dimensions of the atlantic mediterranean connection that caused the messinian salinity crisis abstract what kind of gateway is needed to cause a salinity crisis although several reconstructions of possible atlantic mediterranean gateways are proposed for the late miocene so far the gateway that must have existed before the desiccation of the mediterranean during the messinian is unknown this study uses the theory of hydraulic control combined with the effect of bottom friction in order to find out to first order the geometrical dimensions of the connection that existed during the primary lower gypsum stage 5 97 5 61 ma of the messinian salinity crisis 5 97 5 33 ma the connecting strait is assumed to behave in a similar way as existing straits such as the strait of gibraltar or the bosphorus a salinity crisis in an enclosed basin results when its connection to the open ocean is highly restricted a strait needs to be relatively shallow narrow and or long in order to result in exchange fluxes that are of around 25 or less of the exchange at the strait of gibraltar today considering the evaporite deposits together with global sea level variations we estimate the cross section of a strait responsible of the msc to have a minimum depth of 30 45 m and a maximum width of 0 7 2 km for lengths in the range up to 500 km these dimensions are consistent with only a few of the miocene corridors identified the calculations are extended to explore the implications for sedimentary structures on the corridor floor

palaeontological evidence of communication between the central paratethys and the mediterranean in the late badenian early serravalian abstract in the middle miocene the area of present day eastern slovenia was situated at the eastern mouth of the slovenian corridor a hypothetical seaway connecting the central paratethys and the mediterranean the exact location and time of closure of a seaway between the two neighbouring marine realms are still a matter of debate we studied badenian late langhian and early serravallian calcareous nannoplankton assemblages from eastern slovenia for their palaeogeographical significance by comparing them to contemporaneous central paratethyan and mediterranean assemblages and the assemblages described in selected odp and iodp reports assemblage composition and the sequence of biostratigraphic events observed in slovenia were very similar to that in several mediterranean sites comparison with the world ocean suggests that this similarity reflects communication between the mediterranean and paratethyan populations rather than a universal trend of nannoplankton evolution late badenian assemblages from different localities within the central paratethys exhibit considerable variation with respect to the presence of discoasters considered as typical of the mediterranean and the presence of rhabdosphaera poculi and hayella challengeri considered as typical of the eastern paratethys our results suggest the mixing of mediterranean and eastern paratethyan influences throughout the entire central paratethys during the late badenian the observed variability explains how opposing views on the status of the marine connection between the central paratethys and the mediterranean in the late badenian can arise from palaeontological studies of fossil assemblages considering only a single site or a small area the gastropod species pereiraea gervaisi migrated from the mediterranean to the central paratethys where it is only known from the immediate proximity of the hypothesised slovenian corridor this supports the thesis that the communication between the two seas took place via the slovenian corridor and not some other marine connection like the hypothetical axios vardar trench

changing seas in the late miocene northern aegean a paratethyan approach to mediterranean basin evolution abstract the northern aegean region evolved during the miocene as a restricted land locked basin with small ephemeral connections to both the eastern paratethys former black sea and mediterranean its biostratigraphic data show mixed paratethys mediterranean components but the paratethys fauna has generally been neglected for chronologic reconstructions here we review this biostratigraphic data from a paratethyan perspective and present revised paleogeographic reconstructions of the northern aegean throughout the late miocene in the tortonian all sub basins show mainly fluvio deltaic terrestrial environments with a series of scattered lakes that are predominantly fed by local rivers and short lived paratethys connections the first persisting marine conditions still alternating with brackish paratethyan environments indicate a middle messinian late maeotian age 6 9 6 1 ma when the region formed a semi isolated egemar sea with multiple marine influxes the termination of marine conditions is very well documented by a marked palaeoenvironmental change to the brackish water environments that correlate to the maeotian pontian boundary 6 1 ma in eastern paratethys during the messinian salinity crisis 5 97 5 33 ma the northern aegean was a brackish water system lake egemar that formed a passageway for paratethyan overspill waters towards the mediterranean we conclude that the thick evaporites of the northern aegean domain do not reflect the classic mediterranean msc sequences but are more likely related to older badenian or maeotian salinity incursions

age of the badenian salinity crisis impact of miocene climate variability on the circum mediterranean region massive evaporites were deposited in the central european paratethys sea during the badenian salinity crisis bsc the scarcity of absolute age data has hampered a thorough understanding of these salt deposits here we present a robust chronology for this catastrophic event by 40 ar 39 ar dating of volcanic tuffs below and within the badenian salts in southern poland the onset of bsc evaporite deposition is dated at 13 81 0 08 ma and the entire event is estimated to have lasted 200 600 k y correlation to oxygen isotope records shows that the bsc evaporites were just preceded by glacial event mi 3b suggesting a causal relationship the corresponding sea level fall most likely restricted the open marine connection to the mediterranean thereby trapping the salt in the deep paratethys basins

