on late miocene to recent vertical motions in the cretan segment of the hellenic arc abstract high resolution foraminiferal and calcareous nannoplankton biostratigraphy and reliable paleobathymetry estimates based on plankton benthos ratios in foraminifera make it possible to reconstruct in detail late neogene vertical motions along the central cretan segment of the hellenic arc these motions are considered to express the surficial effect of the roll back process of the hellenic subduction zone which started about 12 ma ago in contrast to earlier views there is no sustained uplift since the late middle miocene successive paleotopographic profiles for central crete show a predominance of subsidence coupled with an increase of differential reliefs from the latest serravallian until the messinian subsidence was most pronounced between the tortonian messinian boundary interval and the early part of the early pliocene locally up to a magnitude of more than 1000 m a two phased uplift history coupled with tilting to the north or northeast can be inferred from the late early pliocene recent record separated by a short early late pliocene episode of subsidence rates of uplift were highest in the early pliocene up to about 125 cm ka the central cretan late neogene to recent paleotopographic profiles are compared with those reconstructed from seismic interpretations and drilling data from the cretan sea the combined results show that paleotopographic configurations between the cyclades and crete were fairly similar to those on central crete until messinian time foundering of the cretan basin started in the course of the early pliocene but subsidence rates were less than the contemporaneous uplift rates of crete the timing and magnitude of the vertical motions along the cretan sea central cretan transect put detailed geological constraints on tectonophysical modelling of the surficial effects of the roll back process these vertical motions are discussed in view of the model of southward translation of a large supracrustal slab resulting in the origin of the cretan sea and in thrusting and uplift in the frontal parts of the slab where it thrusted over the northern limb of the subducted ionian plate

on the hellenic subduction zone and the geodynamic evolution of crete since the late middle miocene abstract in recent syntheses of the geodynamic evolution of the aegean area the hellenic subduction zone and in particular its initiation plays a central role two basic aspects of the recent comprehensive model put forward by le pichon angelier and co workers are a initiation of subduction along the hellenic arc is inferred to have taken place approximately 13 ma ago whereas several others have suggested approximately 5 ma and b migration of the trench system to the south southwest giving rise to an extensional regime in the back arc region which led to general subsidence and formation of the present day aegean sea new data on the structure of the upper mantle underneath the aegean area indicate that the former aspect requires modification the seismic velocity structure indicating a northward dipping slab down to a depth of at least 600 km and the depth distribution of earthquake hypocenters can not be reconciled with straightforward initiation of subduction approximately 13 ma ago estimates of about 5 ma for the time of initiation of the present subduction zone are even more difficult to reconcile assuming 400 km as an upper bound for the effect of stretching of the aegean sea and of other processes contributing to the separation of crete from the eurasian mainland we arrive at an age for the hellenic subduction zone of at least 26 ma as to aspect b geological data of crete lend strong support to the idea that on crete compressional tectonics is of much greater importance than current models imply combining geophysical and geological data we propose a modification of the tectonic evolution for the cretan segment of the hellenic arc whereas the basic process of extension caused by a migrating trench system roll back in a land locked basin remains a very useful and sound concept the tectonics of the margins of a region subject to stretching in this case crete may be more complicated than hitherto thought in our model the documented fragmentation of crete into several basins which started about 12 ma ago is not attributed to initiation of subduction but to inception of the roll back process compressional tectonics on crete is taken to be associated with deformation of the crust resulting from the overall tensional stress regime

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

tectonostratigraphy of the north alpine foreland basin correlation of tertiary depositional cycles and orogenic phases abstract tectonostratigraphic analysis of the depositional history of the north alpine foreland basin indicates that temporal relationships exist between short term events in the foredeep and the adjacent alpine orogen the foredeep can be divided stratigraphically into an alpine foredeep thanetian bartonian pre molasse basin latest bartonian earliest rupelian and molasse basin rupelian tortonian their general and tectonostratigraphic development includes time significant cycle sets and so called cenozoic rift and foredeep crf sequences which are apparently correlative to both foreland and orogen deformation events as well as to changes in global sea level individual basin fill sequences and consequently general stratigraphic and palaeogeographical aspects of the evolving basin system are thus found to be frequently defined by contemporaneous widely distributed tectonics and eustasy successive dominant depositional states underfilled steady state and overfilled episodes and facies flysch molasse are correlated with different concurrently progressing phases of the convergence and subduction history of the european and apulian plates

sedimentary response to intra arc extension controls on oligo miocene deposition sarcidano sub basin sardinia the oligo miocene sardinian rift is a rare example of a well exposed intra arc basin comprising several independent depocentres synthesis of field observations from one such depocentre the sarcidano sub basin in central sardinia not only allows a new and integrated sedimentological and tectonostratigraphic history for the area but also provides insights into controls on syn and post rift sedimentation in intra arc settings initial rifting during the late rupelian early chattian oligocene occurred on nw se trending normal faults and produced a half graben topography which controlled the dispersal of locally supplied coarse continental clastic sediments latest chattian aquitanian miocene ne sw trending normal faulting defined a more complex block topography that remained underfilled in all areas except those which received voluminous ignimbritic volcanic material subsequent marginal and shallow marine sedimentation progressively infilled the fault topography as sea level rose deposition of coarse clastic sediments eroded from fault scarps was focused in the hanging wall depocentres of the intersecting fault trends whilst platform carbonates became established in topographically higher areas protected from clastic sedimentary supply finally as the relative rise in sea level drowned sediment source areas in the burdigalian deeper marine marlstones dominated sedimentation the results demonstrate that the sarcidano sub basin was dominated by a mixed volcanic siliciclastic carbonate basin fill with abrupt facies changes developed in response to complex fault defined topography relative rise in sea level and an episodic volcanic supply whilst the rift structure largely controlled the provenance supply and accumulation of sediments relative sea level primarily controlled the types of facies that developed

comparative tertiary stratigraphy of the rhine graben bresse graben and molasse basin correlation of alpine foreland events abstract comparative tectonostratigraphic analysis of the tertiary middle eocene pliocene of the rhine bresse graben system and the western molasse basin demonstrates the occurrence of eleven correlative sequences crf i xi these show a close relationship between intra basinal tectonics and depositional history their punctuated sediment accumulation can be related to phases of extra alpine taphrogenesis and alpine orogenesis and to coeval eustatic changes in sea level apparent simultaneity in rift and foredeep sequence development structural deformation and global change in sea level suggests a common causal control in which the development of the alps played an important role

