present day kinematics of the mediterranean a comprehensive overview of gps results i combine recently published gps results to derive a geodetic horizontal velocity field consistent at the scale of the mediterranean and the surrounding alpine belts the velocity field is then used to discuss the boundary conditions around each major deforming area in the mediterranean to describe the main patterns of motion and deformation to critically review the existing kinematics models and to finally point out the main unresolved kinematics questions strain rate in europe north of the alpines belt is dominated by the signature of the glacial isostatic adjustment and tectonic strain remains below the current accuracy of gps results in the western mediterranean deformation is restricted to the betics the alboran and the morrocan rif with west to southwestward motion with respect to iberia which is part of stable europe shortening consistent with the relative nubia eurasia plate motion is found throughout the maghrebides but the distribution of deformation in northern africa remains largely unknown the central mediterranean is dominated by the counter clockwise rotation of the adriatic the junction between the southern adriatic domain and nubia has yet to be firmly established the deformation over a wide area east of the maghrebides in tunisia and the gulf of sirte in libya still remains to be quantified in the eastern mediterranean the velocity field is dominated by a general anti clockwise rotation and a general trend towards the hellenic trench with velocity magnitude increasing with decreasing distances from the trench this trend is observed not only in the aegean and anatolia but also in the southern balkans geodetic results emphasize that the convergence of the nubia and arabia plates towards eurasia directly controls the deformation across only very few segments along the plate boundary zone additional processes are therefore required to explain the observed velocity field and deformation pattern

the messinian event on the margin of the mediterranean sea in the nice area southern france abstract seismic reflection profiles have been used to map the messinian erosion surface and associated basin margin deposits on the continental margin off nice a palaeovalley extends seaward from the incised var palaeovalley mapped on land the lower part of this valley is filled by an acoustically incoherent unit with a flat top and steep slope into the basin this unit is interpreted as a coarse grained deltaic deposit that accumulated synchronously with the upper messinian evaporites in a ponded lake basin two submersible dives on strategic outcrops supported the interpretation of the seismic profiles we examined and sampled outcrops of probably early tertiary sandstones underlying the messinian erosion surface and of a fining up predominantly conglomeratic sequence that fills messinian channels on the continental slope and probably overlies the deltaic deposits these conglomerates pass up into early pliocene marls and have turbidite sedimentary structures these are prodeltaic deposits formed during the transgression at the end of the messinian based on seismic facies mapping sampling and submersible observations a palaeogeographic reconstruction of the area is proposed a basal erosion surface including the var palaeovalley represents extreme dessication of the western mediterranean and was followed by accumulation of the main messinian salt following this a lake was ponded in the ligurian basin with accumulation of evaporites and shales a gilbert type delta prograded into the basin from the var palaeovalley relative sea lake level lowering is estimated to be about 1200 m at this time there has been little faulting on the margin since the early pliocene transgression but there is estimated to have been about 800 m of flexural subsidence due to both thermal subsidence and water loading

tension gash like back arc basin opening and its control on subduction rollback inferred from tertiary faulting in sardinia 1 the tertiary reactivation of the paleozoic basement in ne sardinia is shown to reflect transtensional back arc tectonics related to the western mediterranean subduction rollback during the algero provencal basin opening the left lateral nuoro fault which is the prevailing structure in central sardinia operated as radial transfer between the west sardinian rift and northern tyrrhenian basin subsequently it contributed to a tension gash like opening of the southern tyrrhenian basin as conjugate fault to a right lateral fault set in se sardinia resulting antithetic rotations with respect to the arc are revealed by reoriented dikes in the basement the tension gash like opening of the southern tyrrhenian basin determined the gulf shape of the east sardinian margin and the arc shape of its calabrian counterpart this structural control on the southern tyrrhenian rollback scenario suggests that tension gash like opening of back arc basins represents an intrinsic aspect of subduction rollback

crustal features along a w e tyrrhenian transect from sardinia to campania margins central mediterranean abstract the tyrrhenian sea is a neogene back arc basin formed by continental extension at the rear of the eastward migrating apennine subduction system its central part generated from tortonian to pliocene includes the sardinia rifted margin to the west an area with large volcanoes in the deep central sector and the campania rifted margin to the east a reprocessing of some 2000 km of mcs lines a new swath bathymetric map and a review of previous geological and geophysical data allow to analyse the nature and distribution of continental vs oceanic crust in this area which evolved in a short time span the central portion of the southern tyrrhenian sea is characterized by moho at about 10 km depth north of magnghi and vavilov smts this thinned crustal domain include a wide continent ocean transition with the occurrence of extensional allochthons and of serpenitinzed sub continental mantle recalling other well known rifted margins as the iberia one sectors floored by oceanic crust should occur mainly in the southern part of the study area but they do not appear related to discrete spreading ridges the continent ocean boundary cannot be drawn unequivocally in the area due also to the occurrence of widespread and huge magmatic manifestations not related to oceanic spreading these portions of the southern tyrrhenian sea represents therefore a complex oceanic back arc basin surrounded by magma rich rifted continental margins the abundant igneous manifestations and the very high stretching rates observed in the area may be related to the fact that the present tyrrhenian area was occupied by an orogenic domain affected by shortening until middle miocene times which is just before the late miocene onset of back arc extension the lithosphere in the region had then to be rheologically weak abundant generation and ascent of magmas mostly of ocean island basalt type was favoured by the large lithospheric permeability induced by strong extensional deformations

