reservoir potential of late cretaceous terrestrial to shallow marine sandstones taranaki basin new zealand abstract late cretaceous coals and coaly source rocks are the main source of hydrocarbons in the taranaki basin yet to date there have not been any hydrocarbon discoveries within cretaceous strata and sandstone distribution and reservoir quality for this interval have been poorly understood the late cretaceous sediments were deposited in several sub basins across taranaki with their distribution largely determined by sediment supply subsidence and sea level change in this study we describe potential reservoir facies in well penetrations of cretaceous strata in taranaki as well as from outcrop in northwest nelson on the southern edge of the basin study of cretaceous outcrop has shown that facies distribution is a major control on reservoir quality shoreface intertidal and estuarine depositional facies contain both excellent well sorted sandstone reservoir facies as well as low net to gross reservoir poor facies these contrast with deposits from generally less well sorted and more heterolithic coastal plain environments much of the facies distribution is attributed to relative sea level fluctuations which occurred throughout deposition late cretaceous sandstones display a range of mean grain sizes and compositions with the latter related to geographic location and sediment source burial depths are highly variable across the basin ranging from 6 km and this has had a profound effect on reservoir quality the main petrographic controls on reservoir quality are sandstone composition volume of clay minerals degree of mechanical compaction related to maximum burial depth and proximity to a source of acidic pore fluids for the generation of secondary porosity results from this study suggest that cretaceous strata are a viable reservoir play over much of the western part of the taranaki basin and into parts of the south eastern basin palaeogeographic maps and textural compositional data can be used to high grade regions for further exploration

global trends of pco2 across the cretaceous paleogene boundary supported by the first southern hemisphere stomatal proxy based pco2 reconstruction reliable reconstructions of atmospheric carbon dioxide concentrations pco2 are required at higher resolution than currently available to help resolve the relationship between mass extinctions and changes in palaeo pco2 levels such reconstructions are needed 1 at a high temporal resolution for constraining the pre and post extinction atmospheres and 2 at a sufficient spatial resolution to constrain potential inter hemispheric differences here we estimate pco2 based on fossil lauraceae leaf cuticle specimens derived from three localities with strata spanning the latest cretaceous to the mid paleocene including a new cretaceous paleogene boundary k pg locality in new zealand we use two independent methods of stomatal density based pco2 reconstructions a transfer function calibrated using herbarium material and the stomatal ratio method producing three calibration sets our results based on the mean values of each of the three calibration methods indicate pco2 ranging between ca 460 and 650 ppm during the latest cretaceous falling precipitously to average values between ca 360 and 430 ppm across the k pg boundary and further to ca 305 320 ppm in the mid paleocene a spike of extremely high pco2 at the k pg could not be confirmed but our results are nonetheless consistent with previously published pco2 records from the northern hemisphere and show that stomatal density worldwide was responding to significant changes in pco2 across the k pg

latest cretaceous earliest paleogene vegetation and climate change at the high southern latitudes palynological evidence from seymour island antarctic peninsula abstract fluctuations in late cretaceous climate were already influencing biotic change prior to the environmental upheaval at the cretaceous paleogene k pg boundary but their general nature magnitude and timing remain controversial a high resolution dataset on terrestrially derived palynomorphs is presented from the high southern palaeolatitudes that unlocks details of small scale climate variability throughout this period of significant global change specifically this is a quantitative spore and pollen analysis of an expanded uppermost cretaceous to lowermost paleogene maastrichtian earliest danian shallow marine sedimentary succession from seymour island off the northeastern tip of the antarctic peninsula then as now located at 65 s using nearest living relatives the first detailed vegetation habitat and climate reconstruction is presented for the emergent volcanic arc at this time on the coastal lowlands a cool to warm temperate rainforest is envisaged growing in a riverine landscape with both wet river margin pond and relatively dry interfluve canopy gap habitats diverse podocarps and southern beech trees grew alongside angiosperm herbs and shrubs in mean annual temperatures of 10 15 c higher altitude araucarian forests gave way to open ericaceous heathland beyond the tree line in subalpine to alpine conditions with mean annual temperatures of a cold 5 8 c there is no exact modern botanical equivalent but the closest modern flora is that of the andes of southern chile and argentina maastrichtian climate is shown to have fluctuated from cool humid conditions through a rapid warming 2 million years prior to the k pg transition followed by cooling during the earliest danian a trend supported by previous work on this interval

