late oligocene miocene syn late orogenic successions in western and central mediterranean chains from the betic cordillera to the southern apennines the identification of syn and late orogenic flysch deposits extending from the betic cordillera to the southern apennines assists in the reconstruction of the tectonic sedimentary evolution of the perimediterranean chains a microplate was located between the european and african plates during the late jurassic early cretaceous bordered northwards by the piemontese ocean and southwards by another north africa flysch basin or maghrebian ocean the piemontese ocean and the northern margin of the microplate were structured from the late cretaceous to the eocene to create an eo alpine chain the southern margin of the microplate was deformed in the aquitanian when the internal areas of the maghrebian ocean were characterized by syn orogenic flysch deposits this episode culminated with metamorphism 25 22 ma and nappe emplacement which destroyed the former palaeogeography and created an orogenic belt alkapeca afterwards a lower burdigalian late orogenic cycle started in the deformed area which as a result of the opening of the algero provencal basin caused the fragmentation of the alkapeca its thrusting on the flysch basin and the collision with the north africa and south iberia margins these latter were folded and thrusted the flysch units pushed over the external domain and also back thrusted langhian late orogenic deposits suture the new tectonic features finally the whole orogen was thrust onto the foredeep during the middle late miocene

modeling of the transport and deposition of tungsten in the scheelite bearing calc silicate gneisses of the montagne noire france scheelite bearing calc silicate gneisses csg oceur in the montagne noire within a series of dominant micaschists detailed petrographical and mineralogical studies reveal three successive stages of metamorphism and hydrothermal alteration 1 stage 1 a regional metamorphism at 550 c and 4 5 kb where no mineralization is formed 2 stage 2a a hydrothermal alteration at 500 to 450 c and 4 to 3 kb which is characterized by an intense sericitization of feldpars and deposition of sn in sn bearing cale silicates and 3 stage 2b a hydrothermal alteration characterized by the crystallization of idocrasegrossular in csg with concomittant precipitation of scheelite tungsten was transported through the micaschist environment and deposited as scheelite only in the csg of stage 2b at relatively low pressures to characterize the mechanism of tungsten transport tungsten speciation at high p t and scheelite solubility in aqueous solations buffered by the csg and by the micaschists assemblages were calculated it was found that h2wo 0 4 hwo 4 and wo 2 4 are the dominant tungsten aqueous species in h2o nacl one molal solutions at 500 c and 2 4 kb calculations also indicate that scheelite deposition is controlled by decreasing pressure and increasing activity of aqueous calcium in this system this is consistent with the petrographical and mineralogical observations the consequences of the presence of volatiles n2 ch4 co2 in the regional fluids were examined by determining the effect of n2 on tungsten speciation and scheelite solubility the addition of n2 up to 10 mol to the mineralizing fluids results in a marked increase in h2wo 0 4 and hwo 4 concentrations relative to wo 2 4 and in a large decrease of scheelite solubility this mechanism favours scheelite precipitation and accounts for the commonly observed association of w and sn deposits with graphitic series generating mixed volatiles fluids

stratigraphic and provenance evolution of the southern apennines foreland basin system during the middle miocene to pliocene irpinia sannio successions italy abstract the paper deals with original stratigraphic petrographic and structural data concerning the evolution of the southern apennines chain italy the main langhian to pliocene deposits cropping out in the northern sector of the southern apennines foreland basin system sannio irpinia area have been studied and correlated in order to document the effects of tectonic changes on the evolution of sandstone detrital modes and stratigraphic architecture the studied sandstone units can be grouped in five key intervals a numidian flysch mostly formed by langhian mature quartzarenitic deposits and conformable serravallian post numidian successions formed by arkosic and calciclastic arenaceous pelitic beds foreland depozones b langhian to tortonian san giorgio fm mostly composed of quartzofeldspatic sandstones foredeep depozone c tortonian to early messinian quartz feldspatic and partly sedimentary carbonatoclastic petrofacies thrust top successions vallone ponticello villanova del battista and san bartolomeo fms d late messinian quartzolithic to quartzofeldspatic sandstones torrente fiumarella anzano molasse and tufo altavilla unit which can be referred to infilled thrust top basins e unconformity bounded pliocene quartzofeldspatic sandstone strata wedge top depozones characterized by synsedimentary tectonic activity detrital modes of the serravallian through middle pliocene sandstones of the southern apennines foreland basin system testify clear provenance relations from the accreted terranes forming the southern apennine thrust belt the studied clastics show almost the same blended quartz feldspatic composition this condition could be related to the tectonic transport over thrust ramp of source rocks as suggested by the tectonic evolutionary model this study dealing with sedimentary provenance analysis and tectonostratigraphic evolution provides an example of the close relations between clastic compositions and foreland basin system development in southern apennines

cloud to ground lightning in hurricane andrew the spatial and temporal distribution of cloud to ground lightning was examined in hurricane andrew of 1992 lightning locations available from the national lightning detection network were superimposed on infrared satellite images to relate lightning activity to hurricane cloud structure a distinct radial variation occurred in time averaged flash density with a weak maximum in the eye wall a region of near zero flash density 40 to 100 km from the center and a steady increase to a large maximum in the outer rainbands 190 km from the center this radial distribution is consistent with the convective structure of mature hurricanes eye wall lightning tended to be episodic occurring almost exclusively prior to and during periods of intensification of the storm during these periods negative flashes occurred several kilometers inward from the highest eye wall cloud tops in the region of the largest radar reflectivity positive eye wall flashes while small in number tended to occur directly under the highest cloud tops the results are suggestive of a normal dipole in sign but outwardly tilted along the sloping eye wall in general hurricane flash characteristics resembled those for a background data set of nonhurricane flashes from the same area the exception occurred for negative flashes in the eye wall which had a much smaller mean peak current than the background 25 3 ka versus 44 9 ka

stratigraphic and geochemical study of the organic rich black shales in the tarcău nappe of the moldavidian domain carpathian chain romania an integrated stratigraphic analysis has been made of the tarc u nappe moldavidian domain eastern romanian carpathians coupled with a geochemical study of organic rich beds two main sequence boundaries early oligocene and near to the oligocene aquitanian boundary respectively divide the sedimentary record into three depositional sequences the sedimentation occurred in the central area of a basin supplied by different and opposite sources the high amount of siliciclastics at the beginning of the miocene marks the activation of the foredeep stage the successions studied are younger than previously thought and they more accurately date the deformation of the different miocene phases affecting the moldavidian basin the intervals with black shales identified are related to two main separate anoxic episodes with an age not older than late rupelian and not before late chattian the most important organic rich beds correspond to the lower menilites bituminous marls and lower dysodilic shales members interval 2 these constitute a good potential source rock for petroleum with homogeneous type ii oil prone organic matter highly lipidic and thermally immature the deposition of black shales has been interpreted as occurring within a deep periodically isolated and tectonically controlled basin

a sequence of pan african and hercynian events recorded in zircons from an orthogneiss from the hercynian belt of western central iberia an ion microprobe u pb study sensitive high resolution ion microprobe u pb dating shows that a biotite orthogneiss from the hercynian belt of western central iberia contains 1000 300 ma zircon older 1000 570 ma ages within this range represent inherited detrital material among which four age components may be recognized 980 ma 830 ma 616 10 2s ma and 582 5 2s ma this inherited zircon commonly forms cores that are surrounded by rims yielding late pan african ages identical to those found in slender prismatic and some stubbier bi pyramidal euhedral crystals this is the predominant type of zircon with an average age of 546 3 2s ma thought to have been formed during the main magmatic crystallization stage of the granitic protolith of the gneiss local deuteric replacements of magmatic zircon yield a virtually identical average age of 547 5 2s ma suggesting rapid magmatic cooling typical of shallow intrusive settings many zircon crystals have very thin low th u rims with an age of 315 ma suggested to represent the gneissification of the granitic rock during the hercynian orogeny the abundance in the gneiss body of al rich restitic material and inherited detrital zircon suggests that the granitic magma was formed by anatectic melting of a metasedimentary source rock complex the age of the youngest inherited detrital zircon constrains the sedimentation age of the youngest parts of the anatectic source rock complex to the late neoproterozoic 582 5 ma and leaves a maximum period of 40 myr for metamorphism and anatexis of the source rock complex and migration and intrusion of the granitic magma among the inherited detrital zircon the 616 10 2s ma and 582 5 2s ma ages are by far the most abundant and might be derived from the west african craton where such ages are common for main stage pan african complexes the older 980 ma and 830 ma inherited zircon ages are absent or rare in the west african craton and a derivation from the amazon craton grenvillian sunsas orogens where such ages are common is an alternative

the numidian sequence between guelma and constantine eastern tell algeria the numidian sequence represents one of the main tectono stratigraphic units involved in the geological evolution of the maghrebian orogen during the upper oligocene lower miocene geo structural aqalysis led to the reconstruction of tectonc stratigraphic units and recognition of two main tectonic phases eocene and lower miocene sedimentological analysis of the studied sections has resulted in the distinction of arenaceous and conglomeratic facies generated by debris flows or high density turbidity currents on a submarine slope present within the pelitic arenaceous and arenaceous pelitic sequences which also contain slumped units in places previous and new micropalaeontological data indicate late oligocene early burdigalian ages for the numidian sequences of the constantine mountains on the basis of petrographic study the numidian rocks can be classified as poorly sorted quartzarenites containing siliciclastic matrix the overall petrographic data indicate that the continental intercalaire hoggar tassili and fezzan and series pharusienne hoggar and eglab are possible supply areas for the numidian quartz

altered carbon cycling and coupled changes in early cretaceous weathering patterns evidence from integrated carbon isotope and sandstone records of the western tethys abstract in this study we investigate if a major perturbation of the early cretaceous carbon cycle was accompanied by altered weathering and erosion rates the large aptian carbon isotope anomaly records the response of the biosphere to widespread volcanic activity and probably resulting changes in atmospheric pco 2 levels elevated pco 2 levels should also result in an accelerated hydrological cycle and increased silicate weathering creating a negative feedback loop removing co 2 from the atmosphere we propose to interpret the widespread occurrence of quartz sandstones in the tethys atlantic seaway as a result of altered weathering and erosion rates in the wake of the aptian carbon cycle excursion we challenge the traditional notion that these are flysch deposits associated with early cretaceous orogenic movements in the western tethys we propose that these sandstones were most likely part of a large conveyor belt system acting along the iberian and european margin of the tethys seaway using chemostratigraphic correlations we show that the activity of this system was only short lived and coeval with changes in coastal ecology and the aptian carbon cycle perturbations we tentatively relate the existence of this system to a transient climate regime characterized by fluctuating pco 2 levels

