extraction of potential energy from geostrophic fronts by inertial symmetric instabilities abstractsubmesoscale oceanic density fronts are structures in geostrophic and hydrostatic balance which are prone to inertial and or symmetric instabilities we argue in this article that drainage of potential energy from the geostrophic flow is a significant source of their growth we illustrate our point with two dimensional boussinesq numerical simulations of oceanic density fronts on the f plane a set of two dimensional initial conditions covers the submesoscale portion of a three dimensional parameter space consisting of the richardson and rossby numbers and a measure of stratification or latitude because we let the lateral density gradient decay with depth the parameter space map is nontrivial excluding low rossby low richardson combinations dissipation and the presence of boundaries select a growing mode of inertial symmetric instability consisting of flow cells that disturb isopycnal contours systematically these isopycnal displacements correspond to a drainage of potential energy from th

postapocalyptic greenhouse paleoclimate revealed by earliest triassic paleosols in the sydney basin australia the permian triassic boundary in the sydney basin of australia is coincident with a pronounced decrease in 13 c isotopic values of organic carbon the last coals anywhere in the world for all of the early triassic ca 6 m y time and extirpation of the glossopteris flora at the top of the illawarra and newcastle coal measures coal bearing paleosols of the latest permian represent extensive swamplands of the seasonally deciduous glossopteris flora in a humid cold temperate lowland southwest of an andean style volcanic arc stone rolls large ribs of floor rock up into the coal within some of the uppermost coals of the permian coal measures can be interpreted as string bogs of a kind now found in cold climates at latitudes of 68 70 which is compatible with a paleomagnetically estimated paleolatitude of 65 85 s for the sydney basin paleolatitude was not much different for earliest triassic time but paleosols of that age include inceptisols and entisols showing substantial chemical and textural weathering more like soils now forming at latitudes of 40 58 than those within polar circles this anomalous high latitude warmth set in at the permian triassic boundary sedimentation rates increased at the boundary marked by geochemically unusual acidification of clay and a dramatic carbon isotopic excursion these changes in environments and ecosystems can be explained by soil erosion following deforestation implied by the plant extinctions and abundant fungal remains at the permian triassic boundary evidence from paleosols can now be added to that from paleontological and isotopic studies showing that disruption of the carbon cycle at the permian triassic boundary resulted in a co 2 or ch 4 post apocalyptic greenhouse paleoclimate

enhanced turbulence and energy dissipation at ocean fronts the ocean surface boundary layer mediates air sea exchange in the classical paradigm and in current climate models its turbulence is driven by atmospheric forcing observations at a 1 kilometer wide front within the kuroshio current indicate that the rate of energy dissipation within the boundary layer is enhanced by one to two orders of magnitude suggesting that the front rather than the atmospheric forcing supplied the energy for the turbulence the data quantitatively support the hypothesis that winds aligned with the frontal velocity catalyzed a release of energy from the front to the turbulence the resulting boundary layer is stratified in contrast to the classically well mixed layer these effects will be strongest at the intense fronts found in the kuroshio current the gulf stream and the antarctic circumpolar current all of which are key players in the climate system

permian and triassic greenhouse crises paleoclimatic time series from permian and triassic paleosols reveal transient episodes of unusually warm and wet conditions interrupting long periods of cool and dry conditions usual for calcareous red paleosols some of these paleoclimatic events are known from stomatal index of fossil lepidopteris leaves to have been episodes of elevated global atmospheric co2 the magnitude of 19 known permian and triassic greenhouse crises varied considerably and they offer new evidence for the relationship between paleoclimate and atmospheric co2 levels these greenhouse crises also had marked effects on global lowland vegetation introducing frost sensitive tropical lycopsids to high latitudes and drought tolerant conifers to low latitude lowlands greenhouse events punctuate phases in plant evolution ottokaria callipteris plumsteadia rufloria lidgettonia tatarina pleuromeia and dicroidium scytophyllum floras greenhouse events also punctuate the evolution of reptilian dynasties successive pelycosaur dinocephalian dicynodont rhynchosaur and dinosaur faunas and respiratory adaptations such as enlarged bony secondary palate greenhouse crises of the late and middle permian were the most severe known and suggest a role for atmospheric pollution with ch4 and co2 in those mass extinction events probably from thermogenic cracking of coals by intrusive feeder dikes of flood basalts because of formalities in boundary definition these mass extinctions are neither end permian nor end guadalupian but upper changhsingian and mid capitanian respectively

paleocene sea level and productivity changes at the southern tethyan margin el kef tunisia integrated analysis of quantitative distribution patterns of organic walled dinoflagellate cysts dinocysts and benthic foraminifera from the paleocene el kef section nw tunisia allows the reconstruction of sea level and productivity fluctuations our records indicate that the environment evolved from an initially oligotrophic open marine outer neritic to upper bathyal setting towards a more eutrophic inner neritic setting influenced by coastal upwelling by the end of the paleocene an overall second order change in paleodepth is reflected by both microfossil groups from the base of planktic foraminifera zone p4 onwards the main phase of shallowing is evidenced by an increase of inner neritic dinocysts of the areoligera group disappearance of deeper water benthic foraminifera and increasing dominance of shallow marine taxa several buliminids haplophragmoides spp trochammina spp the total magnitude of this shallowing is obscured by interaction with a signal of eutrophication but estimated to be around 150 m from 200 to 50 m superimposed on the overall trend third order sea level fluctuations have been identified and correlated to sequences in other regions paleoproductivity indicators notably protoperidinioid dinocysts and buliminids show a trend from an oligotrophic to a eutrophic setting d 2005 elsevier b v all rights reserved

multiple early triassic greenhouse crises impeded recovery from late permian mass extinction the late permian mass extinction was not only the most catastrophic known loss of biodiversity but was followed by unusually prolonged recovery through the early triassic opinion has been divided on whether delayed recovery was a legacy of especially profound ecological disruption or due to additional environmental perturbations new records from the sydney basin in southeastern australia now reveal five successive late permian and early triassic spikes of unusually high atmospheric co2 and profound chemical weathering these successive atmospheric co2 greenhouse crises coincided with unusually warm and wet paleoclimates for a paleolatitude of 61 s successive transient greenhouse crises punctuated long term cool dry and low co2 conditions and may account for the persistence of low diversity and small size in early triassic plants and animals

direct observations of microscale turbulence and thermohaline structure in the kuroshio front 1 direct observations of microstructure near the kuroshio front were conducted in august 2008 and october 2009 these show negative potential vorticity pv in the mixed layer south of the front where directly measured turbulent kinetic energy dissipation rates are an order magnitude larger than predicted by wind scaling these elevated dissipation rates scale better with an empirical scaling which considers local wind and ekman buoyancy flux driven by downfront wind near zero pv in the thermocline under the kuroshio mainstream is observed at 200 300 m depth with dissipation exceeding open ocean thermocline values by factors of 10 100 overall the large turbulent dissipation rates measured in the kuroshio can be categorized into two groups one characterized by low richardson number along the kuroshio front thermocline and the other characterized by high stratification away from the kuroshio mainstream the former is attributed to mixing by unbalanced frontal ageostrophic flows and the latter is attributed to internal wave breaking on average both groups appear in regions of large horizontal density gradients observed thermohaline structure shows low salinity tongues from the surface to over 300 m depth and deep cold tongues extending upward from 500 to 100 m depth in a narrow 20 km zone suggesting down and upwelling driven by geostrophic straining which is confirmed by quasigeostrophic omega equation solutions this implies that adiabatic along isopycnal subduction and diabatic diapycnal turbulent mixing acting in tandem at the kuroshio front likely contribute to npiw formation

coeval eocene blooms of the freshwater fern azolla in and around arctic and nordic seas abstract for a short time interval c 1 2 myr during the early middle eocene 49 myr the central arctic ocean was episodically densely covered by the freshwater fern azolla implying sustained freshening of surface waters coeval azolla fossils in neighboring nordic seas were thought to have been sourced from the arctic the recognition of a different azolla species in the north sea raised doubts about this hypothesis here we show that no less than five azolla species had coeval blooms and spread in the arctic and nw european regions a likely trigger for these unexpected azolla blooms is high precipitation prevailing by the end of the warmest climates of the early eocene climatic optimum eeco