latitudinal temperature gradient during the cretaceous upper campanian middle maastrichtian y18o record of continental vertebrates latitudinal variations in model biogenic apatite d18o values were calculated using fractionation equations of vertebrates and weighted rainfall y18o values along with mean annual air temperatures provided by iaea wmo meteorological stations the reference equation obtained was used to compute a continental temperature gradient for the late campanian middle maastrichtian interval by using published and new d18o values of phosphate from vertebrates samples are mainly tooth enamel from crocodilians and dinosaurs that lived at paleolatitudes ranging from 83 4 n alaska to 32 3 s madagascar the temperature gradient was less steep 0 4 0 1 c latitude than the present day one 0 6 c latitude with temperatures that decreased from about 30 c near the equator to about 5 c at the poles above 30 of paleolatitude air temperatures were higher than at present the validity of these results is discussed by comparison with climatic criteria inferred from paleontological paleobotanical and sedimentological data the latitudinal distribution of oxygen isotope compositions of continental vertebrates is potentially a powerful tool for quantifying mesozoic terrestrial climates

coniacian flora of the sudetes south western poland palaeoecological and palaeoclimatic interpretations abstract palaeoecology of the coniacian flora of the sudetes idzikow flora south western poland is reconstructed on the basis of fossil plant morphology palynology and taphonomy four plant communities are reconstructed salt marsh mangrove forest dominated by frenelopsis wetland coastal forest dominated by geinitzia pandanites monheimia riparian forest dominated by ettingshausenia debeya dryophyllum and mesophytic forest dominated by microphyllous angiosperms proxy palaeoclimatic data for the idzikow flora have been estimated using clamp technique the numerical variables are as follows mean annual temperature 17 2 c warm month mean temperature 25 2 c cold month mean temperature 8 7 c length of the growing season 9 4 months growing season precipitation 841 mm mean monthly growing season precipitation 135 mm precipitation during the three consecutive wettest months 484 mm precipitation during the three consecutive driest months 100 mm relative humidity 68 5 specific humidity 8 9 and enthalpy 32 57 the reconstructed vegetation was probably a warm temperate seasonal to tropical forest experiencing hot summers and a short relatively dry season

quantification of uncertainties in fossil leaf paleoaltimetry does leaf size matter 1 the utility of multivariate foliar physiognomy specifically the climate leaf analysis multivariate program clamp to yield reliable estimates of enthalpy and hence paleoelevation has been demonstrated by comparison with other proxies yet concerns have arisen regarding uncertainties arising from 1 apparent ambiguities in the scoring regime and 2 the way leaf size is scored regarding the first concern scoring ambiguities are examined by reporting on scoring tests with novice users and interlaboratory comparisons the uncertainties were found to be less than those arising from the statistical methodology underpinning clamp in respect to the second concern the effect of removing all size data both from modern test sites and fossil data was tested specifically the effect of removing leaf size data from the 15 ma namling data set from south central tibet was investigated removal of all size data from modern sites demonstrated that size data contributes little to estimates of mean annual temperature and enthalpy similarly the removal of leaf size information from the namling data set alone but with calibration unchanged and from both the namling site and calibration sites this time with recalibration still yield paleoelevation estimates that have been independently matched by oxygen isotope techniques moreover the removal of all leaf size information results in only small increases in uncertainty 52 m

foliar physiognomic record of climatic conditions during dormancy climate leaf analysis multivariate program clamp and the cold month mean temperature abstract the extent to which the leaves of woody dicots encode in their physiognomy the climatic conditions that exist during dormancy was tested by sampling 20 sites along an approximately west east transect across european russia the crimean peninsula western siberia and central eastern siberia this transect encompassed the most extreme mean annual temperature range recorded in the modern world where vegetation exists climate leaf analysis multivariate program clamp revealed little change in calibration of the warm month mean temperature compared with the physg3ar data set derived from less extreme sites primarily in north america and japan but significant change with respect to the cold month mean temperature cmmt calibration although clamp underestimated the cmmt by up to 9 c in the coldest sites the addition of the transect sites improved clamp s performance at low temperatures this suggests that winter cold is encoded in foliar physiognomy even though the leaves are functional only duri

migration velocity analysis from locally coherent events in 2 d laterally heterogeneous media part i theoretical aspects we present a new method based on migration velocity analysis mva to estimate 2 d velocity models from seismic reflection data with no assumption on reflector geometry or the background velocity field classical approaches using picking on common image gathers cigs must consider continuous events over the whole panel this interpretive step may be difficult particularly for applications on real data sets we propose to overcome the limiting factor by considering locally coherent events a locally coherent event can be defined whenever the imaged reflectivity locally shows lateral coherency at some location in the image cube in the prestack depth migrated volume obtained for an a priori velocity model locally coherent events are picked automatically without interpretation and are characterized by their positions and slopes tangent to the event even a single locally coherent event has information on the unknown velocity model carried by the value of the slope measured in the cig the velocity is e

