use of topex poseidon sea level data for ocean analyses and enso prediction some early results abstract in this study two sets of pacific ocean analyses for 1993 96 were analyzed both analyses were produced with the assimilation of subsurface temperature data from expendable bathythermographs and tropical atmosphere ocean moorings in addition one analysis also assimilated sea level data from topex poseidon sea level variability in the two analyses agreed well with each other and both agree with tide gauge and altimetry data for 1993 95 however beginning in late 1995 through 1996 large sea level differences of 5 8 cm were found in the tropical western pacific between the two analyses furthermore large sea level discrepancies were also found between dynamic height estimated from tao temperatures and tide gauge altimetry observations in the same region during 1996 these discrepancies are consistent with the sea level differences between the two model based analyses historical conductivity temperature depth data along 165 e near the equator were also analyzed and it was found that salinity

deep seismic reflection profile in central europe reveals complex pattern of paleozoic and alpine accretion at the east european craton margin 1 the first deep reflection seismic profile was acquired across the teisseyre tornquist zone ttz a major european suture zone southeast of the avalonia baltica collision zone portraying different tectonic deformation styles thick versus thin skinned and phanerozoic crustal accretion episodes over a relatively short distance 240 km the overall crustal structure preserves image of the neoproterozoic passive margin setting but with a significant overprint of the repetitive tectonic convergence cadomian to alpine acting at the baltica margin in contrast to the avalonia baltica collision zone here the polygenetic crustal accretion occurring at the cratonic margin was ultimately shaped by significant strike slip faulting ttz is imaged as a narrow 10 15 km transform zone separating the thinned east european cratonic crust from the malopolska block

sizing up the sub tommotian unconformity in siberia sedimentary rocks in the western anabar region northwestern siberia preserve an exceptional record of evolution and biogeochemical events near the proterozoic cambrian boundary carbon isotopic data on petrographically and geochemically screened samples collected at 1 to 2 m intervals support correlation of the lower anabar succession staraya reckha and lower manykai formations with sub tommotian carbonates of the ust yudoma formation in southeastern siberia in contrast the upper manykai and most of the overlying medvezhya formation appear to preserve a sedimentary and paleontological record of an evolutionarily important time interval represented in southeastern siberia only by the sub tommotian unconformity correlation of the anabar section with other northern siberian successions that contain well dated volcanic rocks permits the estimate that the sub tommotian unconformity in southeastern siberia spans approximately 3 to 6 m y diverse small shelly fossils but not archaeocyathans previously thought to mark the base of the tommotian stage evolved sequentially throughout this earlier interval

balanced ocean data assimilation near the equator the question is addressed whether using unbalanced updates in ocean data assimilation schemes for seasonal forecasting systems can result in a relatively poor simulation of zonal currents an assimilation scheme where temperature observations are used for updating only the density field is compared to a scheme where updates of density field and zonal velocities are related by geostrophic balance this is done for an equatorial linear shallow water model it is found that equatorial zonal velocities can be detoriated if velocity is not updated in the assimilation procedure adding balanced updates to the zonal velocity is shown to be a simple remedy for the shallow water model next optimal interpolation oi schemes with balanced updates of the zonal velocity are implemented in two ocean general circulation models first tests indicate a beneficial impact on equatorial upper ocean zonal currents

ediacaran δ13c chemostratigraphy of south china abstract we report new 13 c chemostratigraphic data of the ediacaran system in south china using litho and biostratigraphic markers as independent calibrators we combine new and previously published 13 c data to construct a composite 13 c profile for the ediacaran system in south china the composite curve shows in chronostratigraphic order 1 a negative 13 c excursion en1 in the doushantuo cap carbonate that overlies the ghaub age nantuo diamictite 2 a pronounced positive 13 c excursion ep1 in the lower doushantuo formation where doushantuo type acanthomorphic acritarchs red algae and animal embryos first appear 3 a mild negative 13 c excursion en2 in the middle doushantuo formation 4 a positive 13 c excursion ep2 in the upper doushantuo formation where doushantuo type acanthomorphic acritarchs micrometazoans and stem group florideophyte red algae become abundant and diverse 5 a pronounced negative 13 c excursion en3 near the uppermost doushantuo formation 6 a strongly positive 13 c excursion up to 6 3 pdb ep3 in the lower dengying formation 7 a stable 13 c plateau ca 2 5 pdb ei in the middle and upper dengying formation where abundant vendotaenid algae macroscopic ediacaran fossils biomineralized animal tubes and mostly horizontal animal traces occur and 8 a 10 negative 13 c excursion en4 immediately below the ediacaran cambrian boundary the general pattern of this composite 13 c curve is robust despite a considerable amount of variation among the 13 c profiles of different sections this composite 13 c curve provides a first order chemostratigraphic framework for the subdivision and correlation of the ediacaran system in south china

tropical pacific ocean model error covariances from monte carlo simulations as a first step towards the development of an ensemble kalman filter enkf for ocean data assimilation in the tropical oceans this article investigates a novel technique for explicitly perturbing the model error in monte carlo simulations the perturbation technique involves perturbing the surface zonal stress estimates of the characteristics of the wind stress errors were obtained from the difference between zonal wind fields from the ncep and ecmwf re analyses in order to create random zonal wind stress perturbations an eof analysis was performed on the intraseasonally time filtered difference between the two re analysis products the first 50 eofs were retained and random wind stress fields for each ensemble member were created by combining random amounts of each eof ensemble runs were performed using a shallow water model with both short forecasts and long simulations results show covariance patterns characteristic of kelvin wave and rossby wave dynamics there are interesting differences between covariances using short forecasts and those using long simulations the use of the long simulations produced non local covariances e g negative covariances between east and west pacific whereas short forecasts produced covariances that were localized by the time it takes kevin and rossby waves to travel over the forecast period and the scales of spatial covariance in the wind stress errors the ensembles of short forecasts produced covariances and cross covariances that can be explained by the dynamics of equatorial rossby and kevin waves forced by wind stress errors the results suggest that the ensemble generation technique to explicitly represent the model error term can be used in an enkf

seismic basement in poland the area of contact between precambrian and phanerozoic europe in poland has complicated structure of sedimentary cover and basement the thinnest sedimentary cover in the mazury belarus anteclize is only 0 3 1 km thick increases to 7 8 km along the east european craton margin and 9 12 km in the trans european suture zone tesz the variscan domain is characterized by a 1 to 2 km thick sedimentary cover while the carpathians are characterized by very thick sediments up to c 20 km the map of the basement depth is created by combining data from geological boreholes with a set of regional seismic refraction profiles these maps do not provide data about the basement depth in the central part of the tesz and in the carpathians therefore the data set is supplemented by 32 models from deep seismic sounding profiles and a map of a high resistivity low conductivity layer from magnetotelluric soundings identified as a basement all of these data provide knowledge about the basement depth and of p wave seismic velocities of the crystalline and consolidated type of basement for the whole area of poland finally the differentiation of the basement depth and velocity is discussed with respect to geophysical fields and the tectonic division of the area