evidence of enhanced turbulent dissipation in the frontogenetic kuroshio front thermocline 1 enhanced turbulent dissipation o 10 8 10 7 wkg 1 in the thermocline on the cyclonic side of the kuroshio front was observed during a period of frontogenesis using a microstructure profiler xbt and adcp along 143 e across the kuroshio front in august 2008 the eddy diffusivity corresponding to the mixing below the central jet is estimated to be o 10 4 10 3 m2 s 1 the strong turbulent mixing we observed in the kuroshio is in sharp contrast to previous field measurements which found that small scale diapycnal mixing in western boundary currents remains at levels typically measured in the open ocean thermocline the turbulence in the kuroshio is attributed to frontogenesis arising out of an estimated confluence rate of o 10 5 s 1 based on satellite altimeters suggesting the ubiquity of a forward energy cascade from mesoscale to microscale turbulence near ocean fronts as indicated by recent theoretical studies

putative dicynodont coprolites from the upper triassic of poland abstract a significant number more than 100 of brown to dark and silty carbonate or pyrite mineralized in part organic carbon rich spherical or oval shaped structures have been collected from the upper triassic uppermost norian lower rhaetian sediments of the lipie l skie clay pit at lisowice near lubliniec town poland their geological context morphology content geochemistry and association with skeletal remains suggest they are fecal masses of a sizable herbivorous tetrapod the only large herbivore known from the site is a giant 5 meter long dicynodont synapsida anomodontia represented by numerous bones and also by large oval shaped footprints the putative dicynodont coprolites were collected from mudstone and siltstone with numerous organic remains that were deposited in anoxic conditions in addition rees and other trace element concentrations suggest that the burial environment and diagenesis of these coprolites were under anoxic conditions sem and thin section images of the coprolite matrix show numerous nests with pyrite probably bacterial in origin and large amount of mineral particles the putative dicynodont coprolites contain also amorphous dark organic matter poorly preserved palynomorphs small fragments of plant cuticle detailed characteristic of these coprolites reveals possible implications for the ecology and physiology of the source animal species the 13 c values of the gymnosperm cuticle and dark organic matter measured in three coprolites are 23 4 21 2 and 20 3 all average the evidence from these coprolites suggests that dicynodonts processed plant soft elements into very small pieces but wood fragments were found also in a mass accumulation in two coprolites

intensification of ocean fronts by down front winds abstract many ocean fronts experience strong local atmospheric forcing by down front winds that is winds blowing in the direction of the frontal jet an analytic theory and nonhydrostatic numerical simulations are used to demonstrate the mechanism by which down front winds lead to frontogenesis when a wind blows down a front cross front advection of density by ekman flow results in a destabilizing wind driven buoyancy flux wdbf equal to the product of the ekman transport with the surface lateral buoyancy gradient destabilization of the water column results in convection that is localized to the front and that has a buoyancy flux that is scaled by the wdbf mixing of buoyancy by convection and ekman pumping suction resulting from the cross front contrast in vertical vorticity of the frontal jet drive frontogenetic ageostrophic secondary circulations ascs for mixed layers with negative potential vorticity the most frontogenetic ascs select a preferred cross front width and do not translate with

global coal gap between permian triassic extinction and middle triassic recovery of peat forming plants early triassic coals are unknown and middle triassic coals are rare and thin the early triassic coal gap began with extinction of peat forming plants at the end of the permian ca 250 ma with no coal known anywhere until middle triassic 243 ma permian levels of plant diversity and peat thickness were not recovered until late triassic 230 ma tectonic and climatic explanations for the coal gap fail because deposits of fluctuating sea levels and sedimentary facies and paleosols commonly found in coal bearing sequences are present also in early triassic rocks nor do we favor explanations involving evolutionary advances in the effectiveness of fungal decomposers insects or tetrapod herbivores which became cosmopolitan and much reduced in diversity across the permian triassic boundary instead we favor explanations involving extinction of peat forming plants at the permian triassic boundary followed by a hiatus of some 10 m y until newly evolved peat forming plants developed tolerance to the acidic dysaerobic conditions of wetlands this view is compatible not only with the paleobotanical record of extinction of swamp plants but also with indications of a terminal permian productivity crash from delta sup 13 c sub org and total organic carbon of both nonmarine and shallow marine shales 205 refs 3 figs more 3 tabs less

heterogeneous rare earth element ree patterns and concentrations in a fossil bone implications for the use of ree in vertebrate taphonomy and fossilization history abstract a bone fragment cgdq 3 of falcarius utahensis a therizinosaur from the early cretaceous cedar mountain formation utah contained within a carbonate nodule was analyzed by laser ablation inductively coupled plasma mass spectrometry la icp ms in order to investigate ree variability within a thin walled phalanx previous studies have found depth related ree pattern variations however in cgdq 3 variation occurs along the circumference of the bone nasc normalized ree patterns and concentrations vary between two apparent end members a light ree enriched lree pattern similar to solution icp ms analysis of this bone characterizes approximately two thirds of the bone fragment total ree concentrations are high and do not vary significantly from the periosteal surface to the medullar surface conversely the remaining one third of the bone has ree patterns that are mree depleted and low in total ree concentrations ree concentrations in this part of the bone do not vary significantly from the periosteal to the medullar surface a positive ce anomaly is found throughout the entire bone and is greatest within the lree enriched portion of the bone this in combination with the lree enrichment suggests that the bone fossilized under reducing conditions the distance between the lree enriched and mree depleted regions is less than 1 mm isotopic and petrographic analyses of the bone and surrounding carbonate matrix suggest the ree patterns in the bone were the result of partial fossilization incomplete filling of micro pore spaces around bone crystallites in an environment with changing redox conditions the lower mree depleted part of the bone fossilized contemporaneously with a pendant cement that formed on the underside of the bone in the vadose zone formation of the pendant cement restricted water flow through the bone isolating the lower portion which incorporated a mree depleted pattern the upper part of the bone lree enriched side fossilized under more reducing conditions than the lower part this resulted in reductive dissolution of minerals such as hydrous ferric oxides and manganese oxides which were lree enriched with positive ce anomalies these ree were then incorporated into the upper part of the bone this likely occurred after the bone entered the saturated zone below the water table the thinness of the bone and presence of a pendant cement helped facilitate partial fossilization of the bone preserving the ree signature of an earlier fluid as demonstrated by this case study differences in ree patterns within a fossil may record changes in geochemical conditions during fossilization particularly when bones are encased in a material that reduces fluid permeability such as micritic vadose calcite analysis of such bones may offer the opportunity to decipher complex fluid histories that occur during fossilization la icp ms should be utilized to confirm solution icp ms analysis if it yields high ree variability prior to an interpretation of reworking or time averaging

towards quantitative environmental reconstructions from ancient non analogue microfossil assemblages ecological preferences of paleocene eocene dinoflagellates abstract we explore a novel approach towards quantification of paleo ecological signals from non analogue microfossil assemblages by quantifying relations between assemblages and high quality geochemical and sedimentological data from sedimentary archives we test this approach using one group of microfossils the organic cysts of dinoflagellates dinocysts which are widely used in shelf and open marine settings for biostratigraphy and reconstructions of past environments and environmental change similar to other microfossil groups dinocysts can be used to reconstruct environments with relatively high confidence for recent time periods as species affinities can be derived from observational and instrumental data in the absence of such data the ecology of extinct species is much less certain and as a result reconstructions in deep time are often limited to qualitative interpretations to explore if quantitative empirical relations between extinct dinocysts and high quality geochemical data can be established we study a major event of climate change the paleocene eocene thermal maximum petm 56 ma ago the petm is a particularly suitable period for this exercise as there is a multitude of large environmental perturbations associated with the transient global warming such as deoxygenation sea level rise and an accelerated hydrological cycle the synthesized published dataset exhibits better spatial and temporal coverage compared to any other period in deep time we extract empirical relations for the abundance of previously proposed paleoecological groups as a function of independent environmental proxies for example sea surface temperature and terrestrial organic matter input the results unequivocally illustrate that many dinocysts show relations to several of the reconstructed environmental variables notably we show that one genus apectodinium and an ecogroup epicystal goniodomidae required sea surface temperatures in excess of 20 c and 25 c respectively while one species florentinia reichartii was only abundant between 30 and 35 c other groups apparently favored either a limited spiniferites or high senegalinium terrestrial input to the study site relating to salinity nutrient levels or suspended sediment load i e murkiness crucially our work shows that the validation and quantification of ecological signals by independent environmental proxy data provides the opportunity to extract more quantitative information from a wide range of non analogue microfossil assemblages while this approach is not limited to any specific group of microfossils or macrofossils we stress that proper calibration datasets high quality sedimentological and geochemical proxy records are needed and should ideally have decent geographical coverage and include one or more environmental perturbations using this approach such empirical relations can be established for a wide range of microfossil groups that have highly complementary geological records which increases the value of existing data and ensures future application of microfossil based paleoecology

