stromatolites near the permian triassic boundary in chongyang hubei province south china a geobiological window into palaeo oceanic fluctuations following the end permian extinction abstract stromatolites just after the end permian extinction are exceptionally well developed in the chongyang area of hubei province south china the stromatolites include endolithic coccoidal microbes and exhibit three growth forms columnar layered pseudo columnar and columnar each located in different stratigraphic horizons the columnar type is the most conspicuous and provides key information on the mode of their construction in this paper we describe the mega to microscopic features of these stromatolites together with interpretations of their construction the columnar type typically comprises alternations of lighter and darker laminae with intercalations of dense micritic laminae the lighter laminae are composed of fine to coarse calcite cement and fine dolomite whereas the darker laminae are composed of micrite and microspar endolithic coccoids are sporadic in these laminae in contrast the dense micritic laminae consist of micrite with abundant endolithic coccoids accentuating the laminae of stromatolites the columnar stromatolites were formed under deteriorating conditions after the end permian mass extinction as follows 1 the alternating development of lighter and darker laminae due to the colonization of different microbial communities in lower energy shallow to deep subtidal settings 2 carbonate precipitation within each microbial community through microbial metabolic activity and degradation of extracellular polymeric substances eps leading to the alternations of lighter and darker laminae 3 episodic interruption of the growth of the lighter and darker laminae by endolithic coccoidal activity and 4 high levels of endolithic activity accompanied by the precipitation of carbonate within boreholes to produce the dense micritic laminae in contrast the columnar layered and pseudo columnar types comprise alternations of lighter and darker laminae composed mainly of fine to coarse calcite cement fine dolomite micrite peloids and microspar with sporadic endolithic coccoids the dense micritic laminae are absent or rare in these stromatolites these types were essentially produced by the repetition of processes 1 and 2 documented in the columnar type the finely alternating laminae of these stromatolites are therefore the product of the repeated initiation and cessation of growth of relevant microbial communities in response to changing environmental conditions the stromatolites were formed immediately after the end permian extinction and persisted intermittently throughout the early triassic the chongyang stromatolites are undoubtedly some of the best developed stromatolites near the permian triassic boundary and retain a high resolution record of microbial successions and palaeo oceanic perturbations immediately following the end permian extinction

correlations between the classic parana and cape karoo sequences of south america and southern africa and their basin infills flanking the gondwanides du toit revisited

eddy zonal flow feedback in the southern hemisphere abstract the variability of the zonal mean zonal wind in the southern hemisphere is studied using eof analysis and momentum budget diagnostics of ncep reanalysis data 1978 97 the leading eof of the zonal mean zonal wind is well separated from the remaining eofs and represents the north south movement of the midlatitude jet analysis of the momentum budget shows that a positive feedback between the zonal mean wind anomalies and the eddy momentum fluxes accounts for the unusual persistence of eof1 and plays an important role in the selection of the leading eof of midlatitude variability further analysis also shows a propagating feedback common to both eof1 and eof2 which is responsible for the poleward drift of wind anomalies with time the observations support the following feedback mechanism anomalous baroclinic wave activity is generated at the latitude of anomalous temperature gradient that by thermal wind coincides with the latitude of the anomalous zonal jet the net propagation of baroclinic

on the persistence of cold season sst anomalies associated with the annular modes abstractin this study a simple stochastic climate model is used to examine the impact of the ocean mixed layer depth surface turbulent energy fluxes and ekman currents on the persistence of cold season extratropical sea surface temperature sst anomalies associated with variability in the annular modes of atmospheric circulation in both hemispheres observational analysis reveals that during the cold season sst anomalies associated with the southern annular mode sstsam persist considerably longer than those associated with the northern annular mode sstnam using the simple model it is shown that the persistence of the cold season sstsam is consistent with the simple stochastic climate paradigm in which the atmospheric forcing is approximated as white noise and the persistence of sst anomalies can be largely determined by the thermal inertia of the ocean mixed layer in the north atlantic however the simple climate model overestimates the persistence of the cold season sstnam it is thought th

microbial deposits in the aftermath of the end permian mass extinction a diverging case from the mineral mountains utah usa the lower triassic mineral mountains area utah usa preserves diversified smithian and spathian reefs and bioaccumulations that contain fenestral microbialites and various benthic and pelagic organisms ecological and environmental changes during the early triassic are commonly assumed to be associated with numerous perturbations productivity changes acidifica tion redox changes hypercapnia eustatism and temperature changes post dating the permian triassic mass extinction new data acquired in the mineral mountains sediments provide evidence to decipher the relationships between depositional environments and the growth and distribution of microbial structures these data also help to understand better the controlling factors acting upon sedimentation and community turnovers through the smithian early spathian the studied section records a large scale depositional sequence during the dienerian spathian interval during the transgression depositional environments evolved from a coastal bay with continental deposits to intertidal fenestral microbial limestones shallow subtidal marine sponge microbial reefs to deep subtidal mud dominated limestones storm induced deposits microbialite sponge reefs and shallow subtidal deposits indicate the regression three microbialite associations occur in ascending order i a red beds microbialite association deposited in low energy hypersaline supratidal conditions where microbialites consist of microbial mats and poorly preserved microbially induced sedimentary structure ii a smithian microbialite association formed in moderate to high energy tidal conditions where microbialites include stromatolites and associated carbonate grains oncoids ooids and peloids and iii a spathian microbialite association developed in low energy offshore conditions that is preserved as multiple decimetre thick isolated domes and coalescent domes data indicate that the morphologies of the three microbialite associations are controlled primarily by accommodation hydrodynamics bathymetry and grain supply this study suggests that microbial constructions are controlled by changes between trapping and binding versus precipitation processes in variable hydrodynamic conditions due to the presence of numerous metazoans associated with microbialites throughout the smithian increase in accommodation and spathian decrease in accommodation the commonly assumed anachronistic character of the early triassic microbialites and the traditional view of prolonged deleterious conditions during the early triassic time interval is questioned

on the causes of mass extinctions the temporal link between large igneous province lip eruptions and at least half of the major extinctions of the phanerozoic implies that large scale volcanism is the main driver of mass extinction here we review almost twenty biotic crises between the early cambrian and end cretaceous and explore potential causal mechanisms most extinctions are associated with global warming and proximal killers such as marine anoxia including the early middle cambrian the late ordovician the intra silurian intra devonian end permian and early jurassic crises many but not all of these are accompanied by large negative carbon isotope excursions supporting a volcanogenic origin most post silurian biocrises affected both terrestrial and marine biospheres suggesting that atmospheric processes were crucial in driving global extinctions volcanogenic atmospheric kill mechanisms include ocean acidification toxic metal poisoning acid rain and ozone damage and consequent increased uv b radiation volcanic darkness cooling and photosynthetic shutdown each of which has been implicated in numerous events intriguingly some of the most voluminous lips such as the oceanic plateaus of the cretaceous were emplaced with minimal faunal losses and so volume of magma is not the only factor governing lip lethality the missing link might be continental configuration because the best examples of the lip extinction relationship occurred during the time of pangaea many of the proximal kill mechanisms in lip extinction scenarios are also potential effects of bolide impact including cooling warming acidification and ozone destruction however the absence of convincing temporal links between impacts and extinctions other than the chicxulub cretaceous example suggests that impacts are not the main driver of extinctions with numerous competing extinction scenarios and the realisation that some of the purported environmental stresses may once again be driving mass extinction we explore how experimental biology might inform our understanding of ancient extinctions as well as future crises