the two stage opening of the western central mediterranean basins a forward modeling test to a new evolutionary model abstract the algero provencal and the tyrrhenian extensional basins developed in two stages in a geodynamic setting characterized by the nearly n s convergence between africa and eurasia the spreading of the provencal basin occurred in the early miocene following a long period of rifting in the western mediterranean area a dramatic eastward shift of the active extensional deformation resulted in the tortonian to quaternary opening of the tyrrhenian basin in a companion paper carminati et al propose that a trench retreat process in a geodynamic setting locked by the continental collisions in the alps and in the betic chain is a viable mechanism for the late oligocene early langhian opening of the western mediterranean a langhian slab detachment episode along the north african margin is likely to have caused the end of the trench retreat along this part of the boundary determining the end of active expansion in the western mediterranean and the beginning of active extension in the tyrrhenian basin the objective of the present paper is to quantitatively test this proposed scenario we calculate by means of a thin shell model the effects of these plate boundary reorganizations on the european stress and strain field we show that the two stage opening of the western and central mediterranean can be explained by the evolution proposed by carminati et al and that in particular the eastward shift of the active extension which produced the termination of the first opening stage and the beginning of the second is likely to have been triggered by the slab detachment episode along the north african margin

initiation and evolution of the valencia trough western mediterranean constraints from deep seismic profiling and subsidence analysis abstract the structure and evolution of the valencia trough western mediterranean a neogene basin bordered in the north by prominent oligocene early miocene grabens in the catalan coastal ranges and to the south by the early miocene thrust sheets of the betic belt is investigated through a deep seismic reflection profile shot across the basin this profile shows that extensional features related to the rifting are concentrated in the catalan valencian domain in the north whereas in the south the betic balearic domain shows little extensional structures and no clear thrusting the smooth quite symmetrical moho uplift seems to cross cut strong se dipping reflectors which are clearly visible below the moho in the central basin deep seismic data tied on wells and industrial lines are used to establish a regional depth section which is backstripped and along which the history of tectonic subsidence is investigated assuming local isostasy we find out that observed tectonic subsidence shows a classical exponential decay for the period 0 15 2 ma consistently with observed moho attenuation even to the south where a foreland type mechanism of subsidence is not recognized little subsidence is found for the period 25 2 20 ma we also indicate that some brittle basement readjustement must have occurred around 15 2 ma and that the heat flow although variable is not inconsistent with theoretical model of uniform lithosphere attenuation we therefore propose that the development of the valencia trough occurred in two rifting stages the first the oligo miocene west european rifting event had minor effects in the deep basin and affected mostly the catalan margin the second serravallian in age 15 2 10 2 ma is responsible for present day moho uplift and explains the post mid miocene basin development this second rifting is coeval with the opening of the tyrrhenian basin its significance at the west of the western mediterranean remains to be investigated

lateral shifts of apenninic foredeep depocentres reflecting detachment of subducted lithosphere abstract the hypothesis of lateral migration of slab detachment was formulated on the basis of seismic tomography results on the 3 d structure of subduction zones in the mediterranean region m j r wortel and w spakman structure and dynamics of subducted lithosphere in the mediterranenan region proc k ned akad wet 95 1992 325 347 the redistribution of slab pull forces associated with the tearing process is taken to affect foredeep development by adding a lateral component to internal external depocentre migrations in the case of the apenninic arc the direction of detachment and associated depocentre migration is expected to be southeast this prediction has been confronted with the tectonostratigraphy of oligocene to recent apenninic foredeeps results show there are two episodes marked by important lateral shifts of foredeep depocentres during the early late miocene tortonian the depocentre of the northern apennines foredeep shifted towards the southeast this is evidenced by the relative positions of the depocenters of the burdigalian serravallian marnoso arenacea and the tortonian umbrian marchean and lazian minor basins a further stepwise southeastward migration can be inferred from the plio pleistocene records of the central and southern apennines in a more general sense our results indicate that slab detachment may play a significant role in the evolution of foredeeps along convergent plate boundaries

late cenozoic deformation of the hellenide foreland western greece the late cenozoic structural evolution of western greece involved the shortening of mesozoic passive continental margin and cenozoic foreland basin sequences in a foreland propagating fold and thrust system and superimposed neotectonic deformation related to the development of an active island arc although the pre apulian zone has been regarded as the undeformed western foreland to the thrust belt three dimensional exposures in the ionian islands of kephalonia and zakinthos afford evidence of significant late neogene and quaternary shortening including thrusting on reactivated normal faults time relations and fault kinematics show that these structures are compatible with the westward migration of the locus of hellenide thrusting beyond its previously recognized limit and outer arc compression related to active subduction the presence of the pre apulian zone in the west contrasts with other aegean foreland areas where no such intermediate block lay between the thrust pile and old mesozoic oceanic crust consequently the pre apulian block took up continued hellenide shortening in the late miocene while oceanic crust was being overridden subducted in southern parts of the arc to the east the pre apulian zone subsequently overrode the ocean floored ionian sea during the late neogene the confusion in determining driving mechanisms for late cenozoic deformation in western greece and the apparent conflict between evidence for the age of initial subduction in different parts of the arc are explained by this model which is consistent with regional considerations including structuration in adjacent areas and important paleomagnetic rotations in the arc

in situ filtration and preliminary molecular analysis of microbial biomass from the rainbow hydrothermal plume at 36 15 n on the mid atlantic ridge abstract elevated microbial biomass levels play a significant role in altering the chemical composition of hydrothermal plumes in this work a procedure was developed for collecting sufficient quantities of microbial biomass from a hydrothermal plume to allow the extraction of dna suitable for use in molecular analyses of the plume microbial populations during a geophysical survey along 200 km of the mid atlantic ridge mar southwest of the azores triple junction several new sites of hydrothermal activity were identified including the rainbow hydrothermal plume at 36 15 n the strongest such feature yet reported from the mar during the survey in situ filtration systems were used to collect microbial biomass from the water column onto 293 mm diameter 0 2 m pore membrane filters by pumping large volumes 300 500 l of seawater through the filters filter samples were collected from both the neutrally buoyant portion of the rainbow plume at a depth of 2050 m and from above it in the water column at 1500 m microgram quantities of genomic dna were extracted and purified from the biomass on these filters the suitability of the purified dna for use in molecular analyses was demonstrated by polymerase chain reaction pcr amplification of the small subunit ribosomal rrna ssu rrna gene from the two primary prokaryotic domains the bacteria and the archaea as indicated by the binding of domain specific oligonucleotide hybridisation probes to the purified dna the plume microbial populations contained a higher proportion of members of the domain archaea than the populations in the surrounding ambient sea water

