middle miocene badenian vegetation and climate dynamics in bulgaria and poland based on pollen data abstract the miocene represents a time in eurasia when evergreen and thermophilous dominated paleogene vegetation was replaced by deciduous and temperate plants climatically it is the transition from a greenhouse to an icehouse world with the middle miocene climatic optimum as the last warm episode of earth history processes of plant evolution transformation of vegetation and coenotic structure were significantly forced by both changes in the global climate system and also by significant palaeogeographic reorganizations to give new insight in the middle miocene evolution of european ecosystems and climate dynamics we compared plant assemblages from northern bulgaria and southern poland southern paratethyan and polish lowlands realms based on palaeoecological analysis the main palaeocommunities are distinguished in hygro hydrophytic herbaceous palaeocoenoses reed marshes hygrophytic forest palaeocoenoses swamp forest and bush swamp riparian forests and mixed mesophytic forests despite some differences in taxonomic composition of these fossil floras and the proportion of individual taxa the vegetation shows similar composition and trends through time the main trend in the vegetation dynamics is a general decrease in the abundance of palaeotropic and thermophilous elements of semi evergreen forests together with these changes is a corresponding increase in the role of arctotertiary species in plant communities and these plants became dominant in the mesophytic forests changes in swamp vegetation are climatically related too but these reflect mainly local environmental dynamics and changes in inundation of the basin climate data from bulgaria and poland lack significant latitudinal climate gradient thus confirming more or less homogenous climatic conditions within europe in the middle miocene

redefinition of the amery ice shelf east antarctica grounding zone 1 new evidence is presented which shows that the amery ice shelf east antarctica extends 240 km upstream of the previously reported position we combine a digital elevation model of the amery ice shelf created from ers 1 satellite radar altimetry with measured ice thicknesses and a simple density model in a hydrostatic buoyancy calculation to map the extent of the floating ice this reveals that the ice is floating as far south as 73 2 s the result is confirmed by static gps measurements collected during three consecutive field campaigns on the amery ice shelf where the vertical component of the gps shows a clear tidal signal at 72 98 s other evidence for the grounding zone position comes from an analysis of satellite imagery mass flux calculations and ice radar data the southward extension of the grounding line substantially alters the shape and dimensions of the ocean cavity beneath the ice shelf which has implications for modeling studies of sub ice shelf processes such as basal melting and freezing ocean circulation and tides the new grounding line position will also improve geophysical studies where the computation of ocean tidal loading corrections is important for postglacial rebound estimates and correction of satellite altimetry measurements within the region

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

satellite radar interferometry for monitoring ice sheet motion application to an antarctic ice stream satellite radar interferometry sri provides a sensitive means of monitoring the flow velocities and grounding line positions of ice streams which are indicators of response of the ice sheets to climatic change or internal instability the detection limit is about 1 5 millimeters for vertical motions and about 4 millimeters for horizontal motions in the radar beam direction the grounding line detected by tidal motions where the ice goes afloat can be mapped at a resolution of 0 5 kilometer the sri velocities and grounding line of the rutford ice stream antarctica agree fairly well with earlier ground based data the combined use of sri and other satellite methods is expected to provide data that will enhance the understanding of ice stream mechanics and help make possible the prediction of ice sheet behavior

cenozoic evolution of the eastern black sea a test of depth dependent stretching models abstract subsidence analysis of the eastern black sea basin suggests that the stratigraphy of this deep extensional basin can be explained by a predominantly pure shear stretching history a strain rate inversion method that assumes pure shear extension obtains good fits between observed and predicted stratigraphy a relatively pure shear strain distribution is also obtained when a strain rate inversion algorithm is applied that allows extension to vary with depth without assuming its existence or form the timing of opening of the eastern black sea which occupied a back arc position during the closure of the tethys ocean has also been a subject of intense debate competing theories called for basin opening during the jurassic cretaceous or paleocene eocene our work suggests that extension likely continued into the early cenozoic in agreement with stratigraphic relationships onshore and with estimates for the timing of arc magmatism further basin deepening also appears to have occurred in the last 20 myr this anomalous subsidence event is focused in the northern part of the basin and reaches its peak at 15 10 ma we suggest that this comparatively localized shortening is associated with the northward movement of the arabian plate we also explore the effects of paleowater depth and elastic thickness on the results these parameters are controversial particularly for deep water basins and margins but their estimation is a necessary step in any analysis of the tectonic subsidence record stored in stratigraphy

flexure due to the messinian pontian sea level drop in the black sea paleowater depth observations suggest that a large sea level drop occurred in the black sea coeval with the messinian salinity crisis in the mediterranean sea this sea level drop would have induced vertical motions of the solid earth which influenced strait dynamics with major implications for the hydrological regime of the region using three dimensional flexure models we find that a sea level drop between 1730 and 2230 m is required to reproduce the observed paleowater depths the models predict that uplift reduced the seaway connectivity between the black sea and the mediterranean sea aegean region and between the black sea and the caspian sea stavropol highlands the miocene paratethys sea consequently became fragmented and the remaining subseas likely became more sensitive to climate change this agrees with the discovery of erosional surfaces in the caspian sea and in the pannonian basin to explain the synchronicity of the sea level lowering in the black sea and the mediterranean we speculate that a regional shift toward a drier climate occurred in response to the messinian salinity crisis in the mediterranean which led to a fall in sea level within the black sea

north and northeast greenland ice discharge from satellite radar interferometry ice discharge from north and northeast greenland calculated from satellite radar interferometry data of 14 outlet glaciers is 3 5 times that estimated from iceberg production the satellite estimates obtained at the grounding line of the outlet glaciers differ from those obtained at the glacier front because basal melting is extensive at the underside of the floating glacier sections the results suggest that the north and northeast parts of the greenland ice sheet may be thinning and contributing positively to sea level rise

on the interpretation of ice shelf flexure measurements tidal flexure in ice shelf grounding zones has been used extensively in the past to determine grounding line position and ice properties although the rheology of ice is viscoelastic at tidal loading frequencies most modelling studies have assumed some form of linear elastic beam approximation to match observed flexure profiles here we use density radar and dinsar measurements in combination with full stokes viscoelastic modelling to investigate a range of additional controls on the flexure of the southern mcmurdo ice shelf we find that inclusion of observed basal crevasses and density dependent ice stiffness can greatly alter the flexure profile and yet fitting a simple elastic beam model to that profile will still produce an excellent fit estimates of the effective young s modulus derived by fitting flexure profiles are shown to vary by over 200 depending on whether these factors are included even when the local thickness is well constrained conversely estimates of the grounding line position are relatively insensitive to these considerations for the case of a steep bed slope in our study region by fitting tidal amplitudes only and ignoring phase information elastic beam theory can provide a good fit to observations in a wide variety of situations this should however not be taken as an indication that the underlying rheological assumptions are correct