predatorial borings in late precambrian mineralized exoskeletons the late precambrian tube forming cloudina the earliest known animal to produce a mineralized exoskeleton shows evidence of having been attacked by shell boring organisms of more than 500 tubes from shaanxi province china 2 7 have rounded holes 40 to 400 micrometers in diameter the relation between the size of the holes and the width of the bored tubes suggests that the attacking organism was a predator selecting its prey for size if true this would be the oldest case of predation in the fossil record and would support the hypothesis that selection pressures from predation was a significant factor in the evolution of animal skeletons around the precambrian cambrian boundary

late precambrian pennatulids sea pens from the eastern yangtze gorge china paracharnia gen nov abstract pennatulids preserved as membranous carbonised compressions from the shibantan member dengying formation sinian system in the eastern yangtze gorge hubei province represent the first genuine discovery of the late precambrian ediacara type metazoan remains in china the specimens were initially referred to charnia ford 1958 and described as c dengyingensis by ding and chen in 1981 a re examination of the type material and comparing it with other late precambrian frond like forms particularly those from the ediacara assemblage of south australia and from the charnwood assemblage of england indicate that this chinese species represents a distinct genus paracharnia gen nov its characteristic polyp leaves individually free standing on distinct leaf stalks along the lateral sides of the median stem resemble those of many living sea pens represented by pennatula and contribute a significant feature to the precambrian charniidae glaessner 1979 its close association with abundant macroscopic algal remains of vendotaenia sp and its proximity to the overlying basal cambrian small shelly fossil assemblages in the same succession emphasise its palaeontological and biostratigraphic significance

new c isotope stratigraphy from southwest china implications for the placement of the precambrian cambrian boundary on the yangtze platform and global correlations a high resolution c isotope profile from a fossiliferous section spanning the precambrian cambrian pc c boundary on the yangtze platform southwest china is used to constrain c isotope chemostratigraphy and its global correlation the discovery of a strong negative c isotopic anomaly just below the china marker a indicates that this negative anomaly can be correlated globally and demonstrates that the pc c boundary of the chinese successions should be close to marker a on the basis of c isotope chemostratigraphic constraints and biostratigraphic data we find that c isotopic peak s2 also first reported here from the chinese successions can be correlated with c isotopic peak i in northern siberia and c isotope feature d in southwest mongolia by integrating the data from archaeocyaeothan fauna the c isotopic peak s3 in the middle dahai carbonates may be correlative with feature g in the mongolian section

using sims to decode noisy stratigraphic δ13c variations in ediacaran carbonates abstract carbonate carbon isotope 13ccarb chemostratigraphy is a valuable tool in precambrian stratigraphic correlation the effectiveness of this tool rests on the assumption that 13ccarb data record global seawater signals however in some cases 13ccarb data exhibit rapid and noisy stratigraphic variations that may have been influenced by authigenic or diagenetic carbonate minerals to assess the contribution of non primary minerals towards bulk carbonate carbon isotope values we acquired sims secondary ion mass spectrometry 13ccarb data electron microscopic data and cl cathodoluminescence microscopic data from two ediacaran successions the lower member ii of the doushantuo formation in south china and the mooifontein member of the zaris formation in southern namibia the doushantuo samples came from a stratigraphic interval with noisy meter scale 13ccarb variations of up to 10 whereas the mooifontein member is characterized by consistent 13ccarb values with limited meter scale variations of less than 4 our data show that the meter scale stratigraphic variations in 13ccarb are also mirrored in the sims data at m mm scales in both doushantuo and mooifontein samples in the doushantuo samples sims 13ccarb values of authigenic calcite vary by up to 10 over m mm scales and can be either higher or lower than those of the co existing dolomite matrix which also appears to be affected by authigenic carbonate on the basis of petrographic observation bulk sample 13ccarb values measured on powders microdrilled from the same sims specimens are within the range of sims 13ccarb values thus we infer that bulk sample 13ccarb values of doushantuo samples represent mixtures of different carbonate components the doushantuo and mooifontein sims 13ccarb data validate the traditional method of using chemostratigraphic consistency to evaluate authigenic diagenetic alteration but given that secondary phases may be 13c enriched relative to matrix carbonate caution is warranted when taking maximum values to approximate primary chemostratigraphic trends

neoproterozoic stratigraphy of the centralian superbasin australia abstract the basement of central australia includes the arunta block and the 1200 1100 ma musgrave block succeeded by 1075 1000 ma bimodal volcanic rifts and dolerite dykes a regional hiatus at 1000 800 ma interpreted as reflecting a central post volcanic underplated upland was followed at 800 ma by a second swarm of dykes in the musgrave block gawler craton and stuart shelf associated with the crustal sagging that initiated the centralian superbasin the centralian superbasin is defined here to encompass the neoproterozoic fill of the amadeus georgina ngalia officer and savory basins the intra cratonic superbasin was disrupted internally 540 600 ma ago petermann ranges orogeny by a central uplift and associated thrusts and by mid carboniferous 320 ma tectonism alice springs orogeny to form the structural basins listed above the stratigraphy and sedimentology of the relatively well known areas can be used as a basis for predicting those of the poorly known regions new results from acritarch biostratigraphy and isotope chemostratigraphy in conjunction with conventional lithostratigraphy and sequence analysis allow better stratigraphic resolution than previously possible field observations in the recently discovered savory basin in western australia provide a basis for correlations with the adjacent basins

extinction of cloudina and namacalathus at the precambrian cambrian boundary in oman biostratigraphic carbon isotope and u pb zircon geochronological data from the ara group of oman indicate an abrupt last appearance of cloudina and namacalathus coincident with a large magnitude but short lived negative excursion in the carbon isotope composition of seawater that is globally coincident with the precambrian cambrian boundary u pb zircon age data from an intercalated ash bed directly define this negative excursion to be at 542 0 0 3 ma consistent with previous age constraints from siberia and namibia combined with the global biostratigraphic record these new data strengthen hypotheses invoking mass extinction within terminal proterozoic ecosystems at or near the precambrian cambrian boundary

diagnostic model of the three dimensional circulation in the upper equatorial pacific ocean abstract to investigate the processes that maintain the large scale annual average thermal structure of the equatorial pacific the three dimensional ocean circulation for a large area is determined from a diagnostic model applied to repeated meridional hydrographic sections along 150 w and 11o w from 5 n to 5 s geostrophic balances are used to determine velocity profiles from 0 to 500 db across the boundaries of the region zonal velocities across 150 w and 110 w at approximately 1 lattitude intervals from 5 n to 5 s and meridional velocities across 5 n and 5 s averaged over the zonal distance between 150 w and 110 w poleward wind driven flows across 5 n and 5 s based on climatological zonal wind stress are added to the geostrophic velocities in the mixed layers to achieve overall mass conservation the reference dynamic height field at 500 db is adjusted at four of the 21 stations by about 1 dyn cm horizontal nondivergence is used to determine meridional velocities between 0 75 and 5 latitudes