structure and present day compression in the offshore area between alicante and ibiza island eastern iberian margin abstract this study deals with the structure and recent deformation of the eastern iberian margin extending from basement to seafloor and including the south western margin of the valencia basin the alicante shelf the ibiza channel and its southern margin descending into the algerian basin this area underwent a complex tectonic evolution linked to the back arc opening of the north western mediterranean and the concomitant contraction of the betic belt due to the collision with blocks located between africa and europe this oligo miocene structural heritage gave rise to a complex and continuous deformation through times including late miocene post orogenic extension and pliocene to quaternary compression in the western balearic area and coeval extension in the valencia basin this study presents maps of the depth to basement and base of the pliocene as well as bathymetry data and seismic lines which provide a precise integrated 3d study of the offshore domain it reveals a major reactivation of the area represented by the n80 to n60 trending structures small discontinuous folds and thrusts in the ibiza channel and a large flexure on the alicante shelf the structures are picked out by erosion surfaces or deposits linked to the messinian salinity crisis msc these markers are ubiquitous in the seismic sedimentary sequences and record the lateral and vertical deformation active from the messinian salinity crisis to the present the contraction in the western iberian margin and concomitant extension in the southern valencia basin are consistent with the regional stress field as determined from the focal mechanisms of offshore earthquakes or recent gps measurements the tectonic compression of the studied area casts doubt on the eventual propagation of the present day compressive stress from the algerian margin to the western balearic promontory

fluid geochemistry of the sardinian rift campidano graben sardinia italy fault segmentation seismic quiescence of geochemically active faults and new constraints for selection of co2 storage sites abstract sardinia is typically seismically quiescent displaying an almost complete lack of historical earthquakes and instrumentally recorded seismicity this evidence may be in agreement with the presence of a ductile layer in the northern sector of the island as suggested by the he isotopic signature in fluids rising to the surface through quiescent fault systems the fault systems have been found to be segmented and therefore isolated in fluid circulation the study of fluid behaviour along fault systems becomes strategically important when applied to solve some geological risk assessments such as rn indoor or to define geological structures like potential co 2 storage sites both of these have been recently requested by the exploitation in italy of the euratom directive and the evolution of the kyotoprotocol policy four water dominated hydrothermal areas of sardinia located along regional fault systems were considered campidano graben tirso valley logudoro and casteldoria a fluid geochemical survey was carried out taking into account physical chemical and environmental parameters major elements within gaseous and liquid phases a few minor and trace elements selected isotope ratios 2 h 18 o 13 c 3 he 4 he 222 rn concentration and some dissolved gases two different fluids have been recognised as regards both water chemistry and dissolved gases i co 2 rich gases poor in he and rn with a relatively high 3 he 4 he ratio up to r r a 2 32 associated with na hco 3 cl thermal and cold groundwater ii gases rich in he and n 2 poor in co 2 and rn with a low 3 he 4 he ratio associated with alkaline thermal and cold waters the distribution of these two groups of fluids characterises the sardinian tectonic systems in fact gas fluxes are not homogeneous being mainly related to the different fault segments and to the areas where quaternary basalts crop out the underground geochemical evolution of the sardinian fluids as a function of the geological and tectonic systems provides some suggestions for solving one of the most important problems co 2 geological sequestration in order to reduce the co 2 excess produced by human activity the best geological disposal sites are reservoirs with low hydraulic conductivity sealed to fluid movement or aquifers characterised by maximum ph buffering capacity of their mineralogical matrix the knowledge of the role of faults as permeability barriers or as deep fluid uprising pathways is prerequisite

on the origin of the strait of gibraltar most interpretations of the early pliocene opening of the strait of gibraltar involve a tectonic process however no tectonic structure of this age has been unequivocally documented that could account for such a hypothesis on the other hand the sea level drop of the mediterranean during the messinian salinity crisis has dramatically enhanced continental erosion and in particular regressive fluvial erosion we show that such erosional process inevitably developed in the gibraltar area we finally propose that regressive fluvial erosion was at the origin of the opening of the strait of gibraltar