evaporites and strata bound tungsten mineralization discoidal gypsum crystal cavities occur in quartzites that host varying amounts of strata bound scheelite mineralization near halls creek in western australia the host quartzites have been regionally metamorphosed to greenschist facies and are contained within a middle proterozoic sequence that includes pelites mafic and felsic volcanics and volcaniclastic rocks textural fluid inclusion and oxygen isotope data indicate that scheelite was present in the host quartzites prior to regional metamorphism the presence of crystal cavities after gypsum in the quartzites implies an evaporitic origin for this sequence the continental sabkha playa basins of the mojave desert california are suggested to be possible modern analogs e g searles lake where the tungsten content is up to 70 ppm wo sub 3 in brines and 118 ppm in muds and exceeds the amount of tungsten in all known deposits in the united states metamorphism of a continental evaporitic sequence containing tungsten could produce an assemblage of rocks very similar to those reported from several stratabound tungsten deposits some of these such as at halls creek may be related to original accumulations of tungsten in nonmarine evaporitic environments

depositional systems composition and geochemistry of triassic rifted continental margin redbeds of the internal rif chain morocco the middle to upper triassic redbeds at the base of the ghomaride and internal dorsale calcaire nappes in the rifian sector of the maghrebian chain have been studied for their sedimentological petrographic mineralogical and chemical features redbeds lie unconformably on a variscan low grade metamorphic basement in a 300 m thick upward fining and thinning megasequence successions are composed of predominantly fluvial red sandstones with many intercalations of quartzose conglomerates in the lower part that pass upwards into fine grained micaceous siltstones and massive mudstones with some carbonate and evaporite beds this suite of sediments suggests that palaeoenvironments evolved from mostly arenaceous alluvial systems middle triassic to muddy flood and coastal plain deposits the successions are characterized by local carbonate and evaporite episodes in the late triassic the growth of carbonate platforms is related to the increasing subsidence norian rhaetian during the break up of pangea and the earliest stages of the western tethys opening carbonate platforms became widespread in the sinemurian sandstones are quartzose to quartzolithic in composition testifying a recycled orogenic provenance from low grade palaeozoic metasedimentary rocks palaeoweathering indices chemical index of alteration chemical index of weathering and plagioclase index of alteration suggest both a k enrichment during the burial history and a source area that experienced intense weathering and recycling processes these processes were favoured by seasonal climatic alternations characterized by hot episodically humid conditions with a prolonged dry season these climatic alternations produced illitization of silicate minerals iron oxidation and quartz rich red sediments in alluvial systems the estimated burial temperature for the continental redbeds is in the range of 100 to 160 c with lithostatic tectonic loading of ca 4 to 6 km these redbeds can be considered as regional petrofacies that mark the onset of the continental rift valley stage in the western pangea middle triassic before the opening of the western part of tethys in the middle jurassic the studied redbeds and the coeval redbeds of many alpine successions betic tellian and apenninic orogens show a quite similar history they identify a mesomediterranean continental block originating from the break up of pangea which then played an important role in the post triassic evolution of the western mediterranean region

the long term denudation rate in the southern apennines chain italy a gis aided estimation of the rock volumes eroded since middle pleistocene time abstract the long term denudation rate has been evaluated within an actively deforming area the southern apennines chain using both geomorphological and gis aided analysis of a 2738 km 2 representative sample area the rock volume contained between a reconstructed palaeotopography and the present topography of the study area has been calculated palaeotopography has been reconstructed on the basis of the relics of an irregular surface whose tentative age is 0 8 0 6 ma and also includes remnants of a more ancient more suspended and badly preserved palaeosurface to represent the modern topography a certified dtm of italy with grid 230 230 m 2 was adopted the calculated rock volume eroded since the beginning of the dissection of the palaeosurface is 478 km 3 which implies an average erosional downwearing of 175 m however downwearing is not uniformly distributed over the area as it is concentrated along valleys in particular the same major valley trunks that already existed at the beginning of the middle pleistocene show downcutting amounting to 400 m and more while the amount of erosion on the divide areas is of the order of a few tens of metres the resulting mean denudation rate falls between 0 22 and 0 30 mm a

from jurassic extension to miocene shortening an example of polyphasic deformation in the external dorsale calcaire unit chefchaouen morocco abstract liassic rocks of the external dorsale calcaire succession cropping out in the northern rif close to chefchaouen city host pre orogenic structures such as normal faults veins and fractures resulting from extension related to the jurassic rifting of the neotethys domain the successive inclusion of these rocks in the orogenic wedge which mainly occurred in the miocene time deformed the most of pre orogenic structures in a passive manner without an overall reverse reactivation the orogenic deformation includes two main stages the first tectonic pulse which occurred during the burdigalian langhian interval was characterized by a ne sw shortening in the current coordinates and recorded by folds thrust and back thrust faults during this stage the carbonates of the external dorsale calcaire tectonically covered the predorsalian succession producing in the thrust front a sw verging regional fold the second orogenic deformation consisting of a nw se shortening was expressed by thrust faults and related folds both verging to nw and se which probably occurred in the late miocene pliocene time

reply to comment on european provenance of the numidian flysch in northern tunisia dorrik stow christine fildes sami riahi mohamed soussi urval patel j andy milton and stuart marsh institute of petroleum engineering heriot watt university edinburgh eh14 4as uk school of environment university of auckland private bag 92012 auckland new zealand geology department faculty of science university of tunis tunis tunisia core laboratories redhill surrey rh1 2lw uk national oceanography centre southampton so14 3zh uk anadarko algeria company llc 1 harefield road uxbridge ub8 1yh uk

geodynamic implications derived from numidian like distal turbidites deposited along the internal external domain boundary of the betic cordillera s spain this research was supported by urbino university carlo bo grant responsible f guerrera spanish cicyt research projects cgl2009 09249 cgl2011 30153 co2 02 and cgl2012 32169 portuguese fct research project ptdc cli 72585 2006 research groups and projects of the generalitat valenciana from alicante university ctma iga and research group 146 of the junta de andalucia the first author is also grateful to the portuguese fct ciencia 2008 programme contract c2008 ist cvrm 1

paleocene lower eocene carbonate platforms of westernmost tethys abstract the paleocene lower eocene succession is well exposed in sierra espuna mula basin betic cordillera s spain and carbonate platforms are well represented as part of this succession the study of the paleoenvironmental evolution of these platforms has allowed to cover an important gap in the knowledge in the westernmost tethys thirteen microfacies mf1 to mf13 were recognized based mainly on the fossil assemblage principally larger benthic foraminifera texture and fabric of the microfacies the fossiliferous assemblage of the entire succession shows a mixture of photozoan and heterotrophic biogenic elements typical of an inner to outer ramp environment of a warm temperate biogeographic province fragments of hermatypic corals have also been detected in the lower part of the succession paleocene allowing thinking in propitious conditions in this period the succession evolves upwards lower eocene to low energy shallow marine protected environments lagoon in inner ramp settings in addition abundant porcelaneous larger benthic foraminifera such as alveolinids and soritids are indicative of euphotic shallow marine conditions in moderately oligotrophic upper subtidal environments in the upper part of the succession hermatypic corals as displaced fragments and in situ isolated coral phaceloid colonies also appear together with other biogenic components indicating warm shallow and euphotic marine conditions coral maerl environment lenticular larger benthic foraminifera characterizing marine mesophotic and oligotrophic habitats can be found in the upper part of the middle ramp and flattened larger benthic foraminifera forms indicating lowermost mesophotic conditions in a distal middle ramp the obtained results have been compared with other similar tethyan sectors obtaining a broader view the biogenic marine association is characterized by the absence of the lockhartia community of the tethyan domain together with the dominance of alveolinids nummulitids and orthophragminids during most of the paleocene northern mediterranean tethys platforms were located in the middle paleolatitudes and characterized by coral reef and coralgal biofacies the studied platforms located at a latitude close to 25 n show in a ramp like context underdeveloped in situ coral constructions probably of patch reef type in the early eocene the expansion and abundance of the larger benthic foraminifera and the practical disappearance of coral took place in the sedimentary platforms through the entire tethys however in the study area small reef coral build ups have also been observed in the lower cuisian beds indicating that in westernmost tethys coral construction continued at these latitudes

geodynamic evolution of the lithosphere and upper mantle beneath the alboran region of the western mediterranean constraints from travel time tomography an edited version of this paper was published by the american geophysical union copyright 2000 agu see also http www agu org pubs crossref 2000 2000jb900024 shtml http atlas geo cornell edu morocco publications calvert2000 htm

a revised subduction inception model to explain the late cretaceous double vergent orogen in the precollisional western tethys evidence from the northern apennines the meso cenozoic alpine belts of the mediterranean area are characterized by complex architectures result of a complex subduction and collision evolution that preserve also a legacy of the rifting related configuration of the continental margins the northern apennines is a segment of these belts originated during closure of the ligure piemontese ocean and collision between the europe and adria plates the different configuration of the adria and europe margins inherited from asymmetric rifting is recorded in the ligurian units that preserve incorporation into the subduction factory of fragments of the oceanic domain internal ligurian units and portions of the ocean continent transition zone octz toward adria external ligurian units we provide here unpublished data on the stratigraphy and sedimentology of these units together with a review of what is already established in literature both datasets combined testify that at 80 m a an accretionary prism was growing between the deposition basins of the two groups of units and fed both basins with clasts from the ocean realm the continental crust and the subcontinental mantle we propose that closure of the ligure piemontese ocean occurred through subduction that nucleated at the transition from the oceanic plate and the thinned adria margin and developed a double vergent prism by accreting oceanic material and continental extensional allochthons from the octz we believe the revised site of subduction initiation and the pre collisional architecture inherited from the rifting and spreading phases allow reconciling most of the discrepancies between the various interpretation proposed in literature for the pre collisional evolution of the apennines

polyphase out of sequence thrusting and occurrence of marble detritus within the wedge top basin deposits in the mt massico southern apennines insights into the late miocene tectonic evolution of the central mediterranean we present a geological survey of the southwestern sector of the mt massico southern apennines which allowed us to reconstruct the stratigraphy and tectonic architecture of this area the mt massico is a key area to study the out of sequence thrusting stage that affected the southern apennine chain since the late miocene which despite the wide occurrence of these structures in the whole chain is a tectonic process up to now poorly investigated this area deserves to be analyzed also for the occurrence of marble detritus within a wedge top basin deposit representing the only place in the southern apennines where such a kind of metamorphic rocks occurs historically this area is known for the extraction of an ornamental stone named mondragone marble the marble is hosted as olistoliths and clasts within the deposits of the caiazzo fm unconformably covering a jurassic middle miocene succession mostly made of shallow water to deep basin carbonates the wedge top basin deposit mainly consists of a chaotic assemblage of conglomerates olistostromes and olistoliths of meso cenozoic limestones deep basin rocks and marbles embedded in a quartzose matrix the structural setting results from a polyphase deformation related to the superposition of two thrust systems the first thrust system includes a duplex verging to east with the cenozoic carbonates thrusted onto the caiazzo fm and the roof thrust cut by several breaching thrusts the late thrust system encompasses ramp dominated faults verging to the north folds minor thrusts and s c structures are associated with the major compressional structures to date the caiazzo fm and put a temporal constraint to the thrust fault activity we performed a nannoplankton content analysis that furnished for the base of this deposit an age not older than the upper tortonian these out of sequence thrusts hence have acted since the late miocene similar structures are widespread in the southern apennines and are interpreted as the surficial expression of envelopment thrusts formed at deeper structural levels with respect to the thrust front we envisage that the marble and plutonic supply was provided by the mesomediterranean continental crust in the late tortonian when this microcontinent was passing close to the apennine platform domain during its orogenic migration toward se

