geology and tectonics of the betic zone se spain abstract the southern margin of the iberian continent comprises a complex geological history which can be traced back into the proterozoic when a gneissic basement was formed a cover of nevado filabride rocks was deposited onto this proterozoic basement during the palaeozoic the permian intrusion of the bedar granite suggests that the palaeozoic sedimentary rocks now exposed in the betic cordilleras have been affected by the hercynian orogeny similar to that of palaeozoic rocks in the adjoining ossa morena zone the hercynian basement was probably covered by alpujarride carbonates in the mesozoic when rifting opened tethys and intruded 140 ma old basic dyke swarms the palaeozoic basement of the betic cordilleras comprises a suture of late cretaceous subduction 80 85 ma b p this can be inferred from hp lt metamorphic facies obducted in coeval thrust slices of nevado filabride rocks the nevado filabride nappes include mesozoic carbonates transformed into marbles macael the suture was probably annnealed after the closure of tethys the mesozoic boundary between africa and europe and the rifting in tethys ceased during the palaeogene when the atlas mountains were formed 36 ma b p subsequently relative movements between africa and europe in the neogene were accommodated by strike slip faults these define the iberian microplate moving eastward by atlantic spreading and possibly subducting under italy neogene deformation of iberia is most intensive in southeastern spain due to emplacement of a mantle diapir under the alboran area this occurred early in the neogene aquitanian and caused nappe spreading involving alpujarride and malaguide rocks the subsequent neogene history has now been studied in great detail and is reviewed here it involves clear examples of calc alkaline volcanism most probably not related to subduction seismic motion along strike slip faults within the iberian microplate and syntectonic deposition in intermontane neogene basins

extension and partitioning in an oblique subduction zone new zealand constraints from three dimensional numerical modeling 1 contraction strike slip and extension displacements along the hikurangi margin northeast of the north island of new zealand coincide with large lateral gradients in material properties we use a finite difference code utilizing elastic and elastic plastic rheologies to build large scale three dimensional numerical models which investigate the influence of material properties on velocity partitioning within oblique subduction zones rheological variation in the oblique models is constrained by seismic velocity and attenuation information available for the hikurangi margin we compare the effect of weakly versus strongly coupled subduction interfaces on the development of extension and the partitioning of velocity components for orthogonal and oblique convergence and include the effect of ponded sediments beneath the raukumara peninsula extension and velocity partitioning occur if the subduction interface is weak but neither develops if the subduction interface is strong the simple mechanical model incorporating rheological variation based on seismic observations produces kinematics that closely match those published from the hikurangi margin these include extension within the taupo volcanic zone uplift over ponded sediments and dextral contraction to the south

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

the physical effects of an intra aggregate structure on soil shrinkage clay and soil containing it have shrinkage curves that are qualitatively different in shape the objective of this work is to qualitatively show with maximum simplicity how a clay shrinkage curve turns into a soil shrinkage curve because of the crack volume the measured shrinkage curve is not the single valued feature of a soil we use a concept of the reference shrinkage curve that is only stipulated by soil shrinkage without cracking single valued and qualitatively similar to an observed shrinkage curve we also use new concepts of an intra aggregate soil structure i a rigid superficial layer of aggregates that loses water during shrinkage and ii lacunar pores micro cracks inside an intra aggregate clay that change in volume during shrinkage then through a series of consecutive steps illustrating each step by a separate graphic presentation we move from a clay shrinkage curve to a soil shrinkage curve with predicted qualitative features that coincide with those experimentally observed in numerous soil shrinkage publications we thereby demonstrate the qualitative physical impact of the intra aggregate structure on soil shrinkage

middle upper triassic carbonate platforms in minorca balearic islands implications for western tethys correlations abstract in order to progress in the knowledge of the middle to upper triassic evolution of the western tethys realm an integrated approach which includes new sedimentological sequence stratigraphic and biostratigraphic data has been accomplished in the carbonate marine successions muschelkalk facies of that age in minorca balearic islands spain the new biostratigraphy which includes six successive ammonoid biozones allowed to assign these carbonate successions to the uppermost anisian lower carnian interval the integration of the new chronostratigraphic framework with the sedimentological analysis allowed to recognize five main successive stages of carbonate platform evolution 1 initial marine transgression and shallow ramp development uppermost anisian 2 carbonate ramp drowning anisian ladinian boundary 3 prevalence of open sea conditions ladinian early carnian 4 abrupt sea level drop intra lower carnian and 5 shallow carbonate ramp and transition to sabkha systems keuper facies furthermore the sequence stratigraphic analysis allowed to divide some of these stages into depositional sequences minorca was located in the westernmost tethys area during the triassic in a key paleogeographic location close to the present day iberia sardinia and the cottian and southern alps the new data have allowed an interregional comparative analysis among these areas with recognition of major suprarregional events and episodes in the framework of the western tethys evolution

the maritime alps arc in the ligurian and tyrrhenian systems abstract after late eocene meso alpine collision between the european and adria plates the maritime alps underwent further deformations linked to the apennine orogenesis and consistent with a stress field developed during anticlockwise rotation the western limit of the rotated sector is east of the argentera massif and to the southwest represents the northwestern margin of the post eocene ligurian sphenochasm the sinistral rotation of the maritime alps initially occurred contemporaneous with the opening of the ligurian basin about 30 19 ma and probably continued during the subsequent opening of the tyrrhenian basin about 10 0 ma the rotating block comprises the northwestern part of the adria indenter and a part of the paleo european plate namely the maritime alps corsica and sardinia if a convenient configuration is assumed for the moho of the adria margin and suitable poles are chosen for subsequent rotations then a simplified model of rigid body can explain the rotation structures in the maritime alps the apennines and po plain subsurface compressional arcs the late foreland directed transport of nappes in the western alps the presence of extensional and dextral transcurrent structures and the general uplift of the lithospheric mantle between the ligurian sea and the ivrea body as to the causes of rotation two alternatives subduction or asthenosphere uplift are discussed chronological and mechanical arguments seem to favour the latter

regional isostatic response to messinian salinity crisis events abstract the salinity crisis of the mediterranean during messinian time was one of the most dramatic episodes of oceanic change of the past 20 or so million years resulting in the deposition of kilometer thick evaporitic sequences a large and rapid drawdown of the mediterranean water level caused erosion and deposition of non marine sediments in a large lago mare basin both the surface loading by the lower messinian evaporites and the removal of the water load resulted in isostatic flexural rebound that significantly affected river canyons and topographic slopes we use flexure models to quantitatively predict possible signatures of these events and verify these expectations at well studied margins the highly irregular shape of the reconstructed basin calls for a three dimensional model near basin margins plate bending effects are most pronounced which is why flexure is particularly important for a relatively narrow basin like the mediterranean we focus on one specific sea level scenario for the messinian salinity crisis where most of the evaporite load was deposited during a sea level highstand followed by a rapid desiccation evaporite loading at current sea level is expected to cause subsidence of the deep basins by hundreds of meters and simultaneous uplift of continental parts of the margins differential uplift may lead to significant slope angle changes and thus gravity flows the relative scarcity of lower evaporite sequences along the margins may be a result of these phenomena normal faulting of lower evaporite and older sediments and rocks is expected on the margins desiccation enhances erosion of the freshly exposed continental shelf and slope subsidence and riverbed sedimentation occurs on the continental margins and significant uplift towards the basin center reverse faulting is predicted at the margins finally regional isostatic uplift following zanclean flooding is predicted to destabilize margin slope deposits and to cause marginal uplift river down cutting and normal faulting