geophysical constraints on the crustal structure of the east european platform margin and its foreland based on the polcrust 01 deep reflection seismic profile abstract a new 240 km long deep seismic reflection profile polcrust 01 was recently acquired in se poland crossing the east european platform eep margin south east of the north german polish caledonides ngpc here we document geophysical field work and subsequent data processing and modeling results obtained from reflection seismic data are augmented by results of the first arrival tomography applied to co located extended offset refraction data as well as potential field modeling and comparison with the available wide angle reflection refraction data our preferred model of the crustal structure derived by integrating seismic potential field and geological data is composed of crustal blocks terranes separated by nearly vertical faults these are i intact part of the eep ii ysogory terrane iii malopolska terrane and iv carpathian mts with their basement reflective lower crust of the eep can be an inherited feature of crustal extension rifting or compressional tectonics acting at the cratonic margin the teisseyre tornquist zone ttz is depicted as a caledonian transcurrent accretion zone corresponding with the near vertical tomaszow fault bounding the ysogory terrane to the east the crust of the ysogory terrane suggests eep affinity although its middle lower crust thickness is highly reduced the malopolska terrane seems to be internally subdivided into blocks of different magnetic properties of the lower crust the carpathian frontal thrust is associated with a change in the rock properties in the deep basement an unknown crustal block which is not visible in seismic data alone the interpreted structure of the caledonian terranes and their tectonic boundaries favors a transcurrent style of a crustal accretion along the central and se polish segments of the ttz implying a very complex nature of the caledonian accretionary belt of central europe from an array of terranes displaced along the ttz to an accretionary wedge of the collisional ngpc orogen between nw poland and southern north sea area

towering sponges in an early cambrian lagerstatte disparity between nonbilaterian and bilaterian epifaunal tierers at the neoproterozoic cambrian transition epifaunal suspension feeding bilaterian animals in the cambrian lived close to the sediment water interface and hence their ecological tiering levels were low 10 cm here we report an early cambrian diandongian or probably tommotian atdabanian lagerstatte from the hetang formation in anhui province south china the hetang biota is characterized by high tiering to 50 cm sponges and small 0 5 cm bilaterians including orthothecid hyoliths and bivalved arthropods nonbilaterian suspension feeders sponges cnidarians and archaeocyathids as high tiering animals and bilaterian suspension feeders as low tiering animals also characterize other neoproterozoic cambrian assemblages such as the ediacaran chengjiang burgess shale and sinsk biotas these data are consistent with medium to high tiering levels in neoproterozoic cambrian epifaunal communities but suggest that nonbilaterians achieved such tiering levels long before bilaterian suspension feeders did so in the early ordovician the disparity between bilaterian and nonbilaterian tierers during the neoproterozoic cambrian transition and the delayed appearance of high tiering bilaterians demand phylogenetic and ecological explanations the cambrian substrate revolution may have triggered a cascade of ecological evolution including the rise of bilaterian animals in high tiering levels during the ordovician radiation of the paleozoic fauna

redox dependent distribution of early macro organisms evidence from the terminal ediacaran khatyspyt formation in arctic siberia abstract the ediacaran period witnessed the first appearance of macroscopic animal life in earth s history however the biogeochemical context for the stratigraphic occurrence of early metazoans is largely uncertain in part due to the dearth of integrated paleobiological and chemostratigraphic datasets in this study a comprehensive geochemical analysis was conducted on the fossiliferous khatyspyt formation in arctic siberia in order to gain insights into the ediacaran paleoenvironments this study was designed to specifically address the relationship between paleoredox conditions and ediacaran fossil occurrences in the khatyspyt formation our data reveal a dramatic shift in pyrite sulfur isotope compositions 34 s pyrite from ca 20 to ca 55 and this shift is intriguingly associated with the first occurrence of ediacara type macrofossils at the studied section suggesting a possible link between seawater redox conditions and distribution of early macroscopic organisms based on multiple lines of sedimentological and geochemical evidence we propose that the development of oceanic euxinia which may be widespread in the continental margins due to enhanced oxidative weathering in the terminal ediacaran period may have locally prohibited the colonization of ediacara type organisms and resulted in low 34 s pyrite values in the lower khatyspyt formation in the middle and upper khatyspyt formation progressive secular transition from euxinic to non euxinic and more habitable conditions may have allowed for the colonization of ediacara type and other macro organisms

large scale slope instability at the southern margin of the ediacaran yangtze platform hunan province central china thirteen stratigraphical sections from the doushantuo formation hunan province central china indicate large scale mass wasting of the yangtze platform margin between the late neoproterozoic glaciation and the earliest cambrian numerous sedimentary discontinuities due to regional slides olistostromes and slumps have modified the stratigraphy between the shallow water carbonate platform margin and the siliciclastic slope slide blocks are predominantly gently deformed and are largely composed of shallow water dolomitized limestones slide sheets may reach a regional extent of up to 5000 km 2 and are embedded in anoxic shales at an unknown water depth

deep resistivity structure of the trans european suture zone in central poland summary the deep resistivity structure was estimated along a 400 km profile in central poland crossing the malopolska massif mm the lysogory unit lu the trans european suture zone tesz and ending at the east european craton eec magnetotelluric transfer functions corresponding to 20 sites were supplemented by magnetovariational responses obtained at the geomagnetic observatories situated at the same tectonic units such a combination made it possible to extend the initial period range which is from fractions of a second to several hours up to months in order to reliably cover crustal and upper mantle depths the geoelectrical structures revealed using 2 d inversions do not contradict the known features of the lithosphere structure determined using seismic and gravity data along the profile the subsurface conductance varying from approximately 10 siemens at the inner part of the eec to about 600 siemens in the tesz is produced by sediments the deep part of which contains conductive highly mineralized water the existence of two crustal conductive faults at the southwest and northeast of the tesz were established mainly by the use of induction arrows it was also revealed that rather high mantle conductivity beneath the mm lu and tesz at depths of about 150 200 km contrasts with the resistive upper mantle of the eec this can be interpreted as the decrease of asthenosphere conductance and or as its submersion beneath the eec generally the results confirm the idea that the tesz forms not only specific seismic boundaries but also causes peculiar conductivity anomalies in the crust and upper mantle