the eocene oligocene climate transition in the central paratethys abstract we studied two boreholes cserepvaralja 1 and kiscell 1 with continuous sedimentary records across the eocene oligocene climate transition from the central paratethyan area assemblages of benthic foraminifera display a shift in dominance by epifaunal taxa in the late eocene to shallow and deep infaunal taxa in the early oligocene using the benthic foraminiferal oxygen index bfoi a decreasing trend of bottom water oxygen levels is established across the eocene oligocene transition eot leading to the development of dysoxic conditions later in the early oligocene trends in 18o and 13c values measured on tests of selected benthic and planktic foraminifera roughly parallel those of the global record of stepped eot 18o increase and deviate only later in the early oligocene related to the isolation of the paratethys the overall similarity of the isotope curves and the presence of a planktic benthic ecological offset suggest that the original isotope trends are preserved despite the systematically more negative 18o values of different scenarios a quasi uniform diagenetic overprint by fluids with low 18o values during burial or uplift appears best supported we conclude that the globally established isotopic expression of antarctic ice sheet growth across the eot may be recognizable in the paratethys deviations from the global trends after the eot were caused by regional paleoceanographic changes induced by the progressing alpine orogeny and sea level change which led to a restricted connection with the open ocean freshwater influx from increased precipitation and gradual development of bottom water oxygen depletion

late miocene uplift in the romagnan apennines and the detachment of subducted lithosphere abstract we report part of a test of the hypothesis that detachment of subducted lithosphere may be a process of lateral propagation of a horizontal tear wortel and spakman proc kon ned akad wetensch 95 1992 325 347 we have used the apennines as a test area the test procedure consists of the comparison of hypothetical vertical motions predicted from the expected redistribution of slab pull forces with observed vertical motions we demonstrate that a late miocene depocentre migration from the northern towards the central apennines is associated with uplift of the fore arc of the northern apennines such a combination of a depocentre shift and uplift is thought to be diagnostic for lateral migration of slab detachment the depocentre migration was identified in earlier work van der meulen et al earth planet sci lett 154 1998 203 219 this contribution focuses on uplift which has primarily been identified through the geohistory analysis of the monte del casino section romagnan apennines northern italy owing to methodological problems the start and duration of the uplift phase could not be constrained and only a minimum estimate of the total amount of uplift 483 180 m is obtained the data do allow for an estimate of the uplift rate 163 61 cm ky a review of regional data results in better constraints on the timing of the above lateral reorganisation of the fore arc and on the spatial extent of the uplifted area depocentre development in the central apennines began between 8 6 and 8 3 ma b p uplift started between 9 and 8 ma b p and affected the entire northernmost apennines

sensitivity of mediterranean thermohaline circulation to gateway depth a model investigation 1 the neogene sedimentary record of the mediterranean sea holds evidence for changes in water properties and circulation these paleoceanographic changes have been attributed to changes in the flow through the ocean gateway between the mediterranean sea and the atlantic ocean we use an oceanic general circulation model to achieve quantitative physics based understanding of the effect of changes in the depth of the gateway such as may result from tectonic activity or variation in sea level to isolate these effects we use idealized basin geometry and impose simplified atmospheric forcing a reference experiment with present day sill depth demonstrates that the model simulates reasonably well the main features of the present day mediterranean thermohaline circulation as inferred from observations and previous numerical studies subsequently a series of sensitivity simulations is performed with different sill depths the model results show that mediterranean temperature salinity and thermohaline circulation depend strongly on sill depth as the sill depth decreases the upper overturning cell is quasi linearly reduced in strength while contrary to what one would expect the deep cell intensifies and does so in a nonlinear way we find that a shoaling of the sill depth induces a blocking effect on the outflow waters which creates a strong recirculation in the deep layers strengthening the deep cell nevertheless deep water formation is reduced and as a consequence the ventilation of the deep layers diminishes we identify three different circulation modes of the mediterranean thermohaline circulation depending on the sill depth shallow sill moderate sill and deep sill modes coupled with strong weak and negligible blocking effects respectively our results are consistent with the pre messinian paleoceanographic record of the mediterranean sea and may be useful to understanding the behavior of other land locked basins both extant and from the geological past

towards a mechanical model for the formation of the pannonian basin abstract new maps showing crustal and lithospheric thickness variations in the pannonian basin and the surrounding east alpine carpathian and dinaric mountains have been prepared on the basis of recent seismic seismologic and electromagnetic data a map presenting miocene faults of regional significance has been also constructed for the same region by using a wealth of recently available national and or more local studies it is suggested that observed crustal and lithospheric structural contrasts have been controlled primarily by neogene kinematic history of the region kinematic history is characterized by the following main patterns 1 1 indentation by adria and large scale backthrusting in the southern alps 2 2 eastward escape and extension of the eastern alps 3 3 extensional collapse in the pannonian basin area 4 4 formation of broad wrench fault systems along strike in the dinarides and southern carpathians and the western carpathians with dextral and sinistral shear respectively 5 5 compression and accretion of the external thrust and fold belt in the eastern carpathians these kinematic patterns are thought to be interrelated and all are manifestations of the late stage evolution of an overthickened orogenic wedge in order to arrive at a better understanding of the mechanism of extension which formed the pannonian basin deep crustal seismic profiles hydrocarbon exploration reflection lines and borehole data have been analyzed in the little hungarian plain this plain represents the transition zone between the alps and the pannonian lowlands and the results are illustrated by eight interpreted cross sections one result of regional importance is the clear recognition that the transdanubian central range at the southeastern flank of the little hungarian plain is composed of alpine pre senonian thrust sheets this finding marks the end of a century of debate the allochthony of the substrata of the pannonian basin can be now considered proven another result of more general interest is that these cross sections document the mode of lithospheric extension preexisting compressional detachment planes reactivate as low angle normal faults and lead to tectonic unroofing of deeply buried metamorphic terranes characterized by ductile flow along subhorizontal lineation

on late oligocene to pliocene depocentre migrations and the evolution of the carpathian pannonian system abstract the late oligocene to pliocene evolution of foredeep basins of the eastern alps carpathians fold and thrust belt is marked by pronounced internal to external and lateral depocentre shifts the latter shifts covering a present along arc distance of 1700 km portray accelerating rates of foredeep depocentre migration particularly so in the late early and in the middle miocene from about 7 to about 45 cm yr lateral depocentre migration came to a close at the beginning of the late miocene the subsequent late miocene to pliocene foredeep infill history was characterized by exponentially increasing accumulation rates in the intersection area of the east european ukrainian and moesian platforms successive steps in the evolution of the foredeep basins had pronounced counterparts in the intra carpathian area the beginning of acceleration of foredeep depocentre migration in latest early miocene times was coeval with the inception of intra carpathian extensional tectonics the extremely rapid middle miocene depocentre shift coupled with a change in direction of foredeep depocentre migration corresponded with maximum extension in the intra carpathian area the ensuing end of foredeep depocentre migration around the middle late miocene transition was coeval with the end of extension of the intra carpathian area which in turn was followed by the inception of overall thermal subsidence at about 11 5 ma the timing of and spatial relationships between discrete coeval events in arc and intra arc evolution put unambiguous geological constraints on geodynamic modelling of the evolution of the carpathian pannonian system it is speculated that the geological observations may best be understood in terms of the surficial effects of lateral migration of slab detachment such effects would mirror the dominant role of a concentrating slab pull taken to result in e g a time progressive acceleration of foredeep depocentre migration

