paleoenvironmental evolution of central paratethys sea and lake pannon during the cenozoic abstract deep wells penetrated cenozoic sedimentary record of two different basins 1 oligocene retro arc basin which is buried under the 2 miocene back arc danube basin this study is focused on biotic and abiotic proxies discussed in terms of existing biostratigraphical paleoenvironmental and sedimentological data biotic proxies are represented by palynofacies and biomarkers palynomorphs aom phytoclasts toc pr ph ratio steranes abiotic proxies are represented by inorganic geochemistry e g cia sr ba ga rb th u sio2 al2o3 corg p and enrichment factors the biotic and abiotic proxies helped to refine the knowledge about the changes in redox conditions salinity depositional system and paleoclimate in the study area five temporally different environments are observed 1 sedimentation in the oligocene fragment of the retro arc hungarian paleogene basin that took place on a highly proximal part of the shelf a major dysoxic event connected with humid marsh environment is documented within last rupelian transgression ru4 ch1 ch2 2 after a hiatus the danube basin initiated with early badenian langhian stable oxic to slightly dysoxic shelf with minor salinity changes lan2 ser1 ser2 transgression 3 late badenian early serravallian dysoxic deposition similar in all basins of the central paratethys was influenced by upwelling connected with the ser2 ser3 transgression 4 sarmatian late serravallian dysoxic event associated with subsequent flooding ser3 ser4 tor1 which created shallow marginal marine environment 5 pannonian tortonian messinian sedimentation took place on an oxic shelf of the lake pannon near a fluvio deltaic source most likely represented by the paleo danube delta system

the caspian lake history biota structure and function the elongate endorheic caspian lake has a north south orientation and its main freshwater inflow the volga river enters at the shallow north end two deep basins occupy its central and southern regions these facts lead to horizontal differences in temperature salinity and ecology nutrient levels and primary production are low historically lake level has fluctuated by 6 m but on the geological timescale fluctuations of 200 m have occurred the lake formed in the late miocene first went through a long shrinking phase expanded to three times its present size in the late pliocene and repeatedly rose and fell throughout the pleistocene with corresponding freshenings and salinizations the lake surface has remained below sea level since the last pleniglacial this dynamic history led to the assemblage of a set of euryhaline biota of tethyan and freshwater origin besides baltic elements that invaded with glacial meltwater endemism is as high as in lake baikal but typical marine groups are absent because the lake is oxygenated to the bottom its biota show a vertical zonation but without a true abyssal community suggesting cat o pollution of the volga ural and kura rivers and destruction of the spawning grounds of sturgeon signalling a forthcoming collapse of the world caviar market dumont 1995 the caspian is the endorheic terminus of the volga river which contributes 80 of its total inflow 237 km3 yr on average butorin 1979 with a range of 200 450 km3 the kura river is second in line and discharges only 16 8 km yr i the ural river is third with a discharge of 8 1 km yr i lake surface area situated below sea level is close to 400 000 km2 and lake volume is 78 000 km3 or 40 of the world s continental surface water here i attempt to provide insight into the nature of the caspian ecosystem including its eventful past i outline gaps in our knowledge and suggest research for the future

population age structure techniques and ostracods applications in coastal hydrodynamics and paleoenvironmental analysis abstract ostracods are microcrustaceans that grow by moulting eight to nine instars in most cases and consequently studies of its populations need the application of some special techniques the population age structure techniques whatley in ostracoda in the earth sciences 1988 pp 245 256 are a simple statistical method to estimate paleoenvironmental conditions in fossil recent populations of ostracods for its application it is necessary to determine the percentages of each instar present in the samples studied in order to analyze the different types of population age structure histograms and their paleo environmental interpretations some potential applications are the paleo energy levels or the sedimentation rates in this paper these special techniques are applied to recent populations of the ostracod pontocythere elongata collected in littoral sediments of southwestern spain in this area the relative percentages of this species and the adult percentages are closely related with depth and consequently this species was used as a bathymetrical tracer in shallow neogene areas of the guadalquivir basin in addition a first three step multivariate analysis permits the definition of three groups closely related to the theoretical models proposed by whatley a group 1 structure or biocoenosis present either in recent low to medium energy environments located in erosional coastal stretches and neogene fair weather conditions b group 2 structure or high energy thanatocoenosis observed either in recent river mouths with groynes and neogene storm and post storm conditions and c group 3 structure or low energy thanatocoenosis characteristic of recent progradational coastal areas and present in the recent neogene deeper areas analyzed in this paper 30 40 m depth this separation is mainly controlled by intrinsic factors i e the natural growth of this species whereas the extrinsic factors i e the hydrodynamic levels are only a minor cause of the distribution of this species in the area studied

trace fossils indicating bottom aeration changes folusz limestone oligocene outer carpathians poland abstract bioturbation sequences in the pelagic folusz limestone indicate deposition under decreasing bottom aeration possibly in association with the development of microbial mats u shaped burrows diplocraterion and arenicolites exclusively were produced in the laminated limestone and they represent the only colonizers sessile suspension feeders of the oxygen deficient sediment

role of unconformity bounded units in the stratigraphy of the continental record a case study from the late miocene of the western pannonian basin hungary