the practicality of vertical cephalopod shells as paleobathymetric markers the depth to which an intact coiled cephalopod shell will sink with its plane of symmetry vertical is related to shell geometry equations that relate shell geometry to physical constants of pressure sea water density and gravity yield the maximum depth of stable verticality of a shell water depths calculated from the geometries of vertical shells of cymatoceras hilli shattuck drakeoceras drakei young and mortoniceras wintoni adkins from the fort worth formation upper cretaceous albian of north central texas are used to reconstruct a portion of the paleobathymetry of the east texas embayment during late fort worth time the maximum water depth to which shells with these geometries would have sunk with the plane of symmetry vertical range from 1 6 m for the least stable shell geometry d drakei to 2 6 m for the most stable shell geometry c hilli water depths were deeper than 2 6 m at localities where no vertical shells were observed and shells with the plane of symmetry horizontal showed no evidence of being reworked from the vertical orientation

final closure of panama and the onset of northern hemisphere glaciation abstract the greenland ice sheet is accepted as a key factor controlling the quaternary glacial scenario however the origin and mechanisms of major arctic glaciation starting at 3 15 ma and culminating at 2 74 ma are still controversial for this phase of intense cooling ravelo et al 1 a c ravelo d h andreasen m lyle a o lyle m w wara regional climate shifts caused by gradual global cooling in the pliocene epoch nature 429 2004 263 267 proposed a complex gradual forcing mechanism in contrast our new submillennial scale paleoceanographic records from the pliocene north atlantic suggest a far more precise timing and forcing for the initiation of northern hemisphere glaciation nhg since it was linked to a 2 3 c surface water warming during warm stages from 2 95 to 2 82 ma these records support previous models g h haug r tiedemann effect of the formation of the isthmus of panama on atlantic ocean thermohaline circulation nature 393 1998 673 676 2 claiming that the final closure of the panama isthmus 3 0 2 5 ma j groeneveld s steph r tiedemann d nurnberg d garbe schonberg the final closure of the central american seaway geology in prep 3 induced an increased poleward salt and heat transport associated strengthening of north atlantic thermohaline circulation and in turn an intensified moisture supply to northern high latitudes resulted in the build up of nhg finally culminating in the great irreversible climate crash at marine isotope stage g6 2 74 ma in summary there was a two step threshold mechanism that marked the onset of nhg with glacial to interglacial cycles quasi persistent until today

changing seas in the early middle miocene of central europe a mediterranean approach to paratethyan stratigraphy the miocene palaeogeographic evolution of the paratethys sea is still poorly constrained here we use modern mediterranean biochronology to provide an up to date overview of changing seas in central europe instead of a paratethys sea that waxed and waned with fluctuating global sea level we show that the evolution of different seas was mainly controlled by tectonic phases the early miocene ottnangian sea 18 ma was connected to the mediterranean via the rhone valley while the karpatian sea 16 5 ma was initiated by a tectonically induced marine transgression through the trans tethyan gateway in most central european basins the establishment of the badenian sea 15 2 ma triggered by subduction related processes in the pannonian and carpathian domain is significantly younger by 1 myr than usually estimated the updated palaeogeographic reconstructions provide a better understanding of the concepts of basin dynamics land sea distribution and palaeoenvironmental change in the miocene of central europe this article is protected by copyright all rights reserved

the so called cosmopolitan palaeobiogeographic distribution of tertiary nautilida of the genus aturia bronn 1838 the result of post mortem transport by oceanic palaeocurrents abstract the common view among palaeontologists that nautiloids are of little palaeobiogeographic usefulness is not justified at least for palaeozoic and mesozoic genera post mortem transport of their shells seems to have a small impact on the fossil record and the original distribution of these cephalopods appears to be preserved in the majority of cases however the genus aturia bronn 1838 nautilida known from the palaeocene to the miocene constitutes an exception like modern nautilus aturia was in all likelihood a nektobenthic cephalopod at all stages of its post embryonic development its cosmopolitan distribution is therefore surprising because many deposits bearing it are located in areas separated since the palaeocene by large oceans acting as palaeobiogeographic barriers this widespread distribution results mainly from post mortem transport of shells by oceanic palaeocurrents many sedimentological and taphonomical clues indicate that aturia shells in various neogene deposits of the aquitaine basin like many other shells of this genus in the world indisputably represent floated shells the frequency of occurrence of this transport can be explained by the singular morphology of the siphuncle of aturia this siphuncle in a dorsal position exhibits very long septal necks which represent a unique morphological feature among the post triassic nautilida there is a very small surface for the connecting ring permeable part of the siphuncle and so the post mortem filling rate of the chambers during the ascent of the shell in the water column was very limited thus shells would have reached the surface very frequently and floated long distances transported by oceanic palaeocurrents aturia shells had certainly the greatest potential for post mortem drift among the post triassic nautilida post mortem transport tends to destroy shells in sedimentary contexts where they are most likely to be deposited that is high energy shallow littoral environments however at the global scale these environments are clearly more common in the cenozoic sedimentary record visible in outcrop than in the jurassic and the cretaceous therefore the probability of these drifted tertiary shells being preserved was correspondingly greater a main distribution area of aturia populations is suggested to have been the eastern and western coasts of central north and south america this could explain the occurrence of many drifted shells in the indo pacific and on the western coasts of the atlantic ocean shells of the fossil nautilida that are indisputably nekroplanktonic provide evidence for palaeoceanographic reconstructions some aturia shells often isolated fragmentary and badly preserved have been specifically identified according to typologic criteria in addition to their stratigraphic distribution the geographical distance between aturia bearing deposits has sometimes implicitly constituted a taxonomic criterion post mortem transport of shells over long distances refutes the geographical argument a systematic revision of aturia is called for