permian endemic bivalves of the irati anoxic event parana basin brazil taphonomical paleogeographical and evolutionary implications abstract anoxic to dysoxic conditions must have existed in the parana basin during the deposition of the permian oil bearing shales of the irati formation reflecting the marine isolation of the basin from the panthalassic ocean in this environment benthic invertebrates are extremely rare in contrast to the overlying serra alta and teresina formations which were deposited in dysoxic oxic waters respectively hence the abundant shallow burrowing endemic bivalves recorded in the shales of the basal portion of the irati formation are one of the most distinctive features of this stratigraphic interval their preservation in offshore deposits is however a product of storm flows in shallow waters that swept the shells to distal settings subsequently these were sorted by long lasting shelf currents that produced dense 2 5 shells 20 cm2 pavements in which shells in a hydrodynamically stable posture convex up predominate forming thin complex shell concentrations despite their simple internal stratigraphy the new data presented here have important paleoecologic paleogeographic and evolutionary implications and indicate that a during the deposition of the oil rich shales of the irati formation numerous benthic bivalves thrived in the contemporary shallow water bottoms of the parana basin b the mono to paucispecific nature of the studied shell rich pavements is in part due to hydrologic shell transport and c restricted connections to open ocean waters panthalassa existed during irati times therefore the origin of the endemic passa dois molluscan fauna occurred somewhere between the interval represented by the underlying palermo formation and the basal portion of the irati formation finally these endemic bivalves appeared at least 10 million years earlier than previously thought

non chondritic platinum group element ratios in the earth s mantle the earth s upper mantle has an overabundance of highly siderophile elements platinum group elements gold and rhenium relative to what would be expected from equilibrium with the metallic core1 3 this excess is now widely believed to have been introduced as a late veneer by meteorite bombardment during early earth history but after separation of the core4 here we report high precision analyses of platinum group elements pges from fertile upper mantle iherzolites which show variations in relative abundances that exceed those in the chondritic meteorites that are thought to have furnished the late veneer5 in particular the pd ir ratio at about 1 76 is significantly greater than that of known chondritic meteorites6 our results combined with previous indications of both non chondritic and nearly chondritic pge ratios in the few other fertile mantle iherzolites that have been analysed2 3 7 11 strongly suggest that the mantle is heterogeneous in its pge content on scales of 100 kilometres if the observed pge ratios can be reconciled with a plausible meteoritic source the observed heterogeneity may reflect an original spatial variation in the late veneer otherwise an additional fractionation mechanism seems to be required

mixed carbonate siliciclastic microfacies from permian deposits of western gondwana evidence of gradual marine to continental transition or episodes of marine transgression abstract at the end of the paleozoic several intracratonic basins developed in gondwana including the parana basin in western gondwana permian sedimentary units include the passa dois group which encompasses four formations the irati serra alta teresina and rio do rasto and represents a transition from marine to continental depositional environments its strata correlate extensively from argentina to south africa and the irati and teresina formations in particular present mixed carbonate siliciclastic successions this interval has been speculated to have formed under several different paleoenvironmental scenarios however permian gondwana basin microfacies with no open sea influence have rarely been studied in addition in these basins there is a scarcity of micropaleontological studies and geochronological calibration besides an absence of marine index fossils in view of this a comprehensive microfacies study for the unit is developed with a large and representative surface and subsurface sample analysis of the passa dois group divided into three large geographic domains north central and south of the parana basin brazil thin sections distributed among the four units were analyzed with an emphasis on carbonate layers where the microfossils have a better chance to be recognized the data were interpreted within a revised biochronostratigraphic framework and integrated with bivalves macroflora palynology conchostracans and vertebrates biozones microfacies analysis resulted in the recognition of 13 microfacies four siliciclastic eight carbonate and one siliceous chert we observed a predominance of fine siliciclastic microfacies rich in organic matter in the southern domain rudaceous carbonate microfacies in the central domain with diverse allochemicals and the greater diversity of bioclasts and an increase on siliciclastic sediments influx in the northern domain of the basin where only the irati and teresina formations occur a shortage of microfossils was observed in the south domain where the carbonate microfacies are less varied than those to the north in the central domain coarse grained carbonates are present bivalves ostracods and sponge spicules are the main bioclasts on rudstones and grainstones from the irati and teresina formations and have been interpreted as allochthonous to parautochthonous the association of detrital and authigenic glauconite to bioaccumulations of sponge spicules is interpreted as episodes of marine transgression

geochronological constraints on the age of a permo triassic impact event u pb and 40ar 39ar results for the 40 km araguainha structure of central brazil abstract impact cratering has been a fundamental geological process in earth history with major ramifications for the biosphere the complexity of shocked and melted rocks within impact structures presents difficulties for accurate and precise radiogenic isotope age determination hampering the assessment of the effects of an individual event in the geological record we demonstrate the utility of a multi chronometer approach in our study of samples from the 40 km diameter araguainha impact structure of central brazil samples of uplifted basement granite display abundant evidence of shock deformation but u pb ages of shocked zircons and the 40ar 39ar ages of feldspar from the granite largely preserve the igneous crystallization and cooling history mixed results are obtained from in situ 40ar 39ar spot analyses of shocked igneous biotites in the granite with deformation along kink bands resulting in highly localized partial resetting in these grains likewise spot analyses of perlitic glass from pseudotachylitic breccia samples reflect a combination of argon inheritance from wall rock material the age of the glass itself and post impact devitrification the timing of crater formation is better assessed using samples of impact generated melt rock where isotopic resetting is associated with textural evidence of melting and in situ crystallization granular aggregates of neocrystallized zircon form a cluster of ten u pb ages that yield a concordia age of 247 8 3 8 ma the possibility of pb loss from this population suggests that this is a minimum age for the impact event the best evidence for the age of the impact comes from the u th pb dating of neocrystallized monazite and 40ar 39ar step heating of three separate populations of post impact inclusion rich quartz grains that are derived from the infill of miarolitic cavities the 206pb 238u age of 254 5 3 2 ma 2 error and 208pb 232th age of 255 2 4 8 ma 2 error of monazite together with the inverse 18 point isochron age of 254 10 ma mswd 0 52 for the inclusion rich quartz grains yield a weighted mean age of 254 7 2 5 ma 0 99 2 error for the impact event the age of the araguainha crater overlaps with the timing of the permo triassic boundary within error but the calculated energy released by the araguainha impact is insufficient to be a direct cause of the global mass extinction however the regional effects of the araguainha impact event in the parana karoo basin may have been substantial

hydrogeochemical spatialization and controls of the serra geral aquifer system in southern brazil a regional approach by self organizing maps and k means clustering abstract the aim of this study is to investigate the regional hydrogeochemical spatialization and controls of the serra geral aquifer system sgas a transboundary fractured aquifer across the southern region of brazil an extensive dataset of 1564 groundwater wells represented by 16 attributes was analyzed to identify spatial patterns and groups with similar hydrogeochemical facies an unsupervised machine learning approach self organizing maps som was used in combination with k means clustering to carry out the analysis som produces two dimensional representations allowing visual interpretation of nonlinear relationships between the attributes the stochastic davies bouldin index pointed out to an optimal number of four clusters highlighting significant differences in geochemistry cluster 1 is the most abundant and widespread corresponding to meteoric recharge cluster 2 is influenced by the weathering of basaltic rocks being widely distributed but with a higher density at the southeastern region cluster 3 is recognized as a mixing between all the other groups with a sparse distribution mostly in the extreme north of the area cluster 4 is dominated by ascending flow from the underlying sedimentary aquifers occurring in restricted areas this study shows that som can identify large scale spatial hydrogeochemical patterns of the sgas driven by structural and stratigraphic elements

