new evidence for two highstands of the sea during the last interglacial oxygen isotope substage 5e sedimentologic stratigraphic and geochronologic analyses of a previously undescribed carbonate section on oahu hawaii provide new evidence for two distinct sea level highstands on oahu during the last interglacial period oxygen isotope substage 5e whereas electron spin resonance and uranium series ages 122 8 ka to 152 25 ka and 115 10 ka to 160 15 ka respectively of in situ corals place the age of the deposits within substage 5e it is the unique sequence of strata found in these exposures that reveals the two transgressions a highstand lagoonal deposit of coral algal bafflestone is overlain by large seaward dipping slabs of beach rock the beachrock deposited during a mid 5e regression is in turn overlain by a second highstand lagoonal deposit this sequence was deposited in a broad shallow back reef embayment that was very sensitive to fluctuations in sea level elsewhere along much of the shoreline of oahu an in situ coral algal framestone waimanalo formation representing the initial 5e highstand is erosionally truncated on its upper surface this erosional unconformity represents the mid 5e lowstand and separates the framestone from overlying seaward dipping planar bedded grainstone and rudstone leahi formation that accumulated during the second 5e highstand

geodetic strain in peninsular italy between 1875 and 2001 1 we determine geodetic strain in peninsular italy by the gps reoccupation of the first order triangulation network of italy installed from 1860 the uncertainties in the original measurements about 3 ppm and the time span between the two observations imply that tectonic signals larger than about 0 03 ppm yr are resolvable along the apenninic belt where the largest earthquakes are concentrated the geodetic deformation has a clear and consistent strain pattern between adjacent regions well above the uncertainties and shows a pervasive ne sw extension along the tyrrhenian and adriatic coasts the geodetic signal is not homogeneous and is comparable with the uncertainty in the original measurements seismic deformation calculated over the same time interval agrees well with estimated extensional direction but the magnitudes of geodetic and seismic strain differ suggesting that in part of the apennines significant strain accumulation over the past 130 years may not have been released in earthquakes

the puglia uplift se italy an anomaly in the foreland of the apenninic subduction due to buckling of a thick continental lithosphere the apenninic foreland shows two distinct structural signatures comparing the central adriatic sea and the puglia region during the pliocene pleistocene the central adriatic underwent high subsidence rates due to the eastward rollback of the hinge of the west dipping apenninic subduction the puglia region and the bradanic foredeep are located southward along strike in the same foreland but in contrast with the central adriatic after pliocene early pleistocene subsidence they underwent uplift since the middle pleistocene the geometry and the kinematics of the frontal accretionary wedge and related foreland changed from that moment on between the two areas at the front of the central northern apennines off scraping and subsidence continued whereas the foredeep and foreland of the southern apennines were buckled those differences are interpreted as being due to the larger subduction hinge rollback rate since middle pleistocene of the central adriatic lithosphere 70 km thick with respect to the thicker puglia 110 km the different thicknesses of the continental crust and lithosphere were inherited from the mesozoic rifting that disrupted the adriatic plate the different thicknesses appear to have controlled the variable degree of flexure of the lithosphere and its asthenospheric penetration rate the tremiti e w alignment is the right lateral lithospheric transfer zone of those different tectonic regimes the consequent different dip of the subduction in the two sections steeper west of puglia could also explain the lower elevation of the southern apennines compared to their central northern sector

are the seismological and geological observations of the al hoceima morocco rif 2004 earthquake m 6 3 contradictory abstract seismic hazard is associated with recent and present fault activity in mountain ranges in the betic rif alpine mountain chain tectonic activity started in the cretaceous and topographic uplift continues since tortonian times as a consequence of the nw se oblique convergence between africa and eurasia the deformation is active and produces seismicity that sometimes has catastrophic consequences the al hoceima earthquake february 24 2004 considered one of the largest earthquakes ever recorded instrumentally in the westernmost mediterranean m 6 3 caused great damage in the region seismological studies agree that the main shock was situated on land at the limit between the external and internal zones of the rif at a depth of 10 14 km the focal mechanism points to a strike slip solution with a nw se oriented p axis quite similar to those of the significant 1994 earthquake swarm located to the north the epicenter aftershocks distribution would signal the presence of a n s oriented sinistral fault activated by the nw se regional compression associated to plate boundary convergence in this setting the seismogenic fault ruptures related to these seismic events are expected to have reached the earth s surface however detailed field work carried out 1 month after the earthquake does not evidence any n s strike slip coseismic fault in the epicentral area the main observed effects were landslides damages to constructions and locally open cracks indicating an unexpected nw se extension scarce n s faults are normal the main ones being located several kilometers away from the epicentral area to explain this apparent contradiction between geological and seismological observations we propose a decoupled tectonic model with crustal detachments that separate a deep brittle crust from an upper crust undergoing uplift and the development of large folds and normal faults this geological setting common to internal zones of cordilleras may need to be taken into account in future paleoseismicity studies and in the assessment of seismic hazard

the pyrope coesite rocks and their country rocks at parigi dora maira massif western alps detailed petrography mineral chemistry and pt path both the coarse and fine grained varieties of the partly coesite bearing pyrope quartzites their interlayered jadeite kyanite rocks and the biotite phengite gneiss country rock common to all of them were subjected to detailed petrographic and textural studies in order to determine the sequence of crystallisation of their mineral constituents which were also studied analytically by microprobe prior to pyrope and coesite growth the mg rich metapelites were talc kyanite chlorite rutile ellenbergerite schists which upon continued prograde metamorphism developed first pyrope megacrysts in silica deficient local environments at the expense of chlorite talc kyanite and subsequently the smaller pyrope crystals with coesite inclusions from reacting talc kyanite based on geobarometrically useful mineral inclusions as well as on experimentally determined phase relations a prograde pt path simplified for water activity 1 is constructed which passes through the approximate pt conditions 16 kbar and 560 c 29 kbar and 720 c and finally up to 37 kbar at about 800 c where the mg rich metapelite was a pyrope coesite rock with phengite kyanite and talc still present during the retrograde path pyrope was altered metasomatically either into phlogopite kyanite quartz or at a later stage to chlorite muscovite quartz both assemblages yield pt constraints the latter about 7 9 kbar 500 600 c the country rock gneisses have also endured high pressures of at least 15 kbar but they provide mostly constraints on the lowest portion of the uplift conditions within the greenschist facies about 5 kbar 450 c microprobe data are presented for the following minerals pyrope ellenbergerite dumortierite unusually mgti rich jadeite vermiculite formed after na phlogopite paragonite and for several generations of phengite chlorite talc phlogopite dravite and glaucophane in the high pressure rocks as well as for biotite chlorite phengites epidote garnet albite and k feldspar in the country rock gneisses an outstanding open problem identified in this study is the preservation of minerals as inclusions within kyanite and pyrope beyond their pt stability limits

modes of fault reactivation from analogue modeling experiments implications for the seismotectonics of the southern adriatic foreland italy abstract the active tectonics at the front of the southern apennines and in the adriatic foreland is characterized by e w striking right lateral seismogenic faults interpreted as reactivated inherited discontinuities the best studied among these is the molise gondola shear zone mgsz the interaction of these shear zones with the apennines chain is not yet clear to address this open question we developed a set of scaled analogue experiments aimed at analyzing 1 how dextral strike slip motion along a pre existing zone of weakness within the foreland propagates toward the surface and affects the orogenic wedge 2 the propagation of deformation as a function of increasing displacement 3 any insights on the active tectonics of southern italy our results stress the primary role played by these inherited structures when reactivated and confirm that regional e w dextral shear zones are a plausible way of explaining the seismotectonic setting of the external areas of the southern apennines

submarine spring controlled calcification and growth of large rivularia bioherms late pleistocene mis 5e gulf of corinth greece the cyanobacterium rivularia haematites has calcified to form unusually large up to 10 m high bioherms in the pleistocene gulf of corinth today r haematites calcifies only in freshwater environments but these gulf of corinth bioherms have a brackish affinity limited areal extent and occur within marine deposits field relations and preliminary u series dating suggest a marine isotope stage mis 5e age for the bioherms this age is compatible with published mis 5e ages for corals in the marine sediments above the bioherms and is consistent with their current elevation based on average uplift rates bioherm growth during mis 5e constrains their formation during a time of near sea level highstand when the gulf of corinth was marine growth cavities in the bioherms are encrusted by brackish tolerant coralline algae field mapping of the mis 5e highstand palaeoshoreline shows the bioherms grew in water

waveform modeling of historical seismograms of the 1930 irpinia earthquake provides insight on blind faulting in southern apennines italy 1 the southern apennines chain is related to the west dipping subduction of the apulian lithosphere the strongest seismic events mostly occurred in correspondence of the chain axis along normal nw se striking faults parallel to the chain axis these structures are related to mantle wedge upwelling beneath the chain in the foreland faulting develops along e w strike slip to oblique slip faults related to the roll back of the foreland similarly to other historical events in southern apennines the i0 xi mcs intensity scale 23 july 1930 earthquake occurred between the chain axis and the thrust front without surface faulting this event produced more than 1400 casualties and extensive damage elongated approximately e w the analysis of the historical waveforms provides the chance to study the fault geometry of this anomalous event and allow us to clarify its geodynamic significance our results indicate that the ms 6 6 1930 event nucleated at 14 6 3 06 km depth and ruptured a north dipping n100 e striking plane with an oblique motion the fault propagated along the fault strike 32 km to the east at about 2 km s the eastern fault tip is located in proximity of the vulture volcano the 1930 hypocenter similarly to the 1990 mw 5 8 southern apennines event is within the mesozoic carbonates of the apulian foredeep and the rupture developed along a blind fault the 1930 fault kinematics significantly differs from that typical of large southern apennines earthquakes which occur in a distinct seismotectonic domain on late pleistocene to holocene outcropping faults these results stress the role played by pre existing blind faults in the apennines subduction setting

migration of fluid phases and genesis of basalt magmas in subduction zones dehydration and hydration reactions in both the downgoing lithosphere and the overlying mantle wedge have been examined in order to understand the role of h2o in the production of magmas at convergent plate boundaries the subduction of oceanic lithosphere occurring with increasing pressures and rising temperatures causes liberation of h2o from the slab amphibole which can be stable to the highest pt conditions among hydrous phases in the slab decomposes at around 90 km depth it follows that the subducted lithosphere is essentially anhydrous beneath volcanic arcs lying more than 110 km above the slab and that the supply of slab derived h2o is not a direct trigger for the production of arc magmas instead the h2o released from downgoing lithosphere reacts with the forearc mantle wedge to crystallize hydrous minerals serpentine talc amphibole chlorite and phlogopite this hydrated peridotite is dragged downward on the slab toward higher pt regions and releases h2o to shallower potential magma source regions in the mantle wedge combining experimental data on the stability of serpentine and talc with the thermal structure in the mantle wedge it is concluded that those minerals decompose beneath the forearc region on the other hand high pt experimental and thermodynamic data suggest that dehydration of amphibole and chlorite in the downdragged hydrated peridotite can take place just beneath a volcanic front phlogopite in the peridotite decomposes to release h2o at a deeper level about 200 km h2o liberated from the hydrated peridotite causes partial melting of overlying mantle wedge peridotites along with the migration of h2o through the above processes subduction components especially large ion lithophile elements can be overprinted on the magma source region which governs the geochemical characteristics of arc magmas

