a palynofacies study of past fluvio deltaic and shelf environments the oligocene miocene succession north sea basin a reference data set for similar cenozoic systems abstract correct interpretations of depositional environments are fundamental for evaluating the geological history of a sedimentary basin palynofacies analyses are a valuable supplement to sedimentological and seismic studies in order to develop a palynofacies reference dataset for fluvio deltaic and shelfal successions a study of the assemblages of sedimentary organic particles from seven different well defined depositional environments within the uppermost oligocene lower miocene succession onshore denmark eastern north sea basin has been performed the study deals with the following environments floodplain lagoon washover fan flat prodelta shoreface offshore transition and shelf the sedimentary organic particles were grouped into four major categories 1 structured wood particles 2 amorphous organic matter aom in the present study mainly consisting of partly degraded vitrinite 3 cuticle and membranes and 4 palynomorphs the palynomorphs were grouped into eight subcategories 1 microspores 2 non saccate pollen 3 bisaccate pollen 4 botryococcus 5 other freshwater algae 6 fungal hyphae and spores 7 acritarchs and 8 organic walled dinoflagellate cysts a combination of a univariate box plots and a multivariate principal component analysis pca of the palynofacies data clear revealed the quantitative characteristics and variations within each discrete environment as well as their principal similarities and differences in spite of some natural overlaps for example between the lagoon and offshore transition environments the data revealed distinct characteristics e g a strong dominance of wood particles in the shoreface environment a strong dominance of bisaccate pollen in the washover fan flat environment and a near absence of dinocysts in the floodplain environment an overall increase in relative abundances of dinocysts and a decrease in abundances of non saccate pollen in the proximal distal trend were also outlined this study outlines a palynofacies reference dataset that can be used as a tool for interpreting depositional environments in equivalent settings preferentially combined with other information such as seismic data well logs and or lithology

anomalies in global carbon cycling and extinction at the triassic jurassic boundary evidence from a marine c isotope record this study investigates whether the end triassic biotic crisis was coupled with a perturbation of the marine c isotope budget the marine c isotope signature serves as a proxy of the marine carbon reservoir and ultimately of the global c cycle a continuous shallow water marine limestone succession from the western southern alps bergamasc alps northern italy provides information on the end triassic biotic crisis and on the evolution of the marine carbon reservoir across the triassic jurassic t j boundary the established carbonate c isotope curve is marked by a negative c isotope pulse coinciding with the disappearance of the end triassic benthic faunal assemblage and a widespread rhaetian carbonate platform drowning event the negative spike is followed by a positive c isotope excursion starting at the palynological t j transition the negative c isotope pulse may have resulted from the sudden release of gas hydrates the positive isotope excursion records a global change in organic carbon burial rates probably in response to elevated atmospheric co2 levels at a time of massive volcanic activity in the central atlantic magmatic province high co2 levels were responsible for the end triassic biocalcification crisis carbonate platform collapse and possibly the sudden release of methane from gas hydrate

high resolution image treatment in ichnological core analysis initial steps advances and prospects abstract ichnological studies have become popular during the last decades particularly those associated with the development of two major concepts the ichnofacies model and ichnofabric approach they have driven ichnology into diverse fields of earth sciences including paleoecology sedimentology paleoceanography and basin analysis as well as applied fields for the oil and gas industry and aquifer characterization whereas early ichnological analyses focused on outcrops later the number of ichnological studies on well cores increased noticeably still ichnological research on cores is hampered by certain limitations i e mainly narrow exposed surface and the characterization of ichnological properties is complicated when cores are involved to facilitate ichnological analysis in cores from modern deposits several techniques among them x rays magnetic resonance and computed tomography have been used with the development of computer software a new high resolution image treatment has emerged as a powerful tool in different branches of ichnological studies especially for cores from modern marine deposits because applications are numerous and perhaps not familiar to all the scientific community this paper provides an overview of the usefulness of image treatment in ichnological analysis its first steps and subsequent development the novel techniques most recently used in the study of cores from modern marine deposits and some challenges for future research

ichnology of the late carboniferous hoyada verde formation of western argentina exploring postglacial shallow marine ecosystems of gondwana abstract the postglacial interval of the upper carboniferous hoyada verde formation of western argentina contains an ichnofauna dominated by psammichnites plummeri and psammichnites implexus with minor occurrences of ptychoplasma vagans treptichnus bifurcus lingulichnus verticalis protovirgularia isp lockeia isp palaeophycus isp scarce arthropod trackways and some bilobate structures the particular features of this association indicate a depauperate expression of the cruziana ichnofacies and suggest a context that differs from the expected in normal shallow marine settings i e archetypal cruziana ichnofacies integration of sedimentologic ichnologic sequence stratigraphic and paleontologic data points to a prograding deltaic system influenced by wave action trace fossils have been extensively used to recognize stressed brackish water environments in the late paleozoic of gondwana however the recognition of stressed settings needs to take into consideration the specific paleogeographic context of glacially influenced gondwanan settings a postglacial open sea adjacent to a paleotopographic high is considered as a possible scenario for the hoyada verde formation in this particular setting coastal biotas could have been influenced to some degree by the salinity gradient triggered by freshwater release near to melting ice masses stored in highlands and also by freshwater plumes due to longshore currents regional factors e g proximity to highlands and climate may have played an important role in controlling the characteristics of gondwanan ichnofaunas this suggests that the distinction between normal marine and brackish water settings in glacially influenced environments using trace fossils may not be as straightforward as in non glacial settings

the ellipsactinia limestones of the marsica area central apennines a reference zonation model for upper jurassic intra tethys reef complexes abstract this study presents a new and innovative distribution model of the main reef builders that thrived on bioconstructed margins of upper jurassic intra tethys platforms the proposed model is based on the zonation of an upper jurassic reef complex presently exposed in the central apennines excellent exposures allow the reconstruction of the reef profile across the platform margin biota are mainly represented by corals and calcified demosponges distributed with different amounts and aggregating structures along the reef complex microencrusters represent a secondary but important component that actively contributes to the reef construction process reef builders are distributed in variable quantities and with variable aggregating structures along the reef complex revealing a strong reef zonation like the biota the sedimentary features grain size sorting and reworking degree bioerosion cement crusts and cavities show a distinctive distribution along the reef complex three main zones have been recognized along the studied reef complex an internal more protected and deeper zone corresponding to a relatively deep back reef lagoon is dominated by corals and chaetetids a central zone reef flat where well preserved coral bioconstructions give rise to a true but discontinuous framework and a more external zone corresponding to the reef crest characterized by the shallowest depths recorded across the reef complex and dominated by stromatopores the latter forms mound shaped structures playing a role essential for the zoned character of the reef complex these structures actively contribute to the construction of a moderately high topographic relief in the reef crest

organism substrate interactions and astrobiology potential models and methods abstract organism substrate interactions and their products biogenic structures are important biosignatures on earth this study discusses the application of ichnology the study of organism substrate interactions to the search for present and past life beyond earth three main questions are addressed 1 why to look for biogenic structures i e traces and ichnofabrics beyond earth 2 what biogenic structures to expect on other planets moons and asteroids 3 how to study extraterrestrial biogenic structures review of terrestrial evidence highlights a set of properties that make traces and ichnofabrics important for the search of potential extraterrestrial life trace fossils preserve the activity of soft bodied organisms biogenic structures are resilient to processes that obliterate other biosignatures i e mechanical and chemical degradation diagenesis tectonism and metamorphism traces are very visible biosignatures traces indicate environment and behaviour traces can be universal biosignatures i e biosignatures ideally suited for detecting any type of life a model of organism substrate interactions beyond earth is here proposed expected extraterrestrial traces are those that manifest behaviours that allow to maintain homeostasis excavations meandering traces and biodeposition structures most of the existing rovers and orbiters provide basic instruments for searching these traces it is here suggested that the search for extraterrestrial biogenic structures by rovers would also benefit from artificial adjustable lighting gpr lidar and drilling equipment with optical televiewer in this study open access databases of rover and orbiter imagery have been searched for traces and ichnofabrics but no unquestionable evidence of biogenic structures beyond earth has been found besides those produced by humans this sounds along the lines of the famous fermi paradox if the universe is teeming with aliens where are their traces results of this search show that habitable environments are not the only place to look for biogenic structures non habitable environments such as moons without atmosphere can favour the preservation of shallow tier traces the better preservation potential of traces compared to other biosignatures greatly widens the issue of planetary protection including the interaction between astronauts or vehicles and the substrate may produce disturbances although this study highlights a new direction of study with the tools and concepts of ichnology dialogue between the astrobiological and ichnological communities is needed to use its full potential and possibly answer one of the major questions of science does life exist beyond earth

bioturbation in burgess shale type lagerstatten case study of trace fossil body fossil association from the kaili biota cambrian series 3 guizhou china abstract cruziana gordia planolites rusophycus and trichophycus are common ichnological elements of the kaili biota new discoveries based on the examination of 323 specimens include eldoniids echinoderms trilobites monoplacophorans and non biomineralizing arthropods that are associated with trace fossils based on the observed effects of bioturbation on the preservation of five different animal groups it is clear that infaunal scavengers deposit feeders were periodically active on the kaili sea floor and were able to reach historic layers yielding exceptionally preserved fossils in general the average level of infaunal activity is absent to moderate ichnofabric index i i 1 to 3 in the kaili substrate by contrast the phycodes beds are completely disturbed by infaunal activity i i 5 observed burrow diameter ranges from diminutive 0 2 mm to normal up to 4 2 mm computed tomography allows us to visualize the precise geometry of the trace fossil body fossil association in three dimensions we concluded that although some kaili infaunal animals could bore through the biomineralized echinoderms they did not appear to have scavenged upon these echinoderms based on our three dimensional reconstruction furthermore kaili burrowers can reach the historic layers containing exceptionally preserved fossils without altering soft tissue preservation on the other hand we used conventional techniques to reveal that one burrow is filled with fecal pellets 100 200 m at its terminal end because most burrows are filled with yellow brown coarse sediment and because there is no compositional difference between the fecal pellets and the surrounding coarse sediment within the burrow the origin of the yellow brown coarse sediment is interpreted here as parautochthonous and or autochthonous and as a result of sediment reworking by deposit or suspension feeders the relative scarcity of soft part preservation in the kaili biota compared to the older chengjiang biota and the younger burgess shale biota may be the result of post burial bio disturbance due to the relatively high intensity of local bioturbation it is plausible that oxygenation in deeper sediments facilitated by bioturbation allowed carcasses in the kaili biota to undergo a more extensive period of normal decay prior to final burial than in other cambrian konservat lagerstatten