rotational differences between the northern and southern tyrrhenian domains palaeomagnetic constraints from the amantea basin calabria italy we report on a palaeomagnetic study of upper miocene sediments from the amantea basin located on the tyrrhenian coast of calabria the magnetic mineralogy is dominated by greigite and subordinate magnetite in the tortonian messinian clays ten sites and by hemoilmenite and magnetite in the underlying sands and volcanic ashes three sites which have not been dated data from the tortonian messinian clays pass both a reversal and a fold test and define a 19 11 clockwise rotation with respect to the geocentric axial dipole field direction for the whole basin the variable amounts of westward declinations observed in the underlying sands and volcanic ashes can be due to 1 a large counterclock wise rotation episode occurring before the clockwise rotation 2 the effects of a transitional geomagnetic field in these rapidly deposited sediments or 3 the observed complex magnetic mineralogy these new results when compared with previous palacomagnetic studies from other calabrian basins show that the neogene drifting of the calabro peloritan block from the eastern margin of sardinia to the present day position was accompanied by a probably pleistocene 15 20 rigid clockwise rotation recorded in both the tyrrhenian and ionian margins this tectonic regime is shown to be very different from the one observed by previous studies in the northern tyrrhenian domain where large rotations associated with thrust sheet activity in the external apennines were coeval with the onset of an irrotational extensional regime in the tuscan and latium tyrrhenian margins palaeomagnetism thus confirms the significant geodynamical differences between the southern and northern tyrrhenian sea spreadings

paleomagnetism of the istria peninsula yugoslavia 280 core samples were collected from upper jurassic cretaceous and eocene sediments outcropping in the istria peninsula yugoslavia due to the very low intensities of the initial natural remanent magnetizations more than 50 of the collection consisting mainly of rock samples of jurassic and eocene sediments was not suitable for paleomagnetic studies the cretaceous samples yield a mean paleomagnetic pole lat 53 long 275 and 95 4 8 which is significantly different from the african and european paleomagnetic poles of the same age the position of the istria peninsula on the autochthonous adriatic platform allows the result to be interpreted as applicable to all the autochthonous periadriatic region this new paleomagnetic result indicates that the autochthonous adriatic platform rotated counterclockwise over an angle of about 30 with respect to africa in post mesozoic times

arguments for the pre rift uplift and rift propagation in the ligurian provencal basin northwestern mediterranean in the light of pyrenean provencal orogeny the cenozoic provencal orogeny and the subsequent opening of the ligurian provencal basin were caused by a geodynamic mechanism that originated in the cretaceous it is evident from the arguments presented that 1 regional doming preceded rifting of the continental margin and this uplift widened and or migrated during the ensuing opening of the ligurian provencal basin 2 clastic sedimentation on the provencal platform was initiated during the early cenomanian 3 deformation in the provencal block which varies from late cretaceous to miocene reflects a migration of the north south compression from west to east accross the block 4 the languedoc provencal fold belt was initiated during the eocene as a result of tectonic uplift and sinistral displacement of the paleozoic basement toward the north significant geologic features of the region associated with these events include 1 similarities in shape of the languedoc virgation and the provencal thrust front with the shape of geophysical features over the golfe du lion 2 the unusual width of the young stretched continental margin in the golfe du lion 3 the distinctive v shaped form of the ligurian oceanic crust and 4 the concordance in age of the earliest post rift deposits which increasingly young toward the east and magnetic anomalies that parallel the basin axis these events and structures are attributed to the uplift of a paleozoic block situated to the south in the golfe du lion and previously buried under the mesozoic cover the development of this crustal uplift since upper aptian and its northeastwards migration and or gradual widening account for both sedimentary events and tectonic deformation that occurred on the provencal platform until upper eocene and the later stage of rifting and formation of the provencal margin in the ligurian provencal basin the synthesis of marine data as well as relevant terrestrial data indicates that rifting propagated towards the gulf of genoa while the corsica sardinia block rotated to the southeast

onshore to offshore reconstruction of the messinian erosion surface in western sardinia italy implications for the messinian salinity crisis new outcrops in the sinis peninsula sardinia italy allow a detailed description of the messinian erosion surface the correlation between outcrops industrial seismic data and data collected offshore oristano from a recent cruise permits reconstruction of the geometry of this surface from presently emerged interfluves to the deep canyons offshore with onshore an eroded karstic plateau presently cropping out over a 20 km 5 km area well preserved karst structures occur locally and can form several metres high reliefs the southernmost edge of the plateau is limited by a cliff the karstic plateau and the cliff are sealed by transgressive deposits of pliocene age offshore an interfluve zone with a mostly flat and low angle dipping plateau westward dissected by paleovalleys which were identified down to a depth of 2000 m in the oristano gulf messinian paleovalleys were also identified the capo san marco paleocliff was probably located on the edge of a canyon onshore only one major erosion surface was identified located at the top the messinian sequence offshore this surface extends down to the abyssal plain the surface was emplaced above deposits related to the terminal carbonate complex this indicates that the marginal evaporites are older than the major drawdown of the mediterranean sea level the major drawdown is related to the deposition of the deep evaporites

counterclockwise rotation of northeast japan paleomagnetic evidence for regional extent and timing of rotation early to late miocene welded tuffs have been sampled from northeast honshu island and the oshima peninsula of hokkaido island japan for paleomagnetic study characteristic directions with a high unblocking temperature component above 560 c are isolated from 24 sites westerly declinations d 1 91 are identified in welded tuffs older than 17 ma from these areas when combined with previous paleomagnetic data from welded tuffs the early miocene paleomagnetic poles derived from northeast honshu island and the oshima peninsula are statistically identical and indicate that northeast honshu island and the oshima peninsula were subjected to counterclockwise rotation as a single tectonic block these results establish that the rotating block of northeast japan extends north to the oshima peninsula to the latitude 43 n the dimension of this rotating block is of the order of 500 km the paleomagnetic data provide a best curve for the rotation process with the counterclockwise rotation reaching a climax at 15 0 ma and a net amount of rotation of 46 4 the 500 km long northeast japan block was rotated counterclockwise through more than 45 and accompanied a clockwise rotation of the 600 km long southwest japan block at about 15 ma

heat flow in the balearic and tyrrhenian basins western mediterranean we present the results of three detailed heat flow surveys which are used to investigate the variations of heat flow and age of the balearic and tyrrhenian basins in the western mediterranean analysis of 12 measurements within a 10 km radius from 40 01 4 55 e in the balearic abyssal plain shows a mean heat flow of 92 10 mw m 2 after correction for the effects of sedimentation this value agrees well with the predictions of plate cooling and high extension stretching models for crust of the late oligocene age proposed for the basin a similar survey with 18 measurements around 40 16 n 11 19 e in the western tyrrhenian gives a flux of 134 8 mw m 2 while the third survey of 26 measurements in the southern tyrrhenian abyssal plain at 37 17 n 12 58 e yields a slightly higher heat flow of 151 10 mw m 2 these values are within the range predicted by simple plate cooling models for the late miocene ages of the deep tyrrhenian basin thus our observations suggest that although the mode of crustal formation of these deep marginal basins is less well defined than that of the major ocean basins the thermal signature is similar also the trend of increasing heat flow from west to east through the balearic and tyrrhenian basins is in agreement with models of the formation of the western mediterranean behind an eastwardly migrating trench system in all three areas the measured flux shows significant local variability in the two westernmost surveys this can be attributed to the presence of buried high conductivity salt structures but in the third area se tyrrhenian the magnitude of the variations is several times greater than can be attributed to steady state thermal refraction alone instead evidence exists for localized hydrothermal activity linked to the small topographical relief within the survey area