a geodynamic model of the southern apennines accretionary prism the apennines comprise a neogen quaternary accretionary prism that shows several anomalies with respect to classic alpine type mountain belts namely i low elevation ii a shallow new moho below the core of the belt iii high heat flow in the internal parts iv mainly sedimentary cover involved in the prism v a deep foredeep and vi a fully developed back arc basin the suction exerted by a relatively eastward migrating mantle can determine the eastward retreat of the subduction zone and an asthenospheric wedging at the retreating subduction hinge heat flow geochemical and seismological data support the presence of a hot mantle wedge underlying the western side of the apenninic accretionary prism a thermal model of the belt with foreland dipping isotherms fits with deepening of the seismicity toward the east mantle volatiles signatures are also widespread in springs along the apennines

a new view of italian seismicity using 20 years of instrumental recordings in this paper we show the seismicity of the past 20 years that occurred in italy and surrounding regions hypocentral locations have been obtained by using p and s wave arrival times from the ingv national and several regional permanent seismic networks more than 48 000 events selected from an original data set of about 99 780 are used to reconstruct the most complete seismic picture of the italian region so far the seismicity distribution allows inference on seismotectonics of this complex region of subduction versus continental collision our results clearly reveal the geometry of the adria and the ionian subduction and a continuous normal fault belt in the upper crust following the apennines mountain range the depth of the seismogenic layer is computed from the cut off of seismicity at depth and shows large variations along and across the seismic active regions earthquakes are generated by the different velocity of slab retreat and the subsequent asthenospheric upwelling d 2004 elsevier b v all rights reserved

hydrothermal water rock interaction and the redistribution of li b and cl in the taupo volcanic zone new zealand abstract lithium b and cl occur as trace elements in the dominant protoliths rhyolite andesite and greywacke underlying high temperature hydrothermal systems in the taupo volcanic zone tvz the fluid mobility of li decreases substantially at 200 c 20 c with the pervasive deposition of quartz chlorite regardless of protolith and altering fluid compositions boron and cl are more fluid mobile than li at all temperatures with mobility affected by the rock type composition of circulating aqueous solutions and to a limited extent by incorporation of the trace elements in hydrothermal minerals uptake of b by clays decreases its mobility at 320 c occur compared to volcanic rocks the mobility of b and cl in greywackes is very low and thus the b cl signature of greywacke in hydrothermal aqueous solutions of the tvz is overwhelmed by the effects of rhyolite and andesite dissolution temperature dependent transitions from mg fe clays and phyllosilicates to k bearing illitic clays tend to decrease the mg li ratios in aqueous solutions at 200 c

seismic evidence of longitudinal extension in the southern apennines chain italy the 1997 1998 sannio matese seismic sequence 1 we present evidence of longitudinal extension in the apennines based on data from the 1997 1998 sannio matese seismic sequence the earthquakes occurred between the nw se faults responsible for larger historical earthquakes inversion of focal mechanisms indicates a stress field with a prevailing normal stress characterized by a nnw sse sub horizontal 3 this stress regime is consistent with normal movements along ne sw faults these features suggest that the ne sw faults located in between the nw se faults cannot be interpreted as transfer faults or old faults reactivated during the eastward migration of the chain we propose that the deformation due to the eastward chain migration concentrates along nw se normal faults which are responsible for the largest earthquakes whereas the deformation related to the chain curvature concentrates along ne sw normal faults which are responsible for the lower energy seismic sequences

the b isotopic composition of arc lavas from martinique lesser antilles island arc samples from martinique lesser antilles are enriched in b relative to oceanic crust or the mantle with b contents varying between 5 and 54 ppm and have 11b falling in a range between 1 8 and 5 3 less than the 11b of altered oceanic crust the combination of these results indicates that both sediments and altered oceanic crust must have been involved in the generation of those magmas since the abundance of b in the mantle is too low to produce such low 11b values with such high b concentrations b content and 11b are not correlated showing that the amount of b added to the arc magma was decoupled from its isotopic composition by the mixing of at least three distinct components boron concentrations considered in conjunction with 87sr 86sr 143nd 144nd 18o and 11b data show that variable amounts of b were added by a b enriched fluid to different batches of mantle derived magma the b sr and nd isotopic compositions of these samples are consistent with a two stage process in which enriched magma is produced in the mantle wedge by the addition of an aqueous fluid derived from dehydrating subducting lithosphere and then modified during ascent by assimilation of variable amounts of sediment and altered oceanic crust most of the b contained in the fluid was probably derived from altered oceanic crust plus as little as 3 sediment while the material involved in assimilation was apparently largely continentally derived sediment a two stage process like this also explains the distribution of 18o within the context of the b sr and nd isotopic compositions of martinique arc lavas

european mediterranean regional centroid moment tensors 1997 2000 the mediterranean region is seismically very active and undergoing rapid deformation earthquakes as strong as m 6 are present but relatively rare on the other hand moderate magnitude seismicity 4 5 m 5 5 is widespread and often damaging an improved knowedge of moderate magnitude earthquakes can contribute significantly to a better understanding of active tectonics in the region harvard centroid moment tensors cmt today represent the most widely used reference for reliable source mechanisms but modelling seismic sources with the cmt technique for earthquakes with magnitude less than m 5 5 5 is quite difficult since 1997 we are using an extension of the standard cmt algorithm to compute regional centroid moment tensors rcmt for moderate magnitude earthquakes mw as low as 4 0 analyzing intermediate period surface waves from regional and teleseismic seismograms we routinely apply the algorithm to european mediterranean seismicity to produce a catalog of seismic moment tensors for events with magnitude between 4 5 and 5 5 which generally are not included in the harvard cmt catalog in this paper we show the results for earthquakes that occurred between 1997 and 2000 consisting of 252 solutions and we discuss the characteristics of the catalog and the areas where these new data are most relevant

metamorphic evolution of the central metamorphic belt klamath province california an inverted metamorphic gradient beneath the trinity peridotite metabasalts and metasedimentary rocks of the devonian central metamorphic belt comprise the lower plate of the east dipping trinity thrust system in the klamath province an inverted metamorphic gradient is preserved in the central metamorphic belt metamorphic conditions decrease from amphibolite facies adjacent to the trinity thrust through albite epidote amphibolite facies to upper greenschist facies at the base of the central metamorphic belt mineral chemistry mineral assemblages and limited geothermometry suggest that peak metamorphic conditions decrease structurally downward from 650 50 c at the trinity thrust to 500 50 c at the base of the central metamorphic belt under pressures of 5 3 kbar synmetamorphic ab qtz veins up to 1 m thick increase in abundance towards the trinity thrust infiltration of h2o co2 fluids derived from prograde devolatilization reactions in the central metamorphic belt caused extensive hydration and metasomatism of the trinity peridotite the hanging wall block of the trinity thrust zone geological relationships and the preserved inverted metamorphic gradient suggest that the central metamorphic belt formed in an east dipping devonian subduction zone in an oceanic environment the central metamorphic belt appears to represent a discrete slice of accreted oceanic crust several km thick rather than progressively accreted material metamorphic pressures recorded by the central metamorphic belt are intermediate between the 2 kbar pressures recorded in dynamothermal aureoles beneath obducted ophiolites and the 7 10 kbar preserved in subduction related inverted metamorphic gradients the lack of blueschist facies mineral assemblages in the central metamorphic belt may possibly be explained by an anomalously warm geotherm prior to subduction or early shear heating prior to the arrival of wet rocks at depth

discussion on pleistocene calcified cyanobacterial mounds perachora peninsula central greece a controversy of growth and historygeological society london special publications vol 255 2006 53 69 j e andrews m r leeder c portman p j rowe j smith write we were very interested to read kershaw guo s 2006 analysis of the conflicting views on the growth and history of pleistocene cyanobacterial mounds bioherms from the perachora peninsula in the eastern gulf of corinth rift central greece a new field guide to this classic geological area and these spectacular exposures will soon be available leeder et al 2007 and the issues we debate below have an important bearing on regional uplift rates the role of faulting and the environmental conditions required for cyanobacterial calcification we welcome kershaw guo s 2006 fair and balanced account of competing hypotheses for bioherm evolution and particularly commend and accept their new interpretation of the cavity dwelling pendant coralline algae however we dispute the more fundamental basis of their interpretations and take this opportunity to discuss them further in the vicinity of cape heraion perachora peninsula uplifted pleistocene shorelines of marine isotope stage mis 5a c mis 5e mis 7a c and mis 7e age have been mapped leeder et al 2005 and where possible u th dated using coral aragonite vita finzi 1993 dia et al 1997 leeder et al 2005 the upper part of a prominent terrace at c 25 to 30 m above modern sea level is composed of marine bioclastic marls and carbonates of proven mis 5e age vita finzi 1993 leeder et al 2005 however directly below these sediments is a horizon of spectacular bioherms up to 10 m high fig 1 constructed by calcified cyanobacteria rivularia haematites and coralline algae lithophyllum pustulatum there is controversy regarding the age stratigraphic relations and environment of formation of these bioherms they have variously been interpreted as brackish lake deposits forming immediately before the

small microbialites from the basal triassic mudstone tieshikou jiangxi south china geobiologic features biogenicity and paleoenvironmental implications abstract we report small microbialites from the calcareous mudstone slightly above the permian triassic boundary ptb in the tieshikou section southern jiangxi province south china the newly found microbialite is a bowl like structure which contrasts with the surrounding calcareous mudstone the small microbialite is composed of columnar forms and fan shaped structures mini columnar structures resemble mini stromatolites in plane view most branches are patchy or strip shaped with clotted structures resembling that of a thrombolite fan shaped cement precipitates are comprised of multiple crystal fans that have a radiating texture and that show distinct growth laminae the radiating fabrics are represented by rod shaped filaments under sem which are interpreted as calcified trichomes filaments prominent micropores occur within the rods and they may be the plane views of multiple sheaths of the false branching zone of trichomes thus both the columnar forms and radiating fans are probably microbial in origin moreover three types of nano sized structures intraparticle micropores fibrous biofilms and filamentous sheaths are also pronounced in both the columnar structures and cement fans of the tieshikou microbialite all suggestive of biogenicity these well preserved fibrous biofilms probably represent calcified extracellular polymeric substances eps and linear sheaths are interpreted as the traces of bacterial activities during the precipitation of dolomite crystals the tieshikou microbialite therefore shares similar biogenetic mechanisms with other ptb microbialites the combination of the absence of pyrite framboids slightly negative carbon isotope values and an association with abundant ammonoids bivalves and gastropods indicates oxic conditions during the growth of the tieshikou microbialite moreover the nodular preservational state resembles widely distributed nodular mudstones or muddy limestones of the lower triassic successions worldwide this implies that nodular mudstone or argillaceous limestones may also have been deposited in microbe rich environments in which terrigenous supply was abundant