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

contribution to the glaciology of northern greenland from satellite radar interferometry interferometric synthetic aperture radar insar data from the ers 1 and ers 2 satellites are used to measure the surface velocity topography and grounding line position of the major outlet glaciers in the northern sector of the greenland ice sheet the mass output of the glaciers at and above the grounding line is determined and compared with the mass input we find that the grounding line output is approximately in balance with the input except for the three largest glaciers for which the mass loss is 4 3 km3 ice year 1 or 11 8 of the mass input along the coast we detect a systematic retreat of the grounding lines between 1992 and 1996 with insar which implies that the outlet glaciers are thinning the inferred coastal thinning is too large to be explained by a few warm summers glacier thinning must be of dynamic origin that is caused by spatial and temporal changes in ice velocity iceberg production from the glaciers is uncharacteristically low it accounts for only 8 of the ice discharge to the ocean about 55 of the ice is lost through basal melting 5 8 m ice year 1 on average from the underside of the floating glacier tongues that are in contact with warm ocean waters mass losses are highest in the first 10 km of floating ice where ice reaches the greatest depths and basal melting is 3 times larger than on average only a small increase in basal melting would suffice to disintegrate the floating glacier tongues copyright 2001 by the american geophysical union

messinian event in the black sea evidence of a messinian erosional surface in 1975 sediment cores from leg dsdp 42b sites 380a and 381 revealed a thin sediment layer in the black sea basin which points to a shallow water environment at the miocene pliocene boundary with these facts and in the wake of hypothesis of the messinian salinity crisis msc it was proposed that the black sea like the mediterranean sea suffered a desiccation period at the end of the messinian hsu k j and giovanoli f 1979 messinian event in the black sea palaeogeography palaeoclimatology palaeoecology 29 75 93 whereas the main topics of the msc in the mediterranean sea is now widely accepted the lack of evidence for a messinian erosional surface in the black sea left the debate about the messinian desiccation of this basin open until today the analysis of high resolution multi channel seismic data acquired during the blason surveys brings important new elements for this scientific debate 1 down the slope offshore the bosporus we show a clear erosional surface correlated to the top of the upper miocene shallow water environment unit of site dsdp 381 the overlying lower zanclean unit inevitably dates this erosional surface of the messinian event 2 a wide intra pontian erosional surface ipu is evidenced on the romanian shelf the ipu is characterized by a sharp decrease in the incision rate from outer deep canyons to inner shelf superficial incisions network according to the most recent paratethyan and mediterranean stratigraphic scale correlations the ipu erosional surface is considered as the analogue to the messinian erosional surface described down the slope offshore the bosporus in addition to recently discovered inland erosional signature the wide regional erosional surface we underline on the western black sea margins validates the black sea messinian desiccation hypothesis we also demonstrate that evaporative draw down of the black sea implied the installation in the basin of a negative hydrologic budget during the messinian the lack of a major messinian danube canyon on the romanian shelf supports the hypothesis of a messinian danube trapped in the dacic basin however the presence of a messinian superficial incision network connecting the location of the modern danube delta to deeply incised messinian canyons on the outer shelf ipu makes the hypothesis of a danube reaching the partially desiccated black sea still possible

ice motion of the patagonian icefields of south america 1984 2014 2015 american geophysical union all rights reserved we present the first comprehensive high resolution mosaic of ice velocity of the northern npi and southern patagonian icefields spi from multiple synthetic aperture radar and optical data collected between 1984 and 2014 the results reveal that many of the outlet glaciers extend far into the central ice plateaus which implies that changes in ice dynamics propagate far inside the accumulation area we report pronounced seasonal to interannual variability of ice motion on pio xi and jorge montt a doubling in speed of jorge montt a major slow down of o higgins significant fluctuations of upsala and a deceleration of san rafael which illustrate the need for sustained continuous time series of ice motion to understand the long term evolution of the rapidly thinning icefields the velocity product also resolves major ambiguities in glacier drainage in areas of relatively flat topography illustrating the need to combine topography and flow direction to map drainage basins

calcareous nannofossil biostratigraphy and magnetostratigraphy of the upper miocene and lower pliocene of the northern aegean orphanic gulf strimon basin areas greece abstract the transitional position of the northern aegean makes it an important area for studying the relation between the mediterranean and the eastern paratethys a chronostratigraphic framework has been obtained for the late neogene deposits along the orphanic gulf and in the strimon basin of northern greece by analysing calcareous nannofossil data and paleomagnetic results from eight sections the local formations and major lithological units have been correlated with the upper miocene and lower pliocene stages furthermore the obtained framework has facilitated a more detailed reconstruction of the effects of the messinian salinity crisis on the sedimentary record magnetostratigraphic data from the strimon basin result in an age estimate of 6 3 ma for the dafni choumnikon formation transition between normal polarity subchrons c3an 2n and c3an 1n since this late miocene age estimate corresponds closely to estimates of the maeotian pontian boundary in the eastern paratethys dacic basin we believe this transition from marine to brackish conditions corresponds to this latter boundary the gypsiferous unit in the basal part of the choumnikon equivalent beds along the orphanic gulf can then be correlated with the evaporites in the northern aegean and the lower evaporites of the mediterranean basin consequently we assume that these northern aegean evaporites have been deposited between 5 96 and 5 59 ma freshwater deposits above the evaporites are easily traceable across the orphanic gulf area as a gravel or sandstone unit topped by a travertine marker bed and have a wide lateral continuation since their position is intermediate between the shallow marine gypsum anhydrite and the more open marine clastics of the pliocene we argue that these beds correlate with the desiccation phase of the mediterranean and black sea basins this intra messinian event probably occurred between 5 59 and 5 50 ma thus predating the upper evaporites or lago mare of the mediterranean a clear recognition of the miocene pliocene boundary remains problematic in the orphanic gulf area nannofossil assemblages in the sections suggest a higher position of the local base of the pliocene than indicated by the level with the first appearance of planktonic and benthic foraminifera discontinuous occurrences of levels containing nannofossil assemblages of zone mnn11b c are found between the travertine unit and the lowermost pliocene beds representing brief marine ingressions the latter show that in the latest messinian presumably temporary connections of atlantic mediterranean waters with the northern aegean basin existed these marine ingressions likely extended further into the eastern paratethys as demonstrated by the presence of nannofossil assemblages in the middle and upper pontian of the dacic and euxinic basins the events around the miocene pliocene transition resulted in a fairly abrupt change from brackish to open marine conditions in a relative deep basin which was subject to increased rates of subsidence from the onset of evaporite deposition in the late messinian onward