rapid and sustained surface ocean acidification during the paleocene eocene thermal maximum the paleocene eocene thermal maximum petm has been associated with the release of several thousands of petagrams of carbon pg c as methane and or carbon dioxide into the ocean atmosphere system within 10 kyr on the basis of the co occurrence of a carbon isotope excursion cie widespread dissolution of deep sea carbonates and global warming in theory this rapid carbon release should have severely acidified the surface ocean though no geochemical evidence has yet been presented using boron based proxies for surface ocean carbonate chemistry we present the first observational evidence for a drop in the ph of surface and thermocline seawater during the petm planktic foraminifers from a drill site in the north pacific ocean drilling program site 1209 show a 0 8 decrease in boron isotopic composition 11b at the onset of the event along with a 30 40 reduction in shell b ca similar trends in 11b are present in two lower resolution records from the south atlantic and equatorial pacific these observations are consistent with significant global acidification of the surface ocean lasting at least 70 kyr and requiring sustained carbon release the anomalies in the b records are consistent with an initial surface ph drop of 0 3 units at the upper range of model based estimates of acidification

a novel proxy for terrestrial organic matter in sediments based on branched and isoprenoid tetraether lipids we propose a novel tracer for terrestrial organic carbon in sediments based on the analysis of tetraether lipids using high performance liquid chromatography mass spectrometry hplc ms analysis of terrestrial soil and peats shows that branched tetraether lipids are predominant in terrestrial environments in contrast to crenarchaeol the characteristic membrane lipid of non thermophilic crenarchaeota which is especially abundant in the marine and lacustrine environment based on these findings an index was developed the so called branched and isoprenoid tetraether bit index based on the relative abundance of terrestrially derived tetraether lipids versus crenarchaeol this bit index was applied to surface sediments from the angola basin where it was shown to trace the outflow of the congo river furthermore analyses of particulate organic matter from the north sea showed relatively higher bit indices in water column particulate organic matter near large river inputs a survey of globally distributed marine and lacustrine surface sediments shows that the bit index in these environments correlates with the relative fluvial input of terrestrial organic material making this index generally applicable the new proxy allows the rapid assessment of the fluvial input of terrestrial organic material in immature sediments up to 100 ma old

eustatic variations during the paleocene eocene greenhouse world we reconstruct eustatic variations during the latest paleocene and earliest eocene 58 52 ma dinoflagellate cysts grain size fractions and organic biomarkers in marine sections at four sites from three continents indicate an increased distance to the coast during the paleocene eocene thermal maximum petm the same trend is recognized in published records from other sites around the world together the data indicate a eustatic rise during the petm beginning 20 to 200 ka before the globally recorded negative carbon isotope excursion cie at 55 5 ma although correlations are tentative we recognize other global transgressions during chrons c25n and c24n the latter may be associated with eocene thermal maximum 2 53 5 ma or the x event 52 ma these results suggest a link between global sea level and hyperthermal intervals potentially because of the melting of small alpine ice sheets on antarctica thermal expansion of seawater or both however the early onset of sea level rise relative to the cie of the petm suggests contributions from other mechanisms perhaps decreasing ocean basin volume on sea level rise copyright 2008 by the american geophysical union

reconstruction of sea surface conditions at middle to high latitudes of the northern hemisphere during the last glacial maximum lgm based on dinoflagellate cyst assemblages abstract a new calibration database of census counts of organic walled dinoflagellate cyst dinocyst assemblages has been developed from the analyses of surface sediment samples collected at middle to high latitudes of the northern hemisphere after standardisation of taxonomy and laboratory procedures the database comprises 940 reference data points from the north atlantic arctic and north pacific oceans and their adjacent seas including the mediterranean sea as well as epicontinental environments such as the estuary and gulf of st lawrence the bering sea and the hudson bay the relative abundance of taxa was analysed to describe the distribution of assemblages the best analogue technique was used for the reconstruction of last glacial maximum lgm sea surface temperature and salinity during summer and winter in addition to sea ice cover extent at sites from the north atlantic n 63 mediterranean sea n 1 and eastern north pacific n 1 three of the north atlantic cores from the continental margin of eastern canada revealed a barren lgm interval probably because of quasi permanent sea ice six other cores from the greenland and norwegian seas were excluded from the compilation because of too sparse assemblages and poor analogue situation at the remaining sites n 54 relatively close modern analogues were found for most lgm samples which allowed reconstructions the new lgm results are consistent with previous reconstructions based on dinocyst data which show much cooler conditions than at present along the continental margins of canada and europe but sharp gradients of increasing temperature offshore the results also suggest low salinity and larger than present contrasts in seasonal temperatures with colder winters and more extensive sea ice cover whereas relatively warm conditions may have prevailed offshore in summer from these data we hypothesise low thermal inertia in a shallow and low density surface water layer

rare earth element systematics of fossil bone revealed by la icpms analysis intra bone rare earth element ree fractionation trends were studied by la icpms analysis to put constraints on 1 the mechanisms controlling ree fractionation within fossil bones 2 the relative timing of ree uptake in various parts of fossil bone and 3 the origin of ree in fossil bones we have evaluated ree bone profiles across 54 fossil bones from a broad range of well characterised taphonomic settings ranging in age from triassic to early medieval ree patterns and concentration gradients are highly variable and intra bone fractionation trends in la yb n vs la sm n space of few specimens cover almost the entire range previously observed for bulk samples intra bone variability of ce anomalies as well as variable y ho and la la n is also observed sometimes diagenetic fluids with fractionated hree enriched compositions have entered the bone from the marrow cavity producing secondary ree uptake profiles theoretical intra bone fractionation trends modelled using lattice strain theory concur with most ree data but some trends cannot be modelled using realistic boundary conditions this fact as well as the occurence of positive and negative ce anomalies within the same fossil sample hint towards changing ree compositions of diagenetic fluids over the timescales of ree uptake because apparent ce anomalies frequently evolve over bone profiles and ce anomalies can be inherited from previous fractionation events ce anomalies are a highly ambiguous tracer for constraining ambient redox conditions in general bioapatite ree signatures may not always reliably reflect ambient taphonomic or redox conditions and diagenetic fluid compositions therefore ree patterns and ce anomalies of fossil bones must be interpreted cautiously as they vary spatially within skeletal remains and are affected by intra bone fractionation processes as well as changing compositions of the diagenetic fluid

bromalites from a turtle dominated fossil assemblage from the triassic of poland abstract bromalites coprolites and possibly some cololites from a turtle dominated fossil assemblage from the upper triassic of poland were studied bromalites collected at the poreba site are grouped within four morphotypes a b c and d attributable to sharks medium sized omnivorous or carnivorous tetrapods likely turtles sizable carnivorous archosaurs likely theropods and an indeterminate big herbivorous tetrapod possibly dicynodonts or aetosaurs respectively food residues abundant eggs possibly of parasites and microorganisms were found within the materials several lines of evidence suggest that at least part of the type b specimens might have been produced by turtles since a turtles are the prevailing tetrapods in the assemblage over 4 5 of tetrapod bone remains b coprolites are of adequate size and c they appear to have been produced by a carnivore of a low metabolic rate as seen in extant turtles the content of the type b specimens would imply that the late triassic turtle proterochersis porebensis was partly piscivorous but possibly complemented its diet with a more diversified foodstuff including plants semiaquatic habit of proterochersis porebensis might also provide a taphonomic explanation of the relative abundance of turtle remains at the poreba site poland shark bromalites and coprolite specimens attributable likely to theropod dinosaurs also contain abundant fish remains origin and classification of spiral and scroll bromalites left by fish are discussed in addition