tectonics of the mattinata fault offshore south gargano southern adriatic sea italy implications for active deformation and seismotectonics in the foreland of the southern apennines the mattinata fault is an e w trending feature 50 km long that cuts across the gargano promontory in the foreland of the southern apennines most researchers agree that it is a strike slip fault although the timing of activity is not well known mainly because of the scarce occurrence of cenozoic sediments this contribution aims to describe the eastward extent of the mattinata fault in the adriatic sea using a grid of multichannel seismic profiles specifically acquired for this study and taking advantage of the occurrence of offshore oligocene to quaternary sediments to help date the deformation results indicate that from the late miocene to the quaternary compression dominated and only a limited component of strike slip occurred along the fault a strike slip tectonic regime on the other hand was likely dominant during the late cretaceous to paleogene seismicity affects gargano at basement depth and extends northward into the central adriatic suggesting that the offshore extent of the mattinata fault may not currently represent the main site of foreland deformation within the adriatic region although the mattinata fault probably originated as a crustal scale strike slip fault it has been subsequently reactivated in different tectonic regimes the strike slip ml 5 4 2002 san giuliano molise earthquake located 70 km west of the mattinata fault outcrop seems to have been related to the reactivation of a set of preexisting foreland faults and it does not characterize the seismotectonics of the entire mattinata fault our reconstruction has wide implications not only for a better understanding of the tertiary evolution and active tectonics of the adriatic foreland but also for general relationships among preexisting structures foreland tectonics and seismotectonics

active stress map of italy we present a new map of the present day stress field in italy obtained from all the available data the map reports 200 horizontal stress directions inferred from 109 borehole breakout data 44 centroid moment tensor solutions 34 other focal mechanisms most of which are from polarity distributions seven stress inversions of microearthquake data two averages of t and p axes of earthquake focal mechanisms in zones of diffuse seismic activity and four fault slip data the integration of breakout data which yield horizontal stress directions with fault plane solutions which reflect the stress regime allows us to obtain an improved map of the present day stress in italy this stress field map can be used for a better comprehension of active tectonic processes for seismic hazard assessment and to foresee the behavior of faults recognized with other methods stress directions obtained from different data although relative to different depth intervals e g 0 7 km for breakouts and 0 20 km for most of the earthquakes and to different tectonic units are consistent since many regions in italy are characterized by an extensional stress regime we report the minimum horizontal stress shmin orientations the map shows that an extensional regime affects most of the apenninic belt conversely a compressional or transpressional regime characterizes the eastern alps the eastern side of the northern apennines and the southern tyrrhenian to northern sicily zone an abrupt change in stress directions marks the transition between northern and southern apennines suggesting that the two arcs are characterized by a different tectonic setting and recent evolution in this paper we report all the data analyzed to date with their geographic coordinates and average stress directions and we describe the main stress provinces in italy in the framework of the tectonic evolution of the region

mantle and slab contributions in arc magmas destructive plate margins are major sites of terrestrial magmatism that have long had a key role in models for the generation of continental crust and the development of chemical heterogeneities in the upper mantle in these models it is important to evaluate the nature and size of contributions from preexisting crust in the generation of magmas above subduction zones and to constrain the size of the fluxes of different elements from the subducted crust and the overlying mantle wedge in arc magmas kay 1 980 hawkesworth ellam 1 989 hawkesworth et al 1 99 1 a mcculloch gamble 1 99 1 the more mobile components of the subducted oceanic crust are the products of element fractionation processes in the upper continental crust the ocean basins and hydrothermal systems on the ocean floor they therefore have distinctive isotope and even trace element ratios that in principle should be readily distinguished from those in peridotite in the mantle wedge prior to subduction in practice however element ratios are almost certainly fractionated during shallow level dehydration of sub ducted material and at greater depths where material from the slab appears to contribute in the generation of arc magmas moreover the isotope signal of slab derived material may be heavily diluted by exchange with

the 2002 molise earthquake sequence what can we learn about the tectonics of southern italy abstract on october 31 2002 a m l 5 4 earthquake occurred in southern italy at the margin between the apenninic thrust belt to the west and the adriatic plate to the east in this area neither historical event nor seismogenic fault is reported in the literature in spite of its moderate magnitude the earthquake caused severe damage in cities close to the epicenter and 27 people out of a total of 29 casualties were killed by the collapse of a primary school in s giuliano di puglia by inverting broadband regional waveforms we computed moment tensor solutions for 15 events as small as m l 3 5 m w 3 7 the obtained focal mechanisms show pure strike slip geometry mainly with focal planes oriented to ns sinistral and ew dextral in several solutions focal planes are rotated counterclockwise in particular for later events occurring west of the mainshock from the relocated aftershock distribution we found that the mainshock ruptured along an ew plane and the fault mechanisms of some aftershocks were not consistent with the mainshock fault plane the observed stress field resulting from the stress tensor inversion shows a maximum principal stress axis with an east west trend n83 w whereas the minimum stress direction is almost n s considering both the aftershock distribution and moment tensor solutions it appears that several pre existing faults were activated rather than a single planar fault associated with the mainshock the finite fault analysis shows a very simple slip distribution with a slow rupture velocity of 1 1 km s that could explain the occurrence of a second mainshock about 30 h after finally we attempt to interpret how the molise sequence is related to the normal faulting system to the west along the apennines and the dextral strike slip mattinata fault to the east

boron isotope record of peak metamorphic ultrahigh pressure and retrograde fluid rock interaction in white mica lago di cignana western alps this study presents boron b concentration and isotope data for white mica from ultra high pressure uhp subduction related metamorphic rocks from lago di cignana western alps italy these rocks are of specific geological interest because they comprise the most deeply subducted rocks of oceanic origin worldwide boron geochemistry can track fluid rock interaction during their metamorphic evolution and provide important insights into mass transfer processes in subduction zones the highest b contents up to 345 g g b occur in peak metamorphic phengite from a garnet phengite quartzite the b isotopic composition is variable 11b 10 3 to 3 6 and correlates positively with b concentrations based on similar textures and major element mica composition neither textural differences prograde growth zoning diffusion nor a retrograde overprint can explain this correlation modelling shows that b devolatilization during metamorphism can explain the general trend but fails to account for the wide compositional and isotopic variability in a single well equilibrated sample we therefore argue that this trend represents fluid rock interaction during peak metamorphic conditions this interpretation is supported by fluid rock interaction modelling of boron leaching and boron addition that can successfully reproduce the observed spread in 11b and b taking into account the local availability of serpentinites as potential source rocks of the fluids the temperatures reached during peak metamorphism that allow for serpentine dehydration and the high positive 11b values 11b 20 5 modelled for the fluids an influx of serpentinite derived fluid appears likely paragonite in lawsonite pseudomorphs in an eclogite and phengite from a retrogressed metabasite have b contents between 12 and 68 g g and 11b values that cluster around 0 11b 5 0 to 3 5 white mica in both samples is related to distinct stages of retrograde metamorphism during exhumation of the rocks the variable b geochemistry can be successfully modelled as fluid rock interaction with low to moderate 3 fluid rock ratios where mica equilibrates with a fluid into which b preferentially partitions causing leaching of b from the rock the metamorphic rocks from lago di cignana show variable retention of b in white mica during subduction related metamorphism and exhumation the variability in the b geochemical signature in white mica is significant and enhances our understanding of metamorphic processes and their role in element transfer in subduction zones

bbe systematics in subduction related metamorphic rocks characterization of the subducted component the mobility of b and be in h2o rich fluids and felsic silicate liquids produced during metamorphism of subducted oceanic slab and sediments has been investigated through analysis of subduction zone metamorphic rocks of the catalina schist california in metasedimentary rocks b be and the range in b be decrease with increasing metamorphic grade mean 72 std dev 41 for lowest grade lawsonite albite fades rocks mean 21 std dev 11 for higher grade greenschist and epidote amphibolite facies equivalents this decrease to more uniformly low b be may be attributed to the preferential removal of b in h2o rich fluids produced by devolatilization reactions over the approximate temperature interval of 350 600 c metamafic rocks do not show pronounced decrease in b be with increasing metamorphic grade however all metamafic samples have b be 30 lower than values for many altered seafloor basalts in amphibolite grade exposures felsic leucosomes and pegmatites reflecting partial melting have low b be similar to their metasedimentary and metamafic hosts which presumably experienced prior reduction in b be during lower temperature devolatilization this evidence for b and be mobility during high p t metamorphism complements studies of b be systematics in arc volcanic rocks in further characterizing mechanisms by which slab derived elements can be added to the source regions of arc lavas before subducted mafic and sedimentary rocks reach wadati benioff zone depths beneath arcs 80 150 km the b be of these rocks is likely to have decreased to 30 thus highly fractionated slab derived hydrous fluids may be necessary to generate the high b be signatures observed in many arcs b be of up to 200 the b be data together with previously presented stable isotope data for the catalina schist demonstrate that subduction zone metamorphic processes are capable of homogenizing presubduction variability in the concentrations of particularly fluid mobile elements in rocks and may through mixing produce fluids which trend toward uniform trace element and isotopic compositions these homogeneous fluids could infiltrate parts of the mantle wedge and contribute to the characteristic trace element and isotopic signatures of arc magma source regions in hotter subduction zones e g involving subduction of young hot oceanic lithosphere silicate melts derived from previously devolatilized sedimentary and mafic rocks may contribute relatively low b be signatures to arc source regions thus significant variations among arcs in the ranges of b be observed in front rank volcanoes e g for the bismarck arc b be 20 190 for the cascades arc b be 5 may be related in part to varying thermal structure which could govern both the b be of hydrous fluids and the relative proportions of hydrous fluid and silicate melt derived from the subducted slab and sediments

lateral propagation of the surface trace of the south alkyonides normal fault segment central greece its impact on models of fault growth and displacement length relationships abstract the evolution of deformed marine terraces and drainage systems have been examined in order to investigate the growth and lateral propagation of an active normal fault geological mapping has revealed three distinct raised marine terraces in the immediate footwall of the western end of the active south alkyonides fault segment safs gulf of corinth central greece we correlate these terraces with sea level highstands at 125 240 and 330 ka using elevation estimates of the inner edges of the terraces we show that uplift rates decrease towards the perachora fault segment boundary at the western end of the safs analysis of terraces and drainage wind gaps in the footwall of the fault shows that the surface trace of the safs propagated westwards at a rate of 12 1 16 7 mm y over at least the last 330 ka whilst the surface trace length has increased analysis of the geometry and kinematics of fault slip suggests that fault length at depth has remained fixed implying progressive increase in the values for the displacement length ratio if this is correct growth is not self similar and fault length has been established early in the evolution of the system i e before 330 ka