compressional velocity structure and anisotropy in the uppermost mantle beneath italy and surrounding regions travel times of about 39 000 pn arrivals recorded from regional earthquakes by the italian telemetered seismic network and by stations of nearby countries are inverted to image lateral variations of seismic velocity and anisotropy at subcrustal depth in italy and surrounding regions this method allows simultaneous imaging of variations of pn velocity and anisotropy as well as crustal thickness variations the po plain the adriatic sea and the ionian sea have normal to high pn velocities in contrast lower velocities 7 9 8 0 kin s are imaged in italy beneath the western alps the northern apennines and eastern sicily and nearby calabria as well as in northern albania and beneath the pannonian basin low pn velocities beneath the northern apennines correlate with present day extension and may have resulted from thermal anomalies in the uppermost mantle possibly due to delamination processes low velocities are consistent with the high attenuation zone inferred in the uppermost mantle beneath the internal apennine units and the tyrrhenian margin of the peninsula by mele et al 1996 1997 on the contrary low velocities beneath the western alps may be an apparent effect due to the abrupt thickening of the crustal roots pn velocity is anisotropic in the study area with a maximum amplitude of 0 2 km s the largest anisotropic velocity anomalies are observed along the major arc structures of italy i e the northern apennines and the calabrian arc indicating that these features are controlled by uppermost mantle processes the anisotropy anomaly along the calabrian arc extends as far as albania but ends abruptly north of this area suggesting that a lithospheric discontinuity is present along the northern albanian border

structural applications and discussion of a paleomagnetic post paleozoic data base for the central mediterranean abstract a post paleozoic paleomagnetic data base has been compiled for the central mediterranean with the intention of listing directions at the highest possible level of data combination the value of the entries depends on the number and quality of data available the most reliable data are those based on regionally distributed localities and sites where the age is known to a stage and where tectonic correction has been made these represent a whole tectonic unit in a given period of time the lowest quality directions are those based on few samples and isolated in space and time in the tectonic interpretation of the listed data this variation in quality of data has been taken into consideration indications for cenozoic movements having a fundamental influence on the now observable distribution of the clockwise and counter clockwise rotated paleomagnetic directions were treated first and those for older movements afterwards microplate block and nappe movements were considered as possible mechanisms for the rotation of these the last two mechanisms explained satisfactorily the occasional local deviations from a general pattern other differences however such as those which exist between the northern calcareous alps or the tisza unit and the counter clockwise rotated superunit of the central mediterranean which are large and persisted through a longer period of time are best explained by independent movement of the whole unit

structural and tectono stratigraphic review of the sicilian orogen and new insights from analogue modeling abstract the apennines sicilian maghrebian fold and thrust belt originated from the subduction of the alpine tethys and the later collision of drifted continental blocks against the african and apulian paleomargins from north to south the sicilian fold and thrust belt sftb is divided in four main tectono stratigraphic domains 1 the calabro peloritani terrane drifted from the european margin 2 the remnants of the alpine tethys accretionary wedge atw related to the subduction of the tethys 3 the folded and thrusted platform panormide and deep water imerese sicanian series of the offscrapped african margin and 4 the african foreland hyblean unfortunately scarce quality seismic lines and outcrops of key tectono stratigraphic units make the structure and dynamic evolution of the central eastern part of the sftb controversial first this study outlines through a review of the tectono stratigraphic evolution of the central eastern sector of the sicilian orogen the major remaining issues concerning 1 the occurrence of inferred alpine tethys units far from the region where the remnants of the atw outcrop nebrodi mountains both in a forearc position above the peloritani block to the north and in an active foreland context along the present day southern front of the belt and 2 the diverging tectonic styles from stacked large scale tectonic nappes to foreland imbricated thrust systems rooted into a main basal decollement secondly new constraints are given using analogue modeling to test mechanically the hypothesized structural and tectono stratigraphic evolution of the sftb the experiment simulates the orogenic evolution of the sftb at crustal scale from the oligocene tethys subduction to the middle miocene late pliocene continental collision between the european and african paleomargins the tectono stratigraphic synthesis is used to model the first order mechanical stratigraphy of the sedimentary units involved in the sicilian belt as well as the imprint of the african margin structural inheritance the experiments succeed in reproducing the general structure and tectono stratigraphic evolution of the sftb in particular the models support field observations hypothesing a gravity driven origin of the inferred alpine tethys units intercalated within the forearc and foreland syntectonic sedimentation moreover the model testifies of the main tectonic steps that led to the sftb building first a low tapered accretionary wedge was accreted above the alpine tethys oceanic crust from the oligocene to the early miocene the following underthrusting of the stretched african continental margin and its frontal panormide platform shortened and thickened the accretionary wedge this phase provided favorable conditions for significant pulses of reworked alpine tethys units that intercalated within the forearc and foredeep successions during the middle miocene the decollement of the african meso cenozoic cover panormide platform and imerese sicanian deep water basin enhanced a deep seated deformation phase along with duplexing of the panormide platform beneath the alpine tethys wedge leading to its emersion since the late messinian activation of basement faults led to a generalized emersion of the orogenic units through large wavelength fold culminations accompanied by syn tectonic deposition at their southern limbs concurrently the prism front was partly indented to the southeast by the thick and locally already emerged hyblean platform

a two stage rifting in the basins of the corsica sardinian straits abstract a set of seismic and field data from the corsica sardinian straits allowed us to define three well separated oligocene deep basins the castelsardo and porto torres basins forming the northern end of the sardinian graben and the bonifacio basin on the continental shelf of the bonifacio straits a seismostratigraphic investigation of these three basins revealed two major tectonic events a first oligocene to middle aquitanian rifting phase followed by oceanic spreading in the western mediterranean and then a second rifting event between corsica and sardinia in lower burdigalian time the first rifting is noticed in the three basins but the second one only in the porto torres and castelsardo basins