late miocene and pliocene large land mammals and climatic changes in eurasia the fossil teeth of land mammals offer a powerful tool to map the regional details of past climate change in the terrestrial realm we use meanplant eaterhypsodonty molarcrownheight oflateneogenemammallocalitiestomaplatemioceneandpliocenepalaeoprecipitation on the eurasian continent and with higher temporal resolution in europe the results show that the mid latitude drying in eurasia affected thecentral parts ofthecontinentfirst and thatthedrying of western europeafter about7 8maseemstohavecoincidedroughlyintimewith a return to more humid conditions in eastern asia with a return to a drier east and more humid west in the pliocene within europe the hypsodonty based palaeoprecipitation maps suggest that the sequence from mn 9 to mn 12 ca 11 1 6 8 ma was dominated by an east west continental marine humidity gradient which gradually intensified and with a shift of dryer conditions eastwards in mn 12 ca 7 5ma thiswaspartlyoverlainfrommn13onwardsbyanorth southorientedgradient whichpersistedatleasttotheendofthepliocene the maps for both the earliest late miocene mn 9 ca 11 1 9 7 ma and the earliest pliocene mn 14 ca 4 9 4 2 ma show very low regional differentiation possibly suggesting perturbed phases in the evolution of the mammal communities analysis of hypsodonty and dietary structure of the mammalian plant eater community in europe during the entire interval shows that the miocene pliocene boundary was marked by a strong decrease in mesodont species and mixed feeders and an increase in brachydont species and omnivores in this view the shift in the latest miocene from east west to partly north south polarised hypsodonty patterns corresponds mainly to an increase in hypsodont species and grazers it seems probable that the east west gradient was primarily driven by precipitation while the north south gradient would also have been strongly influenced by temperature related effects of humidity

exsolution of ca amphibole from glaucophane and the miscibility gap between sodic and calcic amphiboles transmission and analytical electron microscopy tem aem of glaucophane from glaucophane ca amphibole bearing blueschist and eclogite from two vermont localities ecologite brook and tillotson peak and one california locality cazadero has revealed the first evidence from exsolution for the miscibility gap between sodie and calcic amphiboles the tillotson peak samples and the cazadero samples contain coarsegrained glaucophane actinolite pairs while the eclogite brook samples contain coexisting glaucophane and actinolitic hornblende ca rich glaucophanes contain abundant fine scale lamellae of ca rich amphibole these lamellae are usually oriented near 100 and overline 2 01 high resolution tem hrtem images show them to be coherent the exsolution lamellae are so narrow beyond the resolution of aem that their true ca contents are obscured by analytical contributions from the surrounding host the aem data suggest that the lamellae are either winchite or actinolite depending on the true ca concentration in most cases the exsolution lamellae have very curved interfaces and show variable orientation this is attributed to the close similarity of unit cell parameters for the two amphiboles three dimensional optimal phase boundary calculations using eplag fleet 1982 show that the observed 100 and overline 2 01 orientations are consistent with the minimization of area strain between the two lattices along the interface some samples show evidence for incipient exsolution in the form of homogeneously distributed fine scale precipitates these results suggest that ca rich glaucophanes from other glaucophane actinolite assemblages may be exsolved at the tem scale the coexisting amphiboles from eclogite brook also have been studied using the electron microprobe emp the compositional gap defined by the eclogite brook pairs is consistent with previously reported results but shows a wider break along the glaucophane actinolite pseudobinary join suggesting very limited solid solution up to temper atures of about 500 550 c the glaucophanes are relatively poor in ca except for one anomalous grain containing ca amphibole lamellae ferric iron estimated by normalization to fixed cation numbers is strongly partitioned into the actinolitic hornblende and the glaucophanes are very poor in the riebeckite component

the miocene climatic optimum evidence from ectothermic vertebrates of central europe abstract data sets of central european temporal distributions of thermophilic ectothermic vertebrates channidae varanidae chamaeleonidae cordylidae tomistomidae alligatoridae giant turtles and of north alpine foreland basin nafb distributions of ectothermic vertebrates adapted to dryer habitats albanerpeton inexpectatum salamandra sansaniensis bufo cf viridis chamaeleo caroliquarti gekkonidae varanus hofmanni bransateryx sp are analysed two main migration events of thermophilic ectotherms at 20 ma and 18 ma in the lower miocene are discerned they indicate the beginning of the miocene climatic optimum in central europe 42 45 n palaeolatitude with a lower limit of the mean annual temperature mat of 17 4 c derived from the minimal mat of their extant relatives furthermore additional palaeobotanical data and records of bauxite point to a mat of 22 c this warm and humid optimum peaked at 18 16 5 ma ottnangian karpatian and is confirmed by the coexistence of all investigated thermophilic taxa the following period early badenian is characterised by probably unchanged temperatures but a seasonality in precipitation with dry periods up to six months two major seasonal phases between 16 3 and 15 7 ma earliest early badenian and between 14 7 and 14 5 ma early middle badenian transition are indicated by an immigration of dry adapted taxa from the surrounding karst plateau to the nafb it is presumed that the tectonical reorganisation of the central paratethys realm had considerable influence on this regional humidity pattern the warm period ended abruptly between 14 0 and 13 5 ma middle late badenian transition with major regional extinction events of most of the thermophilic groups in central europe and a drop of the mat of probably more than 7 c to temperatures around 14 8 15 7 c this drop can be attributed predominantly to a decrease of more than 11 c of the minimum cold months temperature this temperature decrease marked the beginning of a climatic zonation of the european continent and is also evidenced by a progressively southward disappearance of the crocodile diplocynodon from 38 45 n palaeolatitude to 30 37 n during the middle and earliest late miocene the results correlate well with palaeobotanical data from the mid latitudes of europe and north america and the deep sea temperature curve generated from oxygen isotope ratios