radar interferometry detection of hinge line migration on rutford ice stream and carlson inlet antarctica satellite synthetic aperture radar sar interferometry is employed to map the hinge line or limit of tidal flexing of rutford ice stream and carlson inlet antarctica and detect its migration between 1992 and 1996 the hinge line is mapped using a model fit from an elastic beam theory

black sea desiccation during the messinian salinity crisis fact or fiction the late miocene messinian salinity crisis msc was an extraordinary geologic event in the mediterranean basin marked by massive salt accumulation and presumably basin desiccation as a consequence of the reduced water exchange with the atlantic ocean the discovery of a desiccation deposit in the black sea the so called pebbly breccia unit was used to claim that the black sea also became desiccated during the msc erosional features interpreted from seismic profiles of the black sea margin correlated by some to the pebbly breccia unit were used to support this hypothesis however the age of the pebbly breccia is poorly constrained and its origin and relevance to the msc subject to controversy here we present new biostratigraphic dinoflagellate cyst data from two key sedimentary successions located in a deep and a marginal setting of the black sea basin these records demonstrate that the pebbly breccia predates the mediterranean water level drop during the msc we argue that the presumed erosional features in the black sea basin are not related to the msc and likely represent an older miocene event

remote sensing of glacier and ice sheet grounding lines a review abstract the precise positioning and long term monitoring of the grounding line forming the boundary between grounded and floating ice of marine ice sheets and tidewater glaciers is critical for assessing ice sheet glacier stability ice sheet glacier mass balance calculations and numerical ice modelling however mapping of the grounding line is a challenging task since it is a subglacial and transient feature remote sensing techniques do not map the grounding line directly but locate surface features in the grounding zone that serve as proxies for the true grounding line position the large variety of methods products and publications as well as an inconsistent use of terminology additionally complicate the topic we present the first detailed review of existing remote sensing techniques and data for grounding line mapping benefits and limitations of the different techniques and data sources are discussed and illustrated with examples we identify a present tradeoff between accuracy and both spatial coverage and temporal resolution of the derived grounding line products rather new methods like sentinel 1 sar synthetic aperture radar differential range offset tracking drot and pseudo crossover radar altimetry pcra offer the potential for recent measurements and to fill gaps in some areas nevertheless there is a high demand of new spaceborne radar sensors that provide time series of very short repeat pass data to enable regular grounding line monitoring with most accurate differential sar interferometry dinsar on a continental scale

sea bed depths at the mouth of rutford ice stream antarctica seismic measurements of ice and water column thickness have been made on rudard ice stream where it joins the ronne ice shelf assuming that the ice is in hydrostatic equilibrium these values have been used to calculate sea bed elevations a sea bed trough more than 2 km below sea level along the western margin continues downstream from the grounded to the floating ice

organic petrology mineralogy and depositional environment of the kipra lignite seam maritza west basin bulgaria abstract the aim of the present study is to provide additional information about the properties and depositional environment of the kipra lignite seam which was deposited during the regressive stage of development of the maritza west basin petrographical and mineralogical data along with ash yields and sulphur contents of 24 samples from a seam profile have been used to study the vertical variation of the depositional settings during peat accumulation and subsequent coalification the kipra lignite is characterized by high ash yields and sulphur contents it formed in a rheotrophic low lying mire with alkaline ph value vegetation with low preservation potential dominated within the palaeomire during peat formation frequent changes of the water level controlled the depositional environment during the deposition of units 1 and 2 high water energy caused the transportation of high amounts of inorganic material into the mire resulting in the formation of weakly gelified mineral rich lignite the organic matter from units 3 and 4 is characterized by enhanced gelification which probably reflects the decreasing energy of the system good positive correlation between sulphur contents and the gi values was established in units 4 indicating that the gelification of the tissues was probably mainly controlled by the bacterial activity in contrast the gelification of the samples from unit 3 of the kipra seam was probably governed by the redox conditions the organic matter deposited under relatively wet conditions in which the thermal and oxidative destruction of the tissues was limited a variety of major minor and accessory minerals are present in maritza west lignite the mineral composition is dominated mainly by pyrite gypsum and calcite and to a lesser extent limonite quartz kaolinite montmorillonite illite chlorite and plagioclase jarosite hematite halloysite mica k feldspar aragonite siderite and dolomite were also determined in very low concentrations these minerals formed syngenetically and epigenetically the syngenetic stage is characterized mainly by the formation of pyrite carbonates silicates and sulphates whereas the fe oxyhydroxides partially the carbonates and almost all silicates are of detrital origin during the epigenetic stage carbonates sulphates clay minerals pyrite and fe oxyhydroxides were formed alteration products like gypsum jarosite limonite chlorite kaolinite illite mica and calcite were generated due to the transformation of detrital and authigenic minerals

ephemeral grounding as a signal of ice shelf change interferometric synthetic aperture radar insar observations of ice shelf tidal deformation reveal the wide transition between grounded and floating ice as well as local areas where the ice shelf is only grounded at low tide a condition that we call ephemeral grounding ephemeral grounding creates a subtle local disturbance on the vertical motion field of the ice shelf surface in response to changes in occanic tide which is detected with millimetric precision using insar these ice shelf features are however not expected to produce a noticeable disturbance on the ice shelf velocity field to illustrate the influence of ephemeral grounding on ice shelf creep flow we use a finite element model in which ephemeral grounding is incorporated through a variable basal friction coefficient the results show that while ice rises permanently grounded areas have a pronounced influence on the ice shelf velocity field areas of ephemeral grounding have a vanishingly small influence what is thus of most interest is the capacity for observations of ephemeral grounding to reveal subtle changes in ice shelf thickness over time we discuss an example in the thwaites glacier area west antarctica where multi year data show how ice rises become ephemeral grounding and subsequently disappear this result is consistent with the grounding line retreat and ice thinning of thwaites glacier