seismotectonics of strike slip earthquakes within the deep crust of southern italy geometry kinematics stress field and crustal rheology of the potenza 1990 1991 seismic sequences mmax 5 7 abstract we present a revision and a seismotectonic interpretation of deep crust strike slip earthquake sequences that occurred in 1990 1991 in the southern apennines potenza area the revision is motivated by i the striking similarity to a seismic sequence that occurred in 2002 140 km nnw in an analogous tectonic context molise area suggesting a common seismotectonic environment of regional importance ii the close proximity of such deep strike slip seismicity with shallow extensional seismicity apennine area and iii the lack of knowledge about the mechanical properties of the crust that might justify the observed crustal seismicity a comparison between the revised 1990 1991 earthquakes and the 2002 earthquakes as well as the integration of seismological data with a rheological analysis offer new constraints on the regional seismotectonic context of crustal seismicity in the southern apennines the seismological revision consists of a relocation of the aftershock sequences based on newly constrained velocity models new focal mechanisms of the aftershocks are computed and the active state of stress is constrained via the use of a stress inversion technique the relationships among the observed seismicity the crustal structure of the southern apennines and the rheological layering are analysed along a crustal section crossing southern italy by computing geotherms and two mechanism brittle frictional vs ductile plastic strength rheological profiles the 1990 1991 seismicity is concentrated in a well defined depth range mostly between 15 and 23 km depths this depth range corresponds to the upper pat of the middle crust underlying the apulian sedimentary cover in the footwall of the easternmost apennine thrust system the 3d distribution of the aftershocks the fault kinematics and the stress inversion indicate the activation of a right lateral strike slip fault striking n100 e under a stress field characterized by a sub horizontal n142 trending 1 and a sub horizontal n232 trending 3 very similar to the known stress field of the gargano seismic zone in the apulian foreland the apparent anomalous depths of the earthquakes 15 km and the confinement within a relatively narrow depth range are explained by the crustal rheology which consists of a strong brittle layer at mid crustal depths sandwiched between two plastic horizons this articulated rheological stratification is typical of the central part of the southern apennine crust where the apulian crust is overthrusted by apennine units both the potenza 1990 1991 and the molise 2002 seismic sequences can be interpreted to be due to crustal e w fault zones within the apulian crust inherited from previous tectonic phases and overthrusted by apennine units during the late pliocene middle pleistocene the present strike slip tectonic regime reactivated these fault zones and caused them to move with an uneven mechanical behaviour brittle seismogenic faulting is confined to the strong brittle part of the middle crust this strong brittle layer might also act as a stress guide able to laterally transmit the deviatoric stresses responsible for the strike slip regime in the apulian crust and may explain the close proximity nearly overlapping of the strike slip and normal faulting regimes in the southern apennines from a methodological point of view it seems that rather simple two mechanism rheological profiles though affected by uncertainties are still a useful tool for estimating the rheological properties and likely seismogenic behaviour of the crust

high resolution seismic imaging of the mw5 7 2002 molise southern italy earthquake area evidence of deep fault reactivation 1 we investigate the seismic structure of the mw5 7 2002 molise earthquake area in order to understand the role of e w trending strike slip faults in the tectonics of the southern apennines we apply an innovative seismic migration technique to a high quality data set of earthquakes recorded at a dense local network sp converted waves are migrated in depth to image the high impedance contrast of the apulian platform top buried under the apennines allochthonous cover the continuity of the migrated seismic horizon is broken by vertical steps that we systematically picked along 200 cross sections the best location points of these structures define two main tectonic features the first one is related to nw se oriented normal faults and is consistent with the sw flexure of the foreland lithosphere beneath the orogenic belt the second one indicates that shallow e w oriented trans tensional faults are concentrated directly above the deeper 10 20 km strike slip fault delineating the geometry of a negative flower type structure this fault system delimits a depressed sector of the apulian platform whose geometry is consistent with a pull apart basin inherited from a previous left lateral strike slip tectonic regime the buried structure is analogous to those outcropping in the apulian foreland and in the adriatic offshore to the east this correlation brings new support to the hypothesis of a regional e w trending shear zone cutting the adria plate and suggests that other earthquakes could occur on this or on parallel e w trending strike slip faults

new 234u 230th coral dates from the western gulf of corinth implications for extensional tectonics we derive rates of uplift of 0 7 0 8 mm yr for the western end of the gulf of corinth greece using geomorphic paleaoshoreline modeling we calibrate the modeling with new 234u 230th dates on the coral cladocora caespitosa collected from raised marine terraces uplifted in the footwall of the active psathopyrgos fault the only major active normal fault reported on published maps controlling the downthrown rio straits at the western end of the gulf of corinth in this area of high 15 22 mm yr extension rates measured with gps the ratio of uplift rate to extensional velocity is 0 025 0 035 much lower than values of 0 15 0 25 found further east in the gulf these low values imply that if gps extension rates are correct then mechanical kinematic models developed for the eastern and central gulf may not be applicable to the western gulf

geomorphic evidence of quaternary tectonics within an underlap fault zone of southern apennines italy abstract a composite seismic source the irpinia agri valley fault zone located in the axial sector of the fold and thrust belt of southern apennines italy is investigated this composite source is made up of a series of nearly parallel nw striking normal fault segments which caused many historical earthquakes two of these fault segments known as the san gregorio magno and pergola melandro and the fault related mountain fronts form a wedge shaped right stepping underlap fault zone this work is aimed at documenting tectonic geomorphology and geology of this underlap fault zone the goal is to decipher the evidence of surface topographic interaction between two bounding fault segments and their related mountain fronts in particular computation of geomorphic indices such as mountain front sinuosity s mf water divide sinuosity s wd asymmetry factor af drainage basin elongation b s relief ratio r h hypsometry hi normalized steepness k sn and concavity is integrated with geomorphological analysis the geological mapping and structural analysis in order to assess the recent activity of the fault scarp sets recognized within the underlap zone results are consistent with the nw striking faults as those showing the most recent tectonic activity as also suggested by presence of related slope deposits younger than 38 ka the results of this work therefore show how the integration of a multidisciplinary approach that combines geomorphology morphometry and structural analyses may be key to solving tectonic geomorphology issues in a complex fold and thrust belt configuration

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

high sediment yields and cool wet winters test of last glacial paleoclimates in the northern mediterranean opposing models have been proposed for last glacial paleoclimates in the mediterranean area to discriminate between the alternative models we calculate variations in sediment yield within a high resolution stratigraphic framework developed for the alkyonides basin central greece latest quaternary highstand deposits are distinguised from lowstand lake corinth deposits on the basis of seismic reflection data and micropaleontological and palynological analyses of drop cores after depth conversion and calculation of solid sediment masses in successive time slices sediment discharge rates during the last glacial lowstand interval ca 70 12 ka are shown to have exceeded discharge rates during the preceeding interglacial highstand interval ca 128 70 ka by 60 implying enhanced seasonality during the glacial period with cool dry summer and wet winter conditions in the region sediment yield calculations can thus provide an empirical test of paleoclimate models and offer input to sequence stratigraphic models

seismotectonics of the southern apennines and adriatic foreland insights on active regional e w shear zones from analogue modeling 1 the active tectonics at the front of the southern apennines and in the adriatic foreland is characterized by e w striking right lateral seismogenic faults interpreted as reactivated inherited discontinuities the best studied among these is the molise gondola shear zone the interaction of these shear zones with the apennines chain is not yet clear to address this open question we developed a set of scaled analogue experiments aimed at analyzing 1 how dextral strike slip motion along a preexisting zone of weakness within the foreland propagates toward the surface and affects the orogenic wedge 2 the propagation of deformation as a function of displacement and 3 any insights on the active tectonics of southern italy our results stress the primary role played by these inherited structures when reactivated and confirm that regional e w dextral shear zones are a plausible way of explaining the seismotectonic setting of the external areas of the southern apennines

fault geometries from the space distribution of the 1990 1997 sannio benevento earthquakes inferences on the active deformation in southern apennines in this study we analyze the recent 1990 1997 seismicity that affected the northern sector sannio benevento area of the southern apennines chain we applied the best estimate method bem which collapses hypocentral clouds to the events of low energy md max 4 1 seismic sequences in order to constrain the location and geometry of the seismogenetic structures the results indicate that earthquakes aligned along three main structures two sub parallel structures striking nw se 1990 1992 benevento sequence and one structure striking ne sw 1997 sannio sequence the southernmost nw se structure which dips towards ne overlies the fault that is likely to be responsible for a larger historical earthquake io max xi mcs 1688 earthquake the northernmost nw se striking structure dips towards sw the ne sw striking structure is sub vertical and it is located at the northern tip of the fault segment supposed to be responsible for the 1688 earthquake the spatio temporal evolution of the 1990 1997 seismicity indicates a progressive migration from se benevento to nw sannio associated to a deepening of hypocenters i e from about 5 to 12 km hypocenters cluster at the interface between the major structural discontinuities e g pre existing thrust surfaces or within higher rigidity layers e g the apulia carbonates available focal mechanisms from earthquakes occurred on the recognized nw se and ne sw faults are consistent with dip slip normal solutions this evidences the occurrence of coexisting nw se and ne sw extensions in southern apennines

pleistocene cyanobacterial mounds in the perachora peninsula gulf of corinth greece structure and applications to interpreting sea level history and terrace sequences in an unstable tectonic setting abstract large pleistocene cyanobacterial mounds in the perachora peninsula gulf of corinth greece occur on a cut terrace and are interpreted to have formed in freshwaters on the basis of the principal constructing element a freshwater cyanobacterium rivularia haematites richter et al 1979 neues jahrb geol palaontol 159 14 40 which pre dates all other biota in and on the mounds however because of corals dated at ca 125 ka in marine debris engulfing the mounds the cut terrace has also been considered to be the erosional component of the tyrrhenian stage 5 highstand an episode when the gulf of corinth was flooded by marine water from the mediterranean sea via the rio strait this contradiction is addressed by consideration of mound ecology mounds are up to 10 m high and several tens of metres wide with simple dome to bulbous morphology commonly coalesced with neighbouring mounds mounds consist of accreted layers of a branched structure of r haematites and encrusted by coralline alga lithophyllum pustulatum which can tolerate brackish water no examples of the alga encrusted by rivularia were found the remaining space is filled with clotted microbial structure and layers of micrite containing peloids shell fragments and planktonic foraminifera the mounds formed submerged in water indicated by their accreted structure and rounded morphology the terrace and mounds are bounded by steeply dipping coastal faults with several hundred metres of water depth on neighbouring subsided hangingwall blocks thus the mound field grew on a triangular promontory protruding into the eastern end of the gulf surrounded on two sides by deep water the mounds are here interpreted to have grown when the gulf of corinth was a fresh to brackish lake when mediterranean sea level was below the contemporaneous depth of the threshold at the rio strait therefore the cut terrace on which the mounds occur cannot be the tyrrhenian highstand relative sea level rise permitted seawater flooding to allow firstly colonisation by brackish water tolerant l pustulatum followed by fully marine tyrrhenian highstand biota thus indicating that the mounds grew in a glacial phase probably stage 6 prior to marine tyrrhenian deposits this work has important implications for the relative dating of cut terraces and the deposits on them therefore 1 not all cut terraces in coastal settings are necessarily the result of sea level rise and 2 terrace deposits are not necessarily always genetically related to the cut surface beneath them

boron isotopic composition of subduction zone metamorphic rocks abstract many arc lavas contain material derived from subducted oceanic crust and sediments but it remains unresolved whether this distinctive geochemical signature is transferred from the subducting slab by aqueous fluids silicate melts or both boron isotopic measurements have the potential to distinguish between slab transfer mechanisms because 11 b fractionates preferentially into aqueous fluids whereas little fractionation may occur during partial melting previous studies have shown that 11 b values of island arc lavas 6 to 7 overlap the range of 11 b values for altered oceanic crust 5 to 25 and pelagic sediments and turbidites 7 to 11 secondary ion mass spectrometry sims analyses of minerals in subduction zone metamorphic rocks yield 11 b 11 to 3 suggesting that slab dehydration reactions significantly lower the 11 b values of subducted oceanic crust and sediments in order to explain the higher 11 b values reported for arc lavas as compared to subduction zone metamorphic rocks the b bearing component derived from the metamorphosed slab must be enriched in 11 b relative to the slab favoring an aqueous fluid as the slab transfer mechanism

