow sandstone wedges as a conduit for heat transport between the low latitudes and polar region atlantic watermasses particularly affected the eastern norwegian margin of this seaway despite its high latitude setting calcareous and few siliceous planktonic microfossils thus play an important role in regional stratigraphy and facies analysis and a majority of fossil events correlate to nw european basins the eastern margin sedimentary succession may be subdivided in several broad lithologic units 1 thin multicolored marly sediments of hauterivian barremian age with a shallow marine falsogaudryina nodosariid ostracod assemblage 2 dark mudstones and minor sands aptian early cenomanian in age with an upper bathyal agglutinated assemblage and monotypic hedbergella floods 3 thick mudstone facies with thin slope apron turbidite sands and an impoverished benthic planktonic assemblage of late cenomanian coniacian age deposited in an upper bathyal oxic dysaerobic environment where turonian sedimentation rates are low a planktonic foraminiferal assemblage with whiteinella hedbergella dicarinella and marginotruncana occurs 4 grayish laminated mudstones santonian campanian in age with local sands in the north a low diversity middle to upper bathyal benthic planktonic foraminiferal assemblage and an inoceramus prisms and radiolarian diatom flood a campanian agglutinated foraminiferal bloom also is known from the atlantic oceanic realm 5 more marly sediments of maastrichtian age with a low diversity planktonic benthic foraminiferal assemblage using the distribution of 1755 foraminiferal and dinoflagellate microfossil events in over 30 exploration wells a rasc ranking and scaling probabilistic zonation served as a template to build a cretaceous zonal model with 19 assemblage and interval zones including over 100 events variance analysis ranks 72 events according to reliability in correlation three new index taxa include uvigerinammina una and ammoanita globorotaliaeformis albian and fenestrella bellii campanian widespread planktonic flood events occur in late albian through early cenomanian early mid turonian late santonian earliest campanian and mid maastrichtian the result of northwards shifts of warmer water masses and disruptions in water stratification in the dysaerobic basins an earliest cretaceous hiatus separates jurassic from cretaceous strata ongoing block faulting coupled to thermal subsidence and global sealevel rise increased water depth in aptian albian time from neritic to bathyal and created sand accommodation space in dysaerobic restricted settings in cenomanian coniacian time sedimentation rates in the central basin increased 10 fold whereas paleo waterdepth did not deepen this relatively brief less than 10 m y tectonic episode resulting in deposition of deep water sands is tentatively linked to stress re orientation in the rockall area a widespread upper maastrichtian danian hiatus the result of shoulder uplift reflects break up prior to the onset of paleogene seafloor spreading in the norwegian sea

long term change of mass balance and the role of radiation the effect of climate change in the 20th century is investigated based on measured mass balance data annual winter and summer mass balances on claridenfirn switzerland since 1914 15 storglaciaren sweden since 1945 46 storbreen norway since 1948 49 glacier de sarennes france since 1948 49 and vernagtferner austria since 1965 66 are studied with air temperature at high altitude stations and the longest records of solar global radiation in europe the mean mass balances of these glaciers during the 20th century were mostly negative except for the first two decades the fluctuating mass balance reaches the minimum largest loss and maximum almost equilibrium around 1940 and 1980 respectively with a drastic loss in the last 15 years these variations are mostly steered by the variation in summer mass balance the change in the summer mass balance is determined to 72 by temperature and the remaining 28 by solar radiation during the colder period e g 1960 80 the reduction in solar radiation counteracted the warming trend due to the greenhouse effect since 1990 the greenhouse effect of terrestrial radiation and the global brightening effect of solar radiation have both been acting to accelerate the melt resulting in the unprecedented mass loss of the observational era the glacier mass balance during the 20th century clearly reacted towards temperature and solar radiation changes which reflected the greenhouse effect and aerosol and cloud variations

on estimating length fluctuations of glaciers caused by changes in climatic forcing the reaction of alpine glaciers to shifts in the equilibrium line altitude ela is calculated by using a two dimensional numerical model to solve the full equations for the velocity and stress fields full system model in the absence of basal motion rates of advance and retreat of the snout of typically sized alpine glaciers are found to be insensitive to the details of the flow at the snout even when the glaciers are far from steady state a comparison of results obtained with a full system model and a shallow ice approximation sia model yields no significant differences in advance or retreat rates this assumption has been implicitly made in numerous previous climatic studies and is here shown to be well justified using a realistic mass balance altitude feedback only slight model dependent changes in steady state lengths are found the relative importance of mass balance and glacier dynamics for the transient response of alpine glaciers to changes in the ela is given a precise meaning by determining the model dependent additional shifts in ela needed for the sia and the full system models to produce identical changes in length for alpine glaciers these additional shifts in ela are on the order of 10 m which is within the error range of ela estimates it follows that at least in the absence of significant basal motion there is no need to include the effects of horizontal stresses when calculating the reaction of alpine glaciers to climatic changes attention should focus on accurate determination of the mass balance distribution and model tuning to give realistic ice thickness distributions

future fluctuations of mer de glace french alps assessed using a parameterized model calibrated with past thickness changes simulations of glacier evolution are needed to assess future changes in the runoff regime of mountain catchments a simplified parameterized model is applied here to simulate future thickness changes and glacier retreat of mer de glace french alps a normalized thickness change function describing the spatial distribution of surface elevation changes as a function of elevation has been determined the model reveals that under present climatic conditions mer de glace will continue to shrink dramatically in the coming decades retreating by 1200 m between now and 2040 the method has certain limitations related to the uncertainties of the normalized function based on thickness change data an error of 10 in the normalized function leads to uncertainties of 46 30 and 18 in mer de glace front surface area and glacier wide mass balance changes respectively in 2040 because the difference of the normalized function largely exceeds 10 from one glacier to another even within a given glacier size class and elevation range it would be very risky to extrapolate the normalized function to unmeasured glaciers consequently the method is applicable only on glaciers where past surface elevation changes are well constrained

dynamic behaviour analysis of glacier de saint sorlin france from 40 years of observations 1957 97 mass balance and dynamic measurements carried out on glacier de saint sorlin since 1957 provide a good opportunity to study the dynamics of this glacier ice flow analysis shows that dynamic changes have been important over the last 40 years and that these changes are not consistent with the concepts usually used in glacier modelling present velocities are larger than the 1960 velocities although the thickness decreased everywhere 10 30 m in the ablation zone a simple numerical ice flow model which does not include longitudinal stress gradients has been used to investigate these phenomena this model allows us to infer the sliding velocity from observed surface and calculated deformation velocities we conclude that 1 the sliding velocity cannot be described by weertman analysis or empirical relations which link the sliding to the thickness and surface slope 2 the inferred sliding velocity is uniform over at least half of the glacier and 3 there is no clear link between the sliding process and the quantity of water coming from surface ablation furthermore it may not be reasonable to calibrate model flow parameters from geometry changes because the surface geometry is relatively insensitive to velocity changes over some decades