30 million years of permian volcanism recorded in the choiyoi igneous province w argentina and their source for younger ash fall deposits in the parana basin shrimp u pb zircon geochronology evidence abstract we present four shrimp u pb zircon ages for the choiyoi igneous province from the san rafael block central western argentina dated samples come from the yacimiento los reyunos formation 281 4 2 5 ma of the cochico group lower choiyoi section andesitic breccias dacitic to rhyolitic ignimbrites and continental conglomerates agua de los burros formation 264 8 2 3 ma and 264 5 3 0 ma and cerro carrizalito formation 251 9 2 7 ma upper choiyoi section rhyolitic ignimbrites and pyroclastic flows spanning the entire permian succession of the choiyoi igneous province a single zircon from the el imperial formation that is overlain unconformably by the choiyoi succession yielded an early permian age 297 2 5 3 ma while the main detrital zircon population indicated an ordovician age 453 7 8 1 ma the new data establishes a more precise permian age artinskian lopingian for the section studied spanning 30 ma of volcanic activity volcanological observations for the choiyoi succession support the occurrence of explosive eruptions of plinian to ultraplinian magnitudes capable of injecting enormous volumes of tephra in the troposphere stratosphere the new shrimp ages indicate contemporaneity between the choyoi succession and the upper part of the parana basin late paleozoic section from the irati up to the rio do rasto formations encompassing about 24 ma geochemical data show a general congruence in compositional and tectonic settings between the volcanics and parana basin permian ash fall derived layers of bentonites thickness and granulometry of ash fall layers broadly fit into the depletion curve versus distance from the remote source vent of ultraplinian eruptions thus we consider that the choiyoi igneous province was the source of ash fall deposits in the upper permian section of the parana basin data presented here allow a more consistent correlation between tectono volcanic permian events along the paleo pacific margin of southwestern gondwana and the geological evolution of neighboring paleozoic foreland basins in south america and africa

the temporal autocorrelation structure of sea surface winds abstractthe temporal autocorrelation structures of sea surface vector winds and wind speeds are considered analyses of scatterometer and reanalysis wind data demonstrate that the autocorrelation functions acf of surface zonal wind meridional wind and wind speed generally drop off more rapidly in the midlatitudes than in the low latitudes furthermore the meridional wind component and wind speed generally decorrelate more rapidly than the zonal wind component the anisotropy in vector wind decorrelation scales is demonstrated to be most pronounced in the storm tracks and near the equator and to be a feature of winds throughout the depth of the troposphere the extratropical anisotropy is interpreted in terms of an idealized kinematic eddy model as resulting from differences in the structure of wind anomalies in the directions along and across eddy paths the tropical anisotropy is interpreted in terms of the kinematics of large scale equatorial waves and small scale convection modeling the vector w

observations of large scale ocean atmosphere interaction in the southern hemisphere abstract the authors provide a detailed examination of observed ocean atmosphere interaction in the southern hemisphere sh focus is placed on the observed relationships between variability in sh extratropical sea surface temperature sst anomalies the southern annular mode sam and the el nino southern oscillation enso results are examined separately for the warm november april and cold may october seasons and for monthly and weekly time scales it is shown that the signatures of the sam and enso in the sh sst field vary as a function of season both in terms of their amplitudes and structures the role of surface turbulent and ekman heat fluxes in driving seasonal variations in the sam and enso related sst anomalies is investigated analyses of weekly data reveal that variability in the sam tends to precede anomalies in the sst field by 1 week and that the e folding time scale of the sam related sst field anomalies is at least 4 months the persistence of the sam related sst anomalies is

effects of ekman transport on the nao response to a tropical atlantic sst anomaly abstract a recent study showed that a tropical atlantic sea surface temperature sst anomaly induces a significant coupled response in late winter february april fma in a coupled model in which an atmospheric general circulation model is coupled to a slab mixed layer ocean model agcm ml the coupled response comprises a dipole in the geopotential height like the north atlantic oscillation nao and a north atlantic tripole in the sst the simulated nao response developed 1 or 2 months later in the model than in observations to determine the possible effects of ekman heat transport on the development of the coupled response to the tropical forcing an extended coupled model agcm eml including ekman transport in the slab mixed layer ocean is now used large ensembles of agcm eml experiments are performed parallel to the previous agcm ml experiments with the model forced by the same tropical atlantic sst anomaly over the boreal winter months september april the inclusion of ekman heat tra

observed relationships between the el nino southern oscillation and the extratropical zonal mean circulation abstract there is increasing evidence indicating that the climate response to variations in the el nino southern oscillation enso includes not only thermally forced zonal wind anomalies in the subtropics but also eddy driven zonal wind anomalies that extend into the mid high latitudes of both hemispheres in this study new insights into the observed seasonally varying signature of enso in the extratropical zonal mean circulation are provided and the associated linkages with the dominant patterns of extratropical variability are examined the zonal mean extratropical atmospheric response to enso is characterized by two principal features an equivalent barotropic dipole in the southern hemisphere sh zonal mean zonal flow with centers of action located near 40 and 60 during austral summer and a weaker but analogous dipole in the northern hemisphere nh with centers of action located near 25 and 45 during early and late boreal winter both structures are accompanied by eddy momentum flux ano

tracing the earth s evolution how the earth s mantle became enriched in noble metals is difficult to explain unless they came from meteorites although many rocks in the mantle don t resemble meteorites new evidence says this theory cannot be ruled out

annular modes in the extratropical circulation part i month to month variability the leading modes of variability of the extratropical circulation in both hemispheres are characterized by deep zonally symmetric or annular structures with geopotential height perturbations of opposing signs in the polar cap region and in the surrounding zonal ring centered near 458 latitude the structure and dynamics of the southern hemisphere sh annular mode have been extensively documented whereas the existence of a northern hemisphere nh mode herein referred to as the arctic oscillation ao has only recently been recognized like the sh mode the ao can be defined as the leading empirical orthogonal function of the sea level pressure field or of the zonally symmetric geopotential height or zonal wind fields in this paper the structure and seasonality of the nh and sh modes are compared based on data from the national centers for environmental prediction national center for atmospheric research reanalysis and supplementary datasets the structures of the nh and sh annular modes are shown to be remarkably similar not only in the zonally averaged geopotential height and zonal wind fields but in the mean meridional circulations as well both exist year round in the troposphere but they amplify with height upward into the stratosphere during those seasons in which the strength of the zonal flow is conducive to strong planetary wave mean flow interaction midwinter in the nh and late spring in the sh during these active seasons the annular modes modulate the strength of the lagrangian mean circulation in the lower stratosphere total column ozone and tropopause height over mid and high latitudes and the strength of the trade winds of their respective hemispheres the nh mode also contains an embedded planetary wave signature with expressions in surface air temperature precipitation total column ozone and tropopause height it is argued that the horizontal temperature advection by the perturbed zonal mean zonal wind field in the lower troposphere is instrumental in forcing this pattern a companion paper documents the striking resemblance between the structure of the annular modes and observed climate trends over the past few decades