elemental dispersion and stable isotope fractionation during reactive fluid flow and fluid immiscibility in the bufa del diente aureole ne mexico evidence from radiographies and li b sr nd and pb isotope systematics the 31 6 0 3 ma old bufa del diente alkali syenite ne mexico intruded a sequence of cretaceous limestones with intercalated sub horizontal chert layers the cherts acted as aquifers that facilitated transport of brines and pegmatitic melts within the shallow level 1 kbar contact metamorphic aureole fluid driven reactions between chert and marble wallrock and the influx of late melts and various fluids gave rise to distinct chemical and isotopic signatures within the aquifer and across the zones of infiltration and fluid driven reaction aqueous brines of magmatic origin produced thick wollastonite mantles around the chert layers wollastonite formation occurred at the expense of limestone and chert and generated co2 this co2 induced fluid unmixing into an aqueous brine and a low density co2 rich fluid which was lost to the overlying marble where it oxidized organic matter and caused 13c and 18o shifts in a zone some 5 10 cm wide after wollastonite formation the chert aquifers were locally intruded by pegmatite veins carrying alkali feldspar quartz aegirine augite eudialyte zircon and apatite aqueous fluids that exsolved during crystallization of the pegmatite veins escaped along late cross fractures and migrated along the inner and outer borders of the wollastonite margins chemical dispersion patterns of u al na k p s fe and ree across the chert to marble boundary and its metasomatic rims are shown by autoradiography and neutron induced radiography scavenging of cations at mineralogical contacts and cation transport into the marbles occurred only on the mm to cm scale isotopic data for pb and sr across a simple metachert marble boundary and for pb sr nd b and li across a metachert pegmatite marble sequence demonstrate the following 1 the pb and sr isotopic signature of early fluids was buffered by the carbonate wallrock only late fluids shielded from wallrock interaction by a wollastonite mantle variably preserved a memory of their initial magmatic signature 2 since the nd isotope signature of marble and chert is bound to calcite and clay minerals systematic shifts to unradiogenic nd in marble reflect loss of carbonate bound nd as the wollastonite margin is approached nd in the wollastonite margin is dominated by nd originally bound to clay minerals the later emplacement of the pegmatite which carried the nd isotope signature of its alkali syenite source had little effect on the nd isotopic composition of the wollastonite rim 3 although the li and b isotopic compositions reflect the alkali syenite source they are also affected by isotopic fractionation and partitioning between melt fluid and solids

the classic marine isotope substage 5e since its identi cation nearly fty years ago marine iso tope stage 5 mis 5 has been placed onto absolute time scaleson the basis of three independent approaches cesare emiliani who set up the isotope stages emiliani 1955 depended onuranium series dating of the sediments a method that today isregarded as not generally capable of yielding useful precisionor accuracy broecker and van donk 1970 pioneered the ap proach of correlating to radiometrically dated marine coral ter races thishasbeenmuchaidedinrecentyearsbyimprovementsin the precision and accuracy of these age determinations thathave owed from the development of thermal ionization massspectrometry tims for uranium series dating edwards

alternating marine and lacustrine sedimentation during late quaternary in the gulf of corinth rift basin central greece abstract the gulf of corinth in central greece has a maximum depth of about 900 m and is separated from the open sea by the rion strait with a sill depth of 62 m marked by an extensive submarine terrace during eustatic sea level lowstands the gulf of corinth was a lake under lacustrine conditions stratified sediments accumulated in the deep water basins and turbid underflows from rivers eroded the basin slopes as the sea level rose marine waters flooded the gulf and deltas prograded across the shelves in shallow water areas two key reflectors termed z and x are terrace surfaces commonly erosional which mark the base of the overlying deltaic sequences in deep water basins z and x mark the top of the acoustically stratified sediments interpreted as lacustrine turbidites reflectors y and w mark the base of these stratified intervals and overlie acoustically transparent sections similar to the holocene section the last lacustrine conditions in the gulf z to y were during isotopic stage 2 and terminated about 12 000 yr ago age estimates based on sedimentation rates suggest that the x to w interval corresponds to the stage 4 lowstand of sea level in the western gulf of corinth shoreline transgressive surfaces corresponding to minor transgressions in stage 5 and to major transgression at the end of stage 6 are recognised this seismic stratigraphy permits a detailed interpretation of the history of the gulf of corinth in the past hundred thousand years it also provides a general model for sedimentation in rift basins in which marine and lacustrine sediments alternate

mantle wedge dynamics versus crustal seismicity in the apennines italy 1 in the apennines subduction italy earthquakes mainly occur within the overriding plate along the chain axis the events concentrate in the upper 15 km of the crust above the mantle wedge and focal solutions indicate normal faulting in the foreland the seismogenic volume affects the upper 35 km of the crust focal solutions indicate prevailing reverse faulting in the northern foreland and strike slip faulting in the southern one the deepening of the seismogenic volume from the chain axis to the foreland follows the deepening of the moho and isotherms the seismicity above the mantle wedge is associated with uplift of the chain axial zone volcanism high co2 flux and extension the upward pushing of the asthenospheric mantle and the mantle derived co2 rich fluids trapped within the crust below the chain axis causes this seismicity all these features indicate that the axial zone of apennines is affected by early rifting processes in northern italy the widespread and deeper seismicity in the foreland reflects active accretion processes in the southern foreland the observed dextral strike slip faulting and the lack of reverse focal solutions suggest that accretion processes are not active at present in our interpretation of the apennines subduction the shallower seismicity of the overriding plate is due to the dynamics uprising and eastward migration of the asthenospheric wedge

local pattern of stress field and seismogenic sources in the pergola melandro basin and the agri valley southern italy summary our study area is a ca 50 km long section of the central southern apennines tectonic belt that includes the pergola melandro basin pm and the agri valley av this region is located between the areas affected by the 1980 ms 6 9 irpinia and the 1857 m 7 0 val d agri earthquakes and is characterized by rare historical events and very low and sparse background seismicity in this study we provide new seismological and geophysical information to identify the characteristics of the seismotectonics in the area as the prevailing faulting mechanism and the fit of local to regional stress field these data concern focal mechanisms from waveform modelling and p wave polarities analyses of borehole breakouts and detailed investigation of two seismic sequences all the data cover a significantly broad range of magnitudes and depths and suggest that no important local variation in stress orientation seems to affect this area which shows a ne sw direction of extension consistent with that regionally observed in southern italy such local homogeneity in the stress field pattern is peculiar to the study area the variations of orientation and or type of stress observed in the northern apennines or less than only 100 km toward the northwest within the same tectonic belt are absent here furthermore there is a suggestion for a northeastward sense of dip of the seismogenic faults in the region an interesting constraint to the characterization of seismic sources

controlled source nonlinear tomography a powerful tool to constrain tectonic models of the southern apennines orogenic wedge italy the anatomy of the southern apennines is a matter of compelling debate both thick and thin skinned tectonic models are proposed due to paucity of deep seismic constraints we present new and well defined information on the velocity structure of the mountain range by using an innovative nonlinear tomographic technique applied to refraction wide angle reflection data the velocity interface model shows a high velocity region with values exceeding 7 km s at 8 9 km depth such large velocities cannot be related to sedimentary rocks and imply the presence of shallow crystalline rocks i e the basement involvement in the thrust belt the integration of our results with other geophysical data local earthquake tomography bouguer and magnetic anomalies confirms this interpretation which strongly supports thick skinned tectonics and has significant implications for the seismotectonics and hydrocarbon potential of the southern apennines our inversion approach can be effective in other orogenic wedges when seismic reflection profiling fails to uniquely resolve deep complex structures

metamorphic evolution of two different eclogites in the franciscan complex california u s a the eclogites in california u s a have been regarded as tectonic blocks which formed 150 160 ma ago and have been tectonically incorporated into younger rocks of the franciscan complex of 90 130 ma however in ward creek northern california two different types of eclogites were identified type i is a typical tectonic block and type ii is a possible in situ eclogite formed during the franciscan metamorphism most eclogites in the franciscan complex are type i eclogites type i eclogites in ward creek consist of garnet omphacite epidote glaucophane phengite rutile barroisite quartz and have coarse grained gneissic texture they have precursors of the epidote amphibolite facies and are overprinted in various degrees by blueschist facies retrograde metamorphism remnants of metamorphic rinds which consist of actinolite talc chlorite and formed during metasomatic interaction with serpentinizing peridotite occur at the margins of type i eclogite blocks type ii eclogites are medium grained and consist of garnet chloromelaniticclinopyroxene epidote glaucophane paragonite phengite rutile quartz petrochemical characters of type ii eclogites are similar to those of in situ eclogitic schists in the ward creek metabasite sequence epidote amphibolite f facies precursors metamorphic rinds and overprint of retrogressive blueschist facies metamorphism are not found in type ii eclogites garnets in type ii eclogites are medium grained unaltered and idioblastic and have higher spessartine contents sp14 25 whereas garnets in type i eclogites are coarse grained and chloritized and have lower spessartine contents sp2 7 the pt conditions of peak metamorphism for type ii eclogites are 380 10 11 5 kb type i eclogites follow a counter clockwise pt path from the epidote amphibolite through eclogite to blueschist facies whereas the presumable in situ type ii eclogites follow a clockwise pt path from the blueschist to eclogite facies

the boron isotopic composition of altered oceanic crust samples of drilled oceanic crust from dsdp holes 417a 417d and 418a and odp hole 735b and oceanic crust from the oman and cyprus ophiolites were analyzed for b contents and 11b composite samples from dsdp holes 417a 417d and 418a were used to represent the upper 550 m of altered oceanic crustal layer 2a whole rock samples from the troodos ophiolite cyprus and the oman ophiolite wer selected to represent crustal layer 2b dikes composite samples from odp hole 735b were used to represent crustal layer 3 the b content of the dsdp composites ranges from 7 2 ppm to 104 ppm and correlates with both 18o and k showing that it is a good indicator of the extent of low temperature alteration the 11b of the dsdp composites varies between 2 5 and 5 4 the b content of the samples from the troodos ophiolite ranges from 2 4 ppm to 8 1 ppm 11b varies from 0 9 to 7 8 the b content of the oman ophiolite samples ranges from 5 0 ppm to 11 1 ppm 11b varies from 1 6 to 16 9 the b content of the samples from odp hole 735b ranges from 1 1 ppm to 7 1 ppm 11b varies from 4 3 to 24 9 the general pattern displayed by these samples is one of greatest and most variable b enrichment at the top of the crust and least enrichment at the bottom of the section all of these samples are enriched compared to unaltered morb which is believed to have a b content of approximately 0 5 ppm the 11b values of deeper samples from layers 2b and 3 are more variable and generally higher than those from layer 2a boron contents and 11b are not correlated the data from the dsdp site 417418 composites indicate that the 11b of fluid circulating in the upper crust changes only slightly during alteration increasing by an average of 5 1 with an accompanying decrease in b concentration of 7 low temperature alteration appears to be a water dominated process resulting in minor modification of circulating seawater a minimum water rock ratio of 400 is calculated for these samples implying a minimum low temperature seawater flux through the upper oceanic crust of 3 4 1014 l y the average b content of altered oceanic crust as represented by these samples is 5 2 1 7 ppm and the average 11b is 3 4 1 1 this average isotopic composition is measurably different from the apparent average of oceanic sediments supporting the idea that 11b could be useful for identifying the source s of b in island arcs

geometry kinematics and rates of deformation in a normal fault segment boundary central greece the geometry kinematics and rates of deformation within a fault segment boundary between the ends of two major active normal fault segments have been investigated through examination of a faulted 126 ka marine terrace slip vector azimuths defined by striations on the faults indicate n s extension on c e w faults sub parallel to those from earthquake focal mechanisms together with significant and contemporaneous e w extension on c n s faults summed rates of e w extension along a c 550 m transect 0 17 mm yr are comparable with those for n s extension 0 20 mm yr along a c 350 m transect our observations show that distributed non plane strain extension occurs in fault segment boundaries and this should be noted when studying fault tip fracture toughness and regional deformation rates

