environmental evolution during the late jurassic at lavarone trento plateau italy abstract four sections have been studied in the monte rust area lavarone northern italy for the interpretation of depositional conditions the biostratigraphic subdivision is based on more than 1400 stratigraphically controlled ammonite specimens which enabled the recognition of five biozones in the kimmeridgian and three in the lower tithonian three basic lithofacies are identified in the upper unit of the rosso ammonitico veronese nodular marly nodular calcareous and pseudonodular calcareous massive which developed according to relative sea level conditions the depositional dynamics were closely related to increasing energy and winnowing during sea level lows nodular calcareous ammonitico rosso and the opposite during sea level highs nodular marly ammonitico rosso the highest energy conditions are assumed for the pseudonodular calcareous massive ammonitico rosso revealing a probable interaction between tectonics and eustasy and an increased mean rate of carbonate sedimentation the cluster analysis of selected components of microfacies shows only minor fluctuations in a low energy environment and thus a rather variable relationship between micro and macrofeatures in the ammonitico rosso facies studied the correlation analysis between relative abundances of selected variables components in the cluster analysis has proven useful in interpreting fluctuations in energy conditions for the kimmeridgian deposits formed during sea level highs uhlandi and beckeri chrons are especially well correlated in the area as well as elsewhere in the western tethys the progressive long term sea level fall during the early tithonian does not diminish the possibility for correlation in the epioceanic area studied

faunal response to transgressive regressive cycles example from the jurassic of western india abstract upper callovian to oxfordian shelf sediments at ler in the kachchh basin western india are interpreted in terms of transgressive regressive cycles the transgressive phases are represented by thin layers of reworked and bored concretions sometimes in association with skeletal concentrations the regressive phases are documented by much thicker units of largely fine grained sediments the benthic fauna of transgressive and regressive phases differes markedly and thus mirrors the sedimentary cycles during transgressive phases non sedimentation produced hard substrates colonized mainly by byssate cemented or pedicle attached suspension feeding epifaunal species whilst sediment input during regressive phases lead to soft substrate conditions characterized by infaunal deposit and suspension feeders as well as by epifaunal opportunists whereas the composition of the regressive fauna remains fairly constant through time that of successive transgressive faunas often differs drastically this is possibly due to a greater environmental sensitivity of epifaunal taxa as compared to infaunal taxa

ecostratigraphy and sequence stratigraphy in high frequency sea level fluctuations examples from jurassic macroinvertebrate assemblages abstract sequence stratigraphy is a method for stratigraphic analysis providing interpretative models with the aim of integrating the subsurface and surface information for correlations and therefore biostratigraphical data has become increasingly valuable in this context given the foregoing unsolved problems still arise out of the difficulty in obtaining local biostratigraphical data which can certainly be related to the fact that the linkages of contemporaneous depositional systems are facies independent and also because of the comparatively broad time span accepted for the cycles of high frequency sea level fluctuations 3rd order and lesser ones other restrictions have to do with the comparative complexity of ancient e g mesozoic platform systems whose extent and subdivision lead to deviations in the stratal patterns as regards those proposed by the existing synthetic models of sequence stratigraphy moreover at present the attempts at correlation of data obtained in ancient platforms with those from distal areas of continental margins which are normally characterized by low sedimentation rates are made indirectly oloriz et al 1991 and are still at a comparatively early stage of development we here propose an ecostratigraphical approach for correlation and characterization of system tracts in the context of high resolution stratigraphy the interpretation of the geological record must of course be undertaken with regard to recognizable local determining factors the observable trends in the record of benthic epibenthic marine macroinvertebrate assemblages are analyzed in this context examples of the upper jurassic ammonite record and especially bivalves among benthic faunas are analyzed on the south and west iberian margins using the sequence stratigraphy frame proposed for this margin by marques et al 1991 the data obtained are compatible with the contraction expansion of ecospaces which could presumably be related to the evolution of highstand transgressive and shelf margin wedge system tracts we also comment on published data by others authors concerning fluctuations in ammonite assemblages and ammonite phenotypes chronological aspects related with sequences stratigraphy analyses and the record of benthic assemblages within the framework of high frequency fluctuations in relative sea level the approach proposed here proves to be a useful complement in sequence stratigraphy analyses and will also be of use in more profound study of the ecostratigraphic characterization of system tracts and new interpretations of the fossil record