tropical atlantic sst forcing of coupled north atlantic seasonal responses recent observational studies reveal that a fall pan atlantic sea surface temperature sst anomaly composed of a horseshoe like dipole in the north atlantic and a southern center in the equatorial atlantic tends to precede the winter north atlantic oscillation nao and its related sst tripole by several months this study seeks to understand this relationship using large ensembles of atmospheric general circulation model agcm experiments and experiments with the agcm coupled to a mixed layer ocean agcm ml the models are forced either by the north atlantic horseshoe nah or by the tropical sst anomalies over the boreal winter months the agcm results show that the nah anomaly induces a baroclinic response in geopotential heights throughout the winter with little projection on the nao since the nah anomaly is ineffective in forcing the wintertime nao it cannot account for observations that the nah sst leads the nao in contrast in the agcm ml the coupled north atlantic response forced by the tropical anomaly exhibits a strong seasonal dependence in early winter the positive anomaly induces a trough east of newfoundland with a wave train to the northeast and in late winter the response projects strongly on a negative nao correspondingly the extratropical sst response features an nah like pattern in early winter and a tripole in late winter these results suggest that tropical atlantic sst anomalies can significantly influence the coupled extratropical variability the observed relationship between the fall nah sst and the winter nao or the sst tripole may be a consequence of persistent forcing of the seasonally varying atmosphere by tropical sst anomalies comparisons with the parallel agcm results indicate that the largely sign symmetric nao responses developed in the agcm ml are in part due to active extratropical sst feedbacks diagnostic experiments using a linear model further illustrate that in the absence of transient eddy feedbacks an idealized tropical heating induces anomalous flows that are qualitatively similar in early and late winter with a trough southeast of newfoundland and a ridge to the northeast the enhanced seasonality in the sst induced coupled response likely arises from the seasonal modulation of transient eddy feedbacks on the heatingforced anomalous flow

on the role of extratropical air sea interaction in the persistence of the southern annular mode using the daily atmosphere and ocean reanalysis data this study highlights the role of extratropical air sea interaction in the variability of the southern annular mode sam our analysis shows that the sam induced meridional dipolar sea surface temperature sst anomalies through surface heat fluxes can maintain persistent lower tropospheric temperature anomalies which further results in anomalous eddy momentum forcing enhancing the persistence of the sam with the finite amplitude wave activity diagnosis we illustrate that response of the eddy momentum forcing to sst anomalies can be attributed to changes in both baroclinic processes as baroclinic eddy generation and barotropic processes as wave breaking thus resultant diffusive eddy mixing with the former confined at high latitudes and the latter strongest at midlatitudes spectral analysis further suggests that the above air sea interactions are important for bimonthly and longer time scale sam variations the dipolar sst pattern may be an indicator for predicting subseasonal and interseasonal variabilities of the sam

a new u pb zircon age dating and palynological data from a lower permian section of the southernmost parana basin brazil biochronostratigraphical and geochronological implications for gondwanan correlations abstract index species useful for correlations with the international stratigraphical column are rare or absent in the pennsylvanian permian strata of the parana basin in brazil preventing accuracy in geochronologic assignments besides absolute datings are very scarce in comparison with other gondwana basins this paper presents palynological data from an outcrop on the surroundings of the candiota coal mine southmost brazil from several levels of the rio bonito and palermo formations the presence of certain index species of spore pollen allowed the recognition of two permian palynozones the vittatina costabilis and the lueckisporites virkkiae zones furthermore u pb in zircons from a volcaniclastic level interbedded in the coal strata of the former unit was analyzed through la mc icp ms method providing a new absolute age dating of 281 4 3 4 ma cisuralian early permian this dating is assumed as the oldest occurrence of the l virkkiae zone in parana basin which contains index species that are widespread in other gondwana basins a well distributed surface boundary occurs in this section also allowing local and regional correlations these new biostratigraphical and geochronological data are integrated in order to offer a deep analysis on the stratigraphical significance for correlations across the occidental gondwana

interdecadal variations in north atlantic sea surface temperature and associated atmospheric conditions abstract evidence is presented for a distinct pattern of ocean atmosphere relationship associated with interdecadal variability in the north atlantic region using a century of surface marine observations it is shown that middle and high latitude sea surface temperature sst display a long term fluctuation with negative anomalies before 1920 and during the 1970s and 1980s positive sst conditions prevailed from about 1930 to 1960 the pattern of interdecadal sst variability is constructed by subtracting the average field during 15 cold years from that during a similar interval of warm years the early century warming and the more recent cooling display a similar spatial pattern in both cases the pattern is basin scale and largely of one polarity with maxima in the vicinity of iceland in the labrador sea and northeast of bermuda the corresponding differences in surface atmospheric conditions are determined by averaging and subtracting in the same manner fields of sea level pressure slp and surf

the reemergence of sst anomalies in the north pacific ocean abstract sea surface temperature sst data and two different upper ocean temperature analyses are used to study the winter to winter recurrence of sst anomalies in the north pacific ocean the ssts recur when temperature anomalies that form in the deep ocean mixed layer in late winter early spring are isolated from the atmosphere in the summer seasonal thermocline and then reemerge at the surface when the mixed layer deepens during the following fall winter this reemergence mechanism is evaluated over the basin by correlating the time series of the leading pattern of ocean temperature anomalies in the summer seasonal thermocline 60 85 m in august september with sst anomalies over the course of the year the results indicate that the dominant large scale sst anomaly pattern that forms in the north pacific during late winter with anomalies of one sign in the central pacific and the opposite sign along the coast of north america is sequestered in the seasonal thermocline in summer and returns to the

advection and dissipation rates in the upper ocean mixed layer heat anomaly budget over the north atlantic in summer 1 processes contributing to the heat anomaly budget of the upper ocean mixed layer are examined over the north atlantic in summer season on the basis of the inversion of the sea temperature profiles the net advection velocity the subgrid heat diffusivity and the surface heat flux feedback are estimated two inversion strategies are pursued with and without the explicit parameterization of the entrainment heat flux into the upper mixed layer the regression estimator is employed for the inversion the data involved are the compilation of the comprehensive ocean atmosphere data set sea surface temperature sst and world ocean database 2001 temperature profiles over a 2 latitude 3 longitude grid for sequential 10 day intervals in june september during 1965 2000 the inversion is constrained by the autocorrelation of the national centers for environmental prediction net air sea heat flux the regression estimator allows for prediction of up to 60 70 of the sst anomaly value 10 days in advance by using the regressions on the sst anomalies lagged by two time steps the sst anomaly transport over the north atlantic agrees broadly with the known features of the surface circulation although the quantitative details of the sst anomaly propagation obtained in this inversion have not previously been available the heat anomaly that originates in the gulf stream region near the western boundary either moves northeastward with speed of up to 0 12 m s 1 downstream of the north atlantic current and the north atlantic drift current or it turns southeastward and then propagates southwestward along the broad subtropical recirculation in the subtropics the westward propagation is seemingly reinforced by the effects of the planetary waves the air sea feedback is negative with the feedback factor having the average value of 39 w m 2 k 1 with substantial variations throughout the north atlantic the entrainment rate is generally about 0 15 m d 1 relatively rapid deepening of the mixed layer by more than 2 10 6 m s 1 occurs near the gulf stream