a review on the driving mechanism of the tyrrhenian apennines system implications for the present seismotectonic setting in the central northern apennines abstract the formation of the tyrrhenian apennines system has been characterized by a complex distribution of major tectonic events such as opening of basins migration and distortion of orogenic belts retreat of trench zones stopping of consuming processes and starting of new subductions the various aspects of each event such as timing location dimension and deformation style impose important constraints on the genetic mechanism in this work we argue that the numerous constraints implied by all events together may be plausibly and coherently explained as effects of the convergence of the confining africa arabia and eurasia plates crucial evidence for discriminating among the various geodynamic hypotheses so far advanced is provided by the structural tectonic information recently provided by crop seismic sections in the study area the proposed evolutionary history is illustrated by several paleogeographic maps which provide a more detailed reconstruction than previous attempts particular attention is paid to describing the tectonic setting developed since the middle pleistocene in the apennines belt and its connection with seismic activity

the nile deep sea fan an example of interacting sedimentation salt tectonics and inherited subsalt paleotopographic features abstract structural analysis of the nile deep sea fan ndsf indicates that post miocene deformation is largely controlled by down slope movement above a messinian salt layer in contrast to other similar systems the ndsf shows significant lateral asymmetry and three distinct provinces can be recognized regional variations in salt thickness and base salt geometry within the system have led to the presence of structures typical of both gravity gliding and gravity spreading trends of structures within the western and central parts of the ndsf are consistent with forming due to gravity gliding processes this pattern contrasts with that in the eastern ndsf that seem to be much more consistent with deformation due to gravity spreading observed differences in structural style across the ndsf can be related directly to the paleomorphological evolution of the nile cone during messinian time which is perhaps partly related to features that have been inherited from early mesozoic evolution of the north egypt passive margin in the east part of the ndsf the structural evolution has been significantly influenced by the proximity of eratosthenes seamount this large topographic buttress has served to both limit and deflect northeastward allochthonous advance of the messinian evaporites and has thus severely complicated deformation of the overlying plio quaternary sedimentary cover within the broad corridor that runs nnw sse and cuts obliquely across the modern bathymetry of the nile cone

salt tectonics and crustal tectonics along the eastern sardinian margin western tyrrhenian new insights from the metyss 1 cruise abstract the tyrrhenian sea is usually interpreted to be a neogene back arc basin that opened by continental rifting and oceanic spreading caused by the eastward migration of the apennine subduction system during miocene and pliocene times rifting of the southern tyrrhenian sea started first along the eastern sardinian margin during the middle to late miocene times including the messinian the metyss project aims at better constraining the relationships between crustal tectonics salt tectonics and sedimentation from messinian times to present day the metyss 1 cruise 2009 allowed to acquire about 1200 km of hr seismic reflection profiles along the eastern sardinian margin western tyrrhenian sea this data set clearly illustrates that this area has been highly dissected during the rifting stage by n s trending normal faults delineating ridges and basins as previously described the messinian seismic markers uu and mu locally display fan shaped stratal geometries but the mechanism responsible for such geometries salt tectonics or rifting has yet to be carefully deciphered we also mapped the spatial distribution of the mobile salt the highly variable thickness of the small confined salt basins may be related to the initial pre messinian basin geometry to the fact that salt deposition was syn rift or to salt movement southeastward salt tectonics is vigorous in unconfined basins and appears to have started early during the uu deposition more surprisingly our data demonstrate that some of the major faults have been significantly reactivated during the post rift period up to late quaternary time as shown by bathymetric scarps and associated debris flows moreover some of this post rift deformation can be evidenced within the plio quaternary sequence by a regional unconformity the post miocene deformation style varies greatly between different areas of the margin and can also be strongly influenced by the presence or absence of mobile messinian salt

structural evolution of the 41st parallel zone tyrrhenian sea the present study is based on the interpretation of more than 1300 km of 16 kj sparker seismic profiles recorded in july 1990 during the cruise t 41 of the geological institute of urbino the investigated area extends along the 41st parallel in the central tyrrhenian sea between the northern sardinian margin to the west and the latium campanian margin to the east this zone situated on continental crust marks the boundary between the northern tyrrhenian and the southern tyrrhenian domains a kinematic reconstruction is presented based on the age dating of the recognized structures i e normal faults reverse faults anticline and flower structures the evolution of the 41st parallel zone can be described in terms of polyphase tectonics characterized by different orientations of the stress field during time the direction of the normal fault trends turned clockwise striking ne sw in the late tortonian messinian e w in the early pliocene nnw sse in the late pliocene and n s during the quaternary the concurrence of compressional and strike slip deformations suggests oblique shear motions across the 41st parallel the occurrence of late pliocene quaternary tectonic activity in the northern tyrrhenian sea locally characterized by inversion tectonics suggests active mechanisms intraplate compression superimposed on the post rift subsidence