tidal motion ice velocity and melt rate of petermann gletscher greenland measured from radar interferometry over a floating glacier ice tongue or an ice shelf the glacier motion measured by a single repeat pass radar interferogram is difficult to analyze because the long term steady motion of the ice is intermixed with its cyclic downward motion induced by tidal forcing multiple interferograms and a quadruple difference technique are necessary to separate the tidal signal from the long term steady motion of the ice an example of application of this technique is given here using ers 1 radar images of petermann gletscher a major outlet glacier of northern greenland tidal displacements are measured with 5 mm statistical noise the long term ice velocity is measured with a precision of 1 m a 1 the inferred tidal displacements agree well with model predictions from a fixed elastic beam with an elastic damping factor of 0 47 0 01 km 1 the hinge line is mapped with a precision of 20 80 m combining the interferometric ice velocities with ice thickness data the glacier ice discharge is calculated at and below the hinge line at the hinge line the ice flux is 12 1 1 km3 a 1 at the ice front calf ice production is only 0 59 km3 a 1 meaning that 95 of the ice that crosses the grounding line melts before it reaches the calving front assuming steady state conditions the melt rate of the glacier tongue averages 12 1 m a 1 with peak values exceeding 20 m a 1 near the hinge line this high melt rate cannot be accommodated by surface ablation alone only about 2 3 m a 1 and is attributed to pronounced basal melting of the ice tongue basal melting often assumed to be negligible in greenland is the dominant process of mass release from the floating section of petermann gletscher

glaciological studies on rutford ice stream antarctica rutford ice stream drains part of the west antarctic ice sheet into ronne ice shelf much of the drainage basin has a bed well below sea level and is therefore an area which could undergo substantial change if a climatic warming were to cause sustained thinning of ronne ice shelf snow accumulation data suggest that an accumulation rate of 0 51 0 12 mg m 2 yr 1 is required for balance an extensive ice movement survey network was established across the grounding line in 1978 1980 and was extended for more than 100 km upstream in 1984 1986 velocities at five sites have been calculated using doppler satellite position measurements when the velocities are combined with cross sectional areas of the ice stream measured by radio echo sounding mass flux figures show that drag at the sidewalls and on the base must decrease downstream toward the grounding line the increasing influence of buoyancy forces on ice stream motion is also shown by the steady rise in the ratio of bedrock depth to ice thickness going downstream along the network below the grounding line that was found to cross the middle part of the earlier network is a zone stretching for a further 100 km where it can now be shown that the ice stream is intermittently grounded in these grounded areas the glacier bed is raised with respect to the surrounding seabed and forms eskerlike features surface elevations over the grounded areas are less than 30 m above those needed for hydrostatic equilibrium

petroleum geology of the black sea abstract the black sea comprises two extensional basins formed in a back arc setting above the northward subducting tethys ocean close to the southern margin of eurasia the two basins coalesced late in their post rift phases in the pliocene forming the present single depocentre the western black sea was initiated in the aptian when a part of the moesian platform now the western pontides of turkey began to rift and move away to the south east the eastern black sea probably formed by separation of the mid black sea high from the shatsky ridge during the palaeocene to eocene subsequent to rifting the basins were the sites of mainly deep water deposition only during the late miocene was there a major sea level fall leading to the development of a relatively shallow lake most of the margins of the black sea have been extensively modified by late eocene to recent compression associated with closure of the tethys ocean gas chromatography mass spectrometry and carbon isotope analysis of petroleum and rock extracts suggest that most petroleum occurrences around the black sea can be explained by generation from an oil prone source rock of most probably late eocene age although a wider age range is possible in the basin centres burial history modelling and source kitchen mapping indicate that this unit is currently generating both oil and gas in the post rift basin a palaeozoic source rock may have generated gas condensate in the gulf of odessa in bulgarian waters the main plays are associated with the development of an eocene foreland basin kamchia trough and in extensional structures related to western black sea rifting the latter continue into the romanian shelf where there is also potential in rollover anticlines due to gravity sliding of neogene sediments in the gulf of odessa gas condensate has been discovered in several compressional anticlines and there is potential in older extensional structures small gas and oil discoveries around the sea of azov point to further potential offshore around the central azov high in offshore russia and georgia there are large culminations on the shatsky ridge but these are mainly in deep water and may have poor reservoirs there are small compressional structures off the northern turkish coast related to the pontide deformation these may include eocene turbidite reservoirs the extensional fault blocks of the andrusov ridge mid black sea high are seen as having the best potential for large hydrocarbon volumes but in 2200 m of water

recurrent phases of drought in the upper miocene of the black sea region abstract since the miocene the black sea proved to be highly sensitive to fluctuations in the hydrological cycle because of its recurrent restricted connections with the open ocean and the location between the dry mediterranean and more humid higher northern latitudes although the black sea formed one of the foci of the 1975 deep sea drilling project leg 42b robust tools to reconstruct past changes in its hydrological cycle were lacking at that time here we revisit the sedimentary succession hole 380a and determined compound specific carbon 13c hydrogen isotope ratios d of terrestrial and aquatic biomarkers to investigate changes in the hydrological budget of the black sea during the late miocene the 13c and d isotopic composition of n alkanes as well as alkenones and palynology indicate large environmental changes in the black sea and or in the sources of the water entering the black sea during the late miocene the d of alkenones showing an enrichment of more than 80 at the end of the miocene implies a major shift in basin hydrology possibly resulting in severely increased salinity these changes in d composition of the alkenones coincide with both with sharp shifts in reconstructed sea surface temperature and palynological assemblages two intervals with negative water budget were identified most likely caused by enhanced evaporation the older and longer dry evaporative phase predates the maeotian pontian boundary regional stages at 6 1 ma the younger drying phase corresponds to the messinian salinity crisis this shift to highly evaporative conditions is related to a similar shift previously observed in a messinian pontian sedimentary succession from the taman peninsula russia these recurrent dry phases likely reflect regional climatic shifts over a significantly larger area around the black sea area during the upper miocene