characteristics of stochastic variability associated with enso and the role of the mjo abstract to shed light onto the possible role of stochastic forcing of the el nino southern oscillation enso the characteristics of observed tropical atmospheric variability that is statistically uncoupled from slowly evolving sea surface temperature sst are diagnosed the madden julian oscillation mjo is shown to be the dominant mode of variability within these uncoupled or stochastic components the dominance of the mjo is important because the mjo generates oceanic kelvin waves and perturbs sst in the equatorial pacific that may feed back onto the el nino southern oscillation the seasonality present in the uncoupled zonal stress maximum in austral summer which reflects the seasonality of mjo activity is also transmitted to the eastern pacific thermocline variability by these kelvin waves hence the mjo component of the uncoupled stress could plausibly contribute to the observed phase locking of enso to the seasonal cycle during an el nino event maximum uncoupled zonal stress variance s

enso to multi decadal time scale changes in east australian current transports and fort denison sea level oceanic rossby waves as the connecting mechanism the connection between east australian current eac transport variability and australia s east coast sea level has received little treatment in the literature this is due in part to the complex interacting physical processes operating in the coastal zone combined with the sparsity of observations available to improve our understanding of these possible connections this study demonstrates a statistically significant at the 490 level relationship between interannual to decadal time scale variations in observed estimates of the eac transport changes and east coast sea level measured at the high quality long record fort denison tide gauge in sydney harbour australia 3315101800s 15111303200e we further demonstrate using a linear reduced gravity ocean model that enso to decadal time scale variations and the ocean adjusted multi decadal trend approx 1 cm decade in observed sea level at fort denison are strongly connected to modulations of eac transports by incoming westward propagating oceanic rossby waves we show that eac transport and fort denison sea level vary in a manner expected from both tasman sea generated rossby waves which account for the interannual and multi annual variability and remotely forced from east of new zealand rossby wave connections through the mid latitudes accounting for the ocean adjusted multi decadal trend observed at the new south wales coast with the regional tasman sea forcing explaining the greatest overall proportion of eac transport and sea level variances

50 myr recovery from the largest negative δ13c excursion in the ediacaran ocean sedimentary rocks deposited during the ediacaran period 630 542 ma contain carbonates whose carbon isotopic ratios show a marked negative excursion consisting of a precipitous drop from 5 to 12 followed by a sub linear recovery to positive 13c values isotopic ages u pb and thermal subsidence modelling are combined to constrain the excursion in time and indicate an onset at 600 ma and duration of recovery of approximately 50 myr the excursion is widely recognized in oman and has potential correlatives in ediacaran strata elsewhere and may thus represent a characteristic feature of the ediacaran period the amplitude of this carbon isotope excursion far exceeds those of other neoproterozoic anomalies the isotopic trend of negative excursion and long term recovery spanned at least one short lived glacial episode at 580 ma but appears unrelated to glaciation which indicates that negative anomalies in the neoproterozoic marine carbon isotope record are not directly or uniquely linked to ice ages

acanthomorphic acritarchs of the doushantuo formation from an upper slope section in northwestern hunan province south china with implications for early middle ediacaran biostratigraphy abstract doushantuo pertatataka acritarchs dpas are abundant and well preserved in the ediacaran doushantuo formation in south china not only do they provide insights into the marine ecosystem immediately after a neoproterozoic global glaciation they also afford us an ideal tool for ediacaran stratigraphic subdivision and correlation however previous reports of dpas in south china are mostly from the yangtze gorges area in intra shelf basin and from weng an in shelf margin environments while data from localities in slope and basinal facies are lacking here we present lithostratigraphy carbon and strontium isotope chemostratigraphy and acritarch biostratigraphy of the doushantuo formation from an upper slope section at lujiayuanzi in northwestern hunan province south china five dpa genera and eight species are preserved in the doushantuo formation chert nodules with the uppermost two dpa horizons occurring above a 13 c negative excursion that is correlated with the en3 shuram excursion based on integrated litho and chemostratigraphic correlation our new findings reveal a broader temporal and spatial distribution of dpas in south china and further support their biostratigraphic potential in the early middle ediacaran subdivision and correlation

lithospheric structure of the trans european suture zone along the ttz cel03 seismic transect from nw to se poland abstract the large scale celebration 2000 seismic experiment investigated the velocity structure of the crust and upper mantle between western portion of the east european craton eec and the eastern alps this area comprises the trans european suture zone the carpathian mountains the pannonian basin and the bohemian massif this experiment included 147 chemical shots recorded by 1230 seismic stations during two deployments good quality data along 16 main and a few additional profiles were recorded one of them profile cel03 was located in southeastern poland and was laid out as a prolongation of the ttz profile performed in 1993 this paper focuses on the joint interpretation of seismic data along the nw se trending ttz cel03 transect located in the central portion of the trans european suture zone first arrivals and later phases of waves reflected refracted in the crust and upper mantle were interpreted using two dimensional tomographic inversion and ray tracing techniques this modelling established a 2 d quasi 3 d p wave velocity lithospheric model four crustal units were identified along the transect from northwest to southeast thickness of the crust varies from 35 km in the pomeranian unit nw to 40 km in the kuiavian unit to 50 km in the radom ysogory unit and again to 43 km in the narol unit se the first two units are thought to be proximal terranes detached from the eec farther to the southeast and re accreted to the edge of the eec during the early palaeozoic the origin of the remaining two units is a matter of dispute they are either portions of the eec or other proximal terranes in the area of the polish basin first two units the p wave velocity is very low vp

a composite reference section for terminal proterozoic strata of southern namibia integrated sequence stratigraphic and chemostratigraphic data yield a framework for correlations of stratigraphic units in the terminal proterozoic to cambrian witvlei and nama groups of namibia coupled with precise u pb zircon age constraints these correlations make it possible to construct a composite reference section for use in calibrating terminal proterozoic chronostratigraphy the namibian reference section starts with two distinct glacial horizons and extends up to within 1 million years of the proterozoic cambrian boundary the two glacial horizons may represent each of two distinct varanger age glaciations better known from the north atlantic region from the higher of the two glacial horizons up the composite stratigraphy preserves one of the thickest and most complete available records of carbon isotope variability in post varanger terminal proterozoic seawater four carbon isotope chemostratigraphic intervals are recognized 1 a postglacial negative 13 c excursion npg interval 2 a rising interval pr interval of increasing positive delta 13 c values 3 a falling interval pf interval characterized by decreasing positive 13 c and culminating in near zero or negative values and 4 an interval of moderately positive relatively invariant 13 c values i interval that extends up to the unconformity that contains the proterozoic cambrian boundary each of these chemostratigraphic intervals can be recognized in widely separated correlative sections around the world by comparing sediment accumulation rate in the radiometrically calibrated namibian stratigraphy with sediment accumulation rates in correlative sections in arctic canada and oman a maximum age of 564 ma is estimated for the end of the younger varanger glaciation 25 m y younger than previous estimates