the italian cmt dataset from 1977 to the present abstract the ingv harvard european mediterranean regional centroid moment tensor rcmt catalog collects solutions routinely computed since 1997 for earthquakes with moderate magnitude 4 5 m 5 5 in the mediterranean region the database represents an extension to smaller magnitudes of the harvard global cmt catalog based on analysis of seismograms recorded at regional distance and modeling of intermediate period surface waves the catalog includes about 600 events 200 of which in the italian region this study extends the catalog back in time for the italian region as long as made possible by available digital data i e since 1977 with the same analysis and inversion method used for current seismicity as a result we present here 65 new moment tensors for years between 1977 and 1997 these solutions represent 45 of the total number of events analyzed the existing seismograms being often too scarce to allow a stable solution the new dataset includes events in many seismic zones where moderate seismicity had previously been scarcely documented e g the po plain the central to southern apennines and the adriatic sea the complete dataset including previously determined rcmts and cmts represents the seismic deformation in the italian area during the last 25 years

constraints on mantle circulation around the deforming calabrian slab 1 combining tectonics with seismological and geochemical data we reconstruct the deformation history of the presently narrow calabrian slab and the path of mantle circulation during the last 10 ma we show that during the slab deformation the mantle laterally flowed inside the back arc region permitting its retrograde motion and giving a seismological and volcanological record after 1 2 myr

extension and compression related basins in central italy during the messinian lago mare event abstract during the messinian lago mare event in the central mediterranean area compression and extension related basins developed as a consequence of the post tortonian evolution of the tyrrhenian apennines system all these syn tectonic sedimentary basins were characterized by different subsidence rates and sedimentary processes several sections located in different tectonic domains from the tyrrhenian to the adriatic margin of the apennine chain have been investigated s valentino in abruzzo citeriore roccamorice penscosansonesco roccacaramanico and le vicenne sections are located in compression related basins foreland basin system while the tolfa blera sections and the sedimentary succession of mondragone 1 well drilled in the garigliano coastal plain are located in extension related basins hinterland or back arc basins the recognition of ostracod assemblages with paratethyan affinities allows them to be referred to the messinian lago mare event loxoconcha djaffarovi zone this result allows us to consider the tyrrhenian rifting the accretion of the apennine thrust belt and the increase in subsidence rate during the flexuration of the foreland domain as synchronous processes due to the same geodynamical process taking into account the thicknesses of the analysed sedimentary basins different total subsidence rates have been computed for both the compression and extension related basins the syn rift basins that developed on the eastern margin of the northern tyrrhenian basin volterra val di fine and tolfa blera basins recorded a mean total subsidence rate of 1 25 mm a whereas higher subsidence rates affected the eastern margin of the central tyrrhenian basin 5 mm a garigliano coastal plain the differences in horizontal stretching and total subsidence rates that affected the tyrrhenian extensional area correspond to different migration rates of the apennine orogenic system in the northern 10 mm a and central apennines 40 mm a this difference in the total syn rift subsidence rate fits in well with the segmentation model of the tyrrhenian apennines system along a nne ssw lithosphere discontinuity which crosses the system from ancona northern apennines to the r selli lineament in the tyrrhenian basin

sardinia coastal uplift and volcanism the low variability of mis 5 5 sea level m i s marine isotopic stage with respect to the present day sea level allows the sardinian coast to be used as an eustatic reference for the entire mediterranean region this level is generally at 7 2 m above current sea level along the sardinian coast one sector along the orosei gulf eastern sardinia includes a characteristic and well conserved tidal notch that changes in elevation from 7 6 to 11 5 m over only 30 km tilting upwards towards the north generally height deviations of such a tidal notch would be due to tectonic or volcanic activity the sardinia coast however is considered to have too little tectonic activity and also too small post glacial rebound in order to explain the anomaly the remaining possibility is neogene quaternary continental and or submarine volcanic activity which we investigate as a possible cause for the observed anomalies in this paper our goal is to explain the anomaly by modelling recent volcanic loading or updoming related to magmatic intrusion emplacement we review the literature on the recent volcanic deposits both on shore and off shore and investigate to what extent volcanic loads can influence the coastline from a theoretical standpoint using the isostatic flexure model and a range of loads we find that the observed notch height anomaly cannot be explained by volcanic loading but must be produced by an upward welling due to the emplacement of volcanic material as produced for instance by a laccolith or batholith the upward movement could be related to the submarine volcano only recently detected or to a source located on the eastern sardinia coast near orosei