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

late oligocene and miocene climate and vegetation in the eastern paratethys area northeast bulgaria based on pollen data abstract the results of palynological studies of the oligo miocene in the western part of the euxinian basin eastern paratethys are based on the analysis of 57 samples from core c 136a drilled near the town of balchik varna district some samples were barren or contained very little pollen and were not included in the analysis quantitative data are thus confined to 26 polleniferous samples we present results for the upper oligocene as well as the tarkhanian karaganian bessarabian and chersonian stages of the middle to upper miocene mixed deciduous forests were widespread during the time period studied swamp forests are also recorded with distribution maxima observed in the oligocene and in the bessarabian the widest extent of herbaceous vegetation is recorded in the late bessarabian and chersonian when it occupied open landscapes after a marine regressional phase the climatic data reconstructed by the coexistence approach indicate mean annual temperatures mats of ca 15 17 c and mean annual precipitation maps of 800 1300 mm for the upper oligocene the narrowest coexistence intervals of the tarkhanian and karaganian display mats of 14 17 c and maps of 800 1300 mm the most substantial data are for the bessarabian in which the lower part is characterized by mats of 15 6 16 6 c and maps from 800 1200 1300 mm the results for the upper part of the bessarabian are more variable especially with respect to precipitation that is generally lower 700 800 mm the same is true for the chersonian where besides lower precipitation lower annual temperature and temperature of coldest month are observed these results correlate with previous vegetation and palaeoclimate data from the forecarpathian basin nw bulgaria

investigating tidal flexure on an ice shelf using kinematic gps the positions of ice stream grounding zones are uniquely sensitive to changes in the mass balance of the ice sheet present methods for locating groundingzone features are either imprecise or require considerable effort in interpretation and so are of little value for change studies we present a new method which uses the kinematic gps technique to locate the position of the limit of tidal flexure the method involves the collection of at least two surface elevation profiles along the same track through the grounding zone at different times during the tidal cycle the elevation profiles obtained coincide upstream of the limit of flexure but diverge downstream of the limit of flexure subtracting the profiles produces a tidal def1ection profile which shows directly the response of the ice shelf to the tidal forcing we present two examples of the use of this method both on rutford ice stream antarctica the first is across the grounding zone and shows that the method is capable of measuring grounding positions to around 200 m precision the second taken across an active shear margin shows a tidal deflection profile with an absence of steps that would indicate the presence of fracture planes penetrating from the ice base to sea level

birth life and death of the pannonian lake abstract the miocene pliocene pannonian lake formed in an extensional basin system behind the compressional arc of the carpathians its size and depth were comparable to those of the caspian sea subsidence began in middle miocene times forming deep pelagic basins separated by reef bearing ridges clastic influx filled the marginal basins during middle miocene time prograding deltas dissected the lake and completed the infilling of the basin system by the end of the pliocene basin plain prodelta delta front delta plain beach fluviatile and marsh environments can be recognized terminal miocene uplift of the carpathians isolated the pannonian region from the rest of paratethys the subsequent decrease of salinity resulted in the evolution of an endemic freshwater mollusc fauna rich nutrient influx from rivers supported high organic productivity dinoflagellates diatoms nannoplankton foraminifers ostracods etc yielding organic rich sediments preservation of organic matter was helped by a stratified water column and oxygen deficient bottom conditions deep burial continuing subsidence and high geothermal flux due to an extremely thin crust led to the formation of commercially exploitable oil and gas accumulations shallow lacustrine zones of basin margins provided suitable environments for a rich congeria melanopsis mollusc fauna wave action on beaches produced commercially exploitable pure quartz sand deposits taxodium and alnus forests flourished around the lake producing enormous lignite deposits besides a rich land snail and mammal fauna prehominids lived in the forests there was a warm temperate climate with probably frostfree winters basaltic volcanoes overlooked the landscape and maars hosted minor lakes with rich algal flora forming oil shale the catchment area included most of the carpathians and parts of the apls and dinarides the positive water balance resulted in a supposed overflow in the southern margin supplying exotic fauna to the south carpathian and dacian basins of the eastern paratethys the pannonian lake was completely filled by the end of pliocene recent lakes in the carpathian basin are not descendants of it

hinge line migration of petermann gletscher north greenland detected using satellite radar interferometry the synthetic aperture radar interferometry technique is used to detect the migration of the limit of tidal flexing or hinge line of the floating ice tongue of petermann gletscher a major outlet glacier of north greenland the hinge line is detected automatically from differential interferograms using a model fitting technique based on an elastic beam theory the statistical noise of the model fit is less than 3 mm and the hinge line is mapped with a precision of 30 m following automatic registration of multidate image data to a precision of 5 m hinge line migration is subsequently detected with a precision of 40 m in the horizontal plane across the glacier width the results show that the hinge line of petermann gletscher migrates back and forth with tide by 70 m in excellent agreement with the migration calculated from ocean tides predicted by a tidal model combined with the glacier surface and basal slope measured by an ice sounding radar superimposed on the short term hinge line migration due to tide we detect a hinge line retreat of 270 m in 3 87 years which varies across the glacier width by 120 m the retreat suggests glacier thinning at a rate of 78 35 cm ice a 1 coincidentally an analysis of ice volume fluxes indicates that the hinge line ice flux of petermann gletscher exceeds its balance flux by 0 88 1 km3 ice a 1 which in turn implies glacier thinning at 83 95 cm ice a 1 in the glacier lower reaches both methods therefore suggest that petermann gletscher is currently losing mass to the ocean

on the derivation of coseismic displacement fields using differential radar interferometry the landers earthquake we present a map of the coseismic displacement field resulting from the landers california june 28 1992 earthquake derived using data acquired from an orbiting high resolution radar system we achieve results more accurate than previous space studies and similar in accuracy to those obtained by conventional field survey techniques data from the ers 1 synthetic aperture radar instrument acquired in april july and august 1992 are used to generate a high resolution wide area map of the displacements the data represent the motion in the direction of the radar line of sight to centimeter level precision of each 30 m resolution element in a 113 km by 90 km image our coseismic displacement contour map gives a lobed pattern consistent with theoretical models of the displacement field from the earthquake fine structure observed as displacement tiling in regions several kilometers from the fault appears to be the result of local surface fracturing comparison of these data with global positioning system and electronic distance measurement survey data yield a correlation of 0 96 thus the radar measurements are a means to extend the point measurements acquired by traditional techniques to an area map format the technique we use is 1 more automatic 2 more precise and 3 better validated than previous similar applications of differential radar interferometry since we require only remotely sensed satellite data with no additional requirements for ancillary information the technique is well suited for global seismic monitoring and analysis

