environmental factors controlling the δ13c and δ18o variations of recent fluvial tufas a 12 year record from the monasterio de piedra natural park ne iberian peninsula abstract a 12 year study 2000 2012 of the stable isotopes of recent fluvial tufas has been performed in the monasterio de piedra natural park river piedra ne iberian peninsula an area of mediterranean climate with intense tufa deposition since the pleistocene the biannual monitoring of the tufa calcite 13c and 18o signatures and of the water 18o value has demonstrated a clear seasonal pattern for the tufa calcite oxygen isotope composition with less negative values for cool periods which is consistent with regional temperature oscillations the tufa calcite 13c values only occasionally exhibit a pattern which is inconclusive and opposite to the 18o clear pattern the water 18o signature has a distinct seasonal pattern also opposite to the tufa calcite 18o clear pattern the temperature calculations from the tufa calcite 18o values and average water 18o values agree with the seasonal pattern of measured water temperatures with a mean difference of 2 3 c between the calculated and measured temperatures the anomalous values recorded for both the water and the tufa calcite oxygen isotope composition during a two year period are characterized by smoothing of the seasonal variations of the tufa calcite and by reversal of the water pattern there is also an increase in the differences between the measured and estimated temperatures the detected anomaly is roughly synchronous with a change in the isotopic signature of the regional precipitation 18o values this contribution demonstrates that tufas in this depositional and climatic context are good indicators of seasonal temperature oscillations and that tufas can also record other interannual environmental changes such as variations in the isotopic composition of precipitation these results can be extrapolated to ancient tufa systems developed in similar contexts which would expand the potential of tufas as high resolution records of paleoenvironmental conditions

microbial processes forming daily lamination in a stromatolitic travertine abstract thirty hour continuous observation revealed that cyanobacterial metabolism caused daily lamination of a stromatolitic travertine in the shionoha hot spring sw japan the travertine is mainly composed of dendritic calcite crystals intercalated with bands of micritic particles at sub millimeter intervals cyanobacteria remained in the spaces between the calcite crystals during the daytime rose to the travertine surface to receive illumination as light decreased and formed a biofilm around sunset a micritic band developed on the biofilm where glutinous substances trapped detrital ferrihydrite rich particles transported from upcurrent the trapped particles covered the biofilm and in situ precipitation of calcite crystals became dominant before mid night the depositional model of daily lamination of the shionoha travertine may provide insight into the poorly understood origins and depositional rate of ancient stromatolites

carbon dioxide reaction processes in a model brine aquifer at 200 c and 200 bars implications for geologic sequestration of carbon the reactive behavior of supercritical co2 under conditions relevant to geologic storage and sequestration of c is largely unknown experiments were conducted in a flexible cell hydrothermal apparatus to determine the extent of fluid rock reactions in addition to carbonate mineral precipitation that may occur in a brine aquifer aquitard system that simulates a saline aquifer storage scenario the system was held at 200 c and 200 bars for 59 days 1413 h to approach steady state then injected with co2 and allowed to react for another 80 days 1924 h in addition to magnesite precipitation silicate minerals quartz plagioclase microcline and biotite in the aquifer and the aquitard display textures etch pits mineralization indicating significant reaction changes in elemental abundances in the brine following addition of co2 include ph decrease and enrichment in cl partly due to supercritical co2 desiccation of the brine geologic sequestration systems have potential for geochemical reactions that extend beyond simple aqueous dissolution of co2 and precipitation of carbonate these reactions may produce geochemical and geotechnical consequences for sequestration and provide important characteristics for monitoring and evaluation of stored co2 a n understanding of multi phase equilibrium relationships between supercritical co2 and aquifer brine systems also raises new questions for a variety of geologic systems multi phase fluid equilibria may for example account for the large amounts and heterogeneous distributions of calcite cement in a wide variety of geologic systems particularly in sedimentary basin sandstones published by elsevier science ltd

impact of global climate in the diversity patterns of middle miocene rodents from the madrid basin spain abstract remarkable palaeoclimatic global changes have been recorded worldwide during the middle miocene the miocene climatic optimum 16 3 to 15 ma one of the warmest phases since the eocene was followed by the stepwise cooling trend of the middle miocene climate transition 15 to 13 7 ma the entry into an earth ice house climate state took place at the end of the latter 13 76 ma marked by one of the major cooling steps in middle miocene climate recorded at a global scale mi3b event the madrid basin which is part of one of the main cenozoic basins of the iberian peninsula contains a well represented small mammal record from the lower middle miocene to the upper middle miocene middle and upper aragonian 15 9 to 12 8 ma being an appropriate region to check how these climatic phases influenced the distribution of the mammalian faunas on the center of the iberian peninsula values of species richness equitability and heterogeneity of rodents have been calculated for 25 localities of the madrid basin and compared to detailed climate isotope records from the marine realm odp site 1146 from the south china sea and the mediterranean record of the ras il pellegrin section on the maltese islands and with palaeoprecipitation curves for southwest europe calatayud montalban basin the results show that the rodent community during the middle and upper aragonian in the madrid basin was subject to the changing climate conditions imposed in the course of the middle miocene the palaeoecological curves witness periods of disturbance of the community during changing climate conditions marked by important drops in equitability and in some cases gradual decreases in heterogeneity and species richness followed by periods showing a recovery of the community and adaptation to the new climate circumstances represented by more evenly distributed and diverse assemblages the effects of the miocene climate optimum and of three mi events mi2b mi3a and mi3b have been related to changes in the small mammal community between 15 8 and 15 3 ma the likely extreme environment high temperature and low precipitation of part of the miocene climate optimum may have imposed severe constraints on the fauna resulting in a community with low values of equitability heterogeneity and a decreasing number of species the transition of the miocene climate optimum to the middle miocene climate transition reflected by the mi2b event has also procured a destabilization of the rodent assemblages as an important drop in equitability is recorded between 15 and 14 6 ma in this interval the drop in temperature and increase in rainfall derived from the middle miocene climate transition promote the southwards migration of northern invaders leading to an increase in species richness in the madrid basin starting around 14 4 ma the onset of a progressive drop in the rodent equitability and heterogeneity which also coincides with a major stratigraphic discordance in the basin is related to the first cooling step of the middle miocene climate transition mi3a event finally the major cooling step in middle miocene climate recorded at a global scale mi3b event is poorly reflected in the palaeoecological curves however the taxonomical study of the rodent faunas of that interval biozone e has shown turnover rates and morphometric changes that indicate that this period represents one of the most variable in assemblage composition within the aragonian although the mi3b event has been correlated for a long time to the substitution of the early middle aragonian fauna by a late aragonian community e f boundary the study of the rodent assemblages of the madrid basin may point out that small changes in the small mammal community started before within biozone e

clinoforms and clinoform systems review and dynamic classification scheme for shorelines subaqueous deltas shelf edges and continental margins abstract clinoforms are inclined and normally basinward dipping horizons developed over a range of spatial and temporal scales in both siliciclastic and carbonatic systems the study of clinoform successions underpins sequence stratigraphy and all efforts to reconstruct the relative partitioning of reservoir seal and source rocks along shoreline to basin floor profiles here we review clinoform research and propose a more systematic description and classification of clinoforms this is a crucial step to improve predictions of facies and lithology distribution within shoreline to continental shelf and abyssal plain successions together with the genesis drivers and dynamics of their constituent sedimentary units four basic clinoform types are here distinguished in delta shorelines lacustrine and marine environments on the basis of their overall spatial and temporal scale morphology outbuilding dynamic and geodynamic and depositional setting 1 2 delta scale clinoforms which in turns are sub divided into shoreline and delta scale subaqueous clinoforms 3 shelf edge clinoforms and 4 continental margin clinoforms delta scale clinoform sets are tens of metres high and typically represent 1 103 kyr with progradation rates ranging from 1 000 100 000 m kyr for shorelines and subaerial deltas to 100 20 000 m kyr for subaqueous deltas shelf edge clinoform sets are hundreds of metres high and are nucleated and accreted in 0 1 20 myr usual progradation rates of 1 100 m kyr by successive cross shelf transits of delta scale clinoforms continental margin clinoform sets are thousands of metres high hallmark key geodynamic crustal boundaries e g continent ocean transition and slowly prograde basinwards in ca 5 100 myr with typical rates of 0 1 10 m kyr as a consequence of the very different progradation rates and of the difficulty of large scale clinothems to backstep during transgressions shorelines are the most dynamic clinoforms with regards to position continental margins the least and shelf edges are intermediate shortly after a transgression therefore the four clinoform types may prograde synchronously along shoreline to abyssal plain transects forming compound clinoform systems during the subsequent regressive cycle however due to the dissimilarity in progradation rates different clinoform types will normally merge progressively with each other giving rise to hybrid clinoforms e g shelf edge deltas and fewer depositional breaks in slope are distinguished along a single shoreline to abyssal plain transect overall all clinoform systems are the result of the dynamic evolution of compound and hybrid clinoforms along a temporal and spatial continuum regulated by the cyclical backstepping of the smaller scale system within natural progradational retrogradational cycles of larger scale clinothem outbuilding all clinothem types may show either an accretionary active or draping passive style depending on the proximity to the sediment source draping clinothems are nearly always composed of condensed fine grained sediments while actively accreting clinothems can be composed of predominantly coarse grained i e reservoir forming or predominantly fine grained i e non reservoir lithotypes a novel hierarchical classification scheme for both recent and ancient clinoforms is here proposed consisting of 12 classes the four basic clinoform types delta scale shoreline delta scale subaqueous shelf edge and continental margin are sub divided into eight accretionary active and draping passive sub types 8 division each accretionary sub type is then sub divided into a sandstone prone and mudstone prone variant 12 division which can be at least tentatively predicted on the basis of the clinoform morphology even in the absence of direct stratigraphic logs

compositional variations in calciturbidites due to sea level fluctuations late quaternary bahamas piston cores in tongue of the ocean bahamas revealed an alternating sequence of periplatform ooze and bankderived turbidites of the past 5 glacial and interglacial periods by using the point count method we have analyzed the composition of the turbidite sediment variations in the bank derived fraction are clearly linked to the glacial interglacial cycles nonskeletal components pellets ooids grapestones are most abundant in interglacial turbidites while skeletal components calcareous algae peneroplids and reef builders dominate in glacial turbidites we attribute this pattern to the exposure and flooding of the surrounding carbonate platforms during late quaternary sea level cycles because nonskeletal sediment is produced in the interior of the platforms its growth and subsequent export to the flanks are at a maximum when the banks are flooded i e during interglacial periods during glacials skeletal grains dominate because the banks are exposed and carbonate production is limited to a narrow belt of skeletal sands and fringing reefs the resulting compositional signal appeared to have a good correlation with aragonite variations in the periplatform ooze between the turbidites further compositional variation parallels the change in turbidite frequency described earlier highstand bundling frequency and composition of turbidites are both unaffected by diagenesis and therefore provide an excellent monitor of sealevel fluctuations

facies changes in the triassic jurassic boundary interval in an intraplatform basin succession at csővar transdanubian range hungary a continuous pelagic marine triassic jurassic boundary section is exposed in newly excavated trenches in the surroundings of cso var ne of budapest hungary in the late triassic this area was located close to the offshore margin of the dachstein carbonate platform system that was segmented by intraplatform basins based on detailed facies analysis of the rhaetian hettangian platform foreslope basin succession a long term second order and superimposed shorter term third and fourth order changes of the relative sea level could be revealed after a period of highstand platform progradation in the late norian large amounts of larger plant fragments and sporomorphs of continental plants mark a significant sea level drop in the early rhaetian presumably exposing large parts of the platform a renewed transgression led to the formation of smaller build ups fringing the higher parts of the previous foreslope crinoid meadows may have occupied the slopes a potential source area of the bioclastic carbonate turbidites rising relative sea level that followed the marked early rhaetian lowstand is also reflected in the general facies trend from lithoclastic debris flows and proximal to the very distal turbidites and radiolarian basin facies up to the earliest hettangian meter scale high frequency probably fourth order deepening upward cycles probably indicating sea level oscillation could also be recognized within this interval at the base of the last rhaetian cycle about 10 m below the assumed tr j boundary the amount of bioclasts including conodonts drastically decreases biotic decline in the radiolarian basin facies characterizing the topmost part of this cycle a significant negative shift in both the d 13 ccarb and d 13 corg and a marked decrease in the organic material toc was recognized that can be interpreted to reflect reduced productivity in connection with the triassic jurassic boundary event it is overlain by a lithoclastic horizon then by laminites where the last conodonts were found the next significant facies change in the early hettangian is marked by appearance of redeposited oncoid grapestone beds suggesting survival of shallow marine carbonate factories in the neighborhood of the basin and the end of the rhatian to earliest hettangian sequence third order the recurrence of basin facies above this interval indicates a new short term third order transgression and continuation of the long term second order deepening trend in the early hettangian d 2004 elsevier b v all rights reserved