chronology of the central atlantic magmatic province implications for the central atlantic rifting processes and the triassic jurassic biotic crisis abstract the central atlantic magmatic province camp is among the largest igneous provinces on earth emplaced synchronously with or just prior to the triassic jurassic t j boundary ca 200 ma in great part due to the controversial connection between the occurrence of camp and the events of the t j boundary the demand for better constraints on the duration and eruptive chronology of this province has increased more than 100 new 40 ar 39 ar ages have been published in the last 15 years with more than half of these in the last 3 years a careful review and selection of available ages as well as the publication of 16 new ages from the carolinas newark basin usa french guyana and morocco are presented judicious selection yields a total of 58 accepted age determinations for camp magmatism ranging from 202 to 190 ma covering every part of the camp a more complete picture develops with intrusive camp magmatism commencing as early as 202 ma extrusive activity initiated abruptly 200 ma reaching peak volume and intensity around 199 ma on the african margin the main period of camp magmatism is confirmed as brief but is suggested to consist of at least two phases over 1 5 ma with magmatism commencing along the africa north american margins and slightly later along the south american margin two volumetrically minor but distinctive magmatic peaks centered at 195 and 192 ma are mirrored in data from all three continents and highlighted by our statistical approach models describing rifting and thermal input and magma production on these timescales are explored despite significant advances in our understanding of the chronology of camp more data of better quality and broader geographical coverage are needed to completely characterize the evolution of the camp and infer its geodynamic origin in addition lack of a well defined t j boundary age as well as the absence of a relevant basis for comparison between u pb and 40 ar 39 ar data for this time period remain limiting factors to unambiguously linking camp in time with the events of the t j boundary

valanginian weissert oceanic anoxic event biotic changes in nannofossils and radiolarians associated with the valanginian 1 3 c anomaly are documented at ocean drilling program hole 1149b in the pacific ocean they are coeval and similar to those previously documented in the tethys suggesting a global perturbation of marine ecosystems a marked increase in abundance of diazomatolithus absence of nannoconids and a pantanellium peak characterize the valanginian 1 3 c excursion such changes are interpreted as being due to global enhanced fertility and a biocalcification crisis under conditions of excess co 2 the occurrence of organic c rich black shales in the southern alps and in the pacific in the interval corresponding to the 1 3 c excursion suggests a valanginian oceanic anoxic event oae volcanism of the parana etendeka large igneous province ca 132 ma was presumably responsible for an increase of co 2 triggering a climate change and accelerated hydrological cycling possibly causing an indirect fertilization of the oceans widespread nutrification via introduction of biolimiting metals at spreading ridges could have significantly increased during the gondwana breakup and simultaneous tectonic events in three separate oceans there is no paleontological or 1 8 o evidence of warming during the valanginian oae on the contrary both nannofossils and oxygen isotopes record a cooling event at the climax of the 1 3 c excursion weathering of basalts and burial of organic c rich black shales were presumably responsible for co 2 drawdown and establishment of reversed greenhouse conditions

transient metazoan reefs in the aftermath of the end permian mass extinction microbes were thought to be the dominant reef constructors following the end permian mass extinction sponge microbe reef deposits formed in the early triassic from the western united states suggest that instead metazoan reef building continued immediately following the extinction wherever marine conditions allowed

indian ocean capacitor effect on indo western pacific climate during the summer following el nino significant climate anomalies persist through the summer june august after el nino dissipates in spring over the equatorial pacific they include the tropical indian ocean tio sea surface temperature sst warming increased tropical tropospheric temperature an anomalous anticyclone over the subtropical northwest pacific and increased mei yu baiu rainfall over east asia the cause of these lingering el nino effects during summer is investigated using observations and an atmospheric general circulation model gcm the results herein indicate that the tio warming acts like a capacitor anchoring atmospheric anomalies over the indo western pacific oceans it causes tropospheric temperature to increase by a moist adiabatic adjustment in deep convection emanating a baroclinic kelvin wave into the pacific in the northwest pacific this equatorial kelvin wave induces northeasterly surface wind anomalies and the resultant divergence in the subtropics triggers suppressed convection and the anomalous anticyclone the gcm results support this kelvin wave induced ekman divergence mechanism in response to a prescribed sst increase over the tio the model simulates the kelvin wave with low pressure on the equator as well as suppressed convection and the anomalous anticyclone over the subtropical northwest pacific an additional experiment further indicates that the north indian ocean warming is most important for the kelvin wave and northwest pacific anticyclone a result corroborated by observations these results have important implications for the predictability of indo western pacific summer climate the spatial distribution and magnitude of the tio warming rather than simply whether there is an el nino in the preceding winter affect summer climate anomalies over the indo western pacific and east asia

how and why did the lingulidae brachiopoda not only survive the end permian mass extinction but also thrive in its aftermath the end permian mass extinction devastated most of the organisms in the sea and on land however a few late permian taxa survived the mass extinction and also the subsequent early triassic post extinction catastrophic environments among them the lingulidae brachiopods were perhaps one of the most noted conquerors not only had they survived the mass extinction but also they thrived in the early triassic marine realm forming a nearly globally distributed lingulidae fauna characterized by low taxonomic diversity but high abundance of individuals the reasons that this group of brachiopods was able to achieve this remain unclear and could possibly include a number of interacting factors among them are their wide ecological adaptations and their shell composition and appearance the long term evolutionary trends in the shell microstructure and exterior of the lingulidae since the late devonian are thought to have advanced considerably by the end permian to the extent that the shells of the brachiopods were able to sustain stressful e g anoxic environments in addition a variety of short term adaptive changes in the shell size reducing shell size shape shells became more pointed and flatter anteriorly and thickness reducing shell thickness are believed to have also aided the survival of the brachiopods through the highly toxic marine environments from the latest permian to the early triassic the long term unchanged organophosphatic shell composition of lingulidae brachiopods is considered to be another key feature that must have aided the survival of this group in the end permian to the early triassic period for organophosphatic shell composition would have prevented the brachiopods from dissolution in the highly acidic marine environment prevailing globally during the permian triassic transition the ability that the lingulids had to live in a wide range of environmental conditions from high latitude to low latitude and from the shoreface to the relatively deep sea environments is also considered vital for the group to have managed to survive the catastrophic event in the latest permian and then thrive in the vacated ecological space in the ensuing early triassic disaster period 2007 elsevier b v all rights reserved

bathymetric zonation of modern microborers in dead coral substrates from new caledonia implications for paleodepth reconstructions in holocene corals abstract microboring endoliths were studied in dead modern corals collected at various depths and in growth position on la surprise atoll in new caledonia eight taxa of microborers were regularly observed three cyanobacteria hyella caespitosa mastigocoleus testarum and plectonema terebrans two chlorophytes ostreobium quekettii and phaeophila dendroides and three fungal forms dodgella priscus and two unidentified fungi the relative abundance of each taxon was determined in the modern corals throughout the studied sampling interval from 0 down to 40 m water depth this allowed us to propose for the first time a bathymetric model based on microendolith assemblages colonizing in situ hard substrates of corals in this model the occurrence of the cyanobacteria hyella and mastigocoleus indicates a bathymetric range from 0 down to a water depth of 3 and 6 m respectively the chlorophyta o quekettii associated with the cyanobacterium p terebrans and fungi is dominant from 10 to 40 m depth which is the lower limit of our sampling the distribution ranges of individual taxa observed in the dead coral substrates from new caledonia are much narrower than those reported in the literature for other substrates the bathymetric model based on distribution of microborers in modern corals was then applied to interpret the trace assemblages of microborers observed in holocene corals collected by drilling on two reef sites of new caledonia la surprise islet in the vicinity of the sampling sites of the modern corals and the barrier reef of bayes on the ne coast of grande terre the paleodepth interpretations performed at various levels along the cores allow identification of several shallowing upward sequences during the last 7000 years of reef growth in new caledonia differences in the thickness of these sequences between la surprise and bayes sites were interpreted as differences in the space available for accommodation between the two sites in turn related to the differential subsidence that affected new caledonia during holocene times the use of the microendolith trace assemblages in paleodepth reconstructions of holocene reefs from new caledonia allowed detection of relative sea level variations finer than those deduced from changes in coralgal assemblages

the end triassic mass extinction record of williston lake british columbia abstract triassic jurassic boundary sections on the shore of lake williston british columbia record a spectrum of depositional environments from the western canadian continental margin a primarily deep water anoxic record of deposition indicated by v v ni v cr th u indices and pyrite framboid and facies data is seen throughout the late triassic early jurassic norian hettangian interval in a section at black bear ridge abundant monotis bivalve populations in norian strata are interpreted to have lived on the seabed during transient oxygenation events that punctuated the background anoxic conditions monotis went extinct around the norian rhaetian boundary and the deep water assemblages are subsequently dominated by thin shelled pectinids an intra rhaetian sea level fall generated a major hiatus in the proximal black bear ridge section whilst distinctive lowstand strata were developed in the more distal and more complete ne parle pas point and pardonet creek sections these consist of shallow water phosphatic ooid sand facies that contain diverse bivalves the majority of the infaunal bivalves but not the epifaunal ones disappeared at the acme of the regression this is the end triassic mass extinction event and it occurred shortly before a terminal triassic flooding event this transgressive event is associated with a rapid negative shift of 13corg values interpreted to be the initial isotope excursion of hesselbo et al hesselbo s p robinson s a surlyk f piasecki s 2002 terrestrial and marine extinction at the triassic jurassic boundary synchronized with major carbon cycle perturbation a link to initiation of massive volcanism geology 30 251 254 the rhaetian record of williston lake thus records an extinction of shallow water infaunal bivalves during a lowstand prior to the development of a transgressive record that is associated with a major negative c isotope

palaeoenvironmental significance of carbon and oxygen isotope stratigraphy of marine triassic jurassic boundary sections in sw britain abstract carbon isotope stratigraphy is a useful tool for stratigraphic correlation especially for strata deposited during major perturbations of the carbon cycle that affected the marine terrestrial and atmospheric reservoirs for the triassic jurassic boundary effectively defined by a first order mass extinction major fluctuations in carbon isotope values have been well documented but these datasets have generally been derived from bulk rock samples hence the extent to which features of the isotopic curve reflect diagenetic alteration or changing proportions of constituent materials is unconstrained here carbon and oxygen isotope data are presented from well preserved oyster shells liostrea comprising low magnesium calcite a mineral species relatively resistant to diagenetic alteration samples were obtained from lavernock point glamorgan wales a coastal section close to a candidate stratotype for the base of the jurassic at st audrie9s bay somerset england the carbon isotope signature from st audrie9s bay previously defined on the basis of analysis of bulk organic matter is confirmed by our new data major features are 1 the upper part of an initial9 negative isotope excursion in the lowest part of the section followed by 2 a pronounced positive excursion and 3 an extended main9 negative isotope excursion in the highest part of the section the data confirm that the carbon isotope stratigraphy previously documented from bulk organic matter in sw england records the chemical composition of the contemporaneous seawater bulk carbonates sampled over the same interval near lyme regis england show similar trends to those from oyster calcite in the lower part of the study section but there are more 13 c depleted values up section these lower values probably result from an admixture of primary and diagenetic carbonate palaeotemperatures calculated from oxygen isotope values from lavernock point oyster shells are relatively cool at the beginning of the positive carbon isotope excursion and increased by up to 10 c during the main negative carbon isotope excursion the new results are compatible with the view that positive carbon isotope excursions correspond to times of low atmospheric carbon dioxide content whereas negative carbon isotope excursions correspond to times of high atmospheric carbon dioxide content as is also found to be the case during the early jurassic toarcian oceanic anoxic event the mg ca and sr ca ratios and 18 o of investigated liostrea hisingeri show no correlation supporting data from modern bivalves that indicate that incorporation of mg and sr is controlled mainly by factors other than temperature