ice ocean interaction on ronne ice shelf antarctica detailed glaciological studies have been completed at 28 sites lying on an approximate flow line extending 760 km across ronne ice shelf parameters measured at each location include ice velocity thickness principal strain rates surface elevation temperature and accumulation rate the data have been used in a steady state model to derive the basal mass flux and the temperature profile with depth at each site from the principles of mass and energy conservation these calculations indicate basal melting in excess of 1 m yr 1 over the first 100 km of the flow line downstream of the grounding line where the ice shelf is between 1200 m and 1600 m thick the maximum melt rates in this region occur near the inland margin and exceed 4 m yr 1 melting continues at a lesser rate over the next 200 km before freezing commences freezing then dominates up to the final 100 km before the ice front resulting in the accumulation of a layer of basal sea ice up to 50 m thick this is rapidly removed as melt rates increase to over 6 m yr 1 at the ice front the cumulative effect of this pattern of basal accumulation and ablation is the wastage by melting of 85 of the mass discharged across the grounding line before it reaches the ice front supporting evidence for a layer of saline ice underlying the ice shelf is provided by the strength of basal radar reflections observed during radio echo sounding of ice thickness in the region where mass balance calculations suggest an accretion of basal sea ice reflection coefficients are consistently low ranging from 6 db to 38 db most of these weak reflections are believed to originate from the true base of the ice shelf the additional energy loss being the result of increased attenuation of the radar signal within the saline layer the derived pattern of basal melting and freezing is consistent with a simple model of sub ice shelf oceanic circulation involving a deep thermohaline convection cell dense saline water which is formed over the continental shelf during winter when the sea surface freezes drains into the deepest parts of the sub ice shelf cavity at the inland margin where this water mass comes into contact with the ice shelf its temperature is 1 c above the local pressure freezing point melting of ice results producing a buoyant outflow of cold relatively fresh water along the ice shelf base basal freezing occurs towards the ice front where the ascending water becomes supercooled this circulation has important implications for the production of antarctic bottom water and for the response of the ice shelf to driving stresses through the temperature dependent viscosity of ice

is the impact of the messinian salinity crisis in the black sea comparable to that of the mediterranean abstract erosional features have been observed along the black sea shelf in wells and on seismic reflection profiles that are broadly similar to the seismic stratigraphic signature of the messinian salinity crisis msc in the mediterranean in particular the intra or middle pontian unconformity has been suggested by some as the manifestation of the msc in the black sea basin missing strata and prominent lithological changes associated with the inferred msc unconformity indicate erosional removal of parts of the underlying cenozoic deposits in the shelf areas of the entire black sea the magnitude of the relative sea level drop associated with this unconformity has been much debated and ranges from tens of meters to thousands of meters the suggestion of a very large 1600 m sea level drop in the black sea during the msc is primarily based on the findings of shallow water clastics and carbonates in deep sea drilling project dsdp wells 380 and 381 however recently acquired long offset seismic data clearly show that both of these wells penetrated gravity driven mega slumps and mass transport complexes therefore the interpreted shallow water msc units in these deepwater wells do not represent in situ rock formations but rather allochthonous strata derived from the basin margin moreover compared to the typical seismic expression of the msc in the mediterranean detailed interpretation of 2d 3d seismic data sets in the bulgarian and turkish black sea revealed considerably more complexity this marked difference is tentatively attributed to the extent of erosion associated with the msc in the black sea i e the multiple msc incisions occurred in a submarine setting not on a subaerially exposed palaeoslope therefore the magnitude of the sea level drop and the overall impact of the msc in the black sea appear to be significantly less than in the mediterranean

miocene connectivity between the central and eastern paratethys constraints from the western dacian basin abstract the dacian basin formed an important link between the central and eastern parts of the paratethys a chain of late tertiary inland seas and lakes this study presents constraints on miocene sea and lake level fluctuations in the dacian basin and on the connectivity between it and other paratethys basins based on the interpretation of seismic lines a micropalaeontological study and lithofacies analysis of a large number of outcrops it is shown that relative sea level fluctuations in the western part of the dacian basin during the middle miocene were primarily driven by tectonic activity in the nearby carpathian mountains from the maeotian late miocene onwards however tectonic activity was minor and relative sea level fluctuations were primarily driven by changes in basin connectivity and climate the connection between the central and eastern paratethys was broken at the end of the middle miocene leading to the development of an endemic fauna in the former but new data presented here suggest that isolation was not sustained completely as central paratethys species appeared in the dacian basin during the maeotian late miocene besides the isolation two falls in water level occurred in the basin during the latest miocene of these the intra pontian sea level drop is the best known we show however that this drop was preceded by a larger sea or lake level drop in the late sarmatian maeotian this latter event may have affected much larger parts of the paratethys and we recommend more study of the bordering basins the hypothesis that the connection between the dacian and central paratethys basins was located in the region where the danube river presently crosses the carpathians was tested but no supporting evidence was found

miocene vegetation and climate dynamics in eastern and central paratethys southeastern europe abstract from the cretaceous to modern time the earth s climate system has changed repeatedly from a greenhouse to an icehouse the miocene appeared as the last warm episode in earth history prior to the establishment of large northern hemisphere ice sheets furthermore the miocene was characterized by both large scale marine transgressions and pronounced episodes of regressions e g opening and closure of marine corridors as well as appearance and disappearance of lakes and swamps the sea level changes and instability of the climate system strongly influenced not only marine ecosystems but also the terrestrial biota to throw new light on the miocene evolution of european ecosystems and climate dynamics we compared plant assemblages from southeastern europe palaeogeographically this area is a transitional belt between tethyan and paratethyan realms and it thus constitutes a crucial geographical position when one tries to comprehend the exchange pathways of various floristic elements appearance and evolution of steppe vegetation interaction between forest and steppe vegetation and of course the corresponding climates influencing the vegetation dynamics both macro and microfloristic plant associations were considered in our analysis large palaeofloristic and palaeocoenotic transformations occurred during the miocene the early to middle miocene flora is rich and diverse in thermophilous elements which formed polydominant mesophytic to hygromesophytic forests early miocene climate was warm and humid with mean annual temperatures mainly above 16 c and annual rainfalls over 1000 mm the middle miocene was the warmest period of the whole miocene with annual temperatures ranging from 17 c to 19 c and winter temperatures from 7 c to 12 5 c climatic changes after the miocene climatic optimum caused changes in floristic composition and vegetation structure the vegetation shows a decreasing trend in abundance of palaeotropic and thermophilous elements reduction of macrothermic elements and disappearance of evergreen laurel forests together with these changes is a corresponding increase in the role of arctotertiary species in plant communities and they became dominants in mesophytic forests the available data indicate that major vegetation changes occur in the late miocene this period is characterized by more diverse climatic conditions which were directed by global climatic changes and probably complicated by regional palaeogeographic reorganizations and tectonic processes slight cooling and some drying is recorded for the beginning of the late miocene followed by fluctuations of palaeoclimate parameters observed which display cycling change of humid dryer and warmer cooler conditions our study provides a new insights on the miocene vegetation and climate dynamics and evolution in southeastern europe