on the impact of local feedbacks in the central pacific on the enso cycle abstract while sea surface temperature sst anomalies in the eastern equatorial pacific are dominated by the thermocline feedback in the central equatorial pacific local wind effects such as zonal advection are important as well el nino southern oscillation enso simulations with a linear model improve markedly if these effects are included as a local wind stress feedback on sst an atmosphere model that reacts both to eastern and central pacific sst anomalies is needed for producing a realistic enso cycle first simulations are studied of a linear 1 5 layer reduced gravity ocean model and a linear sst anomaly equation forced by observed monthly wind stress if only the thermocline feedback is present in the sst equation sst can be simulated well in the eastern pacific but contrary to observations central pacific sst is out of phase with the eastern pacific if a wind stress feedback is added in the sst equation as a term proportional to the zonal wind stress correlations between observed an

multi year predictability in a coupled general circulation model multi year to decadal variability in a 100 year integration of a bmrc coupled atmosphere ocean general circulation model cgcm is examined the fractional contribution made by the decadal component generally increases with depth and latitude away from surface waters in the equatorial indo pacific ocean the relative importance of decadal variability is enhanced in off equatorial wings in the subtropical eastern pacific the model and observations exhibit enso like decadal patterns analytic results are derived which show that the patterns can in theory occur in the absence of any predictability beyond enso time scales in practice however modification to this stochastic view is needed to account for robust differences between enso like decadal patterns and their interannual counterparts an analysis of variability in the cgcm a wind forced shallow water model and a simple mixed layer model together with existing and new theoretical results are used to improve upon this stochastic paradigm and to provide a new theory for the origin of decadal enso like patterns like the interdecadal pacific oscillation and pacific decadal oscillation in this theory enso driven wind stress variability forces internal equatorially trapped kelvin waves that propagate towards the eastern boundary kelvin waves can excite reflected internal westward propagating equatorially trapped rossby waves rws and coastally trapped waves ctws ctws have no impact on the off equatorial sub surface ocean outside the coastal wave guide whereas the rws do if the frequency of the incident wave is too high then only ctws are excited at lower frequencies both ctws and rws can be excited the lower the frequency the greater the fraction of energy transmitted to rws this lowers the characteristic frequency reddens the spectrum of variability off the equator relative to its equatorial counterpart at low frequencies dissipation acts as an additional low pass filter that becomes more effective as latitude increases at the same time enso driven off equatorial surface heating anomalies drive mixed layer temperature responses in both hemispheres both the eastern boundary interactions and the accumulation of surface heat fluxes by the surface mixed layer act to low pass filter the enso forcing the resulting off equatorial variability is therefore more coherent with low pass filtered decadal enso indices e g nino3 sea surface temperature sst than with unfiltered enso indices consequently large correlations between variability and nino3 extend further poleward on decadal time scales than they do on interannual time scales this explains why decadal enso like patterns have a broader meridional structure than their interannual counterparts this difference in appearance can occur even if enso indices do not have any predictability beyond interannual time scales the wings around 15 20 s and sub surface variability at many other locations are predictable on interannual and multi year time scales this includes westward propagating internal rws within about 25 of the equator the slowest of these take up to 4 years to reach the western boundary this sub surface predictability has significant oceanographic interest however it is linked to only low levels of sst variability consequently extrapolation of delayed action oscillator theory to decadal time scales might not be justified

carbon isotope excursions in precambrian cambrian boundary beds morocco the precambrian cambrian boundary is one of the most significant points on the geological timescale because it marks the change in the fossil record from soft bodied organisms to skeletonized faunas the cambrian explosion or radiation event1 saw the evolution of many new life forms especially various molluscs and archaeocyathids from the base of the cambrian tommotian stage others including the trilobites and bivalves evolved a little later in the succeeding atdabanian stage2 3 a massive increase in the biomass of the photic zone through phytoplankton blooms has also been postulated for this time4 particularly in the late riphean early vendian and in the early cambrian5 there has been much discussion concerning where precisely to place the boundary6 7 and here are several contenders in the world for the type section8 i present here a carbon isotope profile from the precambrian cambrian boundary beds in morocco where two distinctive positive 13c excursions are revealed these are interpreted as records of increased organic productivity as part of the precambrian cambrian explosion of life 13c excursions could be useful points for correlation between boundary sections

the border of the east european craton in south eastern poland based on gravity and magnetic data according to recent geological interpretations the border of the east european craton eec in se poland is located in the ne foreland of the holy cross mts results of gravity and magnetic anomaly interpretations presented herein confirm this according to 3d and 2d gravity and magnetic modelling the eec borders the sw flank of the regional crystalline feature with increased magnetic and density properties which occur in the se part of the teisseyre tornquist zone ttz this flank rests near a deep fracture delimiting the ttz on sw the feature is a cause of the regional magnetic gradient observed there two se nw belts of residual gravity anomalies dislocations are also identified in the magnetic gradient zone cutting mesozoic and palaeozoic formations results of geophysical and geological investigations show the importance of this dislocation zone and confirm that it occurs in all crustal complexes and the upper mantle

lithospheric structure beneath trans carpathian transect from precambrian platform to pannonian basin celebration 2000 seismic profile cel05 1 in 2000 a consortium of european and north american institutions completed a huge active source seismic experiment focused on central europe the central european lithospheric experiment based on refraction or celebration 2000 this experiment primarily consisted of a network of seismic refraction profiles that extended from the east european craton along and across the trans european suture zone region in poland to the bohemian massif and through the carpathians and eastern alps to the pannonian basin the longest profile cel05 1420 km is the focus of this paper the resulting two dimensional tomographic and ray tracing models show strong variations in crustal and lower lithospheric structure clear crustal thickening from the pannonian basin 24 25 km thick to the trans european suture zone region 50 km together with the configuration of the lower lithospheric reflectors suggests northward subduction of mantle underlying carpathian pannonian plate under the european plate this however conflicts with strong geological evidence for southward subduction and we present three tectonic models that are to not totally mutually exclusive to explain the lithospheric structure of the area 1 northward old subduction of the pannonian lithosphere under the east european craton in the jurassic lower cretaceous 2 a collisional zone containing a crocodile structure where carpatho pannonian upper crust is obducting over the crystalline crust of the east european craton and the carpathian pannonian mantle lithosphere is underthrusting cratonic lower crust and 3 lithosphere thinning due to the effects of neogene extension and heating with the slab associated with young subduction southward in the miocene having been either detached and or rolled back to the east in the last case the northwestward dipping in the lithosphere can be interpreted as being due to isotherms that could represent the lithosphere asthenosphere boundary in the pannonian region