mass extinction of peat forming plants and the effect on fluvial styles across the permian triassic boundary northern bowen basin australia abstract the most spectacular extinction event in earth s history occurred across the permian triassic boundary in the northern bowen basin a major coal bearing sedimentary basin in eastern australia a long lived c 9 myr cold climate peat mire ecosystem collapsed at the permian triassic boundary when the vast majority c 95 of peat producing plants became extinct the environmental change marked by the permian triassic boundary is expressed as an abrupt and sharp change in sedimentary regime at the contact between the rangal coal measures and the sagittarius sandstone the stratigraphic record shows no diminution in the thickness lateral extent or spatial distribution of coal seams prior to the boundary event the abrupt ecological shift at the permian triassic boundary was coincident with and interrelated to a change in landscape attributes and fluvial style the boundary shift is considered to reflect a short period radical atmospheric change accompanied by an abrupt change in plant ecosystems however palynological data indicate that it was preceded by a more gradual gross taxonomic progression in the floral succession the boundary shift is unlikely to reflect change in the tectonic setting of the northern bowen basin because the detrital character of clastic sediment supply shows no provenance change within the boundary sequence the late permian fluvial style is characterised by large scale up to 1 km wide sandstone dominated low sinuosity trunk river channel deposits the trunk river channels were flanked by extensive levee composite crevasse splay systems channel tracts were relatively stationary in position over enduring periods and developed stacked sediment accumulations up to 30 m thick the constrained character of the late permian trunk river systems was most likely due to progressive compaction of thick tracts of peat substrate and the stabilising effect of vegetation adjacent to the channel complex the well developed crevasse splays coupled with the low sinuosity style of the fluvial channels might suggest a perennial fluvial system characterised by short discharge periods as common in high latitude settings the fluvial architecture of the sagittarius sandstone the basal formation of the lower triassic rewan group is characterised by sheet like elements suggestive of broad shallow channels in a deforested braid plain setting the channel deposits are considered to represent highly mobile sandy systems dominated by a flashy runoff regime the mass extinction of plants in the northern bowen basin at the permian triassic boundary thus had a significant impact on the early triassic landscape and fluvial architecture

deep sea ecosystem revealed by teleost fish coprolites from the oligocene of poland abstract non spiral coprolites likely produced by teleost fish were studied from deep sea sediments of the oligocene rupelian of poland the materials were collected at the futoma and wola czudecka localities of the dynow marl member of the menilite formation western carpathian mountains the coprolites are elongate linear slightly to strongly sinuous and vary in size maximal diameter from 1 25 to 10 mm but appear to show a morphologic continuum rather than represent several morphotypes phosphatic matrix is preserved in 81 13 16 of the specimens and is composed primarily of putative fossilized bacteria the matrix contains numerous cavities possibly formed by gas bubbles or decomposition of organic matter and also an oval object resembling invertebrate eggs or another organic object at least 81 13 16 of the coprolite specimens contain fish remains bones scales a tooth which in some specimens include elements attributable to the predatory fishes palimphyes oligophus and an indeterminate gadiform this is indicative of fish predation upon other predatory fishes in this marine environment which probably exceeded 500 m of depth the coprolites are interpreted as produced by pelagic fish that lived in the oxygenated higher parts of the water column while the fecal matter sank and was deposited in anoxic conditions on the sea bottom identification of non spiral coprolites of fish and the fossil record of teleost coprolites are discussed

high resolution records of location and stratigraphic provenance from the rare earth element composition of fossil bones abstract bone apatite acts as a natural timed sampling device scavenging trace elements from local pore waters over timescales of ca 1 50 ka the rare earth element ree and u th composition of fossil bones reflects associated pore water compositions during the period of recrystallisation the ree composition of fossil bones is controlled by partitioning of ree between pore waters and particle surfaces and the ree composition of fossil bones reflects the ree composition of pore waters which vary spatially and temporally light ree are preferentially sorped onto particle surfaces thus the high la yb values seen in many bones from coastal marine and aeolian environments are best explained by release of ree from light ree enriched particles to local pore waters and subsequent immobilisation in recrystallising bones the ree compositions of bones recovered from pedogenically altered diatomite sediments of the olorgesailie formation of southern kenya vary over spatial scales of less than 10 m location accounts for 48 of the observed variation in bone chemistry and bones recovered from eight discrete excavations within the same time equivalent stratigraphic layer can be assigned to their excavation location with 70 accuracy based on a discriminant analysis of ree u and th composition despite this within layer variation bones recovered from different stratigraphic horizons within the olorgesailie formation can also be distinguished on the basis of their trace element composition bones recovered from four stratigraphic horizons spanning ca 0 5 million years were assigned to their correct stratigraphic layer with 90 accuracy where sedimentological conditions are favourable the trace element composition of fossil bone may be used to test stratigraphic provenance and burial location in excavated bone with a temporal resolution of

the apectodinium acme and terrestrial discharge during the paleocene eocene thermal maximum new palynological geochemical and calcareous nannoplankton observations at tawanui new zealand manifestations of profound perturbations in biogeochemical systems during the paleocene eocene thermal maximum petm include a prominent global negative 13c and a pronounced increase in the relative abundance of dinoflagellate cysts dinocysts assigned to the genus apectodinium while motile representatives of apectodinium were most likely thermophilic and heterotrophic the underlying causes of this dinoflagellate response are not well understood here we provide new insight by examining the palynology chemistry and calcareous nannoplankton across the petm in a continental slope section at tawanui new zealand across the petm marked changes in the relative abundance of apectodinium vary antithetically with significant changes in the 13c of carbonate and organic matter in general the high relative abundance of apectodinium relates to enhanced concentrations of dinocysts signifying a bloom of apectodinium in surface waters during the petm changes in apectodinium and 13c records correspond to variations in many other parameters including a smaller negative shift in bulk carbonate 13c than expected increased terrestrial palynomorphs elevated toc and c n ratios lower carbonate contents higher sio2 and al2o3 contents and lower si al ratios all of these variations can be explained by an increase in delivery of terrigenous material to the continental margin a peak in the relative abundance of glaphyrocysta dinocysts at the onset of the petm may indicate greater down slope transport of neritic material changes in calcareous nannoplankton abundances suggest increased nutrient availability in surface waters during the petm the combined results show that apectodinium dominated assemblages global perturbations in carbon isotopes and enhanced terrigenous delivery closely correspond in time at tawanui a sudden and massive carbon injection to the ocean atmosphere system may have enhanced weathering and increased terrigenous inputs to continental margins during the petm we further suggest that these inputs caused the apectodinium acme by elevating primary productivity in marginal seas

updated gondwana permian cretaceous earth history of australia abstract permo carboniferous glaciation confined to icecaps and mountain glaciers was followed by permian coal measures and early triassic barren measures and redbeds in the east terminally deformed in the mid triassic coal deposition resumed during the late triassic and tholeiite was erupted in the southeast after rifting the western margin was formed by the opening of the indian ocean at 156 and 132 ma at 140 ma a brief glaciation affected central australia by the 99 ma mid cretaceous the southern margin was finally shaped by the opening of the southeastern indian ocean the shoreline retreated to the present coast from the maximum aptian shoreline of an epeiric sea and the eastern highlands were uplifted to produce the present morphology of australia new data relate to the permo carboniferous and early cretaceous glaciations the kiaman reversed paleomagnetic interval events about the permian triassic boundary including possible impact craters advances in palynology invertebrate paleontology macrofloral paleontology and paleobiogeography the provenance of sediments by u pb ages and host rock affinity of zircons stable isotopes and biomarkers in petroleum systems coal environments calibrating the time scale with u pb ages of zircons fission track thermotectonic imaging geothermal energy and terranes split off the western margin