interactions between ice and ocean observed with phase sensitive radar near an antarctic ice shelf grounding line precise measurements of basal melting have been made at a series of 14 sites lying within a few kilometres of the grounding line of the ronne ice shelf antarctica where the ice thickness ranges from 1570 to 1940 m the study was conducted over the course of 1 year and included a detailed survey of the horizontal deformation as well as phase sensitive radar measurements of the vertical displacement of both internal reflecting horizons and the ice shelf base results from the surface survey show that the long term viscous strain rate is modulated at tidal frequencies by probably elastic strains of order 10 5 per metre of tidal elevation the radar measurements show a similar modulation of the long term thinning thickening of the ice shelf with thickness oscillations up to a few centimetres in range the long term trends in ice thickness determined at points moving with the ice shelf flow are consistent with a steady state thickness profile vertical strain rates within the ice shelf were determined from the relative motion of internal reflectors at two sites the observations were sufficient to discern the effect of tidal bending about a neutral surface 60 of the way down the ice column coincident measurements of horizontal and vertical strain imply a poisson s ratio of 0 5 and this combined with the asymmetric bending gives rise to the observed oscillations in thickness at a number of sites the long term viscous strain rates were found to be a linear function of depth for an ice shelf this is an unexpected result it can be attributed to the presence of significant vertical shear stresses set up close to the grounding line where the ice is still adjusting to flotation additional vertical motion arising from firn compaction was observed within the upper layers of the ice shelf the additional motion was consistent with the assumption that firn density is a function only of the time since burial by steady surface accumulation with both spatial and temporal fluctuations in the vertical strain rate accurately quantified it was possible to estimate the vertical motion of the ice shelf base in response differences between the calculated and observed motion of the basal reflector arise because of basal melting derived melt rates at the 14 sites ranged from 0 11 0 31 to 2 51 0 10 ma 1 with a mean of 0 85 m a 1 and a standard deviation of 0 69 m a 1 and showed no signs of significant sub annual temporal variability there was no obvious global correlation with either ice thickness or distance from the grounding line although melt rates tended to decrease downstream along each of the flowlines studied previous estimates of basal melting in this region have been obtained indirectly from an assumption that the ice shelf is locally in equilibrium and have included a broad range of values only those at the lower end of the published range are consistent with the directly measured melt rates reported here

lithospheric memory state of stress and rheology neotectonic controls on europe s intraplate continental topography abstract to date research on neotectonics and related continental topography development has mostly focused on active plate boundaries characterized by generally high deformation rates the intraplate sedimentary basins and rifts of the northern alpine foreland are associated with a much higher level of neotectonic activity than hitherto assumed seismicity and stress indicator data combined with geodetic and geomorphologic observations demonstrate that europe s intraplate lithosphere is being actively deformed this has major implications for the assessment of its natural hazards and environmental degradation the lithosphere of the northern alpine foreland has undergone a polyphase evolution with an intense interplay between upper mantle thermal perturbations and stress induced intraplate deformation that points to the importance of lithospheric folding of the thermally weakened lithosphere in this paper we address relationships between deeper lithospheric processes neotectonics and surface processes in the northern alpine foreland with special emphasis on tectonically induced topography the objectives are to quantify the effects of ongoing alpine collision and atlantic ridge push on the intraplate deformation in europe and its impact on topography evolution and related natural hazards this paper reviews the four dimensional topographic evolution of the european lithosphere through a multi disciplinary approach linking geology geophysics and geotechnology until now research on neotectonics and related topography development of intraplate regions has received little attention our study examines a number of selected natural laboratories in continental europe from orogen through platform to continental margin these natural laboratories include the carpathians pannonian system the northwest european platform iberia and the atlantic continental margin we focus on lithosphere memory and neotectonics with special attention to the thermo mechanical structure of the lithosphere mechanisms of large scale intraplate deformation late neogene anomalies in subsidence and uplift and links with surface processes and topography evolution

glaciological investigations on union glacier ellsworth mountains west antarctica union glacier west antarctica was intensively mapped in december 2008 when an over snow traverse was conducted by cecs and ale with the aim to determine the ice dynamical characteristics of the glacier through mapping the crevasse fields and by providing a glaciological baseline for future studies a mean ice thickness of 1450 m was measured confirming the presence of a deep subglacial topography 900 m below sea level much deeper than previously estimated ice velocities were also measured at 21 stakes drilled into the ice at the narrowest gate of the glacier between december 2007 and december 2008 yielding a mean value of 22 6 m a 1 these velocities combined with the measured ice thicknesses and a numerical model yielded an ice flux of 0 10 0 03 km 3 a 1 w e considering the ice basin above this gate a mean surface mass balance of 0 18 0 05 m a 1 was estimated a value consistent with a mean snow accumulation for nearby ice streams these values indicate that the glacier is at present near equilibrium

novel polar biomarkers of the miocene maritza east lignite bulgaria abstract the present study provides further insight into the composition of polar compounds in the miocene maritza east lignite bulgaria samples from two coal seams and interbedded claystone layers have been analyzed by geochemical proxies for polar constituents consisting of n alkan 2 ones n alkanols n alkanoic acids polar sesqui di and triterpenoids steroids hopanoid acids etc these series are quantified correlated vs depth and various ratios calculated polar diterpenoids predominate in the soluble organic matter several new compounds were identified i e 7 11 dehydro 12 oxoabieta 7 9 11 13 triene salvinolone and chamaecydins the preferential contribution of cupressaceae taxodiaceae in the palaeoflora is confirmed by the significant abundance of polar diterpenoids 200 600 g g c org and is further supported by the presence of chamaecydins 3 9 g g c org the polar lupane assemblage attests that betulaceae also was an important input from angiosperm vegetation to the palaeomire the related new compounds are 24 25 bisnoroxyallobetula 1 3 5 10 triene and 24 25 bisnorallobetula 1 3 5 10 triene which further support this point this investigation increases the knowledge on floral progenitors and provides further proof of the input from the cupressaceae taxodiaceae or podocarpaceae families as the most abundant trees in the peat forming environment of the miocene maritza east basin