petrology and geochemistry of cretaceous sedimentary rocks of the monte soro unit sicily italy constraints on weathering diagenesis and provenance abstract the mineralogy and chemical compositions of shale and sandstone alternations of cretaceous age of the monte soro unit sicily have been determined the clay minerals in the shales are mostly illite and i rich mixed layer i s reflected by enrichment in al2o3 k2o and chemically similar elements the sandstones are subarkose to quartz arenite the shales and sandstones have upper crustal rare earth element patterns and except for k2o they are depleted in alkaline and alkaline earth elements as a result of intense weathering the sandstone and shale mineralogy suggests a diagenetic history in which the sediments were subjected to temperatures in excess of 100 c during which interaction between some minerals in the shales and sandstones took place thus diagenetic quartz cementation and feldspar alteration in the sandstones and smectite illitization in the shales occurred together with the shales being a sink for potassium and the sandstones a sink for silicon negative europium anomalies bet

structural and petrological analyses of the frido unit southern italy new insights into the early tectonic evolution of the southern apennines calabrian arc system abstract this study provides new data on the deformation and metamorphic evolution of the jurassic to upper oligocene frido unit an ocean continent transition oct unit belonging to the ligurian accretionary complex lac by means of the integration of structural analysis petrological investigations and a revision of the stratigraphical setting the frido unit representing the main metamorphic component of the lower middle miocene lac in southern italy is characterized by a multistage tectonic evolution including i two progressive deformation phases involving the development under relatively high pressure metamorphic conditions of an early cleavage associated with isoclinal folds within the framework of a dominant se ward tectonic transport ii a third deformation stage involving the growth of lower pressure na amphibole along extensional shear surfaces therefore probably marking the onset of tectonic exhumation and iii two very low temperature deformation phases characterized by the development of kink folds and associated thrusts probably related to the late tectonic emplacement of the accretionary wedge onto the outer sectors of the apennine domain with a prevailing tectonic transport first toward the ne and then toward the nw in order to clarify the metamorphic evolution of the frido unit petrologic analyses were focused on its metasedimentary pelitic succession here mineral parageneses including carpholite well documented for the first time in this study and potassic white mica yielded peak pressure of 1 2 1 4 gpa and temperature around 350 c thus indicating a high pressure very low temperature metamorphism and a p t t path characterized by a rapid exhumation without any greenschist facies overprint in comparison with similar units cropping out in northern calabria tuscany and corsica the frido unit experienced one of the coldest burial exhumation histories

tectono sedimentary evolution of the numidian formation and lateral facies southern branch of the western tethys constraints for central western mediterranean geodynamics this research was supported by urbino university grant awarded to f guerrera cgl2009 09249 and cgl2011 30153 co2 02 research projects spanish ministry of education and science research groups and projects of the generalitat valenciana from alicante university ctma iga and rnm 208 rnm 3715 of the junta de andalucia

a two stage exhumation of the variscan crust u pb la icp ms and rb sr ages from greater kabylia maghrebides the significance and role of major shear zones are paramount to understanding continental deformation and the exhumation of deep crustal levels la icpms u pb dating of monazites combined with rb sr analyses of biotites from an anatectic metapelite from greater kabylia algeria highlights the history of shear zone development and the subsequent exhumation of deep crustal levels in the internal zones of the maghrebides monazites give an age of 275 4 4 1 ma 2r dating the thermal peak coeval with anatexis this age is identical to those recorded in other crystalline terranes from south easternmost europe i e south alpine and austro alpine domains that suffered crustal thinning during the continental rifting predating the tethys opening rb sr analyses of biotites yield a cooling age of 23 7 1 1 ma related to the exhumation of the buried variscan crust during the miocene as an extrusive slice roughly coeval with the emplacement of nappes and shortly followed by lithospheric extension leading to the opening of the alboran sea

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

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

deformation partitioning during transpressional emplacement of a mantle extrusion wedge the ronda peridotites western betic cordillera spain abstract composite tectonic emplacement of the world9s largest outcropping body of subcontinental mantle rocks the ronda peridotites occurred during early miocene continental subduction and as a result of oblique plate convergence partitioning of transpressional deformation between coeval orogen parallel wrenching and orogen perpendicular pure thrusting components is recorded by shear zone kinematics and dynamothermal metamorphism in the footwall to the ultramafic rocks left lateral shear characterizing the deeper high pressure eclogitic portions of the continental subduction system propagated through the mantle into the overlying continental crust of the overriding plate whereas top to the foreland frontal thrusting dominated at the leading edge of the hot peridotite body top to the hinterland shear along the upper contact of the peridotites is consistent with the kinematics expected for an extrusion wedge consisting of subcontinental mantle rocks on the other hand coeval strike parallel extension and thinning of the crustal rocks overlying the peridotites confirms that similarly to other alpine mediterranean examples partitioned transpression resulted in the development of a complex deformation pattern with kinematically linked shear zones aiding exhumation the proposed model provides a new coherent scenario for syn convergence peridotite emplacement and exhumation in the western betic cordillera

why do oceanic negative cloud to ground lightning exhibit larger peak current values this study examines the temporal monthly and spatial climatology 2004 2010 of the first return stroke of the cloud to ground cg lightning flash peak current ip across various land water boundaries over the contiguous united states four regions are examined the gulf of mexico region 1 the florida peninsula region 2 lake michigan region 3 and part of the u s mid atlantic region 4 the crosss across the coastlines of regions 1 2 and 4 show a gradual oceanward increase in the mean negative polarity cg peak current values ip this transition along the respective land ocean boundaries is not sharp but gradual in direct contrast with ocean there is no consistent behavior in ip values as we move from land out across the fresh water of lake michigan region 3 meanwhile the positive cg flash peak current ip values do not exhibit a consistent variation across any coastal boundary for region 1 the ip values increase as we move toward the coast southwards especially during the wet season june october this finding is in direct contrast with studies that documented winter as the season of maximum ip values the zonal and seasonal variations of ip values across region 4 are not quite as pronounced but the oceanic ip values are still larger than over the adjoining landmass we explore in turn which up to date hypotheses pertinent to the oceanic ip enhancement are supported or refuted by our findings it is concluded that the oceanic ip enhancement is not an artifact related to cg detection or ip retrieval methods nor is it likely related to the cloud top heights or cg activity the study cannot refute the role of electrical conductivity and its contribution to cg leader attachment processes however given the observed blurred transition of the ip values across the coastlines this paper suggests that likely the main physical mechanism is acting on the thundercloud potential the recently suggested role of sodium chloride nacl but also the role of ice crystal size implicated herein as possible modulators of the thundercloud potential exhibit distinct pros and cons their candidacy is supported by their strong physical links to the electrostatic charging and thundercloud electric potential buildup but also by the exhibited blurred ip transition across the coastlines in contrast the suggested mechanisms cannot individually explain the observed ip enhancement in terms of season nacl concentrations and absence of similar behavior in the respective ip values

geotechnical and landslide aspects in weathered granitoid rock masses serre massif southern calabria italy abstract the weathering processes produce important chemical and physical transformations in rock masses producing a decay of their strength and then stability in this study different methodologies were employed to define the physical mechanical properties and the minero petrographical changes at each grade of weathering useful to determine a geological model of the weathered granitoids involved in mass movements the paper focuses on a multidisciplinary research on the weathering profiles of the paleozoic granitoid rocks surrounding the village of fabrizia located in the serre massif southern calabria italy fabrizia lies on an old erosion surface composed of basement rocks made up of weathered granitoids belonging to the serre massif granitoid complex and overlain by thin eluvial colluvial deposits the tectonic uplift of the area combined with mediterranean climatic conditions both active at least since the quaternary are the main causes of the deep weathering of the plutonic rocks the weathered profiles of the granitoid complex have been studied through field observations borehole explorations with geotechnical tests and seismic surveys coupled to minero petrographical analysis and laboratory tests weathered profiles are mainly composed by rock masses varying from completely weathered and residual soil classes v vi to moderately weathered rocks class iii characterized by a progressive increase of geotechnical properties e g seismic wave velocity rock quality designation internal friction angle uniaxial compressive strength with a decrease of weathering the weathered rocks display a wide variety of mass movement landslide types are rockfalls for the fresher rocks class iii translational slides occur between different weathering degrees classes iv and v and rotational slides dominate at the top of the slopes and generally involve the weathering grades from class iv to classes v vi the shallow horizons are composed of thin eluvial colluvial deposits and more weathered granitoids classes v vi that may generate dangerous debris flows or debris avalanches during intense and prolonged rainfall the landslide surface is usually at a depth lower than 2 m in the debris flow type while deeper landslides depth 2 m are rotational and translational types with sliding surfaces occurring mainly in the transition between the classes iv and v the field survey coupled to geotechnical geophysical and minero petrographical data allowed the recognition of the different weathered horizons and relative geotechnical properties useful to the reconstruction of the reliable geological model the model represents an important support for the study of the landslide processes and for a sustainable management of the territory the used approach provided results to set a general reference framework for establishing more precise correlations between mass movement phenomena and weathering processes

from rifting to passive margin the examples of the red sea central atlantic and alpine tethys abstract evolution of the red sea gulf of suez and the central atlantic rift systems shows that an initial transtensive rifting phase affecting a broad area around the future zone of crustal separation was followed by a pre oceanic rifting phase during which extensional strain was concentrated on the axial rift zone this caused lateral graben systems to become inactive and they evolved into rift rim basins the transtensive phase of diffuse crustal extension is recognized in many intra continental rifts if controlling stress systems relax these rifts abort and develop into palaeorifts if controlling stress systems persist transtensive rift systems can enter the pre oceanic rifting stage during which the rift zone narrows and becomes asymmetric as a consequence of simple shear deformation at shallow crustal levels and pure shear deformation at lower crustal and mantle lithospheric levels preceding crustal separation extensional denudation of the lithospheric mantle is possible progressive lithospheric attenuation entails updoming of the asthenosphere and thermal doming of the rift shoulders their uplift provides a major clastic source for the rift basins and the lateral rift rim basins their stratigraphic record provides a sensitive tool for dating the rift shoulder uplift asymmetric rifting leads to the formation of asymmetric continental margins corresponding in a simple shear model to an upper plate and a conjugate lower plate margin as seen in the central atlantic passive margins of the united states and morocco this rifting model can be successfully applied to the analysis of the alpine tethys palaeo margins such as rif and the western alps