parameterization of mixed layer eddies part i theory and diagnosis ageostrophic baroclinic instabilities develop within the surface mixed layer of the ocean at horizontal fronts and efficiently restratify the upper ocean in this paper a parameterization for the restratification driven by finite amplitude baroclinic instabilities of the mixed layer is proposed in terms of an overturning streamfunction that tilts isopycnals from the vertical to the horizontal the streamfunction is proportional to the product of the horizontal density gradient the mixed layer depth squared and the inertial period hence restratification proceeds faster at strong fronts in deep mixed layers with a weak latitude dependence in this paper the parameterization is theoretically motivated confirmed to perform well for a wide range of mixed layer depths rotation rates and vertical and horizontal stratifications it is shown to be superior to alternative extant parameterizations of baroclinic instability for the problem of mixed layer restratification two companion papers discuss the numerical implementation and the climate impacts of this parameterization

north american continental margin records of the paleocene eocene thermal maximum implications for global carbon and hydrological cycling the impacts of the paleocene eocene thermal maximum petm 55 ma one of the most rapid and extreme warming events in earth history are well characterized in open marine and terrestrial environments but are less so on continental margins a major carbon sink here we present stable isotope carbonate content organic matter content and c n ratio records through the petm from new outcrop sections in california and from cores previously drilled on the new jersey margin foraminifer 18o data suggest that midlatitude shelves warmed by a similar magnitude as the open ocean 5 c 8 c while the carbon isotope excursion cie recorded both in carbonate and organic matter 13c records is slightly larger 3 3 4 5 than documented in open ocean records sediment accumulation rates increase dramatically during the cie in marked contrast to the open ocean sites in parallel mass accumulation rates of both organic and inorganic carbon also increased by an order of magnitude the estimated total mass of accumulated carbon in excess of pre cie rates suggests that continental margins at least along north america became carbon sinks during the cie mainly because of weathering feedbacks and rising sea level this result is significant because it implies that the negative feedback role of carbon burial on continental margins was greater than previously recognized

arctic late paleocene early eocene paleoenvironments with special emphasis on the paleocene eocene thermal maximum lomonosov ridge integrated ocean drilling program expedition 302 we reconstruct the latest paleocene and early eocene 57 50 ma environmental trends in the arctic ocean and focus on the paleocene eocene thermal maximum petm 55 ma using strata recovered from the lomonosov ridge by the integrated ocean drilling program expedition 302 the lomonosov ridge was still partially subaerial during the latest paleocene and earliest eocene and gradually subsided during the early eocene organic dinoflagellate cyst dinocyst assemblages point to brackish and productive surface waters throughout the latest paleocene and early eocene dinocyst assemblages are cosmopolitan during this time interval suggesting warm conditions which is corroborated by tex86 reconstructed temperatures of 15 18 c inorganic geochemistry generally reflects reducing conditions within the sediment and euxinic conditions during the upper lower eocene spectral analysis reveals that the cyclicity recorded in x ray fluorescence scanning fe data from close to eocene thermal maximum 2 53 ma presence confirmed by dinocyst stratigraphy is related to precession within the lower part of the petm proxy records indicate enhanced weathering runoff anoxia and productivity along with sea level rise on the basis of total organic carbon content and variations in sediment accumulation rates excess organic carbon burial in the arctic ocean appears to have contributed significantly to the sequestration of injected carbon during the petm

mesozoic ecosystems climate and biotas this issue of palaeogeography palaeoclimatology palaeoecology is devoted to papers on mesozoic ecosystems and is an outcome of the international geoscience program igcp 632 igcp is a joint opera

destruction of potential vorticity by winds the destruction of potential vorticity pv at ocean fronts by wind stress driven frictional forces is examined using pv flux formalism and numerical simulations when a front is forced by downfront winds that is winds blowing in the direction of the frontal jet a nonadvective frictional pv flux that is upward at the sea surface is induced the flux extracts pv out of the ocean leading to the formation of a boundary layer thicker than the ekman layer with nearly zero pv and nonzero stratification the pv reduction is not only active in the ekman layer but is transmitted through the boundary layer via secondary circulations that exchange low pv from the ekman layer with high pv from the pycnocline extraction of pv from the pycnocline by the secondary circulations results in an upward advective pv flux at the base of the boundary layer that scales with the surface nonadvective frictional pv flux and that leads to the deepening of the layer at fronts forced by both downfront winds and a destabilizing atmospheric buoyancy flux f b the critical parameter that determines whether the wind or the buoyancy flux is the dominant cause for pv

variability in satellite winds over the benguela upwelling system during 1999 2000 1 wind stress variability over the benguela upwelling system is considered using 16 months 01 august 1999 to 29 november 2000 of satellite derived quikscat wind data variability is investigated using a type of artificial neural network the self organizing map som and a wavelet analysis the som and wavelet analysis are applied to an extracted data set to find that the system may be divided into six discrete wind regimes the wavelet power spectra for these wind regions span a range of frequencies from 4 to 64 days with each region appearing to contain distinct periodicities to the north 10 23 5 s the majority of the power occurs during austral winter with a 4 16 day periodicity further investigation of national centers for environmental prediction reanalysis outgoing longwave radiation data indicates that the winter intensification of wind stress off the angolan coast is linked with convective activity over equatorial west africa the summer activity appears to be linked with the intensification of the angolan heat low convective activity over the congo basin appears to impact upon wind stress variability off the angolan coast throughout the year farther south 24 35 s the majority of the power occurs in the summer here a bimodal distribution occurs with peaks of 4 12 and 25 50 days the southernmost regions appear to be forced at higher frequencies by both midlatitude cyclones austral winter and mesoscale coastal lows austral summer at lower frequencies eastward propagating periodic wind events that originate over eastern south america appear to be important to the forcing of wind stress over the southern benguela

late quaternary terrestrial vertebrate coprolites from new zealand abstract over the past decade concerted efforts to find and study late quaternary terrestrial vertebrate coprolites in new zealand have revealed new insights into the diets and ecologies of new zealand s prehistoric birds here we provide a broader review of the coprolites found in natural non archaeological late quaternary deposits from new zealand we summarise the morphological diversity of the coprolites and discuss the taphonomy of the sites in which they are found since the 1870s more than 2000 coprolites have been discovered from 30 localities all restricted to the south island the distribution of coprolite localities appears to reflect the presence of geological and climatic factors that enhance the potential for coprolite preservation coprolites require dry conditions for preservation and have been found on the ground surface within drafting cave entrances and at shallow

submesoscale cold filaments in the gulf stream abstracta set of realistic very high resolution simulations is made for the gulf stream region using the oceanic model regional oceanic modeling system roms to study the life cycle of the intense submesoscale cold filaments that form on the subtropical gyre interior wall of the gulf stream the surface buoyancy gradients and ageostrophic secondary circulations intensify in response to the mesoscale strain field as predicted by the theory of filamentogenesis it can be understood in terms of a dual frontogenetic process along the lines understood for a single front there is however a stronger secondary circulation due to the amplification at the center of a cold filament filament dynamics in the presence of a mixed layer are not adequately described by the classical thermal wind balance the effect of vertical mixing of momentum due to turbulence in the surface layer is of the same order of magnitude as the pressure gradient and coriolis force and contributes equally to a so called turbulent therm

mesoscale to submesoscale transition in the california current system part ii frontal processes this is the second of three papers investigating the regime transition that occurs in numerical simulations for an idealized equilibrium subtropical eastern boundary upwelling current system similar to the california current the emergent upper ocean submesoscale fronts are analyzed from phenomenological and dynamical perspectives using a combination of composite averaging and separation of distinctive subregions of the flow the initiating dynamical process for the transition is near surface frontogenesis the frontal behavior is similar to both observed meteorological surface fronts and solutions of the approximate dynamical model called surface dynamics i e uniform interior potential vorticity q and diagnostic force balance in the intensification of surface density gradients and secondary circulations in response to a mesoscale strain field however there are significant behavioral differences compared to the surface dynamics model wind stress acts on fronts through nonlinear ekman transport and creation and destruction of potential vorticity the strain induced frontogenesis is disrupted by vigorous submesoscale frontal instabilities that in turn lead to secondary frontogenesis events submesoscale vortices and excitation of even smaller scale flows intermittent submesoscale breakdown of geostrophic and gradient wind force balance occurs during the intense frontogenesis and frontal instability events