a proposal for the kinematic modelling of w dipping subductions possible applications to the tyrrhenian apennines system in w dipping subduction zones there is a general eastward progression of the back arc basin accretionary wedge foredeep complex with the forward progression early stages of the complex are revealed by slices of upper crust and sedimentary cover abandoned to the west left floating above a new section of mantle a major shear zone should form at the new moho separating upper crust slices of earlier accretionary stages and the eastward flowing mantle the mantle wedging at the top of the subduction plane could be responsible for the uplift of the central parts of the belt the retreating of the subduction hinge is interpreted as due to the push generated by the eastward mantle flow detected in the hot spot reference frame the foredeep depth is mainly a function of the radius of curvature of the subduction hinge the frontal wedge is constructed from the stacking of the upper layers of the subducting plate and the syntectonic clastics that fill the foredeep which are progressively involved in thrusting and later by extension in order to preserve volume balance the lithosphere of the eastern plate before subduction has to be the same size as that which has been subducted due to the longer length of the arc with respect to the original length of the linear margin between the two converging plates laterally stretched subducted lithosphere is predicted at depth w dipping subductions usually have a short life probably due to their inherent capability to produce new lateral heterogeneities of the lithosphere the thin back arc which are a key factor in controlling and generating new subductions both e and w dipping this model is applied to the apennines tyrrhenian sea system

on the asymmetry of turtle back growth anticlines turtle back anticlines are common structures that develop between facing listric growth faults rooted in a flat lying decollement seismic examples from the south atlantic margins show that whereas their external shape can by symmetric their internal structure is more generally asymmetric laboratory experiments on layered sand silicone models designed to study gravity gliding are used to examine the mode of development of turtle back anticlines the results provide information on the ways turtle back asymmetry develops the comparison between nature and experiments leads to the following conclusions the fact that turtle back anticlines often start symmetric and progressively become asymmetric is due to an increase in coupling between overlying brittle sediments and ductile salt layers the increase in coupling is also responsible for the transition in time and space from dominant seaward faulting to landward faulting for the turtle back anticlines which never pass through a symmetric stage the salt diapirs which separate blocks of the sedimentary cover rafted above the basal decollement at early stages of gravity gliding can play a significant role in the development of turtle back anticlines as suggested by previous authors the diapirs first rise and then fall our experiments confirm that diapir fall favours the wrapping of rafted blocks by synkinematic layers

miocene rotation of sardinia new paleomagnetic and geochronological constraints and geodynamic implications the miocene rotation of sardinia western mediterranean remains poorly constrained despite a wealth of paleomagnetic data primarily due to poor chronostratigraphic control however this rotation is contemporaneous with the opening of the liguro provencal back arc oceanic basin and its history is key to understanding the kinematics of opening of the western mediterranean we address this issue through paleomagnetic and 40ar 39ar geochronological investigations of miocene volcanic sequences in sardinia precise age control allows secular variation of the geomagnetic field to be evaluated these data provide constraints on the rotational history of this continental microplate sardinia rotated 45 counterclockwise with respect to stable europe after 20 5 ma aquitanian which is a marked increase over the estimate of 30 derived from prior paleomagnetic studies rotation was essentially complete by 15 ma about 30 of rotation occurred between 20 5 and 18 ma burdigalian corresponding to the period of maximum volcanic activity in sardinia the observed rotation validates palinspastic models derived from a morphological fit of basin margins and indicates high rates of opening up to 9 cm yr 1 in the southern part of the basin between 20 5 and 18 ma

messinian subaerial erosion of the proto nile delta abstract the evaporitic drawdown and subsequent dessication of the mediterranean basins during the messinian salinity crisis has been confirmed by detailed seismic mapping of the ensuing erosion surface in the nile delta region the basal messinian unconformity determined by seismic analysis and borehole correlation extends from almost sea level in the southern delta area to depths of at least 5 km in the nile cone the onlap of the contemporaneously deposited fluvio deltaic clastics of the qawasim formation occurs at between 2 5 to 4 km below present gradual initial drawdown of the mediterranean sea with occasional sudden sporadic falls is implied by the presence of entrenched meanders and impaired rejuvenation terraces in the nile canyon formed as the proto nile river cut down into the pre existing tortonian delta complex the former tortonian delta slope became an extensive linear erosional front with over 3 km of vertical relief the uppermost levels of which were protected by tabular oligocene basalt flows preserved as mesas and buttes the lower slopes were the site of coalescing piedmont fans fed by upper slope wadi systems the piedmonts merged into the qawasim fluvio deltaic deposits of the proto nile fluvial flood plain the subcrop beneath the basal messinian unconformity reveals a remarkable diversity of rock type each with its own distinctive control on the geomorphology and geometry of the ensuing messinian erosional surface fracture patterns within the oligocene basalts produced a trellis drainage network which became later captured by a dendritic system developed on less resistant prodelta shales of the former tortonian delta slope close study of seismic profiles clearly demonstrates that the basal messinian erosional disconformity can be traced northwards to depths of at least 2 5 3 0 km before becoming affected by later pliocene faulting this validates a deep dessication model for the evolution of the messinian evaporites