the middle permian capitanian mass extinction on land and in the oceans abstract a middle permian mass extinction first discovered in 1994 has become known as the end guadalupian event in the literature however recent studies of foraminifera and brachiopod range truncations in conodont dated sections on the south china block have shown that the losses occur below this level in the middle of the capitanian stage extinctions were suffered by several other groups notably the corals whilst the mollusc record is more enigmatic a major bivalve crisis has been reported in some studies the giant alatoconchids being notable victims but not others gastropods were unaffected by the crisis whilst a roughly contemporaneous ammonoid mass extinction may have occurred in the early wuchiapingian a few million years after the main marine losses compilation of data from plant species in south china reveals a significant 24 loss suggesting that the capitanian crisis also occurred on land an intra capitanian extinction of 56 of plant species in north china block sequences may also have coincided with these losses correlation of these marine and terrestrial extinction events using the palaeomagnetic record provides two alternatives either turnover amongst plant species is contemporaneous with the marine extinction and the eruption of the emeishan flood basalt province in southwest china or plant losses post date the marine extinction and instead coincide with the waning phase of the igneous province current understanding of the major dinocephalian extinction suggests this event occurred during the preceding stage the wordian but future improvements in both sampling and dating this tetrapod crisis may reveal a synchronicity of plant animal and marine invertebrate extinctions the clear temporal link of the capitanian marine extinction with emeishan volcanism suggests that these flood basalt eruptions triggered the crisis a contemporaneous major negative c isotope excursion suggests that like many other mass extinction events methane release from hydrates may also be implicated however in the best dated chinese sections the main excursion is found to slightly post date the extinction which occurs at the end of an unusual and unexplained interval of exceptionally heavy 13c values other usual suspects for mass extinctions either lack geological and palaeontological evidence e g marine anoxia and global cooling or do not precisely correlate with the extinction e g major eustatic regression

extraction of mixed layer advection velocities diffusion coefficients feedback factors and atmospheric forcing parameters from the statistical analysis of north pacific sst anomaly fields abstract the statistical properties of observed north pacific sea surface temperature sst anomalies are simulated by a simple mixed layer advection and diffusion model with stabilizing feedback and local stochastic forcing by the atmosphere an optimal fit of the model to the sst auto and cross spectra yields the effective temperature advection velocities and diffusion coefficients in the mixed layer the local feedback factors and the strength and scales of the atmospheric forcing the results obtained by model fitting are in general agreement with independent direct estimates where such data are available the analysis supports previous models in which the origin of midlatitude sst anomalies on time scales of months to a few years is attributed to stochastic forcing by the atmosphere

coupled ocean atmosphere ice response to variations in the southern annular mode abstract the coupled ocean atmosphere ice response to variations in the southern annular mode sam is examined in the national center for atmospheric research ncar community coupled climate model version 2 the model shows considerable skill in capturing the predominantly zonally symmetric sam while regional deviations between model and observation sam winds go a long way in explaining the generally small differences between simulated and observed sam responses in the ocean and sea ice systems vacillations in the position and strength of the circumpolar winds and the ensuing variations in advection of heat and moisture result in a dynamic and thermodynamic forcing of the ocean and sea ice both meridional and zonal components of ocean circulation are modified through ekman transport which in turn leads to anomalous surface convergences and divergences that strongly affect the meridional overturning circulation and potentially the pathways of intermediate water ventilation a heat budget analysis de

the persistence of winter sea surface temperature in the north atlantic abstract the impact of the seasonal variations of the mixed layer depth on the persistence of sea surface temperature sst anomalies is studied in the north atlantic using observations a significant recurrence of winter sst anomalies during the following winter occurs in most of the basin but not in the subtropical area of strong subduction when taking reemergence into account the e folding timescale of winter sst anomalies generally exceeds 1 yr and is about 16 months for the dominant sst anomaly tripole the influence of advection by the mean oceanic currents is investigated by allowing for a displacement of the maximum recurrent correlation and alternatively by considering the sst anomaly evolution along realistic mean displacement paths taking into account the nonlocality of the reemergence generally increases the wintertime persistence most notably in the northern part of the domain the passive response of the mixed layer to the atmospheric forcing thus has a red spectrum down to near dec

the pacific center of action of the northern hemisphere annular mode real or artifact the leading empirical orthogonal function eof of the sea level pressure slp field referred to as the arctic oscillation ao or northern hemisphere annular mode nam consists of a dipole between the polar cap region and the surrounding zonal ring centered along 458n embedded within the outer ring are centers of action over the euro atlantic and pacific sectors in which slp fluctuates in phase that the observed slp fluctuations at these two centers of action are virtually uncorrelated raises the question of whether the pacific center in the annular mode could be an artifact of eof analysis it is argued that sea level pressure fluctuations at the pacific and euro atlantic centers of action of the ao nam would be more strongly correlated were it not for the fact that slp variability over the north pacific is dominated by a pattern in which fluctuations over the north atlantic and north pacific are inversely related evidence of the coexistence of such a pattern which resembles an augmented version of the pacific north american pattern is presented

on the teleconnectivity of the arctic oscillation the term arctic oscillation ao has recently been introduced to describe the leading structure of slp variability over the northern hemisphere a key feature of the ao is its zonally symmetric appearance with a primary center of action over the arctic and opposing anomalies in midlatitudes does the ao s annular appearance result from significant temporal correlations between slp anomalies at distant longitudes the results presented indicate that the temporal coherence between the arctic and midlatitudes is strongest over the atlantic sector with weak correlations between the atlantic and pacific midlatitudes both on intraseasonal and interannual time scales during the past 50 yrs hence the annular character of the ao is more a reflection of the dominance of its arctic center of action than any coordinated behavior of the atlantic and pacific centers of action in the slp field the ao is nearly indistinguishable from the leading structure of variability in the atlantic sector e g the north atlantic oscillation their temporal correlation is 0 95 for monthly data

synchronous variability in the southern hemisphere atmosphere sea ice and ocean resulting from the annular mode zonally symmetric fluctuations of the midlatitude westerly winds characterize the primary mode of atmospheric variability in the southern hemisphere during all seasons this is true not only in observations but also in an unforced 15 000 yr integration of a coarse resolution r15 coupled ocean atmosphere model here it is documented how this mode of atmospheric variability known as the southern annular mode sam generates ocean circulation and sea ice variations in the model integration on interannual to centennial timescales that are tightly in phase with the sam the positive phase of the sam is associated with an intensification of the surface westerlies over the circumpolar ocean around 608s and a weakening of the surface westerlies farther north this induces ekman drift to the north at all longitudes of the circumpolar ocean and ekman drift to the south at around 308s through mass continuity the ekman drift generates anomalous upwelling along the margins of the antarctic continent and downwelling around 458s the anomalous flow diverging from the antarctic continent also increases the vertical tilt of the isopycnals in the southern ocean so that a more intense circumpolar current is also closely associated with positive sam in addition the anomalous divergent flow advects sea ice farther north resulting in an increase in sea ice coverage finally positive sam drives increases in poleward heat transport at about 308s while decreases occur in the circumpolar region ocean and sea ice anomalies of the opposite sign occur when the sam is negative the ocean and sea ice fluctuations associated with the sam constitute a significant fraction of simulated ocean variability poleward of 308s year round the robustness of the mechanisms relating the sam to oceanic variability suggests that the sam is likely an important source of large scale variability in the real southern hemisphere ocean