correlated observations of three triggered lightning flashes a cooperative analysis of three triggered lightning flashes initiated during the thunderstorm research international program trip 81 at langmuir laboratory new mexico has resulted in the determination of three dimensional return stroke propagation speeds and peak currents for 56 subsequent strokes we find a nonlinear relationship between the return stroke propagation speed and the stroke peak current that is qualitatively similar to that proposed by both lundholm and wagner a nonlinear correlation is also found between the return stroke propagation speed and the dart leader propagation speed for 32 strokes linear correlation coefficients are evaluated for the following quantities dart leader propagation speed and ensuing return stroke peak current 32 strokes r 0 84 stroke peak current and interstroke interval 69 strokes r 0 57 return stroke propagation speed and interstroke interval 56 strokes r 0 49 dart leader propagation speed and interstroke interval 32 strokes r 0 43 the weak positive correlation found between the dart leader propagation speed and the interstroke interval contradicts previous corresponding natural lightning observations the mean three dimensional return stroke propagation speed for 56 strokes is 12 107 m s with a range of 6 7 107 m s to 17 107 m s the mean three dimensional propagation speed found for 32 dart leaders is 20 106 m s with a range of 9 5 106 m s to 43 106 m s the mean dart length measured is 50 m with a range of 15 90 m in two of the three flashes the downward propagating dart leaders appear to meet upward propagating streamers at heights of approximately 20 and 30 m respectively

peak current variations of lightning return strokes as a function of latitude latitudinal variations in lightning flash characteristics have been hypothesized1 2 but have not been found to exist3 4 this may be because lightning characteristics are constant over the earth or because the observations have been made over too small an area of the globe to investigate the question of latitudinal variation i have used a network of thirty six gated wideband magnetic direction finders covering the eastern united states to measure the characteristics of cloud to ground lightning flashes these characteristics include the flash location the flash polarity the number of strokes in the flash and the peak magnetic radiation field in the first return stroke of the flash from the peak radiation field i estimate the peak current5 more than five million lightning ground flashes were recorded by the network in 1988 an examination of the mean peak current in the first return stroke shows that the peak current varies by almost a factor of two from 25k a in new england to 40 45 ka in northern florida apparently this is the first report of an important lightning parameter the return stroke current varying over a large area of the globe it seems that the generation of lightning strokes and their characteristics may be a sensitive function of latitude and hence of temperature the results presented here indicate that even higher peak currents will be observed if this research is extended into the equatorial regions

european provenance of the numidian flysch in northern tunisia terra nova 00 1 9 2010 abstract the ultimate source of the deepwater numidian flysch sediments has long been a matter of controversy did the sediments of this late cenozoic orogenic belt in the western mediterranean derive from a european or african source or from a combination of the two new data presented here strongly favour a european provenance zircon ages of 514 19 ma from tunisia and 550 28 ma from sicily can only have derived from rocks of european affinity these zircons have been separated from quartz rich sandstones with a distinctive highly mature heavy mineral assemblage that is different from those of north african autochthonous formations the mature petrography and dominance of euhedral prismatic zircon grains indicate a medium to high grade metamorphic source most palaeocurrent data are indicative of flow from the n and nw the original european provenance is most likely now represented by predominantly metamorphic rocks of the kabylie belt in northern algeria as a result of microplate movement and thrust emplacement

provenance of mesozoic to cenozoic circum mediterranean sandstones in relation to tectonic setting abstract the composition and stratigraphic relations of clastic strata in diverse sedimentary basins of the circum mediterranean region reflect a complete record of provenance relations since break up of pangea neo tethyan taphrogenesis and subsequent plate convergence between the two major plates of europe and africa and other related microplates of iberia adria mesomediterranean and toward to the eastern mediterranean the anatolian microplate since plate reorganization after the breakup of pangea at the end of paleozoic earliest mesozoic clastic wedges filled sedimentary basins within geodynamic settings evolving from intracontinental rifts rifted continental margins protoceanic basins arc trench basin systems remnant ocean basins foreland basin systems and intramontane and back arc basins within the circum mediterranean region the changing nature of clastic particles in these clastic wedges reflect the provenance relations from different source rocks within the spatial and temporal evolving geo puzzle terranes including relations between ophiolite bearing uplifted continental crust both shallow to deep crust terranes volcanic and sedimentary particularly carbonate strata source rocks mixed siliciclastic and carbonate shallow to deep marine clastic wedges are diffuse in many filled basin systems along the mediterranean as such as occurrence of volcaniclastic layers interbedded with siliciclastic wedges the variable mosaic of source terranes within the mediterranean region offered the possibility to investigate provenance relations with a new plane of precision and sophistication discriminating grain particles in clastic wedges using spatial extrabasinal versus intrabasinal and temporal coeval versus noncoeval distinction of detrital signals the spatial temporal approach in deciphering particles in clastic rocks has been widely used to detail the basinal dispersal pathways in different geotectonic settings wherever mixed silicate and carbonate terranes act as the major source rocks from rifted continental margins to collisional orogens

tectonic framework and extensional pattern of the malaguide complex from sierra espuna internal betic zone during jurassic cretaceous implications for the westernmost tethys geodynamic evolution mapping lithostratigraphic biostratigraphic and structural detailed analyses in sierra espuna area internal betic zone se spain have allowed us to reconstruct the jurassic cretaceous evolution of the westernmost mesomediterranean microplate palaeomargin and by correlation with other sectors northern rift central and western internal betic zone to propose a geodynamic evolution for the westernmost tethys extension began from late toarcian when listric normal faults activated these faults are arranged in three categories large scale faults separating hectometric cortical blocks main faults dividing the former blocks into some kilometre length blocks and secondary faults affecting the kilometric blocks this fault ensemble actually outcropping in the sierra espuna area broke the palaeomargin allowing the westerly tethyan oceanic aperture with an extension at about 17 2 extension was not homogeneous in time being the late toarcian to the dogger malm boundary the period when blocks underwent the greatest movement rifting phase leading to the drowning of the area 8 2 extension during the malm drifting phase extension followed 5 7 while during the cretaceous a change to pelagic facies is recorded with an extension of about 3 3 post drift stage this evolution in the westernmost tethys seems to be related to areas out of the limit of significant crustal extension in the hanging wall block of the main cortical low angle fault of the rifting

main differences between thrust belts it is useful to differentiate between thrust belts that are related to east e dipping or west w dipping subduction more precisely these either follow or resist the overall eastward mantle flow detected by the hot spot reference frame because of the overall westward drift of the lithosphere we find in e dipping subduction that the basal decollement underlying the eastern plate reaches the surface and involves deep crustal rocks with w dipping subduction however we find that the basal decollement of the eastern plate is warped as well as subducted consequently thrust belts related to e or ne dipping subduction show conspicuous structural and morphologic relief involve deep crustal rocks and are associated with shallow foredeeps on the other hand thrust belts related to w or sw dipping subduction show relatively low structural and morphological relief involve only shallow upper crustal rocks and are associated with deep foredeeps as well as back arc extension the accretionary wedge foredeep back arc basin association is visualized as an overall eastward propagating tectonic wave the accretionary wedge forms in the frontal parts and generally below sea level this is followed by forward migrating extension that cuts the earlier accretionary wedge typically such a system occurs in the context of overall w dipping subduction and is characterized by an arcuate shape e g carpathians apennines barbados etc along the branches of the arc external transpression and internal transtension co exist but with different sense i e sinistral transpression contrasting with dextral transtension we also observe that with w dipping subduction the tangent to a pre deformation marker is descending into the foredeep at an angle in the range of 1 10 while with e or ne dipping subduction the same marker would rise towards the hinterland with typical angles of about 5 10 foredeep subsidence is mainly controlled by the load of the thrust sheets in thrust belts due to e or ne dipping subduction and by the roll back of the subduction hinge in accretionary wedges due to w dipping subduction subsidence or uplift rates in the foredeeps and accretionary wedges related to the two different types of subduction are very different providing different p t t paths in the two geodynamic realms the present shape and structure of the thrust belts belonging to one of these two general types may help us in reconstructing the location of thinned lithosphere and basin evolution in the past

anhydrite bearing rocks from the rožna district moldanubian zone czech republic high grade metamorphosed exhalites several types of anhydrite bearing rocks have been found in the amphibolite facies metamorphosed rocks at the north eastern margin of the moldanubian zone anhydrite either forms monomineralic bands up to 40 cm thick or occurs in the form of disseminated grains in surrounding calc silicate gneiss together with feldspar scapolite amphibole pyroxene epidote and pyrite the isotopic composition of sulphur 34s 30 6 to 32 3 and strontium 87sr 86sr 0 70797 to 0 70781 in anhydrite may indicate a marine source of sulphate the isotopic ratio of strontium is in the same range as that of metamorphosed strata bound barite sulphide ores which have been previously described in the same area the 34s values of coexisting pyrite range from 21 4 to 22 5 the 34sanhydrite pyrite corresponding to the metamorphic temperature of 600 to 660 c in contrast to many submarine exhalative deposits the oxygen isotopic compositions of anhydrite 18o 9 3 to 10 2 are lighter than that of barite 18o 10 4 to 13 8 this indicates that the both minerals are not in isotopic equilibrium therefore it is probable that anhydrite and barite from the ro na district were deposited from fluids that contained different proportions of seawater and hydrothermal fluids or from hydrothermal fluids that underwent variable extent of oxygen isotope exchange with seafloor rocks the 13c values in calcite 13c 17 2 to 18 7 from anhydrite bearing rock are lower than those in distant marbles as graphite is absent in anhydrite and calcite bearing rocks impoverishment in the 13c isotope cannot be attributed to the graphite carbonate isotopic exchange during metamorphism it is proposed that low 13c values in carbonates are caused by pre metamorphic oxidation of organic matter in course of hydrothermal processes anhydrite and anhydrite bearing calc silicate gneiss from the north eastern part of the moldanubian zone are interpreted to be the high grade metamorphosed analogue of anhydrite rich exhalites commonly found in submarine exhalative hydrothermal deposits