improvement of a 2 d sia ice flow model application to glacier de saint sorlin france a number of improvements have been made to an existing two dimensional ice flow model applied to an alpine glacier analysis of the results of the existing model revealed several shortcomings the first concerns the lack of mass conservation of the applied alternating direction implicit adi scheme a semi implicit si scheme is therefore proposed and the effects on mass conservation assessed by a comparison with the adi scheme the comparison is first carried out with a simple theoretical glacier for which the improvement is significant concerning the real case of glacier de saint sorlin france the initial deviation in mass conservation was much less pronounced such that the new scheme although improving mass conservation does not significantly change the modelled dynamics however other shortcomings that have a more profound impact on the modelling of glacier behaviour have been identified the ice thickness may become negative over some gridpoints leading to an inconsistency the problem is partly resolved by incorporating extra checks on critical gridpoints at the glacier border finally with the help of ice particle tracking unrealistic ice settlement above the bergschrund has been identified as the main reason for spurious dynamic effects and has been corrected

quantitative biostratigraphy achieving finer resolution in global correlation abstract the fossil record preserves a wide range of events that might be used to build timescales and correlate strata from place to place the events include the originations and extinctions of species the occurrence of distinctive faunal assemblages magnetic field reversals changes in ocean chemistry and volcanic ash falls the fundamental task is to determine the global sequence of all these events modern computer algorithms can build high resolution timescales by sequencing and calibrating thousands of such events from hundreds of localities each successful sequencing algorithm can be understood in terms of a simple two dimensional visual device graphic correlation permutable sequences permutable matrices and slotting devices are each suited to a different data problem such as contradictory evidence of sequence a lack of information about sequence or uncertain correspondence of events algorithms based upon permutable sequences and evolutionary programming heuristics have the flexibili

spatio temporal changes in glacier wide mass balance quantified by optical remote sensing on 30 glaciers in the french alps for the period 1983 2014 remote sensing is a powerful method to reconstruct annual mass balance series over past decades by exploiting archives of available images as well as to study glaciers in inaccessible regions we present the application of a methodological framework based only on optical satellite images to retrieve glacier wide annual mass balances for 30 glaciers in the french alps the glacier wide annual mass balance for the period 1983 2014 was reconstructed by combining changes in glacier volumes computed from remote sensing derived dems with annual measurements of the snow line altitude on satellite images data from direct observations on two of the glaciers confirmed the accuracy of the annual mass balances quantified by remote sensing with an average difference of 0 3 m w e within the uncertainty range of the methods our results confirm the significant increase in mass loss since the early 2000s with a difference 1 m w e a 1 between the periods 1983 2002 and 2003 14 the region wide mass balance for the french alps over the period 1979 2011 was 0 66 0 27 m w e a 1 close to that of the european alps we also show that changes in glacier surface area or length are not representative of changes in mass balance at the scale of a few decades

basal icequakes recorded beneath an alpine glacier glacier d argentiere mont blanc france evidence for stick slip motion while basal icequakes associated with glacier motion have been detected under antarctica for several decades there remains very little evidence of stick slip motion for alpine glaciers here we analyzed 2357 basal icequakes that were recorded at glacier d argenti ere mont blanc massif between february and november of 2012 and that are likely to be associated with basal sliding these events have been classified into 18 multiplets based on their waveforms the strong similarity of the waveforms within each multiplet suggests an isolated repeating source despite this similarity the peak amplitude within each multiplet varies gradually in time by up to a factor of 18 the distribution of these events in time is relatively complex for long time scales we observe progressive variations in the amplitudes of events within each multiplet for intermediate time scales hours the events occur regularly in time with typical return times of several minutes up to several hours for short time scales from 0 01 to 100 s the largest multiplet shows clus tering in time with a power law distribution of the interevent times the location of these events and their focal mechanisms are not well constrained because most of these events were detected by a single seismometer nevertheless the locations can be estimated with an accuracy of a few tens of meters using a polarization analysis the estimated average depth of the basal events is 179 m which is in good agreement with the estimated glacier thickness the relative changes in distance between the source and the sensor can be measured accurately by correlating separately the p wave and s wave parts of the seismograms of each event with the template waveforms which are obtained by averaging the signals within each multiplet we observed small variations in the times between the p wave and the s wave of up to 0 6 ms over 50 days these variations cannot be explained by displacement of the sensor with respect to the glacier but might be due to small changes in the seismic wave velocities with time finally we found using numerical simulations that the observed signals are better explained by a horizontal shear fault with slip parallel to the glacier flow than by a tensile fault these results suggest that the basal events are associated with stick slip motion of the glacier over rough bedrock the rupture length and the slip are difficult to estimate nonetheless the rupture length is likely to be of the order of meters and the total seismic slip accumulated over one day might be as large as the glacier motion during the most active bursts

neogene biochronology of antarctic diatoms a comparison between two quantitative approaches conop and uagraph abstract a quantitative biochronological study by cody et al 2008 integrates comprehensive diatom biostratigraphy magnetostratigraphy and tephrostratigraphy from 32 neogene sections around the southern ocean and antarctic continental margin a recent method known as constrained optimization conop which can be viewed as a multidimensional version of graphic correlation is applied to that very interesting database the goal of the present paper is to discuss some theoretical aspects of quantitative biochronology and to compare the constrained optimization with the deterministic method called unitary associations uam a graph theoretical model we illustrate the fact that the uam is an extremely powerful and unique theory allowing an in depth analysis of the internal conflicting inter taxon stratigraphic relationships inherent to any complex biostratigraphical database

solving the paradox of the end of the little ice age in the alps 1 the causes and timing of the little ice age fifteenth to nineteenth centuries are still unclear crowley 2000 bond et al 2001 shindell et al 2001 during the last part of this event 1760 1830 the advance of glaciers in the alps conflicts with the summer temperature signal intergovernmental panel on climate change 2001 this paper attempts to solve this paradox from glacier fluctuations and monthly temperature data we show that mean winter precipitation was higher by at least 25 during this final phase compared to the twentieth century average and that glacier recession after 1830 clearly resulted from a winter precipitation decrease and not a temperature increase conversely since the beginning of the twentieth century glacier changes have been driven mainly by temperature change