climate model predictions for the latest cretaceous an evaluation using climatically sensitive sediments as proxy indicators to date many general circulation model gcm experiments have failed to reproduce the warm high latitude temperatures suggested for the cretaceous by geological proxy climate indicators especially for the northern hemisphere and within continental interiors the vast majority of these proxies are biologically based and it is important to determine whether alternative sedimentologically based proxies indicate similar cold biases in models therefore we have performed an evaluation of the very latest generation of climate model predictions for terrestrial sites using climatically sensitive sediments as palaeoclimate indicators evidence from the geological record comprising coal peat evaporites bauxite and laterite deposits are portrayed on a series of palaeoclimate data maps these are then compared with the global distributions of potential deposits generated from model simulations of the maastrichtian using versions of the hadley centre climate model the maastrichtian was chosen because of the greater range and sophistication of gcms adapted for its climate simulation and sediment prediction than for other cretaceous stages this thus represents the first attempt at comparing such state of the art models to lithological climate indicators and quantifying their relative performances for peat coal there is generally good correspondence between maastrichtian model predictions for predicted potential deposits and the observed record for evaporites there is also very close agreement between predictions by the models and the geological record minor differences between the individual model versions resulting from their differing levels of atmospheric co2 and the different palaeogeographical representations of intracontinental seaways in the northern hemisphere for bauxites and laterites the models predict less than half of the documented deposits successfully portraying equatorial accumulations but omitting the majority of mid to high latitude deposits the main discrepancy is therefore identified as the failure of all models to predict bauxite and laterite deposits corresponding with recorded accumulations within the mid to high latitudes of europe and asia in many cases the effects of co2 have minimal impact on the skill of model prediction however for evaporite distributions the low co2 model is appreciably worse in general the best match across the geological data and models is achieved by the simulation with open northern hemisphere seaways overall these results confirm those inferred from biological proxies showing that climate models have a serious cold bias in high latitudes and continental interiors during the cretaceous and that the latest generation of climate models still produces results which are incompatible with the geological data levels of atmospheric co2 and uncertainties in palaeogeography cannot explain the discrepancy the cold bias is common to many climate models and suggests that a process or mechanism is poorly represented or omitted in the current generation of climate models or that we are failing to recognise a major boundary condition change in the cretaceous if the former this implies that we may be underestimating the extent of extreme future climate change at high latitudes and in continental interiors

the use of a resemblance function in the measurement of climatic parameters from the physiognomy of woody dicotyledons abstract wolfe compiled a data set clamp of the physiognomy of woody dicotyledon leaves with a view to using it to extract climatic information from fossil floras attempts made using these data to identify and describe the relationship between plant physiognomy and climate have all searched for a global relationship applicable throughout data space we investigate the possibility that the relation between climate and physiognomy is so non linear that only local relationships should be sought we use a resemblance function to select sites that are physiognomically similar to each unknown site these similar sites alone yield a climatic estimate for the unknown site data collected from new zealand and australia are then added to wolfe s data set in order to test this new method we show that the use of a resemblance function enables us to produce mean annual temperature estimates for all modern sites that lie within 2 6 c of meteorological data for 90 of the sites this method also allows the objective identification of outliers based on their distance in physiognomic space from their nearest neighbours when a method is used that searches for a global relationship between physiognomy and climate the misfit of estimated mean annual temperature for the combined southern hemisphere and clamp sites is almost twice as great 5 c as that to the clamp sites alone in contrast when the resemblance function is used the rms misfit of estimated mean annual temperature increases by only 0 2 c this result demonstrates the robustness of the new method

seismic wave equation demigration migration reverse time migration is a well known method based on a single scattering approximation it is designed to obtain seismic images in the case of a complex subsurface it can however be a very time consuming task because the number of computations is directly proportional to the number of processed sources in the context of velocity model building iterative approaches require that one derives a series of migrated sections for different velocity models we propose to replace the summation over sources by a summation over depth offsets or time delays defined in the subsurface for that we have developed a new relationship between two migrated sections obtained for two different velocity models starting from one of the two images we obtain a second section correctly and efficiently for each time delay we compute a generalized source term by extending the concept of exploding reflector to nonzero offset we obtain the final migrated section by solving the same wave equation in the perturbed model with the modified source term our work included testing the methodology on 2d synthetic data sets particularly when the initial and perturbed velocity models differ greatly

