the rise and demise of podozamites in east asia an extinct conifer life style abstract in the late triassic early jurassic forests dominated by podozamites an apparently deciduous shoot dropping conifer with broad multi veined leaves were extensive in what were the mid latitudes of eastern asia podozamites was the only conifer in many forests of this region and at times appeared to have formed an almost mono specific vegetation podozamites appears to have been little effected through the triassic jurassic transition but responded to climate changes later in the jurassic the chinese region progressively dried through the middle jurassic and aridity had developed in some areas by the late jurassic early cretaceous the centre of distribution of podozamites shifted north to the siberian region where conditions remained wet there it typically coexisted with conifers having a diverse range of smaller leaf morphologies by the late albian angiosperms had arrived in the siberian area and risen to dominance some time after this event podozamites became extinct this is significant as it represents the permanent extinction of a unique lifestyle a deciduous broad leaved and multi veined conifer the broad history of podozamites raises some interesting issues 1 the existence of a large dominantly deciduous vegetation at mid latitudes in the late triassic early jurassic is little discussed 2 it is unexpected that as broad leaved angiosperms took over amongst the conifers it was the broad leaved multi veined podozamites that became extinct this is the morphology that might have been expected to compete with the apparently more shade forming angiosperms instead it was the smaller leaved and single veined conifers that remained to coexist with the angiosperms

preservation of primary stable isotope signals in dinosaur remains and environmental gradients of the late cretaceous of montana and alberta abstract although the use of stable isotope data from vertebrate remains is becoming common for the cenozoic their application to mesozoic environments has been rare in part due to the perception that diagenesis has obfuscated all potential primary signal in this paper we illustrate how stable isotope data collected from dinosaur and other vertebrate remains can in fact be used to reconstruct paleoenvironmental conditions during the mesozoic carbon and oxygen isotope ratios were measured from tooth enamel of hadrosaur dinosaurs and from scales of freshwater fish that were collected from sites in the two medicine judith river and dinosaur park formations of montana and alberta these formations represent a coastal to upland gradient along the western margin of the late cretaceous inland seaway isotopic comparisons among skeletal components and among taxa are used as evidence that primary paleoenvironmental information as recorded by isotope data is preserved in tooth enamel and freshwater fish scales a comparison of carbon isotope ratios between hadrosaur tooth enamel and sedimentary organic matter indicates that these animals had a larger isotopic offset compared to bulk diet than modern mammals and that all hadrosaurian isotope data are consistent with the existence of c3 only ecosystems higher and more variable carbon and oxygen isotope ratios from animals occupying the coastal judith river region are interpreted to reflect a range of freshwater to brackish water conditions and plants that were undergoing water stress lower and less variable carbon and oxygen isotope ratios from the upland two medicine and intermediate dinosaur park areas are interpreted to reflect a gradual rainout of moisture from air masses moving inland and more uniform environmental conditions overall these results indicate that stable isotopes from dinosaur and other vertebrate remains have the potential to expand our understanding of terrestrial environments and ecosystems during the mesozoic

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

high precision 40ar 39ar age for the jehol biota abstract abundant fossils of the terrestrial jehol biota including plants insects dinosaurs birds mammals and freshwater invertebrates were discovered from the yixian formation and the overlying jiufotang formation in inner mongolia hebei province and liaoning province northeastern china because of the exceptional preservation of fossils the jehol biota is one of the most important mesozoic lagerstatten and is referred to as a mesozoic pompeii the jehol biota has provided a rare opportunity to address questions about the origin of birds the evolution of feathers and flight the early diversification of angiosperms and the timing of placental mammal radiation six tuff samples and two basalt samples collected from the tuchengzi the yixian and the jiufotang formations near the classic outcrops in western liaoning ne china yielded high precision 40 ar 39 ar ages we obtain an age of 129 7 0 5 ma for a basaltic lava from the bottom of the yixian formation and an age of 122 1 0 3 ma for a tuff from the lowermost part of the overlying jiufotang formation our age results provide an age calibration of the whole yixian formation and show that the whole formation was deposited entirely within early cretaceous time over an interval of 7 ma

oxygen isotope variations in phosphate of biogenic apatites ii phosphorite rocks abstract phosphorites from sedimentary sequences ranging in age from archaean to recent were analysed for 18 o in both the po 4 18 o p and co 3 18 o c in the apatite lattice the oxygen isotope record is considerably better preserved in phosphates than in either carbonates or cherts the use of the longinelli and nuti 8 temperature equation yields temperatures for recent phosphorites that are in good agreement with those measured in the field the 18 o p values of ancient phosphorites decrease with increasing age these changes with time are not likely to be due to post depositional exchange changes in 18 o values of seawater and variations of temperature with time can account for the 18 o p time trend but the latter explanation is preferred in ancient phosphorites 18 o c in structurally bound carbonate in apatite is not a reliable geochemical indicator