neogene evolution of the southwestern tyrrhenian sea sardinia basin and western bathyal plain abstract the reprocessing of mcs reflection lines and sampling data across the sw tyrrhenian basin from the sardinia tunisia strait sts to the orosei canyon line ocl show that the acoustic basement of the area is made by variscan crystalline metamorphic rocks covered by a thick sequence of sediments including the messinian interval the pre messinian sequence can be subdivided into three seismic intervals or subunits largely calibrated by sampling data the oldest pre messinian subunit is strongly deformed by compressional and or transpressional structures and the recovered samples are deep water arkosic sediments aquitanian in age however the whole interval may encompass a wider time span probably from late oligocene to langhian this subunit was laid down in a fore arc basin located between a volcanic arc sardinia and an accretionary wedge calabrian peloritanian kabilide or ck units prior to the collision of the latter elements with the continental margin of africa in sicily and tunisia along the so called drepano thrust front dtf coeval to collision the generation of the main sardinia thrust mst occurred carrying the sardinia basement rocks over the ck units and deforming the fore arc basin sediments the intermediate pre messinian sedimentary subunit spans from part of serravallian to part of tortonian it is post tectonic with respect to the underlying subunit but it represents a pre rift succession if related to the overlying one it consists of terrigenous deposits prograding from sardinia to the ene into a basin some hundreds of meters deep which was left in the area after collision the youngest pre evaporitic subunit late tortonian early messinian in age displays wedge shaped reflectors in the sardinia basin and forms the lower portion of a syn rift complex including the messinian and part of the pliocene sediments this succession records the onset of extensional tectonics in the area as also testified by the tortonian age of exumation of the basement while in the tyrrhenian basin north of the ocl intra tortonian to intra pliocene rifting was strong but discontinuous and migrating with time to the east in the sw tyrrhenian basin in contrast rifting was less severe but continuous during the same time interval this emphasizes the role played by the ocl a inherited mesozoic discontinuity reactivated as a transfer zone during the neogene these new data allow correlation of the main miocene deformational events observed in the study area to those of the adjacent emerged areas namely the peloritani and maghrebian units in sicily prior to the pliocene quaternary full development of the southern tyrrhenian sea

erosional processes and paleo environmental changes in the western gulf of lions sw france during the messinian salinity crisis abstract current interpretation of the messinian salinity crisis msc involves partial desiccation of the mediterranean sea coupled with the deposition of thick evaporites in the deep basins new sets of seismic reflection profiles in the western part of the gulf of lions confirm the basinward extension of the messinian erosion and enable the mapping of distinctive seismic markers indicating the messinian erosional surface or messinian unconformity the basin margin detrital deposits and the deep evaporite sequence the geometrical relationship between these three elements and their relationship to the paleogeography of the margin during the msc provide new information about the evolution of the study area during the messinian the messinian erosional surface mes commonly correlated with the desiccation phase and the deposition of deep evaporites during the apogee of the event is generally interpreted as a subaerial feature in the gulf of lions it is a complex diachronic polygenic erosional surface observed at the base of the prograding plio quaternary sequence beneath the shelf and slope it extends downslope beneath the deep basin upper evaporites and the salt and possibly correlates conformably with the base of the so called deep lower evaporites the whole morphology of the mes reflects a buried drainage pattern supporting the interpretation of fluvial erosion driven by a substantial drop in sea level our results also suggest that large submarine gravity flows occurred prior to any significant accumulation of salt in the basin and prior to the upper evaporites consequently interbedded clastic deposits may partly account for the parallel reflectors of the lower evaporites since river erosion persisted throughout the msc the salt and upper evaporite units may also contain a large amount of detrital sediments the good quality of the new seismic data clearly reveals fan shaped messinian deposits in the downstream part of the main messinian valleys i e the nile var and spanish rivers the depositional scenarios generally involve a substantial sea level fall coupled with deltaic prodeltaic accumulations a chaotic seismic unit unit d filling messinian lows and extending beneath the salt within the study area is interpreted as a messinian clastic unit we propose a polyphase scenario of detrital fan deposition involving pre syn and post salt deposition in subaqueous subaerial environments in the gulf of lions a late miocene tectonic phase that affected the western shelf also played an important role in controlling a the pattern of the messinian fluvial network b the location of maximum erosion on the shelf and c the location of the detrital fan depocentre downslope