an early middle eocene antarctic summer monsoon evidence of fossil climates abstract a warmer and mostly ice free south polar region prevailed during the early middle eocene indicative of a low latitudinal temperature gradient climatic models mostly fail to reconstruct such a low gradient demonstrating our poor understanding of the mechanisms involved in heat transfer here we describe a new phenomenon that shaped the southern high latitude climate during the early middle eocene the antarctic summer monsoon our palaeoclimatic reconstruction is based on 25 morphotypes of fossil dicotyledonous leaves from the early middle eocene fossil leaf assemblage of fossil hill from king george island the antarctic peninsula we use a novel clamp climate leaf analysis multivariate program calibration which includes new climatic parameters that allow us to characterise better the seasonality in precipitation our reconstruction indicates a warm humid temperate climate with strong seasonality in temperature and precipitation seasonality in precipitation indicates a rainfall rate of 6 4 1 30 mm day during summer summer daily rate of precipitation sdr and a summer precipitation representing more than 60 3 8 28 of annual rainfall ratio of summer precipitation rsp which fulfils the definition of a summer monsoon in the modern world this implies a seasonal alternation of high and low pressure systems over antarctica during the early middle eocene such a climate regime would have impacted upon global atmospheric circulation and heat transfer this climatic regime presents a challenge for climatic models and their ability to reconstruct accurately palaeoclimates at high southern latitudes and thereby understand latitudinal heat transfer in a greenhouse earth regime

the distinct foliar physiognomy of the late cretaceous forests of new zealand probably deciduous abstract three features of leaf physiognomy craspedodromous venation compound teeth and a lobed leaf outline figure prominently in the late cretaceous vegetation of southern new zealand these make it distinctly different from typical extant predominantly evergreen forests and some deciduous vegetation the physiognomy of the late cretaceous vegetation at the assemblage level shows more similarity with predominantly deciduous forests of the northern hemisphere in terms of the proportions of these characters in the flora at the taxon level combinations of characters found in fossils are very similar to and in some cases restricted to widespread extant northern hemisphere deciduous taxa but also to rarer components of evergreen forests it may not be possible to categorically determine whether any one fossil was deciduous the distinctly different assemblage level foliar physiognomy implies a distinctly different lifestyle for the new zealand forests that bordered gondwana in the late cretaceous it is highly likely that this physiognomy reflects an important deciduous component this is unexpected as for at least part of this time new zealand was apparently below north of the polar circle with a temperate and everwet climate

north american nonmarine climates and vegetation during the late cretaceous abstract analyses of physiognomy of late cretaceous leaf assemblages and of structural adaptations of late cretaceous dicotyledonous woods indicate that megathermal vegetation was an open canopy broad leaved evergreen woodland that existed under low to moderate amounts of rainfall evenly distributed through the year with a moderate increase at about 40 45 n many dicotyledons were probably large massive trees but the tallest trees were evergreen conifers megathermal climate extended up to paleolatitude 45 50 n mesothermal vegetation was at least partially an open broad leaved evergreen woodland perhaps a mosaic of woodland and forest but the evapotranspirational stress was less than in megathermal climate some dicotyledons were large trees but most were shrubs or small trees evergreen conifers were the major tree element some mild seasonality is evidenced in mesothermal woods precipitational levels probably varied markedly from year to year northward of approximately paleolatitude 65 n evergreen vegetation was replaced by predominantly deciduous vegetation this replacement is presumably related primarily to seasonality of light the southern part of the deciduous vegetation probably existed under mesothermal climate comparisons to leaf and wood assemblages from other continents are generally consistent with the vegetational climatic patterns suggested from north american data limited data from equatorial regions suggest low rainfall late cretaceous climates except probably those of the cenomanian had only moderate change through time temperatures generally appear to have warmed into the santonian cooled slightly into the campanian and more markedly into the maastrichtian and then returned to santonian values by the late maastrichtian the early eocene was probably warmer than any period of the late cretaceous latitudinal temperature gradients were lower than at present for the campanian and maastrichtian a gradient of about 0 3 c 1 latitude is inferred equability was high a mean annual range of temperature of about 8 c is inferred for paleolatitude 51 56 n during the campanian most late cretaceous plants evolved in a climate characterized by absence of freezing and low to moderate amounts of precipitation a brief low temperature excursion and a major long lasting increase in precipitation occurred at the cretaceous tertiary boundary in megathermal climates these events selected for plants that could exist in rainforest environments in mesothermal climates deciduousness and contamitant structural adaptations were selected the events at the cretaceous tertiary boundary had a major and long lasting impact on the evolution of land plants and their ecosystems low precipitation at low to middle late cretaceous latitudes is suggested to be the result of high levels of atmospheric co2 which in turn are probably related to inability of warm saline oceans to store large amounts of carbon conditions appear to have rapidly changed at the cretaceous tertiary boundary when oceanic circulation and stratification may have been fundamentally altered after the boundary the oceans were apparently able to store much greater amounts of carbon and the oceans withdrew large amounts of co2 from the atmosphere in turn more precipitation fell at low to middle latitudes the resulting high biomass vegetation formed a second major carbon reservoir to keep atmospheric co2 low relative to the late cretaceous changes in oceanic and atmospheric circulation probably resulted from some factor external to the ocean atmosphere system