strike slip tectonics in the pannonian basin based on seismic surveys at lake balaton strike slip tectonics has been the dominant style of deformation during the neotectonic pliocene and quaternary evolution of the pannonian basin main faults are exposed in the island mountains of the basin but strike slip tectonic features can be best studied in the basin fill by seismic data lake balaton offers the opportunity to carry out high to ultra high resolution seismo acoustic surveys to image stratigraphic and tectonic features in the central part of the pannonian basin several campaigns in the lake using different acquisition techniques have resulted in more than 2000 km seismo acoustic profiles with a range of resolutions and penetration depths interpretation of faults and folds shows a few kilometers wide shear zone below the lake in late miocene pliocene strata this zone can be identified as the continuation of the balatonf line known onshore to the east of the lake mapping revealed a set of duplex structures and highlighted the importance of this shear zone in the formation of lake balaton comparison of our results to analogue clay models suggests that the observed shear zone is sinistral and the horizontal displacement is on the order of hundreds of meters looking at 3d industrial seismic data to the south of the lake we suggest that the first order balaton line which represents the continuation of periadriatic line is also sinistral and characterized by small horizontal displacement of about 1 0 1 5 km during pliocene and quaternary times this indicates a 0 2 0 3 mm year average slip rate which is compatible with recent gps measurements

paleo oxygenation in tertiary epeiric seas evidence from dinoflagellate cysts the dinoflagellate cyst record from an epeiric setting in the oligocene of southwest germany exhibits major changes associated with variations in paleo oxygenation inferred from benthic foraminifera dinoflagellate cyst diversity and equitability strongly decline in the case of extreme oxygen depletion the relative abundance of the dinoflagellate cyst thalassiphora pelagica inversely correlates with the availability of benthic oxygen the t pelagica spectrum consists of different morphotypes which are considered to represent different stages within the cystal part of the t pelagica life cycle following the concept of benedek and gocht the distribution of these morphotypes is also linked to oxygen availability horizons with highest t pelagica abundances are characterized by the occurrence of t pelagica specimens representing an early stage in cyst formation a model is proposed that uses t pelagica as a proxy to assess oxygenation both at the sediment surface and in the water column the occurrence of t pelagica specimens representing an early stage in cyst formation is interpreted to reflect the extension of oxygen depletion upwards into the water column because t pelagica is an easily recognized globally distributed element of paleogene and early neogene dinoflagellate cyst assemblages the application of this model may be of importance in the reconstruction of paleo oxygenation in epeiric settings from these times its sensitivity to changes in benthic oxygenation can be as high as if not higher than that of the approach based on foraminifera moreover it is applicable to decalcified sediments

paleogeographic evolution of the late miocene lake pannon in central europe abstract the paleogeographic evolution of lake pannon within the pannonian basin is reconstructed with eight maps ranging from the middle miocene to the early pliocene the maps are based on the distribution of selected biozones and specific fossils and on complementary sedimentological and seismic information our reconstruction shows that the history of lake pannon can be divided into three distinct intervals an initial stage with low water level which resulted in isolation from the sea at about 12 ma and might have led to temporary fragmentation of the lake an interval of gradual transgression lasting until ca 9 5 ma and a long late interval of shrinkage and infilling of sediments that persisted into the early pliocene the deep subbasins of the lake formed during the transgressive interval in more basinward locations than the deep basins of the preceding sarmatian age the southern shoreline running parallel with the sava and danube rivers along the northern foot of the dinarides changed very little during the lifetime of the lake while the northern shoreline underwent profound changes

estimation of fe3 from electron microprobe analyses observations on calcic amphibole and chlorite metabasites and metagreywackes from the pelona and rand schists of southern california were analysed using three different electron microprobes for all three instruments the estimated fe3 contents of calcic amphibole chlorite and epidote are positively correlated for some samples there is an additional correlation between high estimated fe3 and the presence of magnetite these results imply that microprobe analyses can be used to discern relative differences in fe3 however microprobe data and calculations on the sensitivity of the correction procedures to systematic analytical errors indicate that estimated values of fe3 are not significant in an absolute sense thus estimates of fe3 are meaningful when comparing samples analysed with a single microprobe but must be used with caution when comparing analyses obtained on more than one probe

pervasive exsolution within the calcic amphibole series tem evidence for a miscibility gap between actinolite and hornblende in natural samples

biotic and abiotic response to palaeoenvironmental changes at lake pannons western margin central europe late miocene a multidisciplinary study was performed on a c 30 m thick limnic deltaic sequence in the styrian basin austria geophysical gamma ray activity rock magnetism geochemical organic carbon sulphur and sedimentological observations were combined with palaeontological information mainly ostracods on this base several ecological factors were deduced terrigenous influx salinity water depth and oxygenation based on integrated stratigraphy as well as on palaeomagnetic results the whole section is set to chron c5r 2r 1n 11 308 11 263 ma and covers a period of less than 45 kyr in addition to the long term record we analysed short term changes by high resolution sampling 5 mm sample interval ostracods magnetic susceptibility this 2 3 m thick interval spans in total 3500 yr with an individual sample resolution of a few years only the combination of these data permit the description of the palaeoenvironmental evolution of the section in detail at the base of the section the development of a conifer swamp on the lakeside of lake pannon is documented this almost freshwater swamp existed for some centuries before it became extinct within a few decades due to a rise of the water table the drowning is related to a transgression of lake pannon which triggered the establishment of a brackish water fauna as well as greigite formation in the lake sediments in general the ongoing transgression favoured benthic life due to increased salinity up to mesohaline conditions the high resolution ostracod and magnetic susceptibility record reflect short term fluctuations in bottom water ventilation these oscillations probably range in the order of centuries and decades and are possibly related to climatic shifts later the successive deepening of the lake resulted in a significant faunal turnover a meromictic system with a well established oxygen depleted hypolimnion developed finally the limnic phase was replaced by a prograding deltaic system where the amplified input of coarse grained material and freshwater also affected benthic life periodic changes in clay illite content were detected by the gamma ray log throughout the entire section the observed cycles 5 12 kyr of the gamma ray log may reflect a super ordinate modulation of the sedimentary record by climatically forced changes in precipitation or run off