crustal seismic velocity structure of southern poland preserved memory of a pre devonian terrane accretion at the east european platform margin the updated geological and potential fields data on the east european platform margin in se poland confirm the existence of several regional units differing in ediacaran to silurian development the upper silesian block malopolska block and ysogory block all the blocks are characterized by a distinct crustal structure seen in vp velocity models obtained from the seismic refraction data of the celebration 2000 programme the first two units are interpreted as exotic terranes initially derived from avalonia type crust and ultimately accreted before the late early devonian the ysogory block is probably a proximal terrane displaced dextrally along the baltica margin the sutures between the terranes do not precisely match lateral gradients in vp models this is partly explained by a limited resolution of refraction seismic data 20 km wide interpretative window most of the difference is related however to a post accretionary tectonism mainly variscan transtension transpression the latter processes took advantage of lithospheric memory recorded earlier as zones of rheological weakness along the former suture zones the course of the east european platform margin teisseyre tornquist zone corresponds most likely to the nowe miasto zawichost fault marking the ne boundary of the proximal ysogory terrane

the deep crust beneath the trans european suture zone from a multiscale magnetic model we present a 3 d interpretation of the deep magnetic sources beneath the main geological structure of central eastern europe the trans european suture zone tesz we used a multiscale analysis of aeromagnetic data based on a multiscale data set generated by upward continuation of the european and mediterranean magnetic project data set from 5 to 100 km altitude we also computed the multiscale total gradient t of the multiscale field both of the multiscale data sets allow us to discriminate the main crustal contributions to the field at various scales and we showed that at large altitudes the field is dominated by the sole effect of the tesz the multiridge geometric method was very useful in studying the complex features of the main crustal interfaces either shallow or deep the interpreted interfaces are largely agreement with geological models based on seismic surveys and in some cases complete the models out of the analyzed region in order to estimate the deepest source depths in the tesz region we applied the multiridge method to the large scales 50 100 km altitude obtaining a set of singular points at depths ranging between 35 and 40 km considering the heat flow trend and the geological models around the tesz area we found a meaningful correspondence among the location of the estimated singular points and the most abrupt variations and complex morphology features of the moho boundary the multiridge estimates are consistent with known structural information and can be used for a 3 d representation of the moho depth along the tesz

eumetazoan fossils in terminal proterozoic phosphorites phosphatic sedimentary rocks preserve a record of early animal life different from and complementary to that provided by ediacaran fossils in terminal proterozoic sandstones and shales phosphorites of the doushantuo formation south china contain eggs egg cases and stereoblastulae that document animals of unspecified phylogenetic position small fossils containing putative spicules may specifically record the presence of sponges microfossils recently interpreted as the preserved gastrulae of cnidarian and bilaterian metazoans can alternatively be interpreted as conventional algal cysts and or egg cases modified by diagenetic processes known to have had a pervasive influence on doushantuo phosphorites regardless of this interpretation evidence for doushantuo eumetazoans is provided by millimeter scale tubes that display tabulation and apical budding characteristic of some cnidaria especially the extinct tabulates like some ediacaran remains these small benthic colonial fossils may represent stem group eumetazoans or stem group cnidarians that lived in the late proterozoic ocean

seasonal variability in the equatorial pacific abstract five to nine years of observations from the tropical atmosphere ocean array in the tropical pacific are used to document the seasonal cycle of surface winds zonal currents sst thermocline depth and dynamic height along the equator the normally westward surface zonal current reverses direction in late boreal spring and early summer this seasonal variation in the zonal surface current propagates westward as do seasonal variations in the equatorial undercurrent and zonal surface winds at the equator at 5 n and 5 s the seasonal variations in the 20 c isotherm and dynamic height also propagate westward conversely at the equator in the eastern and central pacific the variations in 20 c isotherm depth and dynamic height propagate eastward these seasonal variations are interpreted by means of a simple dynamical model based on linear equatorial wave theory model results indicate that seasonal variability between 5 n and 5 s is dominated by wind forced equatorial kelvin waves and first meridi

high δ13c carbonates from the songpan garze orogenic belt implications for correlation of neoproterozoic carbon isotope anomalies across the yangtze platform china abstract a detailed stable isotopic profile measured systematically across a thick upper neoproterozoic sinian carbonate succession at danba western yangtze platform china records an overall positive 13ccarb excursion even having experienced amphibolite facies metamorphism most of carbonates in the interior of the marble layer preserve pre metamorphic 13c and 18o values which vary with stratigraphic level the marbles can be divided into lower and upper units the lower and upper units have distinctive isotopic composition ranges 13ccarb 5 to 7 3 and 18ocarb 20 to 25 and 13ccarb 1 5 to 3 and 18ocarb 28 to 30 respectively this pattern of variation especially in 13c is similar to that reported for the unmetamorphosed upper sinian doushantuo and dengying formations in the eastern yangtze platform this suggests that the positive neoproterozoic 13ccarb excursion can be correlated on a basinal scale within the yangtze platform the data presented here establish that high 13c values of carbonates from the upper sinian doushantuo formation are a regional feature across the yangtze platform

latest proterozoic stratigraphy and earth history the end of the proterozoic eon was a time of pronounced biological biogeochemical climatic and tectonic change new bio and chemostratigraphic data provide an improved framework for stratigraphic correlation making possible a deeper understanding of latest proterozoic earth history and providing tools for a chronostratigraphic division of late proterozoic time

late neoproterozoic cap carbonates mackenzie mountains northwestern canada precipitation and global glacial meltdown the 3 27 m thick cap carbonate overlying marinoan ice brook formation glacigene sediments and keele formation carbonate and terrigenous clastic rocks consists of two distinctive stratigraphic units a lower splintery buff weathering microcrystalline dolostone of extensive lateral uniformity comprises mm laminated peloidal sediment with local low angle hummocky like cross stratification micro ridges and synsedimentary tepees all elongated per pendicular to depositional strike this dolostone is unconformably overlain by an upper limestone that exhibits pro nounced facies variation from inboard peloidal lime grainstone and mudstone to shelf edge cementstone to outboard lime wackestone and mudstone calcite cementstones range from isolated crystal fans in laminated limestone to huge decimetre scale crystal arrays to hemispherical and elongate crystal stromatolites wholly composed of acicular crystals that form decametre scale reeflike structures crystal stromatolites are precipitates and replaced microbiolites that con structed biostromes and bioherms like those on many flat topped reef rimmed platforms the calcite crystals have all the physical and chemical attributes of neomorphosed aragonite this aragonite extensively replaced sediment and microbiolite just below the sea floor and grew upward into the overlying water column such interpreted massive synsedimentary replacement is rare in geological history and attests to the highly saturated state of the immediate postglacial ocean all sediment is interpreted to have been caco3 originally low and constant 18 o values reflect diagenetic modification of these carbonates although chemical attributes such as sr and c isotopes in some lithologies are near pristine lower dolostones virtually identical to most other coeval marinoan caps worldwide were part of a global precipitation event of remarkable similarity upper limestones are a more local phenomenon deposited during sea level rise in an aragonitic sea returning to equilibrium after global glaciation low 87 sr 86 sr ratios and varying 13 c values with carbonate sedimentary facies indicate that both units must have formed relatively rapidly prior to significant flu vioglacial runoff or that the influence of this runoff on the chemistry of seawater along continental shelves was mini mal the cap carbonate is thus interpreted to have formed in two steps 1 during initial marine ice melting accompanied by oceanic overturn and upwelling preceding continental margin rebound and 2 during initial stages of sea level rise accompanying continental deglaciation while confirming brief but extensive carbonate precipitation from an ocean highly perturbed by global glaciation the rocks also suggest that this event did not permanently affect either late neoproterozoic ocean chemistry or the contained marine biosphere 1262