artificial neural networks reveal a high resolution climatic signal in leaf physiognomy the relationship linking leaf physiognomy and climate has long been used in paleoclimatic reconstructions but current models lose precision when worldwide data sets are considered because of the broader range of physiognomies that occur under the wider range of climate types represented our aim is to improve the predictive power of leaf physiognomy to yield climate signals and here we explore the use of an algorithm based on the general regression neural network grnn which we refer to as climate leaf analysis with neural networks clann we then test our algorithm on climate leaf analysis multivariate program clamp data sets and digital leaf physiognomy dlp data sets and compare our results with those obtained from other computation methods we explore the contribution of different physiognomic characters and test fossil sites from north america the clann algorithm introduced here gives high predictive precision for all tested climatic parameters in both data sets for the clamp data set neural network analysis improves the predictive capability as measured by r 2 to 0 86 for mat on a worldwide basis compared to 0 71 using the vector based approach used in the standard analysis such a high resolution is attained due to the nonlinearity of the method but at the cost of being susceptible to 39 noise 39 in the calibration data tests show that the predictions are repeatable and robust to information loss and applicable to fossil leaf data the clann neural network algorithm used here confirms and better resolves the global leaf form climate relationship opening new approaches to paleoclimatic reconstruction and understanding the evolution of complex leaf function

quantitative palaeoclimate estimates from late cretaceous and paleocene leaf floras in the northwest of the south island new zealand three new plant macrofossil assemblages were collected from late cretaceous and paleocene fluvio lacustrine sediments of the pakawau and kapuni groups in the northwest of the south island new zealand palaeoenvironmental interpretations were made from each locality and palaeoclimate was deduced from the dicotyledonous angiosperm leaf component of each flora a latest cretaceous pakawau bush road locality flora yielded 58 different dicotyledonous leaf forms the two paleocene collections ian s tip and pillar point track included 23 and 28 dicotyledonous leaf forms respectively quantitative palaeoclimate estimates were obtained using both leaf margin analysis lma and the climate leaf analysis multivariate program clamp temperature estimates suggest that there was a slight cooling from the latest cretaceous into the early paleocene in the northwest nelson region of new zealand supporting similar southern hemisphere palaeoclimate findings from antarctic data consistency in temperature estimates using different methods including lma multivariate leaf morphological analysis clamp oxygen isotope data regional versus local studies and global palaeoclimate models suggests that the mean annual temperature for the pakawau region in the latest cretaceous was between 12 and 15 c lma produced temperature estimates between 6 5 and 8 c for the two paleocene assemblages whereas clamp produced estimates were slightly higher between 9 and 12 5 c 2002 elsevier science b v all rights reserved

new quantitative palaeocolimate data for the late cretaceous arctic evidence for a warm polar ocean abstract physiognomic analysis of four taphofloras one from the coniacian of n alaska one from the coniacian of kamchatka one from the turonian of kamchatka and one from the turonian of novaya sibir island using the clamp technique of wolfe 1993 yielded quantitative data on the mean annual warm month mean and cold month mean temperatures the length of the growing season mean annual precipitation mean growing season precipitation mean monthly growing season precipitation and the precipitation during the three consecutive driest months these new results represent the first application of multivariate statistical analysis of foliar physiognomy to determine palaeoclimatic parameters clamp to arctic cretaceous floras and demonstrate its robustness even in the context of vegetation which has no living analogues these new estimates were comparable to those from previous quantitative or qualitative sedimentological or palaeobotanical data where they were available but offer greater measurable precision the results also suggest that an arctic ocean with a winter surface temperature of approximately 6 c maintained n alaska coastal temperatures above freezing locally reversing the equator to pole temperature gradient a phenomenon not seen in the northern proto pacific this anomalously warm arctic ocean could have been produced by marine poleward heat transport precipitation in alaska kamchatka and novaya sibir island was predicted to have been high e g 1760 mm yr in the coniacian of n alaska reflecting a very weak polar high pressure cell and substantially different precipitation patterns to present