editorial rich geo and bio diversities exist in the south west atlantic deep sea the first human occupied submersible shinkai 6500 dive cruise iata piuna

insights on why graphic correlation shaw s method works in 1964 a b shaw presented a method of correlating fossiliferous sedimentary rocks based on interpretation of graphic plots of first and last occurrences of taxa because there is no way to determine the true total ranges of fossil taxa it is instructive to test the accuracy of the method using hypothetical datasets the dataset used here consists of 16 taxa in six sections with differing known rates of rock accumulation in all graphs a single straight line correlation was a reasonable interpretation the resulting ranges after the first and third rounds of compositing reproduce the true ranges but with small errors slight errors in the positioning of individual correlation lines are more likely to lengthen ranges artificially than to shorten them shaw s method works well because whereas actually sampled ranges will be shorter than true ranges errors in correlation will be likely to extend some ranges this or any exercise using simulated data is useful only if the hypothetical situation resem

quantitative determination of tertiary sediment supply to the north sea basin sediment supply comprises a major family of regime variables that influence geomorphic surface grade spatial and temporal changes in total sediment supply and sediment texture gravel sand mud ratio will cause reconfiguration of depositional and erosional profiles potentially creating or influencing the sequence stratigraphic framework of the basin sequence grain volume which is defined as the volume of sedimentary grains in an individual stratigraphic sequence total sequence volume minus cement and porosity volume has been quantitatively determined for each of 16 genetic stratigraphic sequences in the north sea basin rates of total sediment supply to the basin in both time and space were then calculated sand grain volume and sand mud ratio were also calculated for each sequence these data define four principal episodes of tertiary sediment supply the most significant episode occurred in the late paleocene and was followed by secondary episodes in the eocene and oligocene a fourth neogene episode extends through the present all episodes correlate to source terrain tectonic pulses related to evolution of the north atlantic basin to intraplate stress changes associated with successive phases of the alpine orogeny or to the late cenozoic epeirogenic uplift of scandinavia the major episodes in turn contain secondary sequence to sequence variations that correspond to changes in spatial or temporal values of one or both of the supply regime variables again most changes closely reflect details within the histories of the principal tectonic phases the history of changing source area relief and resulting topographic grades and related changes in sediment yield into the basin was a principal control on north sea cenozoic sequence development source basin relief in turn was largely determined by regional tectonism

multi decadal ice velocity and elevation changes of a monsoonal maritime glacier hailuogou glacier china digital elevation models dems of the ablation area of hailuogou glacier china produced from advanced spaceborne thermal emission and reflection radiometer aster data obtained in 2009 differential gps dgps data surveyed in 2008 and aerial photographs acquired in 1966 and 1989 are differenced to estimate long and short term glacier surface elevation change dh dt the mean dh dt of the ablation area over 43 years 1966 2009 is 1 1 0 4 m a 1 since 1989 the thinning has accelerated significantly ice velocities measured by dgps at 28 fixed stakes implanted in the ablation area increase with distance from the glacier terminus ranging from 41 0 m a 1 approaching the glacier terminus to a maximum of 205 0 m a 1 at the base of an icefall our results reveal that the overall average ice velocity in the ablation area has undergone significant temporal variability over the past several decades changes in glacier surface elevation in the ablation area result from the combined effects of climate change and glacier dynamics which are driven by different factors for different regions and periods

sensitivity of mass balance and equilibrium line altitude to climate change in the french alps assessment of the sensitivity of surface mass balance and equilibrium line altitude ela to climate change is crucial for simulating the future evolution of glaciers such an assessment has been carried out using an extensive dataset comprising numerous measurements of snow accumulation and snow and ice ablation made on four french glaciers over the past 16 years winter mass balance shows a complicated pattern with respect to altitude with no clear linear relationship although the ratios of winter mass balance to valley precipitation differ considerably from site to site they are relatively constant over time relationships between snow ice ablation and temperature are stable with no link with altitude the mean snow and ice positive degree day pdd factors are 0 003 and 0 0061 m w e c 1 d 1 this analysis shows that at a given site ablation depends mainly on the amount of snow precipitation and on cumulative pdds the sensitivity of annual ablation to temperature change increases almost linearly from 0 25 m w e c 1 at 3500 m to 1 55 m w e c 1 at 1650 m ela sensitivity to temperature change was found to range from 50 to 85 m c 1

multi method monitoring of glacier d argentiere dynamics the flow of glacier d argentiere french alps has been extensively studied by glaciologists for 100 years but high temporal and high spatial resolution monitoring of its dynamics has rarely been carried out in this paper the terminal part of the main glacier was selected to undertake such a survey the 2 month experiment september november 2013 included remote sensing to map the velocity field of the whole area and a network of in situ measurements to record the ice velocity at the surface as well as at the base of the glacier with high precision and at high temporal resolution these monitoring methods are combined to produce a comprehensive and reliable picture of the ice flow basal and surface in situ measurements are used to precisely monitor the temporal variability of the ice flow at a section of the glacier where crevassed areas and non cracked ice coexist the achieved results are an innovative and efficient tool to investigate the acceleration deceleration pattern heterogeneities in ice flow that occur after heavy rainfall

quantifying the community turnover of the uppermost wenlock and ludlow silurian conodonts in the baltic basin abstract the homerian to ludfordian interval of the mid to late silurian period was a time of significant changes in conodont communities global climate oceanographic patterns and biogeochemical cycles the mulde and the lau events are preeminent examples of globally recognized conodont extinction episodes from this interval in earth s history the silurian baltic basin is the most suitable locality globally for studying these perturbations to the ocean atmosphere system since there is an extensive record of conodont taxa occurrences their communities and their environments spanning across shore face to open ocean settings in this study we present new conodont and 13c data from the upper homerian to ludlow interval from two core sections g luva 99 and g luva 118 representing shelfal environments and the numerical conodont data from the vidukl 61 section from deep water settings and compare them with patterns of conodont diversity change as revealed in the data rich milaiciai 103 core section for this purpose we explored the stratigraphically tied time series of conodont diversity changes employing recurrence and cross recurrence plots the binary similarity matrices that are used for deciphering complex spatial and temporal dynamic patterns the cross recurrence plots were used as a means of synchronizing the geological sections by applying dynamic time warping and the newly described moving window median recurrence point search algorithms the results revealed that the conodont community compositional data are sufficiently temporally and spatially coherent to be reasonably used for synchronizing geological records moreover the sudden state transitions detected in the cross recurrence plots suggest that the lau event was of great importance for conodont community evolution in the studied time slice