the holocene paleolimnology of lake issyk kul kyrgyzstan trace element and stable isotope composition of ostracodes the stable isotope and trace element geochemistry of ostracode shells from lake issyk kul kyrgyzstan provide an important new paleoclimate record for central asia the n 18 o n 13 c sr ca mg ca and u ca composition of shells from the species candona neglecta found in two piston cores constrains the paleohydrology of the lake from 8700 to 1000 calendar yr before present these data combined with robust chronologies based on 16 ams 14 c dates suggest that the region went from a relatively moist climate in the early holocene to a more arid climate in the late holocene intense freshwater input presumably glacial runoff flowed into the lake from 8700 to 8300 cal yr bp as evident from the n 18 o and n 13 c values from 8300 to 6900 cal yr bp n 18 o and sr ca values indicate that the lake was relatively fresh and an open basin and u ca values suggest that the lake was well mixed with well oxygenated bottom waters there is a transition zone between 6900 and 4900 cal yr bp when n 18 o and sr ca values rapidly increase and mg ca and u ca values rapidly decrease during this period the lake evolved from an open freshwater well mixed lake to a closed more saline less well mixed lake for the remainder of the record n 18 o sr ca mg ca and u ca are relatively constant implying conditions similar to modern conditions although the slight increasing trend in sr ca may suggest an increase in salinity over this period the n 13 c values were approximately in equilibrium with atmospheric co2 in the early part of the record but became relatively negative in the later part of the record this indicates that the dominant mechanism controlling the isotopic composition of dissolved inorganic carbon shifted from exchange with the atmosphere to variations in biological productivity fl 2001 elsevier science b v all rights reserved

marine event beds and recolonization surfaces as revealed by trace fossil analysis turbidites and tempestites exhibit characteristic distributions of trace fossils to gain maximum advantage of the sedimentological and palaeoecological significance of these traces an attempt should be made to relate each trace to the associated colonization surface this approach allows traces initiated at the normal top of an event bed to be distinguished from traces that subsequently passed into the bed from a higher colonization level or were initiated on the eroded surface of the bed

evolution turnovers and spatial variation of the gastropod fauna of the late miocene biodiversity hotspot lake pannon abstract lake pannon constituted the biggest hotspot of biodiversity in the late cenozoic of europe comprising a total diversity of almost 600 gastropod species the gastropod fauna of this huge brackish system which existed over about seven million years from the late miocene to earliest pliocene within the pannonian basin system has been well documented by a great many of taxonomic works in contrast the faunal development within the lake has not been properly addressed from a statistical point of view the present investigation demonstrates that species were not homogeneously distributed across space and time generating uneven and temporally shifting patterns of species richness and degree of point endemism across the lake the faunal compositions of the time intervals analyzed were highly different contrasting simple species accumulation as suggested by the overall numbers shifting patterns of local diversity within the lake reflect changing paleo shorelines resulting from prograding river systems entering and successively diminishing the lake surface area as mainly herbivorous grazers and predominantly shallow water inhabitants the gastropods traced the moving shelf margins and vegetation belts accordingly producing the observed diversity shifts in addition each time interval is characterized by a high degree of provincialism which is considered to reflect high habitat diversity this claim is supported by the complex subaqueous topography and the presence of extensive delta plains produced by the incoming river systems a potential driver for provincialism might be the adaptation of species to distinct water depths and related parameters finally the notable differences among the faunal compositions of the upper pannonian strata and the succeeding lower viviparus beds especially regarding family level indicate an environmental turnover at the transition brackish water species are mostly replaced by typical freshwater elements indicating strong fluvial influence based on our results and latest stratigraphic data we conclude that the viviparus beds were deposited in a different environment replacing lake pannon in the southern pannonian basin in the early pliocene

facies analysis of the balta formation evidence for a large late miocene fluvio deltaic system in the east carpathian foreland abstract deposits of the balta fm are preserved in a large arcuate sediment body that covers about 60 000 km 2 and is up to 350 m thick the balta fm spans ca 5 ma as constrained by underlying tortonian bessarabian and overlying messinian early pontian paratethys strata it contains frequent terrestrial mammal fossils and fresh as well as brackish water paratethys molluscs and ostracods over the past 140 years our understanding of the sedimentary architecture of the formation and its origins has remained in its infancy which has limited insight into the evolution of the east carpathian foreland here we provide the first modern sedimentary facies analysis of the balta fm which is integrated with an extensive review of previously published local literature it is supported with micropalaeontological results and a wealth of historical borehole information we show that the balta fm has a tripartite vertical division its lowermost part is clay dominated and consists of subordinate delta front sand bodies interspersed between muds the middle unit contains separate delta plain channels or channel belts encased in thick muds these are overlain by a unit with amalgamated delta plain channel deposits with only minor amounts of associated mud the abundance of upper flow regime sedimentary structures in channel sands the absence of peats or coals and the presence of calcareous nodules suggest a strongly seasonal and relatively dry climate with a flashy discharge regime deposition of the balta fm in an area previously characterized by distal shelf and prodelta environments indicates large scale progradation triggered by high sediment volume from the uplifting carpathian orogen and enhanced by a general lowering of paratethys sea level the tripartite internal architecture of the balta fm indicates that progradation continued during deposition its wedge shaped geometry suggests that tectonic activity in the carpathians generated a 300 km wide foreland basin that allowed for significant delta plain aggradation despite of the generally regressive trend in paratethys sea level