offshore evidence of polyphase erosion in the valencia basin northwestern mediterranean scenario for the messinian salinity crisis the messinian salinity crisis at the end of the miocene strongly affected the physiography of the mediterranean margins and in particular that of the valencia basin and its margins the valencia basin which is an aborted tertiary rift related to the opening of the oceanic provencal basin shows evidence of two major messinian erosion surfaces a basal erosion surface bes and a top erosion surface tes bracketing the messinian evaporite succession the basin s margins show only a single erosion surface here termed the margins erosion surface mes in examining the geometrical relationships of these erosion surfaces with the deep basin facies deposited in the abyssal provencal basin during the messinian salinity crisis we have been able to establish a chronology for the messinian in the valencia basin briefly the basal erosion surface extends the margins erosion surface into the central valencia basin and records an early and important sea level fall at the beginning of the messinian salinity crisis the miocene basin series were incised by canyons while the exposed margins underwent substantial subaerial erosion the basin s detrital products linked to this basal erosion grade laterally into the massive messinian salt layer of the provencal basin the overlying upper evaporites unit appears to be widely transgressive beyond the edge of the messinian salt and onlaps the basal erosion surface in the valencia basin this disposition suggests a progressive sea level rise during the deposition of the upper evaporites possibly due to the rapid accumulation of thousands of metres of shallow water evaporite facies in the provencal basin the top erosion surface at the top of the upper evaporites shows a network of incisions and we suggest that this final erosion was

post messinian evolution of the florence ridge area western cyprus arc part i morphostructural analysis abstract the florence ridge part of the western cyprus arc is a compressional relief that was eroded during the messinian salinity crisis while deposition of salt occurred north antalya basin and south herodotus abyssal plain in order to better assess the impact of salt tectonics in the florence ridge region deformations we conducted a morpho structural analysis of available multibeam and seismic data simed and prismed ii campaigns it is indeed a crucial issue to distinguish crustal and gravity driven structures in the compressional to strike slip belts of the eastern mediterranean along the antalya basin we mainly observed multi directional tectonic rafts typical of gravity gliding above salt on the florence ridge itself the base of salt evolves laterally to a messinian erosional surface that erodes a series of stacked nappes this surface is involved in recent faulting south of the florence ridge a nearly 100 km wide fold belt characterizes the herodotus abyssal plain three different zones parallel to the florence ridge appear within this fold belt those are respectively from north to south zones a b and c zone a is characterized mainly by small wavelength folding and faulting approaching zone b a long extensional graben deforms the seafloor zone b stands 100 to 200 m higher than zones a and c there salt welding seems common in the easternmost zone b deep sub circular bathymetric depressions are associated with extremely thick and fan shaped depocenters probably emplaced in relation with active sub salt thrusts many evidences suggest post messinian uplift in this zone zone c shows medium to high wavelength salt cored folds wavelength of those folds increase approaching the distal nile deep sea fan within zone c a nearly undeformed domain exists approaching the eratosthenes seamount en echelon folds bound this flat domain suggesting lateral salt extrusion at the junction between zone c and the distal nile deep sea fan to conclude numerous evidences argue for a post messinian reactivation of the pre messinian florence ridge accretionary wedge numerous folds uplifted zones the salt as on the nearby mediterranean ridge decouples deep and surface deformations and even allow the development of isolated grabens and associated salt ridges in the heart of the florence compressional zone we propose in this case that local basal slope of salt increase related to basement fault activity triggered gravity gliding and thus extensional deformation despite the regional compressional regime finally this study shows that the eastern nile deep sea fan submitted to extremely vigorous salt tectonics seems to have collided with the florence ridge fold belt and to have generated a salt extrusion zone

analysis of regional slope characteristics on venus and earth regional slope values for earth and venus are calculated for each 3 o x 3 o region of topography and the global characteristics of these magnitudes are examined and compared the effects on terrestrial regional slope due to ocean loading are treated by approximating the component of seafloor depth due to the weight of the overlying water column and removing this component from the ocean topography although regional slopes on venus and earth span the same range 0 00 2 4 o 0 07o the slope frequency distributions for the two planets differ significantly the most abundant regional slope values for the terrestrial cases earth and unloaded earth are 0 0 o and reflect the presence of vast plains associated with the continental interiors and ocean abyssal plain in contrast venus exhibits a peak in slope frequency at approximately 0 09 o perhaps indicating less effective planation processes in the absence of a hydrosphere surfaces with regional slope values of 0 07o 0 24 o are substantially more common on venus than on earth slopes in this range are associated with discrete features in the lowland and upland rolling plains provinces of venus and may be indicative of a geologic process that is not commonly observed on earth only 14 1 of all venus surfaces have regional slopes above 0 24 o compared to 26 1 for earth when mean regional slope is calculated as a function of elevation a distinctive positive correlation is expressed on venus in contrast the terrestrial cases exhibit a complex relationship marked by four modes related to the presence on earth of an active hydrosphere driven weathering regime a distinctive crustal dichotomy and plate tectonics the distinctions in the regional slope characteristics between venus and earth point to a simpler less diversified geology on venus