palaeoenvironmental changes at the frasnian famennian boundary in key european sections chemostratigraphic constraints abstract the study aims to put constraints on global environmental changes which took place during the frasnian famennian f f transition by using a geochemical multiproxy approach for this several key european f f boundary sections deposited in different palaeogeographic settings were selected including in addition to the stratotype and parastratotype sections of coumiac montagne noire france and steinbruch schmidt branau germany respectively also some other sections thoroughly characterized by other authors the drilling budesheimer bach prumer mulde germany kowala section holy cross mountains poland la serre france changes in the detrital flux along the sections were evaluated on the basis of both variations in mineral composition and in some diagnostic element ratios like ti al the biogenic flux was assessed as a function of the corg content the input of nutrients or the palaeoproductivity was determined by the p2o5 and ba in excess the degree of anoxia during deposition was constrained by determining the concentration of redox sensitive metals e g fe mn in the bulk sediment of specific element ratios e g v cr as well as the size of pyrite grains together with the degree of pyritization dop in the budesheimer bach core the hydrothermal and volcanic influence in the sedimentary record was detected using e g the al al fe mn and zr al2o3 ratios the kellwasser horizons are characterized by a general decrease in the detrital input together with the increase of al normalized concentration of some of the transition metals these changes are interpreted as reflecting a relative sea level rise and a higher hydrothermal influence in contrast to these the establishment of dysoxic anoxic conditions in the depositional environment as well as the increase of organic matter burial are not always restricted to the kellwasser horizons kwh moreover the hydrothermal influence can lead to misinterpretation with respect to redox conditions and productivity due to the additional input of some specific elements our results indicate the coincidence of sea level rise with hydrothermalism and volcanism during the deposition of the kwh in the area of south laurussia and north gondwana the resulting enrichment in metals and nutrients is coupled in several f f boundary sections with a higher microbial activity as already observed by some authors these effects coupled with a general lowering of the degree of oxygenation of the water bodies could have played a significant role in the demise of the biota

the formation mechanism of the bonin high in august the bonin high is a subtropical anticyclone that is predominant near japan in the summer this anticyclone is associated with an equivalent barotropic structure often extending throughout the entire troposphere although the equivalent barotropic structure of the bonin high has been known for years among synopticians because of its importance to the summer climate in east asia there are few dynamical explanations for such a structure the present paper attempts to provide a formation mechanism for the deep ridge near japan we propose a new hypothesis that this equivalent barotropic ridge near japan is formed as a result of the propagation of stationary rossby waves along the asian jet in the upper troposphere the silk road pattern first the monthly mean climatology is examined in order to demonstrate this hypothesis it is shown that the enhanced asian jet in august is favourable for the propagation of stationary rossby waves and that the regions of descent over the eastern mediterranean sea and the aral sea act as two major wave sources second a primitive equation model is used to simulate the climatology of august the model successfully simulates the bonin high with an equivalent barotropic structure the upper tropospheric ridge is found to be enhanced by a height anomaly of more than 80 m at 200 hpa when a wave packet arrives sensitivity experiments are conducted to show that the removal of the diabatic cooling over the asian jet suppresses the silk road pattern and formation of an equivalent barotropic ridge near japan while the removal of the diabatic heating in the western pacific does not copyright 2003 royal meteorological society

tetrapod tracks in a marginal lacustrine setting middle triassic argentina taphonomy and significance abstract fossil tetrapod footprints not only provide valuable information about trackmaker paleobiology but also to give insight into details of the depositional conditions of the substrate at the time of imprinting therefore in the present study the mode of formation and taphonomy of footprints in different substrates was used to investigate the gait and walking dynamics of the trackmakers as well as a source of additional information on the environmental conditions of the track bearing beds during imprinting the analyzed section corresponds to thick middle triassic lacustrine deltaic deposits of the ischichuca los rastros formation ischigualasto villa union basin that crops out at the quebrada de ischichuca in northwestern argentina part of the track bearing surfaces correspond to the top of sandy distributary channel mouth bars in a distal delta front setting that were exposed along the lake margin during a lake level fall cross cutting relationships observed among ripple marks the footprints and invertebrate traces of a softground suite of the scoyenia ichnofacies suggest an omission surface measured trackway orientations in the sandstones are perpendicular to the paleo shoreline with the animals coming and going along the exposed top of the bars probably for drinking laterally the distal delta front deposits interfinger with track bearing wackestone beds of palustrine origin deposited in a restricted local embayment lateral to the delta influenced environment trackway orientations in the wackestones are in contrast consistent with the animals moving nearly parallel to the lake border probably along a preferred route evidences of a relative high groundwater table at the time of imprinting in the track bearing surfaces are revealed by the well developed rims of extruded sediment and collapsed digits in the studied tracks and the nearly absence of associated desiccation cracks on the same surfaces nevertheless temporary emergence cannot be ruled out when paleosoil formation was probably promoted as can be observed in the microstructure of both sandstones and wackestones moreover footprint preservation in the wackestones might have been enhanced by partial hardening of the trampled surface during subaerial exposure combining ichnofossil content and taphonomy with facies analysis we identified in the lower part of the ischichuca los rastros succession a relatively rapid withdrawal of the water basinward that was probably due to a forced regression during early rifting of basin evolution footprints can also provide valuable information about locomotion dynamics and trackmaker behavior thus the sideways deformation observed in the studied footprints attributed to basal archosaurs and putative basal dinosaurs can be related to an outward rotation of the foot during the step cycle a condition that might allied to the development of the parasagittal posture in archosauria besides the densely trampled surface described herein constitutes the first documented evidence of putative social behavior among therapsid dicynodonts the most important group of herviborous animals in the early mesozoic terrestrial ecosystems throughout gondwana

tropical extratropical teleconnections in boreal summer observed interannual variability abstractmaximum covariance analysis is performed on the fields of boreal summer tropical rainfall and northern hemisphere nh 200 hpa height for the 62 yr period of record of 1948 2009 the leading mode which appears preferentially in summers preceding the peak phases of the el nino southern oscillation enso cycle involves a circumglobal teleconnection cgt pattern in the nh extratropical 200 hpa height field observed in association with indian monsoon rainfall anomalies the second mode which tends to occur in summers following enso peak phases involves a western pacific north america wpna teleconnection pattern in the height field observed in association with western north pacific summer monsoon rainfall anomalies the cgt pattern is primarily a zonally oriented wave train along the westerly waveguide while the wpna pattern is a wave train emanating from the western pacific monsoon trough and following a great circle the cgt is accompanied by a pronounced tropical extratropical seesaw in t

a multidisciplinary study of ecosystem evolution through early pleistocene climate change from the marine arda river section italy the arda river marine succession italy is an excellent site to apply an integrated approach to paleoenvironmental reconstructions combining the results of sedimentology body fossil paleontology and ichnology to unravel the sedimentary evolution of a complex marine setting in the frame of early pleistocene climate change and tectonic activity the succession represents a subaqueous extension of a fluvial system originated during phases of advance of fan deltas affected by high density flows triggered by river floods and overlain by continental conglomerates indicating a relative sea level fall and the establishment of a continental environment an overall regressive trend is observed through the section from prodelta to delta front and intertidal settings the hydrodynamic energy and the sedimentation rate are not constant through the section but they are influenced by hyperpycnal flows whose sediments were mainly supplied by an increase in apennine uplift and erosion especially after 1 80 ma the arda section documents the same evolutionary history of coeval successions in the paleo adriatic region as well as the climatic changes of the early pleistocene the different approaches used complement quite well one another giving strength and robustness to the obtained results

sedimentology and stratigraphic architecture of the late permian betts creek beds queensland australia abstract the late permian betts creek beds form a succession of coal bearing alluvial coastal plain sediments in a basin marginal setting within the northeastern galilee basin queensland australia the unit is 50 60 m in thickness at porcupine creek national park where outcrop is laterally continuous for several kilometers eight facies have been identified within the formation and can be grouped into 2 facies associations a channel deposits and b floodbasin deposits the channel association consists of conglomerate a1 and trough cross bedded multistorey sandstone facies a2 both interpreted as deposits of low sinuosity river systems tidally influenced fluvial channels a3 interbedded sandstone and siltstone a4 interpreted as the abandonment fill of the alluvial systems and diamictite a5 interpreted as debris flows the floodbasin facies association is composed of sandy siltstone b1 proximal distal floodbasin carbonaceous siltstone b2 mire and bioturbated siltstone b3 estuarine facies the overall sediment body architecture can be resolved into 6 unconformity bounded cycles interpreted as sequences in the genetic sense which are sheet like in geometry and in general consist of amalgamated multistorey multilateral braided fluvial deposits at the base overlain by extensive sheet like overbank mudstones carbonaceous shales and coals sea level change is interpreted as the primary control on the sequence architecture of the formation while the internal stratigraphic architecture however varies between sequences and is a function of a combination of sea level tectonic and autogenic controls

phanerozoic organic carbon rich marine sediments overview and future research challenges one of the major obsessions of many early workers to the mid 1900s was the application of uniformitarian principles to deposi tional models for black shales arthur and sageman 1994 the purpose of this overview of organic carbon oc rich marinesediments is to provide a brief but current summary of the historicaldevelopments principle concepts and remaining challenges in inte grated sapropel and black shale research as such it provides asubstantive introduction to the special issue of palaeogeography palaeoclimatology palaeoecology on organic carbon rich sedimentsthrough the phanerozoic processes progress and perspectives giventhis focused scope the overview does not aim to be comprehensive orcomplete but to provide a solid setting for the fourteen individualresearch papers that constitute this special issue and two previousspecial issues meyers and negri 2003 negri et al 2006 thatcoverresearch aspects complementary to this one like the individualcontributions this introduction and overview is organized intocenozoic mesozoic and palaeozoic units the cenozoic and palaeozoicunitsaredeliberatelylargerthanthemesozoicunit acknowledgingthatmuch ground on mesozoic black shale is already covered in the twoprevious special issues because the late cenozoic sapropels of themediterraneanbasinhavebeenextensivelystudied understandinghowthese near modern analogs of ancient black shales were depositedprovidesagoodfoundationforunderstandinghowtheoldersequencesmayhaveevolved incontrast becausefarlessisgenerallyknownabouttheblackshalesofthepalaeozoicthancomparableoc richsequencesofeither the cenozoic or the mesozoic a more comprehensive summaryand comparison of the more ancient sequences is particularly appro priate to the theme of this special issue 1 introductionsediments rich in organic carbon are restricted to small areas alongcontinental margins in the modern ocean and have rarely accumulatedduringthecenozoic yetorganic rich sediments werewidely depositedduring multiple intervals of mesozoic palaeozoic time and even earlierduringtheproterozoic archean globalmarinedepositsdocumentthatepisodes of accumulation of oc rich sediments occurred in differentregions and at different times these episodes were linked to climaticandpalaeoceanographicperturbationsthat resulted inmassive uctua tions in hydrologic and nutrient cycles and in oceanchemistryand thatrecurred throughout geologic time however the paucity of survivingpalaeozoic and earlier black shale sections makes it dif cult toimpossible to recognize the internal structure of global events that arecommon inyounger oc rich sedimentary sequences asunderlinedbelow themarinesectionsinmanylocalitiesconsistof intercalated carbonates and shales that may grade into purecarbonate or black shale sedimentation often re ecting shallowing