unravelling hinterland and offshore palaeogeography from pre to syn orogenic clastic sequences of the betic cordillera sierra espuna spain abstract the malaguide complex betic cordillera occurs in the sierra espuna area se spain providing a favorable setting to study a sedimentary successions from continental and shallow marine to deep marine environments using structural and stratigraphic relations and petrological and geochemical signatures the aim of this work is to outline the sedimentary evolution of the malaguide complex and the el nino fm this succession is arranged into pre orogenic paleocene early oligocene and syn orogenic late oligocene early miocene stages the detrital modes of sandstones of the overall succession are heterogeneous and indicate a multi source area marked by exhumation till an unknown malaguide basement and probably lower units of the internal betic zone e g alpujarride complex in the case of the el nino fm pre orogenic deposits are mainly carbonate with abundant skeletons of intrabasinal to extra basinal larger foraminifera calcareous lithic fragments and quartz grains and metamorphic lithic fragments minor metamorphic lithic fragments occur in the eocene deposits i e espuna fm calcareous lithic fragments and extra basinal fossils lithoclastic bioclasts are mostly present in the early oligocene pre orogenic formations i e as fm and were derived from the paleocene eocene sedimentary successions of the malaguide complex syn orogenic sandstones are quartzolithic with abundant metamorphic and sedimentary lithic fragments slate phyllite fine grained schist ooidal grainstone mudrock and quartz rich siltstone fragments sedimentary lithic fragments were derived from the mesozoic successions of the malaguide complex while metamorphic detritus is related to the malaguide basement probably also alpujarride from burdigalian on that was exhumed starting from the late oligocene mudrocks of the syn orogenic clastics record an increase of phyllosilicate quartz and feldspars and an abrupt decrease in calcite and dolomite the abundance of calcite and dolomite and traces of hematite occur dominantly in the pre orogenic mudrocks the geochemical signatures suggest a provenance mostly derived from felsic source rocks with a minor supply from mafic metavolcanic rocks in some samples of the syn orogenic stage the syn orogenic formations i e rio pliego fm and el nino fm are characterized by higher cr v values than the pre orogenic formations suggesting a mafic supply for the syn orogenic samples in particular the contents of cr average 85 ppm and ni average 48 ppm for the samples of the rio pliego and el nino formations are higher than those samples cr average 20 ppm ni average 14 ppm of the pre orogenic formations palaeoweathering indices suggest low to moderate weathering conditions for the source area s the cenozoic studied succession played a key role in the geodynamic evolution of the betic cordillera representing the key tectonic element of the western mesomediterranean domains

detrital zircon u pb ages in the rif belt northern morocco paleogeographic implications abstract detrital zircon u pb age distributions in mesozoic and cenozoic rocks from the external rif and maghrebian flysch complex including the so called mauretanian internal flysch units are very similar strongly suggesting that the external rif and the entire maghrebian flysch complex were part of the same nw african paleomargin these patterns include scarce paleozoic zircon grains that show influence from the sehoul block neoproterozoic and paleoproterozoic grains are abundant with a dominant ediacaran zircon population at ca 590 ma which could have been sourced from the variscan moroccan mesetas the northern components of the west african craton or from triassic sediments from the central high atlas and argana basins mesoproterozoic zircon ages between 1 1 and 1 6 ga were also observed 15 in the combined age spectra the nearest sources for these being in the central part of the west african craton transport of the mesoproterozoic grains to the nw african paleomargin requires northward directed fluvial systems parallel to the central atlantic continental margin of africa in contrast samples from the internal rif or alboran domain are different to those from the external rif and maghrebian flysch complex especially in the scarcity of mesoproterozoic zircons suggesting that the alboran domain was not a source area for zircons found in the nw african paleomargin

neogene quaternary evolution of the forearc and backarc regions between the serre and aspromonte massifs calabria southern italy abstract the role of tectonics in the neogene quaternary evolution of the forearc basin between the serre and aspromonte massifs located in the southern calabria is widely documented in the exposed sedimentary successions the structuration of these different basins is due to the southeastward migration of the calabrian terranes which led to the subduction of the ionian lithosphere and the spreading of the tyrrhenian back arc basin the area is dominantly displaced by two nw se and ne sw oriented regional fault systems these fault systems were active during the infilling of the neogene quaternary basins and represent complex tear fault systems that accommodated stress generated in the accretionary prism during the subduction of the ionian lithosphere furthermore these structures play a relevant role as part of recent seismotectonic processes which controlled the late quaternary geodynamic evolution of the area

the agost basin betic cordillera alicante province spain a pull apart basin involving salt tectonics the agost basin is characterized by a miocene quaternary shallow marine and continental infilling controlled by the evolution of several curvilinear faults involving salt tectonics derived from triassic rocks from the serravallian on the area experienced a horizontal maximum compression with a rotation of the maximum stress axis from e w to n s the resulting deformation gave rise to a strike slip fault whose evolution is characterized progressively by three stages 1 stepover releasing bend with a dextral motion of blocks 2 very close to pure horizontal compression and 3 restraining bend with a sinistral movement of blocks in particular after an incipient fracturing stage faults generated a pull apart basin with terraced sidewall fault and graben subzones developed in the context of a dextral stepover during the lower part of late miocene p p the occurrence of triassic shales and evaporites played a fundamental role in the tectonic evolution of the study area the salty material flowed along faults during this stage generating salt walls in root zones and salt push up structures at the surface during the purely compressive stage middle part of late miocene p p the salt walls were squeezed to form extrusive mushroom like structures the large amount of clayish and salty material that surfaced was rapidly eroded and deposited into the basin generating prograding fan clinoforms the occurrence of shales and evaporites both in the margins of the basin and in the proper infilling favored folding of basin deposits faulting and the formation of rising blocks later in the last stage upper part of late miocene p p the area was affected by sinistral restraining conditions and faults must have bent to their current shape the progressive folding of the basin and deformation of margins changed the supply points and finally caused the end of deposition and the beginning of the current erosive systems on the basis of the interdisciplinary results the agost basin can be considered a key case of the interference between salt tectonics and the evolution of strike slip fault zones the reconstructed model has been compared with several scaled sandbox analogical models and with some natural pull apart basins

paleogeographic and geodynamic miocene evolution of the tunisian tell numidian and post numidian successions bearing with the maghrebian chain the numidian and post numidian stratigraphy of the tunisian tell has been updated based on 16 stratigraphic sections belonging to the massylian sub domain of the maghrebian flysch basin and to the external domain the new data concern detailed litho and biostratigraphy gaps synchronous marker levels lateral correlations tectonic contacts etc the successions studied show many diachronous and unconformity boundaries delimiting sedimentary depositional sequences related to some tectonic sedimentary processes two main miocene sedimentary successions numidian and post numidian are recognized overlying the sub numidian succession pre early aquitanian by new integrated planktonic foraminifera and calcareous nannoplankton chronostratigraphic analyses allowing an update of the formations studied the miocene tectonic sedimentary relationships and the timing of the deformation are summarized as follows 1 the activation of a foredeep stage and a tectogenesis phase gives rise to an accretionary orogenic wedge during mainly the early miocene 2 a late orogenic phase is checked in the late burdigalian early langhian characterized by a marine glauconitic terrigenous sedimentation 3 a post orogenic generalized phase is confirmed from the middle miocene on in shallow marine or continental sedimentation these results show good correlation along the maghrebian chain and betic cordillera finally a paleogeographic and geodynamic evolutionary model concerning the miocene african tunisian margin is postulated

the oligocene ophiolite derived breccias and sandstones of the val marecchia nappe insights for paleogeography and evolution of northern apennines italy abstract ophiolite derived debrites microbreccias and olistoliths are interbedded in the monte morello and argille varicolori formations of the val marecchia nappe constituting the highest tectonic unit of the north eastern apennines and usually considered as having originated from the external ligurian domain the ophiolite derived clastic rocks were supplied exclusively by an oceanic sequence consisting of peridotite gabbro basalt radiolarite pelagic limestone and shale they are interbedded within a succession made up of fine grained carbonate and siliciclastic turbidites and of pelagic claystones petrographic and sedimentological features of the ophiolite derived breccia and sandstone units testify to an intrabasinal source area for these clastic rocks rather than an extrabasinal origin from subaerially exposed oceanic crust forming the inner flank of the basin as previously suggested due to their oligocene earliest miocene age the deposits in which debrites and olistoliths occur are related to early neo alpine tectonic events that caused reactivation and or inversion of old normal transform faults unstable fault escarpments provided a preferential path for submarine landslide and turbidite emplacement debrites microbreccias and olistoliths therefore were added to the basin fill of fine grained turbidite and pelagic deposits this study suggests that the val marecchia nappe succession was deposited on an oceanic substratum stratigraphy and age of the succession of this nappe can be well framed only in the evolution of the sub ligurian domain whereas they conflict with the interpretation of the val marecchia nappe as a nappe originated from the external ligurian domain as suggested previously by most authors this interpretation also requires an oceanic substratum for the sub ligurian domain i e the existence of an oceanic belt external to the ligurian domain which was deformed only in the early miocene the sub ligurian domain therefore would be an eastern branch of the central tethys and would represent the extension in the northern apennines of the maghrebian lucanian oceanic realm as recognized in the betic cordillera maghrebian chain and southern apennines

tectono stratigraphic and kinematic evolution of the southern apennines calabria peloritani terrane system italy abstract temporal controls such as sedimentation ages in foredeep and wedge top basins combined with information about stratigraphic and metamorphic evolution ages and characterization of magmatic rocks deep structures burial and exhumation histories allowed us to obtain kinematic estimations of the southern apennines calabria peloritani terrane system evolution from the late oligocene to recent calculated thrust front velocities suggest to subdivide the orogenic evolution in main five kinematic stages characterized by different velocity trends nine kinematic complexes from a to i i e sets of tectonic units deformed in the same time range are determined according to foredeep ages these complexes bounded by main regional thrust faults encompass one or more tectonic sub units and successions of different paleoenvironment domains paleogeographic evolution model indicates according to available paleomagnetic data a counterclockwise rotation with a mean angle of 60 for the apennine platform carbonates whereas a mean angle of 20 for the eastern sector of the apennine platform and western side of apulian platform shortening estimations for the apennine successions show values ranging between 55 and 88 and a linear best fit indicating an increase from 60 nw sector to ca 90 se sector such high values are consistent with a deformation dominated by a thin skinned tectonics on the contrary the low value of 28 calculated for mt alpi suggests an exhumation ruled by high angle deep seated structures characterized by limited displacements tectonic vergences referred to middle late miocene late miocene and pliocene middle pleistocene when restored indicate an average eastward tectonic transport finally tectonic evolution is summarized in eleven schematic cross sections and corresponding paleogeographic maps