stratigraphic sequences and their chronostratigraphic correlation abstract the exxon sequence models of posamentier and coworkers incorporate two concepts which i question they suggest that rivers grade to a bayline but evidence from modern major rivers indicates that they do not they also proposed that fluvial sedimentary accomodation space is generated by the seaward shift in equilibrium profiles during sea level fall but this is too simplistic a model based on the use of schematic continental margin configurations which do not incorporate real slope and relief data in most cases a fall in base level leads to deltaic progradation and upstream fluvial incision most coastal plain fluvial wedges result from two processes sea level rise with the drowning and filling of estuaries and active source area tectonism major tectonic events adjacent to foreland basins such as terrane collisions lead to the development of sequences of third order type duration approximately 1 15 m y changes in intraplate stress regimes resulting from changes in regional plate kinematics have a similar episodicity and can be shown to be responsible for some third order cycles on extensional continental margins examination of the chronostratigraphic basis of the mesozoic cenozoic cycle chart of haq and coworkers reveals internal inconsistencies and an unrealistic downplaying of the built in potential for error this chart is not an approved global standard and it should be used with extreme caution

concepts and methods of high resolution event stratigraphy modern geological analyses involving sedimentary rocks require a high resolution system of dating integrating and correlating diverse strati graphic geochemical and paleontological data that also takes into account the possibility that short term phenomena 100 kyr or less exercise a strong control on sedimentation such phenomena may be extraterrestrial tectonic volcanic oceanographic climatic sedimentologic and or bio logic in origin some reflect unpredictable perturbations of local to global scale but most short term phenomena are predictable and may be either autocyclic locally regulated with limited stratigraphic continuity or allo cyclic in nature regionally to globally regulated with extensive strati graphic continuity beerbower 1964 a stratigraphic system based on short term phenomena would ideally be chronostratigraphic involving the identification and regional tracing of time lines isochronous surfaces or very thin event deposits and easily integrated with refined independently derived biostratigraphic and geochronologic systems an intensive search for such a new and revolutionary system of stratig raphy has been prompted in many parts of the phanerozoic by attain ment of plateaus in stratigraphic resolution utilizing the more standard tools of magnetostratigraphy biostratigraphy and geochronology most magnetic reversals have been identified biostratigraphic systems can be no more refined than the maximum evolutionary rates of component taxa and their major structures known for many favored groups and geo chronology is regulated by the analytical confidence limits of radiometric

spatial geochemistry of upper jurassic marine carbonates iberian subplate abstract chemostratigraphy applied to ancient marine carbonates is commonly based on one dimensional stratigraphic sections or core data as demonstrated from modern oceans this approach underestimates the spatial complexity of physico chemical seawater properties here a several hundred kilometer long transect consisting of seven upper jurassic sections from settings ranging from proximal neritic middle shelf to the epioceanic distal fringe across the southern and eastern palaeomargins of the iberian sub plate reveals variability in sedimentologic stratigraphic and geochemical records the comparison of isotopic and elemental data from different carbonate materials matrix micrite carbonate cements in veinlets belemnite rostra and ammonite shells reveals differential diagenetic pathways microfacies cathodoluminescence and geochemical data retrieved from biostratigraphically well constrained sections reveal that epioceanic matrix micrite geochemical data provide valuable proxies for palaeo seawater properties our data are reviewed in the context of published late jurassic records the outcome shows a higher level of complexity including the potential admixture of marine continental and diagenetic geochemical signals in the epicontinental record the stratigraphic trend in carbon isotopes of epioceanic sections agrees upon that of upper jurassic reference sections from the northern tethyan margins while oxygen isotope ratios are relatively 18o enriched palaeo seawater temperatures across the transect investigated were estimated using 18o as tentative proxy for interpreting distance from shore differences in water masses relative depth variations and potential local forcing factors palaeoenvironmental conditions evaluated through the combined record of isotope 18o elemental mn and skeletal content contrast with relative fluctuations in sea level site specific changes in palaeoceanographic parameters such as water depth seawater temperature salinity and upwelling are considered in comparison to examples from ancient and modern oceans