evidence for rapid climate change in north america during the latest paleocene thermal maximum oxygen isotope compositions of biogenic phosphate from the bighorn basin wyoming oxygen isotope records of cenozoic sea water temperatures indicate that a rapid warming event known as the latest paleocene thermal maximum lptm occurred during the otherwise gradual increase in world temperatures during the late paleocene and early eocene oxygen isotope analysis of the carbonate and phosphate components of hydroxyapatite found in mammalian tooth enamel and body scales of river dwelling fish from the bighorn basin in wyoming were made to investigate corresponding changes in the terrestrial climate a comparison of carbonate and phosphate isotope data from modern and fossil material indicates that some diagenetic alteration of the fossil material has occurred although systematically larger intra tooth ranges in the oxygen isotope composition of carbonate indicate that it is more likely to have been affected than phosphate carbonate and phosphate from the ecologically diverse mammals and fishes both record a shift to higher oxygen isotope ratios at the same time and of the same duration as the lptm these shifts reflect a change in the isotopic composition of regional precipitation which in turn provides the first evidence for continental climate change during the lptm assuming the present day relation between the oxygen isotope composition of precipitation and temperature applies to conditions in the past and that animal physiology and behavior is relatively invariant over time the isotopic shift is equivalent to an increase of surface temperature in western north america of several degrees this result is consistent with the magnitude of high latitude ocean warming and provides a basis for relating marine and terrestrial oxygen isotope records to records of terrestrial biotic change 1998 elsevier science b v all rights reserved

continental paleotemperatures from an early cretaceous dolomitic lake gansu province china abstract the lower cretaceous strata of asia are renowned for abundant fossil resources these strata can also offer a wealth of quantitative data regarding the paleoclimate and paleoenvironment of the terrestrial cretaceous an important transition in earth history many modern groups of organisms that dominate terrestrial ecosystems today originated or expanded in the early cretaceous in addition the cretaceous period known to have been characterized by a greenhouse climate provides opportunities to understand how the climate system functioned during greenhouse climate states here we utilize the clumped isotope paleothermometer to provide paleotemperature records from a lacustrine sequence in northwestern china previously constrained to the early aptian petrographic and x ray diffraction analyses indicate that the lake sediments produced primary to early diagenetic dolomites likely microbially mediated due to high organic matter input and seasonally warm arid conditions the majority of the dolomitic carbonates formed in pore waters just below the sediment water interface or as primary shallow water precipitates clumped isotope derived temperatures from all carbonates range from 20 6 c for early diagenetic dolomites to 47 2 c for late burial calcite cements accounting for seasonal biases mean annual air temperatures are calculated to have averaged 20 2 c this is broadly consistent with local paleotemperature proxy evidence and climate model paleotemperature estimates the data presented provides further quantitative constraints on the cretaceous greenhouse world as well as insights into depositional settings that produce low temperature dolomites

paleomagnetic constraints on the geodynamic history of the major blocks of china from the permian to the present paleomagnetic study of china and its environs has been the center of a major international effort for the last 10 years in this paper we critically review all available paleomagnetic poles of upper permian to tertiary age from the main blocks of china with the goal of placing constraints on models of the formation and the subsequent deformation of the region after selecting reliable poles by applying objective criteria we divide our analysis into first order motions of blocks and second order deformation within blocks for first order analysis apparent polar wander paths are constructed for the major blocks we discuss the compatibilities and contradictions between the geological and paleomagnetic records a sequence of paleogeographic configurations taking into account geological constraints but remaining within paleomagnetic uncertainties is presented in general the major blocks were probably in contact throughout the permian and triassic but the jurassic was the key age during which most of the movement toward china s present configuration took place our reconstructions include certain details which are suggested by the paleomagnetic record but whose geological signatures seem to have been hidden by subsequent events during the cretaceous chinese poles agree with poles from other continents transferred onto eurasia at the second order we observe that for almost each period with sufficient data the paleomagnetic poles are streaked along a small circle centered on the sampling region indicating that much of china has been affected by small 20 differential rotations this we interpret as deformation caused in part by the extrusion of the chinese blocks away from the indian collision the complete annotated list of poles is given as an appendix

oxygen isotopes from biogenic apatites suggest widespread endothermy in cretaceous dinosaurs the much debated question of dinosaur thermophysiology has not yet been conclusively solved despite numerous attempts we used the temperature dependent oxygen isotope fractionation between vertebrate body water 18obody water and phosphatic tissues 18op to compare the thermophysiology of dinosaurs with that of non dinosaurian ectothermic reptiles present day 18op values of vertebrate apatites show that ectotherms have higher 18op values than endotherms at high latitudes due to their lower body temperature and conversely lower 18op values than endotherms at low latitudes using a data set of 80 new and 49 published 18op values we observed similar and systematic differences in 18op values 18o between four groups of cretaceous dinosaurs theropods sauropods ornithopods and ceratopsians and associated fresh water crocodiles and turtles expressed in terms of body temperatures tb these 18o values indicate that dinosaurs maintained rather constant tb in the range of endotherms whatever ambient temperatures were this implies that high metabolic rates were widespread among cretaceous dinosaurs belonging to widely different taxonomic groups and suggest that endothermy may be a synapomorphy of dinosaurs or may have been acquired convergently in the studied taxa