deep sea trace fossils of the oligocene miocene numidian formation northern tunisia abstract twenty two ichnogenera and thirty one ichnospecies have been recorded in the oligocene miocene numidian formation of northern tunisia heterolithic successions of thin bedded turbidite sandstones and interchannel mudstones contain the most diverse trace fossil assemblages thick to very thick bedded structureless sandstones and conglomerates representing the fill of channel complexes contain a low diversity trace fossil assemblage the ichnoassemblage in the lower part of the formation oligocene which includes paleodictyon isp scolicia strozzii spirorhaphe isp cosmorhaphe isp and halopoa isp can be ascribed to the paleodictyon ichnosubfacies of the nereites ichnofacies the ichnoassemblage in the upper part of the formation miocene aquitanian including diplocraterion cf habichi scolicia vertebralis and ophiomorpha isp is interpreted as the shallower part of the ophiomorpha rudis ichnosubfacies of the nereites ichnofacies the notable switch in ichnofauna between the oligocene and lower miocene reflects variation in environmental and depositional conditions the common occurrence of trace fossils of the ophiomorpha rudis ichnosubfacies and diplocraterion cf habichi in the early miocene indicates an increase in energy level greater environmental disturbance and probable shallowing this is also confirmed by a corresponding decrease in the abundance and diversity of benthic foraminifera the integration of ichnological sedimentological and microfossil contents has allowed the distinction of two quite distinct geographical depositional settings within the numidian formation the first domain includes the numidian succession of the tabarka cap negro cap serrat and bouhertma areas which are characterised by distal turbidites showing the paleodictyon ichnosubfacies that is compatible with a lower bathyal depth in the oligocene and an upper slope depositional environment during the early miocene the second domain includes the ne part of mogod mountain e g the ras el korane jebel gattous zoukar which exhibit more proximal characteristics compatible with a probable slope canyon interpretation the southern margin of the kroumirie balta and zouza areas and sejnene area shows a distal setting compared with the ras el korane and jebel gattous zoukar areas it is ascribed to a mid to upper slope depositional environment during the oligocene to early miocene

the role of slab detachment processes in the opening of the western central mediterranean basins some geological and geophysical evidence abstract a review of the geological and geophysical data from the central and western mediterranean region and the present day upper mantle structure derived from tomographic studies are utilized in order to define the oligocene recent geodynamic evolution for the area in line with previous work we suggest that the miocene quaternary opening of the western and central mediterranean basins is the result of back arc extension due to the roll back toward the southeast of a northwestward subducting african slab in a geodynamic setting pinned between the alpine and betic collisional zones we find however that this general pattern is complicated by four different detachment events which occurred beneath the alps early oligocene the betic chain aquitanian northern africa langhian and the apennines late miocene pliocene we show that each of these events determines a major tectonic reorganization within the european plate

a major late tortonian rotation phase in the crotone basin using ams as tectonic tilt correction and timing of the opening of the tyrrhenian basin abstract paleomagnetic studies of sediments from the calabro peloritan block in southern italy consequently imply a 15 clockwise rotation for the late tortonian to middle pleistocene sedimentary cover but the results of older sediments are generally less consistent earlier paleomagnetic results of tortonian sites from the basilicoi section crotone basin northern calabria suggested a major counterclockwise rotation of 97 scheepers 1994 here we studied the basilicoi section in detail and we used anisotropy of the magnetic susceptibility ams to reconstruct the bedding plane needed for tilt correction this reduced the 97 counterclockwise rotation to a 25 counterclockwise rotation the lese section also in northern calabria shows the same counterclockwise rotation in sediments with an age between 10 4 and 8 6 ma thus confirming the results from the corrected basilicoi section a comparison of the magnetostratigraphy and planktonic foraminiferal biostratigraphy with the magneto biostratigraphic framework of the mediterranean late miocene allows a correlation of the basilicoi and lese sections to the gpts and a timeframe for the rotation it is concluded that the 25 counterclockwise rotation phase took place between 7 6 0 1 and 8 6 ma we speculate that the timing of this tectonic phase is related to the opening of the tyrrhenian sea and the separation of calabria from sardinia we compare our results with those of odp leg 107 and we suggest an age between 8 6 and 7 8 ma for the timing of the opening of the tyrrhenian sea

mosaic of environments recorded by bryozoan faunas from the middle miocene of hungary the marine sediments of the badenian middle miocene of hungary pannonian basin central paratethys are composed of abundant bryozoan skeletal grains seventy one bulk samples collected at 18 localities outcrops and boreholes yielded a total number of 238 bryozoan species in order to reconstruct the badenian palaeoenvironments the present study investigates the composition of this very diverse fauna using a combination of statistical and palaeoecological methods the statistical analyses make use of cluster analysis and non metric multi dimensional scaling the palaeoecological approaches are based on the known ecological requirements of the bryozoan colonial growth forms and of the numerous extant species five facies have first been differentiated on the basis of sedimentological and palaeontological features coral buildups coralline algal limestones biocalcarenites sands and marls each of them is characterized by the abundance the diversity and the types of growth forms of the bryozoans the palaeoecological statistical and facies analyses further permitted to identify four depositional settings carbonate platform distal and proximal terrigenous platform slope and basin these environments developed at depths between 0 to about 300 m in a mixed carbonate siliciclastic depositional system skeletal production and spatial distribution of carbonate factories were predominantly controlled by terrigenous input this resulted in a complex mosaic of facies habitats where rich bryozoan faunas could thrive many warm water organisms among them foraminifers zooxanthellate corals molluscs bryozoans and echinoids were recorded from the study sites the coexistence of coralgal and bryomol carbonate skeletal assemblages in this subtropical setting is explained mostly by variations in the productivity of surface waters periods of nutrient enrichment and increased benthic eutrophication affected coral diversity and abundance in favour of bryozoans