oxygen isotope and paleobotanical estimates of temperature and δ18o latitude gradients over north america during the early eocene empirical estimates of climate parameters such as mean annual temperature mat are essential to describe both ancient climate and to ground truth climate model simulations of past climates in terrestrial settings no single proxy record is able to provide detailed temporal yet geographically widespread information and it thus becomes essential that paleoclimatic information obtained from different proxies be comparable as an example of how to compare estimates and to illustrate what can be learned by doing so we measured oxygen isotope ratios of phosphate in the tooth enamel of fossil mammals and the body scales of freshwater fish in order to estimate the mean annual temperature mat in which they lived the samples were collected from paleogene rocks of the bighorn green river and powder river basins of wyoming earliest eocene samples provide mat estimates that are similar to mat estimates for the same times and areas obtained from leaf margin analysis furthermore isotopic data from the paleocene eocene thermal maximum petm which has not yet yielded fossil floras indicate a significantly higher mat of 26 c we also used temperature estimates obtained by both methods to investigate paleoelevation and to reconstruct geographic patterns of mat over north america for the early eocene larger laramide basins have higher temperatures and lower inferred elevations compared to associated volcanic highlands where cooler temperatures are consistent with substantial elevations in turn latitudinal gradients in temperature indicate that warming centered on polar regions played an important role during the eocene hothouse lastly we show that the reconstructed eocene relation between oxygen isotope ratios of precipitation and mat is significantly different from the modern relation between these two variables because the relation has changed over time the modern correlation should not be used to estimate paleo mat from measurements of oxygen isotope ratios in fossil material

comparison of kirchhoff and reverse time migration methods with applications to prestack depth imaging of complex structures the performance of two popular migration methods the kirchhoff integral and reverse time migrations is evaluated through applications to imaging complex structures using prestack shot records the migration results from the marmousi model data demonstrate that reverse time migration is more accurate than kirchhoff migration in imaging the steeply dipping faults however the improved accuracy of reverse time migration requires higher computational costs in the application to the alberta foothills data where a good estimate of the velocity model is available however both the kirchhoff and the reverse time migration methods produce almost identical results this implies that in the real world of exploration seismology it will be relatively difficult to identify which method performs better because we never know the exact answer of the subsurface

quantitative reconstruction of the late miocene monsoon climates of southwest china a case study of the lincang flora from yunnan province the miocene lincang leaf assemblage is used in this paper as proxy data to reconstruct the palaeoclimate of southwestern yunnan sw china and the evolution of monsoon intensity three quantitative methods were chosen for this reconstruction i e leaf margin analysis lma climate leaf analysis multivariate program clamp and the coexistence approach ca these methods however yield inconsistent results particularly for the precipitation as also shown in european and other east asian cenozoic floras the wide range of the reconstructed climatic parameters includes the mean annual temperature mat of 18 5 24 7 degrees c and the mean annual precipitation map of 1213 3711 mm compared with the modem lincang climate mat 17 3 degrees c map 1178 7 mm the miocene climate is slightly warmer wetter and has a higher temperature seasonality a detailed comparison on the palaeoclimatic variables with the coeval late miocene xiaolongtan flora from the eastern part of yunnan allows us to investigate the development and interactions of both south asian and east asian monsoons during the late miocene in southwest china now under strong influence of these monsoon systems our results suggest that the monsoon climate has already been established in southwest yunnan during the late miocene furthermore our results support that both southeast asian and east asian monsoons co occurred in yunnan during the late miocene c 2010 elsevier b v all rights reserved

the relationship between leaf physiognomy and climate based on a large modern dataset implications for palaeoclimate reconstructions in china abstract in this paper correlation between modern leaf physiognomy and climate in china are examined to optimize the use of leaf characters as a palaeoclimate proxy a large dataset was compiled recording the distribution of leaf physiognomic characters among 3166 native dicot trees species across 732 calibration grids on a county level grids span a range of ecological environments tropical rainforests to alpine shrubs across humid areas thirteen climatic parameters were included for each grid and 22 leaf physiognomic characters were scored for each tree species the correlation between leaf physiognomic characters and climatic parameters were calculated based on single linear regressions slr and multiple linear regressions mlr results indicate clear spatial distribution patterns linked to latitude exist for all leaf characters with temperature coldest month mean temperature cmmt and precipitation growing season precipitation gsp being the main climate controls moreover because leaf characters are more closely correlated with precipitation during the three wettest consecutive months p3wet rather than with precipitation during the three driest consecutive months p3dry seasonal variations in rainfall associated with the asian monsoon might especially influence leaf physiognomic characters closer correlations between leaf physiognomy and climate are seen using mlr compared with slr therefore mean annual temperature mat and mean annual precipitation map based on mlr equations provide the most promising basis for palaeoclimate reconstructions in china