dramatic local environmental change during the early eocene climatic optimum detected using high resolution chemical analyses of green river formation stromatolites abstract the eocene green river formation represents a system of lakes that covered parts of what is now wyoming colorado and utah and captures the early eocene climatic optimum eeco 52 50 million years ago or ma the warmest period of the cenozoic era and a period associated with very high levels of atmospheric co2 lakes especially closed basin lakes can respond dramatically to environmental change because of their sensitivity to precipitation and evaporation in this study stromatolites from the rife bed of the green river formation are used as fine scale records of terrestrial paleoenvironmental change during a global hothouse climate and to investigate how the environmental dynamics within the lake system affected the growth of stromatolites the stromatolites are composed of branching microdigitate columns laminated on the 10 100 m scale laminae are grouped in cm scale layers that alternate between calcite fan micritic and mixed microstructures the fan layers are depleted in 18o na and mg ca the micrite layers in contrast are comparatively enriched in 18o na and mg ca the 13c and 18o are strongly positively correlated suggesting the stromatolites formed in a closed basin lake consistent with the regional stratigraphy additionally clumped isotope analyses provide the first quantitative values for water temperatures in lake water from the green river formation 35 c for micrite layers and 28 c for fan layers changes in 18o and sodium ion concentration are likely related to periods of evaporation and recharge and thus can be used to estimate lake volume change during stromatolite growth two models one using sodium ion concentrations in a conserved system the other using rayleigh fractionation and mixing equations to explain changes in oxygen isotopes converge upon similar results for lake volume changes revealing multiple episodes of meter scale lake level rise and fall during the accretion of the 30 cm thick stromatolite because of the broad flat bathymetry of the lake such lake volume and depth changes would have been accompanied by shoreline shifts on the order of tens of kilometers while the stromatolites were actively growing challenging the view of a single stromatolite paleoenvironment in the lake therefore the fan microfabric interpreted here as abiogenic in nature formed in cooler waters when the lake was deeper possibly below a thermocline in contrast the micrite microfabric for which there is evidence of biogenicity formed when the lake was shallow and warm the alternation between biogenic and abiogenic microfabrics present in the rife bed stromatolites is hypothesized to result from dramatic changes in lake level influencing the microbiology and chemistry of the waters in which the stromatolites formed indicating that stromatolite growth can occur under disparate conditions and therefore does not necessarily represent a single facies

microbial carbonates the geological record of the calcified bacterial algal mats and biofilms summary deposits produced by microbial growth and metabolism have been important components of carbonate sediments since the archaean geologically best known in seas and lakes microbial carbonates are also important at the present day in fluviatile spring cave and soil environments the principal organisms involved are bacteria particularly cyanobacteria small algae and fungi that participate in the growth of microbial biofilms and mats grain trapping is locally important but the key process is precipitation producing reefal accumulations of calcified microbes and enhancing mat accretion and preservation various metabolic processes such as photosynthetic uptake of co2 and or hco3 by cyanobacteria and ammonification denitrification and sulphate reduction by other bacteria can increase alkalinity and stimulate carbonate precipitation extracellular polymeric substances widely produced by microbes for attachment and protection are important in providing nucleation sites and facilitating sediment trapping microbial carbonate microfabrics are heterogeneous they commonly incorporate trapped particles and in situ algae and invertebrates and crystals form around bacterial cells but the main component is dense clotted or peloidal micrite resulting from calcification of bacterial cells sheaths and biofilm and from phytoplankton stimulated whiting nucleation interpretation of these texturally convergent and often inscrutable fabrics is a challenge conspicuous accumulations are large domes and columns with laminated stromatolite clotted thrombolite and other macrofabrics which may be either agglutinated or mainly composed of calcified or spar encrusted microbes stromatolite lamination appears to be primary but clotted thrombolite fabrics can be primary or secondary microbial precipitation also contributes to hot spring travertine cold spring mound calcrete cave crust and coated grain deposits as well as influencing carbonate cementation recrystallization and replacement microbial carbonate is biologically stimulated but also requires favourable saturation state in ambient water and thus relies uniquely on a combination of biotic and abiotic factors this overriding environmental control is seen at the present day by the localization of microbial carbonates in calcareous streams and springs and in shallow tropical seas and in the past by temporal variation in abundance of marine microbial carbonates patterns of cyanobacterial calcification and microbial dome formation through time appear to reflect fluctuations in seawater chemistry stromatolites appeared at 3450 ma and were generally diverse and abundant from 2800 to 1000 ma inception of a proterozoic decline variously identified at 2000 1000 and 675 ma has been attributed to eukaryote competition and or reduced lithification thrombolites and dendrolites mainly formed by calcified cyanobacteria became important early in the palaeozoic and reappeared in the late devonian microbial carbonates retained importance through much of the mesozoic became scarcer in marine environments in the cenozoic but locally re emerged as large agglutinated domes possibly reflecting increased algal involvement and thick micritic reef crusts in the late neogene famous modern examples at shark bay and lee stocking island are composite coarse agglutinated domes and columns with complex bacterial algal mats occurring in environments that are both stressed and current swept products of mat evolution ecological refugia sites of enhanced early lithification or all three

the continental margin of the mesozoic tethys in the western alps abstract most of the structural units of the western alps were derived from the european continental margin of the ligurian ocean a segment of the mesozoic tethys ocean their mesozoic palaeotectonic and stratigraphic evolution bears witness of the following main stages 1 deposition of the triassic platform carbonates essentially prerift but nevertheless bearing the imprint of some extensional movements 2 the liassic middle jurassic rifting corresponds to the creation of a horst and graben system with especially tilted blocks and hence a shoal and basin palaeogeography but without a preliminary doming event 3 the late jurassic early cretaceous opening and spreading of the ligurian ocean began with a general collapse of the continental margin thermal subsidence latest middle jurassic and earliest late jurassic in this paper emphasis is given to the refting derived structures more especially to the major tilted crustal blocks a few tens of kilometres wide which can be either reconstructed or directly observed the rifting stage lasted roughly 40 m y with the alternation of extensional tectonic phases and of relatively quiet periods during the extensional phases movements along fault planes and related episodes of tilting were followed by sudden and rapid episodes of subsidence the latter may be interpreted as resulting from the isostatic and thermal readjustment that follows a phase of stretching of the crust and of the lithosphere the tectonic evolution of the margin continued but decreased during the late jurassic early cretaceous oceanspreading stage tectonic activity resumed in the late cretaceous this probably resulting from the beginning of contraction of both the ocean and the continental margin leading progressively to the continental collision in the tertiary

temporal and environmental significance of microbial lamination insights from recent fluvial stromatolites in the river piedra spain despite extensive research the environmental and temporal significance of microbial lamination is still ambiguous because of the complexity of the parameters that control its development a 13 year monitored record of modern fast accreting calcite stromatolites mean 14 mm year 1 from artificial substrates installed in rapid flow in the river piedra north east spain allows comparison of the sedimentological attributes of successive six month depositional packages with the known climatic hydrophysical and hydrochemical parameters of the depositional system the stromatolites are formed of dense porous and macrocrystalline composite laminae the dense and porous composite laminae which are composed of two to eight laminae consisting largely of calcified cyanobacteria are characterized by i dense composite laminae up to 15 mm thick mostly with successive dense laminae and minor alternating dense and porous laminae and ii porous composite laminae up to 12 mm thick consisting mainly of porous laminae alternating with thinner dense laminae most of the dense composite laminae formed during the warm periods april to september whereas most of the porous composite laminae developed in the cool periods october to march each dense and porous composite lamina represents up to or slightly longer than six months the alternation of these two types of composite laminae parallels seasonal changes in temperature the dense and porous laminae result from shorter for example intraseasonal variations in temperature insolation and hydrological conditions the macrocrystalline laminae with crystals 100 m long occur isolated and grouped into composite laminae up to 1 7 mm thick their occurrence suggests the absence or poor development of microbial mats over periods of weeks to several months thus stromatolite lamination can record different order periodic and non periodic changes in the magnitude of environmental parameters over a single year these results hold important implications for the temporal and environmental interpretation of lamination in microbial structures

sea level highstand and lowstand shedding related to shelf margin aggradation and emersion upper eocene oligocene of maiella carbonate platform italy abstract sequence stratigraphic analysis of the upper eocene lower oligocene of the maiella carbonate platform allows the timing of shelf aggradation and erosion to be linked to shedding onto the slope and relative sea level stands the shelf was eroded during lowstands and the lowstand slope sediments are thin channelized lithic breccias with clasts eroded from an emerged reef tract highstand shedding of skeletal sands from the inner shelf resulted in thick coarsening and thickening upward successions of turbidites

north atlantic oscillation recorded in carbonate δ18o signature from lagunillo del tejo spain abstract oxygen 18o and carbon 13c isotope compositions of authigenic carbonates measured in lagunillo del tejo sediment document precipitation variability during the last millennium in the iberian range modern water samples show that lagunillo 18o and d plot below the global meteoric water line gmwl sediment samples show a covariant trend between carbonate 18o and 13c indicating that the precipitation evaporation ratio has largely controlled the isotopic composition of this lake this covariant trend is used to extract information about past lake level changes humid periods occurred around ad 1300 1450 ad 1620 1775 and ad 1950 1980 while the driest periods were concentrated around ad 1200 ad 1500 and especially around the transition between the 19th and 20th centuries we compared these inferences with previous studies in this lake and with nao index and discovered strong correspondence of signals this sensitive site can be used to extent records of nao back in time providing a framework for climatic modeling and ecological management

quantifying the role of geographic change in cenozoic ocean heat transport using uncoupled atmosphere and ocean models abstract a series of five cenozoic atmospheric general circulation model agcm experiments has been performed using a new set of paleogeographic reconstructions for 55 40 33 20 and 14 ma the five continental reconstructions incorporate the tectonic evolution of early eocene to middle miocene continental positions and topography with all other model boundary conditions and forcings held constant the series of agcm experiments captures a

intrinsic and extrinsic controls of spatial and temporal variations in modern fluvial tufa sedimentation a thirteen year record from a semi arid environment sedimentological and hydrochemical parameters of the river piedra north east spain were monitored every six months from 1999 to 2012 at 24 sites at which tablets were installed all along the river the river water is of hco3 so4 ca type and is notably influenced by inputs from upstream karstic springs tufa deposition was first detected 8 km downstream of these springs and greatly increased from there primarily along the steeper stretch i e within the monasterio de piedra natural park then deposition decreased through the most downstream stretch with smaller ground water inputs the spatial evolution of the tufa thickness with parallel variations of pwp plummer wigley parkhurst rates was thus determined by the river water pco2 which was controlled by ground water inputs and by the river bed slope five fluvial subenvironments and seven sedimentary facies were characterized the water flow conditions are the primary factor responsible for the distinct deposition rates of facies mainly through co2 outgassing stromatolites and moss tufa and alga tufa had the highest rates whereas loose tufa formed in slow flowing water and tufa of spray areas had thinner deposition a six month pattern in the deposition rate was detected through thickness measurements that pattern was parallel to the seasonal pwp rates the increased deposition during warm periods spring and summer mean 5 08 mm compared with cool periods autumn and winter mean 2 77 mm is linked chiefly to temperature which controlled the seasonal changes in the physico chemical and biological processes this finding is supported by a principal components analysis seasonal variations of insolation and day duration also contributed to such a deposition pattern large discharge events which provoked erosion of tufa deposits and dilution of water caused the reversal of the seasonal deposition rate pattern stromatolites are likely to preserve the most complete sedimentary record although tufas are a potentially sensitive record of climate related parameters erosion is an intrinsic process that may overwhelm the effects of such parameters this issue should be considered in palaeoclimatic studies based on the tufa record particularly in semi arid conditions