reinterpretation of palmate and semi palmate webbed fossil tracks insights from finite element modelling abstract a track from the late cretaceous previously described as being generated by a semi palmate bird was studied with the aid of high resolution laser scanning substrate conditions at the time of track formation were diagnosed fine grained soft waterlogged sediment and used to constrain a finite element track simulator the indentation of a non webbed virtual tridactyl foot in such conditions created a resultant track with features analogous to webbing between digits this webbing was a function of sediment deformation and subsequent failure in 3d specific to rheology variation of substrate conditions and interdigital angle was incrementally stepped apparent webbing impressions were clearly developed only within a limited range of sediment conditions and pedal geometry the implications of this work are that descriptions of webbed tracks should account for the possibility that webbing was indirectly formed through sediment failure and not necessarily the direct impression of a webbed foot additionally dating the earliest occurrence of webbed feet in the fossil record and potentially extending phylogenetic ranges should be treated with caution when based upon evidence from tracks

high organic carbon content and a decrease in radiolarians at the end of the permian in a newly discovered continuous pelagic section a coincidence article i nfo the greatest mass extinction occurred at the end of the permian most records of the mass extinction are not from pelagic sediments but from shallow marine and terrestrial sediments although several pelagic sections that span the end permian mass extinction have been found these sections contain few index fossils and are often discontinuous because of small faults we found the index fossils albaillella cf triangularis radiolaria in siliceous claystone beds hindeodus parvus conodont in the overlying black claystone beds and neospathodus cf cristagalli and ns waageni conodont in the subsequent siliceous claystone beds in akkamori section 2 in northern japan these fossils suggest that this section ranges from the late permian to the early triassic including the early induan and olenekian stages furthermore the lithological changes in the section i e starting from bedded chert through siliceous claystone and black claystone to siliceous claystone are concordant with those of well known permian triassic pelagic sequences in japan there is no gap between each lithofacie of the akkamori section 2 critical lithological continuity between upper permian siliceous claystone beds and uppermost permian to lowermost triassic black claystone beds of the akkamori section 2 was recognized by observing hand polished specimens and thin sections such paleontological and sedimentological evidence implies that the akkamori section 2 is a continuous pelagic section that records the end permian mass extinction event the carbonaceous black claystone beds have high total organic carbon toc concentrations 1 06 3 31 wt suggesting oceanic anoxia at least deep and probably stable primary productivity a decrease in radiolarian abundance from 26 563 to 0 27 20 specimens cm 2 coincided with an increase in toc content from 0 01 0 16 to 1 06 3 31 wt at the boundary of the siliceous claystone and the overlying black claystone beds near the top of the permian implying that radiolarian extinction occurred at the end of the permian coinciding with oceanic anoxia although toc contents decreased in the early olenekian smithian radiolarian abundance did not increase at that time indicating that radiolarian recovery was delayed by n1 5 m y

mass extinctions and sea level changes abstract review of sea level changes during the big five mass extinctions and several lesser extinction events reveals that the majority coincide with large eustatic inflexions the degree of certainty with which these eustatic oscillations are known varies considerably thus the late ordovician and end cretaceous extinctions are associated with unequivocal major regressions demonstrated from numerous widespread regions in contrast the multiple high frequency sea level changes reported for the frasnian famennian crisis based on the supposed depth preferences of conodont taxa have little support from sequence stratigraphic analyses which reveals the interval to be one of highstand the end permian mass extinction has long been related to a severe first order lowstand of sea level newell n d 1967 revolutions in the history of life geol soc am spec pap 89 63 91 based primarily on the widespread absence of latest permian ammonoid markers but field evidence reveals that the interval coincides with a major transgression newell s hypothesis that marine extinctions are related to shelf habitat loss during severe regression remains tenable for the end guadalupian and end triassic extinction events but not for other crises rapid high amplitude regressive transgressive couplets are the most frequently observed eustatic changes at times of mass extinction with the majority of extinctions occurring during the transgressive pulse when anoxic bottom waters often became extensive the ultimate cause of the sea level changes is generally unclear a glacioeustatic driving mechanism can only be convincingly demonstrated for the end ordovician and end devonian events at other times it is speculated that they may relate to the widespread regional doming and subsequent collapse caused by the impingement of superplumes and ultimate eruption on the base of the lithosphere

structure and dynamics of the summertime pacific japan teleconnection pattern convective activity over the tropical western pacific is known to influence the extratropical circulation over east asia in the boreal summer in the form of teleconnection called the pacific japan pj pattern but its structure and dynamics have not yet been studied in depth in this study a composite analysis is performed for 32 monthly events of enhanced convection observed to the east of the philippines the composited monthly mean vorticity anomalies associated with the pj pattern are elongated zonally with a distinct poleward tilt with height this structure differs fundamentally from a combination of the first baroclinic mode in the tropics and the barotropic structure in midlatitudes as has widely been accepted as a conceptual model of the pj pattern a wave activity flux points polewards only in the lower troposphere indicating that rossby wave teleconnection occurs primarily through a low level south westerly jet those tilted anomalies over the western pacific can effectively gain kinetic energy in the exits of the mean jet streams in the upper and lower troposphere and available potential energy ape in the presence of the vertically sheared jets the enhanced convection can generate ape effectively and the associated low level anomalous circulation acts to increase moisture supply into the convective region while enhancing evaporation from the pre warmed ocean surface it is thus hypothesized that the pj pattern may be regarded as a dynamical mode that can be effectively excited in the zonally asymmetric baroclinic mean flow associated with the asian summer monsoon with an efficient self sustaining mechanism through moist processes copyright 2006 royal meteorological society

skeletal carbonate productivity and phosphogenesis at the lower middle cambrian transition of scania southern sweden the lower middle cambrian transitional interval of scania is largely represented by condensed limestone beds lithostratigraphically grouped in the gislov formation 1 5 7 m thick and the forsemolla and exsulans limestone beds lower part of the alum shale formation up to 4 in thick the strata display a combination of skeletal carbonate productivity episodic nucleation of phosphate hardground nodules and polyphase reworking recorded on a platform bordering the nw corner of baltica the shell accumulations can be subdivided into three deepening upward parasequences separated by distinct erosive unconformities the parasequences correspond biostratigraphically to the holmia kjerulfi ornamentaspis linnarssoni and ptlychagnostus gibbus zones the latter two generally being separated by a stratigraphic gap that includes the middle cambrian acadoparadoxides oelandicus superzone except for the exsulans limestone the carbonates reflect development of a prolific epibenthic biota dominated by filter feeding nonreefal chancelloriid echinoderm sponge meadows rich in trilobites and brachiopods and which were subjected to high energy conditions the absence of microbial mats or veneers encrusting the erosive surfaces of these event concentration low relief shoal complexes may be related to long hiatal episodes resulting in microboring proliferation high levels of nutrient supply resulted in high primary productivity eutrophic conditions glauconite precipitation phosphogenesis in some case microbially mediated and rnicroendolithic infestation an early diagenetic mildly reducing environment is suggested by the presence of authigenic subsequently reworked pyrite which contrasts with the syndepositional normal oxygenated conditions reflected by macroburrowing and the abundance of benthic fossils

a revised sedimentary and biostratigraphical architecture for the type llandovery area central wales the global standard for the llandovery series early silurian in central wales is re assessed in the light of detailed geological surveying biostratigraphical sampling and a rigorous examination of published datasets a new sedimentary and biostratigraphical architecture is presented key graptolite brachiopod acritarch and for the first time chitinozoan assemblages are critically assessed upper hirnantian to aeronian strata record events that followed the late ordovician glacial maximum and comprise a series of progradational sequences bounded by flooding surfaces but inferred still to be glacioeustatic in origin significant faunal renewals associated with many of the flooding levels underpin their potential for international recognition compound non sequences are a feature of proximal parts of the system where erosion associated with fault footwall uplift was an important process extensive slump sheets contribute to further stratal loss and displacement in distal facies a re assessment of the aeronian stage gssp reveals shortcomings with the biostratigraphical criteria used in its selection telychian portions of the succession display the disrupting effects of intra wenlock synsedimentary sliding hence the relevance of key published fossil assemblages and the criteria used to erect the stage gssp are undermined however the llandovery area remains one of the best studied early silurian successions in the world this together with regional considerations supports the retention of the series standard in mid wales where the contiguous deep water basinal succession affords internationally cited exposure of richly graptolitic facies for the whole series and significantly for the post sedgwickii biozone interval

response of the marine infauna to triassic jurassic environmental change ichnological data from southern england abstract the trace fossil record through the triassic jurassic boundary interval is examined at three sites in central and southern england st audrie s bay somerset pinhay bay devon and long itchington warwickshire the lower pre planorbis beds of the blue lias formation record low ichnotaxonomic diversity low bioturbation intensity small burrow diameters and an absence of deep tier bioturbation the stepwise reappearance of ichnotaxa following this interval is similar at the three sites suggesting similar rates of recovery in the benthic marine ecosystem and highlighting the potential contribution of these trace fossils to stratigraphic correlation mass extinction in the late triassic is increasingly linked to the emplacement of the central atlantic magmatic province camp timing of the onset of camp volcanism in the uk is currently imperfectly known but potentially occurred within either the westbury formation or the lilstock formation if the onset of camp was within the lilstock formation the modestly diverse trace fossil assemblage of the langport member of the lilstock formation suggests that emplacement of camp had little lasting effect on the marine benthos in central and southern england the decline in benthic activity recorded in the pre planorbis beds appears to be unrelated to the onset of camp and any associated environmental change it is more likely related to an episode of marine anoxia an episode of marine anoxia also provides a suitable causal mechanism for the reduction of infaunal tiering

co2 and the end triassic mass extinction the end of the triassic period was marked by one of the largest and most enigmatic mass extinction events in earth s history1 and with few reliable marine geochemical records terrestrial sediments offer an important means of deciphering environmental changes at this time tanner et al 2 describe an isotopic study of mesozoic fossil soils which suggests that the atmospheric concentration of carbon dioxide pco2 across the triassic jurassic boundary was relatively constant within 250 p p m v but this is inconsistent with high resolution evidence from the stomatal characters of fossil leaves3 here i show that the temporal resolution of the fossil soil samples may have been inadequate for detecting a transient rise in pco2 i also show that the fossil soil data are consistent with a large increase in pco2 across the triassic jurassic boundary when variations in the stable carbon isotope denoted as 13c in terrestrial plant leaves are taken into account these factors suggest that the linkage between pco2 global warming and the end triassic mass extinction remains intact