tertiary palaeogeography and tectonostratigraphic evolution of the northern and southern peri tethys platforms and the intermediate domains of the african eurasian convergent plate boundary zone abstract the increasing effects of african eurasian convergence during the tertiary resulted in the uplift and emergence of the northern and southern peri tethys platforms palaeogeographic maps covering six selected time slices including the middle eocene late early oligocene late early miocene early middle miocene early late miocene and middle to late pliocene illustrate that environmental and depositional differentiations on the northern platform and along the bordering domains of the convergence zone were more pronounced than on the southern platform and its adjacent areas the tectonic evolution of the northern platform included an overall eastward directed trend in the onset of basin uplift and emergence which started at about the eocene oligocene transition at 34 ma tectonostratigraphic analyses indicate a striking contemporaneity of the events which defined the temporal and spatial development of both the domains of the convergent plate boundary zone and the bordering platforms five episodes of major regional change in palaeogeographic and tectonic setting are distinguished they occurred in the late eocene 37 34 ma early late oligocene 30 27 ma latest early to earliest middle miocene 17 15 ma early late miocene 9 8 ma and late early to early middle pliocene 4 3 ma these episodes encompassed changes which were most probably induced by geodynamic events primarily related to the relative motions of the african arabian and eurasian plates in turn the plate motions are assumed to have triggered discrete steps in the regional kinematics and geodynamics that governed the palaeogeographic evolution of the peri tethys platforms and the intermediate domains of the african eurasian plate boundary zone

bryozoan beds in northern italy as a shallow water expression of environmental changes during the oligocene isotope event 1 abstract shifts in carbonate producing biotic communities in the geological record provide evidence of past environmental changes in the neritic realm the shallow marine calcare di nago formation exposed in the san valentino section northern italy covers the late eocene and earliest oligocene the succession is characterized by the occurrence of light dependent biota such as coralline algae and larger benthic foraminifera in the uppermost part of the section however the fossil association is dominated by bryozoans which are filter feeder organisms this ca 12 m thick interval locally contains up to 86 bryozoans while coralline algae as well as larger benthic foraminifera are absent coralline algae and nummulitid foraminifera recover in the upper part of the bryozoan beds whereas orthophragminids do not recover the gradual disappearance of larger foraminifera and coralline algae within the bryozoan dominated deposits is coeval with a pronounced positive shift in 13c based on its biostratigraphic position this positive shift is interpreted to be linked to the positive shift in 13c recognized in deep sea records shortly above the eocene oligocene boundary which in turn is associated to the positive shift in 18o leading to the oi 1 oligocene isotope event 1 cooling phase total phosphorus content increases in the bryozoan beds suggesting enhanced nutrient supply to the neritic ecosystem this phosphorous peak is coeval with the globally recognized increment in ocean productivity around the oi 1 and 13c positive shift thus disappearance of light dependent biota and the dominance of bryozoans in the platform carbonates studied are interpreted to result not necessarily from a deepening of the depositional environment but from the combination of lower sea surface temperatures and the deterioration of underwater light conditions on account of elevated turbidity in surface waters resulting from enhanced primary productivity as bryozoan beds occur in several italian localities around the eocene oligocene boundary they are interpreted to represent the regional expression of neritic carbonate depositional systems to global environmental changes occurring at the dawn of an ice house earth

late cretaceous and cenozoic intra plate compressional deformations in the alpine foreland a geodynamic model abstract the mesozoic grabens and wrench induced troughs of western and central europe developed in response to triassic early cretaceous intra plate tensional stresses which affected the arctic north atlantic and the tethys borderlands during the rifting phase preceding the opening of the respective oceans this resulted in the fragmentation of the continental crust of the alpine foreland during the late cretaceous and tertiary alpine orogeny collision related compressive stresses exerted on the foreland induced the reactivation of these fracture systems causing the inversion of mesozoic grabens and the uplifting of major basement blocks at distances up to 1300 km to the north of the present alpine deformation front the structural style of these inverted basins and basement uplifts is indicative of compressional and transpressional deformations the total amount of crustal shortening associated with these deformations is unlikely to exceed a few tens of kilometres these displacements require a coupling between the foreland and the orogen at the alpine a subduction zones and within the foreland a decoupling at intra crustal levels between the crust and mantle and or at deeper lithospheric levels the example of the alpine foreland indicates that compressive stresses inducing major deformations can be transmitted from a collisional plate boundary through continental lithosphere over distances of up to 1300 km circumstantial evidence suggests that collision related compressive stresses not large enough to give rise to significant deformations can be transmitted through continental lithosphere over even greater distances

late cenozoic burial history and dynamics of the northern caucasus molasse basin implications for foreland basin modelling abstract the collisional history of the caucasus segment of the alpine himalayan fold belt started at the end of the eocene the associated development of the northern caucasus foreland basin occurred during two syn collisional stages each displaying different subsidence patterns the 34 16 ma maikopian or pre foreland stage displays a long wavelength subsidence of a broad area whereas the 16 0 ma foreland stage displays asymmetrical foreland subsidence the first is correlated with the termination of subduction in the southern area and can be associated with mantle flow induced by the re equilibration of the subducted slab the along strike configuration of the second molasse basin stage contradicts the hypothesis in which topographical loading is considered to be the main control on foreland subsidence there is a clear anti correlation between basin depths and orogen heights the deepest parts of the basin are at the tips of the orogen where mountain heights are negligible while the area adjacent to the highest mountains central caucasus is uplifted the influence of other types of loading in foreland basin development has therefore been investigated and it has been possible to find a good fit with both gravity and basin architecture by including only two additional model parameters into the model these are crustal and lithospheric thickening thinning the results demonstrate that crustal thickening and removal of lithospheric roots are responsible for supporting the high central caucasus mountains and uplift of adjacent areas the subsidence of the basins at the orogen tips is explained by loading of lithospheric roots both effects are important in the geographically intermediate areas in general it is concluded that topography should not be considered as the main control on foreland subsidence but only as one of several counterbalancing mechanisms the existing flexural model therefore needs improvements such that it can be related directly to subsurface loading by real structures and processes during collision

tectonostratigraphy of the west alpine foreland correlation of tertiary sedimentary sequences changes in eustatic sea level and stress regimes abstract analysis of the tertiary depositional history of the west alpine foreland shows that its different basins were governed by essentially synchronous tectonostratigraphic scenarios the tectono sedimentary records of the west alpine foredeep and molasse basin and the rhone and massif central grabens demonstrate successions of tectonic deformation events and so called cenozoic rift and foredeep crf sequences which correlate to both changes in eustatic sea level and coeval modification in foreland stress regime since correlative successions developed in the north alpine foreland it seems likely that the western and northern alpine foreland stress fields were repeatedly modified at the same time compressional stresses associated with the intermittent tectonic and sedimentary changes in the foreland originated firstly from the alpine and pyrenean orogens in conjunction with the episodic history of the foreland stress regime the syn orogenic accumulation of widespread tectono sedimentary sequences reflects sequential kinematic events in the adjacent mountain chains the apparent synchroneity of the tectonostratigraphic events in the principal basins of the west alpine foreland testifies for a common geodynamic cause for the occurrence of correlative series of widespread tectonic phases and crf subdivisions