ecostratigraphic approaches sequence stratigraphy proposals and block tectonics examples from epioceanic swell areas in south and east iberia abstract an ecostratigraphic approach is proposed here as a supplementary tool to sequence stratigraphic interpretations mainly based on lithology as a case study six sections were selected with condensed ammonitico rosso facies of early tithonian age albertinum darwini chron within an epioceanic fringe this fringe clearly differs in its ecologic sedimentary and tectonic frameworks from better documented epicontinental environments in the studied sections short distance differences vs long distance similarities have been evaluated by comparing features of macro and microfacies in the ammonitico rosso facies and by the analyses of 1239 megainvertebrates which were recorded bed by bed sixteen average faunal spectra containing anywhere from 50 to 150 specimens were analyzed the ecostratigraphic interpretation is made by considering the ammonites other megainvertebrates ratio the assumed ecology and taphonomy for selected ammonite groups the depositional dynamics and proposed short term sea level changes and local tectonics the trends observed in the composition of megainvertebrate faunal spectra are explained by ecospace changes caused by eustasy shared trends in long distance correlations and by relative sea level changes due to the combined action between tectonics and eustasy counteractive trends in short distance correlations

early cretaceous pre aptian ammonites of the mediterranean tethys palaeoecology and palaeobiogeography abstract this study focuses on late valanginian and barremian ammonite assemblages of the mediterranean tethys their palaeobiogeographic distribution shows that the faunal composition is ecologically controlled shelf assemblages differ from those reported from epioceanic areas the number of families regarded as major morphologic types increases during the early cretaceous reaching a peak in the late barremian opportunistic strategy has been suggested for some taxa leptoceratoidinae bochianitidae the increased diversification of the ammonite faunas from valanginian to barremian reflects an increase of the number of niches possibly the progressive radiation and adaptation to different distal marine environments is the result of a more and more specialized use of food resources a possible link between the trophic opportunities which developed as a consequence of the late tithonian nannoconid bloom and the evolution of the ammonites living mainly on the shelf margins and distal epioceanic environments cannot be disregarded to explain some ammonoid evolutionary events during the early cretaceous

coupled model simulations of boreal summer intraseasonal 30 50 day variability part 1 systematic errors and caution on use of metrics boreal summer intraseasonal 30 50 day variability bsisv over the asian monsoon region is more complex than its boreal winter counterpart the madden julian oscillation mjo since it also exhibits northward and northwestward propagating convective components near india and over the west pacific here we analyze the bsisv in the cmip3 and two cmip2 coupled ocean atmosphere models though most models exhibit eastward propagation of convective anomalies over the indian ocean difficulty remains in simulating the life cycle of the bsisv as few represent its eastward extension into the western central pacific as such few models produce statistically significant anomalies that comprise the northwest to southeast tilted convection which results from the forced rossby waves that are excited by the near equatorial convective anomalies our results indicate that it is a necessary but not sufficient condition that the locations the time mean monsoon heat sources and the easterly wind shear be simulated correctly in order for the life cycle of the bsisv to be represented realistically extreme caution is needed when using metrics such as the pattern correlation for assessing the fidelity of model performance as models with the most physically realistic bsisv do not necessarily exhibit the highest pattern correlations with observations furthermore diagnostic latitude time plots to evaluate the northward propagation of convection from the equator to india and the bay of bengal also need to be used with caution here incorrectly representing extratropical tropical interactions can give rise to apparent northward propagation when none exists in association with the eastward propagating equatorial convection despite these cautions the use of multiple cross checking diagnostics enables the fidelity of the simulation of the bsisv to be meaningfully assessed