marine notches in coastal cliffs indicators of relative sea level change perachora peninsula central greece abstract in several sites in the complex faulted western part of perachora peninsula central greece three principal marine notches in rocky coasts are present in each site no holocene notches occur above the upper of the three notches only subaerial weathering affected the rocks lateral variation in the heights of notches demonstrates differential uplift due to fault control and illustrates the complexity of application of marine notches in interpretation of tectonic history the lower undated notch is prominent in places coincides with modern sea level and is interpreted to be forming now it suggests that the western part of the peninsula has been stable for a considerable time the middle and upper notches vary in height between sites and may not be time equivalent but represent earlier sea level positions in the harbour adjacent to the heraion archaeological site the middle and upper notches are preserved in most places as notch roofs so that gradual uplift led to removal of notch floors by physical chemical and biotic processes in exposed locations however within a few hundred metres west of the harbour four uplifted plus a fifth forming now notches have been illustrated by pirazzoli et al tectonophysics 229 1994 201 that cannot be readily correlated to the harbour site and indicate differential uplift by fault displacement in a more complex situation at mylokopi 6 km ne of heraion three different notch profiles occur in three blocks separated by two faults however within the central block of the three two very different profiles are preserved only tens of metres apart beneath one continuous upper notch roof at the same height this complex arrangement interpreted as variability of exposure to marine processes on different parts of this irregular embayment such that one profile containing three notches was controlled largely by abrasion and formed notches that are vertically more extensive while the other profile containing five narrow notches formed by dissolution and or biological erosion at the same time in the protected east end of the block however if only one or the other profile was visible very different tectonic interpretations would result the bedrock of perachora peninsula also shows important variations in resistance to erosion affecting the resulting notch profiles and some sites are influenced by structurally controlled differential subaerial weathering forming ridges and grooves giving the false impression of extra minor notches the distinction between dissolution controlled and structure controlled minor notches may not be possible in some places the interpretations of notch profiles can be highly complex and influence views of tectonic history in a given region overall the occurrence of three principal notches beneath one uplifted notch roof in several sites indicates that a holocene uplift rates outpaced post glacial sea level rise b there were three principal periods of relative sea level stillstand affecting the perachora peninsula and c uplift of the entire western part of the perachora peninsula is an important component of its tectonic processes probably more important than fault movement within the peninsula

boron isotope systematics of marine sediments abstract boron contents and boron isotopic compositions were determined for modern and ancient permian to miocene marine sediments including pelagic clay calcareous ooze siliceous ooze and neritic clay sediments 11b values of modern marine sediments range from 6 6 to 4 8 isotopic variation is controlled by the simple mixing of four major constituents detritus of continental origin marine smectite biogenic carbonates and biogenic silica detritus of continental origin with an average 11b value of 13 to 8 is the low 11b end member constituent of marine sediments and its boron is largely controlled by the concentration of illite which originates from wind or fluvial transport marine smectite biogenic carbonate and biogenic silica on the other hand represent the high 11b end members with 11b values of 2 3 to 9 2 8 0 to 26 2 and 2 1 to 4 5 respectively these high 11b values are the result of the equilibrium uptake of boron from seawater spatial variations in boron isotopes in the pacific sediments are essentially due to the distribution of the above four constituents although ancient argillaceous sediments shale and slate have boron contents that are identical with those of modern equivalents boron contents of limestone and chert are distinctly lower than those of modern calcareous and siliceous oozes ancient marine sediments have systematically lower 11b values 17 0 to 5 6 than those of the modern sediments the lower 11b values can be caused by diagenesis which induces 1 preferential removal of high 11b boron in calcium carbonate and silica during recrystallization and 2 boron isotopic exchange in the course of the smectite illite transition the observed boron isotopic compositions of ancient argillaceous sediments are distinctly different from those of fresh and altered morb therefore boron isotope systematics will be useful in identifying components from the descending oceanic slab involved in the formation of island arc magma and in investigating mantle crust recycling through subduction processes

quaternary evolution of the corinth rift and its implications for the late cenozoic evolution of the aegean summary we present geological and morphological observations at different scales to constrain rates of faulting and the distribution of deformation in the seismically active aegean region we focus first on the 130 km long corinth rift an asymmetric graben where a flight of terraces of marine origin are uplifted we show that the edges of the terraces lie in the footwall of the normal fault bounding the corinth rift and correspond to sea level highstands of laic pleistocene age using a detailed analysis of aerial and spot imagery supported by field observations we have mapped 10 terrace platforms and strandlines ranging in elevation from 10 to 400 m over distances of 2 to 20 km from the fault the elevation of the terraces inner edges was estimated at 172 sites with an error of 5m this data set contains a precise description of the uplift and flexure of 10 different palaeohorizontal lines with respect to the present sea level to date the deformation we correlate the corinth terraces with late pleistocene oxygen isotope stages of high sea level stands and with global sea level fluctuations using a thick elastic plate model consistent with our current understanding of the earthquake cycle and a boundary element technique we reproduce the geometry of the shorelines to constrain both mechanical parameters and the slip on the fault we show that the seismogenic layer behaves over the long term as if its elastic modulus were reduced by a factor of about 1000 all the terraces are fitted for fault slip increasing in proportion to terrace age and the component of regional uplift is found to be less than 0 3 mm yr 1 the best fits give a slip rate of 11 3 mm yr 1 on the main rift bounding fault over the last 350 kyr other geological and morphologic information allows us to estimate the total age of the main fault 1 ma and to examine the mechanical evolution of the corinth rift the minimum observed sediment thickness in the gulf places an extreme check on the results of the modelling and a lower bound on slip rate of 6 7 mm yr 1 40 per cent less than estimated with modelling even this slip rate is nearly 10 times higher than for comparable features in most of the aegean and elsewhere in the world at a larger scale the spacing and asymmetry of the rift systems in the aegean suggest strain localization in the upper mantle with slow extension starting 15 myr ago or earlier the more recent 1 myr rapid phase of rifting in corinth partly reactivated this earlier phase of extension the younger faulting in corinth appears to result from its present location in the inhomogeneous stress field process zone of the south westward propagating tip of the southern branch of the north anatolian fault we extend these relations to propose a mechanical model for the late cenozoic evolution of the aegean as the arabia europe collision progressed in eastern turkey it caused anatolia to move to the west and the north anatolian fault to propagate into the aegean where the early slow extension started to be modified about 5 ma ago the process of propagation dramatically increased the activity of some but not all of the earlier rifts the model we present is compatible with tectonic observations as well as with the seismicity the palaeomagnetic rotations and the displacement field now observed with gps and slr

fault delineation and regional stress direction from the analysis of background microseismicity in the southern apennines italy abstract the present active faults and stress field acting in the southern apennines italy a structurally complex area characterized by high seismic potential are studied by analyzing the background microseismicity m 3 we used a microearthquake data set consisting of 1312 events that occurred from august 2005 to april 2011 by integrating the data recorded at 42 seismic stations of various networks the refined seismicity locations and focal mechanisms delineate a system of northwest southeast striking normal faults along the apenninic chain and an approximately east west oriented strike slip fault transversely cutting the belt the seismicity along the chain does not occur on a single fault but in a volume delimited by the faults activated during the 1980 irpinia m 6 9 earthquake on subparallel predominantly normal faults results show that the recent low magnitude earthquakes belong to the background seismicity and they are likely generated along the major fault segments activated during the most recent earthquakes suggesting that they are still active today 30 years after the mainshock occurrences the stress inversion from the whole data set suggests that a unique anti apenninic extensional regional stress field could explain the two different faulting styles characterizing the earthquakes that occur along the chain and the east west fault dissecting the belt on the other hand the results obtained by separately inverting the irpinia and the potenza clusters indicate a more complex model that would predict a change from a normal faulting regime acting in the inner sector of the chain to a strike slip regime moving eastward and down depth in the potenza area online material seismicity maps and focal mechanisms

the september 27 2012 ml 4 1 benevento earthquake a case of strike slip faulting in southern apennines italy abstract on september 27 2012 at 01 08 utc a m l 4 1 earthquake started a seismic sequence approximately 10 km east of the city of benevento in southern apennines italy during the following four days about 40 events with m l ranging between 1 3 and 4 1 were detected in the same area where the seismic hazard is one of the largest of the italian peninsula and where several historical and destructive events took place in order to investigate the seismicity spatio temporal pattern and to identify the seismogenic source geometry a detailed analysis was performed integrating data recorded at three different seismic networks the earthquakes were relocated using the double difference technique and focal mechanism solutions were obtained by the moment tensor inversion also to better understand the rupture process seismic source parameters were estimated and apparent source time functions were inverted to retrieve the slip distribution for the largest magnitude event our results show the existence in the study area of roughly e w striking fault plane with a right lateral strike slip kinematics seated at mid crustal depths 10 20 km revealing a characteristic seismicity quite different from that typically associated to the outcropping nw se striking active normal faults that are responsible of moderate to large earthquakes in the southern apennines axial sector in this work we address questions concerning i the presence in the benevento area of a mid crust seismogenic strike slip fault previously unrecognized ii its link to the regional seismotectonic setting and iii the existence of a strike slip tectonic regime that uniformly extends in the footwall of the apennines thrust at relevant depth not only in the apulian foreland as demonstrated to date but also under the mountain chain axial zone

active degassing of mantle derived fluid a geochemical study along the vulture line southern apennines italy abstract we report the results of a geochemical study of gas emissions along a ne sw transect in southern italy in order to test the hypothesis that the region around monte vulture is affected by degassing of mantle derived fluids through a lithospheric discontinuity we also investigated lavas from the monte vulture volcano displaying 3 he 4 he up to 6 0 ra and sr isotopes that are consistent with an origin in mantle that has had minimal pollution from subducted adriatic slab similar 3 he 4 he in fluids from around mt vulture indicate that the deep volcanic system is still degassing mantle derived he occurs in fluids along the length of the vulture line reinforcing the hypothesis that it is a deep tectonic discontinuity along which mantle fluids and or melts advect to the surface the co 2 3 he ratios are highly variable 2 7 10 8 2 15 10 11 in response to processes such as gas dissolution into aquifers addition of crustal gases and degassing fractionation