millennial scale climatic cycles in the early pliocene pollen record of ptolemais northern greece early pliocene lacustrine sediments from the ptolemais basin northern greece exhibit a climatically induced cyclicity which can be correlated with the orbital cycle of precession superimposed on precession controlled cycles palynological time series data reveal a higher order climatic cyclicity with periodicities of 10 2 5 and 1 5 ka these millennial scale vegetation changes are likely to reflect changes of the soil moisture gradient on mountain slopes caused by fluctuations in orographic winter precipitation such fluctuations corroborate the concept of a nao like north atlantic climatic teleconnection during early pliocene times the periodicities are similar to those of climate oscillations inferred from quaternary records the occurrence of millennial scale cyclicity in a time interval when the northern hemisphere was essentially ice free implies an ultimate forcing mechanism that operated independently of changes in the thermohaline circulation in the atlantic ocean the cycles are likely to be related to long period variations in solar activity

the effect of drainage reorganization and climate on the sedimentologic evolution of intermontane lake systems the final fill stage of the tertiary ebro basin spain abstract stratigraphic and sedimentologic analyses and geochemical data from the middle and late miocene record in the southwestern central sector of the ebro basin have allowed the evolution of its neogene final fill stage to be characterized and its controlling factors to be discerned the focus of these analyses was the distinct depositional environments that occurred over time tecto sedimentary units t6 t7 and t8 twelve main associations of lacustrine palustrine fluvial and alluvial facies revealed that the sedimentary processes leading to the formation of the units occurred in different environments in units t6 and t7 middle and late aragonian i e langhian serravallian and in unit t8 vallesian turolian i e tortonian the depositional environments of units t6 and t7 encompassed a closed shallow carbonate lake system with wide palustrine fringes the lake was fed by small sandy and gravelly channels flowing from the southwest iberian range and a sandy fluvial system from the north pyrenees inputs were also received from a southeastward flowing axial fluvial system as the mouths of these systems commonly formed small deltaic sandy lobes on the northern lake margins the evolution of unit t6 and in particular that of unit t7 was greatly influenced by pyrenean tectonics the depositional environments of unit t8 included the occurrence of the as but this system was soon replaced by an open shallow carbonate lake surrounded by wide and shallow oncoid bearing channels and palustrine tufaceous areas on its west southwest margin distinct depositional events from the south and west which involved intra t8 erosion resulted in minor coarse alluvial deposits the carbonate system of unit t8 occurred in an open depression created after local erosion of the pre t8 deposits and subsequent northward shifting of the as since early deposition of unit t8 the origin of which was related to late contractile deformation in the northwestern iberian range bicarbonate and calcium rich water from the mesozoic carbonate rocks in the iberian range fed the t8 system sedimentologic 13c 18o and trace element data support the change from closed to open drainage and strongly suggest a general climate trend toward wetter and cooler conditions which is consistent with the middle late miocene climate evolution of other european regions despite the general timing coincidence between unit t8 deposition and the opening process of the ebro basin the attributes of the t8 deposits are inconclusive to support the previous hypothesis that the fluvial lacustrine palustrine system could be directly connected to the emptying drainage of the basin into the mediterranean sea instead the results of this study demonstrate the combined influence of tectonics and climate on the evolution of the final fill stage of this part of the ebro basin these results may be useful for assessing the influence of such allocyclic factors on the sedimentologic hydrologic and geochemical evolution of other intermontane lake basins

evolution of a high relief carbonate platform slope using 3d digital outcrop models lower jurassic djebel bou dahar high atlas morocco abstract seismic scale continuous exposures of an early jurassic carbonate platform located in the southern high atlas of morocco provide detailed quantitative information about the lithofacies and stratal geometries of an aggrading retrograding and prograding steeply inclined slope system that evolved in an active intracratonic rift basin aggradational backstepping and progradational outer platform to slope transects are each characterized by distinct lithological features and stratal patterns a digital outcrop model was constructed using real time kinematic global positioning system and lidar storing information on recorded stratal surfaces including lithofacies information from these data 3d models of the slope system could be built in the study area four stages of slope development are recognized stage 1 corresponds to a low relief carbonate platform characterized by widespread sub wave base depositional conditions stage 2 developed as an aggrading to retrograding platform during which the platform built considerable relief in addition a massive organically bound upper slope fringe formed dominated by coral sponge microbial boundstone the in situ boundstone consisted of irregular wedges that accreted on the upper slope down to 140 m below the platform break after a period of sediment starvation stage 3 involved a major backstepping of sediment deposition seventy meter high clinoforms prograded from the center of the platform across the platform top until reaching the relict platform break of stage 2 subsequently progradation occurred basinward as indicated by the spilling of lobes down the existing slope deposits of stage 2 limited progradation along with the reestablishment of the in situ coral sponge microbial boundstone on the upper slope led to the progressive steepening of the slope profile to dips of 23 clinoforms are planar in the upper part of the slope and concave upwards in the lower part with a total relief of over 460 m stage 4 is observed only in the lower slope and adjacent basin coarse detrital carbonate deposits form lens shaped aprons that grade basinward into kilometer scale lobes that alternate with thick wedges of basinal fallout sediments syndepositional extensional faults operating in the subsurface affected sedimentation along the lower slope profile throughout the four stages and are expressed in the stratal patterns through growth strata in monoclinal folds three dimensional digital outcrop models reconstructing the architecture of the slope system allowed quantification of slope geometries and stratal relationships and spatial distribution of sedimentary bodies the digital model enhanced the understanding of the depositional changes during slope evolution and also led to observations on for example angular relationships that would have been difficult to detect without the digital approach the evolution from aggrading to retrograding prograding and retrograding was strongly influenced by synsedimentary tectonics within an intracratonic rift basin the tectonics generated irregular distribution of accommodation space variably interfering with eustatic sea level movement this in combination with the character of lithofacies types and style of sedimentary processes along the slope such as in situ boundstone growth and gravity driven resedimentation processes directly controlled carbonate slope architecture and stratigraphy of the djebel bou dahar and influenced stratal anatomy and lithofacies distribution

sea level changes an integrated approach sea level changes an integrated approach in october 1985 sepm sponsored a four day conference entitled sea level changes an integrated approach the purpose of the conference was to provide a forum for an interdisciplinary exchange of ideas on sea level changes and to provide an opportunity for integrating various types of evidence in approaching unresolved issues the conference was successful in bringing together scientists from industry academia and government representing all of the major geosciences disciplines presentations of many new papers plus significant releases of data that were previously held proprietary provided fertile ground for discussion this much cited volume represents the best of the material presented at the conference includes the early vail chart

palaeoclimate interpretation of stable isotope data from lake sediment archives the isotope composition of authigenic and biogenic carbonates and diatom silica are commonly used as palaeoclimate proxies from lake sediments this article reviews the controls on the isotope composition of lacustrine skeletal and non skeletal deposits and illustrates how stable isotope studies contribute to an understanding of changes in temperature precipitation patterns evaporation and the carbon cycle it highlights the differences in the palaeoclimate potential of a wide range of lakes ranging from open to closed lake basins a large number of the case histories but not all are drawn from studies of temperate lakes from europe large closed lake systems in the tropics and elsewhere lose water predominantly through evaporation and contain sediments with variable and generally high 18o values fluctuations in the isotope composition of authigenic or biogenic minerals are mainly a function of long term changes in the precipitation evaporation ratio in contrast small open lakes which have a degree of through flow typically contain sediments with 18o values that vary by no more than a few these variations are generally ascribed to variations in temperature or the isotope composition of precipitation p from which either an annual or seasonally specific signal can be gained these types of lakes are common in northern europe and at high altitudes the interpretation of isotope data from a lacustrine succession requires a knowledge of the local processes that might control and modify the signal their effects need to be quantified and a robust calibration using the modern lake system is necessary to establish the relationship between the measured signal the isotopic composition of the host waters and climate

understanding the geological record of carbonate platform drowning across rifted tethyan margins examples from the lower jurassic of the apennines and sicily italy abstract in the geological record a drowning process is documented by various types of shallow water to pelagic or shallow water to mixed benthic pelagic carbonate transitions drowning unconformities are paraconformities to disconformities to angular unconformities and their drowning surfaces range from planar to highly irregular morphologies drowning successions display a mix of products of both the benthic and pelagic carbonate factories these successions can be also bounded by unconformities drowning unconformities and drowning successions are contrasted through a description and discussion of examples of escarpment bounded platforms from the jurassic of the northern apennines and subordinately from sicily and other tethyan sectors the areal distribution of drowning unconformities and successions is discussed with reference to a complex depositional system whose architecture was the product of the rift induced fragmentation of a regional hettangian carbonate megabank the examples in this study show drowning unconformities to be exclusive to intrabasinal highs while drowning successions are found both on highs and in hangingwall basins drowning unconformities with their long associated hiatuses and drowning successions are often seen to merge laterally into one another over very short distances on the same intrabasinal high the deposits of the drowning succession are sometimes missing on the top of the platform while they are found forming clinoforms along its flanks evidence that sediment could be permanently swept from the highs in these depositional systems at this stage

evolution of nao and amo strength and cyclicity derived from a 3 ka varve thickness record from iceland abstract a 3000 year varve thickness record from hvitarvatn a glacier dominated lake in central iceland preserves inter annual variations in the delivery of glacially eroded sediment to the lake the first order low frequency trend in varve thickness reflects increased glacial erosion through the late holocene reaching a peak during the little ice age lia superimposed on this trend are large inter annual to decadal fluctuations in varve thickness that we suggest reflect variability in climate parameters that determine the efficiency of the fluvial transport system to deliver glacially eroded sediment to the lake each year we use spectral analysis to test whether regular high frequency cyclicity in varve thickness exists in the 3 ka record after removing the low frequency variability spectral analyses from three sediment cores recovered from the lake show essentially the same periods of 2 8 3 4 13 35 40 and 85 93 for the overlapping 900 year period additionally cycles of 55 130 and 290 years are found in the spectrum for the 3000 year record that do not show up in the spectra for the shorter cores some of these cycles show similar variability to those of the north atlantic oscillation nao and atlantic multidecadal oscillation amo this relationship is supported by a significant correlation between varve thickness and both the nao precipitation and amo summer temperature indices over the 180 year instrumental period nao cyclicities 2 15 years are weakly expressed in the first half of the record increase between 600 and 1000 ad decrease in strength during medieval time and are most strongly expressed between 1300 ad and the early 20th century amo cyclicities 50 to 130 years are also relatively weak in the first half of the record becoming quite strong between 600 and 1000 ad and again between 1100 and 1500 ad but are essentially absent through the peak of the lia between 1500 and 1900 ad a time when strong cyclicities of about 35 years appear

environmental gradients in carbonate sediments and rocks detected by correspondence analysis examples from the recent of norway and the dinantian of southwest england continuous sedimentary gradients are only crudely expressed by standard facies and microfacies methods which are more appropriate to situations where changes occur in relatively discrete steps in carbonate sediments and rocks continuous gradients are often represented by the arrangement of component grain types in a relay that is a systematic shifting of the relative importance of the components subdivision of such relays into micro facies can only be arbitrary correspondence analysis is shown to be useful for detecting isolating and describing relays particular use is made of the arch effect in which samples and components from data sets with a strong unidimensional structure a relay plot in the form of an arch in the plane of the first two factor axes a relay index indicating the position of samples in the relay can be extracted from the analysis and plotted on maps and stratigraphic logs to reveal details of the sedimentary gradient in areal and or stratigraphic context examples are given from i recent shallow marine carbonate sediments from northern norway illustrating a relatively simple depositional setting where surface sediments are viewed in plan and ii lower carboniferous carbonates of southwest england representing a more complex regional study of a particular stratigraphic interval viewed in cross section in both examples the relays can be related to identifiable environmental gradients