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

paleomagnetic study of sicily consequences for the deformation of italian and african margins over the last 100 million years abstract paleomagnetic analysis of cenozoic sediments from the iblean platform 12 sites 100 samples has provided four new poles these data are combined with those available from volcanic series to yield a new apparent polar wander path for stable sicily since the upper cretaceous this curve when compared to a revised curve for africa using a selection of available data points demonstrates a 15 rotation of sicily with respect to africa during the plio pleistocene this rotation accounts for the extensional tectonic regime that prevails in the pelagian sea and which is evidenced by en relais rifts malta pantelleria linosa associated with alkaline volcanism of pliocene and quaternary age paleomagnetic directions from various areas of the italian peninsula also indicate anticlockwise rotations with diverse amplitudes the chronology of these rotations is consistent with a deformation of the western italian margin during progressive suturation from north to south of the corsican sardinian block since the end of the oligocene

the deep lithosphere in the alps a model inferred from p residuals abstract the tomographic studies of the alps and their surroundings based on the relative p residuals indicated two lithosphere roots attaining depths over 200 km separated by an upwelling of the lithosphere asthenosphere transition beneath the central part of this mountain range the directional dependence of relative p velocities indicates an anisotropic wave propagation in the subcrustal lithosphere beneath the alps and their surroundings the presented model of the deep lithosphere structure suggests several phases of the tectonic development of this region collision of a tip of the adriatic plate with europe in the eastern alps and dextral strike slip movement of the adriatic ending with underthrusting of europe beneath the western alps and counterclockwise rotation the latter contributes to a steep plunge of both plates beneath the eastern alps and to stress accumulation in the friuli region a model with delamination of the rigid upper crust and its rotation resolves some of the inconsistencies between the near surface and deep tectonics and also explains the distribution of seismicity

paleomagnetic and structural evidence for neogene block rotations in the central apennines italy magnetic fabric and paleomagnetic analyses on sedimentary sequences in several structural units in the central apennines ranging from upper cretaceous pelagic carbonates to upper miocene turbidites provide evidence for at least two distinct phases of rotation the first counterclockwise ccw rotation is well recorded in eocene oligocene sediments and does not affect the lower middle miocene sequences the second phase is clearly recorded in lower middle and upper miocene sediments and shows both ccw and clockwise cw rotations in concordance with trends of the different thrust structures we detected three domains characterized by different rotation patterns the westernmost is the southern sabina area an arcuate thrust belt which underwent a cw rotation after the early miocene the second domain is the latium abruzzi carbonate platform where a ccw rotation occurred after the late miocene the third is the marsica area that underwent a cw rotation after the late miocene the magnetic fabric analyses confirm the existence of these different structural provinces and show a strong correlation between the present day strike of the anisotropy of magnetic susceptibility magnetic lineation and the rotations recorded in miocene sediments we attribute present day variations in orientation of the compressional structures in the central apennines to differential rotations about vertical axes due to strike slip faults and out of sequence thrust activity rather than to a change in the stress field orientation we also suggest that this deformation mechanism could be common in other collisional chains around the world

a synchronous alpine and corsica sardinia rotation 1 we report on the paleomagnetism of 34 sites from lower oligocene middle miocene sediments exposed in the tertiary piedmont basin tpb northern italy the tpb is formed by a thick 4000 m and virtually undeformed sedimentary succession unconformably lying upon alpine nappes decapitated by extensional exhumation which in turn are tectonically stacked over the adriatic foreland paleomagnetic directions from 23 mostly oligocene sites were chronologically framed using new biostratigraphic evidence from calcareous nannoplankton our data along with published paleomagnetic results show that the tpb rotated 50 counterclockwise with respect to africa in aquitanian serravallian times the rotation was likely driven by underneath nappe stacking and was synchronous with further bending of the alpine chain both the rotation magnitude and its timing are similar to those documented for the corsica sardinia microplate therefore the formation of the western alpine arc or at least part of its present day curvature occurred during the rollback of the apenninic slab and related back arc spreading of the liguro provencal basin and drift of the corsica sardinia block this suggests a common dynamics driving both the alpine and the apennine slab motions paleomagnetic data also document that the adriatic plate has undergone no paleomagnetic rotation since mid late miocene times anisotropy of magnetic susceptibility data suggests that the tpb an enigmatic basin arising from a controversial tectonic setting formed in an extensional regime characterized by a stretching direction approximately orthogonal to the main trend of the underlying chain

oligo miocene rotation of sardinia kar ages and paleomagnetic data of tertiary volcanics abstract conventional k ar dating was carried out on mineral separates mostly plagioclases from middle tertiary volcanics of sardinia along with paleomagnetic studies the close agreement of dates from the two methods establishes the rotation age of sardinia relative to europe within a rather short time span of 1 5 ma between 20 5 and 19 ma from correlation of our results with the geomagnetic time scale it is suggested that the rotation took place shortly after the magnetic anomaly 6

the valencia trough and the origin of the western mediterranean basins abstract evolutionary models for the valencia trough must be necessarily related to the neogene present geodynamics of the western mediterranean basins all these basins occupy new space created in the wake of the westward translation of the alboran block and the counter clockwise rotation of the corso sardinian block this escape tectonics microplate dispersal model can account for the co existence and progressive migration of compressional and extensional strain fields within the africa europe broad zone of convergence in this escape tectonics model the valencia trough has resulted in a complex evolution which includes 1 latest oligocene early miocene rifting along the catalan valencian margin due to the opening of the gulf of lions 2 almost simultaneous early miocene transpressive thrusting in the balearic margin related to the initiation of displacement of the alboran block and 3 late miocene generalized extension as a consequence of the opening of the south balearic basin

aeromagnetic constraints on the geostructural interpretation of the southern part of the sardinian rift italy abstract aeromagnetic data are interpreted to better understand the relationship between the southern part of the oligo miocene rift and the plio quaternary campidano graben on sardinia particular reference is made to the geostructural location of the campidano graben the aeromagnetic data have been interpreted by applying three different methods to the original survey data spectral analysis analytical signal and werner deconvolution the results of this study give first order estimates of the depth of the magnetic basement and position of major dykes in the study area and on the efficiency of the inversion methods used

a cross section of the lithosphere along the european geotraverse southern segment from the alps to tunisia abstract the european geotraverse southern segment egt s is a 200 300 km wide strip from the alps to tunisia which crosses the youngest tectonic provinces of europe where continued alpine compression is accompanied by recent extension e g in the ligurian sea and sicily channel the geophysical research along the egt s has been nearly continuous both on land and sea from 1982 to 1987 with deep seismic sounding dss experiments and collection of heat flow gravity magnetic seismological and seismotectonic data the new dss and seismic reflection data testify to the asymmetry of the alpine edifice the deepest part of the crust mantle boundary is found beneath the internal and external crystalline massifs where the european moho disappears after a steep flexure in the seismic reflection data the continuation of the moho discontinuity into the southern alpine domain is however evident in the seismic refraction data seismic evidence and heat flow data indicate incipient rifting in the ligurian sea which is underlain by a mantle with an anomalously low pn velocity of only 7 5 km s the palaeozoic crust of the sardinia corsica block exhibits a bowl shape with a rather undifferentiated internal structure average p wave velocity of 6 3 6 4 km s crustal thickness increases from 20 km at its margins to more than 30 km beneath the centre of the islands a thinned crust with thrusted blocks in its upper part characterizes the sardinia channel finally the preliminary dss results from tunisia show an abrupt deepening of the moho from 20 to approximately 35 km in the tell area very low average crustal velocity which requires a velocity inversion within the lower crust and subcrustal reflectors revealing a structured upper mantle