pendant bioconstructions cemented by microbial carbonate in submerged marine caves holocene se sicily abstract unusual pendant bioconstructions occur within two submerged caves in the plemmirio marine protected area south of syracuse se sicily these cm to dm sized bioconstructions project downward from the cave roofs the main framework builders are serpulids belonging to the genera protula semivermilia and josephella encrusting bryozoans corals hydrozoans and sponges are subordinately present whereas bivalves and brachiopods are overall rare these faunal associations are characteristic of the studied caves but only in some places they form small bioconstructions that are cemented by microbial carbonates made up by autochthonous peloidal to clotted peloidal and aphanitic micrite the autochthonous micrite stabilizes the pendant bioconstructions herein referred to as biostalactites the microbial carbonate reveals high contents of bacterial lipid biomarkers among the most abundant compounds are mono o alkyl glycerol ethers mages and branched fatty acids 10 me c16 0 iso and anteiso c15 0 and c17 0 interpreted as biomarkers of sulfate reducing bacteria other compounds preserved in the autochthonous carbonates include lipids derived from marine zoo and phytoplankton brassicasterol dinosterol and monounsaturated short chain fatty acids unspecified marine bacteria saturated and monounsaturated short chain fatty acids and land plants long chain fatty acids long chain alcohols stigmasterol sitosterol and campesterol the observed lipid biomarker signatures are remarkably similar to those of post glacial reefal microbialites where microbialite formation in cavities of the coral framework was also mediated by sulfate reducing bacteria in the submerged caves of plemmirio marine protected area serpulid colonies apparently occur preferentially where freshwater is seeping through crevices in the limestone the consequent nutrification is believed to favor serpulid aggregation and the growth of other skeletal i e bryozoans and corals and soft bodied organisms i e sponges and ascidiae the resultant accumulation of biomass and its taphonomy provide niches for sulfate reducing bacteria which induce carbonate precipitation cementing and stabilizing the biostalactites the finding of pendant cemented bioconstructions in the mazzere and granchi caves of the plemmirio marine protected area reveals that sulfate reducing bacteria are involved in microbialite formation in various cryptic environments the formation of such peloidal to clotted peloidal microcrystalline carbonates in cryptic ecosystems is a significant factor for the stabilization of different kinds of bioconstructions spanning from small biostalactites to large reefs

a holocene coral algal reef at mavra litharia gulf of corinth greece structure history and applications in relative sea level change a holocene coral algal reef at mavra litharia south central coast of gulf of corinth greece is exposed from ca 2 to 9 3 m above sea level on an uplifting footwall associated with the eliki fault the reef lacks sea level critical species but its coralline algal assemblage indicates a ca 10 m water depth reef frame components date from 9280 8730 years bp to 6343 5993 years bp so the reef frame grew between ca 10 000 and 6000 years bp the youngest dated shells 1860 305 years bp from the site are accessory organisms collected from the lowest 2 m of outcrop one of which dendropoma grew at sea level stiros s c and pirazzoli p 1998 late quaternary coastal changes in the gulf of corinth greece tectonics earthquake archaeology guidebook for the gulf of corinth field trip patras university greece patras september 14 16 1998 reef history has four phases a growth and lithification of reef b development of smooth walled dissolution pipes and caves in the reef c colonisation of dissolution surfaces by mn fe crusts that may be bacterially formed barnacles serpulid worms and rock boring bivalves and d uplift to present position where much of the reef is eroded sea level history after 11 500 years bp when rising post glacial sea level overtopped the rio sill and returned the gulf of corinth to a marine environment is reconstructed calculations of interplay between sea level rise and tectonic uplift suggest that between 11 500 and 10 000 years bp sea level rose very quickly associated with deglaciation at the close of the younger dryas mwp 1b at a maximum of 25 6 mm year broadly consistent with other studies then slowed to ca 4 4 mm year until 6000 years bp when sea level was ca 3 m below modern after which sea level rose at ca 0 5 mm year to modern day tectonic uplift rate of maximum 3 mm year slower than sea level rise means that the reef could not catch up to sea level until recent times explaining its fossil assemblage the pipe cave system is interpreted as having formed when the reef top was emerged but much dissolution occurred beneath sea level because of insufficient time to allow uplift and resubmergence intense rainfall during the mid holocene pluvial phase ca 6000 years bp for the eastern mediterranean which affected large areas of the mediterranean is suggested as the mechanism and timing of submarine dissolution

distributed normal faulting in the tip zone of the south alkyonides fault system gulf of corinth constrained using 36cl exposure dating of late quaternary wave cut platforms abstract the geometry rates and kinematics of active faulting in the region close to the tip of a major crustal scale normal fault in the gulf of corinth greece are investigated using detailed fault mapping and new absolute dating fault offsets have been dated using a combination of 234u 230th coral dates and in situ 36cl cosmogenic exposure ages for sediments and wave cut platforms deformed by the faults our results show that deformation in the tip zone is distributed across as many as eight faults arranged within 700 m across strike each of which deforms deposits and landforms associated with the 125 ka marine terrace of marine isotope stage 5e summed throw rates across strike achieve values as high as 0 3 1 6 mm yr values that are comparable to those at the centre of the crustal scale fault 2 3 mm yr from holocene palaeoseismology and 3 4 mm yr from gps geodesy the relatively high deformation rate and distributed deformation in the tip zone are discussed in terms of stress enhancement from rupture of neighbouring crustal scale faults and in terms of how this should be considered during fault based seismic hazard assessment

source composition and distribution of the fluid in the kurile mantle wedge constraints from across arc variations of b nb and b isotopes b and nb concentrations and b isotope composition were determined for lavas covering the entire length of the kurile arc b nb and 11b of these lavas show clear across arc variations in which both are highest at the trench side and continuously decrease as the slab depth increases b nb in the volcanic front lavas 8 25 is significantly higher than those of morb and oib indicating that the mantle wedge is extensively metasomatized by b rich fluid derived from the subducting slab the frontal 11b values are also out of the range of morb and oib and systematic difference exists between northern kurile nk 5 4 0 5 and central and southern kurile csk 4 3 0 3 however these two parameters approach or coincide with mantle values at the most back arc side the 11b and 87sr 86sr linearly correlate with nb b suggesting control by simple mixing of two isotopically homogeneous components that is slab derived fluid and mantle wedge the estimated 11b and 87sr 86sr of the fluid are 7 0 0 6 and 0 70326 0 00005 for nk and 6 3 0 3 and 0 7033 for csk respectively these fluid compositions are consistent with a source constituted by 95 altered oceanic crust and 5 oceanic sediment with the slight difference between nk and csk resulting from the different lithologies of subducting sediments the mantle wedge beneath the kurile arc has b sr and nd isotope compositions identical with morb but shows significantly higher b nb the above trends bear a close resemblance to those observed in the izu arc strongly suggesting their universality in the arc system the across arc decline of b nb observed both in kurile and izu implies that the fluid flux from the slab continuously decreases as the slab depth increases however this relates only to a final stage of slab dehydration since most of the volatile components are lost at the fore arc region in contrast to b k is uniformly enriched across the arc this requires control by a k bearing mineral phase either in the slab phengite or the mantle wedge phlogopite although such a mineral is responsible for only a small part of the whole fluid transport

the geochemical cycle of boron constraints from boron isotope partitioning experiments between mica and fluid abstract the fractionation of boron isotopes between synthetic boromuscovite and fluid was experimentally determined at 3 0 gpa 500 c and 3 0 gpa 700 c for near neutral fluids 11b mica fluid 11b mica 11b fluid is 10 9 1 3 at 500 c and 6 5 0 4 at 700 c this supports earlier assumptions that the main fractionation effect is due to the change from trigonal coordination of boron in neutral fluids to tetrahedrally coordinated boron in micas clays and melts the t dependence of this effect is approximated by the equation 11b mica clay melt neutral fluid 10 69 1000 t k 3 88 r2 0 992 valid from 25 c for fluid clay up to about 1000 c for fluid silicate melt experiments at 0 4 gpa that used strongly basic fluids produced significantly lower fractionations with 11b mica fluid of 7 4 1 0 at 400 c and 4 8 1 0 at 500 c showing the reduced fractionation effect when large amounts of boron in basic fluids are tetrahedrally coordinated field studies have shown that boron concentrations and 11b 10b ratios in volcanic arcs systematically decrease across the arc with increasing distance from the trench thus reflecting the thermal structure of the subducting slab our experiments show that the boron isotopic signature in volcanic arcs probably results from continuous dehydration of micas along a distinct p t range continuous slab dehydration and boron transport via fluid into the mantle wedge is responsible for the boron isotopic signature in volcanic arcs

cross arc geochemical variations in the kurile arc as a function of slab depth lavas from transects across the kurile islands arc showed geochemical variations related to changes in the compositions of fluids derived from the subducting slab enrichment factors for boron cesium arsenic and antimony all elements with strong affinities for water decreased across the arc this decrease is presumably related to losses of water rich fluids during the dehydration of the subducting plate enrichments of potassium barium beryllium 10 and the light rare earth elements remained constant these species may move in silica rich fluids liberated from the slab at greater depths

the stability and composition of phengitic muscovite and associated phases from 5 5 to 11 gpa implications for deeply subducted sediments abstract the stability and composition of phengitic muscovite was investigated from 5 5 11 gpa 700 1150 c in synthesis experiments performed in a multianvil apparatus starting materials consisted of natural minerals with a bulk composition similar to that of a k deficient intermediate dioctahedral trioctahedral mica phengitic muscovite was found to be stable from 5 5 11 gpa at 900 c phengite melting occurs between 1075 1150 c at 7 8 gpa and 1000 1050 c at 10 gpa at 10 11 gpa 800 c octahedral cation deficient ocd muscovite and k hollandite are observed rather than phengite the average phengite content of muscovite is positively correlated with pressure ranging from 3 65 si pfu at 5 5 gpa to 3 81 si pfu at 11 gpa the maximum phengite content of stable muscovite appears to be 3 80 3 85 si pfu most phengite examined exhibits at least minor solid solution towards phlogopite averaging 2 04 0 06 2 octahedral cations pfu the hydrous phases phengite lawsonite topaz oh and mg pumpellyite occur between 6 8 gpa 700 900 c with increasing pressure lawsonite and mg pumpellyite dehydrate to form garnet between 8 9 gpa with increasing temperature mg pumpellyite lawsonite and topaz oh devolatilize to form garnet and kyanite between 900 1000 c at 7 8 gpa phengitic muscovite and topaz oh would be stable in hydrous sediments in cool mature subduction zones to depths exceeding 360 km while lawsonite and mg pumpellyite would be stable to 240 300 km allowing the transport of h2o contained in these phases deep into the upper mantle in warmer subduction zones the dehydration of mg pumpellyite lawsonite and topaz oh as well as the melting of phengite would result in fluid release at depths of 180 240 km the presence of phengite at far greater depths than the zone of melt generation beneath arcs 100 150 km requires a mechanism such as the partitioning of k be b ba and rb into migrating fluids rather than the simple dehydration of phengite beneath arcs in order to provide for the transfer of these slab signature elements from phengite into arc magmas

episodic uplift deduced from holocene shorelines in the perachora peninsula corinth area greece four raised shorelines between 1 1 m and 3 5 m have been identified at two localities on the perachora peninsula and were dated by ams 14c to between 6400 and 1500 calibrated years ago uplift movements seem to have occurred in increments of 0 8 0 3 m with a return period of about 1600 years the last uplift coincided with a regional tectonic paroxysm which has already been documented in several areas of the eastern mediterranean the average uplift rate was probably faster during the holocene than the average since the last interglacial period no important vertical displacement occurred in this area at the time of or after the 1981 earthquake but a new episode of coseismic uplift may be in preparation

low temperature eclogites and eclogitic schists in mn rich metabasites in ward creek california mn and fe effects on the transition between blueschist and eclogite