external controls on the distribution fabrics and mineralization of modern microbial mats in a coastal hypersaline lagoon cayo coco cuba active carbonate mineralizing microbial mats flourish in a tropical highly evaporative marine fed lagoonal network to the south of cayo coco island cuba hypersaline conditions support the development of a complex sedimentary microbial ecosystem with diverse morphologies a variable intensity of mineralization and a potential for preservation in this study the role of intrinsic i e microbial and extrinsic i e physicochemical controls on microbial mat development mineralization and preservation was investigated the network consists of lagoons forming in the interdune depressions of a pleistocene aeolian substratum they developed due to a progressive increase in sea level since the holocene the hydrological budget in the cayo coco lagoonal network changes from west to east increasing the salinity this change progressively excludes grazers and increases the saturation index of carbonate minerals favouring the development and mineralization of microbial mats in the easternmost lagoons detailed mapping of the easternmost lagoon shows four zones with different flooding regimes the microbial activity in the mats was recorded using light dark shifts in conjunction with microelectrode o2 and hs profiles high rates of o2 production and consumption in addition to substantial amounts of exopolymeric substances are indicative of a potentially strong intrinsic control on mineralization seasonal climate driven water fluctuations are key for mat development mineralization morphology and distribution microbial mats show no mineralization in the permanently submersed zone and moderate mineralization in zones with alternating immersion and exposure it is suggested that mineralization is also driven by water level fluctuations and evaporation mineralized mats are laminated and consist of alternating trapping and binding of grains and microbially induced magnesium calcite and dolomite precipitation the macrofabrics of the mats evolve from early colonizing flat mats to complex cerebroid or terrace structures the macrofabrics are influenced by the hydrodynamic regime wind driven waves inducing relief terraces in windward areas and flat morphologies on the leeward side of the lagoon other external drivers include i storm events that either promote for example by bioclasts covering or prevent for example by causing erosion microbial mat preservation and ii subsurface degassing through mangrove roots and desiccation cracks covered by flat mats i e forming hemispheroids and cerebroidal structures these findings provide in depth insights into understanding fossil microbialite morphologies that formed in lagoonal settings

compositional variations during phases of progradation and retrogradation of a triassic carbonate platform picco di vallandro durrenstein dolomites italy in this paper data are presented on the composition of sediments deposited at the toe of slope during progradation or retreat of triassic carbonate platforms in the dolomites italy for this purpose a succession was studied from the toe of slope of a triassic carnian carbonate platform picco di vallendro durrenstein dolomites italy the microfacies analysis of selected calciturbidites sequences revealed a reduced input of oncolites and ooids during progradation and an increase in clasts the main input however was derived from the reefs on the platform retrogradation of the platform showed an increase of filaments and radiolarians open ocean biota as well as carbonate mud and a reduced input of grains that originated within the reefs on the platform both during progradation and retrogradation parts of the platform were flooded and could produce excess sediment that could be exported to the surrounding basins however the absence of platform interior biota documents that progradation occurred from sediments of the reefal belt probably during relative sea level lowstands carbonate composition varies systematically with toe of slope progradation retrogradation and thus argues for carbonate production as the main driver of the geometries observed at the toe of slope

laminated eocene maar lake sediments from eckfeld eifel region germany and their short term periodicities abstract the eocene age eckfeld eifel maar lake is interesting both because of the excellently preserved fossil remains and also for the laminated sediment sequence deposited under subtropical conditions the latitude however has a higher seasonal insolation difference than comparable recent environments due to the northward shift of climatic zones during the eocene the overall aim of this investigation was to compare sediment types and lake development of a tertiary subtropical maar lake with recent maar lakes to discuss the origin of laminations and search for their possible periodicities the main sediment types which were exposed during recent paleontological excavations are laminated oilshales partly laminated bituminous siltstones and graded beds mostly turbidites which sometimes include laminated clay tops some deeper parts of the profile drilled in 1980 are dominated by diatomaceous laminites the amount of organic carbon around 8 5 is comparable with recent lakes with low sedimentation rates the high c n ratios 25 30 of the eckfeld sediments as well as the fact that the highest corg values are found in the graded beds shows the importance of terrestrial plant debris for these lake sediments lamination of the oil shales was caused by the complex interrelationship of clastic supply mineral and plant detritus autochthonous organic deposition mainly green algae and early diagenetic siderite formation the darker sublaminae represent the coarser clastic organic and inorganic input together with the autochthonous supply from the lake green algae whereas the lighter sublaminae are composed of settled fine grained mostly siliciclastic detritus derived from the probable yearly turnover of the density stratification of the lake the thickness of the fine siliciclastic and organo clastic layers the morphology and palaeogeographical situation of the maar lake and the occurrence of algal layers strongly suggest that the laminated sediments are varves although there is no definitive proof of this thickness variations from ca 700 oil shale laminae were measured and computed time series analysis yielded at least one certain period of 5 5 yr accepting that the laminae are indeed varves the duration of the laminated lake sequence from eckfeld maar as deduced from sedimentation rates of the different sediment types is ca 82 000 yr and thus within the typical life time of other small maar lakes

latest oligocene late miocene lacustrine systems of the north central part of the ebro basin spain sedimentary facies model and palaeogeographic synthesis abstract in the central part of the ebro basin spain north of the ebro river three allostratigraphic or tectosedimentary units differentiated within the latest oligocene late miocene upper agenian vallesian interval are sedimentologically characterized these deposits represent carbonate and sulphate lacustrine environments fed by pyrenean alluvial systems luna system and huesca system in each unit several facies associations or lithofacies were mapped these interfinger through time gypsum lithofacies occupy the southernmost part of the study area and are surrounded by carbonate and or detrital lithofacies to the north each lithofacies consists of different carbonate sulphate and or detrital facies arranged in simple sequences decimetres to metres thick the four types of sequences characterized reflect a complex shallowing evolution involving carbonate or sulphate contexts thus each lithofacies represents the sedimentation in a particular lacustrine or alluvial subenvironment a single lacustrine system is proposed for the central part of the basin its evolution followed cycles of water level variations which caused kilometre scale migrations of the lake shoreline in this model two distinct situations or lakes alternated through time a one represents high levels associated with a single body of dilute carbonate water where massive carbonate facies formed influenced by organism proliferation these lakes had wide palustrine vegetated margins in which bioturbated facies developed b the other represents low levels that correspond to a playa lake model laminated sulphate deposits formed in the lake waters while nodular gypsum originated in the surrounding saline mud flats and within the exposed previously deposited carbonate sediments transitions from one situation to the other including minor water level fluctuations within carbonate sedimentation conditions were marked by the development of laminated and stromatolitic facies lake level variations were caused by climatic cycles and gave rise to the simple sequences and to the lithofacies lateral relationships recognized in this study correlation among tectosedimentary units in the studied pyrenean domain and in the iberian domain of the ebro basin shows that for units n1 and n2 the facies that resulted from dilute carbonate waters are rare in the lacustrine areas of the iberian margin this indicates that a strong hydrological contrast existed between both regions on this basis a theoretical asymmetrical facies model is proposed for the single lacustrine basin that extended over these regions

facies architecture of an early jurassic carbonate platform slope jbel bou dahar high atlas morocco the plateau of jbel bou dahar high atlas morocco represents an outstanding example of a well preserved early mesozoic carbonate platform field observations of the large scale sedimentary structures and the arrangement of lithofacies associations within the mid and lower slope were combined with detailed microfacies analyses and gamma ray measurements the investigations were carried out in order to 1 resolve the sequence stratigraphic architecture of the slope and 2 reconstruct the sediment export patterns and depositional processes related to high frequency sea level variations the slope strata are arranged into two different types of lithofacies associations that are bounded by characteristic discontinuities and show a specific occurrence along the investigated slope section the steep 8 18 mid slope is dominated by thick to medium bedded limestone successions that were able to maintain a high angle of repose due to their detrital composition the sediment packages are bounded by basal low angle unconformities and wedge out within the lower slope or thin into the adjacent basin as single carbonate layers the sediments are characterized by coarse grained and poorly sorted floatstones to rudstones which show low gamma ray values and contain components derived mainly from the platform edge the facies associations were interpreted as debris flow deposits that were exported during sea level lowstands when the flattened platform top and extended parts of the margin were exposed and sediment production was restricted mainly to the outer margin and upper slope section in contrast the gently dipping lower slope 4 18 is characterized by rhythmic limestone marl alternations that show increasing thicknesses with increasing distance from the platform from the lower part of the mid slope down the successions onlap the debris flow deposits forming a characteristic interfingering pattern of different lithofacies associations the medium to thin bedded carbonates of the limestone marl alternations comprise two different microfacies types 1 mudstones to wackestones with high gamma ray values and a mixed shallow marine to deep marine microfacies overlain by 2 well sorted arenitic packstones to grainstones with low gamma ray values and a shallow marine component composition the latter points to the platform interior and margin as primary source areas the shallow marine material was exported during sea level highstands when the carbonate factory included the entire platform margin and the flooded lagoons of the platform top during these periods the exported fine grained sediments could maintain only low angles of repose thus they bypassed the steep upper and mid slope sections developed into turbidites during downslope transport and were finally redeposited on the gently dipping lower slope and in the adjacent basin the architecture of the investigated slope area shows a characteristic interfingering of different facies associations that can be interpreted as genetic highstand and lowstand stratigraphic sequences the arrangement of these sequences along the slope as well as their composition were controlled by high frequency sea level fluctuations affecting the primary sediment production source area export patterns and sedimentary processes resulting in a shift of the depositional centers during different sea level stands

stratal patterns sediment composition and sequence stratigraphy at the margin of the vercors carbonate platform lower cretaceous se france abstract conventional sequence stratigraphic concepts relate the large scale stratal architecture of sediment bodies to changes in relative sea level this paper evaluates the relationship between stratal geometry and sea level stand based on a study of large semicontinuous outcrops of cretaceous carbonate platform strata in the vercors southeastern france multiple lines of evidence for sea level change are combined including stratal geometry detailed quantitative microfacies analyses and diagenetic patterns at platform top hardground surfaces the studied outcrops of the cirque d archiane show two main prograding platform tongues both over 100 m thick the stratal geometries at the boundary between these platform tongues including an apparent pinchout of a wedge of slope sediments suggest the presence of a major lowstand unconformity however this stratal boundary does not coincide with the horizon containing the most extensive meteoric alteration furthermore detailed platform to basin correlation shows that the wedge of slope sediments is not basin restricted but makes a thin drape over the platform top the sedimentologic and diagenetic evidence suggest incipient drowning of the platform at the boundary between the two main platform tongues preceded by a minor exposure event only internally the main platform tongues consist of smaller 10 30 m thick units that prograde towards the basin and aggrade on the platform top and which are interpreted as stacked highstand wedges these wedges are usually topped by hardground surfaces with minor evidence for subaerial exposure the platform top horizon with the most extensive subaerial diagenesis and erosion correlates with a distinct but relatively thin unit of lithoclastic debris on the slope a pronounced scour in the clinoforms of the vercors does not correlate with a major exposure surface on the platform top this study shows that stratal geometries alone are a rather ambiguous guide to sea level history without the accompanying sedimentologic and diagenetic evidence for sea level change most of the stratal architecture of the vercors platform can be explained by either changes in accommodation or changes in carbonate production

combined textural and stable isotopic data as proxies for the mid cretaceous paleoclimate a case study of lacustrine stromatolites in the gyeongsang basin se korea abstract microbial interference of the prevailing sedimentary dynamics during stromatolite growth records vital biogeochemical information which reflects the prevailing paleoclimatic conditions this study documents the simultaneous geochemical and textural changes in mid cretaceous lacustrine stromatolites gyeongsang basin se korea deposited in a semi arid setting fibrous calcite micrite couplets in the stromatolites occurring in the sinyangdong hwasan and banyawol formations constitute the basic growth cycles and can be divided into first second and third order cycles second order cycles show couplets with gradual textural changes from fibrous calcite to micrite laminae and three different types of micrite are present sometimes one type of micrite evolves into another within the second order cycle in the sinyangdong stromatolites consistent enrichments in 18o and depletion in 13c towards micrites within the sinyangdong and hwasan stromatolite couplets and a concomitant depletion of both isotopes from fibrous calcite to micrite in the banyawol sample can be observed these shifts reflect paleohydrological changes in the lake water related to paleoproductivity and paleosalinity fluctuations relatively higher paleosalinity values within the sinyangdong lake water system is registered by higher 18o values of fibrous calcite and micrite in the sy 3 than in the sy 1 and sy 2 stromatolites the consistent shifts in 18o and 13c isotopes in different textural growth fabrics indicate that paleohydrological factors could play a significant role in the formation of these primary lacustrine carbonates textural changes shown by the frequency of the growth cycles also corresponds with oxygen and carbon isotopic values these results appear to have been influenced by climate related paleohydrological changes