arctic oscillation or north atlantic oscillation abstract the definition and interpretation of the arctic oscillation ao are examined and compared with those of the north atlantic oscillation nao it is shown that the nao reflects the correlations between the surface pressure variability at its centers of action whereas this is not the case for the ao the nao pattern can be identified in a physically consistent way in principal component analysis applied to various fields in the euro atlantic region a similar identification is found in the pacific region for the pacific north american pna pattern but no such identification is found here for the ao the ao does reflect the tendency for the zonal winds at 35 and 55 n to anticorrelate in both the atlantic and pacific regions associated with the nao and pna because climatological features in the two ocean basins are at different latitudes the zonally symmetric nature of the ao does not mean that it represents a simple modulation of the circumpolar flow an increase in the ao or nao implies stro

observational evidence of reemergence in the extratropical southern hemisphere observations of subsurface temperatures are used to examine the winter to winter reemergence of sea surface temperature sst anomalies in the extratropical south pacific ocean reemergence is the mechanism through which sst anomalies formed in the late winter are sequestered beneath the relatively shallow summer mixed layer and then reentrained into the deepening mixed layer during the following autumn winter although several studies have extensively examined reemergence in the northern hemisphere nh this is the first study to use observations of subsurface temperatures to document reemergence in the extratropical southern hemisphere sh the sh subsurface data reveal a pronounced reemergence signal in the western extratropical south pacific in this region surface thermal anomalies formed during late sh winter are observed to persist below the summertime mixed layer and reemerge at the surface during the followingearly winter months as such sst anomalies formed during late winter are strongly correlated with sst anomalies during the following early winter but are not significantly correlated with sst anomalies during the intervening summer months the results based on subsurface data are robust to small changes in the period of analysis and are qualitatively similar to existing evidence of reemergence in the nh analyses of independent sst data reveal that reemergence is widespread in the western extratropical south pacific basin but is less discernible in sst anomalies over the eastern part of the basin

shell beds as tools in basin analysis the jurassic of kachchh western india skeletal concentrations are ubiquitous in bathonian oxfordian shallow water sediments of the pericratonic basins of kachchh and rajasthan western india by analysing the biofabric of the concentrations and the taphonomic signatures of individual components it is possible to distinguish between the final concentration process recorded by the biofabric and events taking place prior to final deposition recorded by taphonomic signatures the skeletal concentrations are grouped in nine genetic types ranging from fair weather wave concentrations to storm concentrations and condensed concentrations they mainly reflect biological and hydraulic processes and in some instances permit estimates of their duration and show a rough zonation along a bathymetric gradient plotted against the stratigraphic sections the skeletal concentrations show in accordance with other sedimentological data three orders of bathymetric trends the first two orders are shallowing deepening cycles which possibly correspond to eustatic changes in sea level the third order represents parasequences with a strongly asymmetric sedimentary record skeletal concentrations are a useful additional tool in basin analysis but are best used in combination with other data

an abrupt extinction in the middle permian capitanian of the boreal realm spitsbergen and its link to anoxia and acidification the controversial capitanian middle permian 262 ma extinction event is only known from equatorial latitudes and consequently its global extent is poorly resolved we demonstrate that there were two severe extinctions amongst brachiopods in northern boreal latitudes spitsbergen in the middle to late permian separated by a recovery phase new age dating of the spitsbergen strata belonging to the kapp starostin formation using strontium isotopes and d 13 c trends and comparison with better dated sections in greenland suggests that the first crisis occurred in the capitanian this age assignment indicates that this middle permian extinction is manifested at higher latitudes redox proxies pyrite framboids and trace metals show that the boreal crisis coincided with an intensification of oxygen depletion implicating anoxia in the extinction scenario the widespread and near total loss of carbonates across the boreal realm also suggests a role for acidification in the crisis the recovery interval saw the appearance of new brachiopod and bivalve taxa alongside survivors and an increased mollusk dominance resulting in an assemblage reminiscent of younger mesozoic assemblages the subsequent end permian mass extinction terminated this late permian radiation

on the persistence of decadal sst anomalies in the north atlantic abstract historical wintertime sea surface temperature sst data show that a sandwich pattern dominates on the decadal timescales in the north atlantic at least after the 1970s the authors investigated how such decadal sst anomalies can survive against local thermal feedback which acts to dampen them rapidly at the surface winter sst anomalies have a negligible projection with the subsequent summer anomalies while they show a significant projection with the sst anomalies in the next winter on the other hand observed summer temperature anomalies below the mixed layer tend to have the same sign as the previous winter sst anomalies although the magnitude of the former is roughly one third of the latter this suggests that a reemergence mechanism of sst anomalies associated with the seasonal cycle of the mixed layer depth mld which has been verified by alexander and deser helps maintain the decadal sst anomalies in order to examine this scenario a mixed layer model driven by daily atmospheric d

on the reemergence of north atlantic sst anomalies abstract the reemergence mechanism whereby temperature anomalies extending over the deep winter mixed layer are stored beneath the surface in summer and are reentrained into the mixed layer when it deepens again in the following autumn and winter is studied in the north atlantic using approximately 40 years of surface and subsurface data reemergence is found to be robust in the sargasso sea and the northeast atlantic regions where i the mixed layer is much deeper in winter than in summer ii currents are relatively weak and iii temperature anomalies are coherent over broad areas the two leading empirical orthogonal functions of north atlantic sst anomalies also exhibit strong reemergence signatures a novel application of empirical orthogonal function analysis to temperature anomalies in the time depth plane which also incorporates information from all grid points is shown to be an efficient and useful approach for detecting reemergence without dependence on specific spatial patterns or prio

noble metal enrichment processes in the merensky reef bushveld complex we have analysed sulphides silicates and chromites of the merensky introduction reef for platinum group elements pges re and au using laser the enrichment of noble metals in layered gabbroic ablation inductively coupled plasma mass spectrometry and synthetic intrusions to form stratiform merensky type ore horizons pyrrhotite standards annealed with known quantities of noble metals is an extremely efficient yet poorly understood process os ir and ru reside in solid solution in pyrrhotite and pentlandite metal enrichment must be related to the formation of rh and part of the reef s pd in pentlandite whereas pt au re magmatic layering as the ore horizons form an integral and some pd form discrete phases olivine and chromite often part of the magmatic stratigraphies of their host insuspected to carry os ir and ru are pge free all phases analysed trusions metal concentration is also related to the prescontain noble metals as discrete micro inclusions with diameters ence of magmatic sulphides because the noble metals are either dissolved in base metal sulphides or occur as typically 100 nm inclusions in sulphides commonly have the discrete noble mineral phases intergrown with sulphides element combinations os ir pt and pt pd au inclusions in vermaak hendriks 1976 ballhaus ryan 1995 olivine and chromite are dominated by pt au pd few inclusion ballhaus ulmer 1995 spectra can be related to discrete noble metal phases and few there is considerable controversy as to where the inclusions have formed by sub solidus exsolution rather some metals came from and how metal enrichment worked pge inclusions notably those in olivine and chromite are earlyfor a stratiform platinum group element pge deposit magmatic nuggets trapped when their host phases crystallized we inside the magmatic stratigraphy of a layered intrusion suggest that the silicate melt layer that preceded the merensky reef there are two possibilities either the metals were derived was pge oversaturated at early cumulus times experiments from the melt column above the ore horizon or they came combined with available sulphide silicate partition coefficients sugfrom the magma equivalent to the cumulate package gest that a silicate melt in equilibrium with a sulphide melt underlying the ore owing to the large density contrast containing the pge spectrum of the merensky ore would indeed be between silicate and sulphide melt a popular view is that oversaturated with respect to the least soluble noble metals sulphide the metals were enriched by gravitational settling of melt apparently played little role in enriching the noble metals in sulphide melt i e out of the magma column above the the merensky reef rather its role was to immobilize a pre existing ore campbell et al 1983 barnes naldrett 1985 in situ stratiform pge anomaly in the liquid stratified magma naldrett et al 1987 on the other hand it is well chamber established that gravitational crystal settling plays little role in producing magmatic layering and magmatic stratigraphies mcbirney noyes 1979 morse 1986 campbell 1987 and this cannot remain without consequence for stratiform noble metal deposits a third alternative is noble metal enrichment by late