common climatic signal from glaciers in the european alps over the last 50 years conventional glacier wide mass balances are commonly used to study the effect of climate forcing on glacier melt unfortunately the glacier wide mass balances are also influenced by the glacier s dynamic response investigations on the effects of climate forcing on glaciers can be largely improved by analyzing point mass balances using a statistical model we have found that 52 of the year to year deviations in the point mass balances of six glaciers distributed across the entire european alps can be attributed to a common variability point mass balance changes reveal remarkable regional consistencies reaching 80 for glaciers less than 10 km apart compared to the steady state conditions of the 1962 1982 period the surface mass balance changes are 0 85 m water equivalent w e a 1 for 1983 2002 and 1 63 m w e a 1 for 2003 2013 this indicates a clear and regionally consistent acceleration of mass loss over recent decades over the entire european alps

global dynamics of a temperate valley glacier mer de glace and past velocities deduced from forbes bands transverse profiles and velocities which have been measured on the ablation zone of mer de glace more or less continuously since 1891 contradict the weertman nye theory of glacier kinematic waves faint broad waves which undoubtedly result from fluctuations in the balance travel down the glacier faster than this theory predicts this theory having first been completed by taking changes in width with time and with distance down the glacier into account on the other hand velocity fluctuations are synchronous and more or less the same over the entire length studied 6 km these discrepancies result from bottom friction being of the solid type i e independent of sliding velocity friction should also be almost insensitive to discharge in subglacial waterways since in the steady state energy for keeping them open not entirely flooded and at atmospheric pressure is superabundant the sliding velocities at all cross profiles are thus controlled by some areas where the body of the glacier suffers strong deformation because the valley shape is far from cylindrical one such controlling zone exists on mer de glace owing to the existence of a subglacial transverse shoulder a new perturbation equation and a new rough expression for wave velocity are given intervals between forbes bands were plotted on seven aerial surveys between 1939 and 1979 progressive tilting of the slices of blue dusty ice from the position from which these dark bands proceed and progressive lowering of their exposed edge must be taken into account this analysis confirms the validity of our simple model for velocity fluctuations and allows us to estimate the entire series since the year 1888

ice ablation as evidence of climate change in the alps over the 20th century 1 over fifty years of cumulative annual mass balance data for several glaciers in the alps shows similar fluctuations which seem to provide evidence of a common climatic signal separate winter and summer mass balance measurements from the claridenfirn glacier in switzerland since 1914 and the sarennes glacier france since 1949 show that 1 the annual mass balance is primarily driven by the summer mass balance term and 2 melting rate variations with time are very similar for these two glaciers located 290 km apart the increase in the ablation rate of 0 5 cm w e day 1 between the two periods 1954 1981 and 1982 2002 over these two glaciers corresponds to a 20 wm 2 rise in the energy flux at the glacier surface these results suggest that a common summer melting rate change may have affected the alps as a whole detailed observations on the sarennes glacier show that the origin of this strong increase in summer ablation since 1982 is not only a rise in the summer melting rate but also an increase in the ablation period during the months of september and october

twenty first century glacier slowdown driven by mass loss in high mountain asia glaciers in high mountain asia have experienced heterogeneous rates of loss since the 1970s yet the associated changes in ice flow that lead to mass redistribution and modify the glacier sensitivity to climate are poorly constrained here we present observations of changes in ice flow for all glaciers in high mountain asia over the period 2000 2017 based on one million pairs of optical satellite images trend analysis reveals that in 9 of the 11 surveyed regions glaciers show sustained slowdown concomitant with ice thinning in contrast the stable or thickening glaciers of the karakoram and west kunlun regions experience slightly accelerated glacier flow up to 94 of the variability in velocity change between regions can be explained by changes in gravitational driving stress which in turn is largely controlled by changes in ice thickness we conclude that despite the complexities of individual glacier behaviour decadal and regional changes in ice flow are largely insensitive to changes in conditions at the bed of the glacier and can be well estimated from ice thickness change and slope alone changes in glacier speed in high mountain asia are closely linked to mass balance through gravitational driving stress and largely insensitive to basal conditions according to satellite derived ice flow observations

probabilistic correlation of single stratigraphic samples a generalized approach for biostratigraphic data existing quantitative methods for biostratigraphic dating and correlation commonly ignore one of the key strengths of the microfossil record relative abundance data in this study we present a maximum likelihood based biostratigraphic method that demonstrates how microfossil abundance can be used in the stratigraphic placement of isolated samples precise correlation and dating of isolated paleontological samples is not possible with current methods which are primarily intended for the alignment of longer stratigraphic sequences in contrast the probabilistic approach provided by likelihood analysis results in sample age estimates with defined confidence intervals therefore all the uncertainties inherent in our age assessment resulting from small sample sizes incomplete sampling imperfect knowledge of stratigraphic distributions lack of taxonomic resolution of biostratigraphic data and underlying environmental paleogeographic and sedimentologic processes are explicit in our results we conclude with a field test of the method from data collected from an oil well from the catatumbo basin colombia illustrating the use of our approach in a real world case study and highlighting how our method could be generalized to a wide range of stratigraphic problems

using remote sensing data to determine equilibrium line altitude and mass balance time series validation on three french glaciers 1994 2002 alpine glaciers are very sensitive to climate fluctuations and their mass balance can be used as an indicator of regional scale climate change here we present a method to calculate glacier mass balance using remote sensing data snowline measurements from remotely sensed images recorded at the end of the hydrological year provide an effective proxy of the equilibrium line mass balance can be deduced from the equilibrium line altitude ela variations three well documented glaciers in the french alps where the mass balance is measured at ground level with a stake network were selected to assess the accuracy of the method over the 1994 2002 period eight mass balance cycles results obtained by ground measurements and remote sensing are compared and show excellent correlation r 2 0 89 both for the ela and for the mass balance indicating that the remote sensing method can be applied to glaciers where no ground data exist on the scale of a mountain range or a given climatic area the main differences can be attributed to discrepancies between the dates of image acquisition and field measurements cloud cover and recent snowfalls constitute the main restrictions of the image based method