basin to platform chemostratigraphy and diagenesis of the early cretaceous vercors carbonate platform se france abstract cathodoluminescence petrography has been combined with bulk rock and micro sampled 87 sr 86 sr 18 o and 13 c analyses to reconstruct the diagenetic history of lower cretaceous barremian limestones exposed at the southern margin of the vercors carbonate platform in southeastern france stratigraphic and geographic trends in these analyses coupled with mass balance water rock interaction modeling have been used to constrain the chemical composition source and relative timing of the groundwaters responsible for diagenetic alteration this study was completed on the montagnette outcrop which is composed of two stacked 70 m thick units of prograding platform margin limestones that interfinger with marly basinal sediments the montagnette exposure is exceptional in that it is a single complete outcrop of basin to platform limestones that are preserved in their original lateral depositional continuity cathodoluminescence petrography indicates that the limestones have experienced a complex sequence of carbonate dissolution precipitation and fracturing events over one hundred bulk rock and micro sampled 87 sr 86 sr 18 o and 13 c analyses were completed to characterize each major event of deposition and diagenesis bulk rock analyses from the montagnette basin to platform transect exhibited no significant variations in 87 sr 86 sr 0 707523 to 0 707555 these values are consistent with estimated barremian seawater 87 sr 86 sr ratios in contrast micro sampled shell material in the platform margin and platform top deposits exhibit large variations in 87 sr 86 sr 0 706910 to 0 707450 the least radiogenic sr lowest 87 sr 86 sr occurs in shell material located toward the platform while the more seawater like ratios occur in sections without shells that are located toward the basin this pattern implies that selective diagenetic alteration of the shell material took place after basinal brines flowed up into the platform and spread out laterally the sr in the diagenetic waters was probably derived from water rock interaction with jurassic basinal sediments in the vocontian trough this conclusion is based on 1 the extremely low 87 sr 86 sr composition of shell material in the platform limestone 2 modeled co variation trends in 87 sr 86 sr 13 c and 18 o and 3 the absence of another nearby source of less radiogenic sr in the vercors region

origin of annual laminations in tufa deposits southwest japan abstract laminated tufas and a tufa depositing stream in sw japan shirokawa ehime prefecture were studied monthly over a 3 yr period a series of samples from the tufa clearly reveals the pattern of annual laminations the annual layering pattern was primarily controlled by changes in the rate of calcite precipitation as calculated from water chemistry the concentration of dissolved caco 3 which correlates with the precipitation rate was high in summer autumn and low in winter spring owing to changes in the partial pressure of co 2 in underground air regular seasonal changes in underground pco 2 probably resulted from two temperature dependent processes the diffusion of soil co 2 and the ventilation of underground air these changes in addition to water temperature changes altered the precipitation rate which has a clear seasonal pattern especially in the lower stream the seasonal precipitation rate was high in summer autumn and low in winter spring which is consistent with the seasonal lamination pattern seen in the tufas the textures of collected samples show that the laminations consist of densely calcified summer autumn june october laminae and lightly calcified winter spring november may laminae we infer that the increased precipitation rate stimulated thick calcite encrustation on cyanobacterial filaments to produce the dense textures this interpretation is supported by the lowered organic inorganic carbon production ratio in summer autumn seasonal variations in cyanobacterial assemblages are present but do not reflect the seasonal lamination pattern because the relevant processes are temperature dependent the seasonal lamination pattern at shirokawa is thought to generally apply to other laminated tufas deposited in temperate climates however a reversed pattern can result from local and climatic circumstances dense laminae were deposited in winter near the source of the spring at shirokawa because calcite precipitation was high owing to low underground pco 2 in winter reversed patterns reported from northwestern europe were probably influenced by seasonal rainfall which is reflected in hydrological conditions

a 3000 year high resolution stalagmitebased record of palaeoclimate for northeastern south africa high resolution stable isotope variations and growth structure analyses of the last three millennia of a 6600 year stalagmite record at cold air cave makapansgat valley south africa are presented growth layers which are measurable over the last 250 years are shown to be annual the correlation between the width of growth layers and precipitation is strongly positive changes in 18o and 13c are positively correlated and inversely correlated to changes in the colour of the growth layers in the stalagmite variations in colour are directly correlated with mean annual temperature dark colouration is the product of increased temperature and mobilization of organic matter from the soil and is associated with wetter summers and enhanced growth of c4 grasses darker colouring and enriched 18o and 13c reflect a warmer wetter environment whereas lighter colouring and depleted isotopic values are indicative of cooler drier conditions the dominant episode in the 3000 year record is the cool dry 500 year

interpreting compositional variations of calciturbidites in relation to platform stratigraphy an example from the paleogene of se spain abstract in the sierra de aitana betic cordilleras southern spain a sequence of massive platform limestones outcrops study of these limestones indicates a late eocene age and has resulted in distinguishing four lithofacies associations several features suggest tilting uplift and partial exposure of this carbonate platform at the end of the eocene in a more basinward section this time interval is represented by calciturbidites the composition of which has been analysed microscopically the upper eocene turbidites are mainly composed of loose skeletal grains derived from the platform interior around the eocene oligocene boundary the composition changes abruptly and the lower oligocene turbidites mainly consist of platform derived limestone clasts and skeletal debris from the platform margin this compositional change is accompanied by a large decrease in volume of turbidite input it is concluded that both composition and amount of calciturbidites reflect the history of the adjacent carbonate platform this case study therefore provides new evidence for the mechanism of highstand shedding in carbonate depositional systems

the interactions of sea level change terrigenous sediment influx and carbonate productivity as controls on upper cambrian grand cycles of western newfoundland canada the upper cambrian stratal record in western newfoundland is complex and reflects the interplay and feedback between 1 changes in third order sea level 2 episodic incursion of terrigenous fines onto the paleoshelf and 3 productivity levels of the ancient carbonate factory mixed carbonate and terrigenous clastic rocks of western newfoundland are configured in large scale third order stratal patterns called grand cycles such cycles are tens to hundreds of meters in stratigraphic thickness and appear to span millions of years grand cycles are divided here into ribbon half cycles composed principally of ribbon rock and oolitic half cycles dominated by oolite stratigraphic distribution of shale in these rocks however is not everywhere coincident with large and small scale patterns in carbonate lithofacies and it suggests that the incursion of terrigenous clay and silt onto the ancient platform must be evaluated separately in part from the dynamics of carbonate accumulation areal and stratigraphic distribution of rock cycles record shifts in facies belts on the ancient platform presumably in response to third order changes in accommodation potential meter scale cycles in carbonate lithofacies are of two types peritidal cycles that fine upward and shelf cycles that coarsen upward thick successions of shelf cycles composed of ribbon rock are interpreted as highstand deposits and are separated by a sequence boundary marked by peritidal cycles from lowstand deposits comprising thick successions of ootite shelf cycles the former mid grand cycle transitions of previous workers are thereby reinterpreted in this study as sequence boundaries the long term position of sea level and thus the degree of platform inundation influenced the health of the platform carbonate factory during times of low sea level the platform was bathed in water more saline than open ocean sea water and it had a robust non skeletal carbonate factory that was resilient to poisoning by episodic influx of terrigenous fines onto the shelf in contrast the carbonate factory during highstands was less resilient to terrigenous poisoning and was susceptible to localized drowning by the reduction in the rate of carbonate sediment production the thick shale units are therefore interpreted to represent the coincidence of and interaction between 1 incursion of terrigenous fines onto the ancient platform and 2 a weakened highstand carbonate factory unable to recover from this terrigenous poisoning

a possible mechanism of solar modulation of the spatial structure of the north atlantic oscillation 1 the spatial structure of the north atlantic oscillation nao in winter differs significantly according to the solar cycle the nao is confined to the atlantic sector during low solar activity ls whereas it has a hemispherical structure during high solar activity hs the present study focuses on identifying the involved processes the results of analyses suggest that the solar activity influence originates in the stratopause region where the mode of interannual variation in the zonal mean zonal winds changes according to solar activity in the early winter of hs the leading zonal wind mode has a meridional dipole type structure that extends downward from the stratosphere to the troposphere through interaction with planetary waves the dipole type anomaly in the zonal winds produces a hemispherical scale seesaw pattern in the surface pressure between the polar region and surrounding regions thus the nao during hs has a hemispherical pattern during ls the downward extension of zonal mean zonal wind anomalies is weak so the regional scale variation becomes dominant in the troposphere

stable isotope characterization of the miocene lacustrine systems of los monegros ebro basin spain palaeogeographic and palaeoclimatic implications the lacustrine carbonate facies from three allostratigraphic units n1 n2 and n3 of miocene age in the los monegros region ebro basin are characterized isotopically the dominant facies are marls laminated limestones stromatolitic limestones massive limestones and bioturbated limestones these are associated with lacustrine sulphate deposits and distal alluvial facies palaeohydrological reconstructions of the study area are supported by the isotopic and the mineralogical composition of the carbonates massive and bioturbated limestones occupy a very similar compositional domain and have the lowest isotopic compositions of all the facies 9 18opdb 4 5 and 6 4 13cpdb 0 4 reflecting a short residence time of the water and variable commonly high influence of biogenic co2 laminated limestones and stromatolites define a comparatively enriched domain with 18o values ranging from 6 to 0 and 13c values ranging from 3 5 to 0 these values indicate stronger evaporation and enhanced 12c assimilation due to intense biological activity during periods of longer water residence time marls have isotopic values intermediate between these two domains and correspond to periods of lacustrine dilution dolomite bearing samples mainly laminated and stromatolitic facies show a 18odol cal 7 5 with respect to calcite from the same facies while 13c values show very little enrichment up to 1 the positive correlation r 0 85 between 18o and dolomite contents suggests that dolomite resulted from the progressive evaporative concentration of a single water mass and not from the mixing of waters of different compositions the dolomite is thought to be primary or at most the product of very early diagenetic processes the isotopic composition of the facies and their spatial and temporal variations depend on the depositional environment and were constrained by changing regional paleogeography isotopic trends from units n1 to n3 upper agenian vallesian period display a regular depletion in heavy isotopes that indicates a climatic change towards wetter conditions

carbonate platform flanks slope angle and sediment fabric more than 20 examples of fossil carbonate platform systems were compared for slope angle and sediment fabric plots of slope angle versus sediment fabric show that grainy non cohesive mud free sediments build steeper slopes than muddy cohesive sediments examples near the end members of grainy and muddy carbonate platform flanks are found in the triassic of the dolomites in northern italy and in the bahamas respectively they document the flank geometry and the processes readjusting the slope profile once the limiting slope angle is exceeded the grainy flank sediments in the dolomites modified by shearing and avalanching produce straight slope profiles with declivities up to 35 whereas the muddy bahamian flank sediments modified by large scale creep and rotational to translational sliding and slumping produce a concave upwards slope profile inclined at less than 4 the comparison between slope angle and sediment fabric indicates that the physical behaviour of sediments in the gravity field angle of shearing and mode of readjustment processes is linked to the composition of the slope sediment among the variables such as sea level subsidence climate plate motion and oceanographic setting windward leeward sediment fabric is suggested to be a major if not the major control on slope angle and slope curvature of carbonate platform flanks besides the recently documented tendency of carbonate sediments to build steeper slopes than siliciclastics this proposed relation sheds new light on the analysis and quantification of the variables influencing the geometry and depositional evolution of carbonate systems furthermore it provides an opportunity to deduce sediment composition from seismic lines and predict lithology prior to drilling

clinoform composition and margin geometries of a lower cretaceous carbonate platform vercors se france the concept of sequence stratigraphy uses the stratal geometries at the margins of carbonate platforms to define depositional sequences and systems tracts the aim of this study was to research if prograding purely aggrading and retrograding phases of a cretaceous carbonate platform showed differences in the composition and facies type of the slope sediments the vercors plateau in se france provides excellent outcrops to study this relationship continuous exposure of the platform to basin transition allowed direct examination of the margin geometries five successions were measured and sampled in great detail samples were thin sectioned and point counted using point count groups characterizing palaeoenvironments along the platform to basin transect the composition logs as well as the numerical analysis of the point count data both show a clear relationship between grain composition and stratal geometry the prograding and purely aggrading intervals are similar in composition as they are both relatively coarse grained and enriched in platform biota and limeclasts retreating units are relatively fine grained and rich in basinal grains small benthic foraminifers sponge spicules non carbonate grains and embedding material these observations suggest that the retreating intervals represent incipient drownings of the platform however rather than distinctly separated groups the different phases of platform development form a continuous range of variation between high platform input and high basinal input compared to the prograding units the purely aggrading intervals are relatively rich in peloids which may be suggestive of relatively low energy conditions on the platform during aggradation the compositional analysis also revealed significant variation in the frequency of ooids but these variations showed no relationship with the progradation aggradation or retreat of the platform