palaeoenvironment and carbon isotope stratigraphy of upper proterozoic carbonates of the yangtze platform the 13c values for phanerozoic marine carbonates display secular trends mainly in the range 1 to 2 1 these have been interpreted as primary features reflecting changes in the carbon isotope composition of dissolved bicarbonate in seawater brought about largely by variations in the proportions of carbon being sequestered in the oxidized and reduced carbon reservoirs1 2 carbon isotope trends are not as well established for the precambrian but there are indications that upper proterozoic sequences contain carbonates with unusually high 13c values3 9 here we present the results of the first carbon isotopic study of the upper proterozoic carbonate strata from the type locality of the sinian system in the yangtze gorges sections near yichang south china and discuss their implications for accumulation of organic matter we also compare the results for these chinese strata with 13c trends in other upper proterozoic cambrian sequences and assess the extent to which such isotopic data can be used to make stratigraphic correlations between widely spaced sequences

pb pb ages of neoproterozoic doushantuo phosphorites in south china constraints on early metazoan evolution and glaciation events the pb pb isochron ages of 576 14 ma for the upper part of the upper phosphorite bed upb this study and 599 4 ma for the lower part of the upb earth planet sci lett 201 2002 203 in the doushantuo formation in the weng an area south china suggest that the deposition of the upb lasted at least 5 ma and indicate that the observed microfossil assemblage animal remains multicellular algae and giant process bearing acritarchs in the doushantuo formation predates all well dated diverse ediacaran assemblages and represents the earlier paleontological record of eukaryotes radiation on earth the 576 14 ma age in the upper part of the upb approximates the age of a negative delta 13 c excursion near the boundary between the doushantuo and the overlying dengying formation if the doushantuo dengying boundary at the weng an area is equivalent to that in the yangtze gorges area this negative excursion might correlate to a post marinoan glaciation in south china suggesting that the ice age following doushantuo sediment deposition is younger than 590 ma the 599 4 ma age in the lower part of the upb earth planet sci lett 201 2002 203 represents the minimum age of the nantuo diamictites which are generally correlated with the marinoan glaciation c 2004 elsevier b v all rights reserved

devonian cretaceous repeated subsidence and uplift along the teisseyre tornquist zone in se poland insight from seismic data interpretation abstract the teisseyre tornquist zone that separates the east european craton from the palaeozoic platform forms one of the most fundamental lithospheric boundaries in europe devonian to cretaceous paleogene evolution of the se segment of this zone was analyzed using high quality seismic reflection data that provided detailed information regarding entire palaeozoic and mesozoic sedimentary cover with particular focus on problems of late carboniferous and late cretaceous paleogene basin inversion and uplift two previously proposed models of development and inversion of the devonian carboniferous lublin basin seem to only partly explain configuration of this sedimentary basin a new model includes late devonian early carboniferous reverse faulting within the cratonic area ne from the kock fault zone possibly first far field effect of the variscan orogeny this was followed by late carboniferous inversion of the lublin basin inversion tectonics was associated with strike slip movements along the ursynow kazimierz fault zone and thrusting along the kock fault zone possibly triggered by deeper strike slip movements late carboniferous inversion related deformations along the ne boundary of the lublin basin were associated with some degree of ductile quasi diapiric deformation facilitated by thick series of silurian shales during mesozoic extension and development of the mid polish trough major fault zones within the lublin basin remained mostly inactive and subsidence centre moved to the sw towards the nowe miasto zawichost fault zone and further to the sw into the present day holy cross mts area late cretaceous paleogene inversion of the mid polish trough and formation of the mid polish swell was associated with reactivation of inherited deeper fault zones and included also some strike slip faulting the study area provides well documented example of the foreland plate within which repeated basin inversion related to compressive transpressive deformations was triggered by active orogenic processes at the plate margin i e variscan or carpathian orogeny and involved important strike slip reactivation of crustal scale inherited fault zones belonging to the teisseyre tornquist zone

three dimensional seismic modelling of the crustal structure between east european craton and the carpathians in se poland based on celebration 2000 data summary in this paper we present results of 3 d first arrival tomography applied to data recorded in se poland during the celebration 2000 seismic experiment the target area covers ca 500 500 km 2 and represents a complex geological setting from old precambrian platform east european craton eec through the crustal blocks terranes that form the transeuropean suture zone tesz to the young alpine orogen the carpathians contrasting velocity distributions in various geological units makes the tomographic inversion challenging for this reason much attention was paid to the inversion methodology we tested multioffset and multiscale approaches by increasing the offset range in the multioffset inversion we have independently constrained different depth ranges of our model we have found that the multiscale method that is the gradual stepping from bigger to smaller model cells produced the preferred solution resolution of the resultant crustal model was determined by performing checkerboard and restoration resolution tests lateral resolution of the order of 25 km is inferred down to 10 km depth and 50 km down to 25 30 km depth we have also applied a quasi monte carlo analysis to determine the absolute errors of model parameters which to our knowledge is the first such attempt in case of a 3 d wide angle data set the mean uncertainties of our tomographic velocities are 0 1 km s 1 but some anomalies are recovered with