geohistory analysis of bombay high region abstract geohistory diagrams have been constructed for three representative sites in the bombay high region offshore west coast india the model curve for 60 lithospheric injection matches the intitial part of a thermo tectonic curve for one of the sites where a complete tertiary sequence is developed the study suggests that the four paleogene unconformities recognised in this region were caused by eustatic falls a distinct phase of active subsidence occurred during the late middle late miocene probably due to more active spreading at the mid indian ocean ridge

the 3d microscopic signature of strain within glacial sediments revealed using x ray computed microtomography abstract x ray computed microtomography ct a non destructive analytical technique was used to create volumetric three dimensional 3d models representing the internal composition and structure of undisturbed pro and subglacial soft sediment sample plugs for the purposes of identifying and analysing kinematic indicators the technique is introduced and a methodology is presented addressing specific issues relating to the investigation of unlithified polymineralic sediments six samples were selected based on their proximity to type brittle and ductile deformation structures or because of their perceived suitability for successful application of the technique analysis of a proglacial ideal specimen permitted the 3d geometry of a suite of micro faults and folds to be investigated and the strain history of the sample reconstructed the poor contrast achieved in scanning a diamicton of glaciomarine origin is attributable to overconsolidation under normal loading the sediment demonstrated to have undergone subsequent subglacial deformation another overconsolidated diamicton contains an extensive small scale the subglacial sample evidence indicates that complex polyphase brittle ductile deformation histories are common in such diamictic soft sediments and that the local micro scale environment composition structure shear forces and effective pressure controls rheology the sediment void ratio is a key indicator of strain three of the samples are tentatively placed at different points on the strain cycle for subglacially deforming soft sediment based on their void ratio characteristics and distribution it has been demonstrated that ct offers significant potential for elucidating glacial soft sediment kinematics the ability of the technique to both test a variety of hypotheses pertaining to mechanisms operating within the subglacial environment and evaluate efforts to replicate those processes under controlled laboratory conditions is therefore discussed along with solutions to the problems encountered within this project ct also permits the seamless linking of analytical techniques applied at the hand specimen mm micromorphological m mm scanning electron microscopy and x ray diffraction fluorescence nm m scales and the archiving duplication and dissemination of sample volumetric 3d data

recent developments in quantitative stratigraphy abstract during the past 10 years about 150 scientists in 25 countries have collaborated under the auspices of the international geological correlation programme project no 148 evaluation and development of quantitative stratigraphical correlation techniques this paper reviews mathematical methods of stratigraphical correlation mainly in biostratigraphy but also in chronostratigraphy and lithostratigraphy sequencing methods treat the relative order of stratigraphic events such as the highest occurrences of fossil taxa as observed in many sections intervals between successive events in an ordered sequence can be estimated and the results expressed in linear time if a subgroup of the stratigraphical events can be dated recently such methods have been used to develop a new deep water benthic foraminiferal zonation for the cenozoic strata of the central and viking grabens north sea several regional hiatuses of 2 to 5 m y in duration can be recognized and matched to changes in sea level the same methods have been used for automated isochron contouring with error bars in depth or time units in cenozoic and cretaceous basins off eastern canada such information may be used for automated basin history analysis time successive assemblages of fossils can be established by using multivariate methods applied to co occurrences of events or by the method of unitary associations in conjunction with graph theory on the overlap of stratigraphical ranges other methods for stratigraphical correlation reviewed in this paper include the composite standard method and estimation of the age of chronostratigraphical boundaries using maximum likelihood and cubic spline interpolations attractions of quantitative stratigraphy are the use of rigorous methodology which highlights many properties of the data the ability to handle large and complex data bases in an objective manner and statistical evaluation of the uncertainty in the results generally little conceptual orientation is required in order to use these methods and thereby gain more information from a particular dataset

mountain glacier velocity variation during a retreat advance cycle quantified using sub pixel analysis of aster images coverage of ice velocities in the central part of the southern alps new zealand is obtained from feature tracking using repeat optical imagery in 2002 and 2006 precise orthorectifica tion co registration and correlation is carried out using the freely available software cosi corr this analysis combined with short times between image acquisitions has enabled velocities to be captured even in the accumulation areas where velocities are lowest and surface features ephemeral the results indicate large velocities for mountain glaciers i e up to 5md 1 as well as dynamic changes in some glaciers that have occurred between 2002 and 2006 for the steep and more responsive fox and franz josef glaciers the speed increased at the glacier snout during the advance period while the low angled and debris covered tasman glacier showed no measurable velocity change velocity increases on the steeper glaciers are the result of an observed thickening and steepening of the glacier tongues as they moved from a retreat phase in 2002 to an advance phase in 2006 this contrasting behaviour is consistent with historic terminus position changes the steeper glaciers have undergone several advance retreat cycles during the observation period 1894 to present while the low angled glacier showed little terminus response until retreat resulting from the accelerating growth of a proglacial lake commenced in 1983

a quantitative analysis of calcareous nannofossil bioevents of the late cretaceous late cenomanian coniacian western interior seaway and their reliability in established zonation schemes abstract calcareous nannofossil assemblages from 8 localities in the upper cenomanian coniacian strata of central colorado and kansas and southern texas western interior seaway usa were analyzed to produce a new high resolution biostratigraphic framework for the greenhorn formation eagle ford formation and basal austin chalk eighteen datasets from coeval successions around the world including the global stratotype section and point gssp at pueblo co and proposed reference sections for the base of the turonian and candidate gssps for the base of the coniacian in germany poland and new mexico were incorporated from literature sources additional discussion is devoted to the basal turonian and coniacian boundaries as they reflect paleoceanographic phenomena e g oae2 widespread late turonian regression where high resolution biostratigraphy has academic as well as industrial application ranking and scaling of 48 selected bioevents produces a quantitatively derived optimum sequence of first and last occurrences scaling of events along a relative time scale reveals an 8 9 evolutionary turnover during oae2 comparison with the qualitatively developed nannofossil zonations known as the cc zonation of perch nielsen and uc zonation of burnett reveals inconsistencies largely due to the recognition of new amended species concepts discrepancies near the turonian coniacian boundary reflect changes to its placement in recent revisions to the geologic timescale a recently documented sequence of bioevents provides an accurate proxy for the boundary in the absence of the inoceramid index fossil cremnoceramus deformis erectus meek fifteen bioevents from the optimum sequence are given greater priority based on their interpreted reliability between the sections examined and the cc and uc zonations