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

carbonate mineral water interactions in sulfide rich mine tailings the chemical composition and mineralogy of coatings on carbonate minerals from mine tailings have been studied using aqueous geochemical methods time of flight laser ionization mass spectrometry tof lims and transmission electron microscopy tem the goal is to study major and trace element partitioning between the aqueous and solid phase and to infer mechanisms that control the concentrations of elements in the pore water of sulfide rich mine tailings pore water samples and carbonate mineral grains were collected from four geochemically distinct zones within the tailings oxidation of sulfide minerals near the surface results in a large range in pore water ph 3 85 to 6 98 and aqueous concentrations of metals and sulfate with increasing depth in the tailings mineral water interactions lead to increasing ph and decreasing concentrations of metals and sulfate calculated mineral saturation indices trends in the abundance of ca fe mg and mn in tof lims profiles through the secondary coatings and electron diffraction patterns obtained from the coatings suggest that precipitation dissolution of jarosite group minerals gypsum goethite akaganeite amorphous fe oxyhydroxides and siderite control the aqueous ca fe na k and so4 concentrations the occurrence of secondary coatings on primary minerals is widespread and reactions with the secondary minerals rather than the primary mineral substrate probably represent the principal controls on trace element distributions in the pore water the data indicate that adsorption surface complexation and co precipitation reactions are important controls on the concentrations of trace elements in the pore water the occurrence of siderite coatings on the surface of ankerite grains suggests that fe bearing dolomite structure carbonate minerals dissolve incongruently this corroborates inferences made by previous workers that solubility differences between calcite and siderite lead to calcite dissolution and siderite precipitation during acid neutralization the accumulation of secondary coatings will diminish the rate of mineral dissolution reactions involving the primary minerals consequently the use of kinetic rate constants obtained from the literature for simulating the dissolution of primary mineral phases such as the carbonates and alumino silicates will likely overestimate the actual rates

aeromagnetic evidence for the rotation of sardinia mediterranean sea comparison with the paleomagnetic measurements abstract the aeromagnetic survey of sardinia western mediterranean delineated a large magnetic anomaly located in the western part of the island the shape of the anomaly is improved and simplified by upward continuation and modelling in terms of three dimensional structure gives a westward remanent magnetization some tests have been carried out to suppress ambiguities on the magnetic dual aspect magnetization distribution shape of sources the optimal declination obtained after a few testings is 30 west which is ascribed to the rotation of sardinia this value confirms the results provided by paleomagnetic investigations and is significant because it characterizes a large and deep rooted structure involved in the rotation of sardinia our results thus illustrate another interesting application of aeromagnetic surveys

integrated chronostratigraphy of an intra arc basin 40ar 39ar datings micropalaeontology and magnetostratigraphy of the early miocene castelsardo basin northern sardinia italy the chronostratigraphy of the lower miocene deposits of northwestern sardinia is refined in the castelsardo basin the combination of new 40ar 39ar isotopic datings 19 micropalaeontological datings calcareous nannofossils planktonic and large benthic foraminifers and 16 palaeomagnetic polarity measurements led to a new chronostratigraphic framework the continental deposits of the first megasequence valledoria and casteldoria members are possibly aquitanian the overlying marine sediments are early burdigalian vaginella depressa molasse the marine transgression can be dated to around 19 7 ma marine conditions ceased 18 83 0 13 ma the age of the index aerial 2 ignimbrite the continental part of the second megasequence lacustre unit is early middle burdigalian between 18 8 and 18 ma the overlying marine part campulandu and sedini members is middle late burdigalian the second marine transgression began in the earliest late burdigalian during the chron c5dr reversal at the time of the eustatic bur 4 event the castelsardo basin went through two main extensional tectonic episodes the first one occurred as the valledoria member was deposited and possibly dates back to the aquitanian the second one occurred as the uppermost part of the vaginella depressa molasse was deposited during the early burdigalian the second extensional episode is related to a rapid rotation of sardinia palaeomagnetic results confirm that corsica and sardinia acted as a single block which suffered a 28 17 ccw rotation after 19 2 ma the castelsardo basin is held to be an aquitanian early burdigalian intra arc rift basin that later evolved in a thermally controlled subsident margin of the ligurian provencal basin during the middle late burdigalian

benthic foraminiferal proxies of environmental changes during the pre messinian salinity crisis of the sinis basin w sardinia mediterranean sea abstract the messinian succession cropping out in a marginal basin of the mediterranean sea sinis basin w sardinia was studied in its benthic foraminiferal content in order to investigate the main palaeoenvironmental changes occurring a shallowing upward depositional trend from an upper bathyal circalittoral environment to a coastal lagoon was recognized during the pre messinian salinity crisis in the lower part of the analyzed succession capo san marco formation upper bathyal circalittoral conditions are suggested by species with a wide depth range such as cibicidoides pseudoungerianus melonis pompilioides oridorsalis umbonatus bolivinids and buliminids in the middle part of this formation the progressively shallowing environment is indicated by the low abundance of planktonics coupled with the upward increase of shallow water epiphytic species lobatula lobatula elphidium crispum e macellum ammonia beccarii hanzawaia boueana the progressive marine restriction led to the development of hypohaline conditions typical of lagoonal environments as suggested by ammonia tepida and oligotypic macrofaunas the succession stops with the deposition of laminated limestones barren in fossils sinis laminated limestone formation a mixed siliciclastic carbonate platform torre del sevo formation characterized by fluvial deposits intercalated in the marine succession developed as suggested by benthic foraminifera ostracods very rare planktonic species and macrofaunas sinis laminated limestone formation and torre del sevo formation constituted part of the terminal carbonate complex strongly eroded by the messinian erosional surface mes at its top the palaeoecological conditions in the sinis basin were intermittently suitable for sustaining full marine biota indicating that this marginal basin was not constantly desiccated during the pre messinian salinity crisis

middle paleozoic paleomagnetism of east kazakhstan post middle devonian rotations in a large scale orocline in the central ural mongol belt abstract in order to test different hypotheses concerning the paleozoic evolution of the ural mongol belt umb and the amalgamation of eurasia we studied middle devonian basalts from two localities 11 sites and lower silurian volcanics redbeds and intra formational conglomerates from three localities 20 sites in the chingiz range of east kazakhstan the devonian rocks prove to be heavily overprinted in the late paleozoic and a high temperature presumably primary southerly and down component is isolated at only four sites from a homoclinal section most silurian redbeds are found to be remagnetized in the late paleozoic in contrast a bipolar near horizontal remanence isolated from silurian volcanics is most probably primary as indicated by positive tilt and conglomerate tests analysis of paleomagnetic data from the chingiz range shows that southward pointing directions in ordovician silurian and devonian rocks are of normal polarity and hence indicate large scale rotations after the middle devonian the chingiz paleomagnetic directions can be compared with paleozoic data from the north tien shan and with the horseshoe shaped distribution of subduction related volcanic complexes in kazakhstan both paleomagnetic and geological data support the idea that today s strongly curved volcanic belts of kazakhstan are an orocline deformed mostly before mid permian time despite the determination of nearly a dozen new paleozoic paleopoles in this study and other recent publications by our team significant temporal and spatial gaps remain in our knowledge of the paleomagnetic directions during the middle and late paleozoic however the paleomagnetic results from the chingiz range and the north tien shan indicate that these areas show generally coherent motions with siberia and baltica respectively