rare earth elements and stable isotope geochemistry δ13c and δ18o of phosphorite deposits in the gafsa basin tunisia rare earth elements ree and stable isotope compositions 13c and 18o of shark teeth and phosphatic coprolites were analyzed from the lower maastrichtian layers of the el haria formation and two sequences of the paleocene eocene p e chouabine formation in the gafsa basin south western of tunisia in order to trace the sedimentological climatic and oceanographic conditions the ree chemistry and their distribution in the two archives are the same for each of the studied layers indicating that the coprolites and shark teeth experienced the same early diagenetic environments however major differences occur between the maastrichtian and the p e reflecting changes in the depositional conditions the early maastrichtian burial environment tended to be more anoxic with ree derived from reduced feo while in the p e the ree patterns mimic the modern oxic suboxic seawater the ree source from remineralisation of organic coating could have more significance the oxygen isotope compositions of the structural phosphates 18opo4 indicate a stable and warm climate during both studied time intervals a small offset 0 4 in the 18o value between the coprolites and shark teeth show minor thermal gradient between bottom and surface water the pronounced negative shift of 3 4 in 13c values recorded in the upper part of the chouabine formation was ascribed to the paleocene eocene boundary at the same time the lack of negative change in the 18o is explained by the semi closed situation of the gafsa basin which situation also played an important role in the evolution of the organic matters in the sediment resulting in the exceptional low 13c values

temnospondyls from the beaufort group karoo basin of south africa and their biostratigraphy abstract the permo triassic beaufort group karoo basin of south africa is biostratigraphically subdivided into eight temporally successive assemblage zones based on therapsids mammal like reptiles the temnospondyli fossil tetrapods usually regarded as extinct amphibians are second only to therapsids in terms of diversity and abundance in these strata with nine higher level taxa families known temnospondyls are also playing an increasingly important role in biostratigraphy and correlation of the beaufort strata the lower beaufort group late permian contains six of the eight biozones but only one temnospondyl family the rhinesuchidae whose record in the karoo is the richest in the world however rhinesuchid taxonomy remains in flux and the group is thus of limited biostratigraphic utility the early triassic lystrosaurus assemblage zone middle beaufort group contains the rhinesuchidae amphibamidae lydekkerinidae tupilakosauridae rhytidosteidae mastodonsauridae and trematosauridae although the biostratigraphy of temnospondyls within this biozone is poorly constrained the uppermost reaches of the lystrosaurus biozone contain a paucity of fossils but includes kestrosaurus mastodonsauridae and trematosuchus trematosauridae taxa previously thought to pertain to the lower part of the overlying cynognathus biozone the late early to middle triassic cynognathus assemblage zone upper beaufort group hosts the mastodonsauridae trematosauridae brachyopidae laidleriidae and possibly the rhytidosteidae based largely on the spatial and temporal distribution of mastodonsaurids this biozone has been biostratigraphically subdivided into a lower a middle b and upper c subzones characterised by differing ages and faunas

rare earth elements in pore waters of marine sediments abstract the rare earth elements rees were measured in pore waters of the upper 25 cm of sediment from one site off peru and three sites on the california margin the pore water ree concentrations are higher than sea water and show systematic down core variations in both concentration and normalized pattern from these analyses and from comparison to other chemical species measured dissolved fe mn ba oxygen nitrate phosphate it is suggested that pore water rees can be grouped into three categories those that are from an fe source those that are from a poc source and cerium oxide rees from the fe source appear where anoxia is reached they have a distinctive middle ree mree enriched pattern the concentrations in this source are so elevated that they dominate ree trends in the fe oxide reduction zone the net result of flux from the poc source is relative enrichment of heavy rees hrees over light rees lrees reflecting remineralizing poc and complexation with doc a common linear ree pattern seen in both oxic and anoxic sediments is associated with this poc source as well as a hree enriched pattern that is seen in surficial sediments at the peru site overall the pore water results indicate that mn oxides are not an important carrier of rees in the oceans a ree biogeochemical model is presented which attempts to reconcile ree behavior in the water and sediment columns of the oceans the model proposes that poc fe oxide and ce oxide sources can explain the ree concentration profiles and relative abundance patterns in environments ranging from oxic sea water to anoxic pore water the model is also consistent with our observation that the ce anomaly of pore water does not exceed unity under any redox condition

contrasting paleoceanographic conditions off morocco during heinrich events 1 and 2 and the last glacial maximum abstract past hydrological and primary productivity regimes on the basis of dinocyst and foraminiferal fossil assemblages as well as on stable isotopes o c and alkenones were investigated over the last 30 ka at upwelling site md04 2805 cq off morocco the results show highest upwelling intensity during heinrich event he 1 time coeval with a distinct plateau of heavy planktonic 13 c values high concentrations of pinus pollen and heterotrophic dinocysts caused by an increased northern wind regime in addition we also present regional reconstructions of paleo sea surface temperatures ssts using three different proxy tools dinocyst and foraminiferal transfer functions as well as alkenones u k 37 sst the reconstructed ssts depict coherent scenarios as modulated by the typical northern hemisphere climatic fluctuations furthermore specific occurrences of the dinocyst spiniferites lazus and of the foraminifer turborotalita quinqueloba are noted for he 2 he 1 and the younger dryas whereas in the alboran sea and in peri iberian waters these cold events were accompanied by the dinocyst bitectatodinium tepikiense and the subpolar foraminifer neogloboquadrina pachyderma s both implying a marked southward shift in the planktonic population in response to the migration of polar water masses this very pronounced demarcation between the planktonic communities better seems to attest the presence of a distinct hydrological structure in proximity of the strait of gibraltar which separated at that time african north of morocco from european southern iberia water masses

rare earth elements in old biogenic apatites abstract the ree distributions in individual upper devonian conodonts have been measured by ion probe the patterns of all analyzed conodonts are enriched in middle ree eu gd and have a weak or no ce anomaly concentrations and la yb or la sm ratios vary very little within or among individuals from the same zone which suggests that uptake of labile ree from sediments was essentially quantitative therefore the ree signature of the primary carriers probably organic and oxyhydroxides particulates from marine suspensions was efficiently transferred to biogenic apatites and survived late diagenetic processes ree patterns of conodonts do not resemble those of present day seawater and post cretaceous biogenic phosphates which are typically depleted in nd and sm with a negative ce anomaly since ree distributions in the modern water column mimic those of nutrients we assume that in pre cretaceous seawater they were not controlled by surface biological activity we assume instead that ree in pre cretaceous seawater can be explained by mechanism of desorption adsorption on particle surfaces progressive extraction of lree from river water by oxyhydroxides leads to precipitates enriched in middle ree a simple quantitative model was calculated in order to illustrate the proposed mechanism

symmetric instability in the gulf stream abstract analyses of wintertime surveys of the gulf stream gs conducted as part of the clivar mode water dynamic experiment climode reveal that water with negative potential vorticity pv is commonly found within the surface boundary layer sbl of the current the lowest values of pv are found within the north wall of the gs on the isopycnal layer occupied by eighteen degree water suggesting that processes within the gs may contribute to the formation of this low pv water mass in spite of large heat loss the generation of negative pv was primarily attributable to cross front advection of dense water over light by ekman flow driven by winds with a down front component beneath a critical depth the sbl was stably stratified yet the pv remained negative due to the strong baroclinicity of the current suggesting that the flow was symmetrically unstable a large eddy simulation configured with forcing and flow parameters based on the observations confirms that the observed structure of the sbl is consistent with the dynamics of symmetric instability si forced by wind and surface cooling the simulation shows that both strong turbulence and vertical gradients in density momentum and tracers coexist in the sbl of symmetrically unstable fronts si is a shear instability that draws its energy from geostrophic flows a parameterization for the rate of kinetic energy ke extraction by si applied to the observations suggests that si could result in a net dissipation of 33 mw m 2 and 1 mw m 2 for surveys with strong and weak fronts respectively the surveys also showed signs of baroclinic instability bci in the sbl namely thermally direct vertical circulations that advect biomass and pv the vertical circulation was inferred using the omega equation and used to estimate the rate of release of available potential energy ape by bci the rate of ape release was found to be comparable in magnitude to the net dissipation associated with si this result points to an energy pathway where the gs s reservoir of ape is drained by bci converted to ke and then dissipated by si and its secondary instabilities similar dynamics are likely to be found at other strong fronts forced by winds and or cooling and could play an important role in the energy balance of the ocean circulation