intermediate depth icequakes and harmonic tremor in an alpine glacier glacier d argentiere france evidence for hydraulic fracturing we detected several thousand deep englacial icequakes on glacier d argentiere mont blanc massif between 30 march and 3 may 2012 these events have been classified in eight clusters inside each cluster the waveforms are similar for p waves and s waves although the time delay between the p waves and s waves vary by up to 0 03 s indicating an extended source area although these events were recorded by a single accelerometer they were roughly located using a polarization analysis the deepest events were located at a depth of 130 m 60 m above the ice bed interface the clusters are separated in space the largest cluster extends over about 100 m for this cluster the strike of the rupture plane is nearly parallel to the direction of the open crevasses and the dip angle is 56 deep icequakes occur in bursts of activity that last for a few hours and are separated by quiet periods many events occurred on 28 29 april 2012 during the warmest days when snow melting was likely important the distribution of events in time and space obeys a power law as also observed for earthquakes but with larger exponents the polarity of the p waves for all of the events is consistent with tensile faulting finally between 25 april and 3 may we observed a gliding harmonic tremor with a fun damental resonance frequency that varied between 30 hz and 38 hz with additional higher frequency harmonics during this time we also observed shallow hybrid events with high frequency onsets and a monochromatic coda these events might be produced by the propagation of fractures and the subsequent flow of water into the fracture the strongest resonance was observed just after a strong burst of deep icequakes and during an un usually warm period when the snow height decreased by 60 cm in one week the res onance frequency shows a succession of several sharp decreases and phases of progressive increases one of the strongest negative steps of the resonance frequency on 28 april coincides with a burst of deep icequakes these events appear to be associated with the propagation of fractures which can explain the decrease in the resonance frequency finally we observed an acceleration of glacier flow on 29 april and suggested that melt water had reached the ice bed interface these observations suggest that deep icequakes are due to hydraulic fracturing and that they can be used to track fluid flow inside glaciers

glacier thickening and decay analysis from 50 years of glaciological observations performed on glacier d argentiere mont blanc area france numerous glaciological data have been obtained from measurements carried out on glacier d argentiere mont blanc area france since the beginning of the 20th century moreover data on annual mass balance ice flow velocity thickness variation and length fluctuation have been obtained from yearly measurements performed since 1975 this dataset provides an excellent opportunity to analyze the relationships between surface mass balance and dynamic response over time periods during which net mass balance changed from positive to negative following a positive specific net balance period between 1960 and 1981 the ablation zone experienced a large increase in thickness and ice flow velocities conversely the highly negative specific net balance period since 1982 has led to strong thinning deceleration and retreat of the tongue the response of these observed dynamics to surface mass balance is analyzed from ice flux calculations performed on three transverse cross sections our results reveal that the ice fluxes are largely accommodated by ice flow velocities velocity fluctuations are synchronous over the entire area studied in the largest part of the glacier no compressing extending flow change has been observed over the last 30 years and thickness changes are solely driven by surface mass balance changes however on the tongue of the glacier thickness changes do not depend on surface mass balance but are mainly driven by changes in the longitudinal strain rate

a new species of africanacetus odontoceti ziphiidae found on the deep ocean floor off the coast of brazil abstract a fossil skull of a beaked whale was newly collected by a manned submersible from the sao paulo ridge of the atlantic floor about 2900 m deep off the coast of brazil it was found in the middle of the manganese nodules on the seafloor the whale fossil can be dated sometime between the middle miocene and the early pliocene based on the timing of the onset of the tectonic movements of the sao paulo ridge whence the specimen came and the precipitation of the manganese layers which entirely encrusted the specimen this is the first instance of a fossil beaked whale skull retrieved from such great depths this skull belongs to a new species of africanacetus which may be a genus with a broad distribution in southern oceans in neogene times expands the geographic distribution of the genus as the northernmost record and adds the taxonomic and morphological diversity within the genus

a cretaceous and jurassic geochronology an integrated geomagnetic polarity and geologic time scale for the jurassic and cretaceous periods is presented based on various methods according to the availability of definitive isotopic ages an age calibrated sea floor spreading model is used to interpolate the ages of the kimmeridgian to barremian and the campanian to maestrichtian stages numerical age estimates for the aptian to santonian stage boundaries follow published isotopic age determinations the hypothesis of equal duration of ammonite zones is employed as a vernier to apportion time for the hettangian to oxfordian stages the new scale results in ages of 208 ma for the base of the jurassic 144 ma for the jurassic cretaceous boundary and 66 5 ma for the top of the cretaceous the integrated biostratigraphic magnetostratigraphic and geochronometric record serves as a working hypothesis for geologic correlation of jurassic and cretaceous strata

comparison of a three dimensional model for glacier flow with field data from haut glacier d arolla switzerland a three dimensional finite difference model based on a first order solution of the ice flow equations is applied to haut glacier d arolla switzerland the numerical model successfully converges at horizontal resolutions down to 70 m so a number of detailed comparisons with field data can be made modelled surface velocities with no basal sliding component are compared with surface velocities observed on the glacier over four different time periods the best fit is achieved with over winter surface velocities r 2 0 75 using a rate factor a in glen s flow law of 0 063 a 1 bar 3 surface zones of maximum computed effective stress display a high level of coincidence with observed crevassing the orientation of which is successfully predicted by the direction of the tensile component of the computed principal surface stress comparison of the relative magnitude and direction of computed principal stresses with principal strains measured at the ice surface also correspond closely in an attempt to simulate the observed annual velocity distribution within a cross section of the glacier tongue we incorporate two basal motion patterns into the model by treating net annual ice motion as a time weighted composite of three separate flow situations normal sliding enhanced sliding and no sliding we are able to reproduce the key features of the observed cross sectional ice and basal slip velocity distributions these experiments indicate there may be substantial decoupling taking place along an elongated narrow zone at the bed of haut glacier d arolla and that this decoupling interacts in a complex manner with the englacial stress and strain field

ice velocity changes on penny ice cap baffin island since the 1950s predicting the velocity response of glaciers to increased surface melt is a major topic of ongoing research with significant implications for accurate sea level rise forecasting in this study we u