septarian concretions internal cracking caused by synsedimentary earthquakes septarian concretions are abundant in many phanerozoic marine and marginal marine shales and mudstones they range from a few centimetres to several metres in size and are spherical or ellipsoidal in morphology in general formation by localized calcite or siderite cementation in argillaceous sediments began under less than a few metres of burial septarian cracks vary widely in shape and configuration included are networks of wide vertically radially and sometimes concentrically oriented lenticular shrinkage cracks and narrower parallel sided straight to irregular tension cracks locally accompanied by brecciation and plumose and en echelon sigmoidal cracks indicative of shear stresses crack types are intergradational many concretions exhibit multiple cracking events enclosed macrofossils and isopachous fibrous calcite cement that lines earlier formed cracks are commonly broken and displaced in some cases cracks contain injected lime mud and silt these features taken together testify that cracking involved a spectrum of responses in concretion interiors from loss of shear strength dewatering and shrinkage to brittle failure demonstrating variations in and contrasts between the rheological properties of the matrix and enclosed objects localization to interiors and outward tapering of lenticular cracks make a case for fracture partitioning and indicate that interiors were softer than exteriors at the time of shrinkage parallel sided cracks point to greater stiffness and evolving crack shape in multiply cracked concretions shows that rigidity increased with time crack orientations indicate highly variable tensile and shear stress directions within individual concretions rupture brecciation displacement of fragments loss of shear strength liquefaction and injection of unconsolidated granular sediment suggest that deformation events were rapid if not virtually instantaneous previous explanations for the internal cracking such as gas generation spontaneous chemical dehydration or localized overpressuring due to compaction seem either untenable or fail to account for the spectrum of observed features however syndepositional earthquake induced shaking of cementing bodies of varying rigidity at shallow burial depths seems to be a plausible source for the requisite short lived variable to anisotropic high stress regime inside the concretions septarian concretions may thus preserve a signature of basin seismicity as it relates to their cementation history

nautiloid shell taphonomy interpretations based on water pressure abstract nautiloid taphonomy is a difficult and widely neglected topic acting as a test of many of the assumptions made in nautiloid paleobiology phylogenetic interpretations and geological facies analysis the eocene nautiloids from the offshore london clay formation of england are considered from the perspective of flooding and implosion experiments on recent nautilus the deeper water facies are often characterized by body chambers in approximate life position one or two complete septa and various types of shell debris intermediate depth facies show intact and often vertically embedded phragmocone walls with zones of internally broken and spar cemented septa taphnomic characteristics of the former facies probably result from the implosion of shells at depths of 200 or 300 m on the seafloor while those of intermediate depth facies result from the sinking of gas filled shells to the seafloor and subsequent bending stress failure of septa left unsupported by sediment in the last whorl evidence for the removal of the body from the largely unbroken shell by octopus illustrates the potential for a biological influence on the taphonomic history of nautiloids through the phanerozoic tertiary nautiloids were probably unusually prone to extensive post mortem transport a process which tends to remove shells from the fossil record under most geological circumstances

the mid langhian flooding in the eastern central paratethys integrated stratigraphic data from the transylvanian basin and se carpathian foredeep the mid langhian badenian flooding fully reconnected the semi isolated central paratethys realm with the mediterranean and thereby drastically changed the middle miocene paleogeography of central europe due to the scattered stratigraphic record and scarcity of independent age constraints in some areas the precise age and underlying mechanism are still debated we present integrated chronostratigraphic data from five sections in the eastern part of the system to reconstruct the flooding event distal from the strait to the mediterranean by applying modern mediterranean biochronology planktonic foraminifera and calcareous nannofossils supplemented by an 40ar 39ar age on a tuff we demonstrate that the widespread open marine settings in the nw transylvanian basin were definitely installed after 14 9 ma mmi4d biozone and in most areas before 14 4 ma in the marginal study area in the se carpathian foredeep fully marine conditions likely set in slightly later 14 6 14 4 ma there short lived marine incursions into the brackish environment occurred since the latest burdigalian pre flooding phase the new ages overlap with the flooding in the majority of the central paratethys 14 9 14 4 ma and with marine overflow into the black sea 14 85 ma we suggest that the transgression was driven by subsidence of the pannonian basin by creating accommodation space and diminishing barriers between sub basins but was likely enhanced by a global sea level rise finally we speculate that the scarcity of all calcareous material in the se carpathian foredeep before the mid langhian flooding might be related to pulses of nutrient rich brackish and low ph water from the neighboring black sea basin