widespread delayed mixing in early to middle cambrian marine shelfal settings abstract the radiation of burrowing metazoans in the early phanerozoic dramatically altered the properties of marine sediment an event commonly referred to as the cambrian substrate revolution or agronomic revolution the advent of infaunalization and especially biogenically mediated sediment mixing profoundly impacted the development of phanerozoic biogeochemical cycling including nutrient fluxes organic carbon burial seafloor oxygenation and sediment ecology however the timing of the development of mixed seafloor sediment has historically not been well constrained mixing has been assumed in the absence of data to occur at the precambrian cambrian boundary with the appearance of the index fossil and three dimensional burrow treptichnus pedum herein we present new ichnological stratigraphic and taphonomic data suggesting that although significant developments in infaunalization paleobiologically complex animal substrate interactions particularly burrow construction occurred during the early and middle cambrian mixing remained suppressed throughout this interval we demonstrate using a novel multi proxy approach that shelfal sediment in the earliest cambrian was essentially unmixed moreover our findings indicate that even as late as the middle cambrian 30 million years after the precambrian cambrian transition and well after the appearance of supposedly deposit feeding trilobites seafloor heterolithic shelfal sediment remained largely unmixed on a global scale these findings challenge the current assumption that mixing occurred with the first appearance of three dimensional burrows and hold important implications for the advent and development of modern style biogeochemical cycling

bryozoans in transition the depauperate and patchy jurassic biota bryozoans were profoundly affected by the end permian and probably also by the end triassic mass extinction events their recovery in terms of diversity and disparity during the jurassic was slow and geographically patchy critical compilation of data from the published literature reveals only 172 valid species 160 cyclostomes 10 ctenostomes and 2 cheilostomes some as yet not formally named however the rate of description of new jurassic bryozoan species during the last two hundred years implies that many more species remain to be discovered and described the jurassic is the only geological period during which cyclostomes were the dominant order and is also important in having the oldest cheilostome bryozoan the first representative of the order that dominates the modern bryozoan biota species diversity peaked in the bathonian where local assemblages may contain up to 33 species encrusters account for 124 73 of the 172 jurassic species among which small sheet like forms especially those assigned to the form genus berenicea are the most numerous the overwhelming predominance in the jurassic of weeds with runner ribbon or sheet colony forms is striking unlike the triassic and cretaceous large tree like or frondose erect colonies are uncommon and species with fenestrate articulated and free living colonies are unknown of 92 geographically categorized entries for jurassic bryozoans in the zoological record 1937 2003 80 87 are european records outside europe diversity appears to have remained low throughout the jurassic and non weedy species are particularly scarce compared with the cretaceous jurassic bryozoans show no adaptations that can be interpreted as related to the increased predation pressure associated with the mesozoic marine revolution the jurassic bryozoan biota shares characteristics with both the stenolaemate dominated palaeozoic triassic biota and the cheilostome dominated cretaceous recent biotas

triassic jurassic organic carbon isotope stratigraphy of key sections in the western tethys realm austria the late triassic period is recognized as one of the five major mass extinctions in the fossil record all these important intervals in earth history are associated with excursions in c isotope records thought to have been caused by perturbations in the global carbon cycle the nature and causes of c isotopic events across the triassic jurassic t j transition however are poorly understood we present several new high resolution organic c isotope records from the eiberg basin austria including the proposed global boundary stratotype section and point gssp for the base of the jurassic the triassic jurassic boundary interval in these records is characterized by the initial and main negative organic carbon isotope excursions cie of up to 8 the initial and main cies are biostratigraphically constrained by first and last occurrences of boundary defining macro and microfossils e g ammonites high resolution c isotope records appear to be an excellent correlation proxy for this period in the eiberg basin pyrolysis analysis demonstrates increased hydrogen index hi values for organic matter coinciding with the initial cie terrestrial organic matter influx and mass occurrences of green algae remains may have influenced the c isotope composition of the sedimentary organic matter this may have contributed to the extreme amplitude of the initial cie in the eiberg basin

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

wetland sedimentation and associated diatoms in the pleistocene olorgesailie basin southern kenya rift valley abstract the olorgesailie basin in the southern kenya rift valley contains a variety of lacustrine wetland and terrestrial facies that were laid down during the last 1 2 million years this study integrates diatom ichnofossil and rhizolith silica and carbonate evidence in order to identify and characterize shallow wetland deposition at the top member 14 ca 493 ka of the olorgesailie formation a key feature of these deposits is the presence of facies with aquatic indicators diatoms that are overprinted by ichnofossils and rhizoliths that suggest drier conditions diatom floras include several fresh water aulacoseira spp and saline indicators such as thalassiosira rudolfi t faurii cyclotella meneghiniana and anomoeoneis sphaerophora the main indicators of shallow fresh to mildly saline waters include epithemia argus rhopalodia gibberula encyonema muelleri and synedra spp three main suites of ichnofossils indicate varying water table depths during their formation these consist of 1 horizontal tunnels that suggest saturated substrates 2 vertical burrows formed in substrates with relatively lower water tables and 3 termite hymenopteran and beetle ichnofossils that indicate dry substrates member 14 of the olorgesailie formation also contains carbonate and siliceous rhizoliths which occur both together and separately four possible models are suggested to explain the silica and carbonate rhizolith formation 1 a complex of spring fed marshes and dry areas 2 ephemeral wetlands and floodplains 3 wetlands with abundant organic decay and 4 initial carbonate rhizoliths that were replaced by silica preservation of cellular structures and the reworking and incorporation of rhizoliths in overlying younger strata suggest that they formed early during diagenesis

barotropic wave propagation and instability and atmospheric teleconnection patterns abstract a global barotropic model linearized about the 300 mb climatological mean january flow is perturbed by applying a series of localized forcings distributed throughout the tropics and subtropics structures which resemble the observed pacific north american and east atlantic teleconnection patterns noted by wallace and gutzler 1981 tend to recur in the responses similar patterns are found to result from the dispersion of isolated initial perturbations placed at a variety of locations in the tropics and midlatitudes it is shown that these structures are related to the most rapidly growing mode associated with barotropic instability of the zonally varying climatological basic state in the absence of damping this mode has an e folding time of about a week and a period close to 50 days in localized regions the instantaneous growth rates can be competitive with those of baroclinic instability these episodes of rapid local barotropic growth are interspersed with intervals in which the local

global extratropical response to diabatic heating variability of the asian summer monsoon abstract global teleconnections associated with the asian summer monsoon convective activities are investigated based on monthly data of 29 northern hemisphere summers defined as june september jjas two distinct teleconnection patterns are identified that are associated respectively with variabilities of the indian summer monsoon and the western north pacific summer monsoon the indian summer monsoon convective activity is associated with a global pattern that has a far reaching connection in both hemispheres whereas the western north pacific summer monsoon convective activity is connected to a southern hemisphere wave train that influences the high latitude south pacific and south america a global primitive equation model is utilized to assess the cause of the global circulation anomalies the model responses to anomalous heatings of both monsoon systems match the general features of the observed circulation anomalies well and they are mainly controlled by linear processes the response patterns ar

stratigraphy and palaeoenvironmental analysis of the triassic jurassic transition in the western southern alps northern italy abstract high resolution stratigraphic studies were carried out on the rhaetian hettangian succession of the bergamasc alps western southern alps italy in order to characterise the stratigraphic and palaeoenvironmental evolution of the lombardian succession across the triassic jurassic t j boundary the t j boundary in the bergamasc alps is sandwiched between the rhaetian carbonate ramp succession of the zu limestone formation and the malanotte formation a new lithostratigraphic unit introduced in this paper deposited during relative sea level rise in the earliest hettangian the zu limestone is organised into subtidal mixed shale carbonate asymmetric cycles documenting the regional evolution from a distal to a proximal depositional environment of an articulated homoclinal carbonate ramp the malanotte formation lacks cyclicity and shows thin bedding and a dominant micritic facies documenting the subtidal evolution of a relatively homogenous outer carbonate ramp environment the microfloral associations record a gradual evolutionary change at the t j boundary whereas the biocalcifying communities appear to be severely affected by the end triassic biotic crisis

palaeoecological patterns within the dysaerobic biofacies examples from devonian black shales of new york state abstract two distinct body fossil distribution patterns are recognized within devonian dysaerobic strata of the appalachian basin 1 taxa that are adapted to the lowest bottom water oxygen conditions and 2 taxa that are adapted to fully oxygenated conditions with distinct ranges of tolerance to low oxygen conditions the latter group taxa demonstrate a nested pattern of distribution in association with relative bottom water oxygen levels as a result rather than discrete unique taxonomic assemblages within the dysaerobic biofacies the successive loss of species in a predictable order in association with decreasing oxygen serves to delineate relative bottom water oxygen levels throughout the range of dysaerobic conditions rhynchonelliform brachiopods of the super family camarotoechioidea are overwhelmingly dominant but species within this clade are ecologically variable valve size of eumetabolotoechia multicostata with a broad range of oxygen tolerance varies in association with relative oxygen levels further variation in life habit distribution is recognized through the dysaerobic zone epifaunal filter feeders dominate under extremely reduced oxygen levels and specific oxygen thresholds are recognized by the addition and or dominance of specific life habits this nested pattern of taxonomic distribution through the dysaerobic zone is unexpected based on observations in modern and other post palaeozoic low oxygen communities and is likely associated with frequent and pervasive periods of dysoxia in shallow epeiric seaways