seasonal to sub seasonal palaeoenvironmental changes in lake sihetun lower cretaceous yixian formation ne china sedimentary properties of the fossil bearing deposits of lake sihetun yixian formation lower cretaceous were investigated on a high resolution sub millimetric scale data were obtained from three excavations and 50 thin sections lake evolution is subdivided into four phases of which phases 2 and 3 provided suitable conditions for excellent fossil preservation six microfacies are recognized within these two phases 1 allochthonous siliciclastic laminae 26 1 m thick on average 2 chrysophycean cyst accumulations 3 tuffaceous silt 4 lacustrine chemical precipitates 5 tuff and 6 normal graded sandy to silty siliciclastics phase 2 is characterized by microfacies 1 5 and phase 3 by microfacies 6 biofilms are common and mass occurrences of framboids pyrite pseudomorphs are occurring in sediments of phase 2 varves can be verified for microfacies 2 and 4 179 m thick thicknesses of microfacies 2 highly fluctuate depending on the occurrence of seasonal heavier rains which led to deposition of tuffaceous silt layers microfacies 3 meromictic conditions dominated phase 2 but recurrent mixing is demonstrated by short lived colonization events by a benthic invertebrate fauna the transition of phase 2 to holomictic phase 3 is marked by a dramatic increase in sediment yield associated with a change from dry to humid climates fossil preservation differs according to the diverse physical and chemical conditions during lake evolution phase 2 yields framboid replacement of organic tissue and excellent preservation of growth increments of clam shrimp carapaces which are poorly preserved in phase 3 conversely though exhibiting a different mode of preservation insect fossils are superbly preserved as dark stains sealed by silica coatings during phase 3

cretaceous sea surface temperature evolution constraints from tex86 and planktonic foraminiferal oxygen isotopes it is well established that greenhouse conditions prevailed during the cretaceous period 145 66 ma determining the exact nature of the greenhouse gas forcing climatic warming and climate sensitivity remains however an active topic of research quantitative and qualitative geochemical and palaeontological proxies provide valuable observational constraints on cretaceous climate in particular reconstructions of cretaceous sea surface temperatures ssts have been revolutionised firstly by the recognition that clay rich sequences can host exceptionally preserved planktonic foraminifera allowing for reliable oxygen isotope analyses and secondly by the development of the organic palaeothermometer tex86 based on the distribution of marine archaeal membrane lipids here we provide a new compilation and synthesis of available planktonic foraminiferal 18o 18opl and tex86 sst proxy data for almost the entire cretaceous period the compilation uses ssts recalculated from published raw data allowing examination of the sensitivity of each proxy to the calculation method e g choice of calibration and places all data on a common timescale overall the compilation shows many similarities with trends present in individual records of cretaceous climate change for example both sst proxies and benthic foraminiferal 18o records indicate maximum warmth in the cenomanian turonian interval our reconstruction of the evolution of latitudinal temperature gradients low 48 palaeolatitudes reveals temporal changes in the valanginian aptian the low to higher mid latitudinal temperature gradient was weak decreasing from 10 17 c in the valanginian to 3 5 c in the aptian based on tex86 ssts in the cenomanian santonian reconstructed latitudinal temperature contrasts are also small relative to modern 14 c based on low latitude tex86 and 18opl ssts minus higher latitude 18opl ssts compared with 20 c for the modern in the mid campanian to end maastrichtian latitudinal temperature gradients strengthened 19 21 c based on low latitude tex86 and 18opl ssts minus higher latitude 18opl ssts with cooling occurring at low middle and higher palaeolatitude sites implying global surface ocean cooling and or changes in ocean heat transport in the late cretaceous these reconstructed long term trends are resilient regardless of the choice of proxy tex86 or 18opl or calibration this new cretaceous sst synthesis provides an up to date target for modelling studies investigating the mechanics of extreme climates

xenoxylon a boreal fossil wood in the mesozoic redbeds of southeast asia potential for the stratigraphy of the khorat group and the palinspatic reconstruction of southeast asia abstract the fossil wood genus xenoxylon is reported in situ for the first time in thailand it originates from the indosinian terrane from the mesozoic continental redbeds of the phu kradung formation khorat group palinspatic reconstruction palaeobiogeography and correlation with other occurrences of the genus in southern china as well as in vietnam suggest a middle to late jurassic age for the phu kradung formation level yielding the fossil wood the dating of this formation is still controversial and thus our data is an important step towards a better understanding of its geological history and palaeoecology as well as of the southeast asia mesozoic continental redbeds significance for the evolution of the vertebrates

dinosaur bones fossils or pseudomorphs the pitfalls of physiology reconstruction from apatitic fossils abstract a prerequisite to any attempt to reconstruct thermophysiology of ancient animals through analysis of stable isotopes of oxygen is the assumption that apatitic fossils are isotopically unaltered parts of their original skeletons we suggest that sufficient evidence is available to seriously question this assumption because living bones contain about 1 3 by weight of organic matrix mass balance considerations show that at least half of an apatitic fossil must be new material added post mortem furthermore living apatitic skeletons contain almost no rare earth elements and uranium whereas apatitic fossils bear high concentrations of these elements additionally we found that while in living fish correlation between 18o of oxygen in the phosphate and that in the carbonate of apatite is poor these two values are linearly correlated in fossil fish this suggests diagenetic recrystallization has taken place perfect preservation of micro textures such as haversian canals does not prove the pristine condition of a fossil some of the most beautifully preserved fossils are highly silicified most apatitic fossils probably are pseudomorphs replacing original skeletal elements whereas distribution of stable isotopes of oxygen in fossils might provide information about their burial environment it could be misleading in attempts to interpret the organisms physiology this cautionary note is supported by the similarity of 18op in bones of coexisting fossil fish dinosaurs and various other reptiles at different latitudes the overlap of predicted 18op values in fish and mammals living in contact with the same environmental water also weakens the hope that ectotherms can be distinguished from endotherms by the isotopic composition of oxygen in their bones and teeth