detrital modes and provenance of miocene sandstones and modern sands to the southern apennines thrust top basins italy abstract the cilento group lower middle miocene the monte sacro conglomerate upper miocene the gorgoglione formation upper miocene and the crati submarine fan holocene are four turbidite sequences deposited in northwest southeast trending thrust top basins of the southern apennines italy foreland region the corigliano basin is a part of the modern taranto gulf foredeep basin that developed since the late pleistocene sandstone detrital modes of the miocene turbidite units are quartzofeldspathic petrofacies 1 2a 4 5 8 q62f25l13 quartzolithic petrofacies 2b q60f16l24 and arkosic petrofacies 7 q50f45l5 reflecting a collisional orogenic provenance volcanolithic sandstones petrofacies 3 q23f11l66 suggest an important contribution also from a volcanic source area related to the convergent continental margin volcanism connected with the collisional tectonic regime that affected the western mediterranean e g sardinia volcanic arc individual carbonatoclastic beds hybrid arenite biocalcarenite and mudstone are interbedded with sandstone units of the ilento group they have siliciclastic content of about 35 and are quartzofeldspathic petrofacies 6 q53f23l24 these beds 0 10 65 m thick record impulsive gravitational collapses of the carbonate platform passive margin to the east and southeast the petrologic parameters show a temporal evolution from metasedimentary to granitic gneissic provenance ascribed to different tectonostratigraphic units of the calabrian arc nine miocene petrofacies suggest dynamic evolution of the source terranes from laughian to tortonian time facies dispersal patterns and petrologic parameters of the miocene sandstones suggest a provenance from the northern and western margins of the basins comparison between the holocene crati fan petrofacies 9 q54f24l22 and miocene detrital modes suggests that the sandstones of the cilento group the monte sacro conglomerate and the gorgoglione formation were derived from unroofing of the thrusted basement block transported by torrential type fluvio deltaic systems and then funneled into a major turbidite dispersal system analogous to the modern crati submarine fan of the corigliano thrust top basin

the cenozoic graben system of sardinia italy geodynamic evolution from new seismic and field data abstract a tectono sedimentary scenario for the southern sardinia italy cenozoic graben system is proposed using field observations and the interpretation of onshore and offshore seismic profiles the major structural events are tied to the general geodynamic evolution of the western central mediterranean thus the extensional late oligocene aquitanian event is a consequence of an apenninic westward subduction process associated with a volcanic arc 29 30 to 15 16 my which is particularly well exposed in sardinia deposition of sub aerial clastics was followed by transgression of the rift depression at the beginning of the aquitanian subduction terminated at the opening of the oceanic provencal basin and the rotation of sardinia corsica during burdigalian time 20 21 to 15 16 my the messinian compressional event ne sw oriented documented from microtectonic data strongly affected the oligo miocene basin the superimposed plio quaternary campidano graben which is probably related to the formation of the tyrrhenian basin contains more than 600 m of syntectonic deposits a change in polarity of the master faults bounding the oligo miocene rift created a central horst type twist zone separating two depocenters in the oristano and cagliari regions emplacement of large volcanic bodies and inversion of the basin during the messinian in cagliari area has reduced the areas with potential for hydrocarbon exploration the two remaining prospective zones are the oristano sub basin and the offshore south of cagliari where burial of lower miocene marine organic matter may have been sufficient to generate hydrocarbons potential reservoirs could be pre rift mesozoic or eocene strata but are mainly excellent miocene sands derived from erosion of the granitic basement in tilted blocks

ignimbrite correlation using whole rock geochemistry an example from the sulcis sw sardinia italy ignimbrites are useful chronological markers in the geological record at local and regional scales they also provide information on the dynamics of the eruption that produced them making their study of great importance in terms of volcanic hazard assessment however their study is usually hampered by their lateral variation and discontinuity when stratigraphic and lithologic criteria are not sufficient for correlation purposes the use of multiple complementary correlation tools may be necessary to correctly determine their areal extension volume and facies variations whole rock geochemistry is considered one of the less reliable correlation techniques due to the pyroclastic nature of these deposits and their emplacement dynamics these may introduce vertical and horizontal geochemical heterogeneity in the final deposit in addition the occurrence of zoned ignimbrites due to magma supply of changing composition is common in this work we show that if appropriately used whole rock geochemistry can be a valid and highly useful tool for ignimbrite correlation we provide an example from the study of an ignimbrite sequence containing 18 units sensu lato in the sulcis region sw sardinia italy a protocol has been developed for unit recognition based on successive simple binary diagrams where the whole rock composition of a problem sample can be plotted immobile trace elements have been preferentially used to minimize effects of element mobilization associated with alteration and weathering the diagrams provided here are designed for the sulcis but the methodology followed to develop them may be applied to other study areas

evolution of the sardinia channel western mediterranean new constraints from a diving survey on cornacya seamount off se sardinia abstract sarcya 1 dive explored a previously unknown 12 my old submerged volcano labelled cornacya a well developed fracturation is characterised by the following directions n 170 to n s n 20 to n 40 n 90 to n 120 n 50 to n 70 which corresponds to the fracturation pattern of the sardinian margin the sampled lavas exhibit features of shoshonitic suites of intermediate composition and include amphibole and mica bearing lamprophyric xenoliths which are geochemically similar to ti poor lamproites mica compositions reflect chemical exchanges between the lamprophyre and its shoshonitic host rock suggesting their simultaneous emplacement nd compositions of the cornacya k rich suite indicate that continental crust was largely involved in the genesis of these rocks the spatial association of the lamprophyre with the shoshonitic rocks is geochemically similar to k rich and tio2 poor igneous suites emplaced in post collisional settings among shoshonitic rocks sample sar 1 01 has been dated at 12 6 0 3 my using the 40ar 39ar method with a laser microprobe on single grains the age of the cornacya shoshonitic suite is similar to that of the sisco lamprophyre from corsica which similarly is located on the western margin of the tyrrhenian sea thus the cornacya shoshonitic rocks and their lamprophyric xenolith and the sisco lamprophyre could represent post collisional suites emplaced during the lithospheric extension of the corsica sardinia block just after its rotation and before the tyrrhenian sea opening drilling on the sardinia margin odp leg 107 shows that the upper levels of the present day margin hole 654 suffered tectonic subsidence before the lower part hole 652 the structure of this lower part is interpreted as the result of an eastward migration of the extension during late miocene and early pliocene times data of cornacya volcano are in good agreement with this model and provide good chronological constraints for the beginning of the phenomenon

sedimentation and volcanism linked to multiphase rifting in an oligo miocene intra arc basin anglona sardinia three extensional phases can be recognized in the northern anglona area of the oligo miocene sardinian rift during a fifteen million year period which spanned corsica sardinia continental microplate separation and western mediterranean back arc basin opening in response to this multiphase rifting a complex facies architecture involving clastic carbonate and volcanic rocks developed integrated onshore facies and structural analysis dating and offshore seismic data are here used to reconstruct the tectono stratigraphic history of the anglona area initial late oligocene extension created a half graben geometry with syn rift clastic deposits shed locally from fault bounded highs passing laterally to lacustrine marlstones calc alkaline volcanic activity subsequently predominated as volcanic centres developed along one half graben bounding fault voluminous pyroclastic and epiclastic material was supplied to the adjacent half graben accommodation space and was deposited in marginal to marine conditions second phase mid aquitanian early burdigalian extensional faulting recognized from localized clastic syn rift stratal wedges truncated and subdivided the half graben the syn rift sediments were sealed by a regionally correlated ignimbrite that in turn was offset by late second phase faulting third phase extensional fault movement which reactivated the original fault trend then occurred a perched lake developed in the resultant topography coeval with the progressive marine transgression of lower areas as sea level rose during mid burdigalian times reefal carbonates and grainstones developed on fault block highs whilst calcarenites and marlstones were deposited in hangingwall locations initial extension was coeval with the formation of the sardinian proto rift and the initiation of the western mediterranean basin second phase faulting occurred as the corsica sardinia microplate rotated to its present position during western mediterranean back arc basin spreading final extension can be correlated to a second major extension phase along the oligo miocene sardinian rift following back arc basin opening as extension was transferred towards the fore arc in anglona the main influence of multiphase tectonism was on rift topography providing accommodation space and localized uplifted source areas varying relative sea level mainly controlled the broad types of facies belts that developed contemporaneous calc alkaline volcanism played a major role in the supply of basin filling material and in changing the topography locally