the eocene expansion of nautilids to high latitudes abstract a short term return of environmental conditions similar to those of the end cretaceous is marked by the reappearance of nautiloid cephalopods in the lower middle eocene la meseta formation of seymour island antarctic peninsula previous findings have been supplemented by a collections of 33 specimens the nautiloids come from several horizons the oldest sample apparently being located close to the base of the formation telm1 the most numerous coming from the cucullaea bed of telm2 and 3 a few specimens were collected from telm4 6 the la meseta formation nautiloid assemblages developed apparently in response to one of the eocene warmings and resulting transgression of a warm sea the incursion of nautiloids into southern high latitudes was roughly coeval with their expansion to the northern european seas and the succession of faunas was parallel in both regions based on the analogy with the lower eocene london clay nautiloid assemblages an estimate of bathymetric evolution of the environment can be made by the presence of a relatively shallow water form similar to cimomia imperialis close to the base of the lower middle eocene la meseta formation telm1 marks the beginning of the marine transgression the dominant la meseta species euciphoceras argentinae was apparently an analogue of the english e regale the occurrence of which in the london clay corresponds to the highest sea level stand the presence of aturia in the higher part telm4 and 5 of the la meseta formation suggests that cold oceanic waters possibly entered the area accompanied by a sea level drop the last nautiloid telm6 is an euciphoceras sp interpreted to be indicative of shallower habitat depth limits both incursion of the nautiloids to and their disappearance from the eocene high latitudes were connected with a fundamental rearrangement of the geographic distribution of particular lineages

postglacial connection of the black sea to the mediterranean and its relation to the timing of sapropel formation the opening of the connection between the mediterranean and black seas as sea level rose above the bosporus sill has long been associated with the formation of the most recent holocene sapropel deposit s1 in the eastern mediterranean but the mechanism has remained elusive we present a model for the opening of the black sea based on hydraulics arguments which demonstrates that increased freshwater flux out of the black sea began 500 1000 years after sea level reached sill depth and that the timescale for the increased freshwater flux that drained the freshwater reservoir of the black sea is about 2500 3500 years we argue that the increased freshwater discharge out of the black sea would lead to decreased deep water formation and higher productivity in the surface waters in the eastern mediterranean two conditions generally associated with sapropel formation the delay in increased freshwater flux after the opening of the black sea and the period of increased freshwater discharge appear to match the onset and duration of sapropel deposits in the eastern mediterranean

evolution of the late miocene mediterranean atlantic gateways and their impact on regional and global environmental change marine gateways play a critical role in the exchange of water heat salt and nutrients between oceans and seas as a result changes in gateway geometry can significantly alter both the pattern of global ocean circulation and associated heat transport and climate as well as having a profound impact on local environmental conditions mediterranean atlantic marine corridors that pre date the modern gibraltar strait closed during the late miocene and are now exposed on land in northern morocco and southern spain the restriction and closure of these miocene connections resulted in extreme salinity fluctuations in the mediterranean leading to the precipitation of thick evaporites this event is known as the messinian salinity crisis msc the evolution and closure of the mediterranean atlantic gateways are a critical control on the msc but at present the location geometry and age of these gateways are still highly controversial as is the impact of changing mediterranean outflow on northern hemisphere circulation here we present a comprehensive overview of the evolution of the late miocene gateways and the nature of mediterranean atlantic exchange as deduced from published studies focussed both on the sediments preserved within the fossil corridors and inferences that can be derived from data in the adjacent basins we also consider the possible impact of evolving exchange on both the mediterranean and global climate and highlight the main enduring challenges for reconstructing past mediterranean atlantic exchange

the messinian salinity crisis past and future of a great challenge for marine sciences forty years after the image of the mediterranean transformed into a giant salty lake was first conceived the fascinating history of the messinian salinity crisis msc still arouses great interest across a large and diverse scientific community early outcrop studies which identified severe palaeoenvironmental changes affecting the circum mediterranean at the end of the miocene were followed by investigations of the marine geology during the 1950s to 1970s these were fundamental to understanding the true scale and importance of the messinian event now after a long period of debate over several entrenched but largely untested hypotheses a unifying stratigraphic framework of msc events has been constructed this scenario is derived mainly from onshore data and observations but incorporates different perspectives for the offshore and provides hypotheses that can be tested by drilling the deep mediterranean basins the msc was an ecological crisis induced by a powerful combination of geodynamic and climatic drivers which had a great impact on the subsequent geological history of the mediterranean area and on the salinity of the global oceans these changed the mediterranean s connections with both the atlantic ocean and the freshwater paratethyan basins causing high amplitude fluctuations in the hydrology of the mediterranean the msc developed in three main stages each of them characterized by different palaeoenvironmental conditions during the first stage evaporites precipitated in shallow sub basins the msc peaked in the second stage when evaporite precipitation shifted to the deepest depocentres and the third stage was characterized by large scale environmental fluctuations in a mediterranean transformed into a brackish water lake the very high resolution timescale available for some late miocene intervals in the mediterranean makes it possible to consider environmental variability on extremely short time scales including in some places annual changes despite this fundamental questions remain some of which could be answered through new cores from the deepest mediterranean basins improvements in seismic imaging and drilling techniques over the last few decades make it possible to plan to core the entire basinal messinian succession for the first time the resulting data would allow us to decipher the causes of this extreme environmental change and its global scale consequences