complex palaeosol ichnofabrics from late jurassic early cretaceous volcaniclastic successions of central patagonia argentina abstract late jurassic early cretaceous volcaniclastic continental deposits from central patagonia argentina were analyzed for an integral characterization of palaeosol ichnofabrics these units contain complex continental ichnofabrics that were also recorded in other late jurassic late miocene extended volcaniclastic successions from patagonia according to a recently proposed method ichnofabric pedofabric and original bedding of selected intervals were measured separately in order to determinate the degree in which the deposits are affected by soil features besides the ichnofabrics four recurrent ichnofabrics were recognized in studied palaeosols the loloichnus large taenidium beaconites diffuse boxwork and dagnichnus ichnofabrics the loloichnus ichnofabric is characterized by sub vertical loloichnus baqueroensis and subordinate similarly arrenged large taenidium barretti and beaconites coronus l baqueroensis is a crayfish dwelling structure while large t barretti and b coronus are assigned to locomotion of the same organisms root traces are additional components of this ichnofabric the large taenidium beaconites ichnofabric is formed by large irregular and curved t barretti and b coronus and by l baqueroensis in low proportion this ichnofabric is also assigned to crayfish activity the diffuse boxwork ichnofabric is characterized by a pervasive and intricate three dimensional boxwork of burrows occasionally joined to subspherical chambers possible castrichnus the diffuse boxwork is interpreted as an earthworm burrow system and the associated chambers are probably for aestivation rare and scattered discrete trace fossils in this ichnofabric include l baqueroensis t barretti and b coronus the dagnichnus ichnofabric is formed by dagnichnus titoi root traces and subordinately loloichnus baqueroensis cellicalichnus meniscatus and tangled groups of meniscate burrows d titoi and c meniscatus has been interpreted as crayfish breeding structures and the tangled groups of meniscate burrows are probably related to juvenile crayfish activity the studied ichnofabrics were formed in weakly to moderately developed palaeosols in lowland areas with frequent reworking of pyroclastic material by unconfined flows the recognized ichnofabrics show that in patagonia for the late jurassic early cretaceous times crayfishes and earthworms were the dominant soil organisms and along with plants rapidly colonized deposits exposed subaerially after sediment deposition and with high soil moisture content or high water table crayfishes probably crawled in moist sediments forming the large taenidium beaconites ichnofabric with a better drained soil profile or lower water tables the loloichnus ichnofabric representing the dwelling structures of adult crayfishes overprinted the previous ichnofabric the diffuse boxwork ichnofabric usually located in the uppermost portion of palaeosols correspond to extensive fossil earthworm burrow systems the dagnichnus ichnofabric occurs in very weakly developed palaeosols and probably reflects the optimal palaeoenvironmental conditions for breeding crayfish

bivalve trace fossils in an early miocene discontinuity surface in patagonia argentina burrowing behavior and implications for ichnotaxonomy at the firmground hardground divide abstract ichnofossils developed in a firmground at the contact between the middle eocene lower miocene continental sarmiento formation and the lower miocene marine chenque formation in central eastern patagonia argentina are assigned to gastrochaenolites ornatus kelly and bromley kelly s r a bromley r g 1984 ichnological nomenclature of clavate borings palaeontology 27 793 807 and interpreted as dwelling structures of suspension feeding bivalves these record the activities of pholadids most likely belonging to the pholadinae bivalves are usually preserved as casts and external molds within the biogenic structures the details of the internal ornamentation in g ornatus allow identification of two sets of scratch patterns permitting comparison with the boring behavior of modern pholadids in terms of ichnotaxonomy when the same organism is able both to excavate and to bore and the excavation technique is identical to the mechanical perforation technique the same name should be used accordingly gastrochaenolites whilst more commonly assigned to bioerosion structures in hard substrates is herein regarded as available also for bivalve burrows in firm but unlithified substrates the firmground studied here represents a co planar surface of lowstand erosion and transgressive erosion that produced exhumation of deposits belonging to the sarmiento formation providing appropriate conditions for the development of the glossifungites ichnofacies differential erosion of the apertural necks the heterogeneity of the available casting material and the wide size range of ichnofossils suggest a complex history of colonization and erosion for this surface

role of subtropical precipitation anomalies in maintaining the summertime meridional teleconnection over the western north pacific and east asia abstract the meridional teleconnection patterns over the western north pacific and east asia wnp ea during summer have a predominant role in affecting east asian climate on the interannual time scale a well known seesaw pattern of tropical subtropical precipitation is associated with the meridional teleconnection and the subtropical precipitation anomaly has been previously viewed as a result of anomalous circulations associated with the teleconnection in this study however the authors suggest that subtropical precipitation anomalies in turn can significantly affect large scale circulations and may be crucial for maintenance of the meridional teleconnection diagnosis by using observational and reanalysis data indicates that the meridional teleconnection patterns are clearer in summers when the subtropical rainfall anomalies are greater the simulated results by a linear baroclinic model indicate that a subtropical heat source which is equivalent to the diagnosed positive subtropical precipitati

marine bioerosion in rocks of the prehistoric tholos of la pastora valencina de la concepcion seville spain archaeological and palaeoenvironmental implications in this study we examined the materials used in the building of the tholos of la pastora located in the archaeological site of valencina de la concepcion seville spain which represents the largest settlement of the guadalquivir valley during the third millennium bc three different types of rock were found palaeozoic sandstone shale which forms the walls of both the corridor and the chamber palaeozoic granite which makes up part of the roof slabs and neogene calcareous sandstone which forms the remainder of the roof and floor slabs as well as the jambs lintels and some blocks of the walls of the chamber intense marine bioerosion as a result of the activity of bivalves annelids and sponges was observed in some elements of the calcareous sandstone in fact the remains of some of the tracemakers were unusually well preserved as was the case for the bivalve petricola lithophaga whose shells remain in many of their burrows we infer that these bioerosion structures were formed in a shallow coastal environment intertidal and that bioerosion was possible until the few moments before its extraction as construction material thereby the environment in which rock extraction took place was likely a coastal wave cut platform in which calcareous sandstone levels outcropped and stood out between clay layers the radiocarbon dates obtained from these bivalve shells provide a time range between 4780 and 4400 cal yr bp 2830 2450 yr bc as the highest probability for rock extraction and the subsequent building of the tholos thus the date represents a terminus post quem for the construction of the monument of la pastora

contrasting origins of early cretaceous black shales in the vocontian basin evidence from palynological and calcareous nannofossil records abstract detailed records of spore pollen assemblages particulate organic matter om dinoflagellate cysts and calcareous nannofossils provide new insights into the palaeoclimatic and palaeoceanographic conditions during formation of early cretaceous black shales in the vocontian basin southeastern france the early aptian niveau goguel which corresponds to the oae1a and the regionally distributed late aptian niveau jacob have been studied with regard to changes in terrestrial vegetation patterns terrigenous inputs and palaeofertility conditions palynological results from both black shale intervals exhibit a rich and stable floral pattern dominated by various ferns different types of cycads bennettites as well as by several conifer families dinoflagellate cyst assemblages and the calcareous nannofossil based nutrient index show no prominent changes in surface water productivity across the two studied intervals in the vocontian basin significant variations are observed in terrestrial detrital input indicated by changes in absolute abundances of marine and terrestrial palynomorphs according to our results the laminated om rich horizons of the niveau goguel interval reflect deposition during times of reduced siliciclastic input episodes of pronounced condensation were accompanied by anoxic conditions preventing degradation of the predominantly marine derived om in contrast the niveau jacob is characterised by a strong increase in terrestrial palynomorphs most probably reflecting an abrupt increase in riverine runoff the enhanced terrestrial om input may have triggered oxygen depletion in bottom waters resulting in turn in increased om preservation our results highlight the variety of processes that controlled the accumulation of om in the vocontian basin and they illustrate that enhanced surface water productivity is not an indispensable prerequisite for the formation of mid cretaceous black shales

joining forces combined biological and geochemical proxies reveal a complex but refined high resolution palaeo oxygen history in devonian epeiric seas abstract two devonian black shale intervals were analysed using a carefully integrated palaeontological geochemical approach to interpret relative bottom water oxygen levels at a resolution and sensitivity possible only through the combined approach biological data presented as both trace and body fossil abundance and size suggest generally low bottom water oxygen conditions the frequently laminated sediments would be viewed traditionally as recording appreciable intervals of anoxic and or euxinic anoxic and h 2 s containing bottom waters the inclusion of parallel geochemical results however refines this perspective well established iron proxies for depositional redox tell us that anoxic and euxinic conditions were intermittent and short lived if present at all manganese and molybdenum data point to conditions with a likelihood of very low oxygen in bottom waters during intervals with high pore water concentrations of hydrogen sulphide near the sediment water interface these elevated sulphide concentrations under iron limited diagenetic conditions varied with organic content and may have further inhibited benthic colonization and an active infaunal community more specifically the combined palaeontological and geochemical data sets point to depleted bottom water oxygen contents with evidence for hydrogen sulphide limited dominantly or exclusively to the pore waters anoxia and euxinia if present occurred only intermittently and lasted only briefly perhaps on seasonal time scales tied to primary productivity cycles or climatically induced variation in water column stratification the time scales and mechanisms of rapid redox variation remain to be studied the details of such transitional and dynamic settings are best viewed from a multi proxy biogeochemical and palaeoecological perspective as an important byproduct geochemical methods refined in multi proxy studies of phanerozoic shales can then be extended with greater utility to precambrian strata without trace and body fossils

carbon isotope anomaly and other geochemical changes at the triassic jurassic boundary from a marine section in hungary most mass extinctions are linked with carbon isotope excursions implying that biotic crises are coupled with changes in the global carbon cycle the isotopic evolution during the end triassic extinction is far less documented than that for the other major phanerozoic extinctions here we report a sharp and short lived 23 5 excursion in carbon isotope values for carbonate d 13 ccarb corresponding to a 22 excursion in the isotopic composition of marine organic matter d 13 corg and other geochemical

survival of burgess shale type animals in a middle ordovician deep water setting exceptional preservation of non biomineralized arthropods sponges and vermiform taxa occurs in the darriwilian middle ordovician llanfallteg formation of south wales uk the assemblage contains elements typical of ordovician communities juxtaposed with those more commonly associated with cambrian konservat lagerstatten this assemblage is preserved in rocks of a deep marine succession dominated by fine grained siliciclastic and volcaniclastic density current deposits non biomineralized taxa of cambrian aspect are preserved as pyritized carbonaceous compressions on the spectrum of burgess shale type preservation trilobites with phosphatized digestive structures have also been recovered the assemblage of the llanfallteg formation konservat lagerstatte demonstrates that some burgess shale type faunal elements survived into the middle ordovician within cool deep water refugia in the welsh basin offshore from communities dominated by typical ordovician taxa supplementary material assemblage composition data and sedimentological images can be found at https doi org 10 6084 m9 figshare c 2182218

paleoceanographic and paleoclimatic similarities between mediterranean sapropels and cretaceous black shales pliocene quaternary sapropels of the mediterranean sea and mid cretaceous black shales share many distinctive properties organic carbon concentrations that often exceed 5 in both types of sequences record episodes of exceptional accumulation of organic matter although both are rich in marine organic matter they have high c n ratios that mimic those of land plant organic matter which suggests less efficient organic matter recycling than in the modern ocean the coupled presence of isorenieratene derivatives and low 15n values that result from microbial primary productivity indicates that photic zone anoxia existed during their formation and implies strong stratification of the surface ocean enrichments of redox sensitive metals and sediment laminations indicate that anoxia existed deeper in the water column and at the seafloor multiple proxies indicate freshening of surface waters of the mediterranean and imply periods of wetter climate during times of sapropel deposition episodes of black shale deposition similarly coincide with times of wetter climate these comparisons suggest that the wetter climate created similar conditions of surface salinity stratification that enhanced microbial primary production and magnified organic matter export during deposition of both the mediterranean sapropels and mid cretaceous black shales