the early miocene bisciaro volcaniclastic event northern apennines italy a key study for the geodynamic evolution of the central western mediterranean the early miocene bisciaro fm a marly limestone succession cropping out widely in the umbria romagna marche apennines is characterized by a high amount of volcaniclastic content characterizing this unit as a peculiar event of the adria plate margin because of this volcaniclastic event also recognizable in different sectors of the central western mediterranean chains this formation is proposed as a marker for the geodynamic evolution of the area in the bisciaro fm the volcaniclastic supply starts with the raffaello bed earliest aquitanian that marks the base of the formation and ends in the lower portion of the schlier fm late burdigalian langhian p p forty one studied successions allowed the recognition of three main petrofacies 1 pyroclastic deposits volcanic materials more than 90 including the sub petrofacies 1a vitroclastic crystallo vitroclastic tuffs 1b bentonitic deposits and 1c ocraceous and blackish layers 2 resedimented syn eruptive volcanogenic deposits volcanic material 30 90 including the sub petrofacies 2a high density volcanogenic turbidites 2b low density volcanogenic turbidites 2c crystal rich volcanogenic deposits and 2d glauconitic rich volcaniclastites 3 mixing of volcaniclastic sediments with marine deposits volcanic material 5 30 mixed with marine sediments marls calcareous marls and marly limestones coeval volcaniclastic deposits recognizable in different tectonic units of the apennines maghrebian and betic chains show petrofacies and chemical geochemical features related to a similar calc alkaline magmatism the characterization of this event led to the hypothesis of a co genetic relationship between volcanic activity centres primary volcanic systems and depositional basins depositional processes in the early miocene palaeogeographic and palaeotectonic evolution of the central western mediterranean region the results support the proposal of a geodynamic model of this area that considers previously proposed interpretations

overview of the late tertiary recent tectonic and palaeo environmental development of the mediterranean region the late tertiary history of the mediterranean region exemplifies processes of ocean basin closure and continental collision as determined from integrated land and marine evidence during the mesozoic early tertiary tectonic settings were dominated by evolution of neotethys this ocean generally widened eastwards with a number of oceanic strands in the eastern mediterranean area great diversity of tectonic settings and palaeo environments developed during the tertiary closure history of these oceanic basins in the eastern mediterranean region more northerly neotethyan strands were closed by the mid tertiary while oceanic crust remained in the south in the present eastern mediterranean sea area northwards subduction of the remaining southerly neotethyan strand was probably active by the early miocene different areas exhibit different stages of convergence and ocean basin closure in the east the amalgamated eurasian plate had collided with the arabian margin africa by the late miocene while oceanic crust still persisted further west steady state subduction during the late tertiary gave rise to the mediterranean ridge as a substantial mud dominated accretionary wedge in the aegean area sufficient northward subduction took place to activate arc volcanism and pervasive back arc extension short of marginal basin opening in the easternmost mediterranean only limited subduction took place associated with supra subduction zone extension e g in cyprus today steady state subduction continues only locally where vestiges of neotethys remain e g herodotus abyssal plain in the western mediterranean area suturing of the african and eurasian plates initially took place in the betic region early mid tertiary where the neotethys had existed only as a narrow connection with the central north atlantic in the central mediterranean region where the western neotethys was wider northward subduction was active apparently as early as the late cretaceous in a widely accepted interpretation an andean type magmatic arc developed along the southern margin of europe and was then rifted off in the late oligocene early miocene to form the corsica sardinia block opening the north balearic marginal basin in its wake the migrating subduction zone and microcontinent then collided diachronously with north africa related continental units north africa and apulia from late oligocene early miocene giving rise to collisional thrust belts in the northern and southern apennines and along the north african continental margin i e the maghrebian chain to the betic rif area from the early miocene onwards a separate subduction system became active related to removal of neotethyan oceanic crust to the southeast ionian sea fueling suprasubduction zone extension and opening of the tyrrhenian sea orogenic collapse is an alternative mechanism of such extension and is widely believed to have caused divergent thrusting in the betic and rif regions of the westernmost mediterranean at the same time as crustal extension and subsidence of the alboran sea

the late neogene sahabi rivers of the sahara and their climatic and environmental implications for the chad basin this paper is based on the concept that the drainage system of c 7 5 4 6 ma is still reflected in the geomorphology of northeastern chad and adjacent areas of libya during the messinian and early pliocene a large lake was present in the chad basin that is termed neogene lake chad it fluctuated in size in response to the precessional cycle and at times overflowed to the east ne or north giving rise to the sahabi rivers the eosahabi flowed during the drawdown of the mediterranean late messinian and eroded the erdi and part of the east tibesti valley the post rift miocene deposits of the chad basin some several hundred metres in thickness record a transgression over an irregular and faulted terrain with the deposition of coarse and fine clastic material fluviatile and lacustrine environments are represented at least part of the miocene succession belongs to a phase of late miocene lake development fluctuating climate during the messinian and early pliocene led to repeated changes in the environment of the chad and eosahabi basins with over 100 climatic cycles developed this would favour the development of animal species with high adaptability for example to littoral riparian woodland and savanna habitats

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

linking palaeozoic palaeogeography of the betic cordillera to the variscan iberian massif new insight through the first conodonts of the nevado filabride complex graphite rich metamorphic limestones included within low grade black schists of the lowest nevado filabride tectonic unit in the sierra de baza bodurria unit provided the first conodonts found in this complex declinognathodus bernesgae d inaequalis d cf praenoduliferus and idioprioniodus sp this demonstrates the early bashkirian age of the sedimentary protoliths and their deposition in open marine anoxic environments of a continental margin that opened towards the e and that was related to the palaeotethys this breakthrough offers strong support for the hypothesis that the lower nevado filabride units show stratigraphic and palaeogeographic affinities with the external domains of the iberian massif palentian domain of the cantabrian zone in particular consequently this part of the betic internal zones must be related to the basement of the south iberian palaeomargin and excluded from the alboran domain tectonostratigraphic terrane

stratigraphy and tectonics of an internal unit of the southern apennines implications for the geodynamic evolution of the peri tyrrhenian mountain belt the parasicilide succession is a key element of the southern apennine orogen being originally located in the distal portion of the apulian palaeomargin at the neotethys ocean continent transition the succession presently included in the upper nappe complex of the thrust belt has been described elsewhere as a broken formation however detailed investigations carried out in the sele valley point out that there the parasicilide unit is characterized by a coherent stratigraphy therefore in the study area these rocks form a coherent sheet of distal continental margin oceanic sedimentary cover material included within the peri tyrrhenian mountain belt stratigraphic and structural constraints obtained from both pre and synorogenic deposits the latter including both foredeep and thrust top basin sediments suggest that the pre orogenic part of the parasicilide succession subsided into the apennine foredeep in the first part of the burdigalian the studied rocks were then involved in thrusting prior to late burdigalian early langhian times

provenance signatures for the miocene volcaniclastic succession of the tufiti di tusa formation southern apennines italy the tufiti di tusa formation a siliciclastic turbidite system of lower miocene age in southern italy is mainly composed of volcaniclastic and quartzolithic sandstones interbedded with mudrocks sandstones are subdivided into four distinctive petrofacies evolving from quartzolithic to volcaniclastic lithofeldspathic and feldspatholithic reflecting detrital evolution from growing orogen quartzolithic petrofacies to active volcanism volcaniclastic petrofacies the mineralogical composition of the associated mudrocks is predominantly characterized by phyllosilicates mainly illite smectite mixed layers i s r1 associated with minor amounts of i s r0 in the lower part of the succession and i s r3 in its upper part together with illite detrital micas and chlorite and minor amounts of chlorite smectite mixed layers and kaolinite in addition to quartz calcite and feldspars the most abundant phyllosilicates are i s mixed layers 10 a minerals illite and micas and chlorite while kaolinite and chlorite smectite mixed layers are present as a few per cent or in trace amounts x ray diffraction patterns show the occurrence of the ordered i s r1 mixed layers in most samples but at the top of the succession some samples are characterized by i s r3 mixed layers whilst in the lower part of the succession i s r1 is associated with a lower amount of i s r0 these features suggest that the tufiti di tusa formation experienced a medium diagenetic grade and the occurrence of i s r3 could be explained by k availability in samples in the upper part of the succession the lithic fragments in sandstones are metasedimentary rocks of palaeozoic age and andesite to dacite volcanic rocks of early miocene age the associated mudrocks also contain trace element ratios cr v y ni la sc th sc th co th cr cr th and eu eu consistent with a provenance containing intermediate to silicic sources with scarce or absent basic rocks the chemical index of alteration 63 2 to 71 6 suggests a moderate degree of weathering in the source furthermore the k cs ratios of sediments confirm likely moderate rather than intense weathering the index of compositional variability icv values from 1 2 to 2 5 are high enough to suggest the mudrocks are first cycle sediments with little recycling the al ti zr diagram and the th sc v zr sc plot indicate poor sorting and rapid deposition of the sediments detrital and sedimentary evolution of the tufiti di tusa formation provides constraints in terms of relations between a growing orogenic system and active volcanism in the central mediterranean to contribute to geodynamic and palaeogeographic reconstructions of the earliest collision in the southern apennines region

the alboran sea western mediterranean revisited with a view from the moroccan margin this paper presents a new depth to acoustic basement map based on a grid of seismic profiles in the western alboran basin the basement is more than 10 km deep an examination of a seismic profile of this region suggests that late oligocene early miocene 5 km thick synrift formation has been accumulated in this basin this west alboran basin has been formed in an extensional setting but in a fore arc position south of the balearic islands then westwards transported behind a subduction zone

shallow burial and exhumation of the peloritani mountains ne sicily italy insight from paleothermal and structural indicators we used vitrinite refl ectance and mixedlayered clay minerals to investigate levels of diagenesis of the oligocene miocene basin developed on the nappes of the alpine orogen exposed in the peloritani mountains ne sicily paleothermal indicators were integrated with stratigraphic and structural analyses and published apatite fi ssion track and u th sm he ages to defi ne the late evolutionary stages of the peloritani mountains this multimethod approach allowed us to reconstruct the paleogeothermal gradient of the basin in oligocene miocene times to constrain its burial evolution and discriminate between areas where it has been affected by sedimentary and or tectonic load in the southern area of the basin organic and inorganic thermal parameters increase as function of depth suggesting that their evolution was ruled by sedimentary burial they record a decrease in paleogeothermal gradient values marking the evolution of the basin from a forearc to a thrust top setting during the convergence collision process between the calabria peloritani arc and the african plate on the other hand in the northern edge of the basin vitrinite refl ectance values 0 46 0 58 indicate that the thermal evolution of this area was controlled by tectonic burial related to late langhian early serravallian out of sequence thrust tec tonics the tectonic overburden has been totally removed by extensional tectonics and or erosion since the late miocene the short time span at maximum temperature 2 m y elapsing between thrust stack emplacement and the beginning of tectonic overburden removal has allowed only vitrinite refl ectance and thermochronological indicators to record this compressive reactivation