quantitative analysis of paratethys sea level change during the messinian salinity crisis at the time of the messinian salinity crisis in the mediterranean sea i e the pontian stage of the paratethys the paratethys sea level dropped also evidence found in the sedimentary record of the black sea and the caspian sea has been interpreted to indicate that a sea level fall occurred between 5 6 and 5 5 ma estimates for the magnitude of this fall range between tens of meters to more than 1500 m the purpose of this study is to provide quantitative insight into the sensitivity of the water level of the black sea and the caspian sea to the hydrologic budget for a scenario in which the paratethys is disconnected from the mediterranean using a late miocene bathymetry based on a palaeographic map we quantify the fall in sea level the mean salinity and the time to reach equilibrium for a wide range of negative hydrologic budgets by combining our results with i estimates calculated from a set of recent global late miocene climate simulations and ii reconstructed basin salinities we are able to rule out a drop in sea level of the order of 1000 m in the caspian sea during this time period in the black sea however such a large sea level fall cannot be fully discarded

benchmark data of a changing sea palaeogeography palaeobiogeography and events in the central paratethys during the miocene abstract the reconstruction and interpretation of terrestrial ecosystems and vegetational patterns in the central european miocene have to take into account the influence of a vast landlocked water body namely the paratethys sea as a northern appendage of the early mediterranean sea it spanned a north south gradient of at least 4 latitude and has been suggested to represent some kind of palaeothermometer which reflected slight expansions or restrictions of climatic belts due to its vulnerable marine connections it was also highly susceptible to major global sea level fluctuations which are reflected in phases of endemism hence a fairly continuous record of marine nearshore assemblages throughout the miocene reflects an extraordinary interplay of sea level fluctuations changes in climate immigrations and blooms in autochthonous elements whilst biostratigraphic implications of these patterns were recognised early in palaeontology a biogeographic model is still lacking the intermingling of palaeogeographic terms with those restricted to biogeography is still commonly used a situation which can be overcome by integrating data from different biota into a new palaeobiogeographic scheme herein a data set of 1809 species level taxa gastropoda and foraminifera serves as the base for interpretations gastropods in particular turned out to be of greatest value for the differentiation of palaeobiogeographic units due to sensitive reactions to all environmental parameters and occupying a wide range of ecological niches based on the excellent gastropod record the proto danubian province early danubian p danubian p balatonian p and a proto caspian subprovince are defined the biogeographic reorganisations are associated with five major biotic events within the gastropod faunas these big five comprise four extinctions the late ottnangian extinction event loee the mid badenian extinction event mbee the badenian sarmatian extinction event bsee the sarmatian pannonian extinction event spee and one exceptional immigration origination event termed the early badenian build up event ebbe foraminifera are less valuable for palaeobiogeographic purposes in the area and time slice studied endemisms are generally lower and turn over rates less dramatic they are however very useful for stratigraphic correlations with the mediterranean and atlantic areas this fairly well calibrated marine biostratigraphy of the central paratethys serves as stratigraphic backbone and control for continental stratigraphy

the myth of the brackish sarmatian sea the biota of the 1 5 ma period of the middle miocene sarmatian of the central paratethys lack stenohaline components this was the reason to interpret the sarmatian stage as transitional between the marine badenian and the lacustrine pannonian stages however our new data indicate that brackish water conditions could not have prevailed sarmatian foraminifera molluscs serpulids bryozoans dasycladacean and corallinacean algae as well as diatoms clearly indicate normal marine conditions for the entire sarmatian during the lower sarmatian however a sea level lowstand forced the development of many marginal marine environments during the late sarmatian a highly productive carbonate factory of oolite shoals mass occurrences of thick shelled molluscs and larger foraminifera as well as marine cements clearly point to normal marine to hypersaline conditions this trend is not restricted to the western margin of the pannonian basin system but can be observed in the entire central and even eastern paratethys

post evaporitic restricted deposition in the middle miocene chokrakian karaganian of east crimea ukraine abstract in the middle miocene of east crimea gypsum evaporites formed in a shallow basin from mixed seawater nonmarine waters are overlain by marl siltstone and claystone which contain a few horizons of stromatolitic limestone the thickness and abundance of the stromatolitic horizons increase up the section in the siliciclastic portion of the section a very poor and taxonomically impoverished assemblage of benthic foraminifers jadammina nonion haynesina astrononion and eponides is recorded it is typical for a shallow water marsh or lagoon environment with a lowered salinity accordingly the brackish conditions prevailing during gypsum precipitation in east crimea continued afterwards although at the end of evaporite deposition the basin became desiccated and then it was rapidly reflooded by brackish water the impoverished biota and the occurrence of microbialites in the ptashkino section indicate extremely unfavourable conditions for most living organisms during the deposition of both the terrigenous and carbonate beds the water salinity thus was probably not only lowered but also anomalous in composition if compared to normal marine water the occurrence of carbonate stromatolitic horizons is probably related to the periodic shallowing of the basin caused by a drop of the lake water table driven by climatic factors the resulted changes allowed for a growth of the bizarre microbial serpulid communities that gave birth to most of the stromatolites in karaganian time the eastern paratethys was a huge lake isolated from the tethys this lake responded to any climatic fluctuation that in turn might lead to water level oscillations in humid climate periods the lake could be open with a surface outflow and when it was drier it could be a closed system without surface outflow gypsum evaporites and stromatolitic carbonates are clear evidence of strong evaporation in a dry climate that probably induced water level fall in the whole basin however all the time the environmental conditions were predominantly brackish even during gypsum precipitation as suggested by the chemical composition of fluid inclusions in gypsum similar conditions may be expected in other evaporite hosted predominantly brackish basins such as some messinian basins of the eastern mediterranean where some evaporites were deposited in the oligohaline to mesohaline conditions typical of the lago mare deposits