organization of tropical convection in a gcm with varying vertical resolution implications for the simulation of the madden julian oscillation experiments using a gcm with two different vertical resolutions show differences in the amount of variability in the tropical upper tropospheric zonal wind component associated with the madden julian oscillation mjo the gcm with lower vertical resolution shows very little variability in this quantity whereas when the vertical resolution is doubled in the free troposphere the gcm produces variability which is of the same strength as observations however the eastward propagation of an enhanced convective region from the indian ocean into the west pacific is not well represented in either simulation of this atmospheric gcm a water covered or aqua planet version of the same gcm is used to investigate the behaviour of tropical convection when the vertical resolution is doubled when the vertical resolution is increased the spectrum of tropical cloud types changes from a bimodal distribution with peaks representing shallow cumulus and deep cumulonimbus clouds to a trimodal distribution with a third peak in mid troposphere near the melting level associated with periods when these mid level congestus clouds are dominant the detrainment from these clouds significantly moistens the mid troposphere the appearance of these congestus clouds is shown to be partly due to improved resolution of the freezing level and the convective processes occurring at this level however due to the way in which convective detrainment is parametrized in this model the vertical profile becomes rather noisy and this too contributes to the change in the nature of the convective clouds the resulting cloud distribution more closely resembles observations particularly during the suppressed phase of the mjo when cumulus congestus is the dominant cloud type

simulation of the observed evening transition and nocturnal boundary layers large eddy simulation large eddy simulations are performed of two observed cases of evening transition boundary layers over land although generally similar to the observations the simulations have a poor match to the ageostrophic wind above the boundary layer and overestimate the nocturnal 4 m wind speed for one case the nocturnal phase is also simulated using a close match to observations in the early evening reproducing well the early morning boundary layer and jet this is achieved with a moderate resolution 5 m and also demonstrates the importance of a good initial wind state in a numerical weather prediction context these findings motivate improved wind profile observations around transition and a better representation of the ageostrophic wind by the boundary layer parametrization copyright 2006 crown copyright

tropical intraseasonal variability in the mri 20km60l agcm this study documents the detailed characteristics of the tropical intraseasonal variability tisv in the mri 20km60l agcm that uses a variant of the arakawa schubert cumulus parameterization mean states power spectra propagation features leading eof modes horizontal and vertical structures and seasonality associated with the tisv are analyzed results show that the model reproduces the mean states in winds realistically and in convection comparable to that of the observations however the simulated tisv is less realistic it shows low amplitudes in convection and low level winds in the 30 60 day band filtered anomalies have standing structures power spectra and lag correlation of the signals do not propagate dominantly either in the eastward direction during boreal winter or in the northward direction during boreal summer a combined eof ceof analysis shows that winds and convection have a loose coupling that cannot sustain the simulated tisv as realistically as that observed in the composited mature phase of the simulated mjo the low level convergence does not lead convection clearly so that the moisture anomalies do not tilt westward in the vertical indicating that the low level convergence does not favor the eastward propagation the less realistic tisv suggests that the representation of cumulus convection needs to be improved in this model

sequence stratigraphy of the jurassic new data from the paris london basin compiled on well logs a sequence stratigraphic analysis of the jurassic sedimentary succession in paris basin is derived from an integration of subsurface log correlations field observations and reinterpretations of field descriptions the analysis is presented on two log sections one crossing the basin from northeast to southwest and the other from northwest to southeast approximately 80 logs a vast quantity of field data collected all around the parsi basin english dorset french normandy manche ardennes lorraine bourgogne allowed the sequences and system tracts boundaries to be traced and dated at the same time or prior to being recognized on well log data in comparison with the haq et al 1987 cycle chart 16 new sequences have been added three for the lias seven for the dogger and six for the malm occasionally ages of some of the already recognized sequences boundaries have been slightly modified to fit new biostratal data these biostratal data were usually at the scale of the ammonite sub zone and the actual give ages all tie with the 1987 haq et al chart time scale

simulation of the madden julian oscillation in the ncar ccm3 using a revised zhang mcfarlane convection parameterization scheme abstract this study presents the simulation of the madden julian oscillation mjo in the ncar ccm3 using a modified zhang mcfarlane convection parameterization scheme it is shown that with the modified scheme the intraseasonal 20 80 day variability in precipitation zonal wind and outgoing longwave radiation olr is enhanced substantially compared to the standard ccm3 simulation using a composite technique based on the empirical orthogonal function eof analysis the paper demonstrates that the simulated mjos are in better agreement with the observations than the standard model in many important aspects the amplitudes of the mjos in 850 mb zonal wind precipitation and olr are comparable to those of the observations and the mjos show clearly eastward propagation from the indian ocean to the pacific in contrast the simulated mjos in the standard ccm3 simulation are weak and have a tendency to propagate westward in the indian ocean nevertheless there remain several deficiencies that are yet