porites corals from crete greece open a window into late miocene 10 ma seasonal and interannual climate variability variations in the biotic composition of marine shallow water carbonates document global climatic changes however a discontinuous stratigraphic record and uncertainties regarding the ages limit the significance of shallow water carbonates as palaeoclimatic archives on geological time scales notwithstanding these deficits the environmental information stored in the skeleton of reef biota is a unique source of information that resolves seasonal to interannual climate variability in geological time application of the method to corals from carbonate rocks is usually restricted to the past 130 000yr because the aragonite skeleton undergoes rapid diagenetic alteration consequently reconstructions resolving seasonal to interannual climate variability of the more distant geological time are rare we describe exceptionally well preserved corals porites as old as late miocene 10million years from the island of crete eastern mediterranean greece stable isotope records 18 o 13 c reflect seasonal changes in sea surface temperature and symbiont autotrophy spectral analysis of a 67 yr coral 18 o record reveals significant variance at interannual time scales 2 5yr that show similarities to late quaternary eastern mediterranean climate variability supported by simulations with a complex atmospheric general circulation model coupled to a mixed layer ocean model we suggest that climate dynamics in the eastern mediterranean may reflect atmospheric variability related to the icelandic low 10 million years ago

solar influence and hydrological variability during the holocene from a speleothem annual record molinos cave ne spain this study is a contribution to the ctm2013 48639 c2 1 r opera cgl2009 10455 and hidropast cgl2010 16376 projects spanish government european regional development fund the uz2014 cie 04 project university of zaragoza the ga lc 030 2011 project aragon government la caixa and the e 28 and s 97 research groups aragon government

carbonate platform to basin correlation by means of grain composition logs an example from the vercors cretaceous se france quantitative logs of grain composition for several sections of platform top and flank of the vercors carbonate platform early cretaceous se france provide platform to basin correlation with a resolution of a few metres over an area of 70 km2 grain composition was determined by point counting thin sections point count groups that characterize palaeoenvironmental realms i e open sea platform margin were defined for the platform basin trajectory grain composition logs revealed marked peaks in the number of open sea biota and peaks in ooid abundance the peaks in open sea biota correspond to back stepping intervals and deepening upward facies successions at the platform margin these peaks probably relate to incipient drowning of the platform and may be used to delineate marine flooding surface bounded sequences peaks in ooid occurrence show no relationship with the progradation aggradation or retreat of the platform apparently the oolitic sands were not part of a facies tract that shifted up and down the platform instead they represent a depositional mode that was either on or off times of prolific ooid production and shedding probably occurred during wide but shallow submergence of the platform accompanied by suitable water chemistry peaks in both ooids and open sea biota are excellent markers for platform to basin correlation as they are recorded in successions on the platform top as well as on the flank altogether the grain composition logs show that each of the lithologically rather similar platform tongues of the vercors has a unique signature or compositional fingerprint these compositional fingerprints are most helpful in evaluating the lateral extent of different stratigraphic units in outcrops of the vercors platform the physical tracing of bedding surfaces delineate wedges of toe of slope sediments that show a conspicuous thinning towards the platform however our correlation shows that these sediment bodies are not truly basin restricted wedges but have a platform top equivalent this implies that these units were at least partly deposited during high stands of sea level that flooded the platform

periodicity in stromatolitic lamination a potential record of enso nao and sunspot in the miocene lacustrine record of the ebro basin spain abstract the spectral decomposition of time series obtained from ancient rock records can be used to study the similarity between the dynamics of present day and past climate systems a high resolution periodicity analysis of luminance and lamina thickness of lacustrine stromatolites in the ebro basin northeast of iberian peninsula reveals a significant signal of interannual and decadal climatic variability in the miocene this is one out of very few works that presents the use of spectral analysis to estimate the potential of stromatolite lamination as multiple scale recorders of climate parameters the effects of precipitation and evaporation variations on stromatolite lamination have been detected at three orders of cyclicity based on textural and high resolution stable isotope analyses c and o obtained in prior studies these analyses also revealed that the light and dark simple lamina couplets are identified with annual cycles third order isotopic cycles in the present study the spectral analysis results obtained through different paths in five stromatolite specimens reveal significant periods in the power spectrum at around 2 5 3 7 5 7 10 and 22 years these cycles can be correlated with the typical oscillation bands of different climate related agents the 2 5 year period corresponds to the quasi biennial oscillation qbo or to the biennial component of the el nino southern oscillation enso or to the north atlantic oscillation nao the 3 to 5 and 5 to 7 year bands can be linked to enso or nao variability second order isotopic cycles the 8 to 11 year bands fit the 11 year schwabe first order isotopic cycles and 22 to 23 year fit the 22 year hale sunspot cycles thus the stromatolite growth was controlled by enso nao and solar activity cycles the close relationship between these climate related agents makes it difficult to specify the dominant agent controlling the stromatolite growth nevertheless the significant periods obtained from this study within interannual 2 5 3 7 5 7 years decadal 10 22 years and even multidecadal bands 37 42 years support the existence and concurrence of enso and nao precursors during the early and middle miocene

variability of the north atlantic oscillation over the past 5 200 years the north atlantic oscillation influences climate in the arctic region and northern europe reconstructions of circulation patterns associated with the north atlantic oscillation from a 5 200 year long lake sediment record suggest that the atmospheric circulation responded to significant transitions in northern hemisphere climate

tufa forming biofilms of german karstwater streams microorganisms exopolymers hydrochemistry and calcification to understand mechanisms of tufa biofilm calcification selected karstwater stream stromatolites in germany have been investigated with regard to their hydrochemistry biofilm community exopolymers physicochemical microgradients calcification pattern and lamination in stream waters co2 degassing drives the increase in calcite saturation to maximum values of approximately 10 fold independent from the initial ca2 alkalinity ratio for the cyanobacteria of tufa biofilms a culture independent molecular approach showed that microscopy of resinembedded biofilm thin sections underestimated the actual diversity of cyanobacteria i e the six cyanobacteria morphotypes were opposed to nine different lineages of the 16s rdna phylogeny the same morphotype may even represent two genetically distant cyanobacteria and the closest relatives of tufa biofilm cyanobacteria may be from quite different habitats diatom diversity was even higher in the biofilm at the studied exemplar site than that of the cyanobacteria i e 13 diatom species opposed to 9 cyanobacterial lineages the non phototrophic prokaryotic biofilm community is clearly different from the soil derived community of the stream waters and largely composed of flavobacteria firmicutes proteobacteria and actinobacteria the exopolymeric biofilm matrix can be divided into three structural domains by fluorescence lectin binding analysis seasonal and spatial variability of these structural eps domains is low in the investigated streams as indicated by microsensor data biofilm photosynthesis is the driving mechanism in tufa stromatolite formation however photosynthesis induced biofilm calcification accounts for only 10 20 of the total ca2 loss in the streams and occurs in parallel to inorganic precipitation driven by co2 degassing within the water column and on biofilm free surfaces annual stromatolite laminae reflect seasonal changes in temperature and light supply the stable carbon isotope composition of the laminae is not affected by photosynthesis induced microgradients but from pedley h m rogerson m eds tufas and speleothems unravelling the microbial and physical controls geological society london special publications 336 83 118 doi 10 1144 sp336 6 0305 8719 10 15 00 the geological society of london 2010 mirrors that of the bulk water body only reflecting climate fluctuations tufa stromatolites with their cyanobacterial photosynthesis related calcification fabrics form an analogue to porostromate cyanobacterial stromatolites in fossil settings high in caco3 mineral supersaturation but comparatively low in dissolved inorganic carbon here the sum effect of heterotrophic exopolymerdegradation and secondary ca2 release rather decreases calcite saturation contrary to settings high in dissolved inorganic carbon such as soda lakes geobiological significance of tufa

a 600 k y record of el nino southern oscillation enso evidence for persisting teleconnections during the middle eocene greenhouse climate of central europe the el nino southern oscillation enso is a globally important factor in today s climate dynamics annually laminated oil shales from the maar lake of messel germany provide high resolution sedimentological and paleoenvironmental data of a time interval of 600 k y during the eocene greenhouse phase individual laminae consist of a light spring and summer algal layer tetraedron minimum layer and a dark winter layer composed of terrigenous background sediment four sections were selected from the core of the messel 2001 well in order to count varves and to measure total varve thickness and the thickness of light and dark laminae spectral analyses were done in order to detect possible cyclic fl uctuations in varve thickness fluctuations are signifi cant in the quasi biennial 2 1 2 5 yr and low frequency band 2 8 3 5 yr 4 9 5 6 yr thus showing that algal growth as well as the background sedimentation were controlled by enso effects at least over a time interval of 600 k y this confirms the existence of a previously postulated robust eocene enso significant peaks within a quasi decadal 10 11 yr interdecadal 17 26 yr and multidecadal band 52 yr 82 yr show either the enduring influence of more or less cyclic instabilities or the influence of solar cycles

origin and significance of lamination in lower cretaceous stromatolites and proposal for a quantitative approach stromatolite lamination is typically defined as alternation of dark and light laminae study of lower cretaceous stromatolites fromthe leza fm n spain supports this statement but recognises additional complexities in lamination that have implications for interpreting accretion processes these stromatolites are partial analogues of present day coarse grained carbonate stromatolites in the bahamas and shark bay australia that mainly form by trapping and binding carbonate sand the leza examples contain both grain rich and micrite rich laminae with scarce particles suggesting that they accreted both by trapping and not trapping grains lamination in modern and ancient coarse grained stromatolites is commonly defined by thinmicritic crusts that formed during interruptions in accretion and separate contiguous grainy laminae repetitive lamination leza examples also contain these thin hiatal crusts and locally showrepetitive lamination but their conspicuous macroscopic lamination is defined by thicker alternating grain rich and micrite rich laminae alternating lamination this indicates that although hiatuses in accretion occurred change in accretion process was the main cause of macroscopic lamination these differences in accretion processes and lamination styles between leza examples and modern coarse grained stromatolites may reflect differences in their environmental settings modern examples occur in shallow marine tidal environments whereas leza fm coarse grained stromatolites developed in ideinfluencedwater bodies in coastal wetlands that experienced fluctuations inwater salinity and hydrochemistry analysis of lamina thickness in these cretaceous stromatolites and similar published examples provides a quantitative approach to the processes that underlie stromatolite lamination

the atmospheric circulation and sea surface temperature in the north atlantic area in winter their interaction and relevance for iberian precipitation abstract the ocean surface atmosphere relationships in the north atlantic area in northern winter are empirically examined by canonical correlation analysis cca this analysis is performed from two different points of view first the connection between atmospheric circulation anomalies in terms of monthly mean sea level pressure slp and monthly standard deviation of slp slp and sea surface temperature sst anomalies of the atlantic ocean are directly examined second the air sea relationships are indirectly studied through their influence upon precipitation in an area likely to be influenced by the north atlantic the iberian peninsula the canonical correlation analysis yields two pairs of patterns that describe the coherent variations of the combined sst slp fields one pair of patterns for the sst slp fields and one pair of patterns for the slp slp fields all patterns are dominant in describing variance a lag cross correlation analysis of the time coefficients indicates that monthly mea

stromatolite lamination frequency walker lake nevada implications for stromatolites as biosignatures lamination in stromatolites considered some of the oldest fossils on earth is commonly interpreted to record the periodic response of a microbial community to daily seasonal or perhaps yearly environmental forcing but the inability to date ancient stromatolites precludes an understanding of the lamination formation processes we use high resolution 14c dating of holocene stromatolites from walker lake nevada united states to construct a record of lamination rate over the course of accretion laminae formed with a period of 5 6 1 6 yr lamination at the base of the structure 1 6 2 8 1 9 yr lamination in the middle and 4 5 0 8 yr lamination at the top of the laminated portion the predominant 4 6 yr periodicity indicates that lamination formation is likely more closely related to regional climate forcing e g el nino southern oscillation versus the typical diurnal or seasonal changes in microbial mats traditionally assumed for most ancient stromatolites thus generalizations regarding the influence of microbial mats on stromatolite lamination and the use of stromatolites as biosignatures need careful consideration