sequential extension as a record of corsica rotation during apennines slab roll back the mediterranean geodynamic system is an exceptional natural laboratory to study the complexities of back arc extension during subduction rollback corsica is a key locality that recorded the alpine subduction collision history followed by 30 ma of the apennines slab rollback responsible for the successive opening from west to east of the liguro provencal basin and the tyrrhenian sea the overall strain pattern of the alpine metamorphic units of alpine corsica is studied through a synthesis of i available geological maps ii geochronological data and iii newly acquired structural data relative to successive events of ductile and brittle extension three main stages of extension are recorded 1 syn metamorphic oligocene extension accommodated by n140 trending ductile shear zones that correspond to the reactivation of a major alpine thrust 2 burdigalian ramp flat extension with n60 70 trending fault zones that controlled the deposition of onshore piggy back basins e g st florent basin and 3 serravalian n s trending fault zones from a geodynamical point of view these successive extensional deformations in alpine corsica can be correlated to the history of the apennines slab rollback the two first stages are related to a southeastward rollback of the appennines slab that successively triggered 1 continental rifting in oligocene leading to the opening of the liguro provencal basin and 2 burdigalian extension with n60 70 trending fault zone oblique to the alpine thrust that after a counterclockwise rotation of the corso sardinian block became unable to accommodate extension finally the third stage that gave ns trending fault zones developed in serravalian at the onset of tyrrhenian rifting related to an eastward rollback of the apennines slab as a response of slab tearing in sicily

stratigraphic simulations of the shelf of the gulf of lions testing subsidence rates and sea level curves during the pliocene and quaternary determining the relative importance of factors interacting to control stratigraphic organization is a key issue in sedimentology the pliocene quaternary chronostratigraphy on the gulf of lions platform is still poorly constrained giving rise to different interpretations of the evolution of its subsidence through time this paper examines the pliocene quaternary sedimentary filling of the gulf of lion s shelf with dionisos a numerical stratigraphic model our results show that a constant subsidence rate accurately reproduces the observed geometries whereas a varying subsidence rate reproduces them only if the acceleration of subsidence is limited at this time scale a third order eustatic curve is also reappraised a higher resolution curve built using d 18 o measurements gives a more realistic restitution of our stratigraphic markers finally the constant subsidence rate and sediment fluxes implied in these modellings are discussed relative to climate and local factors of sedimentation

paleomagnetic implications on the evolution of the tethys belt from the atlantic ocean to the pamirs since the triassic abstract we first re examined the apparent polar wander curves for stable eurasia and africa since the triassic these curves were then combined together with curves of north and south america according to the kinematics of the atlantic ocean and a synthetic polar wander curve was given then most of the paleomagnetic results from the tethys mobile belt from the atlantic to the pamirs were analysed several groups of plates microplates and blocks can be seen first relatively stable regions like maghreb and sicily which have not moved much then we have a group formed by iberia sardinia italy and to a lesser extent corsica and the western and central alps for these blocks movements are anticlockwise rotations chiefly driven by the anticlockwise rotation of africa but they are sometimes stronger to the east a major change takes place the north of the aegean sea and the ionian zone are clockwise rotated and these rotations are recent oligocene miocene for the first part pliocene to the present for the second part a major problem arises in turkey caucasus and iran paleomagnetic results indicate a position far to the south of eurasia and at the same time geological evidence is in favour of a position close to eurasia we discuss these discrepancies

the messinian salinity crisis new seismic evidence in the west sardinian margin and eastern sardo provencal basin west mediterranean sea abstract we processed and interpreted a newly acquired geophysical dataset ws10 project integrated with vintage seismic profiles to study the evolution of the sardinian passive margin of the sardo provencal basin the most prominent features of the area of study are a consequence of the messinian salinity crisis msc which produced a thick salt layer in the deep basin complex halokinetic tectonics deformed the overlying messinian upper unit uu and the pliocene quaternary pq sediments sometimes also bending the sea bottom a thinner autochthonous salt in the uu suggests at least one further low stand during the late msc the messinian erosional surface mes separates the erosional truncation of the pre messinian sedimentary sequence from the overlaying plio pleistocene sequence with a clear angular discordance which almost completely masks possible earlier erosional events the mes is present across the middle and upper slopes of the sardinian margin and can be easily recognized down to the lower slope where it interfingers with the messinian evaporites which gradually thicken basinward we propose a correlation between the main erosional surface of the lower slope and the salt layer recognized in the uu as a consequence of a falling stage during the last part of the msc the seismic profiles now available along the west sardinian margin provide novel and crucial information to correlate the messinian depositional units in the deep basin with those present in the lower continental slope and with the erosional surface of the middle and upper slopes our data and interpretation highlight the main units of the messinian trilogy and further internal sequences that are probable related to cyclic fluctuations during their deposition

40ar 39ar dating and paleomagnetism of the miocene volcanic succession of monte furru western sardinia implications for the rotation history of the corsica sardinia microplate although it is widely acknowledged that the corsica sardinia microplate rotated counterclockwise with respect to europe during oligocene miocene time the precise timing of this event has yet to be determined we have measured the age and degree of rotation of a single tie point in the rotation history of the microplate biotite and sanidine 40ar 39ar age determinations of the 200m thick monte furru volcanic succession indicates that most of the volcanic pile accumulated within less than 200 ky the paleomagnetic pole obtained for the 12 volcanic flow units comprising this succession indicates that by 18 2 ma sardinia remained 13 shy of its final rotation angle these results demonstrate that the movement of the corsica sardinia block and the opening of the liguro provencal basin terminated later than previously estimated based on paleomagnetic and geochronologic studies of sardinian volcanic rocks in agreement with paleomagnetic data from sardinian sediments

paleomagnetic evidence for a post eocene 90 ccw rotation of internal apennine units a linkage with corsica sardinia rotation we report on an extensive paleomagnetic study 36 sites of the tuscan nappe succession from the northern apennines arc aimed to reconstruct the tectonic evolution of the internal sector of this chain we analyzed eocene pelagic foreland ramp deposits scaglia toscana formation and oligocene lower miocene siliciclastic turbidites macigno and falterona formations paleomagnetic results show that the internal sector of the northern apennines underwent large counterclockwise ccw rotations with respect to the adria africa foreland a decrease in the rotation magnitude was observed from the southern to the northern sector of the arc from 91 to 36 this trend is opposite to that observed in the more external units of northern apennines and demonstrates that the oroclinal bending model which has been proposed for the external units of the chain is not appropriate to explain the evolution of the internal sector of the arc on the basis of the observed paleomagnetic pattern we propose a new tectonic model in which the tuscan and falterona cervarola units in the southern area were first rotated ccw along with the corsica sardinia block during its lower miocene rotational drifting and were later involved in the main phases of rotational emplacement and translation toward the outermost sector umbria domain thus yielding the final curved shape of the northern apennines chain data from this study represent the first paleomagnetic evidence of the influence of the corsica sardinia ccw rotation in the apennines orogenic wedge deformation in the general framework of the geodynamic evolution of the central mediterranean subduction system