postmortem transport and resedimentation of foraminiferal tests relations to cyclical changes of foraminiferal assemblages abstract cyclical changes in microfossil mainly foraminiferal assemblages were analysed for sixteen boreholes from three stratigraphical levels in the lower and middle miocene of the central paratethys the following characteristics of assemblages were quantified and used for interpretation of cyclical changes in assemblages 1 abundance of foraminifers calcareous nannoplankton sponge spicules and diatoms 2 similarity diversity and epifauna infauna ratio of benthonic foraminiferal assemblages 3 planktic benthic ratio of foraminiferal assemblages the palaeoecology mainly palaeobathymetry fluctuations were interpreted from the species composition of assemblages values of the mentioned quantitative characteristics as well as palaeoecological interpretations may be influenced by postmortem transport and resedimentation of foraminiferal tests therefore prior to the interpretation of cyclical changes of quantitative characteristics the studied sections were classified on the basis of the intensity of taphonomical changes in foraminiferal assemblages three different categories of sections were obtained for every category those quantitative characteristics of foraminiferal assemblages were chosen which reflect cyclical changes most efficiently 1 cyclical changes of abundance of foraminifers calcareous nannoplankton and sponge spicules as well as the fluctuations in palaeobathymetry for sections dominated by indigenous foraminifers 2 percentage of indigenous suspension transported bedload transported and reworked foraminiferal tests and changes in the abundance of indigenous tests for sections dominated by transported tests 3 different modes of test preservation used for the identification of a cycle boundary for sections with only transported or reworked tests the distinguished cycles were interpreted predominantly as manifestations of relative sea level changes if comparable data exist from other paratethys regions the determined cycles can be correlated with the other basins

development characteristics and dynamic structure of tropical intraseasonal convection anomalies abstract the development and dynamical structure of intraseasonal low frequency convection anomalies in the equatorial region are investigated using 10 years 1975 85 of outgoing longwave radiation olr and 7 years 1979 85 of 200 and 850 mb wind data the composite olr anomalies for 36 cases show a four stage development process initiation over equatorial africa rapid intensification when passing through the indian ocean mature evolution characterized by a weakening in the maritime continent and redevelopment over the western pacific and dissipation near the date line in moderate events or emanation from the equator toward north america and southeastern pacific in strong events a noticeable feature in vertical structure is that the 850 mb convergence leads convection and midtropospheric upward motion by about 30 degrees longitude in both developing and mature phases equatorial upper lower level easterly westerly anomalies and associated twin anomalous anticyclonic cyclonic circulation an

the boreal summer intraseasonal oscillation relationship between northward and eastward movement of convection the summertime intraseasonal oscillation iso is an important component of the south asian monsoon lagged regressions of intraseasonally filtered 25 80 days outgoing longwave radiation olr reveal that centers of convection move both northward and eastward from the central equatorial indian ocean subsequent to the initiation of an iso eastward movement of convection is also seen at indian subcontinent latitudes 10 8 208n based on the regression results the summertime iso convection signal appears as a band tilting northwestward with latitude and stretching from the equator to about 208n viewed along any meridian convection appears to propagate northward while equatorial convection propagates to the east to examine the robustness of the connection between eastward and northward movement individual isos are categorized and composited relative to the strength of the large scale eastward component of convection in the central equatorial indian ocean it is found that the majority of isos that exhibit northward movement onto the indian subcontinent 42 out of 54 isos or 78 also exhibit eastward movement into the western pacific ocean it is also found that when convection in the central indian ocean is not followed within 10 20 days by convection in the western pacific ocean 12 out of 54 isos or 22 the independent northward movement of convection in the indian ocean region is somewhat stunted the link between the eastward and northward movement of convection is consistent with an interpretation of the summertime iso in terms of propagating equatorial modes the northward moving portion of convection is forced by surface frictional convergence into the low pressure center of the rossby cell that is excited by equatorial iso convection a similar convergence pattern is seen for the northern winter iso but it does not generate poleward movement due to relatively cool ssts underlying the surface convergence