refining clamp investigations towards improving the climate leaf analysis multivariate program clamp climate leaf analysis multivariate program has been used for the past 17 years to estimate palaeoclimatic conditions the reliability and applicability of this method based on leaf physiognomic characters of fossil woody dicots has been widely discussed over the same period the present study focuses on some technical aspects of clamp mainly on its robustness in the context of the theoretical unimodal requirements of canonical correspondence analysis and introduces correction coefficients for these aspects of the statistical approach as a new way of interpreting and improving on clamp estimates this tool was tested on datasets derived from 17 european fossil floras ranging in age from the late oligocene to the pliocene additionally an objective statistical method for the selection of the best suited modern vegetation dataset from 144 site physg3br or 173 physg3ar extant biotopes is proposed

deriving temperature estimates from southern hemisphere leaves abstract the percentage of woody dicots with entire margined leaves in a flora is known to be positively correlated with mean annual temperature leaf margin analysis lma but this relationship is not globally uniform in particular the floras of australia and new zealand have been regarded as displaying a different physiognomic relationship to climate than floras seen in the northern hemisphere this difference is more marked in new zealand where the lma relationship appears entirely absent here we amass data for both northern and southern hemispheres using standard protocols and show that regional variations in the leaf margin mean annual temperature relationship are real but become less significant when other characters are included even new zealand falls into line and most of the mean annual temperature signal in new zealand floras is encoded in non margin features we introduce a new clamp climate leaf analysis multivariate program calibration dataset for the southern hemisphere comprising leaf physiognomic data from argentina bolivia south africa australia new zealand and other pacific islands that offers comparable precision for climate prediction to similar datasets derived from the northern hemisphere

incorporating sinuous connectivity into stochastic models of crustal heterogeneity examples from the lewisian gneiss complex scotland the franciscan formation california and the hafafit gneiss complex egypt stochastic models are valuable and sometimes essential tools for investigating the behavior of complex phenomena in seismology stochastic models can be used to describe velocity heterogeneities that are too small or too numerous to be described deterministically where analytic approaches are often infeasible synthetic realizations of such models can be used in conjunction with finite difference algorithms to systematically investigate the response of the seismic wave field to complex heterogeneity this paper represents a continuing effort at formulating a complete and robust stochastic model of lithologic heterogeneity within the crust and the means of generating synthetic realizations complete implies that the model is flexible enough to describe all types of random heterogeneity within the crust while robust implies sufficiently constrained parameterization that an inversion problem may be well posed as a basis for investigation we use geologic maps of crustal exposures and petrophysically inferred velocities earlier efforts at stochastic modeling have focused on characterization of the univariate probability density function which is typically modal i e binary ternary etc and the covariance function which is typically fit with a von karman function here we provide a means of characterizing the property of sinuous connectivity and for generating realizations that possess this property sinuous connectivity is the tendency for individual lithologic units to be continuous over long and highly contorted paths there is no means in the earlier modeling of either characterizing or synthesizing this property we generate sinuously connective realizations by mapping regions encompassed by two contours in a gaussian distributed surface into the two values of the binary field this operation is nonunique as one can choose in many ways the values for the contours

quantification of large uncertainties in fossil leaf paleoaltimetry 1 estimates of paleoelevation potentially constrain geodynamic models of continental deformation and inform interpretations of landscape and climate evolution one widely used paleobotanical approach reconstructs paleoelevation from the difference in estimated atmospheric enthalpy between a known sea level and a targeted coeval elevated fossil floral site enthalpy is estimated using climate leaf analysis multivariate program clamp on 31 leaf size and shape variables that have been calibrated in living forests errors related to clamp are significantly greater than often reported and there are many sources of large potential error related to this method that are either difficult to quantify or unquantifiable and are thus not documented here we quantify one significant bias toward underestimation of leaf area in the clamp data set 50 that affects all clamp climate estimates including enthalpy crucially errors in paleoelevation when the leaf size bias is included are in the range of 2 km or more at least 2 times the previous estimates and exceeding the plausible paleoelevations of many fossil sites previously published paleoelevations derived from this technique are unlikely to be accurate either in magnitude or in estimated error

prestack migration velocity estimation using nonlinear methods we describe here methods of estimating interval velocities based on two nonlinear optimization methods very fast simulated annealing vfsa and a genetic algorithm ga the objective function is defined using prestack seismic data after depth migration this inverse problem involves optimizing the lateral consistency of reflectors between adjacent migrated shot records in effect the normal moveout correction in velocity analysis is replaced by prestack depth migration when the least squared difference between each pair of migrated shots is at a minimum the true velocity model has been found our model is parameterized using cubic b splines distributed on a rectangular grid the main advantages of using migrated data are that they do not require traveltime picking knowledge of the source wavelet and expensive computation of synthetic waveform data to assess the degree of data model fit nonlinear methods allow automated determination of the global minimum without relying on estimates of the gradien