geographic and temporal patterns in the late neogene 12 3 ma aridification of europe the use of small mammals as paleoprecipitation proxies abstract present day relations between small mammal community structure and rainfall are used to predict late neogene 12 3 ma precipitation patterns in europe and anatolia new proxy methods are developed which include regressions of mean annual and minimum monthly precipitation on diet invertivory index and locomotion habitat arboreality index a series of precipitation maps and a set of regional precipitation curves through time at 1 myr resolution are presented precipitation curves at a higher temporal resolution are constructed for the region of central spain the miocene results show the existence between 12 and 9 ma of a large wet 800 1200 mm yr zone extending from northern spain to the ukraine and characterized by the whole year penetration of large amounts of moisture far into the continent between 10 9 and 5 ma this european temperate wet zone etwz shrinks and or moves northward resulting in diachronous aridification a coeval northward migration of the subtropical high pressure zone shpz is hypothesized which is also consistent with the predicted onset of seasonal summer dryness between 10 and 8 ma the maximum extension of the etwz at 12 9 ma temporally correlates with northern hemisphere cooling suggesting that climate zonation rather than the global amount of atmospheric moisture controlled european climate at this time the main aridification at 9 8 ma could best be explained by a northward extension shifting of the subtropical high pressure zone and a transition towards less zonal circulation processes which ultimately could have been triggered by uplift of the tibetan plateau a temporary increase of precipitation at 7 6 ma is associated with renewed global cooling the lowest precipitation values less than 400 mm yr occur during the pliocene in southern and eastern europe uplift in eastern europe carpathians shrinking of the paratethys could well explain the aridification in this area and the associated sharpening of east west precipitation gradients across the continent

the stable isotope archive of lake pannon as a mirror of late miocene climate change abstract lake pannon was a long lived miocene and pliocene lake system in central europe with a famous endemic mollusc fauna the radiation of melanopsid gastropods and dreissenid bivalves has been explained simply by the opportunity to settle empty ecological niches after the extinction of marine life at the end of the middle miocene this model however fails to explain the offset in the timings of evolutionary pulses in different mollusc families stable isotope data oxygen carbon indicate a strong climatic forcing on these radiations moreover the investigated time span covers the well known vallesian optimum and subsequent crises in european terrestrial ecosystems during the late miocene the new palaeoclimatic data on the strongly changing isotope patterns of mollusc aragonite of lake pannon might shed light on the mechanisms acting during this crucial period according to the new interpretation the early lake 11 6 ma was still influenced by the latest middle miocene dry spell this phase coincided with a pronounced radiation of melanopsid gastropods during the warm early late miocene 10 ma humidity increased and culminated in a phase with high summer precipitation this caused a reorganisation of the coastal deltaic faunas suppressing the radiation of melanopsids on the other hand high nutrient loads favoured the dispersion of filter feeding dreissenids despite steadily declining salinity lake pannon remained an alkaline lake with pronounced stratification that was apparently periodically disrupted only during the humid early late miocene a separation of the isotope data into genera and ecological guilds is the prerequisite for discussing overall trends of long lived lake systems

stress induced late stage subsidence anomalies in the pannonian basin abstract subsidence sedimentation and tectonic quiescence of the pannonian basin was interrupted a few million years ago by tectonic reactivation this recent activity has manifested itself in uplift of the western and eastern flanks and continuing subsidence of the central part of the pannonian basin low to medium magnitude earthquakes of the carpathian pannonian region are generated mostly in the upper crust by reverse and wrench fault mechanisms there is no evidence for earthquakes of extensional origin 2 d model calculation of the subsidence history shows that a recent increase in magnitude of horizontal compressional intraplate stress can explain fairly well the observed quaternary uplift and subsidence pattern we propose that this stress increase is caused by the overall europe africa convergence in late pliocene consumption of subductible lithosphere at the eastern margin of the pannonian basin was completed and the lithosphere underlying the pannonian basin became locked in a stable continental frame consequently extensional basin formation has come to an end and compressional inversion of the pannonian basin is in progress

palaeoevironmental significance of ichnogenus diplocraterion torell from the permian vryheid formation of the karoo supergroup south africa abstract the late carboniferous to early jurassic karoo supergroup of south africa includes economically important coal deposits within the vryheid formation of natal the karoo sediments are almost entirely lacking in body fossils but ichnofossils are locally abundant modern sedimentological and ichnofaunal studies suggest that the north eastern part of the karoo basin was marine in this part of natal a shallow basin margin accommodated a prograding fluvio deltaic complex forming a broad sandy platform on which coal bearing sediments were deposited ichnofossils include u burrows formerly corophioides which are assigned to ichnogenus diplocraterion they are best compared with diplocraterion polyupsilon smith 1893 from crawfurdland burn scotland and are better preserved than the scottish specimens diplocraterion was made by suspension feeding animals maintaining a constant depth relationship between the vertex of the u burrow and the sediment water interface producing protrusive and retrusive forms of the burrow they preferred subtidal and intertidal environments similar ichnofaunal associations from the cretaceous of the mid western united states and the permian sydney basin of southeastern australia are unequivocably marine

a late maeotian age 6 7 6 3 ma for the enigmatic pebbly breccia unit in dsdp hole 380a of the black sea abstract various hypotheses exist on the age and origin of the so called pebbly breccia unit in the deep sea record of dsdp hole 380a of the euxinian black sea basin here we present a detailed study of diatom and nannofossil assemblages of hole 380a our diatom records show a characteristic sequence of appearance of markers species which we can correlate to the recently established bio magnetostratigraphic time frame of the zheleznyi rog section on the black sea coast of the taman peninsula russia it shows that the pebbly breccia is sandwiched between upper maeotian deposits and must have been deposited at an age between 6 7 and 6 3 ma the appearance of nannoplankton and the marine diatom association at above the pebbly breccia unit ivc suggests a short term incursion of marine conditions the age of unit ivc based on diatom data is 6 3 6 1 ma the nannoplankton record is mainly represented by species that do not have stratigraphic value the previously reported presence of ceratolithus acutus in the black sea is explained by misinterpretation of destructed elements of ascidian spicules we conclude that the pebbly breccia is not related to a desiccated black sea at messinian salinity crisis times but it corresponds to a late maeotian episode of gravitational instability in the sw black sea region