first u pb detrital zircon ages from numidian sandstones in southern apennines italy evidences of african provenance abstract two samples of quartz rich sandstones collected in the numidian flysch of southern apennines italy have been studied to highlight the provenance of detritus using radiometric dating by la icp ms of detrital zircons and to compare the obtained ages with those of the betic and maghrebian chains the provenance of quartzose detritus from european or african plates is still debated in these chains accordingly the ages of the detrital zircons can contribute significantly to discriminate the origin of the quartzose supply the u pb zircon ages n 47 vary from 3047 13 ma mesoarchean to 516 19 ma cambrian the predominance of paleo proteozoic ages 2500 1600 ma and the lack of hercynian and alpine ones suggest a provenance of the numidian supply from north african cratonic areas during the early middle langhian when the numidian successions of southern apennines were deposited in addition a cluster of ages at 773 24 ma and 668 12 ma in one sample and at 664 17 ma in the other sample calculated on zircon domains with magmatic zoning testify to an important contribution from neo proterozoic granitic rocks widely outcropping in the north african craton the age data on detrital zircons from numidian sandstones in southern apennines overlap those found in the numidian sandstones widespread in the betic cordillera and in the maghrebian chain from south spain to sicily this suggests that the entire depositional zone in which numidian flysch deposited was fed from a southerly source represented by the african craton where archean proterozoic and cambrian rocks widely crop out from the atlantic coast to the hoggar and tibesti massifs finally it must be outlined that a meso archean zircon age 3047 ma has been found in the numidian flysch of the southern apennines whereas in the numidian flysch of the maghrebian chain zircons older than paleo proterozoic 1840 ma have not yet been found

the rif chain northern morocco in the late tortonian early messinian tectonics of the western mediterranean orogenic belt evidence from the tanger al manzla wedge top basin

paleoclimatic conditions and paleoweathering processes on mesozoic continental redbeds from western central mediterranean alpine chains abstract chemical and mineralogical analyses of the triassic to lowermost jurassic mudstones from continental redbeds outcropping in the internal domains of the betic rifian and calabria peloritani chains have been used to infer the relationships between paleoclimatic conditions and paleoweathering processes during rifting of a continental crust block that finally detached from adjoining western tethyan realms to form an independent microplate mesomediterranean microplate from jurassic to lower miocene time the studied mudstone samples come from middle triassic and upper triassic beds of the saladilla formation both in the betic cordillera and in the rif whereas the calabria peloritani arc studied mudstones come from upper triassic to lowermost jurassic beds both in the sila and longi taormina units major and trace element concentrations based on the mass balance calculation relative to the upper continental crust show negative values both in gibraltar and calabria peloritani arcs implying that mudstone formation in the early mesozoic involved moderate to intense continental paleoweathering of the crust in particular cao na 2 o mgo sr ba fe 2 o 3 mno and transition metal elements v cr co and ni are more depleted in the triassic to upper jurassic samples of the calabria peloritani samples than in the middle to upper triassic betic rifian samples and suggest an increase of continental paleoweathering in the mediterranean region from the triassic to the jurassic in addition enrichment in sio 2 tio 2 al 2 o 3 k 2 o and incompatible elements in the calabria peloritani arc mudstones indicates sediment recycling effects that gradually increase from the triassic to jurassic time the hinterland paleoweathering and sediment recycling effects have been mathematically distinguished using principal component analysis pc1 is a measure of paleoweathering rate mainly due to humidity positive values against aridity negative values whereas pc2 corresponds to the extent of sediment recycling the results strongly indicate that humidity had increased from the triassic to the jurassic and that the depositional environments in calabria peloritani arc were probably more suitable for sediment recycling these seasonal climate alternations corresponding to an increase in paleoclimatic humidity that favored paleoweathering conditions and recycling processes these results are also confirmed by the mineralogical data which show a higher abundance of kaolinite typical of warm humid conditions in the calabria peloritani mudstones than in those of the betic cordillera and the rif furthermore the comparison among geochemical weathering index values of the studied samples and of recent soils from different climatic zones likely suggests a tropical rainforest climate in the studied area during the triassic to the lowermost jurassic

on the tectonic evolution of the ligurian accretionary complex in southern italy unraveling the deformation pattern characterizing the transition from final oceanic subduction stages to early stages of deformation of a foreland continental margin is crucial for a better understanding of the geodynamic processes taking place at convergent plate boundaries in particular the combined role of internal wedge dynamics and continental margin architecture in controlling the tectonic evolution of an accretionary complex during its final emplacement onto the foreland continent is discussed in this study to this purpose we conducted integrated structural stratigraphic and low temperature thermochronometric analyses on the ligurian accretionary complex units exposed in the campania region italy and on continental margin successions located in their footwall as well as on related foredeep and wedge top basin deposits our results point out a series of late early miocene burdigalian shortening events also involving buttressing of the accretionary wedge against the crustal ramp of the foreland continental margin emplacement of the overthickened accretionary complex onto the distal part of the continental margin was followed by horizontal extension and wedge thinning aiding the development of wedge top depocenters extension may have been either related to reduced subduction rates during the middle miocene or to a period of subduction erosion known to have occurred in the northern apennines in the same time frame early miocene nw se shortening recorded by ligurian accretionary complex units was completely unrelated to later late miocene to pleistocene ne directed thrusting in the apennines which was coeval with backarc extension in the tyrrhenian sea therefore our results emphasize the occurrence of a major discontinuity in the neogene geodynamic evolution of the southern apennines the tectonic history of which may be clearly subdivided from a kinematic point of view into pre and syn tyrrhenian backarc extension stages

meta evaporite sequence exhalative chemical sediments and associated rocks in the proterozoic willyama supergroup south australia implications for metallogenesis abstract the willyama supergroup comprises proterozoic meta sedimentary and meta igneous rocks in western new south wales and eastern south australia and contains the giant broken hill pb zn ag deposit in addition to numerous small stratiform stratabound and vein mineral deposits new lithological geochemical and fluid inclusion data from the olary block west of broken hill suggest the presence of former evaporite rocks now metamorphosed to a variety of chemically and mineralogically unusual lithologies these evaporite rocks overlie relatively oxidised strata and are in turn overlain by reduced graphite bearing pelites rocks of sodic composition abound represented by albite quartz rich rocks calcite actinolite epidote garnet clinopyroxene inferred to represent metamorphosed analcime rich strata of felsic volcaniclastic provenance with variable proportions of carbonates for example calcite dolomite trona and shortite these rocks are interspersed with potassic rocks possibly also with an evaporitic origin in addition to normal clastic meta sediments the presence of halogen rich minerals in a distinctive mineral assemblage hypersaline fluid inclusions pseudomorphic voids and minerals after gypsum and carbonate in addition to tourmalines with isotopically light boron isotopes is interpreted as evidence for a non marine evaporite parent rock for portions of the olary block types of mineral occurrences in the olary block form a continuum between chemical sediments formed by the exhalations of hydrothermal fluids to intrasediment deposits inferred to have been formed due to the chemical changes imposed on these and or diagenetic fluids during their passage through the sedimentary pile disseminated stratabound pyrite including cobaltian types and chalcopyrite extend along strike for many kilometres and are interpreted to have formed by a diagenetic mechanism the presence of massive sulphide bearing strata iron formations barite tourmalinite and manganiferous rocks are typical of chemical sediments derived from hot spring sources the olary block meta evaporites have similar whole rock compositions to tertiary analcime rich rocks of the green river formation wyoming these new data imply that portions of the adjacent broken hill block may also comprise meta evaporites for example the quartz albite rich strata of the thackaringa group and the calcsilicates of the lower broken hill group and that the disseminated cobaltian pyrite mineralisation in the thackaringa group may not be of exhalative origin

the eclogitized pillows of the betic ophiolitic association relics of the tethys ocean floor incorporated in the alpine chain after subduction in the volcanic sequence of the betic ophiolitic association boa volcanic structures and textures are preserved in spite of being metamorphosed to the edogite facies the original quenched glassy margins of the pillows and lava flows are still recognizable by the darker colour fine grained textures and scarcity of phenocrysts the boa eclogitized pillows have chemical compositions very similar to the basalts enriched in lil elements erupted nowadays at the mid oceanic ridges magmatism which generated the boa most likely began under continental rift conditions at the triassic jurassic boundary and continued under ocean floor extensional conditions during the lower and middle jurassic in age and petrological characteristics this magmatism is equivalent to that of the western tethys ophiolites during the late cretaceous due to the collision of african and iberian plates the boa ophiolites were subducted and underwent a metamorphism in the eclogite fades whose climax in the lugros outcrop can be estimated at 650 700 c and about 20 kb

some characteristics of cloud to ground lightning in tropical northern australia peak currents and polarities for the first return strokes of approximately 5000 cloud to ground lightning flashes have been studied the flashes were associated with eight mesoscale convective systems mcss that occurred in tropical northern australia in 1989 during the second field phase of the down under doppler and electricity experiment dundee statistical analysis of the lightning data produced an average peak current independent of polarity of 39 ka when considered with the average cloud top heights of the tropical mcss examined herein the 39 ka peak current average appears to be in general agreement with orville s 1990 hypothesis of latitudinal variation in peak current in six of the dundee mcss consisting of both convective and stratiform precipitation components we found that positive peak current maxima tended to occur in the trailing stratiform region while positive peak current minima were generally situated in convective precipitation we also observed this pattern in a middle latitude mcs that occurred on june 10 11 1985 the magnitude of the positive peak current maxima in the tropical mcss and the middle latitude mcs increased coincidentally in time with the growth of the stratiform regions and reached peak values when the stratiform regions were most intense given the apparent dependence of positive peak current magnitude on the life cycle of the stratiform region and the spatial separation between positive peak current maxima and the convective line we offer further support for a noninductive charging mechanism being responsible for the electrical charging and subsequent lightning observed in the trailing stratiform regions of mcss

geochemistry of metabasites from the nevado filabride complex betic cordilleras spain relics of a dismembered ophiolitic sequence abstract major and trace element distribution including ree data in the metabasites of the nevado filabride complex betic cordilleras spain suggests that the whole mafic ultramafic association represents a dismembered ophiolitic sequence all the analyzed samples have been affected by sea floor alteration yet only the fine grained rocks have suffered some significant mobilization of the lree life the other western mediterranean ophiolites this sequence is related to the opening of the liguro piemontese basin during mesozoic times however the metabasites from betic cordilleras differ from the ophiolitic basalts by higher values of the more incompatible over less incompatible element ratios the entire variation of these ratios in the liguro piemontese basin is related to a dynamic melting process coupled with a diapiric uprise of the mantle source from the stability field of garnet peridotites possibly up to the spinel plagioclase facies transition in this process the ophiolites of the betic cordilleras would record the deepest stages and the lowest degrees of melting this feature is related to the peculiar location of these ophiolites at the western end of the liguro piemontese basin