climatic conditions and hydrological change recorded in a high resolution stable isotope profile of a recent laminated tufa on a subtropical island southern japan abstract the stable isotope composition of a tufa collected on subtropical miyako island southern japan records climatic and hydrologic changes over a 15 year period 1989 2003 a total of 450 subsamples taken at increments of 0 2 mm define the high resolution isotopic profile of a 9 cm long sample the oxygen isotope values clearly exhibit cyclical changes that generally correlate with the annual lamination pattern of the tufa the observed stability of water 18o values confirms that the seasonal records of water temperature are reflected in the cyclic change of tufa 18o values the oxygen isotope profile also exhibits a long term decreasing trend that is equivalent to a 2 5 c temperature increase over the 15 year period the range of the long term change in 18o values is at least partly compensated for by a warming trend of 0 95 c seen in metrological data for miyako island however the carbon isotope profile does not vary cyclically and the values are clearly higher than for previously reported tufas from the temperate japanese mainland vegetation on miyako island which is dominated by c4 type sugar cane is largely responsible for the high 13c values of the tufa the high resolution isotopic profile provides data on the annual deposition rate which clearly increased from 1996 to 1998 when the groundwater table was raised by the construction of two underground dams near the tufa locality increased water flow from the spring activated calcite precipitation and increased the depositional rate in the upper part of the core up to 1 cm year this rate is much larger than those recorded for tufas from temperate settings in japan

eocene el nino evidence for robust tropical dynamics in the hothouse much uncertainty surrounds the interactions between the el nino southern oscillation enso and long term global change past periods of extreme global warmth exemplified by the eocene 55 to 35 million years ago provide a good testing ground for theories for this interaction here we compare eocene coupled climate model simulations with annually resolved variability records preserved in lake sediments the simulations show pacific deep ocean and high latitude surface warming of approximately 10 degrees c but little change in the tropical thermocline structure atmosphere ocean dynamics and enso in agreement with proxies this result contrasts with theories linking past and future hothouse climates with a shift toward a permanent el nino like state

carbonate deposition in a fluvial tufa system processes and products corvino valley southern italy in a multi scale approach to the study of the organic and mineral components in an active barrage type tufa system of southern italy neo formed deposits in both natural depositional sites and on inorganic substrates placed in the stream for this study were observed and compared through one year of monitoring dams and lobes representing the basic morpho facies of the deposits are composed of two depositional facies vacuolar tufa a mixture of phytoclastic and framestone tufa and stromatolitic tufa phytoherm boundstone tufa three petrographic components comprise both facies micrite and microsparite often forming peloidal to aphanitc laminar and dendrolitic fabrics and sparite which occurs as isolated to coalescent fan shaped crystals forming botryoids or continuous crusts all fabrics occurring in all depositional facies are organized into layers with a more or less well developed cyclicity which has its best expression in stromatolitic lamination the precipitation of all types of calcite with mg 1 0 to 3 2 mole and sr 0 5 to 0 8 mole takes place more or less constantly during all seasons in spite of the low saturation state of the water the saturation index range is 0 75 to 0 89 within the active depositional zone the latter extends for a few hundred microns through the external surface of the deposit the active depositional zone has a particular micro morphology composed of porous micro columns 50 to 150 m in size separated by interstitial channels mineral precipitation occurs upon both external surfaces and within internal cavities of the micro columns while further point sites of precipitation occur suspended within the masses of cyanobacterial tufts sub spherical mineral units nano spheres 10 to 20 nm in diameter are the basic biotic neo precipitate they commonly form by replacing non living degrading organic matter and at point sites along the external surface of living cyanobacterial sheaths nano spheres agglutinate to form first rod shaped aggregates 100 to 200 nm which then evolve into triads of fibres or polyhedral structures successively both triads and polyhedral solids coalesce to form larger calcite crystals mainly tetrahedrons tens of microns in size that represent the fundamental bricks for the construction of the micro columns in the active depositional zone precipitation is attributed to the presence of a widespread biofilm that occurs in the active depositional zone this is composed of a heterogeneous community comprising epilithic and endolithic filamentous cyanobacteria green algae unicellular prokaryotes actinobacteria and fungi with a variable amount of extracellular polymeric substances no precipitation takes place where the biofilm is absent indicating that the biological activities of the biofilm are crucial with its living organisms and non living organic matter basic aggregates of neo precipitates do not form in association with any one particular type of organic matter substrate but appear to be related to the seasonal temperature variation polyhedral micro crystals mainly precipitate in the colder season short triads in the intermediate seasons and long triads in the warmest conditions these three basic crystal aggregates have a petrographic counterpart respectively in the spar microspar and micrite

high resolution δ18o seasonality record in a french eemian tufa stromatolite caours somme basin abstract recent and sub recent laminated tufa stromatolites can contain high resolution 18o records of in stream temperature change fossil tufa stromatolites are therefore key targets for reconstructing terrestrial palaeoclimatic but so far only a few examples have been published in this research we studied a 2 5 cm radius tufa stromatolite from the eemian of the somme basin northern france we show 1 that high resolution sampling of fossil laminated tufas is highly reproducible we demonstrate 2 that within the limitations of the 18o method nw european eemian seasonality was essentially similar to the present day perhaps most important we show 3 that precise observations from thin section that match the position of lamina boundaries with the position of reversals in direction of 18o values are a record of the style or intensity of seasonality in this french tufa stromatolite abrupt 18o reversals do not coincide with sharp lamina boundaries rather the lamina boundaries occur where 18o values are either gradually decreasing or increasing we interpret this to be a record of abrupt changes in the growth rate accelerating in spring or early summer and decelerating in late autumn or early winter this contrasts with a published montane record from the eemian of greece where lamina boundaries and 18o reversals do coincide interpreted as more extreme seasonality caused by cessations in growth due to summer aridity or winter cold we thus propose this criterion as a method to help identify regional styles of seasonality in tufa stromatolites

temporal aspects of genetic stratigraphic units in continental sedimentary basins examples from the ebro basin spain abstract the utility of genetic stratigraphy lies with the fundamental relationship between genetic stratigraphic units and correlative intervals of geologic time while high resolution studies may reveal varying degrees of diachroneity that are associated with their bounding surfaces genetic stratigraphic units are generally viewed as chronostratigraphic in nature representing specific periods of basin fill despite the vast literature on basin analysis an evaluation of the temporal character of the boundaries between genetic stratigraphic units particularly in cases where they are conformable has not yet been undertaken the cenozoic ebro basin is a foreland basin on the north eastern iberian peninsula that provides a case for assessing the temporal character of the boundaries between genetic stratigraphic units these units are termed tecto sedimentary units following the method of tecto sedimentary analysis that is used in some continental basins in the ebro basin tecto sedimentary analysis is based on direct field observations in this work magnetostratigraphic data from four tecto sedimentary units units t4 to t7 that span rocks of lower and middle miocene age ca 1000 m thick in the central and western areas of the basin are analysed the study area contains alluvial fluvial and lacustrine deposits that were sourced from pyrenean and iberian areas whose catchments were structured during the collision of iberia and eurasia new magnetostratigraphic data from this study and previously published magnetostratigraphic data enable us to determine the ages of these tecto sedimentary unit boundaries throughout a 200 km long east west transect that extends from the basin centre to the southwestern margin the results indicate that the diachrony of the three boundaries between the miocene tecto sedimentary units through the central ebro basin is less than 0 3 ma where they are conformable this low degree of diachroneity may be attributed to the effects of allogenic largely tectonic processes that operate in the catchment areas and methodological inaccuracies these results provide empirical support to the idea that genetic stratigraphic units are bounded by surfaces that exhibit low amounts of diachroneity where they are conformities

calciturbidite composition related to exposure and flooding of a carbonate platform triassic eastern alps the compositional variation of calciturbidites pedata potschen formation deposited adjacent to the dachstein formation carbonate platform in the triassic hallstatt basin was analysed using detailed field measurements and point counting of thin sections the 35 m long section is located in the northern calcareous alps of austria six point count groups were distinguished separating basinal from platform derived input summary statistics cluster and correspondence analysis of the point count data reveals a close relationship between the biota present on the dachstein carbonate platform and the calciturbidite composition the variations in turbidite composition are attributed to fluctuations in sea level and resulting flooding and exposure of the platform which alternately created and destroyed shallow water habitats on the platform top

an atmospheric teleconnection linking enso and southwestern european precipitation abstract numerous studies have demonstrated statistical associations between the el nino southern oscillation enso and precipitation in the mediterranean basin the dynamical bases for these teleconnections have yet to be fully identified here observational analyses and model simulations are used to show how enso variability affects rainfall over southwestern europe iberia southern france and italy a precipitation index for the region named southwestern european precipitation swep is used the observational analyses show that enso modulates swep during the september december wet season these precipitation anomalies are associated with changes in large scale atmospheric fields to the west of iberia that alter low level westerly winds and onshore moisture advection from the atlantic the vorticity anomalies associated with swep variability are linked to enso through a stationary barotropic rossby wave train that emanates from the eastern equatorial pacific and propagates eastward to the atlant

temperature dependence of oxygen and clumped isotope fractionation in carbonates a study of travertines and tufas in the 6 95 c temperature range conventional carbonate water oxygen isotope thermometry and the more recently developed clumped isotope thermometer have been widely used for the reconstruction of paleotemperatures from a variety of carbonate materials in spite of a large number of studies however there are still large uncertainties in both 18o and 47 based temperature calibrations for this reason there is a need to better understand the controls on isotope fractionation especially on natural carbonates in this study we analyzed oxygen carbon and clumped isotopes of a unique set of modern calcitic and aragonitic travertines tufa and cave deposits from natural springs and wells together these samples cover a temperature range from 6 to 95 c travertine samples were collected close to the vents of the springs and from pools and tufa samples were collected from karstic creeks and a cave the majority of our vent and pool travertines and tufa samples show a carbonate water oxygen isotope fractionation comparable to the one of tremaine et al 2011 with some samples showing higher fractionations no significant difference between the calcite water and aragonite water oxygen isotope fractionation could be observed the 47 data from the travertines show a strong relationship with temperature and define the regression 47 0 044 0 005 106 t2 0 205 0 047 the ph of the parent solution mineralogy and precipitation rate do not appear to significantly affect the 47 signature of carbonates compared to the temperature effect and the analytical error the tufa samples and three biogenic calcites show an excellent fit with the travertine calibration indicating that this regression can be used for other carbonates as well this work extends the calibration range of the clumped isotope thermometer to travertine and tufa deposits in the temperature range from 6 c to 95 c

evidence for active el nino southern oscillation variability in the late miocene greenhouse climate an evaporite varve thickness record from the late miocene mediterranean reveals significant signals of interannual variability the frequency and persistence of which are compared with climatic oscillations affecting the region today sustained variability in the 2 7 yr band resembles the modern spectrum of the el nino southern oscillation enso and contrasts with that of the north atlantic oscillation nao the cyclicity of which is less stationary in frequency and less sustained in duration fully coupled climate model simulations demonstrate not only that enso variability persisted during the late miocene but also that its teleconnections may have extended further than today as high latitude climate modes weakened due to a reduced meridional temperature gradient enso appears to have exerted a stronger influence on the evaporative balance of the mediterranean in the late miocene than it does today this evidence suggests that the pacific prior to the northern hemisphere glaciation was characterized by ongoing interannual variability