paleobiology and skeletochronology of jurassic dinosaurs implications from the histology and oxygen isotope compositions of bones fossil biogenic phosphate of fast growing primary bone tissue of dinosaurs can preserve a histologic and isotopic time series of annual seasonality in temperature variations similar to tooth enamel and other accretionary skeletal phases such as corals or wood on two bone fragments from sympatric dinosaurs with different histologic patterns of bone growth high resolution oxygen isotope profiles were analyzed along the radial direction of bone growth the investigated specimens are from the jurassic shishugou formation in the junggar basin nw china and have distinct patterns of compositional variation a fibrolamellar dinosaur bone with multiple lines of arrested growth lags and periodic growth cycles of decreasing bone laminae thickness displays a cyclic intra bone variation in 18o values of about 2 corresponding with the lags these growth cycles in fast growing fibrolamellar bone provide evidence for seasonal growth of dinosaurs in lower latitudes 45 n possibly influenced by a monsoon type paleoclimate seasonal changes in temperature and water supply are consistent with the oxygen isotope composition measured in dinosaur bone phosphate as well as with growth rings in contemporaneous fossil conifer wood from the same locality in contrast a plexiform sympatric sauropod bone displays continuous growth free of lags and has a lower intra bone variation of 0 8 differences in bone histology are also reflected in the oxygen isotopic composition and its intra bone variability indicating different physiological responses to external climatic stress between sympatric dinosaur species seasonal intra bone oxygen isotope variations combined with bone histology may thus yield new insights into species specific response to climatic stress and its influence on dinosaur growth formation of growth marks growth rates as well as dinosaur thermophysiology

oxygen isotope variations in phosphate of biogenic apatites i fish bone apatite rechecking the rules of the game abstract the major advantage of the oxygen in phosphate isotope paleothermometry is that it is a system which records temperatures with great sensitivity while bone and teeth building organisms are alive and the record is nearly perfectly preserved after death fish from seven water bodies of different temperatures 3 23 c and different 18 o values 16 to 3 of the water were analysed the 18 o values of the analysed po 4 vary from 6 to 25 the system passed the following tests a the temperatures deduced from isotopic analyses of the sequence of fish from lake baikal are in good agreement with the temperatures measured in the thermally stratified lake b the isotopic composition of fish bone phosphate is not influenced by the isotopic composition of the phosphate which is fed to the fish but only by temperature and water composition isotopic analysis of fossil fish in combination with analysis of mammal bones should be a useful tool in deciphering continental paleoclimates

the evidence and implications of polar ice during the mesozoic abstract the mesozoic perhaps representing the longest period of warmth during phanerozoic earth history contains in general sparse and frequently equivocal evidence for polar ice although this time is undoubtedly punctuated by oscillations in climate whether sufficient to lead to polar cooling and the formation of polar ice an inviting mechanism to account for faunal and floral distribution patterns and large scale sea level change has been widely debated mesozoic evidence for glacial conditions includes abraded rock surfaces generally unsorted stone rich beds and the presence of dropstones rafted by ice within a finer grained host sediment faunal and floral evidence has also been utilised to determine the presence or absence of cold or sub freezing polar conditions together with more indirect evidence for glacial conditions derived from general circulation model gcm simulations of climate the analysis of clay mineral distributions glendonite abundance and palaeontological and sedimentological evidence for globally synchronous sea level change the extent of possible glacial environments during the mesozoic has been established by plotting published reports of glacial sediments on palaeogeographic reconstructions the general clustering of evidence at high palaeolatitudes suggests that the extent of polar ice during the mesozoic is likely to have been approximately one third the size of the present day based on such evidence a number of episodes of cold or sub freezing polar climates during the bajocian bathonian tithonian volgian valanginian and aptian are recognised evidence exists possibly also for a cold episode during the early jurassic pliensbachian although poorly constrained owing to limited biostratigraphical control the longevity of these events may be represented by a cold snap within a stage although undoubtedly the possible smearing of ages may have had the effect of lengthening and hence promoting the importance of these proposed events the climate regime of the earth during these times may be hypothesised to be characterised by a relatively steep pole to equator temperature gradient where low latitude regions are as warm or warmer than today the evidence to support such reasoning includes sharp increases in the areal distribution of both glendonites and deposits with affinities to glacial tillites and dropstones for these times coincidental falls of sea level arid events and an increased bipolarity of faunas at these times imparts further confidence that these events were of a magnitude to effect the earth as a whole

oxygen deficiency in lake sihetun formation of the lower cretaceous liaoning fossillagerstatte china the redox state of lake sihetun represented by the lower cretaceous yixian formation western liaoning china is evaluated to understand the formation of this konservat lagerstatte lake evolution is subdivided into four phases of which phases 2 and 3 exhibit excellent fossil preservation exceptional preservation and mass mortality events within phase 2 were previously attributed to synsedimentary volcanism and oxygen deficiency however the volcanic trigger for mass mortality events remains enigmatic and distinction between anoxia and dysoxia has not been put forward so far to resolve the redox state of the lake during phase 2 5394 diameters of pyrite framboid pseudomorphs in 29 thin sections from three localities have been measured framboid size distributions reveal that lake sihetun was governed by dysoxic bottom waters with spells of anoxia recording pronounced environmental stress hence holomictic eutrophic conditions were episodically replaced by meromictic interludes spatial variations in redox state were common and oxic conditions were detected in two of the three studied localities concentrated iron sulphide layers resulted from biofilms at the lake floor or the development of microenvironments around organic remains which preserved highly reactive organic compounds in contrast sediments of phase 3 record oxic conditions and an entirely holomictic lake