paleoecology of limnic ostracodes a review of some major topics abstract the paleoecology of limnic ostracodes is reviewd in the context of the evolution of their environment in order to understand why there is a rich ostracode fossil record we examine data such as the quantitative and qualitative distribution of living ostracode species and ostracode assemblages ways of describing and limitations importance of biological and physico chemical factors for the local accumulation of high numbers of ostracodes and diversified assemblages is emphasized we discuss the limits of extrapolations of information from ecology to paleocology we stress how paleontological knowledge can be applied to neontological studies the possibility of using holocene ostracodes as indicators of morphometric changes of lakes temperature salinity eutrophication and as a criterion of meromictic conditions is demonstrated relationships between ostracodes and the chemical environment and particularly the morphological response of the carapace are considered e g diversity and qualitative composition of assemblages and chemical stability types of carapace mineralization and ornamentation and chemistry of bottom waters these ideas developed from studies on recent material are tested for limnic cenozoic faunas in the mesozoic the main questions arising from the study of nonmarine ostracodes deal with the possible evaluation of paleosalinities in marginal lagoonal environments purbeck wealden and with evaluation of depth and hydrochemical and paleoclimatological regime in truly lacustrine intracratonic basins some peculiarities of paleozoic nonmarine ostracode assemblages are described the paleoecological cause of changes in diversity of several ostracode groups in the carboniferous and permian is emphasized

life in the sublittoral zone of long lived lake pannon paleontological analysis of the upper miocene szak formation hungary life and depositional environments in the sublittoral zone of lake pannon a large brackish paratethyan lake from the late miocene were reconstructed from fossils and facies of the szak formation this formation is exposed in several roughly coeval 9 4 8 9 ma outcrops located along strike of the paleo shelf break in northwestern hungary the silty argillaceous marl of the formation was deposited below storm wave base at 20 30 to 80 90 m water depth the abundance of benthic organisms indicates that the bottom water was usually well oxygenated interstitial dysoxia however may have occurred immediately below the sediment water interface as evidenced by occasional preservation of trace fossils such as diplocraterion the fauna comprised endemic mollusks including brackish cockles of the subfamily lymnocardiinae dreissenid mussels congeria and highly adapted uniquely large sized deep water pulmonate snails planorbids and lymnaeids ostracods were dominated by endemic species and in some cases endemic genera of candonids leptocytherids cypridids and loxoconchids fish remnants include a sciaenid otolith and the oldest skeletal occurrence of perca in europe the phytoplankton comprised exclusively endemic coccolithophorids mostly endemic dinoflagellates prevailingly spiniferites and cosmopolitan green algae the late miocene fauna and flora of lake pannon were in many ways similar to the modern caspian biota and in particular cases can be regarded as its precursor

immiscibility in ca amphiboles the literature data of nine different occurrences of coexisting mineral pairs of ca amphibole have been studied and the bulk vectors spanning the miscibiuty gap derived the additive component is always impure mg tremolite accompanied by some glaucophane and cummingtonite component the four major exchange components required to describe the compositional variation in coexisting mineral pairs are the edenite ed tschermaki ts femg j and f tschermaks fets vector trivalent iron is postulated on the basis of excess charges in the bulk vector the size of which coincides with residuals in al si fe and mg the four cations have equal sizes forming the vector ft al mg jsi j this distribution scheme is consistent for all the different occurrences and sets the basis for a comparison deviations from the scheme would radically complicate the proposed exchange pattern the ratio t ed in most mineral samples fluctuates between one and two projection of the data points in the vector space ts ed onto the line 1ed 2ts tr hbl or 1ed 1ts tr prg provides the projected tremolite content x y 7 x w or 1x j this parameter applied to coexisting pairs and plotted against the ratio mg mg fe shows some characteristic features about the miscibiuty gap in the mg pure system the solvus is almost symmetric and located in the temperature range between 800 and 870 c small amounts 0 10pfu offe in the m 4 sites and replacing ca have a dramatic effect forcing the solvus to much lower temperatures of 650 c an increase in the ratio fe fc mg causes a shift of the solvus towards more tremolitic compositions with temperatures 500 650 c the maximum asymmetry of the solvus is reached where the al poor member tremolite has a composition of x y 10 and mg mg fe 0 6 the corresponding al rich member has x 0 5 and mg mg fe 0 4 an anomaly of the solvus is observed at mg mg fe 0 8 it manifests as a kind of highly asymmetric sub gap in the tremolite rich composition range this is explained by the partitioning of fe into the single m 3 site and is characterized by a thermal hump to 650 700 c

sapphirine and ti clinohumite in ultra high pressure garnet pyroxenite and eclogite from dabie shan china sapphirine occurs as inclusions along with clinochlore enstatite talc corundum gedrite hornblende and phlogopite in millimetre size garnets from the orthopyroxenites in a 50 m thick mafic ultramafic lens in dabie shan in china the lens enclosed by felsic gneiss is made up of metre scale intercalation of garnet or thopyroxenite garnet clinopyroxenite eclogite and gneiss the equilibrium conditions of the matrix minerals as determined from the fe mg exchange equilibria between garnet and orthopyroxene and al solubility in orthopyroxene were 740 50 c temperature and over 40 kbar pressure pressures of over 28 kbar are also indicated by inclusions of quartz pseudomorphs after coesite in garnet from the eclogites phase relations among the inclusion minerals on the other hand indicate similar temperatures of 730 30 c but much lower pressures of 4 2 kbar the mafic ultramafic lens was therefore not a direct mantle fragment but was probably a low pressure cumulate in the upper crust the early granulite facies metamorphism was most likely part of a precambrian event genetically unrelated to the triassic ultra highpressure metamorphism ti clinohumite occurs in garnet orthopyroxenites as a matrix mineral and appears to have been stable during the ultra high pressure metamorphism its stability was controlled by the fluorine fugacity as documented by its reaction textures with olivine