stochastic backscatter for cloud resolving models part i implementation and testing in a dry convective boundary layer abstract in simulations of deep convection with cloud resolving models the turbulence is often rather poorly resolved and the influence of the subfilter scale parameterization used in such circumstances is probably greater than in better resolved simulations therefore a study to investigate the influence of stochastic backscatter was performed and presented in two papers this first paper focuses on a description of the stochastic backscatter model and its effect on a neutral and a dry convective boundary layer the second paper then deals with two cases of deep convection the dry convective boundary layer is typical of the subcloud layer in deep convection and this study allows for influences on this layer to be investigated separately as a simple case of convection it also allows for general effects to be identified the implementation of stochastic backscatter was improved to ensure an appropriate scale of backscatter that is independent of any mesh refinements and always spatially isotropic it ca

architecture of the focsani depression a 13 km deep basin in the carpathians bend zone romania 1 in front of the se carpathians bend a very deep basin focsani depression developed in miocene to recent times an important part of its subsidence occurred after the main stages of thrusting in the carpathians apparently the basin lies in the wrong place and evolved in the wrong time in this study we constrain its architecture and evolution by analyzing a large database consisting of more than 1000 km two dimensional seismic lines and more than 60 wells around 13 km thick badenian to quaternary 16 5 myr sediments were deposited in the central part of the focsani depression during the badenian 16 5 13 myr the foreland south of trotus fault underwent ne sw directed extension and nw trending basins opened in the eastern moesian platform a nw se oriented area of subsidence stretched from the transylvania basin through the focsani depression to the se of the moesian platform while thrusting was going on in the east european scythian platform east carpathians and getic depression starting with the sarmatian 13 10 myr the focsani depression depocenter moved out of the carpathian belt coeval with the exhumation of the south and the east carpathians north of the trotus fault the basin became wider and was tilted toward the belt tilting was accompanied by dextral shearing mainly along the intramoesian and peceneaga camena faults after sarmatian times subsidence occurred practically only sse of trotus fault during meotian pontian 10 5 myr subsidence slowed down stronger pliocene quaternary subsidence is coeval with normal faulting and shearing in moesian platform the western margin of the focsani depression was then tilted eastward coeval with the exhumation of the bend zone and opening of the intramontane basins in the inner part of the belt

a quantitative analysis of the desiccation and re filling of the mediterranean during the messinian salinity crisis abstract notwithstanding the great deal of attention that the messinian evaporites of the mediterranean region have received from an observational point of view there is to date no consensus as to their mechanism of formation we aim to contribute to the investigation through a quantitative analysis of the processes of desiccation and re filling these processes are thought to have played a role in particular during the deposition of the upper part of the evaporite sequence we calculate the evolution of sea level and average salinity based on both the present day geometry and a paleogeographic reconstruction and assess the sensitivity to variations in the freshwater budget our results support previous inferences that desiccation and re filling are fast desiccation occurs on a time scale of 3 8 kyr re filling probably even faster equilibrium sea levels imply that most water has gone from the western basin while a significant water column remains in the eastern basin whether or not the eastern basin reaches the level of halite saturation depends critically on in particular the freshwater budget the fast rate of desiccation and re filling imply that temporal differences in the onset of salt precipitation between western and eastern basin and between marginal basins and basin centres are below the resolution of astronomical dating also when atlantic sea level periodically varied from below to above the level of the intervening sill the mediterranean basin will have responded with repeated desiccation and re filling fast re filling is found to require only a small connection to the atlantic ocean this in combination with the previous results suggests the mediterranean is unlikely to attain stable intermediate water levels