seismic and geological structure of the crust in the transition from baltica to palaeozoic europe in se poland celebration 2000 experiment profile cel02 abstract the celebration 2000 together with the earlier polonaise 97 deep seismic sounding experiments was aimed at the recognition of crustal structure in the border zone between the precambrian east european craton baltica and palaeozoic europe the cel02 profile of the celebration family is a 400 km long sw ne transect running in poland from the upper silesia block usb across the malopolska block mb and the trans european suture zone tesz to the east european craton eec the structure along cel02 was interpreted using both 2d tomography and forward ray tracing techniques as well as 2d gravity modelling the crustal thickness along cel02 varies from 32 35 km in the usb to 45 47 km beneath the tesz and the eec the usb is a clearly distinctive crustal block with the characteristic high velocity lower crust 7 1 7 2 km s interpreted as a fragment of gondwana the krakow lubliniec fault is a terrane boundary produced by soft docking of the usb with the mb the malopolska crust fundamentally differs from the usb and has a strong connection with baltica it is a transitional 150 to 200 km wide unit composed of the extended baltican lower crust and the overlying low velocity 5 15 5 9 km s neoproterozoic metasediments in the up to 18 km thick upper crust the ysogory unit has its crustal structure identical with that of malopolska thus it is connected with baltica and cannot be interpreted as a gondwana derived terrane higher velocity and density bodies found below the mazovia lublin graben at a depth of 12 km and at the base of the lower crust might be a result of mantle derived mafic intrusions accompanying the extension of baltica by the preliminary 2d gravity modelling we have reconfirmed the need for considering the increased tesz mantle density in comparison to the eec and usb mantle

interdecadal sea surface temperature variability in the equatorial pacific ocean part i the role of off equatorial wind stresses and oceanic rossby waves the australian bureau of meteorology research centre cgcm and a linear first baroclinic mode ocean shallow water model swm are used to investigate ocean dynamic forcing mechanisms of the equatorial pacific ocean interdecadal sea surface temperature sst variability an eof analysis of the 13 yr low pass butterworth filtered sst anomalies from a century time scale cgcm simulation reveals an sst anomaly spatial pattern and time variability consistent with the interdecadal pacific oscillation results from an swm simulation forced with wind stresses from the cgcm simulation are shown to compare well with the cgcm and as such the swm is then used to investigate the roles of uncoupled equatorial wind stress forcing off equatorial wind stress forcing offeqwf and rossby wave reflection at the western pacific ocean boundary on the decadal equatorial thermocline depth anomalies equatorial pacific wind stresses are shown to explain a large proportion of the overall variance in the equatorial thermocline depth anomalies however offeqwf beyond 12 5 latitude produces an interdecadal signature in the nino 4 nino 3 region that explains approximately 10 1 5 of the filtered control simulation variance rossby wave reflection at the western pacific boundary is shown to underpin the offeqwf contribution to these equatorial anomalies the implications of this result for the predictability of the decadal variations of thermocline depth are investigated with results showing that offeqwf generates an equatorial response in the nino 3 region up to 3 yr after the wind stress forcing is switched off further a statistically significant correlation is found between thermocline depth anomalies in the offequatorial zone and the nino 3 region with the nino 3 region lagging by approximately 2 yr the authors conclude that there is potential predictability of the offeqwf equatorial thermocline depth anomalies with lead times of up to 3 yr when taking into account the amplitudes and locations of off equatorial region rossby waves

crustal and upper mantle structure of the western carpathians from celebration 2000 profiles cel01 and cel04 seismic models and geological implications summary celebration 2000 was a large international experiment that focused on the lithospheric structure in central europe it consisted of several wide angle reflection and refraction seismic profiles profiles cel01 and cel04 are located in the transition from the precambrian and palaeozoic platforms to the carpathian orogen the data were modelled using 2 d tomographic and forward modelling techniques the profile cel01 about 900 km long extends from the southwestern margin of the east european craton to the pannonian basin system the depth of moho boundary varies along the profile from 27 33 km under the pannonian basin system area 30 39 under the carpathians and within the tesz to 40 45 km under the east european craton the cel04 profile 630 km long starts in the polish trough pt and reaches the pannonian basin system along the cel04 profile the moho interface shallows from 40 km beneath the pt to about 35 km in the maopolska unit the crustal thickness is 43 km beneath the carpathians and 25 km beneath the pannonian basin system the results obtained are consistent with a commonly accepted view of the carpathians thought to be formed largely due to the interplay between palaeogene to middle miocene subduction of oceanic or suboceanic crust and subsequent collision a feature that we interpret as the subduction related orogenic root is at least partially preserved in both profiles and is manifested by a crustal thicknesses of 39

spatial and temporal variations in carbon and sulfur isotopic compositions of sinian sedimentary rocks in the yangtze platform south china abstract eight stratigraphic sections from the yangtze platform south china were selected for a study of spatial and temporal variations in carbon and sulfur isotope compositions of sinian sedimentary rocks carbon isotope compositions of carbonate from lower sinian strata deposited between pulses of glacial diamictite range from 3 9 to 9 9 the more negative values recorded from mn carbonates suggest that in part the carbon was derived from the oxidation of organic matter during early diagenesis in the upper sinian strata 13c varies with the facies they are positive for the platform carbonates whereas they are negative from about 3 to 12 for the carbonates formed in or near basin environments it is evident that post depositional alteration accounts for the strongly negative 13c values however some information on primary isotopic compositions can be obtained by evaluating sample quality the primary 13c values of carbonates from the doushantuo formation are ca 3 to 4 and from the dengying formation as low as 6 34s values for pyrite from the lower sinian rocks are highly positive and range from values near the coeval seawater sulfate up to ca 60 in contrast 34s values for pyrite from the upper sinina rocks are negative down to 27 to 30 the feature of sulfur isotopic composition for the lower sinian rocks is consistent with the late proterozoic sulfur isotopic record it might be explained by the supercontinent model many basins on the yangtze block in a supercontinent tectonic background had limited or no access to the open ocean and the basin waters contained sulfate with considerably higher 34s values than the coeval seawater for a geologically long period an alternative explanation is based on the sulfate minimum zone smz modal because of the slow sinking of organic matter bacterial sulfate reduction would be important in the lower sinian shallow water environment particularly in the smz the residual sulfate might have been significantly enriched in 34s so that pyrite produced in closed diagenetic system would yield very positive 34s values

new lu hf and pb pb age constraints on the earliest animal fossils abstract the neoproterozoic doushantuo formation south china preserves a unique assemblage of early multicellular fossils and overlies rocks which are thought to have formed during an ice age of global extent the age of this formation is thus critical for understanding the important biological and climatic events that occurred towards the end of the proterozoic eon until now direct dating of sedimentary formations such as the doushantuo has been difficult and associated with large uncertainties here we show that dating of doushantuo phosphorites by a novel lu hf dating method and conventional pb pb geochronometry independently yield ages of 584 26 ma and 599 3 4 2 ma respectively these ages are in agreement with bio and chemostratigraphical observations and show that the doushantuo animal remains predate diverse ediacaran fossil assemblages making them the oldest unambiguous remains of metazoans currently known furthermore the pb pb age for the post glacial doushantuo rocks suggests that the neoproterozoic glaciation in china might predate glacial rocks in eastern north america commonly associated with the younger marinoan of two major neoproterozoic glaciations the combination of lu hf and pb pb dating shows considerable potential for dating other phosphorite successions and future application of these methods could therefore provide further constraints on proterozoic biological and environmental history