a paleoclimatic review of southern south america during the late paleozoic a record from icehouse to extreme greenhouse conditions abstract this paper provides a review of the late mississippian to permian paleoclimatic history for southern south america based on lithologic indicators biostratigraphic information and chronostratigraphic data the region is divided into three major types of basins 1 eastern intraplate basins e g parana basin 2 western retroarc basins e g paganzo basin and 3 western arc related basins e g rio blanco basin four major types of paleoclimatic stages are recognized in these basins 1 glacial late visean early bashkirian 2 terminal glacial bashkirian earliest cisuralian 3 postglacial cisuralian early guadalupian and 4 semiarid arid late guadalupian lopingian the glacial stage began in the late visean and continued until the latest serpukhovian or early bashkirian in almost all of the basins in southern south america during the bashkirian earliest cisuralian terminal glacial stage glacial deposits disappeared almost completely in the western retroarc basins e g paganzo basin but glaciation persisted in the eastern basins e g parana and sauce grande basins a gradual climatic amelioration postglacial stage began to occur during the earliest permian when glacial deposits completely disappeared across all of south america during this interval glacial diamictites were replaced by thick coal beds in the parana basin while north south climatic belts began to be delineated in the western basins which were likely controlled by the distribution of mountain belts along the panthalassan margin of south america towards the late permian climatic belts became less evident and semiarid or arid conditions dominated in the southern south america basins eolian dunes playa lake deposits and mixed eolian fluvial sequences occur in the parana basin and in the western retroarc basins volcanism and volcaniclastic sedimentation dominated along the western margin of south america at that time the stratigraphic record obtained in southern south america supports a long duration transition from icehouse to extreme greenhouse conditions

eurydesma lyonia fauna early permian from the itarare group parana basin brazil a paleobiogeographic w e trans gondwanan marine connection abstract here the biocorrelation of the marine invertebrate assemblages of the post glacial succession in the uppermost portion of the late paleozoic itarare group parana basin brazil is for the first time firmly constrained with other well dated gondwanan faunas the correlation and ages of these marine assemblages are among the main controversial issues related to brazilian gondwana geology in total 118 brachiopod specimens were analyzed and at least seven species were identified lyonia rochacamposi sp nov langella imbituvensis oliveira streptorhynchus sp cyrtella sp tomiopsis sp cf t harringtoni archbold and thomas quinquenella rionegrensis oliveira and biconvexiella roxoi oliveira the presence of tomiopsis sp cf t harringtoni and the bivalve atomodesma aphanaia orbirugata harrington in the teixeira soares beds plus myonia argentinensis harrington and heteropecten paranaensis neves et al both of which recorded in deposits in the teixeira soares and mafra beds butia suggests a biocorrelation with the eurydesma fauna from the bonete formation sauce grande colorado basin argentina furthermore the presence of lyonia archbold and praeundulomya cf subelongata dickins in the taciba formation indicates affinities with deposits in the lyons group carnarvon basin and the fossil cliff member perth basin western australia suggesting a late asselian early sakmarian age even more importantly the collected data suggest the existence of an w e trans gondwanan marine seaway between the parana brazil sauce grande colorado argentina huab hardap shale of the dwyka group aranos area namibia southwest africa the carnavon western australia basins and beyond eastward to the cimmerian region a v proto rift system through two major axes of extensional basin development facilitated the w e marine connection main axes formed by a north northwesterly trending axis paralleling the future south atlantic and a broadly north northeasterly trending line of separation related to the future indian ocean this proto rift system coupled with a sea level rise of at least 100 m favored the establishment of a long narrow shallow seaway allowing the exchange of eurydesma fauna between eastern and western gondwana

testing a dynamical model for mid latitude sea surface temperature anomalies abstract a slab model of the oceanic mixed layer is used to predict the statistical characteristics of the sea surface temperature anomalies that are forced by day to day changes in air sea fluxes in the presence of a mean current because of the short time scale of the atmospheric fields the model validity can be tested without quantitative information on the atmospheric forcing a procedure is developed for the case where the mean current is given it is applied to sea surface temperature sst anomaly data from the north pacific using ship drift data as estimates of the mean ocean currants at the 95 level of significance the model is consistent with the data over more than 85 of the investigated region the results indicate that the atmospheric forcing acts as a white noise forcing in regions of large currents advection effects are important at low frequencies however sst anomaly autospectra are equally well represented by a local model where advection is neglected the available meteorological

microbial proliferation coinciding with volcanism during the permian triassic transition new direct evidence from volcanic ashes south china abstract coupling with major biotic extinction both widespread microbially mediated deposits and ash beds characterize the permian triassic boundary ptb successions worldwide thus active volcanism through the ptb interval has been proposed to account for contemporary microbial bloom direct evidence however has long been scarce here we present several lines of evidence for microbial proliferation in the ptb ashes from south china petrographic analysis reveals annular granular and tubular bioalteration textures that formed during microbial dissolution of glass and subsequent precipitation annular textures appear as fresh glass shards connected with bands in different thicknesses showing rough and sharp interfaces and are bordered with fibrous textures granular textures are composed of clusters of near spherical bodies ranging in size from 0 05 to 2 m tubular textures occur as straight curved or spiral tunnels excavating into fresh glass their distinctive morphologies microbe analogous sizes and log normal size distributions all indicate a biogenic origin element mapping along alteration fronts shows enrichment of organic carbon and depletion in metabolically significant elements providing further support for their biogenicity besides textural relationships low n k and high c contents as well as pronounced microstructure density variations between different ash beds in same section all suggest that the bioalteration textures are syngenetic with volcanic glass relevant to microfossils rather than recent microbes we interpret the fossilized organic remains e g small coccoid like spheroids rods filaments and thin films as extracellular polymeric substances eps probably produced by microorganisms which might have served as templates for nucleation and played a crucial role in bio mineralization process the diversity of microstructure sizes shapes and organic remains may reflect a complex community of microbes in the ptb ashes we infer that microbial proliferation may contribute to negative c isotope excursions in the ptb ashes microbial blooms in ash beds directly triggered by large scale volcanism may reveal that extreme environmental stresses prevailed during the ptb crisis

a mechanism for the recurrence of wintertime midlatitude sst anomalies abstract in the early 1970s namias and born speculated that ocean temperature anomalies created over the deep mixed layer in winter could be preserved in the summer thermocline and reappear at the surface in the following fall or winter this hypothesis is examined using upper ocean temperature observations and simulations with a mixed layer model the data were collected at six ocean weather stations in the north atlantic and north pacific concurrent and lead lag correlations are used to investigate temperature variations associated with the seasonal cycle in both the observations and the model simulations concurrent correlations between the surface and subsurface temperature anomalies in both the data and the model indicate that the penetration of temperature anomalies into the ocean is closely tied to the seasonal cycle in mixed layer depth high correlations extend to relatively deep shallow depths in winter summer lead lag correlations in both the data and the model at some of the stations