mediterranean outflow pump an alternative mechanism for the lago mare and the end of the messinian salinity crisis the final stage of the messinian salinity crisis msc was characterized by brackish water lago mare conditions in the intermediate and marginal basins of the mediterranean sea the presence of paratethyan former black sea fauna in these deposits has fueled long lasting controversies over the connectivity between the mediterranean and paratethys and contemporary sea level drops in both basins here we use the results of sub precessional climate simulations to calculate the freshwater budget of the mediterranean and paratethys in the messinian we show that during the msc the freshwater budget of paratethys was positive while the mediterranean was negative using these numerical constraints we propose a mediterranean outflow pump as an alternative scenario for the two most dramatic hydrological changes in the msc 1 the halite lago mare transition and 2 the pliocene reestablishment of marine conditions following the maximum msc lowstand during halite formation progressive mediterranean sea level rise resulting from african river runoff and overspill from both the atlantic and paratethys eventually reached the level of the paratethys sill a density contrast at this gateway caused dense mediterranean waters to flow into the paratethys driving a compensatory return flow this pump mechanism significantly enhanced paratethyan inflow to the mediterranean creating suitable conditions for the lago mare fauna to migrate and thrive when the mediterranean sea level finally reached the height of the gibraltar sill mediterranean outflow restarted there and enhanced exchange with the atlantic ocean during this reorganization of the circulation brackish and hypersaline waters were pumped out of the mediterranean and open marine conditions were reestablished without major flooding of the basin at the miocene pliocene boundary

timing and magnitude of miocene eustasy derived from the mixed siliciclastic carbonate stratigraphic record of the northeastern australian margin article eustasy is a key parameter to understand sedimentary sequences on continental margins and to reconstruct continental ice volume in the cenozoic but timing and magnitude of global sea level changes remain controversial especially for the miocene epoch we analyzed sediment cores recovered from the marion plateau offshore northeastern australia during ocean drilling program odp leg 194 to define the mechanisms and timing of sequence formation on mixed carbonate siliciclastic margins and to estimate the amplitude of miocene eustatic adjustments we identified sequence boundaries on seismic reflection lines significantly revised the existing biostratigraphic age models and investigated the sedimentary response to sea level changes across the marion plateau we subdivided the miocene sediments into three sequence sets comprising a set of prograding clinoforms a muddy prograding carbonate ramp evolving into an aggrading platform and a lowstand ramp evolving into a backstepping ramp we recognized eight individual sequences dated at 18 0 ma 17 2 ma 16 5 ma 15 4 ma 14 7 ma 13 9 ma 13 0 ma and 11 9 ma we demonstrate that sequences on the marion plateau are controlled by glacio eustasy since sequence boundaries are marked by increases in 18 o deep sea miocene isotope events mi1b mbi 3 mi2 mi2a mi3a mi3 mi4 and mi5 respectively which reflects increased ice volume primarily on antarctica our backstripping estimates suggest that sea level fell by 26 28 m at 16 5 ma 26 29 m at 15 4 ma 29 38 m at 14 7 ma and 53 81 m at 13 9 ma combining backstripping with 18 o estimates yields sea level fall amplitudes of 27 1 m at 16 5 ma 27 1 m at 15 4 ma 33 3 m at 14 7 ma and 59 6 m at 13 9 ma we use a similar approach to estimate eustatic rises of 19 1 m between 16 5 and 15 4 ma 23 3 m between 15 4 and 14 7 ma and 33 3 m between 14 7 and 13 9 ma these estimates can be combined into a eustatic curve that suggests that sea level fell by 53 69 m between 16 5 and 13 9 ma this implies that at least 90 of the east antarctic icesheet was formed during the middle miocene the new independent amplitude estimates are crucial as the miocene is the geologic epoch for which the new jersey margin sea level record is poorly constrained

the impact of horizontal resolution on the simulations of convective development over land summary cloud resolving models crms can be used to provide subgrid information for use in improving the representation of the development of convection in large scale models however for the crm to be of value it must itself give an accurate representation of the processes involved in the work presented here we focus on the development of convection in simulations of both shallow and deep convection over land and consider sensitivity to the horizontal resolution in a crm in both shallow and deep cases it is found to be necessary to provide adequate resolution of the sub cloud layer in order to obtain a satisfactory representation of the transport of moisture from the sub cloud layer into the free troposphere typically this requires the horizontal grid spacings to be no coarser than around one quarter of the sub cloud layer depth poorer resolution with the present model leads to signie cant delays in the development of convection while a more sophisticated subgrid scheme could reduce the sensitivity to resolution the work here has shown the resolution required to explicitly resolve the key processes using this improved resolution may be one technique for reducing the discrepancies between some model results and observations reported in earlier studies

a small coleoid cephalopod with soft parts from the lower devonian discovered using radiography during the past 50 years x ray examinations have greatly increased our knowledge of fossils modern radiographic methods x ray tubes with fine focal spots high resolution films and optimal exposure conditions have revealed details of the anatomy and general biology of ancient life as well as species and representatives of major groups hitherto unknown in the lower devonian1 5 most of this material came from the hunsriick slate where most fossils are converted to pyrite fes2 giving a good contrast in the radiographs additional image processing may reveal even more details while screening large quantities of black slate pieces i have discovered a small teuthid coleoid showing soft parts fig 1 which is the best preserved specimen i have found during 20 years of investigation this eoteuthtis elfriedae n sp is very similar to the living alloteuthis africana of the loliginidae and is one of many unusual fossils yielded by this slate3 5 only a few of which have been published this specimen of e elfridea shows that alloteuthis like animals have not changed much over the past 400 myr and means that previous concepts of the appearance of such forms must be revised