late cenozoic base level variations of the caspian sea a review of its history and proposed driving mechanisms abstract the caspian sea is characterized by significant variations in its base level during the late cenozoic and provides an important repository for long term records of both regional climate and tectonics due to its position within the interior of the eurasian continent and at the northern margin of the ongoing arabia eurasia collision zone the caspian also serves as an important moisture source for eastern eurasia including the northern tibetan plateau and thus the history of caspian base level variations represents an important and poorly understood constraint on paleoclimate reconstructions throughout eurasia prior work in the caspian region has largely focused on developing biostratigraphic age divisions and investigating the history of connection between the caspian black and mediterranean seas as well as the global ocean recent geochronologic work in the caspian and related basins has questioned previous correlations of hydrologic events in these different basins as a result prior estimates of the chronology and magnitude of caspian sea level variations may be incorrect here we synthesize previous work to develop a new caspian base level curve starting at the beginning of the meotian regional stage 7 ma we also present a new synthesis of potential driving mechanisms for the large variations in caspian base level and speculate on a possible cause for the enigmatic akchagyl transgression this synthesis highlights the dynamic range of caspian sea level which varied from 200 m above to in excess of 1000 m below its current level during the late cenozoic and provides a basis for future work investigating the tectonic and climatic drivers behind variations in caspian base level

neogene tectonic evolution of the southwestern alboran basin as inferred from seismic data off morocco the southwestern part of the western mediterranean alboran basin including part of the alboran ridge xaouen bank was investigated through the analysis of 28 intersecting multichannel seismic lines the seismic stratigraphy is tied to the amoco well el jebha 1 five seismic units or subunits are described from the quaternary to the middle and lower miocene the acoustic basement is interpreted to be mainly paleozoic and triassic metamorphic rocks of the alboran domain nappes and in places middle miocene messinian calc alkalic volcanics in the depocenters the thickness of the sedimentary infill mostly clays and turbidites exceeds 9 km normal faults of middle miocene tortonian age are broadly parallel to the coast and dip either seaward or landward they were mostly inverted during pre and post messinian episodes of compression which formed a set of en echelon north verging faulted folds in the alboran ridge area in relation with sinistral movement along the offshore projection of the jebha fault after pliocene subsidence a final episode of compression reactivated the earlier folds and pushed the alboran ridge onto the moroccan slope the complex structural history suggests many structural and stratigraphic potential hydrocarbon traps a high resolution seismic survey could lead to the definition of new exploration plays

chronology causes and progression of the messinian salinity crisis the messinian salinity crisis is widely regarded as one of the most dramatic episodes of oceanic change of the past 20 or so million years 1 3 earliest explanations were that extremely thick evaporites were deposited in a deep and desiccated mediterranean basin that had been repeatedly isolated from the atlantic ocean1 2 but elucidation of the causes of the isolation whether driven largely by glacio eustatic or tectonic processes have been hampered by the absence of an accurate time frame here we present an astronomically calibrated chronology for the mediterranean messinian age based on an integrated high resolution stratigraphy and tuning of sedimentary cycle patterns to variations in the earth s orbital parameters we show that the onset of the messinian salinity crisis is synchronous over the entire mediterranean basin dated at 5 96 0 02 million years ago isolation from the atlantic ocean was established between 5 59 and 5 33 million years ago causing a large fall in mediterranean water level followed by erosion 5 59 5 50 million years ago and deposition 5 50 5 33 million years ago of non marine sediments in a large lago mare lake sea basin cyclic evaporite deposition is almost entirely related to circum mediterranean climate changes driven by changes in the earth s precession and not to obliquity induced glacio eustatic sea level changes we argue in favour of a dominantly tectonic origin for the messinian salinity crisis although its exact timing may well have been controlled by the 400 kyr component of the earth s eccentricity cycle

the relative mobility of u th and ra isotopes in the weathered zones of the eye dashwa lakes granite pluton northwestern ontario canada radioisotope activity ratios of weathered surface rocks from the eye dashwa lakes granite pluton show that in the 238u decay series 226ra has been leached more rapidly than the grandparent 234u and 238u isotopes the observation of 238th232th disequilibria in the 232th decay series shows that either 228th half life of 1 9 yrs or 228ra half life of 5 75 yrs have been removed from these rocks very rapidly indeed isotope ratios of separated mineral fractions appear to show that whereas uranium tends to be removed from all mineral fractions ra is strongly readsorbed onto feldspars presumably as these undergo alteration to clay minerals this necessitates making a distinction between intermineral mobility of u or ra and the net loss of u or ra from the whole rock an attempt has been made to model quantitatively the transport rate of ra though with little success failure of the modelling appears to indicate that the mobility of 228ra is higher than might be predicted by the mobility of 226ra that is the two isotopes are not strict analogues of one another in their response to initial weathering

ash shutbah a possible impact structure in saudi arabia we have investigated the ash shutbah circular structure in central saudi arabia 21 degrees 37n 45 degrees 39e using satellite imagery field mapping thin section petrography and x ray diffraction of collected samples the approximately 2 1km sized structure located in flat lying jurassic tuwaiq mountain limestone has been nearly peneplained by erosional processes satellite and structural data show a central area consisting of dhruma formation sandstones with steep bedding and tight folds plunging radially outward open folding occurs in displaced younger tuwaiq mountain limestone formation blocks surrounding the central area but is absent outside the circular structure an approximately 60cm thick unique folded and disrupted orthoquartzitic sandstone marker bed occurring in the central area of the structure is found 140m deeper in undisturbed escarpment outcrops located a few hundred meters west of the structure with exception of a possible concave shatter cone found in the orthoquartzite of the central area other diagnostic shock features are lacking some quartz rich sandstones from the central area show pervasive fracturing of quartz grains with common concussion fractures this deformation was followed by an event of quartz dissolution and calcite precipitation consistent with local sea or groundwater heating the combination of central stratigraphic uplift of 140m concussion features in discolored sandstone outward dipping concentric folds in the central area deformation restricted to the rocks of the ring structure a complex circular structure of 2 1km diameter that appears broadly consistent with what one would expect from an impact structure in sedimentary targets and a possible shatter cone all point to an impact origin of the ash shutbah structure in fact the ash shutbah structure appears to be a textbook example of an eroded complex impact crater located in flat lying sedimentary rocks where the undisturbed stratigraphic section can be studied in escarpment outcrops in the vicinity of the structure less