the muddy bottom of lake pannon a challenge for dreissenid settlement late miocene bivalvia abstract the late miocene dreissenids of lake pannon a long existing eastern central european lake bear witness to two very different modes of life which allowed these bivalves to successfully settle in what appears to be an inhospitable environment one guild is restricted to the genera mytilopsis conrad 1858 and sinucongeria lorenthey 1894 these representatives are extreme r strategists which tend to produce temporal boom and bust populations during time windows of improved ecological conditions these opportunities are interpreted here to correlate with cyclic shifts in the epilimnion hypolimnion relation and the corresponding oxygenation of bottom waters events which are probably triggered by low frequency orbital forcing the second guild is composed solely of congeria partsch 1836 the paradox of the proliferation of a single species characterised by extreme size and weight in a muddy oxygen deficient lake environment avoided by nearly all other molluscs points to a hidden mechanism not accessible to other species we tentatively link this mechanism with chemosymbiosis functional morphology in interplay with a highly sulphidic over saturated interstitial water support an interpretation of the large congeria subglobosa as a successful h2s pump model

modern and holocene sublittoral ostracod assemblages crustacea from the caspian sea a unique brackish deep water environment abstract we present a reconnaissance study of sublittoral ostracods from a number of caspian sea core tops collected during a joint french russian scientific cruise in 1994 cores from between 13 and 875 m water depth the modern ostracods show little depth restriction and this reflects the hydrography of the caspian sea which maintains relatively constant conditions 5 c 13 salinity below 50 m throughout the year we also present the ostracod faunal record from a 10 m core of laminated sediments recovered from the central caspian basin at a water depth of 475 m which we believe shows repetitive quasi cyclic changes in bottom water conditions over approximately the last 14 15 000 years with a major change at about the late glacial to holocene transition the faunal record from this core illustrates the potential of these sediments for reconstructing environmental changes in the caspian region during the late quaternary to holocene the continuous occurrence of in situ benthic meiofauna throughout the core also indicates that the bottom water must have remained ventilated throughout this period although variability in the faunal assemblages may reflect long and short term changes in the strength of ventilation

widespread occurrence of greigite in the sediments of lake pannon implications for environment and magnetostratigraphy abstract lake pannon was a large lake at the southern margin of the european plate which separated from the central paratethys at the sarmatian pannonian boundary and was filled completely with sediment during the pliocene the separation produced an endemic fauna that makes classical geological correlation problematic with sediments outside the lake magnetostratigraphic correlation could potentially solve the problem and several long cores from deep drillings have been analysed for polarity information in the course of these studies primary magnetite was assumed to carry the natural remanent magnetization nrm later when outcrops of dark grey clays and marls of lake pannon were sampled for palaeomagnetic investigations of tectonic processes greigite was discovered as the carrier of the nrm at several localities this motivated a systematic study of the fine grained sediments of lake pannon in order to identify the principal carriers of the nrm to relate them to depositional environments and to assess the importance of neoformation of magnetic minerals the concentration of magnetic minerals is low in the fine grained sediments of lake pannon this made extraction of the magnetic minerals impossible so they were identified with magnetic methods magnetic experiments suggest that greigite is the most common magnetic mineral in the lake pannon sediments magnetite when it occurs is often accompanied by pyrite haematite is rare the studied sediments represent three time intervals 11 9 3 ma 8 7 ma and 6 4 ma in the 11 9 3 ma sediments greigite occurs as an original early diagenetic magnetic mineral during this period the climate was warm and humid the lake was fairly deep and stratified high organic productivity resulted in oxygen depleted bottom waters burial was rapid due to intensive erosion from the surrounding carpathian and alpine mountains magnetite bearing sediments deposited during this period do not carry a coherent palaeomagnetic signal which suggests that the magnetite was neoformed the 8 7 ma sediments were deposited in sublittoral upper delta plain and swamp environments in humid conditions they are also greigite bearing during the third investigated time period 6 4 ma the climate was arid the lake was of low salinity and was restricted to the southern part of the pannonian basin these sediments were deposited in a distal environment low sedimentation rate the characteristic magnetic mineral of this period is magnetite which most probably has a detrital origin widespread greigite which is always of diagenetic origin suspected neoformation of magnetite in the older parts of lake pannon and occasionally opposite polarities connected to greigite and magnetite when they occur together in the present study are important for magnetostratigraphic interpretation they imply that detailed magnetic mineralogical investigations and documentation of the consistency of the nrms by working on fully oriented samples are essential in magnetostratigraphic studies of molasse sediments

ghost shrimps decapoda axiidea callianassidae as producers of an upper miocene trace fossil association from sublittoral deposits of lake pannon vienna basin slovakia numerous trace fossils are described from the late miocene sediments of the bzenec formation exposed at the gbely section the vienna basin slovakia during deposition of the sediments the area was part of the large long lived brackish to freshwater lake pannon most of the trace fossils are attributed herein to egbellichnus jordidegiberti igen et ispec nov and are interpreted as burrows produced by decapod crustaceans specifically by a ghost shrimp of the family callianassidae this interpretation is based on two independent lines of evidence environmental requirements of large bioturbators and the burrow morphology itself the new ichnotaxon is distinguished from other related ichnotaxa by a combination of typically inclined roughly at an angle of 45 cylindrical burrows absence of lining and tunnels making loops or bends at approximately right angles the burrow systems at gbely document the survival of ghost shrimp long after the closure of all seaways and the origin of lake pannon as today no ghost shrimp are known from long lived brackish lakes egbellichnus from gbely is the only although indirect record of ghost shrimp from a brackish lake environment reported so far