a refugium for relicts the yixian formation in china s liaoning province has yielded many spectacular fossils notably several remarkably complete feathered dinosaurs yet its age has been controversial accurate radiometric dating now shows unambiguously that these beds are from the early cretaceous providing a new temporal calibration for assessing the evolution of animal and plant life from that period

the evolution of latitudinal temperature gradients from the latest cretaceous through the present abstract latitudinal temperature gradients are a defining characteristic of the climate system using thermometric indicators including 18o plant and animal fossils glycerol dialkyl glycerol tetraether gdgt proxies and clumped isotope estimates we document marine and terrestrial temperature gradients for the latest cretaceous late paleocene early eocene early oligocene pliocene and recent the changes in gradients reflect the transition greenhouse to icehouse conditions the evolution of latitudinal temperature gradients in marine and terrestrial realms are similar but has some distinctive differences marine temperatures are generally warmer than those on land except for the late paleocene early eocene the marine records show distinct inflection points at 30 and 50 latitude indicating the existence of frontal systems in the ocean except for the late paleocene early eocene the marine records show an increasingly steeper trend from latest cretaceous through recent being most pronounced after the early oligocene greenhouse icehouse transition this trend reflects the increasing intensity of high latitude and polar cooling as the icehouse state developed during the late paleocene early eocene the oceans were characterized by slightly warmer tropics and much warmer higher latitudes than at present the continents have generally had tropical temperatures like those of today varying by

early cretaceous palaeoceanography of the greenland norwegian seaway evidenced by calcareous nannofossils abstract reconstructions of the palaeoclimate of the early cretaceous are controversial varying from a warm temperate greenhouse world to icehouse conditions we studied calcareous nannofossil assemblages of sediments from north east greenland wollaston forland and kuhn o of late ryazanian barremian age in order to better understand the palaeoclimate and palaeoceanography of the high latitudes the calcareous nannofossil assemblages are characterized by abundant crucibiscutum spp and watznaueria spp biscutum constans and other boreal taxa they show also influxes of tethyan and low to mid latitudinal taxa like nannoconids e g nannoconus bermudezii nannoconus dolomiticus nannoconus steinmannii pentaliths micrantholithus hoschulzii micrantholithus obtusus conuspheres speetonia colligata and cruciellipsis cuvillieri in the upper ryazanian and lower hauterivian reconstructed surface water conditions indicated by fluctuations in the assemblage compositions suggest cool conditions for the late ryazanian a cold climate for the valanginian and warm climatic conditions for the hauterivian barremian high meridonial temperature gradients and cool cold climatic conditions in the high latitudes caused supposedly the formation of deep water in the south anyui gulf in the late ryazanian valanginian palaeoceanographic changes reflected in a counter balanced ocean current system in the greenland norwegian seaway allowed tethyan biota to spread as far north as north east greenland during the late ryazanian

production preservation and prediction of source rock facies in deltaic settings abstract this article hypothesizes that production and preservation of source rock type facies in deltaic systems both landward and seaward of a coastline is mutually exclusive time successive and related to the dynamics of relative sea level sedimentologic research in the holocene mississippi and rhone delta complexes suggests that rheotrophic peats and associated organic rich beds preferably accumulate in the accommodation space created behind landward stepping shorelines in a transgressive systems tract tst such a setting also allows for a sufficient supply of recharging fresh nutrient rich groundwater into the peat forming mires kosters e c suter j r 1993 facies relationships and systems tracts in the late holocene mississippi delta plain journal of sedimentary petrology 63 4 727 733 independently carried out quantitative paleoecological studies in the same delta systems and in addition in the orinoco and po deltas suggest that in a progradational setting highstand systems tract hst seasonally discharged nutrient and sediment laden river waters on the shelf may give rise to anoxia or dysoxia subsequent overfertilization of the shelf leads to accumulation of organic rich mud belts on the shelf vanderzwaan g j jorissen f j 1991 biofacial patterns in river induced anoxia in tyson r v pearson t h eds modern and ancient continental shelf anoxia geological society of london special publication no 58 pp 65 82 thus production and preservation of source rock type facies landward of a shoreline as peats and related sediments is preferred in a tst when accommodation space and nutrient supply are landward of the shoreline vice versa production and preservation of such facies seaward of a shoreline as organic rich shelf muds occurs preferentially in a highstand systems tract in that situation accommodation space is on the shelf where river fed nutrients are supplied as well this hypothesis suggests further potential for application of sequence stratigraphic concepts for improved understanding of the occurrence of source rock type facies