the red sea 50 years of geological and geophysical research abstract the red sea displays lithosphere that is in transition from rifting to drifting and therefore provides enormous opportunity to understand incipient seafloor spreading development despite more than 50 years of extensive geological and geophysical research there remains significant conjecture concerning the timing of sea floor spreading initiation the extent of spreading along the axis of the red sea and the geodynamic processes responsible for the onset of crustal extension red sea tectonic models based on geological data are dominated by single stage rift models involving protracted stretching of continental crust followed by sea floor spreading at ca 5 ma and include both asymmetric and symmetrical extension models geophysical data suggest that an oceanic crust occurs beneath the red sea shelves although exactly how this crust has evolved remains undecided equally arguments have been made in favor of the sedimentary shelves forming on extended continental crust and that oceanic crust is restricted to the present day red sea axial valley however our synthesis shows that none of the models proposed so far is applicable to the entire red sea basin the distribution and timing of the red sea crustal extension and sea floor spreading may have been influenced by subduction related far field forces due to complex plate interactions along the northern edge of the arabian plate during early miocene our reassessment suggests that following the arrival of the afar plume the southern red sea underwent rapid extension culminating in the transition from rifting to seafloor spreading which stalled during the early miocene in the central red sea due to either slowing of the convergence between arabia and eurasia or the onset of the arabian plate passive margin collision with eurasia off axis magmatism is focused on the arabian margin and afar depression and has been episodically active since the miocene we consider a formation of the red sea as a hybrid process involving both active and passive rifting

palynomorphs from a lacustrine sequence provide evidence for palaeoenvironmental changes during the early miocene in central anatolia turkey pollen samples belonging to 54 plant taxa from 32 intervals in a 59 m thick lacustrine sequence in the harami open pit lignite mine in konya province turkey were studied to evaluate early miocene aquitanian changes in vegetation climate and environments in central anatolia the regional vegetation consisted of forests whose composition changed through time an abundance of sub tropical and warm temperate mainly deciduous trees in the lower part of harami section indicates a warm and humid climate in the region during the earliest miocene a trend towards cooler and drier conditions driven by a combination of regional and local factors is reflected by the sequential establishment of two kinds of coniferous forests a cedar cedrus dominated forest in the middle part of the section followed by a mixed cedar and pine pinus forest in the upper part of the section the high percentages of cedrus in the middle and upper portions of the harami section suggest that high elevation coniferous forests

paleoceanography and climate of the badenian middle miocene 16 4 13 0 ma in the central paratethys based on foraminifera and stable isotope δ 18 o and δ 13 c evidence benthic foraminifera and stable isotopes analyses revealed changes emerging in the paleoceanographic scenery in the paratethys the percentage of inbenthic oxyphylic taxa and diversity in the benthic foraminiferal assemblage showed increasing food supply organic matter decreasing oxygen level and growing stress on the sea floor oxygen isotopes measured in planktonic and benthic foraminifera pointed to strengthening stratification during the badenian period the carbon isotopes indicated intensified accumulation of light marine organic matter this increasing stratification trend is especially pronounced by late badenian 13 5 13 ma when surface water oxygen isotope values are rather negative a simple two layer circulation model was worked out for the badenian paratethys explaining these characteristic environmental changes an antiestuarine lagoonal circulation is assumed for the central paratethys during the early 16 4 15 ma and mid badenian 15 13 5 ma the mid badenian period of time comprises the short episode of evaporite formation in the carpathian foredeep and the transylvanian basin evidence presented here supported a reversal of circulation to estuarine type after the deposition of salts by late badenian 13 5 13 ma the early badenian antiestuarine circulation is suggested to associate with the high temperatures of the mid miocene climatic optimum and the late badenian estuarine circulation with the cooler period following it

oligocene miocene basin evolution in se anatolia turkey constraints on the closure of the eastern tethys gateway the oligocene miocene was a time characterized by major climate changes as well as changing plate configurations the middle miocene climate transition 17 to 11 ma may even have been triggered by a plate tectonic event the closure of the eastern tethys gateway the marine connection between the mediterranean and indian ocean to address this idea we focus on the evolution of oligocene and miocene foreland basins in the southernmost part of turkey the most likely candidates to have formed this gateway in addition we take the geodynamic evol ution of the arabian eurasian collision into account the musand elazog u basins located to the north of the bitlis zagros suture zone were most likely connected during the oligocene the deepening of both basins is biostratigraphically dated by us to occur during the rupelian early oligocene deep marine conditions between 350 and 750 m prevailed until the chattian late oligocene when the basins shoaled rapidly to subtidal intertidal environment in tropical to subtropical conditions as indicated by the macro fossil assemblages we conclude that the emergence of this basin during the chattian severely restricted the marine connection between an eastern indian ocean and western mediterranean marine domain if a connection persisted it was likely located south of the bitlis zagros suture zone the kahramanmarasbasin located on the northern arabian promontory south of the bitlis zagros suture zone was a foreland basin during the middle and late miocene possibly linked to the hatay basin to the west and the lice basin to the east our data indicates that this fore land basin experienced shallow marine conditions during the langhian followed by a rapid dee pening during langhian serravallian and prevailing deep marine conditions between 350 and 750 m until the early tortonian we have dated the youngest sediments underneath a subduc tion related thrust at c 11 ma and suggest that this corresponds to the end of underthrusting in the kahramanmarasregion i e the end of subduction of arabia this age coincides in time with the onset of eastern anatolian volcanism uplift of the east anatolian accretionary complex and the onset of the north and east anatolian fault zones accommodating westward escape tec tonics of anatolia after c 11 ma the foreland basin south of the bitlis formed not or no longer a deep marine connection along the northern margin of arabia between the mediterranean sea and the indian ocean we finally conclude that a causal link between gateway closure and global climate change to a cooler mode recorded in the mi3b event d 18 o increase dated at 13 82 ma cannot be supported

the rotation of arabia and the levant fault system abstract we establish the kinematics of the rotation of arabia with respect to africa and show that the rotation rate of africa increased by a factor of about four in late serravallian time about 12 13 ma ago we discuss evidence that oceanic accretion started simultaneously in the gulf of aden and in the red sea at this time it is also at this time that the levant and anatolian fault systems were initiated our initial reconstruction of the red sea rift in late oligocene early miocene time approximately superposes the present shore lines which coincide with the mid point of the zones of rapid crustal thinning the future continental slopes the amount of extension during the early phase of continental rifting is obtained by assuming that the total volume of continental crust is conserved during extension and by checking these estimates through closure around the sinai triple junction in the late miocene the southern evant fault zone was a zone of distributed shear deformation through counterclockwise block rotation extending soul h ward within the northernmost red sea since the early pliocene the shear motion has been localized within the gulf of aqaba changing the tectonic pattern in the northern red sea