distinguishing between sudden and gradual extinctions in the fossil record predicting the position of the cretaceous tertiary iridium anomaly using the ammonite fossil record on seymour island antarctica a simple method employing 50 confidence intervals may be used to distinguish sudden from gradual extinctions in cases where the fossil record is consistent with a sudden disappearance the expected position of the extinction horizon may als o be determined analysis of the fossil ammonites on seymour island shows that their pattern of disappearances is consistent with a sudden mass extinction at the cretaceous tertiary k t boundary even though a literal reading of the fossil record shows they disappeared gradually over a stratigraphic interval 10 50 m below the boundary it is striking that the iridium anomaly on seymour island falls within the stratigraphic interval determined by the 50 confidence intervals to be the most likely place for the k t boundary assuming there was a sudden disappearance of ammonites at the boundary however a computer simulation of the seymour island ammonite fossil record indicates a wide range of other extinction scenarios including gradual extinctions ranging over as much as 20 m 0 05 that are consistent with the ammonite fossil record without saturation collecting near the k t boundary it will be impossible to distinguish between gradual and sudden extinction scenarios for the seymour island ammonites based on the ammonite fossil record alone

sensitivity of rhonegletscher switzerland to climate change experiments with a one dimensional flowline model a one dimensional time dependent flowline model of rhonegletscher switzerland has been used to test the glacier s response to climatic warming mass balance variations over the last 100 years are obtained from observations of the equilibrium line altitude ela and a reconstruction of the ela based on a statistical correlation between temperature and ela for the period prior to ad 1882 for which no reliable climate data exist we chose equilibrium line altitudes that enabled us to simulate accurately the glacier length from ad 1602 the model simulates the historical glacier length almost perfectly and glacier geometry very well it underestimates glacier surface velocities by 1 18 following these reference experiments we investigated the response of rhonegletscher to a number of climate change scenarios for the period ad 1990 2100 for a constant climate equal to the 1961 90 mean the model predicts a 6 decrease in glacier volume by ad 2100 rhonegletscher will retreat by almost 1 km over the next 100 years at this scenario at a warming rate of 0 04 k a 1 only 4 of the glacier volume will be left by ad 2100

simulating annual glacier flow with a linear reservoir model 1 in this paper we present a numerical simulation of the observation that most alpine glaciers have reached peak velocities in the early 1980s followed by nearly exponential decay of velocity in the subsequent decade we propose that similarity exists between precipitation and associated runoff hydrograph in a river basin on one side and annual mean specific mass balance of the accumulation area of alpine glaciers and ensuing changes in ice flow on the other side the similarity is expressed in terms of a linear reservoir with fluctuating input where the year to year change of ice velocity is governed by two terms a fraction of the velocity of the previous year as a recession term and the mean specific balance of the accumulation area of the current year as a driving term the coefficients of these terms directly relate to the timescale the mass balance altitude profile and the geometric scale of the glacier the model is well supported by observations in the upper part of the glacier where surface elevation stays constant to within 5 m over a 30 year period there is no temporal trend in the agreement between observed and modeled horizontal velocities and no difference between phases of acceleration and phases of deceleration which means that the model is generally valid for a given altitude on a given glacier

disappearance of an alpine glacier over the 21st century simulated from modeling its future surface mass balance a spatially distributed snow ice model is used to simulate the surface mass balance of the saint sorlin glacier french alps over the 1981 2004 period the modeled mass balance globally reproduces field data except over places where because of the scarcity of measurements small scale features as proposed by the model are smoothed out by the data interpolation both measured and simulated mass balance fields are then used to force a 2 d ice flow model and comparison of respective results show similar large scale glacier flow dynamics on the other hand at a smaller scale the present day ice distribution computed from the modeled mass balance field sometimes deviates from that obtained with the interpolated field mass balance it particularly offers a better match to observations by succeeding in reproducing a specific deglaciation pattern in the upper part of the glacier these preliminary results led us to consider the possibility of substituting modeled mass balance series to measured ones especially when modeling the future of the glacier this latter approach is thus applied to simulate the glacier response under the ipcc sresb1 scenario results show a rapid decay leading to a total disappearance of the glacier by the year 2070

spatiotemporal variations in surface velocity of the gangotri glacier garhwal himalaya india study using synthetic aperture radar data the gangotri glacier is the largest in the garhwal himalaya india and its melt water forms the main source stream of the ganga river yet its dynamics are poorly understood its long record of terminus retreat measurements 1800 present shows multi decadal oscillations and more recently a slowing down of the retreat its complex dynamics are also indicated by studies of proglacial melt water at the terminus however there have been no systematic measurements of its surface velocity or how it changes seasonally or over longer term time scales here i have characterized the spatiotemporal variations of surface velocity of the gangotri glacier using synthetic aperture radar sar data spanning nearly two decades 1991 2011 the main findings are as follows 1 the glacier undergoes seasonal fluctuations in surface velocities there was a clear summer speedup of similar to 57 126 compared to winter velocities between 0 and 12 6 km from the terminus with peak summer speeds of 63 1 5 4 m yr in 1992 66 6 6 0 m yr in 1999 58 2 4 5 m yr in 2004 and 42 8 4 2 m yr in 2007 whereas winter speeds were relatively stable 25 30 m yr during the same period this summer speedup is indicative of increased basal sliding known to occur when melt waters penetrate to the glacier bed resulting in reduced friction 2 these summer velocities exhibited an inter annual reduction which was manifest as a reduction in summer speed up from 120 in 2004 to 60 in 2007 this pattern continued into 2011 despite the availability of abundant melt water during those years this inter annual reduction indicates the formation of increasingly efficient melt water channels year on year resulting in lesser lubrication at the glacier bed interface my results show that the gangotri glacier is dynamic throughout its length with systematic spatiotemporal variations in surface velocity that elucidate its subglacial processes based on my results and other evidence in the literature i propose that the subglacial drainage system of the gangotri glacier is subject to seasonal and inter annual hydrodynamic coupling between winters and melt seasons akin to other glaciers c 2016 elsevier inc all rights reserved

quantitative stratigraphy of the wufeng and lungmachi black shales and graptolite evolution during and after the late ordovician mass extinction article i nfo graptolite bearing black shales are widely distributed on the yangtze platform in south china based on 19 sec tions systematically studied recently we conducted a quantitative stratigraphic analysis of the graptolite biodi versity change during and after the late ordovician mass extinction the combination of graphic correlation and rarefaction methods make it possible to evaluate the effect of sampling intensity on biodiversity estimates graptolite diversity reached its peak in the dicellograptus complexus chron and then a gradual decline to the p pacificus chron it was followed by a two step mass extinction the first and major phase occurred in the metabolograptus extraordinarius chron and the second and minor phase in the latest m persculptus chron the second phase of the extinction was mostly represented by the elimination of the diplograptina survivors from the major extinction event but did not show significant decline in standardized diversity curve thereafter a moderate increase in richness appeared in the early and mid parakidograptus acuminatus chron which was followd by a considerable decrease of graptolite richness in the late p acuminatus chron and early c vesiculosus chron the present study also indicates slow and uneven sedimentation rates in the studied sections from mid katian to early rhuddanian including a relatively slower sedimentation rate during the hirnantian epoch the latter andthehiatusatthe honghuayuanandguanwusections probablyreflecttheeffectsofthe hirnantian glaciation and regional tectonic movements