amount of clockwise rotation of southwest japan fan shape opening of the southwestern part of the japan sea abstract paleomagnetic measurements have been carried out on welded tuffs ranging in age between 58 ma and 112 ma from yamaguchi and go river areas in the central part of southwest japan the new data together with those of younger igneous rocks published previously define the change of paleomagnetic field direction during the late mesozoic cenozoic period for southwest japan the paleomagnetic direction from this area has pointed 56 3 clockwise from the expected field direction estimated from apwp apparent polar wandering path of the whole of eurasia during the period between 100 and 20 ma in comparison with the expected one from the eastern margin of eurasia korea china siberia the cretaceous field direction of southwest japan shows the clockwise deflection by 44 49 these results establish that while the eastern margin of eurasia including southwest japan was rotated more or less with respect to the main part of eurasia during last 100 ma southwest japan was rotated clockwise through more than 40 with respect to the eastern margin of eurasia since 20 ma the large amount of rotation for southwest japan implies that it is rotated by an opening of the southwestern part of the japan sea which widens northeastward fan shape opening the tectonic feature of southwest japan and the japan sea is analogous to that of corso sardinia and the ligurian sea in the mediterranean indicating that the fan shape opening is a specific feature of the rifting of the continental sliver at the continental rim

paleomagnetic evidence for a pleistocene clockwise rotation of the calabro peloritan block southern italy abstract a paleomagnetic study of marine marls of early pliocene age and clays of late pliocene to middle pleistocene age from sites along the ionian coast spartivento basin and catanzaro depression of calabria and from sites along the tyrrhenian coast of both calabria and sicily was carried out to determine the amount and timing of tectonic rotation of the underlying calabro peloritan block the magnetisations of the lower pliocene trubi marls have maximum blocking temperatures indicating the presence of magnetite these lower pliocene sediments as well as the younger upper pliocene lower pleistocene clays of this area reveal consistent clockwise rotations of 10 20 there is evidence for a uniform 15 clockwise rotation of the entire calabro peloritan block during the middle pleistocene this is opposite in sense of rotation to the earlier established 23 counterclockwise rotations for the southern apennines but the timing is the same between 0 7 and 0 2 ma the tectonic rotations occur 1 myr after the major phases of extension in the southeastern part of the tyrrhenian basin but simultaneously with the onset of major uplift of the block

structural signature of tectonic processes in the calabrian arc southern italy evidence from the oceanic derived diamante terranova unit the diamante terranova unit is an oceanic derived element within the thrust and nappe structure of the northern sector of the calabrian arc its metamorphic and structural signature reveals a long history of se dipping subduction and collision related deformation of an oceanic lithospheric section underlying the narrow diamante terranova basin the deformation history of the diamante terranova unit may be related to three main tectonic phases the first one is characterized by a structural association which includes features that developed during a progressive deformation related to the evolution of a deep seated shear zone kinematic indicators characterizing subduction related structures clearly show a top to the northwest sense of overthrust shear the second tectonic phase that can be recognized in the area is characterized by structures that may be related to the onset of shear deformation induced by a postcollisional northeastward motion of the overriding plate the third tectonic phase is recorded by brittle features related to the latest tectonic events affecting the calabrian arc during the opening of the tyrrhenian sea shear sense indicators and available radiometric and stratigraphic information together with plate kinematic data allowed us to infer the time evolution of this sector of the calabrian arc and to assess that the diamante terranova unit cannot be considered as an eoalpine element since its deformation related to subduction collision processes occurred prior to the end of the cretaceous

the valencia trough western mediterranean an overview abstract the valencia trough located between the spanish mainland and the balearic islands corresponds to a late oligocene to recent sedimentary basin that is characterized by a highly attenuated continental crust its northwestern part evolved in response to a late oligocene to early miocene rifting phase that was followed by a period of post rift subsidence and a late miocene pleistocene phase of renewed crustal extension and magmatism its southeastern part is characterized by late oligocene to mid miocene compressional deformation and subsequent extension in the axial parts of the basin the crust has been thinned by a factor of 3 whereby the lower crust is either absent or very thin upper crustal extension appears to be considerably smaller than indicated by the crustal configuration of the basin a major problem in understanding the evolution of the valencia trough is the lack of knowledge about the physical state and structure of the lithosphere before late oligocene extension evolution of the northwestern part of the basin appears to be linked with the development of the oceanic provencal basin middle miocene compressional deformation of the balearic fold belt forming the southeastern margin of the valencia trough appears to have interfered with the tensional evolution of the latter which only resumed after crustal shortening in the balearic domain had given way to extensional tectonics during the late miocene

analysis of nrm directions from the rossello composite implications for tectonic rotations of the caltanissetta basin sicily abstract the paleomagnetic results of the pliocene marine marls from the rossello composite section 30 in the caltanissetta basin of sicily have been analysed to determine the amount and timing of tectonic rotations the analysis shows that there is a consistent inclination error for the nrm component which is removed between 500 and 600 c which may be caused by compaction of the sediment differences in inclination error throughout the composite section are related to differing carbonate content a higher carbonate content implying less compaction and smaller inclination error furthermore consistent differences are found between directions of normal and reversed polarities as well as between directions of the lower and upper part of the composite section these differences are to a large extent related to differences in carbonate content porosity and influence of weathering the caltanissetta basin shows a total clockwise rotation of 34 occurring since the early pliocene the magnetostratigraphy of the rossello composite section shows that from the miocene pliocene boundary 5 2 ma up to the gilbert gauss boundary 3 6 ma there were no tectonic rotations of the caltanissetta basin further we speculate that 10 of this total clockwise rotation occurred during approximately kaena times ca 3 05 ma and that at least 24 of this clockwise rotation is younger than the gauss matuyama boundary 2 6 ma

cenozoic denudation of corsica in response to ligurian and tyrrhenian extension results from apatite fission track thermochronology 1 the island of corsica france occupies a unique position in the western mediterranean since it has recorded both the cenozoic alpine orogenic history of the area as well as subsequent extensional collapse and oceanic basin formation we present 41 new apatite fission track aft ages and 23 measurements of track length distributions from corsica in order to elucidate its cenozoic thermal and morphological evolution aft ages vary from 10 5 0 8 ma to 53 8 4 1 ma and form a clear spatial pattern oldest ages are encountered in the southwest of the island with a broad band of ages between 20 and 30 ma running across the mountainous central area and ages 20 ma confined to the eastern half of the island samples along the western and northwestern coasts record kilometer scale erosional denudation linked to rifting in the ligurian provencal basin whereas samples from close to the extensionally inverted alpine deformation front record a later cooling phase related to tyrrhenian extension the eastward younging pattern of aft ages suggests the migration of a wave of erosional denudation from west to east across the island apparently controlled by the migrating locus of extension our aft data therefore support models of mediterranean extension controlled by slab roll back

structural setting of a transpressive shear zone insights from geological mapping quartz petrofabric and kinematic vorticity analysis in ne sardinia italy