mathematical model of the late pleistocene and holocene transgressions of the black sea abstract although the late pleistocene holocene fluctuations in the black sea have been studied over many years no overall picture of this difficult natural phenomenon has as yet been developed and described moreover in the literature many researchers have provided mutually exclusive opinions about many of the processes occurring within this time interval the variation in conceptualizations about the filling of the black sea basin is explained by the following reasons 1 fluctuations of sea level in the basin were never properly studied as physical processes under conditions of increased freshwater runoff change in bosporus strait depth increase in world ocean level etc therefore some conclusions about sea level changes were not verified by appropriate calculations and have not been physically substantiated 2 the study of sea level fluctuations are conducted according to modern sea depth markers and sediment age but as the sediment was formed under varying depth conditions and could have moved relative to modern markers by the agency of various geological processes it is possible that that every core may give a different level curve 3 processes of sedimentation erosion and redeposition of sediment occurring in the sea have been studied insufficiently for this reason the same geological material has been interpreted differently by various researchers therefore mathematical modeling of sea level fluctuations based on various physical laws seems to be of great importance in this paper the value and sign for the black sea freshwater balance during the upper pleistocene holocene are discussed the hypothesis suggests that during the specified period of time the freshwater balance of the sea was always positive the sea was filled with water up to the sill mark in the bosporus strait and a river flowed into the sea of marmara along the strait bottom in the present paper geologic evidence of the river flow in the strait during the glacial age and later is presented other points of view about the sea s freshwater balance change are considered a mathematical model of the black sea basin filling with freshwater in the upper pleistocene holocene is suggested it considers that change in water volume inflowing to the black sea to be a result of ablation neotectonic processes in the strait bottom erosion and sediment accumulation black sea level change calculations have shown the following as a result of repeated increases in river runoff during glacial melting the level of the black sea started to rise from 80 m probably to 20 30 m making in the process numerous secondary fluctuations the reason for this phenomenon was the circumstance that the water volume brought by the rivers could not flow to the sea of marmara through the narrow canyon of the bosporus strait at the time therefore water collected in the sea raising its level at approximately 12 ka bp the world ocean level rose to the river surface and began to increase its depth as a result of the increase in strait depth the accumulated water in the black sea flowed out thereby lowering its level to a mark close to the ocean level according to calculations this occurred ca 11 ka bp thereafter the black sea level rose together with the ocean level water within the sea of marmara has flowed to the black sea since approximately 9 ka bp in the form of a bottom counterflow with a small time delay theoretical change in the black sea level practically corresponds to data obtained from geological investigations the theory offered here of fluctuations in black sea level is self sufficient it explains all processes from the melting of the glaciers by physical laws and does not demand the application of any additional hypotheses in the conclusion of this paper the debatable questions about the black sea s possible lowering and the subsequent flooding of the basin are considered

new imaging of the salinity crisis dual messinian lowstand megasequences recorded in the deep basin of both the eastern and western mediterranean through several examples we show that following sea level fall and marginal erosion during the messinian salinity crisis msc clastic inputs into the eastern and western mediterranean sea are not distributed evenly in space and time but are mainly limited to the lower section of the messinian salinity crisis depositional megasequence significant similarities around the basin allow us to propose a mediterranean messinian salinity crisis depositional episode that can be divided into two seismic megasequences the messinian lower megasequence mlm and the messinian upper megasequence mum their distinctive seismic facies correspond to systems tracts deposited during three main stages that represent a complete sea level cycle 1 a falling stage systems tract including mass transport deposits and forced regressive clinoforms deposited in in the early part of the falling stage and related to the increasing rate of relative sea level fall this stage is characterized by a marked shift in the depocenter towards the deep basins 2 an early lowstand characterized by massive clastic inputs from major messinian rivers the rhone nile and antalya gulf rivers or smaller river systems offshore south lebanon these clastics were deposited in an oversaturated basin as evidenced by the interfingering chaotic and transparent seismic facies of the messinian lower megasequence mlm 3 a late lowstand starting with rapid deposition of massive halite with no detrital inputs into the deep basin the upper part of the evaporites clearly onlaps the messinian erosional surface at the margins and is evidence for a transition between a late lowstand stage and an early transgressive stage these deposits belong to the messinian upper megasequence mum we interpret the transition between the two megasequences as the peak of the salinity crisis the end of the relative sea level fall and the maximum dispersal of sands into the deep mediterranean basins

timing and climatic consequences of the opening of drake passage age estimates for the opening of drake passage range from 49 to 17 million years ago ma complicating interpretations of the relationship between ocean circulation and global cooling secular variations of neodymium isotope ratios at agulhas ridge southern ocean atlantic sector suggest an influx of shallow pacific seawater approximately 41 ma the timing of this connection and the subsequent deepening of the passage coincide with increased biological productivity and abrupt climate reversals circulation productivity linkages are proposed as a mechanism for declining atmospheric carbon dioxide these results also indicate that drake passage opened before the tasmanian gateway implying the late eocene establishment of a complete circum antarctic pathway