palaeogeographic environment during the desiccation of the black sea abstract during the latest chersonian about 10 3 m y ago tectonic movements took place leading to an elevation of the crimean caucasian chain and to an isolation of the fore caucasian part of the black sea basin this part of the basin had been draining the rivers of the russian platform and after the isolation it became desalinized while the main part of the black sea basin was almost desiccated and evaporites mainly dolomites formed in it due to the predominant calcium magnesium carbonate composition of the chersonian sea waters these dolomites are found in the drillings of dsdp leg 42b and are confirmed geophysically the tectonic movements during the latest chersonian led to the formation of a series of grabens along which the mediterranean sea invaded the north aegean area and a little later during the early maeotian the black sea

acoustic impedance and basal shear stress beneath four antarctic ice streams the acoustic impedance of the subglacial material beneath 7 2 km profiles on four ice streams in antarctica has been measured using a seismic technique the ice streams span a wide range of dynamic conditions with flow rates of 35 464 in a 1 the acoustic impedance indicates that poorly lithified or dilated sedimentary material is ubiquitous beneath these ice streams mean acoustic impedance across each profile correlates well with basal shear stress and the slipperiness of the bed indicating that acoustic impedance is a good diagnostic not only for the porosity of the subglacial material but also for its dynamic state deforming or non deforming beneath two of the ice streams lodged non deforming and dilated deforming sediment coexist but their distribution is not obviously controlled by basal topography or ice thickness their distribution may be controlled by complex material properties or the deformation history beneath rutford ice stream lodged and dilated sediment coexist and are distributed in broad bands several kilometres wide while on talutis inlet there is considerable variability over much shorter distances this may reflect differences in the mechanism of drainage beneath the ice streams the material beneath the slow moving carlson inlet is probably lodged but unlithified sediment this is consistent with the hypothesis that carlson inlet was once a fast flowing ice stream but is now in a stagnant phase which could possibly be revived by raised basal water content the entire bed beneath fast flowing evans ice stream is dilated sediment

ice flow modulated by tides at up to annual periods at rutford ice stream west antarctica 1 for over 2 years we have collected gps data 40 km upstream of the grounding line on rutford ice stream west antarctica here we examine deviations from mean downstream flow although the record is incomplete during winter there is clear modulation of flow at semi diurnal diurnal two weekly semi annual and annual ocean tidal frequencies this is the first observation of ice stream flow variations over such a long time period and such a wide range of frequencies the ice stream flows fastest at equinoxes when there are two semi diurnal tides of equal magnitude and slowest at solstices when one of the semi diurnal tides has lower amplitude the sensitivity of the downstream flow is greatest to the long period forcing which suggests that ice stream velocity may be affected by future changes in sea level if so this effect would provide a feedback whereby rising sea levels could increase ice stream velocity and hence discharge

catastrophic flooding of the black sea abstract decades of seabed mapping reflection profiling and seabed sampling reveal that throughout the past two million years the black sea was predominantly a freshwater lake interrupted only briefly by saltwater invasions coincident with global sea level highstand when the exterior ocean lay below the relatively shallow sill of the bosporus outlet the black sea operated in two modes as in the neighboring caspian sea a cold climate mode corresponded with an expanded lake and a warm climate mode with a shrunken lake thus during much of the cold glacial quaternary the expanded black sea s lake spilled into to the marmara sea and from there to the mediterranean however in the warm climate mode after receiving a vast volume of ice sheet meltwater the shoreline of the shrinking lake contracted to the outer shelf and on a few occasions even beyond the shelf edge if the confluence of a falling interior lake and a rising global ocean persisted to the moment when the rising ocean penetrated across

observation of ocean tides below the filchner and ronne ice shelves antarctica using synthetic aperture radar interferometry comparison with tide model predictions tides near and under floating glacial ice such as ice shelves and glacier termini in fjords can influence heat transport into the subice cavity mixing of the under ice water column and the calving and subsequent drift of icebergs free surface displacement patterns associated with ocean variability below glacial ice can be observed by differencing two synthetic aperture radar sar interferograms each of which represents the combination of the displacement patterns associated with the time varying vertical motion and the time independent lateral ice flow we present the pattern of net free surface displacement for the iceberg calving regions of the ronne and filchner ice shelves in the southern weddell sea by comparing sar based displacement fields with ocean tidal models the free surface displacement variability for these regions is found to be dominated by ocean tides the inverse barometer effect i e the ocean s isostatic response to changing atmospheric pressure also contributes to the observed vertical displacement the principal value of using sar interferometry in this manner lies in the very high lateral resolution tens of meters obtained over the large region covered by each sar image small features that are not well resolved by the typical grid spacing of ocean tidal models may contribute to such processes as iceberg calving and cross frontal ventilation of the ocean cavity under the ice shelf

influence of floral assemblage facies and diagenesis on petrography and organic geochemistry of the eocene bourgas coal and the miocene maritza east lignite bulgaria abstract numerous differences in the petrography and organic geochemistry of two tertiary low rank coal deposits of bulgaria formed within comparable depositional environments are outlined different floral assemblages are indicated as the main sources of organic matter for the eocene bourgas sub bituminous coals a warm climate plant community dominated by angiosperms is reflected in the biomarker composition whereas a coniferous flora was the main source of the resinous organic matter of the miocene maritza east lignite the results are in agreement with palaeobotanical data these differences in the peat forming vegetation of the paleogene compared to the neogene of bulgaria are attributed to decreasing temperature during the tertiary the abundance of resinous compounds relative to lipids from plant waxes long chain n alkanes as well as the preservation of plant tissue are mainly controlled by gymnosperm angiosperm ratios pristane phytane and diasterenes sterenes ratios reflect variations in redox conditions and the ph of the depositional environments caused by eustatic sea level changes freshwater inflow or varying ground water table changing eh and ph values are associated with differences in microbial activity controlling the extent of gelification of plant tissue bacteria most probably contributed to the aromatisation of triterpenoids in the mire enhanced thermal maturation of organic matter during diagenesis is reflected in higher contents of n alkanes and the presence of alkyl naphthalenes in the bourgas coals alkyl naphthalenes are thought to have been formed from pentacyclic triterpenoids rather than from resinous compounds