δ18o and ree contents of phosphatic brachiopods a comparison between modern and lower paleozoic populations 18o values of both carbonate 18 7 25 1 and phosphate 15 1 16 7 components of the francolite from the fossil brachiopod shells are interpreted as the result of a partial resetting of pristine isotopic compositions the similarity of hat shape ree patterns of some lower ordovician linguloids with those of extant littoral specimens suggests the preservation of a 500 myr old record of ree marine chemistry in agreement with the known paleogeography the phosphatic brachiopods have been deposited in a coastal environment under shallow and oxygenated marine waters however the contents and distribution of ree in some strongly altered brachiopod shells reveal an alteration of the original negative ce anomalies and both nd and sm enrichments that transformed the initial hat shape patterns of linguloids into strongly convex or bell shape patterns

fossil crocodilians as indicators of late cretaceous and cenozoic climates implications for using palaeontological data in reconstructing palaeoclimate abstract that the earth s climate has cooled over the last 100 million years has been recognized since the early nineteenth century the transition from the hot house world of the cretaceous a time interval without significant polar icesheets to the ice house world in which we now live today the dynamics process responsible for this change are being examined using computer models especially general circulation models gcm s through such work our understanding of the dynamics of the earth system improves and our ability to predict future trends is enhanced but the success of modelling experiments can only be assessed by comparing results with observations the pattern which for palaeoclimate are drawn exclusively from the geological record palaeoclimate interpreted from geological data is invariably based on analogy with the recent the validity of which depends on corroboration from multiple lines of evidence this requires the compilation and investigation of large global datasets of well constrained geological climate proxies this study uses the palaeodistribution of fossil crocodilians to examine the spatial distribution of palaeoclimate during this transition fossil crocodilians have a relatively good fossil record and are climatically limited in the recent they also provide a manageable global dataset with which to investigate other issues that impinge on the use of geologic data for reconstructing palaeoclimate taphonomy sampling effects time averaging tectonics and for fossils palaeobiogeography and evolution as such this study provides a possible template for examining other climate proxies in order to validate and hone palaeoclimatic interpretations an analysis of modern crocodilians indicates that temperature is the principal influence on their global distribution with the coldest month mean temperature cmm of 5 5 c marking the minimum thermal limit for the group corresponding today to a minimum mean annual temperature mat of 14 2 c the duration of warmth during the year partly indicated by the mean annual range of temperature mart is also important as this affects early juvenile development and survival the presence of standing water provides an essential thermal buffer against temperature extremes by analogy the palaeodistribution of fossil crocodilians suggests the following during the late cretaceous and early palaeogene mat s in excess of 14 2 c cmm s 5 5 c permeated throughout mid latitudes and coastal regions in high latitudes during the oligocene the restriction of fossil crocodilians to low latitudes suggests high latitude cooling as indicated by numerous other lines of evidence coeval restriction of crocodilians to coastal regions in mid latitude north america and much of asia consistent with increased seasonality and aridification in continental interiors may reflect local orographic changes as well as global climate change during the miocene fossil crocodilians return to the great plains of north america but do not reoccupy the continental interior of asia by the pliocene crocodilians are again restricted to low latitudes and coastal regions in mid latitudes coincident with further high latitude cooling and aridification and cooling of mid latitude continental interiors minor distributional changes during the holocene may reflect human effects

environment and ecology of east asian dinosaurs during the early cretaceous inferred from stable oxygen and carbon isotopes in apatite abstract during the cold late barremian early albian interval terrestrial environments in east asia were populated by rich and diverse vertebrate faunas characterized by a strong provincialism the latitudinal gradient of temperature and the existence of geographic barriers likely accounted for some aspects of this heterogeneous distribution of faunas other factors however such as local environmental conditions and interactions within vertebrate communities which could have influenced their distribution have not yet been fully identified and understood therefore new and published oxygen and carbon isotope compositions of apatite from chinese and thai reptiles dinosaurs crocodilians and turtles have been analyzed and interpreted in terms of ecology local air temperature and precipitation amounts differences in carbon and oxygen isotope compositions between various groups of sympatric plant eating dinosaurs sauropods ornithopods and ceratopsians indicate food resources partitioning among them most likely to avoid competition mid latitude environments where the jehol biota flourished were submitted to cool temperate climatic conditions with mean air temperature mat of 10 4 c and mean annual precipitations map of about 600 mm yr compatible with the existence of forest environments by contrast sub tropical regions characterized by mat of about 20 25 c were either submitted to high amounts of seasonal precipitations of about 1200 mm yr in thailand or to significant aridity map of about 400 mm yr in south china this difference in precipitation regime between thailand and south china may be attributed to the occurrence of the coastal cordillera extending along the east margin of the south china block these mountain ranges likely prevented humid air masses from the pacific to penetrate some parts of south china thus generating a rain shadow effect mosaic environments characterizing east asia during the late early cretaceous may have acted as a cradle for the origination of advanced dinosaur taxa that subsequently radiated over eurasia and north america during the late cretaceous

the stratigraphy and paleoenvironment of a lycoptera bed site in eastern inner mongolia china correlation with the fossiliferous lower cretaceous strata in western liaoning abstract the stratigraphy and the fossil assemblage of a lower cretaceous lycoptera bed of the xinganling group in naketa arongqi area inner mongolia china are described and the paleoenvironment is discussed as it relates to the jehol biota the naketa fossil bed belongs to the lower part of volcanic sedimentary jiufengshan formation and preserves a typical eel eosestheria ephemeropsis trisetalis lycoptera davidi faunal assemblage which indicates a strong affiliation to the jehol biota of western liaoning china the fossil bed was deposited in a shallow to semi deep lacustrine setting with occurrence of oil shale facies and this is different from the lycoptera bed of the yixian formation and more similar to the overlying jiufotang formation in western liaoning a layer of volcanic tuffite within the fossil bed is dated as 121 6 0 47 ma using the zircon u pb isotopic dating method this age is contemporary with the age of the base of jehol biota producing jiufotang formation in western liaoning thereby supporting the biostratigraphic correlation however the genus lycoptera is almost entirely absent in western liaoning with only one species in the jiufotang formation where the dominant fish genus is jinanichthys therefore lycoptera in the great xing an mountain areas appears to have a longer record than in western liaoning which likely indicates that the fish fauna changed earlier in western liaoning and this observation supports the hypothesis that the yanliao area was the diversification center of some cretaceous new groups in ne asia preliminary analysis of the taphonomy and the geology indicates that the mass mortality of fish at the naketa site may not be related to volcanism additional taphonomic investigations would allow a better understanding of the early cretaceous aquatic paleoecology and paleoenvironment in the volcanic rifting regions the great xing an mountain area is a new opportunity for expanding the research on the jehol biota beyond the core localities in western liaoning