dietary and environmental implications of early cretaceous predatory dinosaur coprolites from teruel spain coprolites from the early cretaceous vertebrate bone bed at arino in teruel spain were analyzed geochemically and palynologically they contain various inclusions such as small bone fragments abundant plant remains pollen and spores we attribute the coprolites to carnivorous dinosaurs based partly on their morphology together with the presence of bone fragments and a high content of calcium phosphate hydroxylapatite with calcite well preserved pollen and spore assemblages were identified in all coprolite samples and a slightly poorer assemblage was obtained from the adjacent sediments both indicating an early cretaceous albian age this shows that the coprolites are in situ and also confirms previous age determinations for the host strata the depositional environment is interpreted as a continental wetland based on the palynoflora which includes several hydrophilic taxa together with sparse occurrences of fresh water algae such as ovoidites and the absence of marine palynomorphs although the coprolites of arino samples generally are dominated by pollen produced by taxodiaceae cypress and cheirolepidiaceae a family of extinct conifers the sediment samples have a slightly higher relative abundance of fern spores the distribution of major organic components varies between the coprolite and sediment samples which is manifest by the considerably higher charcoal percentage within the coprolites the high quantities of charcoal might be explained by a ground dwelling species feeding on smaller vertebrates that complemented its diet with plant material from a paleoenvironment were wild fires were a part of the ecosystem the state of preservation of the spores and pollen is also more detailed in the coprolites suggesting that encasement in calcium phosphate may inhibit degradation of sporopollenin less

elevated mixing at a front 1 the mesoscale submesoscale and microscale structure of a front in the california current was observed using a towed vehicle outfitted with microconductivity sensors thirteen 60 km cross front sections from 0 to 350 m in depth were covered in 3 5 days objectively mapped data are fit via the omega equation to obtain vertical velocity a composite cross front section shows elevated mixing on the dense side within 10 20 km of the front water downwells and gradients are elevated there i e rossby number ro horizontal strain spice gradients and microscale thermal dissipation thermal eddy diffusivity kt reaches 10 3 m2 s 1 and increases 3 10 from the anticyclonic to the cyclonic side with a depth mean of 10 4 m2 s 1 the spatial structure of kt ro and are similar on the dense side suggesting an energy cascade from the mesoscale via the submesoscale to the microscale however it is unclear whether frontogenesis internal wave blocking by elevated vorticity or internal wave trapping by large produces the elevated mixing the mean turbulent heat flux opposes the mean restratifying mesoscale heat flux of 10 w m 2 and may allow the front to persist turbulent nitrate fluxes are 0 1 0 3 mmol m 2 s 1 chlorophyll fluorescence and beam transmission reveal a 6 km wide 100 km long alongfront streamer which is a deep biomass maximum time scales for mixing and nutrient fluxes are 0 3 3 days which are similar to phytoplankton growth rates and the time scale for frontal evolution

helical burrow casts of therapsid origin from the beaufort group permian of south africa abstract large helical burrow casts of vertebrate origin have been discovered at several localities in the lowermost strata of the teekloof formation of the beaufort group permian in the southwestern karoo basin south africa they are not only the oldest but also the first vertebrate burrows of helical geometry to be found in rocks of pre mammalian age the burrow casts are vertically disposed spiralling tubes filled with fine grained sandstone or siltstone often with a calcareous cement tube diameters gradually increase from 60 mm in the upper entrance decline through two non contacting dextral coils to about 160 mm at the base of the spiral whereupon the tube straightens and widens into a horizontal terminal chamber burrow depths range from 0 5 0 75 m and the ramp angle ranges from 10 to 32 although within any single spiral it is constant articulated skeletons of the small dicynodont diictodon have been found within the terminal chambers and spirals of three sand filled burrows linear ridges preserved on the outer walls and floor of some of the terminal chambers resemble scratch marks possibly made by the claws and beak of diictodon during burrow excavation the sedimentary sequences at two separate localities are interpreted as having been deposited by episodic sheet floods and distributary splay fans in the proximal floodbasin areas flanking an aggrading meanderbelt rise comparison is drawn between helical burrow casts in the lower beaufort and other recorded occurrences in particular daimonelix a beaver burrow from the miocene of nebraska fundamental similarities far outweigh differences to the extent that the beaufort helical burrows may be grouped with the daimonelices it is concluded that the excavation of large helical burrows an activity usually attributed to rodents was pre empted by mammal like reptiles some 50 million years before the first anatomical mammals evolved

the distribution of rare earth elements in groundwaters assessing the role of source rock composition redox changes and colloidal particles rare earth element ree dissolved organic carbon doc and trace element al mn fe sr ba u and th concentrations were measured in fourteen well water samples 0 22 m and one spring located along two transects set up in a catchment from western europe kervidy coet dan catchment france previous hydrological and hydrochemical no3 so42 investigations demonstrated that three chemically and spatially distinct groundwater types are present in this catchment which is fully confirmed by the ree and doc results these include i a shallow organic rich groundwater 4 4 doc 34 6 mg l from the wetland areas close to the river network this first groundwater type characterized by the development of temporary reducing conditions records high and variable ree contents 2 ree 16 ppb and displays slight or no negative ce anomaly ce ce 0 8 1 05 ii a shallow organic poor doc 3 mg l no3 rich groundwater type 86 8 no3 155 mg l located in the weathered schists below the hillslope domains this second type corresponds to recently recharged oxidized water and displays also high and variable ree concentrations 2 ppb ree 15 ppb but distinguish from the former by the occurrence of very strong negative ce anomalies ce ce 0 05 0 10 finally iii a deep organic poor doc 1 mg l nitrate poor no3 close to 0 2 mg l detection limit groundwater this third type corresponds to reduced water flowing into the deep fresh schists and yields low to very low ree contents ree 0 15 ppb as well as slight negative ce anomaly ce ce 0 8 to 0 9 temporal ree concentration variations were assessed using samples regularly collected over a six month period results show that the spatially distributed ce anomaly and ree pattern signatures are preserved throughout the studied period by contrast ree concentrations are quite variable through time especially in the wetland waters where the ree concentrations are seen to vary in phase with both redox changes and doc fe u and th content variations three ree rich water samples one doc rich and two doc poor were also filtered through membranes of decreasing pore size 100 000 d 30 000 d 5 000 d the results show that between about 40 to 65 of the ree present in the shallow doc poor groundwater samples are controlled by the colloidal fraction which is likely to consist in these inorganic waters of a mixture of mineral phases in the wetland groundwaters the fraction of ree controlled by microparticles is higher than 65 which confirms the predominant role of organic colloids as major ree carriers in wetland waters using the above data set in conjunction with analyses of soil samples we show that the deep ce anomalies found in the upper non organic part of the aquifer are probably not source rock inherited features most likely these anomalies arise from the oxidative precipitation of ce the very low ree content displayed by waters flooding the deep fresh schists is interpreted as due to the combined effects of i ph variation ii secondary sulfate mineral precipitation and iii the trapping of colloids borne ree by the aquifer rock pores data from wetland groundwaters show that the ree fe u and th budgets of these waters are mainly controlled by seasonal changes in redox conditions and organic matter content however unlike organic poor waters it appears difficult to relate the ce behaviour in these organic rich waters solely to redox conditions it is likely that the complexation of ce by organic colloids in the organic rich waters may mask redox changes by inhibiting the development of negative ce anomalies