compositional changes in sigmoidal carbonate clinoforms late tithonian eastern sardinia italy insights from quantitative microfacies analyses quantitative analysis of sediment composition was performed on a kilometre wide section of upper tithonian low relief up to 70 m gently inclined 3 to 15 sigmoidal carbonate clinoforms eastern sardinia to identify changes in sediment composition along the slope and across the studied succession these changes may reflect modifications of the carbonate factory and of processes responsible for sediment transport point count analysis of carbonate microfacies q mode r mode cluster analysis and spearman s rank provided a composition based classification of microfacies and highlighted relationships among sediment components the studied clinoforms are mainly composed of non skeletal grains 70 such as peloids and lithoclasts together with micrite and cements and only a limited contribution from coated grains 2 among skeletal grains 28 the greatest contribution derives from a coral stromatoporoid encruster reef that provided 15 of the components crinoids brachiopods and other along slope thriving biota provided nearly 5 of the allochems whilst fragments of molluscs gastropods bivalves and diceratids from the backreef sourced another 2 the contribution of platform interior biota is negligible 1 the association of composition based facies varies along the slope the upper slope beds consist of coral stromatoporoid grainstone to rudstone the middle slope deposits are dominated by encruster lithoclast grainstone and packstone at the lower slope peloidal lithoclastic packstone as well as brachiopod crinoidal wackestone prevail also the association of skeletal grains changes along the slope the encruster frame builder association typifies the upper slope whilst encrusters characterize the middle slope sediments in the lower slope encrusters are equally represented as the brachiopod crinoid association along slope compositional changes evidence a scarce downslope transport of frame builders and a progressive enrichment in along slope thriving biota quantitative analysis of microfacies allowed the sigmoidal clinoforms to be grouped into six sets each set gathers sigmoids with a similar sediment composition coated grains are dominant in the first set whilst they are lacking in the overlying sets reflecting a change in the carbonate factory other major compositional changes among the sets concern the relative amounts of peloids micrite frame builders corals and stromatoporoids and encrusters the contribution of peloids varies inversely to that of cements and micrite as evidenced in the third and fifth sets which respectively record the highest occurrence of peloids or cement and micrite variations in the amount of frame builders and encrusters are instead non linear high percentages of both frame builders and encrusters as recorded in the second and fifth sets are related to low amounts of peloids and lithoclasts that probably reflect episodes of reduced background sedimentation this study demonstrates that quantitative analysis of carbonate microfacies represents a powerful tool that can improve the reconstruction of the stacking pattern in carbonate slope successions both in outcrop and in subsurface settings

current tufa sedimentation in a high discharge river a comparison with other synchronous tufa records in the iberian range spain abstract the results from sedimentological isotopic and hydrochemical analyses of current tufa sedimentation conducted in a high discharge river ebron river northeastern spain 1 49 m 3 s through six month monitoring over 3 5 years are discussed in terms of the factors that control local carbonate deposition through space and time and compared with results from other synchronous tufa records in the same climatic domain the findings allow for discerning the influence of the riverbed slope hydrochemistry discharge and groundwater inputs on tufa attributes and assess the significance of tufa as archives of certain climatic events on a regional scale in the ebron river the dominant upstream karstic springs from a jurassic rock aquifer determined the river s hco 3 ca composition two river stretches were differentiated according to localised increments in both pco 2 resulting from additional groundwater inputs and so 4 content influenced by evaporite bearing units the variations in tufa s thickness through space were strongly controlled by co 2 rich springs and local slope variations the monitored sites represent four primary subenvironments with distinct sedimentary facies whose attributes suggest that 1 the tufa deposition rates in each fluvial subenvironment are mainly controlled by the co 2 outgassing intensity linked to local flow conditions and the biological substrate type and 2 stromatolites represent the thickest and most complete record the six month variations in tufa thickness and calculated calcite mass in the ebron river were controlled by temperature dependent physico chemical and biological parameters coupled with high discharge events that provoked tufa erosion the smaller deposition of the ebron river compared to two other synchronous tufa records in the iberian range is linked to 1 the absence of long areas of increased slope 2 the occurrence of significant co 2 rich groundwater springs in the middle reach and 3 the higher discharge and water depth certain high discharge events were recorded as lower deposition rates concurrent in the three rivers moreover anomalous water temperatures calculated from the calcite 18 o in the three rivers for a coincident time span support a regional anomaly in the precipitation 18 o thus the evolution of the short term tufa deposition rates and calcite 18 o composition through time can detect regional climate and hydrology changes and therefore can be robust criteria for correlation in the geological record

inter annual climate variability in europe during the oligocene icehouse abstract new sclerochronological data suggest that a variability comparable to the north atlantic oscillation nao was already present during the middle oligocene about 20 myr earlier than formerly assumed annual increment width data of long lived marine bivalves of oligocene 30 25 ma strata from central europe revealed a distinct quasi decadal climate variability modulated on 2 12 mainly 3 7 year cycles as in many other modern bivalves these periodic changes in shell growth were most likely related to changes in primary productivity which in turn were coupled to atmospheric circulation patterns stable carbon isotope values of the shells 13 c shell further corroborated the link between shell growth and food availability sub decal oscillations in the 3 7 year band in other annually resolved fossil archives were often interpreted as el nino southern oscillation enso cycles this possibility is discussed in the present study however combined shell derived proxy and numerical climate model data lend support to the interpretation of a nao like variability according to numerical climate models winter sea level pressure wslp and precipitation rate wpr across central europe during the oligocene exhibited a pattern similar to the modern nao the simulated nao index for the oligocene shows periodicities coherent with those revealed by the proxy data 2 5 6 years yet on shorter wavelengths than the modern nao biennial and 6 10 year cycles likely the different paleogeography and elevated atmospheric co 2 concentrations not only influenced the sea level pressure pattern but also the temporal variability of the nao precursor the present study represents the first attempt to characterize the inter annual climate variability in central europe during the oligocene and sets the basis for future studies on the early phase of the cenozoic icehouse climate state

late miocene sea surface salinity variability and paleoclimate conditions in the eastern mediterranean inferred from coral aragonite δ18o abstract coral skeletons are archives of chemical proxies which enable paleoenvironmental reconstructions to be made at subannual resolution stable oxygen isotope 18 o ratios of these archives reflect sea surface temperature sst as well as the 18 o composition of ambient seawater the 18 o seawater composition is not only controlled by global ice build up but river discharge and the hydrological balance of evaporation and precipitation all influencing sea surface salinity sss also play an important role in marginal seas new sub annually resolved coral 18 o data were measured and evaluated together with published data from reef coral communities of late miocene age from crete eastern mediterranean this time window is of particular importance for the paleoceanographic evolution of the mediterranean sea because it covers the successive closure of the marine gateways connecting the mediterranean with the atlantic ocean which culminated in the onset of the messinian salinity crisis msc at 5 96 ma corals were recovered from eight time slices dated by 87 sr 86 sr chronostratigraphy and cover a time window from 10 to 7 ma to monitor pre msc environmental changes the oxygen isotope composition of the reef corals porites and tarbellastraea document significant changes in mean annual 18 o as well as in mean 18 o seasonality during the late miocene tortonian and messinian coral mean annual 18 o values differ by up to 1 72 and exhibit substantial variability since ssts can be considered rather constant over the late miocene according to lithological paleobotanical and geochemical evidence the mean annual 18 o variations in the corals appear to result from changing sss during the late miocene prior to the msc this result is in contrast to earlier concepts that despite increasing isolation of the mediterranean basin starting at about 9 ma ago sss did not change until only 300 kyr prior to the deposition of the first msc evaporites mean seasonal 18 o amplitudes are lower by 0 4 in the messinian compared to those of the tortonian corals which may be due to enhanced summer evaporation spectral analyses of tortonian and messinian coral 18 o records indicate significant interannual variability with periods of 2 3 and 4 5 years such variability is similar to that found in modern records in the modern case the iceland low and azores high pressure centers influence climate in the circum mediterranean region combined with evidence from other studies the coral records of this study suggest that a similar pressure field system was already in existence in the early late miocene

a facies distribution model controlled by a tectonically inherited sea bottom topography in the carbonate rimmed shelf of the upper tithonian valanginian southern tethyan continental margin nw sicily italy the upper tithonian valanginian shallow water carbonates outcropping in the palermo mts nw sicily consist of several facies associations reflecting different depositional environments of a carbonate rimmed shelf pertaining to the southern tethyan continental margin the reconstructed depositional model based on the sedimentological features cyclic facies arrangement and biota distribution shows that a wide protected lagoon dominated by algae molluscs and scattered patch reefs was bordered landward by a tidal flat where stromatolitic algal mats were cyclically subaerial exposed and seaward by a marine sand belt and reef complex oolitic packstone grainstone lithofacies cyclically subjected to subaerial exposure suggests the occurrence of a barrier island located nearly to the lagoonal carbonate shoreline allowing the development of narrow embayments with restricted circulation in the outer platform the oolitic lithofacies of the marine sand belt pass landward into the protected lagoon where washover oolite sands occur and seaward into a high energy zone back reef apron gradually merging in the reef complex in the latter coral framestone occupied the inner sector reef flat while the facies association dominated by boundstone with ellipsactinia sp developed in the outer sectors reef wall adjacent to the fore reef and upper slope environments stratigraphic evidence associated with the recognized facies associations helped to reconstruct the geo tectonic setting of the carbonate platform where the distribution of the depositional facies along the shelf and their extension were influenced by the tectonically inherited sea bottom topography in a regime of extensional tectonics localized and thin succession of high energy prograding oolite sand belt depositional facies occupied structural highs footwall uplift while the largely diffused and thick low energy aggrading peritidal to lagoonal depositional facies developed in subsiding hanging wall the reef complex and the fore reef depositional facies exhibiting lateral migration and prograding geometries with clinoforms and downlap stratal terminations developed on a subsident stepped margin adjacent to a faulted shelf break this morphostructural setting can be comprised in a model where the tilted and faulted blocks inner platform and stepped margin outer platform paleo topography inherited from the rifting tectonics was the most important factor controlling the geometry and depositional architecture of a carbonate platform growing on the southern tethyan passive margin

systems tracts and depositional sequences in a carbonate setting a study of continuous outcrops from platform to basin at the scale of seismic lines abstract the application of sequence stratigraphy concepts to carbonates is feasible and this paper presents an example of its successful application the continuity and lateral extent of outcropping sedimentary sections observed at the scale of a seismic line from platform to basin in the southern vercors plateau western alps france confirm the validity of sequence stratigraphy concepts when applied to carbonate depositional systems from the stratal patterns displayed in outcrop we determined that carbonate lowstand systems tracts are major components in the basin even in the deep pelagic realm transgressive and highstand systems tracts are very thin a response to starvation in contrast on the shelf transgressive and highstand systems tracts are the major components carbonate lowstand and shelf margin systems tracts pinch out in the vicinity of the offlap break it clearly appears that the stratal patterns and stratal termination patterns of carbonate systems tracts especially of carbonate lowstand systems tracts are basically similar to those of siliciclastic systems tracts this study documents that carbonate platforms may provide the basin with carbonate clastics during periods of relative sea level falls and lowstand this is one of the most controversial aspects of the application of sequence stratigraphy concepts in carbonate environments a second controversial aspect of the application of sequence stratigraphy concepts to carbonate rocks is the distinction between transgressive and regressive facies cycles and depositional sequences and systems tracts this paper demonstrates that the shoreline position for carbonates which indicates the facies transgression or regression is independent of prograding or retrograding shelf breaks the stratal pattern and facies within systems tracts vary depending on the overall evolution of the accommodation space i e on their position within the transgressive and regressive cycles

pliocene pleistocene platform facies transition recorded in calciturbidites exuma sound bahamas abstract the composition of pliocene pleistocene calciturbidites of odp hole 632a exuma sound bahamas has been determined by point count analysis of thin sections in order to correlate basin platform events which influenced sedimentation strontium isotope chronostratigraphy has been used to correlate basin turbidite compositional variations to the evolution of the platform as documented by magnetostratigraphy magnetostratigraphy of great bahama bank cores shows that between 3 4 and 2 5 ma late pliocene ooids and peloids became the dominant sediments across the platform after this period the platform has been subjected to a series of subaerial exposure events this led to slow accumulation on the platform and starvation of the basin around 1 ma the platform was reflooded the transgression being followed by an increased production of ooids there is a change in calciturbidite composition in the earliest pleistocene coinciding with a regional unconformity pleistocene turbidites containing abundant skeletal material and ooids overlie pliocene early pleistocene turbidites rich in mud and skeletal material the duration of the hiatus represented by the unconformity based on 87 sr 86 sr dating is 1 0 0 7 ma prior to this hiatus sedimentation rates in the basin are an order of magnitude lower than present day accumulation rates we conclude that reflooding of the platform around 0 8 ma led to shedding of both non skeletal and skeletal sediments the change of great bahama bank from a pliocene reef rimmed skeletal platform to the present day flat topped bank dominated by non skeletal sediments can be correlated with the observed change in turbidite composition