oxygen isotopes of east asian dinosaurs reveal exceptionally cold early cretaceous climates early cretaceous vertebrate assemblages from east asia and particularly the jehol biota of northeastern china flourished during a period of highly debated climatic history while the unique characters of these continental faunas have been the subject of various speculations about their biogeographic history little attention has been paid to their possible climatic causes here we address this question using the oxygen isotope composition of apatite phosphate from various reptile remains recovered from china thailand and japan values indicate that cold terrestrial climates prevailed at least in this part of asia during the barremian early albian interval estimated mean air temperatures of about 10 4 c at midlatitudes 42 n correspond to present day cool temperate climatic conditions such low temperatures are in agreement with previous reports of cold marine temperatures during this part of the early cretaceous as well as with the widespread occurrence of the temperate fossil wood genus xenoxylon and the absence of thermophilic reptiles such as crocodilians in northeastern china the unique character of the jehol biota is thus not only the result of its evolutionary and biogeographical history but is also due to rather cold local climatic conditions linked to the paleolatitudinal position of northeastern china and global icehouse climates that prevailed during this part of the early cretaceous

diagenesis and the reconstruction of paleoenvironments a method to restore original δ18o values of carbonate and phosphate from fossil tooth enamel abstract intra tooth 18 o variations within the carbonate 18 oc and phosphate 18 op components of tooth apatite were measured for miocene and pliocene hypsodont mammals from afghanistan greece and chad in order to evaluate the resistance of enamel to diagenetic alteration application of water apatite interaction models suggest that the different kinetic behaviours of the phosphate water and carbonate water systems can be used to detect subtle oxygen isotope disequilibria in fossil enamel when intra individual variations are considered selective alteration of the oxygen isotope composition from the carbonate component of afghan and greek enamels suggests inorganic isotopic exchange processes microbially induced isotopic exchange for phosphate is demonstrated for the first time in enamel samples from chad in association with extensive recrystallization in chad 18 op values were derived from partial isotopic exchange with fossil groundwater during early diagenesis mass balance calculations using average carbonate content in enamel as a proxy for recrystallization and the lowest 18 op value of dentine as a proxy for the isotopic composition of the diagenetic fluid indicate that diagenesis can alter 18 op by as much as 3 in some enamel samples this diagenetic alteration is also responsible for a decrease in intra individual variations of up to 1 in affected specimens the effects of diagenesis on 18 op values of fossil enamel are not systematic however and can only be estimated if sequential 18 op and 18 oc analyses are performed on fossil enamel and dentine reconstruction of large temporal or spatial scale paleoclimates based on 18 op analyses from mammalian teeth cannot be considered valid if enamel has been affected by bacterial activity or if the data cannot be corrected for diagenetic effects

thermal evolution of cretaceous tethyan marine waters inferred from oxygen isotope composition of fish tooth enamels 1 the evolution of subtropical 30 35 n upper ocean temperatures through the cretaceous is inferred from the oxygen isotope compositions of 64 fish teeth enamel coming from the western tethyan platform mean 18o values of 22 at the berriasian valanginian boundary decrease with oscillations to 18 5 around the cenomanian turonian boundary and progressively increase to 21 5 by the end of the cretaceous the similarity of this oxygen isotope curve for bioapatites from platform environments with those for foraminifera and bulk carbonates that were deposited in deeper waters and at other paleolatitudes indicates that they record global climatic signals major cooling events at the million year scale can be distinguished 1 at the berriasian valanginian boundary and 2 during the earliest late valanginian a third cooling event is detected during the earliest aptian these events already proposed as icehouse interludes during the lower cretaceous are also recorded at subtropical latitudes a progressive warming is identified from the aptian to the cenomanian turonian interval that corresponds to a thermal optimum and then upper ocean temperatures decreased to the maastrichtian minimum isotopic temperatures range from 15 c to 28 c assuming a 18oseawater of 1 for an ice free world taking more realistic 18oseawater values of 0 for tropical waters during glacial periods within the berriasian valanginian interval and earliest aptian or with above average salinities possibly the maastrichtian temperatures are increased by 4 5 c temperature differences between climatic extremes of the valanginian and cenomanian turonian are estimated to have been 10 c latitudinal thermal gradients for the albian cenomanian turonian and maastrichtian were 0 2 0 3 c latitude and thus weaker than modern oceanic values at about 0 4 c latitude