lithostratigraphy tephrochronology and rare earth element geochemistry of fossils at the classical pleistocene fossil lake area south central oregon abstract one of the most famous fossiliferous pleistocene sites in the pacific northwest is fossil lake oregon until recently fossil collections from the area were not stratigraphically controlled owing to the lack of a detailed stratigraphic and chronologic framework our field studies reveal at least nine exposed thin rhythmic fining upward depositional packages most separated by disconformities analysis of interbedded tephras reveals that the rye patch dam 646 ka dibekulewe 610 ka tulelake t64 95 ka marble bluff 47 ka and trego hot springs 23 2 ka tephra layers are present in the section indicating deposition from more than 646 ka to less than 23 ka which includes both the late irvingtonian and rancholabrean north american land mammal ages a much longer time span than previously believed bones analyzed from eight of the defined units have distinctly different rare earth element ree signatures fossils obtain ree during early diagenesis and signatures are probably closely

coprolites of marine vertebrate predators from the lower triassic of southern poland abstract numerous coprolites are described for the first time herein from the lower triassic olenekian shallow marine sedimentary rocks in southern poland x ray diffraction and geochemical analyses show that they are preserved as calcium phosphate with small admixtures of quartz and calcite additionally sem and thin section studies revealed that they contain highly fragmented faunal remains crinoids molluscs and vertebrates the size shape geochemistry biostratigraphic distribution and co occurrence with vertebrate skeletal remains imply that the coprolites at hand were likely produced by nothosaurids the durophagous sauropterygian reptiles and actinopterygian ray finned fish the large number of recorded coprolites implies that durophagous predation has been intense during the early triassic and suggests that the so called mesozoic marine revolution probably started soon after the end permian extinction furthermore discovery of sinusoidal trails attributable to nematodes in some coprolites implies that the intestinal parasitic associations with these predators had already evolved by at least the early triassic

newly discovered fish faunas from the early triassic karoo basin south africa and their correlative implications recent collecting in exposures of the lowermost burgersdorp formation beaufort group of the karoo basin of south africa has revealed a previously unknown fish fauna from the early triassic scythian lowermost cynognathus assemblage zone caz which forms an important component of the total vertebrate assemblage the newly discovered fish material includes lungfish saurichthyids and a large microfauna that includes numerous isolated chondrichthyan teeth two fin spine fragments and actinopterygian scales and teeth the latest fish finds together with the lowermost cynognathus assemblage zone vertebrate faunas make this karoo basin assemblage zone one of the most diverse early triassic faunal assemblages comparable in faunal diversity to those from the czatkowice formation poland and the arcadia formation australia the presence of the lungfish ptychoceratodus phillipsi in the early middle triassic cynognathus assemblage zone subzone b and in the underlying latest early triassic cynognathus assemblage zone subzone a indicates that these lungfish could serve as range index fossils within the caz and thus are potentially useful biostratigraphic markers across the early middle triassic boundary furthermore the new fish fauna provides a vital marine realm link in particular with the faunas of madagascar and australia that is unavailable using the tetrapod faunal elements of the lower caz

an early triassic polar predator ecosystem revealed by vertebrate coprolites from the bulgo sandstone sydney basin of southeastern australia abstract vertebrate trace fossils often provide a measure of cryptic biodiversity and are especially pertinent when skeletal remnants are exceptionally rare the lower triassic lower olenekian bulgo sandstone at long reef in the sydney basin of southeastern australia constitutes just such a deposit having yielded isolated bones of giant capitosaurian temnospondyls and proterosuchid archosauriforms together with abundant coprolites that are geochemically rich in elemental phosphate and carbon denoting vertebrate predators microstructural analysis of these preserved droppings reveals occasional bone fragments fish scales insect cuticles plant material and bacterial traces pseudomorph voids as well as silicate mineral particles ree concentrations indicate that burial and early diagenesis occurred explicitly within fluvial sediments furthermore external morphological characterization permits attribution of spiral coprolites to chondrichthyan or osteichthyan fishes polygonal ovoid spherical and typically flattened feces to temnospondyls and conspicuously large cylindrical droppings to archosauriforms or other amniote apex predators collectively the bulgo sandstone coprolite assemblage thus offers new insights into ecosystem structure and palaeoenvironment in what was an earliest triassic near polar setting such data compliments the documented skeletal record but indicates a greater range of aquatic and possibly terrestrial carnivores the latter being enigmatically sparse in the australian triassic and yet detected here via the hitherto underexplored trace fossil evidence of their ecological presence

early triassic early olenekian life in the interior of east gondwana mixed marine terrestrial biota from the kockatea shale western australia abstract a new terrestrial marine assemblage from the lower beds of a thin outcrop section of the kockatea shale in the northern perth basin western australia contains a range of fossil groups most of which are rare or poorly known from the lower triassic of the region to date the collection includes spinose acritarchs organic cemented agglutinated foraminifera lingulids minute bivalves and gastropods ammonoids spinicaudatans insects austriocaridid crustaceans actinopterygians a temnospondyl like mandible plant remains and spores and pollen of these groups the insects crustaceans and macroplant remains are recorded for the first time from this unit palynomorphs permit correlation to nearby sections where conodonts indicate an early olenekian smithian age the locality likely represents the margin of an early triassic shallow interior sea with variable estuarine like water conditions at the southwestern end of an elongate embayment within the east gondwana interior rift sag system preserved along the western australian margin monospecific spinose acritarch assemblages intertwined with amorphous organic matter may represent phytoplankton blooms that accumulated as mats and suggest potentially eutrophic surface waters the assemblage represents a mixure of marine and terrestrial taxa suggesting variations in water conditions or that fresh brackish water and terrestrial organisms were transported from adjacent biotopes some of the lower dark shaly beds are dominated by spinicaudatans likely indicating periods when the depositional water body was ephemeral isolated or subjected to other difficult environmental conditions the biota of the kockatea shale is insufficiently known to estimate biotic diversity and relationships of individual taxa to their permian progenitors and triassic successors but provides a glimpse into a coastal zone from the interior of eastern gondwana specialist collecting is needed to clarify the taxonomy of many groups and comparisons to other lower triassic sites are required to provide insights into the pattern of biotic decline and recovery at the end permian crisis

the south african stereospondyl lydekkerina huxleyi tetrapoda temnospondyli from the lower triassic of australia abstract the rsttetrapodfossilfromtherewanformationofthegalileebasin centralqueensland australia isidenti edas lydekkerinahuxleyi astereospondylfoundelsewhereonlyinthe lystrosaurus assemblage zone of south africa apomorphies shared with l huxleyi are anterior palatal vacuitywith anterodorsal projections from its posterior margin ventral surface of skull roof with series ofthickenedridges conditionunknowninotherlydekkerinids andvomerineshagreenpresent possibleautapomorphic reversal restudy of the only other australian lydekkerinid chomatobatrachus halei shows it to be distinct from l huxleyi the rewan formation undifferentiated in the galileebasin can be correlated with the rewan group of the bowen basin and to the early part of the lystrosaurus assemblage zone of the karoo basin south africa which are of griesbachian age varying palaeoenvironments may contribute to the contrasting nature of the australian and southafrican faunas keywords earlytriassic lydekkerina australia arcadiaformation

buoyancy and wind driven convection at mixed layer density fronts in this study the influence of a geostrophically balanced horizontal density gradient on turbulent convection in the ocean is examined using numerical simulations and a theoretical scaling analysis starting with uniform horizontal and vertical buoyancy gradients convection is driven by imposing a heat loss or a destabilizing wind stress at the upper boundary and a turbulent layer soon develops for weak lateral fronts turbulent convection results in a nearly homogeneous mixed layer ml whose depth grows in time for strong fronts a turbulent layer develops but this layer is not an ml in the traditional sense because it is characterized by persistent horizontal and vertical gradients in density the turbulent layer is however nearly homogeneous in potential vorticity pv with a value near zero using the pv budget a scaling for the depth of the turbulent low pv layer and its time dependence is derived that compares well with numerical simulations two dynamical regimes are identified in a convective layer near the surface turbulence is generated by the buoyancy loss at the surface below this layer turbulence is generated by a symmetric instability of the lateral density gradient this work extends classical scalings for the depth of turbulent boundary layers to account for the ubiquitous presence of lateral density gradients in the ocean the new results indicate that a lateral density gradient in addition to the surface forcing can affect the stratification and the rate of growth of the surface boundary layer