trace elements in sulfide inclusions from yakutian diamonds sulfide inclusions in diamonds may provide the only pristine samples of mantle sulfides and they carry important information on the distribution and abundances of chalcophile elements in the deep lithosphere trace element abundances were measured by proton microprobe in 50 sulfide inclusions sdi from yakutian diamonds about half of these were measured in situ in polished plates of diamonds providing information on the spatial distribution of compositional variations many of the diamonds were identified as peridotitic or eclogitic from the nature of coexisting silicate or oxide inclusions known peridotitic diamonds contain sdis with ni contents of 22 36 consistent with equilibration between olivine monosulfide solid solution mss and sulfide melt whereas sdis in eclogitic diamonds contain 0 12 ni a group of diamonds without silicate or oxide inclusions has sdis with 11 18 ni and may be derived from pyroxenitic parageneses eclogitic sdis have lower ni cu and te than peridotitic sdis the ranges of the two parageneses overlap for se as and mo the mo and se contents range up to 700 and 300 ppm respectively the highest levels are found in peridotitic diamonds among the in situ sdis significant zn and pb levels are found in those connected by cracks to diamond surfaces and these elements reflect interaction with kimberlitic melt significant levels of ru 30 1300 ppm and rh 10 170 ppm are found in many peridotitic sdis sdis in one diamond with wustite and olivine inclusions and complex internal structures have high levels of other platinum group elements pges as well and high chondrite normalized ir pd comparison with experimental data on element partitioning between crystals of monosulfide solid solution mss and sulfide melts suggests that most of the inclusions in both parageneses were trapped as mss while some high cu sdis with high pd rh may represent fractionated sulfide melts spatial variations of sdi composition within single diamonds are consistent with growth histories shown by cathodoluminescence images in which several stages of growth and resorption have occurred within magmatic environments that evolved during diamond formation

paleotemperatures and paleofluids recorded in fluid inclusions from calcite veins from the northern flank of the ponta grossa dyke swarm implications for hydrocarbon generation and migration in the parana basin abstract the parana basin southern brazil has an atypical thermal and fluid history due to the occurrence of an episodic continental flood volcanism during the early cretaceous so far there are few data about the influence of this volcanic event on the paleotemperatures and paleofluids of the parana basin sedimentary rocks the teresina formation in the northern flank of the ponta grossa dyke swarm hosts high concentration of subsurface igneous rock bodies sills and dykes besides its covering by a hundreds meter thick volcanic rock cap in this study we used fluid inclusion analysis performed in horizontal and vertical calcite veins from the teresina formation and from a late cretaceous basic dyke to estimate paleotemperatures and to characterize the composition of diagenetic paleofluids homogenization temperatures of requilibrated fluid inclusions show that the teresina formation reached temperatures above 200 c horizontal parallel bedding calcite veins from the teresina formation record low to high salinity 2 26 wt nacl eq aqueous paleofluids the prevalence of high salinity fluid inclusions associated with light hydrocarbon fluid inclusions indicates deep buried fluids fluid inclusions in vertical calcite vein from basic dyke comprise only low salinity aqueous fluids 0 3 wt eq nacl interpreted as dominated by meteoric water the recorded paleotemperatures are attributed to the heating by the parana volcanic event during the early cretaceous with the thermal effect of the volcanic rock cap surpassing the effect of nearby sills and dykes estimated paleotemperatures higher than 200 c would allow the generation of light liquid and gaseous hydrocarbons overpressured compartments in the teresina formation allowed the expulsion of buried pore fluids high salinity aqueous fluids and hydrocarbons to fracture systems where they mixed with meteoric water the input of meteoric water through fracture systems connected with the surface favored hydrocarbons degradation in the early stages of source rock maturation during the early cretaceous

sea surface temperature anomalies planetary waves and air sea feedback in the middle latitudes the mechanisms that contribute to the generation and damping of large scale mid latitude sea surface temperature sst anomalies are discussed the sst anomalies reflect primarily the response of the upper ocean to the changes in air sea fluxes that are associated with daily weather fluctuations heat flux forcing is dominant in the lower middle latitudes while wind driven entrainment may be most effective in the high latitudes advection by anomalous ekman current is generally less important and ekman pumping is negligible the sst anomalies decay in part because of entrainment effects associated with mixed layer deepening and oceanic mixing and in part because of heat exchanges with the atmosphere the three approaches commonly used to model the evolution of sst anomalies are reviewed case studies based on monthly or seasonal anomaly maps of the large scale sst and atmospheric anomalies numerical simulations with one dimensional mixed layer models and stochastic forcing models we stress the similarities in the different approaches and discuss their main advantages and limitations the response of the atmosphere to mid latitude sst anomalies is considered first we discuss the poorly known relationship between sst anomalies and diabatic heating using a crude assumption for the air sea coupling we consider a two layer quasi geostrophic channel model and discuss the stationary wave response to sst anomaly forcing and the resulting air sea feedback it is found that the back interaction of the sst anomalies onto the atmosphere causes a weak sst anomaly damping at large scales and a strong one at small scales the air sea coupling should also act as an eastward propagator for the sst anomalies the response of more realistic linear wave models to prescribed diabatic heating is then reviewed and it is suggested that realistic mid latitude sst anomalies have a weak influence on the atmospheric circulation corresponding to changes in the geopotential height of 10 30 m at most this order of magnitude is consistent with the results of general circulation model experiments and with the limited climate predictability associated with mid latitude sst anomalies

effect of oceanic advection on the potential predictability of sea surface temperature abstract the effect of oceanic advection on the predictability of sea surface temperature sst is investigated in the framework of a linear stochastic model an analytical solution of a one dimensional model shows that even though advection can give rise to a pair of low frequency normal modes no enhancement in the predictability is found in terms of domain averaged error variance however a predictable component analysis shows that advection can play a role in redistributing the predictable variance when forced with a spatially coherent stochastic forcing advection enables certain regions to be more predictable than others this analytical result is further examined in a more realistic two dimensional north atlantic model with observed mean currents it is shown that the predictability of sst averaged over the whole north atlantic basin is determined by the thermal damping time scale 3 months not the advective time scale 6 years however the most predictable pattern reveals that the predicta

eddy zonal flow feedback in the northern hemisphere winter abstract the variability of the zonal mean zonal wind in the northern hemisphere winter december march is studied using eof analysis and momentum budget diagnostics of ncep ncar reanalysis data 1976 2001 the leading eof of the zonal mean zonal wind is well separated from the remaining eofs and represents the north south movement of the midlatitude westerlies analysis of the momentum budget shows that a positive feedback between the zonal mean wind anomalies and the eddy momentum fluxes selects the leading eof of midlatitude variability like the southern hemisphere the baroclinic eddies reinforce the zonal wind anomalies while external rossby waves damp the wind anomalies in the northern hemisphere the quasi stationary eddies also reinforce the zonal wind anomalies but the baroclinic eddies are most important for the positive eddy zonal flow feedback the observations support the following feedback mechanisms 1 above normal baroclinic wave activity is generated in the region of enhanced wester