estimating slope stability reduction due to rain infiltration mounding rainwater can infiltrate into slopes and earth dams given sufficient infiltrating rainfall intensity frequency and time the phreatic line within the slope or dam will mound above its otherwise steady state position such a mound will increase downslope seepage and reduce downslope stability this paper develops an approximate method for solving this transient seepage mounding problem and the resulting reduction in stability it shows the following variables will reduce stability increased rainfall intensity and duration decreasing permeability especially over the 10 2 10 4 mm s range and its anisotropy increasing the slope cotangent decreasing the depth to an impermeable underlayer or increasing the depth to a permeable underlayer increasing size and effective porosity has only a time effect in special circumstances the mounding effect can reduce slope stability by 50 and the paper includes a slope case history example

thermal excursions in the ocean at the cretaceous tertiary boundary northern morocco δ18o record of phosphatic fish debris c lecuyer p grandjean j r o neil h cappetta and f martineau 1993 thermal excursions in the ocean at the cretaceous tertiary boundary northern morocco c lso record of phosphatic fish debris palaeogeogr palaeoclimatol palaeoecol 105 235 243 high precision oxygen isotope analyses were made of phosphate extracted from 17 samples of nektonic and benthic fish debris sampled across the stratigraphic cretaceous tertiary boundary in northern morocco a refinement of the silver phosphate method was used to isolate phosphate from biogenic materials measured 180 values of 18 6 20 5 o are interpreted as reflecting high resolution thermal variations that affected the ocean water column of the western tethys the warm 27 c water masses that characterized maastrichtian times underwent rapid cooling and stabilized at an average temperature of 19 c during the dano montian and thanetian this period of constant and cool temperature was followed by a relatively rapid but more gradual warming to about 25 c achieved in the middle ypresian significant small shifts in 6180 values between nektonic and benthic fauna recorded only during the stages of rapid warming or cooling may correspond to averaged thermal differences within the water column that developed in response to global climatic changes the indicated temperature distribution could have been caused by thermal changes in the atmosphere rather than some signal carried by deep ocean currents the oxygen isotope data coupled with previous measurements of ree and end ti on the same samples support the suggestion that paleo pacific westward currents progressed as far as the northwestern part of the african platform at the end of the cretaceous period

stable isotope composition and rare earth element content of vertebrate remains from the late cretaceous of northern spain lano did the environmental record survive abstract oxygen and carbon isotope measurements have been performed on phosphatic remains from faunal associations dinosaurs crocodiles turtles and fish of the late cretaceous continental and marine sediments from northern spain basque country the environmental meaning of the oxygen isotope record in fossil reptiles is discussed on the basis of known paleoecology modern fauna analogs and apatite chemistry rare earth elements ree co32 and po43 contents fossil remains in sandstones and argillites from two localities urria and cuezva have low down to 16 and scattered 18o po4 co3 and 13c values with ree patterns characterized by strong middle ree enrichments these geochemical compositions of the biogenic apatites have most likely been acquired during a multi stage late diagenesis involving complete recrystallization of the apatite in the presence of aqueous fluids ree contents of fossils preserved in the clayey sands from the site of lano suggest that samples have only been affected by early diagenesis despite the diversity of analyzed taxa and the close association of marine sharks and rays and freshwater species crocodiles and turtles evolving in a littoral environment the narrow range of phosphate 18o values is interpreted as reflecting the temperature and isotopic composition of groundwaters that prevailed in the burial environment the potential information relative to the physiology and thermal regime of the vertebrates has been erased during the process of early diagenesis if all oxygen in the phosphate has exchanged with groundwaters the oxygen isotope composition of vertebrate remains suggests that a warm climate t 20 25 c prevailed in northern spain during the late cretaceous

tectonic implications of new late cretaceous paleomagnetic constraints from eastern liaoning peninsula ne china 1 a paleomagnetic study has been carried out in the east of the tan lu fault in liaoning province ne china to understand the timing of tan lu fault activity samples aging from early paleozoic to late mesozoic from 51 sites have been analyzed paleozoic and late permian early triassic rocks are remagnetized by the recent geomagnetic field however late cretaceous between 118 and 83 ma red tuffaceous sandstone passes a positive fold test shows no present earth field characteristic remanent magnetization carried by both magnetite and hematite presents a solo normal polarity and thus provides the only reliable paleomagnetic data in this study the paleomagnetic pole calculated from these rocks p 59 4 n p 205 5 e and a95 7 3 is statistically undistinguishable from all available cretaceous paleomagnetic data from eastern liaoning korean peninsula indicating that these areas may belong to a single tectonic unit here named the east liaoning korea elk block at least since the late cretaceous conversely a significant discrepancy between the elk block and chinese block i e north and south china blocks characterized by a differential rotation 22 5 10 2 with a negligible latitudinal displacement 0 8 6 1 is demonstrated this result indicates first that the left lateral displacement along the tan lu fault if any must have occurred before the late cretaceous and second that the korean block can not be considered as a rigid part of north china block sedimentological and structural evidence show that the meso cenozoic triangle shaped plain consisting of songliao xialiaohe sanjiang zeya and other smaller basins developing in northeast china and southeast russia south of the mongol okhotsk belt experienced a heterogeneous rifting from the late jurassic to tertiary the variable amount of extension larger in the northeast 300 km than in the southwest 80 km is probably related to the clockwise rotation of the elk block centered at the south of the bohai bay basin this result shows that a significant segment of the east eurasian margin more than 1000 km long experienced differential rotation in cenozoic times