the probable range concept applied to the biostratigraphy of marine microfossils the probable range of a taxon is its most frequently observed range defined for a set of geologic sections the probable range concept is defined and demonstrated using two applications both based on deep sea drilling project data the first uses a cenozoic and mesozoic north atlantic ocean data set calcareous nannoplankton 228 taxa 55 sections the major result is a standardized rangechart at a definable level of minimum confidence for the data set that shows excellent correlation when compared with published range data the second application uses a pacific ocean data set calcareous nannoplankton planktonic foraminifera radiolaria 330 taxa 32 sections the application results in an estimated maximum attainable resolution of 100 000 years for the tertiary the quantitative application of the probable range concept offers the improvement of resolution beyond the 100 000 year level equally reliable alternatives to standard biostratigraphic zonations and objective limits of confidence or risk o

relative contribution of surface mass balance and ice flux changes to the accelerated thinning of the mer de glace alps over 1979 2008 by subtracting surface topographies from 1979 1994 2000 and 2008 we measured ice thinning rates increasing from 1 m a 1 1979 1994 to more than 4 m a 1 2000 2008 on the tongue of the mer de glace the relative contributions of changes in surface mass balance and ice fluxes to this acceleration in the thinning are estimated using field and remote sensing measurements between 1979 1994 and 2000 2008 surface mass balance diminished by 1 2 m w e a 1 mainly because of atmospheric warming mass balance changes induced by the growing debris covered area and the evolving glacier hypsometry compensated each other meanwhile the mer de glace slowed down and the ice fluxes through two cross sections at 2200 m a s l and 2050 m a s l decreased by 60 between 1979 1994 and 2000 2008 two thirds of the increase in the thinning rates was caused by reduced ice fluxes and one third by rising surface ablation however those numbers need to be interpreted cautiously given our inability to respect mass conservation below our upper cross section an important implication is that large errors would occur if one term of the continuity equation e g surface mass balance was deduced from the two others e g elevation and ice flux changes

thinking outside the zone high resolution quantitative diatom biochronology for the antarctic neogene abstract developing a coherent neogene history of the antarctic ice sheet and southern ocean requires a high resolution biostratigraphic age model one that is applicable to the array of existing onshore and offshore paleoenvironmental records this study integrates comprehensive diatom biostratigraphy magnetostratigraphy and tephrostratigraphy from 32 neogene sections around the southern ocean and antarctic continental margin framing their correlation as a constrained optimization conop permits the use of computer implemented approaches that resemble multidimensional versions of graphic correlation the method establishes the most parsimonious sequence of events subject to an expert s selection of suitable input data determination of geological feasibility constraints and the most appropriate measure of fit to the data optimization quantitative output includes assessments of record quality and confidence intervals on all age assignments thorough review and testing of conop model settings and input datasets established the solution s sensitivity to these factors and guided the selective removal of unreliable data to produce a robust precise and reproducible biochronology two complementary models based on different assumptions about reworking yield independent estimates of average local ranges and total regional ranges of fossil taxa in the southern high latitudes the resulting composite sequences include range data of 116 diatom taxa as well as 52 paleomagnetic reversals and two radiometrically dated ashes which enable age calibration to within an average of 0 08 m y for first and last appearances as old as 18 ma deviations of new model ages from previously published estimates are generally small and reflect the different sample sizes available for traditional versus new quantitative biostratigraphic calibrations our results confirm the reliability and regional isochroneity of most commonly utilized diatom zonal marker events identify many new potentially useful events and provide up to an order of magnitude greater temporal resolution than traditional zonations the anticipated expansion of this new southern ocean chronostratigraphic framework to new localities and other microfossil groups will pave the way to further age refinement and broader application of this approach in the future

climatic reconstruction for the younger dryas early holocene transition and the little ice age based on paleo extents of argentiere glacier french alps abstract investigation of holocene extents of mountain glaciers along with the related naturally driven climate conditions helps improve our understanding of glacier sensitivity to ongoing climate change here we present the first holocene glacial chronology in the mont blanc massif argentiere glacier in the french alps based on 25 in situ produced cosmogenic 10be dates of moraines and glacial bedrocks the obtained ages from mapped sequences of moraines at three locations reveal that the glacier retreated from its lateglacial extent and oscillated several times between 11 7 ka and 10 4 ka i e during the younger dryas early holocene yd eh transition before substantially retreating at 10 4 ka climate conditions corresponding to the past extents of argentiere glacier during the yd eh transition 11 ka and the little ice age lia were modelled with two different approaches by determining summer temperature differences from reconstructed ela rises and by using a positive degree day pdd mass balance model the ela rise reconstructions yield a possible range of temperatures for the yd eh transition that were lower by between 3 0 and 4 8 c compared to the year 2008 depending on the choice of the ela sensitivity to temperature the results from the pdd model indicate temperatures lower by 3 6 5 5 c during the yd eh transition than during the 1979 2002 period for the lia our findings highlight the role of local precipitation changes superimposed on the dominant temperature signal in the detailed evolution of the glacier overall this study highlights the challenge that remains in accurately inferring paleoclimate conditions from past glacier extents

a 17 my old whale constrains onset of uplift and climate change in east africa timing and magnitude of surface uplift are key to understanding the impact of crustal deformation and topographic growth on atmospheric circulation environmental conditions and surface processes uplift of the east african plateau is linked to mantle processes but paleoaltimetry data are too scarce to constrain plateau evolution and subsequent vertical motions associated with rifting here we assess the paleotopographic implications of a beaked whale fossil ziphiidae from the turkana region of kenya found 740 km inland from the present day coastline of the indian ocean at an elevation of 620 m the specimen is 17 my old and represents the oldest derived beaked whale known consistent with molecular estimates of the emergence of modern strap toothed whales mesoplodon the whale traveled from the indian ocean inland along an eastward directed drainage system controlled by the cretaceous anza graben and was stranded slightly above sea level surface uplift from near sea level coincides with paleoclimatic change from a humid environment to highly variable and much drier conditions which altered biotic communities and drove evolution in east africa including that of primates