high resolution simulation of mean convection and its intraseasonal variability over the tropics in the mri jma 20 km mesh agcm abstract tropical mean convection and its organization on different spatiotemporal scales in a simulation using the meteorological research institute japan meteorological agency mri jma global atmospheric general circulation model agcm at 20 km resolution tl959l60 has been investigated comparison with two lower resolution simulations of 120 km tl159l40 and 180 km tl95l40 shows that convection climatological fields and moist stability over the indian ocean and south pacific convergence zone are better represented in tl959l60 than in lower resolution simulations however the simulated three dimensional structure of the walker and hadley cells and the vertical structure of convective heating do not show marked improvement relative to lower resolution simulations the amplitude and phase speed of convectively coupled equatorial waves show that although the kelvin waves the observed hierarchical structure of cloud clusters associated with the madden julian oscillation mjo convection and th

approaching trophic structure in late jurassic neritic shelves a western tethys example from southern iberia the palaeoenvironmental conditions and trophic structure of a mid outer neritic biota microfossils mainly forams and macroinvertebrate assemblages have been approached in middle oxfordian lowermost kimmeridgian deposits from the prebetic zone betic cordillera in south eastern spain according to relationships between fossil assemblages and lithofacies a general seaward trend is identified which displays decreasing sedimentation rates and nutrient inputs but increasing substrate consistency and presumably depth midshelf terrigenous rich deposits in the external prebetic relate to the highest sedimentation rates and nutrient availability these two parameters correlate with the highest content in vagile benthic calcareous perforate epifaunal forams as well as with potentially deep infaunal forams and infaunal macroinvertebrates outer shelf lumpy deposits in the internal prebetic show the lowest sedimentation rates and nutrient availability and the highest records for macro micro nektonics and planktics in contrast vagile benthic calcareous perforate epifaunal and potentially deep infaunal forams are scarcer in the midshelf environments colonial encrusting forams benthic microbial communities and sessile benthic macro invertebrates increase from the middle to outer shelf trophic analysis structuring through the integration of benthic microbial communities foraminiferal and macroinvertebrate fossil assemblages makes it possible to interpret a a trophic level frame composed of producers and primary and secondary consumers b a main trophic group differentiation in suspension feeders detritus feeders browsers grazers carnivores and scavengers c a preliminary approach to food chain structure supported by suspension feeders deposit feeders and predators active prey selection carnivores and d a food pyramid model which takes into account both recorded fossils and envisaged i e ecologically inferred organisms

fossil assemblages lithofacies taphofacies and interpreting depositional dynamics in the epicontinental oxfordian of the prebetic zone betic cordillera southern spain abstract the study of six sections within the external prebetic pozo canada fuente alamo chinchilla de montearagon and riogazas chorro ii and the internal prebetic navalperal and rio segura comprises the first results of a taphonomic study to be incorporated into the ecostratigraphic interpretation of the oxfordian in the prebetic zone betic cordillera southern spain a taphonomic analysis was made of 9350 specimens including fragments of macroinvertebrate fossils ammonoids 64 benthic organisms 26 and belemnoids and nautiloids 10 the taphonomic features analysed were a state of preservation ratio of moulds with without shell and type of mould filling b fossil size c position within the bed d corrasion see brett c e baird g c palaios 1 1986 207 227 e fragmentation f epibionts and encrustment g disarticulation h uncoupling and i deformation analysis of the relative significance of these features and their relation to the lithofacies allows us to characterise and distinguish three major taphofacies a taphofacies i characterised by the greater average size of the specimens recorded higher values of corrasion encrustation and colonisation and by the fact that a high proportion of the specimens are in a quasi horizontal position b taphofacies ii characterised by a higher proportion of smaller specimens and a greater variety of azimuthal orientation although the quasi horizontal position is always predominant and corrasion values are low c taphofacies iii with predominantly small specimens the highest proportion of quasi horizontal orientation and fragmentation and no evidence of corrasion the taphofacies are stratigraphically and palaeogeographically distributed in interpreting the taphofacies the exposure time of skeletals is an essential parameter and is related to the controlling effect of the sedimentation rate this latter depends on factors such as the tectonic eustatic dynamics the relative distance from the shore and the bottom physiography