influence of rock composition on kinetics of silica phase changes in the monterey formation santa barbara area california the diatomaceous deposits of the monterey formation along the santa barbara coast were subjected to temperatures and burial depths that increased westward after deposition as a result the silica phase in originally similar laterally equivalent strata generally changed westward from biogenous opal a to diagenetic opal ct to diagenetic quartz in individual beds at the same stratigraphic level however silica phases changed at various temperatures producing a transformation or kinetic sequence related to variations in the ratio of silica to detrital minerals compared to silica in rocks with minor detrital minerals in rocks with progressively more abundant detrital minerals 1 opal ct formed progressively later 2 the initial d spacing of opal ct was progressively smaller and 3 quartz formed progressively earlier comparison of associated calcareous dolomitic and carbonate free rocks with equal silica detrital ratios shows that carbonates did not significantly affect rates of silica diagenesis in the vast majority of rocks in carbonate bearing rocks with silica detrital ratios 8 however some 2 to 10 quartz formed early in diagenesis probably prior to opal ct formation in addition atypical quartz cherts formed locally in carbonate bearing strata by pore filling and replacement early in diagenesis possibly before widespread opal ct formation

paratethyan ostracods in the spanish lago mare more evidence for interbasinal exchange at high mediterranean sea level abstract a gigantic cascade of atlantic waters filling the deep desiccated mediterranean basin at the beginning of the pliocene has commonly been envisaged to end the messinian salinity crisis msc the mediterranean lowstand during its final lago mare phase however has long been subject to major controversy and has recently been seriously questioned again here we present high resolution ostracod distribution patterns of the msc successions in the black sea basin zheleznyi rog section russia and the mediterranean cuevas del almanzora section spain to study the origin and migration history of the lago mare ostracods we conclude that two major phases of faunal migration have taken place in the messinian the first phase corresponds to the maeotian pontian boundary interval 6 1 6 0 ma of the paratethys where mainly pannonian species suddenly invaded the black sea region the second migration event corresponds to the lago mare phase of the mediterranean when first 5 55 5 47 ma some opportunistic taxa species of cyprideis and loxoconcha genera and then 5 40 5 33 ma a more diverse assemblage of paratethyan species occupied the entire mediterranean region the spanish ostracod assemblages show a high percentage of paratethyan pontian ostracods in agreement with previously studied italian lago mare sections the similar palaeoenvironmental changes that developed roughly synchronously in the western and central mediterranean marginal basins provide more evidence for intrabasinal exchange at high water level during the final stage of the lago mare phase this indicates that the mediterranean in the latest messinian was full of water comparable to the present caspian sea and that the zanclean deluge if happened only surged some tens up to few hundred metres into the mediterranean

late miocene climate in the circum alpine realm a quantitative analysis of terrestrial palaeofloras abstract selected mega and microfloras from central and southern europe have been analysed for the time interval tortonian pannonian mn 9 12 with the coexistence approach to obtain quantitative palaeoclimate data the results give a geographically differentiated picture of the late miocene climate in the circum alpine area spatial patterns are presented in maps for mean annual temperature temperature of the coldest month temperature of the warmest month mean annual precipitation and mean annual range of temperature the obtained data show an overall warm humid and homogenous climate with very low latitudinal and longitudinal gradients there is no indication of a mediterranean type of climate palaeogeographic influences on climate patterns are evident the pannonian lake caused mild winters and a lower seasonality of temperature in the pannonian basin

third order middle miocene early pliocene depositional sequences in the prograding delta complex of the pannonian basin abstract few studies exist in the geologic literature that show the distribution of seismic facies and depositional sequences within a lacustrine basin the pannonian basin of central europe offers a unique opportunity to evaluate the influence of the eustatic signal on lacustrine deposition seismic stratigraphie and sedimentological studies indicate that the middle miocene early pliocene infill of the transtensional pannonian basin was formed by large delta systems systematic sequence stratigraphie analysis of 6000 km of reflection seismic data and more than 100 hydrocarbon exploration wells in hungary allowed the identification of twelve third order sequence boundaries in the late neogene sedimentary fill this number of depositional sequences corresponds to that of the published global eustatic curve for this time period furthermore based on magnetostratigraphic and radiometric data the ages of these depositional sequences can be tentatively correlated with the global eustatic curve the pannonian basin became isolated from the world sea at the sarmatian pannonian 11 5 ma boundary and formed a large lake the stratal patterns and sedimentary facies of individual systems tracts within the lacustrine sequences display the same characteristics as marine depositional sequences the relatively low rate of thermal subsidence and the high rate of sediment supply resulted in a good sequence resolution within the third order sequences higher order sequences can be recognized with an average duration of about 0 1 0 5 ma

new method to estimate paleoprecipitation using fossil amphibians and reptiles and the middle and late miocene precipitation gradients in europe existing methods for determining paleoprecipitation are subject to large errors 6350 400 mm or more using mammalian proxies or are restricted to wet climate systems due to their strong facies dependence paleobotanical proxies here we describe a new paleo precipitation tool based on an indexing of ecophysiological groups within herpetological communities in recent communities these indices show a highly significant correlation to annual precipitation r 2 5 0 88 and yield paleoprecipitation estimates with average errors of 6250 280 mm the approach was validated by comparison with published paleopre cipitation estimates from other methods the method expands the application of paleo precipitation tools to dry climate systems and in this way contributes to the establishment of a more comprehensive paleoprecipitation database this method is applied to two high resolution time intervals from the european neogene the early middle miocene early langhian and the early late miocene early tortonian the results indicate that both periods show significant meridional precipitation gradients in europe these being stronger in the early langhian threefold decrease toward the south than in the early tortonian twofold decrease toward the south this pattern indicates a strengthening of climatic belts during the middle miocene climatic optimum due to southern hemisphere cooling and an increased contribution of arctic low pressure cells to the precipitation from the late miocene onward due to northern hemisphere cooling