trace fossils of the arthropod camptophyllia from the westphalian carboniferous rocks of lancashire uk and their palaeoenvironmental context abstract two arthropod trace fossils are described and analysed from the carboniferous lower westphalian c communis and basal a modiolaris chronozones coal bearing strata of lancashire the biserial trackway diplichnites triassicus consists of five overlapping en echelon sets of 7 9 tracks preserved as epichnia and hypichnia in lacustrine siltstones the trackway suggests subaqueous in phase walking by a multi segmented producer with a body length of 35 40 mm width 17 22 mm and 7 9 appendages curved clustered or laterally repeated hypichnial lobes with transverse striations on the base of ripple cross laminated sandstone are identified as rusophycus versans this trace fossil is interpreted as shallow resting or furrowing burrows of a homopodous arthropod 30 60 mm long 15 30 mm wide and probably the same kind of arthropod as produced d triassicus a review of contemporary arthropod body fossils from lagerstatten in lancashire favours the onisciform or arthropleura like arthropod camptophyllia as a potential producer of both of these trace fossils in a lacustrine palaeoenvironment this study integrates the analysis of sediments trace fossils and body fossils for reconstructing the arthropod biota and ecology in westphalian lacustrine and crevasse splay fluvial palaeoenvironments

late permian to middle triassic correlations and palaeogeographical reconstructions in south western european basins new sedimentological data from minorca balearic islands spain description of sedimentary sections and interpretations of sequence stratigraphic evolution of permian triassic red beds of minorca allow a new proposal of palaeoenvironment reconstructions the permian sediments mainly correspond to floodplain and pond deposits with sheetflood sand bed rivers environment de 1 within a warm and semi arid climate and the preserved succession forms one complete stratigraphic cycle the retrogradational phase of this cycle is represented by alluvial colluvial deposits grading upwards to environment de 1 and to extensive floodplain and pond deposits the progradational phase is characterized by increasing fluvial influence with palaeocurrent mainly oriented to the sw palaeosol horizons and preservation of a late permian palynoflora the uppermost part of this succession is truncated by a major erosional surface the sediments above this unconformity are characterized by braided river deposits environment de 2 with palaeocurrent oriented to the ssw within the more basal conglomeratic facies and to the wnw in overlying units the absence of extensive floodplain deposits a paucity of evidence for biogenic activity and palaeosols together with the presence of ventifacts indicate an arid climatic setting for the succession this environment evolved from braided rivers palaeocurrents mainly oriented to the se environment de 3 with in situ palaeosols and reworked breccias to fluvial coastal and shallow marine deposits environment de 4 dated as upper anisian to ladinian this succession characterizes a retrogradational trend although the transition between de 2 and de 3 was not observed a switch in palaeocurrent directions may indicate a change in source area a comparison at a regional scale with other peri tethyan basins allows the succession to be placed within a broader palaeoenvironmental and stratigraphic context during late permian to middle triassic during the late permian sedimentation occurred in alluvial playa lake or ponded environments where fluvial systems generally flowed southward except in south eastern france oriented to the ne within these sw european basins such as minorca the late permian succession shows a major retrogradational evolution from fluvial or alluvial fan deposits to extensive lake playa or floodplain deposits and a progradational trend fluvial or alluvial fan deposits the permian triassic transition corresponds to an unconformity overlain by braided river deposits with arid climate indicators aeolian deposits ventifacts and aeolian dune sedimentation at the scale of western europe this arid episode is dated as smithian and the induan age sedimentation deposits seem to be preserved only in the central part of the germanic basin as with all other peri tethyan basins environment de 2 of minorca above the major erosional surface is attributed to the smithian in the upper part of the studied succession braided river deposits indicative of less arid climatic conditions are preserved this succession contains the earliest mesozoic palaeosols dated as anisian by palynomorphs and expresses a vertical evolution from fluvial to open marine depositional environments attributed to the muschelkalk transgression

an extended organic carbon isotope record across the triassic jurassic boundary in the queen charlotte islands british columbia canada abstract new lithologic and organic carbon isotope data are presented for the triassic jurassic boundary section at kennecott point queen charlotte islands british columbia canada the previously reported late norian to earliest hettangian record is extended by over 130 m and three new isotopic features are revealed the record now shows a negative offset in baseline carbon isotope values from approximately 29 in the late norian to 31 in the hettangian this offset is accompanied by the previously reported 2 negative excursion at the triassic jurassic boundary and a 5 positive excursion in the early hettangian there is a significant long term negative isotopic trend in the hettangian interval of the section which may be due to camp volcanism the positive excursion is attributed to a decline in bio calcification as well as changes in microbial ecology both related to the mass extinction at the triassic jurassic boundary

temperature controlled deposition of early cretaceous barremian early aptian black shales in an epicontinental sea abstract a continuous 103m thick mudstone sequence of barremian early aptian age recently exposed in northern germany has been logged and analyzed with respect to its macrofaunal content and its geochemistry 13c 18o based on common belemnite and rarer ammonite findings a detailed biozonation has been established covering the complete barremian early aptian interval including the mid early aptian fischschiefer the deposition of which occurred during oceanic anoxic event 1a quite common throughout the sequence are finely laminated black shales blatterton with high toc contents of up to 7 these laminated black shales with caco3 contents of up to 60 are interbedded with dark and carbonate poor clays on the scale of decimeters to several meters oxygen depletion of bottom waters is indicated for the laminated intervals since these are barren of any benthic fossils a salinity driven stratification of the water column during more humid periods was caused by a more intense run off from the nearby hinterland this and increased surface water productivity are seen as a possible cause for the lamination with observations being mainly based on micropalaeontological evidence dinoflagellates calcispheres calcareous nannofossils stable isotope studies 13c 18o performed on belemnite guards show 13c values of 0 to 2 for the barremian a distinctive positive excursion of 4 directly above the early aptian fischschiefer correlates well with the global positive 13c excursion of mid early aptian age following the oceanic anoxic event 1a this first record of the 13c positive excursion from the boreal realm therefore confirms the global nature of the signal a shift in 18o values of about 2 in the late barremian early aptian is interpreted as a temperature decrease by 8 c this cooling goes along with a shift from the thick up to 6 5m early barremian hauptblatterton to thin 10cm to 20cm laminites blatterton in the late barremian during the deposition of the hauptblatterton very warm conditions caused a long lasting 500kyrs stable water stratification the cooler temperatures of the late barremian reduced the stability of the water stratification resulting in rather short termed alternations of thin laminites and dark clays these observations suggest a temperature controlled peak of anoxic conditions in the early barremian hauptblatterton and subsequently short termed changes from anoxic to suboxic conditions in the late barremian and early aptian

reply to comment on the organic carbon isotopic and paleontological record across the triassic jurassic boundary at the candidate gssp section at ferguson hill muller canyon nevada usa by ward et al 2007

contrasting relationship between tropical western north pacific convection and rainfall over east asia during indian ocean warm and cold summers abstractusing daily data this study compares the subseasonal seesaw relationship between anomalous tropical western north pacific wnp convection and anomalous rainfall over subtropical east asia during boreal summers june august in which the indian ocean io sea surface temperature is either warmer or colder than normal it is found that the precipitation anomalies over central eastern china 25 35 n 110 120 e associated with the anomalous tropical wnp convection activities during the io cold summers are weaker and less evident compared to that in the io warm summers indicating the seesaw relationship in the io cold summers becomes obscure this contrasting seesaw relationship between the io warm and cold summers is attributed to different patterns of anomalous moisture transportation and vertical motion over central eastern china the anomalous circulations associated with the anomalous tropical wnp convection the pacific japan pj pattern during the io warm and cold summers show that rela

genesis of the south asian high and its impact on the asian summer monsoon onset abstractthe formation of the south asian high sah in spring and its impacts on the asian summer monsoon onset are studied using daily 40 yr ecmwf re analysis era 40 data together with a climate mean composite technique and potential vorticity diabatic heating pv q analysis results demonstrate that about 2 weeks before the asian summer monsoon onset a burst of convection over the southern philippines produces a negative vorticity source to its north the sah in the upper troposphere over the south china sea is then generated as an atmospheric response to this negative vorticity forcing with the streamline field manifesting a gill type pattern afterward the persistent rainfall over the northern indochinese peninsula causes the sah to move westward toward the peninsula consequently a trumpet shaped flow field is formed to its southwest resulting in divergence pumping and atmospheric ascent just over the southeastern bay of bengal bob near the surface as a surface anticyclone is formed over t

late pliensbachian early toarcian early jurassic environmental changes in an epicontinental basin of nw europe causses area central france a micropaleontological and geochemical approach abstract we present an integrated work based on calcareous nannofossil and benthic foraminiferal assemblages and geochemical analyses of two upper pliensbachian lower toarcian sections located in the central south france the studied sections tournadous and saint paul des fonts represent the proximal and the distal part respectively of the jurassic causses basin one of the small partly enclosed basins belonging to the epicontinental shelf of the nw tethys at the transition from late pliensbachian to early toarcian the causses basin recorded an emersion in response to the global sea level fall our data indicate severe environmental conditions of marine waters including salinity decrease and anoxia development occurring in the early toarcian the acme of this deterioration coincides with the early toarcian anoxic event t oae but due to the restricted nature of the basin anoxia persisted until the end of the early toarcian mainly in the deeper parts of the basin the micronutrients and organic organic matter fluxes were probably high during the entire studied time interval as shown by nannofossil and foraminiferal assemblages however nannoplankton production drastically decreased during the t oae as demonstrated by very low nannofossil fluxes and only taxa tolerant to low saline surface waters could thrive at the same time benthic foraminifers temporarily disappeared in response to sea bottom anoxia our study demonstrates that environmental changes related to the t oae are well recorded even in small partly enclosed basins of nw europe like the causses basin within this area the effects of global changes like sea sea level and temperature fluctuations are modulated by local conditions mainly controlled by the morphology of the basin

high resolution ammonite and carbon isotope stratigraphy across the triassic jurassic boundary at new york canyon nevada the triassic jurassic boundary is generally considered as one of the major extinctions in the history of phanerozoic the high resolution ammonite correlations and carbon isotope marine record in the new york canyon area allow to distinguish two negative carbon excursions across this boundary with different paleoenvironmental meanings the late rhaetian negative excursion is related to the extinction and regressive phase the early hettangian 13corg negative excursion is associated with a major floristic turnover and major ammonite and radiolarian radiation the end triassic extinction early jurassic recovery is fully compatible with a volcanism triggered crisis probably related to the central atlantic magmatic province the main environmental stress might have been generated by repeated release of so2 gas heavy metals emissions darkening and subsequent cooling this phase was followed by a major long term co2 accumulation during the early hettangian with development of nutrient rich marine waters favouring the recovery of productivity and deposition of black shales