new tropical carcharhinids chondrichthyes carcharhiniformes from the late eocene early oligocene of balochistan pakistan paleoenvironmental and paleogeographic implications new selachians sharks and rays have been collected from several late eocene and early oligocene marine localities in the bugti hills balochistan pakistan two new species of requiem sharks close to the recent bull shark are described carcharhinus balochensis and carcharhinus perseus the rest of the fauna is notable for the strong representation of carcharhiniformes these selachian faunas represent a unique tropical association for the oligocene period and one of the first modern tropical selachian faunas with modern taxa such as the two new species of bull sharks negaprion sp and one of the first occurrences of sphyrna sp moreover these faunas permit paleoenvironmental interpretation of adjacent land masses the relatively modern aspect of these faunas compared with other contemporaneous and younger selachian associations from atlantic and mediterranean seas suggests biogeographic isolation of selachian communities living in eastern and western parts of the tethys before its final closure during the early middle miocene

the minorca basin a buffer zone between the valencia and liguro provencal basins nw mediterranean sea detailed analyses of seismic profiles and boreholes in the valencia basin vb reveal a differentiated basin the minorca basin mb lying between the old mesozoic valencia basin sensu strico vbss and the young oligocene liguro provencal basin lpb the relationship between these basins is shown through the correlation of four miocene to present day megasequences the central and north balearic fracture zones cfz and nbfz that border the mb represent two morphological and geodynamical thresholds that created an accommodation in steps between the three domains little to no horizontal neogene movements are found for the ibiza and majorca islands in contrast the counterclockwise movement of the corso sardinian blocks induced a counterclockwise movement of the minorca block towards the se along the cfz and nbfz during the exhumation of lower continental crust in the lpb this new understanding implies pure neogene vertical subsidence in the vbss and places the alkapeca northeastward of the present day alboran area

magnetostratigraphy and radio isotope dating of upper miocene lower pliocene sedimentary successions of the black sea basin taman peninsula russia abstract we present a new chronology for the upper miocene to pliocene deposits of the black sea basin based on high resolution magnetostratigraphic data coupled with 40 ar 39 ar dating from the 475 m long zheleznyi rog section on the taman peninsula russia this section comprises the stratigraphic interval of the khersonian to kimmerian regional stages of the eastern paratethys our magnetostratigraphic record is based on biogenic and early diagenetic greigite components and yields a magnetostratigraphic sequence of 8 polarity zones a volcaniclastic ash layer at the upper part of the khersonian is radio isotopically dated at 8 69 0 18 ma the age of the khersonian meotian transition arrives at 8 6 or 8 2 ma which is significantly younger than earlier estimates the new age has important consequences for the hipparion datum in the eastern paratethys and implies that all vallesian fossil sites are younger than 11 2 ma the meotian stage has a total duration of 2 2 to maximum 2 6 myr and is marked by multiple erosional events the end of the paratethys sea is dated at 5 5 ma when the black sea becomes isolated from the caspian sea the dacian basin and the mediterranean

oligocene uplift of the western greater caucasus an effect of initial arabia eurasia collision the greater caucasus is europe s largest mountain belt significant uncertainties remain over the evolution of the range largely due to a lack of primary field data this work demonstrates that depositional systems within the oligocene early miocene maykop series on either side of the western greater caucasus wgc display a similar provenance and divergent palaeocurrents away from the range constraining a minimum age for the subaerial uplift of the range as early early oligocene an eocene oligocene hiatus basal oligocene olistostromes and a marked increase in nannofossil reworking also point to initial deformation in the earliest oligocene the initial uplift of the wgc occurred during the final assembly of the tethysides to its south uplift commenced after the late eocene final suturing of northern neotethys and during the initial collision of arabia with the southern accreted margin of eurasia this suggests that compressional deformation was rapidly transferred across the collision zone from the indenting arabian plate to its northern margin

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

late neogene evolution of the taza guercif basin rifian corridor morocco and implications for the messinian salinity crisis abstract magnetostratigraphic and biostratigraphic results are presented from neogene deposits in the taza guercif basin located at the southern margin of the rifian corridor in morocco this corridor was the main marine passageway which connected the mediterranean with the atlantic during messinian times correlation of the biostratigraphy and polarity sequence of the taza guercif composite section to the astronomical time scale allows an accurate dating of three subsequent events in the rifian corridor 1 the oldest marine sediments marking the opening of the rifian corridor were deposited at 8 ma at this age a deep 600 m marine basin developed in the taza guercif area marked by deposition of precession controlled turbidite marl cycles 2 paleodepth reconstructions indicate that a rapid 5 m ka shallowing of the marine corridor took place at the tortonian messinian boundary at an age of 7 2 ma this shallowing phase is primarily related to active tectonics although a small glacio eustatic sea level lowering also took place 3 the taza guercif basin was emergent at an age of 6 0 ma and subsequently continental sedimentation continued well into the early pliocene we suggest that shallowing and restricting the marine passageway through the rifian corridor actually initiated the messinian salinity crisis well before the deposition of the messinian evaporites in the mediterranean

neogene tectonic and stratigraphic events in the gulf of suez rift area egypt abstract the gulf of suez neogene syn rift section contains at least five datable intra basinal unconformities or stratigraphie hiatuses these events and associated changes in sedimentary sequences seen in the basin can be related to changes in suez rift subsidence miocene eustasy and the tectonic effects of adjacent red sea and dead sea rifting the first hiatus spans oligocene to earliest miocene time and separates syn rift from pre rift strata throughout the region this erosional event resulted from regional emergence during the oligocene and the initiation of suez rifting a second hiatus from 21 19 ma separates the poorly dated shallow marine nukhul formation of aquitanian to early burdigalian age from the overlying upper bathyal shales of the middle burdigalian to langhian nn3 5 rudeis formation this hiatus resulted from both a brief lowstand in early burdigalian sea level and increased suez rift related tectonism this event climaxed with the rapid tectonic subsidence that established deep marine conditions by 19 ma a third major event occurs within the rudeis at 17 ma nn4 n7 and marks the initiation of uplift of i he rift shoulders and margins and decelerated subsidence or even minor uplift in the axial trough hiatuses are seen over paleohighs e g tilted fault blocks whereas coarse elastics are deposited in more basinal areas in submarine fans and as turbidites a fourth unconformity at 14 ma separates the middle miocene kareem formation from overlying anhydrites and open marine shales of the belayim formation minor tectonic uplift throughout the suez region resulted from this event and a sill was established between the mediterranean and suez basins allowing cyclic anhydrite marl deposition from 14 to 11 ma this post kareem event may be the sedimentary response to initiation of movement along the dead sea aqaba transform a sharp drop in sea level at 11 ma restricted the suez basin even more and marked the initiation of massive halite precipitation in the central and southern suez well south of the sill area a final major neogene event occurs at the miocene pliocene boundary and is marked by a major unconformity caused by tectonic uplift this tectonic pulse is related to initiation of red sea sea floor spreading and acceleration of sinistral motion along the dead sea aqaba transform at 5 ma this event establishes the marine connection with the red sea and the sedimentary environments seen in the gulf of suez today