palaeoclimate analysis of late cretaceous angiosperm leaf floras james ross island antarctica the fossilized remains of cretaceous angiosperm leaves are preserved within sandstones and siltstones of the coniacian hidden lake formation gustav group and the santonian early campanian santa marta formation marambio group in the james ross basin antarctic peninsula region the leaves represent the remains of vegetation that grew at approximately 65 s on an emergent volcanic arc now represented by the antarctic peninsula and were subsequently transported and buried in marine sediments in the adjacent back arc basin some of the angiosperm leaf morphotypes show similarities to leaves of living families such as sterculiaceae lauraceae winteraceae cunoniaceae and myrtaceae palaeoclimate analysis based on physiognomic aspects of the leaves such as leaf margin analysis indicates that the mean annual temperatures for the hidden lake and santa marta formations were 13 21 c mean 17 c and 15 23 c mean 19 c respectively the fossil plants are indicative of warm climates without extended periods of winter temperatures below freezing and with adequate moisture for growth this period of cretaceous warmth in antarctica corresponds with the cretaceous thermal maximum an interval of peak global warmth from the turonian to the early campanian

vibracoring a new method for coring deep lakes abstract a major limitation facing lacustrine researchers is an inability to take long 6 to 18 m continuous sediment cores in water depths greater than several metres at a low cost these problems have limited the advancement of palaeolimnology and quaternary stratigraphy working from a frozen lake surface new developments make it possible to take 18 m long vibracores in water depths of at least 55 m high frequency low amplitude vibrations are transferred down a series of 6 m long 7 6 cm diameter core tubes 3 inch aluminum irrigation pipe rigidly coupled end to end vibrations liquify sediment adjacent to the core tube walls thus allowing penetration of the sediment a core catcher prevents sediment from extruding out of the tube end during extraction this cost effective and labour efficient two persons coring system has been achieved by developing rigid core tube couplers a hand powered drum cable hoist and a set of operation procedures the hoist cable end is attached to a clamp 1 m above the core catcher and at each coupler along the pipe string at 6 m intervals lifting or lowering using a drum cable hoist allows for quick coupling and decoupling of core tubes although vibracoring is an improvement over other systems it still has portability limitations because of the bulk and weight of the equipment and large amount of pipe required for deep coring three sleds are required to transport equipment from the nearest vehicle access to the coring sites

modelling equable climates of the late cretaceous can new boundary conditions resolve data model discrepancies late cretaceous maastrichtian climate and vegetation is modelled using the hadcm3l fully coupled atmosphere ocean model and the triffid dynamic vegetation model we investigate data model inconsistencies in the high latitudes and continental interiors by exploring the sensitivity of modelled terrestrial climate to vegetation treatment changing atmospheric pco2 levels and the representation of arctic seaway connections we expand on previous work by using millennial scale gcm runs with dynamic vegetation to allow for improved representations of ocean heat transport and terrestrial boundary conditions incorporating realistic vegetation drives high latitude warming particularly during summer through reductions in surface albedo and induced atmosphere ocean feedbacks resulting regional warming can exceed 10 c as pco2 rises some regions cool as deciduous to evergreen change increases albedo incorporating enhanced arctic connectivity reconfigured ocean heat transport drives widespread terrestrial warming of 3 c and 5 c regionally applying sensitivities in combination significant palaeobotanical data model inconsistencies in the northern high latitudes and continental interiors remain further work is required to resolve climate and vegetation model deficiencies and improve the interpretation and geographic distribution of quantitative climate sensitive geological proxies

migration velocity analysis from locally coherent events in 2 d laterally heterogeneous media part ii applications on synthetic and real data we demonstrate a method for estimating 2 d velocity models from synthetic and real seismic reflection data in the framework of migration velocity analysis mva no assumption is required on the reflector geometry or on the unknown background velocity field provided that the data only contain primary reflections diffractions in the prestack depth migrated volume locations where the reflectivity exhibits local coherency are automatically picked without interpretation in two panels common image gathers cigs and common offset gathers cogs they are characterized by both their positions and two slopes the velocity is estimated by minimizing all slopes picked in the cigs we test the applicability of the method on a real data set showing the possibility of an efficient inversion using 1 the migration of selected cigs and cogs 2 automatic picking on prior uncorrelated locally coherent events 3 efficient computation of the gradient of the cost function via paraxial ray tracing from the picked events to the surface and 4 a gradient type optimization algorithm for convergence