sense of overthrust shear in the alpine nappes of calabria southern italy abstract southern italy consists tectonically of ophiolite and basement nappes thrust over the apenninic sedimentary nappes whilst all more recent authors agree that the sediments of the apenninic nappes were deposited on apulian basement i e on african continental crust and that the ophiolites were associated with the oceanic basement of the mesozoic tethys the provenance of the basement nappes is still debated new data based on microstructural criteria have shown that the main shear sense of the ophiolite nappes and of the overlying basement nappes in northern calabria is from west to east in today s co ordinate system the basement nappes might not therefore be of austroalpine african provenance but could be of european origin

geologic evolution of the betic cordilleras in the western mediterranean miocene to the present abstract the betic cordilleras were formed during the eo meso and neo alpine evolution of the western mediterranean area during the neo alpine stage the northward subduction of the african plate took place and the algerian provencal basin opened with the creation of oceanic floor associated space problems produced the expulsion and extensive stretching of the internal zones to the west which in turn disrupted and deformed the external zones of the betic and rif cordilleras these occurrences essentially took place in the burdigalian and continued with diminished intensity into the middle miocene following the suturing of the transcurrent contact between the internal and external zones important n60 90 e and nw se faults occurred the betic cordilleras are characterized as having been deformed by regional horizontal shortening compression oriented wnw ese or nw se which gradually rotated to the nnw sse in the late miocene when its most important intramontane neogene basins were formed the alboran basin with a thinned continental crust was formed as a western prolongation of the opening of the algerian provencal basin with its basic features already apparent in the burdigalian the volcanism present in the southeast of the betic cordilleras and in northeast morocco crossing the alboran basin is mainly late miocene in age it is linked to fracturing and exhibits chemistry related to the different thickness of the crust

new data on the vrancea nappe moldavidian basin outer carpathian domain romania paleogeographic and geodynamic reconstructions a study has been performed on the cretaceous to early miocene succession of the vrancea nappe outer carpathians romania based on field reconstruction of the stratigraphic record mineralogical petrographic and geochemical analyses extra basinal clastic supply and intra basinal autochthonous deposits have been differentiated appearing laterally inter fingered and or interbedded the main clastic petrofacies consist of calcarenites sub litharenites quartzarenites sub arkoses and polygenic conglomerates derived from extra basinal margins an alternate internal and external provenance of the different supplies is the result of the paleogeographic re organization of the basin margins system due to tectonic activation and exhumation of rising areas the intra basinal deposits consist of black shales and siliceous sediments silexites and cherty beds evidencing major environmental changes in the moldavidian basin organic matter rich black shales were deposited during anoxic episodes related to sediment starvation and high nutrient influx due to paleogeographic isolation of the basin caused by plate drifting the black shales display relatively high contents in sub mature to mature type ii lipidic organic matter good oil and gas prone source rocks constituting a potentially active petroleum system the intra basinal siliceous sediments are related to oxic pelagic or hemipelagic environments under tectonic quiescence conditions although its increase in the oligocene part of the succession can be correlated with volcanic supplies the integration of all the data in the progressive reorientation of convergence direction carpathian model and their consideration in the framework of a foreland basin led to propose some constrains on the paleogeographic geodynamic evolutionary model of the moldavidian basin from the late cretaceous to the burdigalian

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

triassic redbeds in the malaguide complex betic cordillera spain petrography geochemistry and geodynamic implications abstract sandstone petrography and mudstone mineralogy and geochemistry of triassic mudstones and sandstones from continental redbeds of the malaguide complex betic cordillera southern spain provide useful information on provenance palaeoclimate and geodynamics during the early stages of the pangea break up and on their diagenetic evolution the sandstones are quartzarenites to sub litharenites with minor lithic fragments and rare feldspars the mudstone samples show a paas like elemental distribution the samples likely record recycling processes from their metasedimentary basement rocks that significantly affected the weathering indices and monitors cumulative effects including a first cycle of weathering at the source rocks sandstone composition and chemical mineralogical features of mudstones record a provenance derived from continental block and recycled orogen that were weathered under warm and episodically wet climate source areas were located towards the east of the present day malaguide outcrops and were formed by fairly silicic rock types made up mainly of palaezoic metasedimentary rocks similar to those of the paleozoic underlying series with subordinate contributions from magmatic metamorphic sources and a rare supply from mafic metavolcanic rocks clay mineral distribution of mudstones is dominated by illite and illite smectite mixed layer that result from differences in provenance weathering and burial temperature history illite crystallinity values illitization of kaolinite occurrence of typical authigenic minerals and apatite fission track studies coupled with a subsidence analysis of the whole malaguide succession suggest burial depths of at least 4 6 km with temperatures of 140 160 c typical of the burial diagenetic stage and confirm the middle miocene exhumation of the betic internal domain tectonic stack topped by the malaguide complex

e w opening of the algerian basin western mediterranean we present geophysical and geological evidence of fast 2 cm yr 1 in the east and 5 cm yr 1 in the west e w spreading between 16 and 8 ma in the region behind the gibraltar arc in the algerian basin

interpreting provenance relations from sandstone detrital modes southern italy foreland region stratigraphic record of the miocene tectonic evolution abstract the southern italy orogen preserves deep marine turbitic clastic wedges that record the key tectonic events during structural growing over the adria margin the regional tectonic transition from thick skinned calabrian accretion and deformation during late paleogene to middle miocene to thin skinned southern apennines thrusting since early middle miocene is recorded by diverse contrasting petrofacies in uppermost paleogene and miocene sandstones of dominantly turbiditie deposits most of these sandstones reflect in time quartzolithic and quartzofeldspathic and arkosic petrofacies derived from growing and unroofing calabrian terranes quartzose petrofacies mainly indicate provenance from cratonal african margin during langhian and or from lowland internal domains before its deformation during the cretaceous to paleogene volcaniclastic sandstone petrofacies also testify active volcanism during the late paleogene to early miocene these variable compositions indicate strong palaeogeographic constraints for the central western mediterranean during the neogene reflecting provenance relationships from differentiate source rocks these include interplays between ophiolitiferous uplifted continental shallow to deep crust terranes volcanic and sedimentary mostly carbonate source rocks sandstone detrital modes provide an example of the close relations between clastic compositions and growing orogen in southern italy and may contribute to unravel the geodynamic history of other major orogens

tectono sedimentary evolution of the southern branch of the western tethys maghrebian flysch basin and lucanian ocean consequences for western mediterranean geodynamics the evolution of the oceanic maghrebian flysch basin and its continuation in the southern apennines was studied by reconstructing mainly representative stratigraphic successions in all sectors a common evolution has been identified rifting and drifting phases are indicated by remnants of oceanic crust jurassic limestones cretaceous palaeogene turbiditic and pelagic deposits the pre orogenic sedimentation was mainly controlled by extensional tectonics and sea level changes the occurrence of a generalized foredeep stage since the early miocene is testified by thick siliciclastic and volcaniclastic syn orogenic flysch successions the deformation of the oceanic areas began in the burdigalian and the resulting nappes were stacked in the growing chains during the middle miocene piggy back basins developed and the building of the chains was accomplished in the late tortonian areal distribution and ages of flysch deposits represent an important tool for the study of the diachronous growth of the accretionary wedges

compositional and geochemical signatures for the sedimentary evolution of the middle triassic lower jurassic continental redbeds from western central mediterranean alpine chains abstract compositional and chemical analyses suggest that middle triassic lower liassic continental redbeds in the internal domains of the betic maghrebian and apenninic chains can be considered a regional lithosome marking the triassic jurassic rift valley stage of tethyan rifting which led to the pangaea breakup and subsequent development of a mosaic of plates and microplates sandstones are quartzose to quartzolithic and represent a provenance of continental block and recycled orogen made up mainly of paleozoic metasedimentary rocks similar to those underlying the redbeds mudrocks display k enrichments intense paleoweathering under a hot episodically humid climate with a prolonged dry season and sediment recycling redbeds experienced temperatures in the range of 100 160 c and lithostatic tectonic loading of more than 4 km these redbeds represent an important stratigraphic signature to reconstruct a continental block mesomediterranean microplate that separated different realms of the west

composition and provenance of the macigno formation late oligocene early miocene in the trasimeno lake area northern apennines abstract sandstone petrography and mudstone mineralogy and geochemistry of the late oligocene early miocene terrigenous deposits of the macigno fm of the trasimeno lake area central italy provide new information on provenance paleoenvironment palaeoclimate and geodynamics during the early stages of the northern apennines foreland basin setting sandstones are rich in trace fossils and are quartzofeldspatic with various crystalline phaneritic mostly granitoids and medium low grade metamorphic rock fragments volcanic and sedimentary lithic fragments are rare the mudstone mineralogy contains a large amount of phyllosilicates quartz and feldspars and small amount of calcite which increases in the mid part of succession palaeoweathering indices chemical index of alteration with and without cao value cia and cia respectively suggest a source area that experienced low to moderate weathering and low recycling processes on average cia 66 4 and cia 69 7 furthermore very low and homogeneous values of rb k ratios the sandstone and mudstone composition reflects a provenance derived from uplifted crystalline rocks the different amount in feldspars the variety of lithic fragments the occurrence of mafic and carbonate input coupled with evidence of multi directional flows suggest a provenance from different source areas the geochemical proxies indicate a provenance from both felsic and mafic sources predominantly for the maesta section that shows cr v values ranging from 1 15 to 3 36 typical of source areas composed of both felsic and mafic rocks the western central alps are inferred to be the main source area of the macigno foreland system but significant signals from the mesomediterranean microplate are also testified these new data suggest that the macigno fm was probably located in a peculiar area which received either distal fine turbidite flows from the northernmost alpine area and residual sandy debris flows coming from the westernmost alps

lightning over the gulf stream during the period 15 january 15 march 1986 the average frequency and strength of lightning flashes to the earth s surface over the gulf stream off the carolina coast was greater than that over the adjacent land near the north carolina coast in prefrontal situations the mean number of flashes to the earth s surface per lightning day per grid area 1 latitude 1 longitude was 20 9 in the vicinity of the gulf stream and 4 8 over the adjacent land in postfrontal situations the corresponding numbers were 18 4 and 8 9 most but not all of the lightning flashes over the gulf stream conveyed negative charge to the earth s surface and the increase in the frequency of lightning over the gulf stream was greater for these lightning flashes than for those that carried positive charge to the earth s surface the enhancement in lightning activity over the gulf stream is attributed to the recurrent convective rainbands that form in this region