preservation of pristine titanomagnetite in older ocean floor basalts and its significance for paleointensity studies transmission electron microscopy observations and rock magnetic measurements reveal that alteration of fine and large grained iron titanium oxides can occur at different rates fine grained titanomagnetite occurs as a crystallization product within interstitial glass that originated as an immiscible liquid within a fully differentiated melt in several samples with ages to 32 ma it displays very little or no oxidation z 0 in contrast samples with ages of 10 ma or older are observed to also contain highly oxidized z 0 66 large grained titanomaghemite these large grains having originated by direct crystallization from melt are associated with pore space such pore space can serve as a conduit for fluids that promote alteration whereas fine grains may have been armored against alteration by the glass matrix in which they are embedded apparently alteration of oceanic crust is a heterogeneous process on a microscopic scale the existence of pristine fine grained titanomagnetite in the interstitial glass of older ocean floor basalts that have undergone significant alteration implies that such glassy material is capable of carrying original thermal remanent magnetization and may be suitable for paleointensity determinations

salt tectonics driven by sediment progradation part ii radial spreading of sedimentary lobes prograding above salt experimental models indicate that sedimentary lobes deposited above mobile evaporites deform gravitationally by spreading outward radially radial spreading forms both concentric and radial families of thin skinned grabens that are then pierced diapirically by salt ridges the overburden blocks located between the ridges become subsiding depocenters later continued spreading after depletion of the salt layer forces salt ridges and diapirs to fall forming rapidly subsiding bathymetric lows that channel or trap younger sediments spreading causes large horizontal overburden movements whose distribution and orientation change when the locus of regional deposition shifts

active tectonics of the adriatic region from gps and earthquake slip vectors 1 to investigate the kinematics of the adriatic region we integrate continuous and episodic gps measurements with mw 4 5 earthquake slip vectors selected from the regional centroid moment tensor catalogue coherent motion of gps sites in the po valley in apulia and in the hyblean plateau allows us to estimate geodetically constrained angular velocities for these regions the predictions of the gps inferred angular velocities are compared with the earthquake slip vectors showing that the seismically expressed deformation at the microplate boundaries is consistent with the observed geodetic motion the remarkable consistency between geodetic seismological and geological evidence of active tectonics suggests that active deformation in the central adriatic is controlled by the relative motion between the adria and apulia microplates the microplates angular rotation rates are then compared with the rotation rates calculated with a simple block model supporting the hypotheses 1 that apulia forms a single microplate with the ionian sea and possibly with the hyblean region and 2 that adria and apulia rotate in such a way as to accommodate the eurasia nubia relative motion we suggest that the present day microplate configuration follows a recent fragmentation of the adriatic promontory that during the neogene rigidly transferred the africa motion to the orogenic belts that now surround the adriatic region

european mediterranean regional centroid moment tensor catalog solutions for years 2001 and 2002 abstract we present regional centroid moment tensor rcmt solutions for 168 moderate magnitude earthquakes that occurred in the european mediterranean region during 2001 and 2002 events with moment magnitudes as low as 4 0 were successfully analyzed although this low threshold is only achievable in regions with the best azimuthal coverage and with stations at a few hundred kilometers distance earthquakes with focal depths from 10 to more than 200 km were analyzed comparison with standard harvard cmts when available shows good agreement the solutions shown in this paper represent an addition to the european mediterranean rcmt catalog that we are maintaining the rcmt catalog now spans 6 years from 1997 to 2002 and contains 420 solutions we also outline the main seismic sequences that occurred in the european mediterranean region during 2001 2002

on the post 25 ma geodynamic evolution of the western mediterranean during the neogene and quaternary western mediterranean geodynamics were dominated by the eastward migration of the apenninic arc and associated back arc basins the migration was controlled by retreat of the apenninic slab and was associated with boudinage of the lithosphere in the back arc area palaeo reconstruction of the kinematics of the arc suggests about 775 km of migration from the late oligocene to present along a transect from the gulf of lions to calabria a maximum of 135 km of n s converge occurred between africa and europe during the same time span the western mediterranean was thus mainly shaped by the migration of the slab related to west directed subduction it is hypothesized that minor n s convergence deformed the arc but was not the cause of its formation 1998 elsevier science b v all rights reserved