mechanisms of meridional teleconnection observed between a summer monsoon system and a subtropical anticyclone part i the pacific japan pattern abstract summertime atmospheric circulation over the midlatitude western north pacific wnp is influenced by anomalous convective activity near the philippines this meridional teleconnection observed in monthly anomalies and known as the pacific japan pj pattern is characterized by zonally elongated cyclonic and anticyclonic anomalies around the enhanced convection center and to its northeast respectively in the lower troposphere with an apparent poleward phase tilt with height the authors idealized two layer linear model whose basic state consists of a zonal subtropical jet and a pair of a monsoon system and a subtropical anticyclone can simulate a pj like response against diabatic heating located between the pair each of the observed and simulated patterns can gain energy through barotropic and baroclinic conversions from the zonally varying baroclinic mean flow in an efficiency comparable with that of energy generation due to the anomalous diabatic heating indicating a characteristic of

how to measure the strength of the east asian summer monsoon defining the intensity of the east asian summer monsoon easm has been extremely controversial this paper elaborates on the meanings of 25 existing easm indices in terms of two observed major modes of interannual variation in the precipitation and circulation anomalies for the 1979 2006 period the existing indices can be classified into five categories the east west thermal contrast north south thermal contrast shear vorticity of zonal winds southwesterly monsoon and south china sea monsoon the last four types of indices reflect various aspects of the leading mode of interannual variability of the easm rainfall and circulations which correspond to the decaying el nino while the first category reflects the second mode that corresponds to the developing el nino the authors recommend that the easm strength can be represented by the principal component of the leading mode of the interannual variability which provides a unified index for the majority of the existing indices this new index is extremely robust captures a large portion 50 of the total variance of the precipitation and three dimensional circulation and has unique advantages over all the existing indices the authors also recommend a simple index the reversed wang and fan index which is nearly identical to the leading principal component of the easm and greatly facilitates real time monitoring the proposed index highlights the significance of the mei yu baiu changma rainfall in gauging the strength of the easm the mei yu which is produced in the primary rain bearing system the east asian ea subtropical front better represents the variability of the easm circulation system this new index reverses the traditional chinese meaning of a strong easm which corresponds to a deficient mei yu that is associated with an abnormal northward extension of southerly over northern china the new definition is consistent with the meaning used in other monsoon regions worldwide where abundant rainfall within the major local rain bearing monsoon system is considered to be a strong monsoon

ichnological analysis the common ground between ichnofacies workers and ichnofabric analysts abstract this work compares the approaches taken by the two schools of applied ichnology ichnofacies and ichnofabric analysts and proposes an integrated approach for future improvement there are many similarities between the two approaches which mainly differ in the resolution at which ichnological analysis is undertaken ichnofabric work is by necessity performed on a bed by bed basis and interpreted at a scale consistent with that of the sedimentologist s facies ichnofacies studies in contrast seldom report bed by bed changes in ichnological content instead highlighting bedset to facies association scale changes in ichnology through comparison with summary models of ichnological trends this work highlights the fact that workers from both schools utilize the same tools with slightly different emphases to reach their ichnological conclusions contention between the two schools has in recent years centred upon which is the better method for studying trace fossils an artificial construct that detracts from the fact that both are extremely useful to sedimentological and palaeoenvironmental studies ichnofabric analysis is in addition a highly effective means of documenting bioturbated sedimentary fabrics as the basis for petrophysical studies ichnofacies and ichnofabric analysts use the same toolbox of ichnological methods to determine ancient palaeoenvironments the scale of observation is generally different but the results closely comparable the recognition of key stratal surfaces on ichnological grounds is also possible with both methodologies ichnofacies analysts look to recognise glossifungites ichnofacies firmgrounds in offshore mudstones ichnofabric studies would look to recognise overprinting of fabrics created by groups of organisms from different palaeoenvironments but associated with the same key surface it is proposed that the terms ichnofacies method and ichnofabric analysis are abandoned in favour of a neutral ichnological analysis method encompassing the approaches and terminology of both to produce a unified scientifically rigorous user friendly methodology

the application of ichnology to palaeoenvironmental and stratigraphic analysis it has been increasingly realized by sedimentologists in the petroleum industry and academia that integration of ichnological information into sedimentological models and vice versa is one of the main means by which we can improve our understanding of ancient depositional environments this volume aims to provide an analytical review of the ichnology of all major depositional environments and the use of ichnology in biostratigraphic and sequence stratigraphic analysis as well as highly refined palaeoenvironmental studies the remit of the book is achieved through a combination of review articles and novel research papers that outline methodologies and protocols for improving our understanding of ancient palaeoenvironments trace fossils from microscopic borings to dinosaur footprints are considered the comprehensive coverage of ancient depositional environments means that the book will be of use as a course text for undergraduates as well as an invaluable reference text for all students of ichnology whether they are ichnologists sedimentologists or petroleum geologists by trade

carbon cycle perturbation and stabilization in the wake of the triassic jurassic boundary mass extinction event 1 the triassic jurassic boundary mass extinction event t j 199 6 ma is associated with major perturbations in the carbon cycle recorded in stable carbon isotopes two rapid negative isotope excursions in bulk organic carbon 13corg occur within the immediate boundary interval at multiple locations and have been linked to the outgassing of 12c enriched co2 from the central atlantic magmatic province in british columbia a positive 13corg excursion of 5 vienna peedee belemnite v pdb spans part or all of the subsequent hettangian stage here we examine the significance of these carbon isotope excursions as records of global carbon cycle dynamics across the t j boundary and test the link between carbon cycle perturbation stabilization and biotic extinction recovery patterns a combination of 13corg and palynological analyses from the late triassic to early jurassic in the mingolsheim core germany suggests that organic carbon isotope variations are best explained as the result of both compositional changes in terrestrial versus marine input and disturbance and recovery patterns of major terrestrial plant groups across the t j boundary a new high resolution 13ccarb record from the val adrara section in the southern alps italy spanning from the uppermost rhaetian through lower sinemurian does not exhibit a negative excursion at the t j boundary but does record a large positive 13ccarb excursion of 4 v pdb in bulk carbonate that begins at the t j boundary and reaches a local maximum at the early late hettangian boundary values then gradually decrease reaching 0 5 at the hettangian sinemurian boundary and remain relatively constant into the early sinemurian complementary 13ccarb data from 4 more sections that span the hettangian sinemurian boundary support carbon cycle stabilization within the upper hettangian our analyses suggest that isotope changes in organic carbon reservoirs do not necessarily require a shift in the global exogenic carbon reservoir and that the positive excursion in the carbonate carbon isotope record is best explained as the combined result of an increase in atmospheric pco2 leading to accelerated carbon cycling decreased skeletal carbonate production and increased organic carbon burial lasting several hundred thousand years the termination of the positive inorganic carbon isotope excursion coincides with the recovery of marine skeletal carbonate producers and coeval changes in terrestrial vegetation and reflects the gradual reduction in pco2 and the stabilization of the global carbon cycle during the sinemurian

carbon isotope stratigraphy and palynostratigraphy of the triassic jurassic transition in the tiefengraben section northern calcareous alps austria abstract the end triassic is characterized by enhanced rates of biotic turnover in both the marine and terrestrial realms carbon isotope anomalies have been reported worldwide that may indicate coeval global disturbances in the biogeochemical cycles here we present the results of an integrated study of the palynomorph assemblages and the carbon isotope composition of organic matter in the tiefengraben section near st wolfgang austria carbon isotope values from bulk organic matter show significant fluctuations through the triassic jurassic t j boundary interval with two prominent negative 13 c org excursions an initial negative carbon isotope excursion occurs at the base of the kendlbach formation tiefengraben member pre planorbis beds although triassic ammonoids and conodonts have their highest occurrence at the top of the underlying kossen formation the palynomorph and calcareous microfossil assemblages indicate still a rhaetian age for the lower part of the tiefengraben member high abundance of prasinophytes during the interval of the initial carbon isotope excursion may represent a bloom of green algae that flourished as a result of the disturbance of the marine ecosystems increased spore abundance together with the disappearance of distinctive late triassic pollen types e g ovalipollis rhaetipollis indicate vegetation changes on land that are contemporaneous with the marine biotic crisis a second negative carbon isotope excursion occurs in the middle part of the tiefengraben member based on palynological evidence the t j boundary may be drawn at about this level by the lowest occurrence of cerebropollenites thiergartii the established carbon isotope curve as well as palynostratigraphic and other biostratigraphic events can be correlated with st audrie s bay england

changing oligocene climate recorded by palynomorphs from two glacio eustatic sedimentary cycles cape roberts project victoria land basin antarctica abstract two marine palynomorph assemblages recovered from two glacio eustatic sedimentary cycles from the cape roberts project crp which recovered over 1500 m of oligocene and miocene strata from the western margin of the victoria land basin are investigated we present results from one cycle dated as early oligocene and the other dated as late oligocene modest numbers of marine palynomorphs were recovered with an average abundance of 56 specimens per gram the assemblages recovered from both cycles are broadly similar and dominated by acritarchs and the phycoma of prasinophyte algae these include leiosphaeridia sp 2 leiosphaeridia sp 3 and the prasinophyte alga cymatiosphaera sp 2 in detail however the lower oligocene assemblage is different from that of the upper oligocene the lower oligocene cycle includes impagidinium cf dispertium and impagidinium cf elegans cymatiosphaera sp 6 and pyxidinopsis sp are abundant the upper oligocene cycle is characterized by an absence of cymatiosphaera invaganata cymatiosphaera sp 8 and pterospermella sp a it has very low numbers of acritarch sp b impagidinium and pyxidinopsis it contains tasmanites sp and brigantedinium pynei and it has higher abundances of lejeunecysta sp 1 and sigmopollis than the lower oligocene cycle the environmental interpretations of the crp core from other workers using sedimentological and paleontological indicators are used to infer environmental conditions that are likely to have influenced the marine palynomorph assemblages paleontological and sedimentological analysis suggests that both cycles were deposited in cold conditions with sea ice and melt water influence although the upper oligocene assemblage is inferred to have existed in colder marine conditions with more prolonged sea ice cover and less associated fresh water input than the assemblage of early oligocene times the application of modern analogues for some of the marine palynomorph taxa identified suggest the presence of sea ice and occasionally lowered salinity in both cycles this is broadly consistent with the findings of the other paleoenvironmental studies on the crp cores

climate change driven black shale deposition during the end triassic in the western tethys abstract several new triassic jurassic boundary sections from the eiberg basin northern calcareous alps austria have been studied at high resolution we present integrated geochemical and biological proxy data from this western tethys shelf basin high resolution correlation of kuhjoch the global boundary stratotype section and point gssp for the base of the jurassic hochalplgraben and tiefengraben shows that the initial and main carbon isotope excursions cie are contemporaneous with first and last occurrences of boundary defining macro and microfossils we focus on the end triassic initial cie at the transition from the limestones of the kossen formation to the marls of the kendlbach formation this change coincides with a dramatically increased influx of conifer cheirolepidiaceae pollen and increased total organic carbon toc values succeeded by an acme of green algae cymatiosphaera we present a model in which increased terrestrial organic matter influx is related to enhanced seasonality and increased erosion of the hinterland reduced salinity of the surface waters led to the mass occurrence of green algae stratification of the water column may have caused anoxic bottom water conditions and black shale deposition during the initial cie at the base of the kendlbach fm