beryllium and boron in subduction zone minerals an ion microprobe study secondary ion mass spectrometry was used to measure the distribution of be b rb sr y nb ba and ce among minerals in rocks from the franciscan complex and catalina schist paleosubduction zone terranes the rocks examined represent a wide range of metamorphic pressure temperature conditions 6 15 kb 300 750 c and include metasomatized and migmatitic samples white mica is the primary host of be 2 5 ppm and b 107 ppm in the rocks examined average concentrations amphibole be 0 7 b 15 ppm lawsonite be 0 9 b 37 ppm and biotite be 0 9 b 25 ppm may also contain significant amounts of both be and b omphacite may host be 4 1 ppm in veins 0 7 ppm groundmass and chlorite is a minor host of b 22 ppm minerals in these subduction zone metamorphic rocks that lack measurable be or b include albite apatite calcite clinozoisite epidote garnet ilmenite sphene stilpnomelane plagioclase quartz rutile and zoisite white mica biotite and stilpnomelane are the major mineral hosts of rb 90 300 and 30 ppm respectively and ba 2100 1000 and 4700 ppm epidote and lawsonite are the major host minerals of sr 600 and 300 ppm and ce 12 and 15 ppm garnet epidote lawsonite and sphene host y 100 30 40 and 60 ppm respectively sphene 77 ppm 1 analysis ilmenite and rutile host nb evidence of veining and metasomatism is strongly correlated with be and or b enrichment of white mica omphacite amphibole and lawsonite at the p t conditions examined both be and b appear to be transported in aqueous fluids at depths of 20 50 km in subduction zones the transfer of be b and other elements from the subducted slab into the mantle wedge can be accomplished by aqueous fluids transfer of the elements hosted by white mica could result directly from the breakdown of white mica through pressure dependent dehydration reactions or alternatively the be and b in white mica could be partitioned into infiltrating fluids produced at deeper levels in the slab and subsequently transported into the region of are magma genesis

deep structure of the campanian lucanian arc southern apennine italy abstract recent exploration activities and successful discovery of large oil fields in the upper val d agri area southern apennine italy have encouraged the collection of large quantities of geological and geophysical data and their integration into comprehensive geological models here we present a series of structural profiles based on several hundred kilometres of seismic lines two and three dimensional and the results of many deep wells the best seismic lines have been extensively reprocessed and also tied to magnetotelluric data geological interpretations of those lines have been interactively tested and verified by gravity and magnetic modelling and structural balancing the wells and seismic data demonstrate that the fundamental tracts of the deep architecture of the orogen as it appears today were developed only at the end of the late pliocene the final closure of the ensialic shear zone responsible for the subduction of at least 150 km of continental lithosphere originally underlying the lagonegro basin can be dated as early pliocene the involvement of the inner apulian platform in the core of the belt and the activation of a new and more external left lateral oblique ensialic shear zone can be constrained to the late pliocene pleistocene the seismic profiles clearly show the underthrusting of the outer apulian platform unit beneath the inner apulian platform unit the thick skinned character of the plio pleistocene contractional structures is evident from the structural profiles this geometry is constrained by gravity magnetic data and structural considerations according to the relatively steep angle of dip about 10 of the apulian foreland beneath the chain the structural profiles depict the general architecture of the campanian lucanian arc the apennine platform and lagonegro unit are largely allochthonous and a part of the lagonegro basement could be buried below the apennine platform sole thrust the neogene plastic successions of the apennine platform and lagonegro basin were detached and now outcrop in the bradanic foredeep the inner apulian platform constitutes a huge thrust sheet structured as a wide antiform in the core of the belt its regional culmination roughly corresponds to the val d agri area extensional and transtensional structures cross cut the pre existing compressional structures as shown by the quaternary valleys of vallo di diano and val d agri the profiles shown also highlight the existing contrast between the deep structures in the core of the belt and the tectonic style of the lagonegro liguride and sicilide units these units were in fact subjected to brittle ductile deformation under metamorphic part of liguridi units and deep diagenetic to anchizonal conditions lagonegro units and were affected by a general overthrust shear directed towards the ne the inner apulian platform was on the contrary involved in the thrust belt together with its basement whereas the outer apulian platform affected by a subduction underwent a regional bending with associated normal faulting

serpentinization and infiltration metasomatism in the trinity peridotite klamath province northern california implications for subduction zones the trinity peridotite was emplaced over metabasalts and metasedimentary rocks of the central metamorphic belt along the devonian trinity thrust zone three metamorphic events can be recognized in the trinity peridotite 1 antigorite d 63 to 65 formation related to regional underthrusting of the central metamorphic belt 2 contact metamorphism associated with mesozoic dioritic plutons and 3 late stage formation of lizardite brucite and chrysotile d 127 to 175 due to infiltration of meteoric waters abundant relict phases indicate incomplete reactions and strongly suggest that the availability of h2o was a controlling factor during serpentinization antigorite event 1 formed as a result of infiltration into the trinity peridotite of mixed h2o co2 fluids derived from the underlying central metamorphic belt foliation defined by magnetite veins and shear zones within antigorite serpentinites are subparallel to the trinity thrust the assemblage fo atg chl mag tr carb reflects partial hydration of peridotite at 425 570 c talc rich serpentinite formed along the thrust as a result of the infiltration of silica bearing fluids metasomatic mass balance calculations based on silica solubilities and the extent of antigorite serpentinization suggest that 80 175 volumes of fluid have passed through a given volume of original peridotite at the trinity thrust the trinity thrust probably represents a devonian subduction zone thermodynamic calculations suggest that hydration reactions account for 30 35 of the total heat released by the cooling trinity peridotite by analogy similar hydration reactions are to be expected in the overlying mantle wedge of a subduction zone which act to retard cooling of the hanging wall just as dehydration reactions delay heating of the downgoing slab metasomatic zones formed in peridotite at the trinity thrust may reflect similar metasomatic processes to those proposed to occur in the mantle wedge above a subducting slab

stratigraphy palaeoenvironments and model for the deposition of the abdur reef limestone context for an important archaeological site from the last interglacial on the red sea coast of eritrea stone tools discovered within uplifted marine terraces along the red sea coast of eritrea at the abdur archaeological site dated to 125 7 ka the last interglacial marine isotope stage 5e show that early humans occupied coastal areas by this time walter et al 2000 nature 405 65 69 in the present paper the stratigraphy facies types and faunal composition from 25 measured sections of the tool bearing abdur reef limestone arl are documented in detail and interpreted to provide a palaeoenvironmental context for the stone artefacts and a model for the deposition of the arl the arl represents a complex marine terrace sequence erosional surfaces indicative of interrupted sedimentation are locally observed at two levels within the arl they subdivide the complex into three subunits named 5e1 5e2 and 5e3 representing different stages of the marine isotope stage 5e sea level highstand comprising six depositional phases i vi of the arl subunit 5e1 begins with the initial transgression of the 5e sea level highstand leading to the deposition of widespread lag gravels on which rich oyster beds developed in shallow water phase i it further records rapid deepening accompanied by the deposition of low energy carbonates with scarce corals phase ii and later shoaling characterised by local development of a fringing reef tract in a sedimented environment phase iii subunit 5e1 is capped locally by a burrowed hardground that is laterally equivalent to depositional discontinuities interpreted as caused by a globally recognised mid 5e sea level low stand phase iv extensive reef build up in response to sea level rise and improved conditions for coral growth characterises subunit 5e2 phase v a possible second sea level drop during the 5e highstand is inferred from the oyster encrusted upper surface of subunit 5e2 subunit 5e3 encompasses restricted coral patches that developed on the upper surface of the underlying subunit during the last stage of the 5e marine high stand phase vi two different toolkits are found in the arl one consists of bifacial hand axes and cores of the acheulian industry typically associated with the oyster beds encrusted on the transgressive lag deposits the other consists of middle stone age msa type obsidian flakes and blades mainly found in the nearshore and beach environments alongside debris from marine invertebrates and large land mammals the distribution of these tools suggests that foraging activities of early humans varied with environmental setting the abdur archaeological site represents a late example of the acheulian msa transition seen as a benchmark for early modern human behaviour and is to date the earliest well dated example of early human adaptation to marine food resources

microbialite morphology structure and growth a model of the upper jurassic reefs of the chay peninsula western france abstract during the early kimmeridgian the northern margin of the aquitaine basin western france is characterised by a significant development of coral reefs the reef formation of the chay peninsula comprises two main reefal units in which the microbial structures can contribute up to 70 of framework the microbial crusts which played an important role in the stabilisation and growth of the reef body show the characteristic clotted aspect of thrombolitic microbialites corals are the main skeletal components of the build ups the bioconstructions of the chay area are thus classified as coral thrombolite reefs four main morpho structural types of microbial crusts are distinguished 1 pseudostalactitic microbialites on the roof of intra reef palaeocaves 2 mamillated microbialites found either on the undersides or on the flanks of the bioherms 3 reticular microbialites in marginal parts of the reefs and between adjacent bioconstructed units and 4 interstitial microbialites in voids of bioclastic deposits thrombolitic crusts developed on various substrates such as corals bivalves or bioclasts the thrombolites formed a dense clotted and or micropeloidal microbial framework in which macro and micro encrusters also occur variations in accumulation rate strongly influenced the reef morphology in particular its relief above the sediment surface the coalescence of the coral microbialite patches created numerous intra reef cavities of metre scale dimensions the direction of microbial growth which defined the macroscopic microbialite forms strongly depended on the position within the reef framework but was also controlled by water energy accumulation rate and light availability

reactivation of deep faults beneath southern apennines evidence from the 1990 1991 potenza seismic sequences we relocate the 1990 1991 potenza southern apennines belt italy sequences and calculate focal mechanisms this seismicity clusters along an e w dextral strike slip structure second order clusters are also present and reflect the activation of minor shears the depth distribution of earthquakes evidences a peak between 14 and 20 km within the basement of the subducting apulian plate the analysed seismicity does not mirror that of southern apennines which include nw se striking normal faults and earthquakes concentrated within the first 15 km of the crust we suggest that the e w faults affecting the foreland region of apennine propagate up to 25 km of depth the potenza earthquakes reflect the reactivation of a deep preexisting fault system we conclude that the seismotectonic setting of apennines is characterized by nw se normal faults affecting the upper 15 km of the crust and by e w deeper strike slip faults cutting the crystalline basement of the chain

the impacts of sea level changes during latest pleistocene and holocene times on the morphology of the ionian and aegean seas se alpine europe abstract the tentative coastline configuration in the ionian and aegean seas in three late pleistocene holocene time slices is given based on the global eustatic sea level curve in combination with local geological and geoarcheological data at lowstand stage 2 21 500 cal yr bp years before present sea level 120 m extensive shelves existed in the northern aegean sea and to a second degree in the eastern aegean sea and in the northern and central parts of the ionian sea many islands were connected with each other and with the mainland a great part of the periphery of gulfs that have an entrance less than 120 m deep was subaerially exposed while in their central parts lakes were formed at 11 500 cal yr bp sea level 60 m the exposed shelf was much restricted most of the gulfs were overflowed by the advancing sea and only a few islands were still connected with the mainland finally at 8000 cal yr bp and onward the sea initially intruded the lowlands and the gulfs but the subsequent sediment input by the rivers regressed the sea to its present position thus many human settlements and old cities that were maritime during hellenistic or older times are now a few to tens of kilometers inland

rapid sea level changes at the close of the last interglacial substage 5e recorded in bahamian island geology rapid and abrupt relative sea level changes within the last interglacial substage 5e are recorded in the island geology of the tectonically stable bahamas from 132 to 118 ka reef growth reached a maximum elevation near 2 m as indicated by fossil reef elevation across the platform whereas bioeroded notches are incised in coastal cliffs as high as 6 m the end of the interval is characterized by voluminous eolianites exhibiting palm tree and frond impressions it is inferred that sea level for most of the interval remained near 2 m restraining reef growth and that the notch at 6 m represents a rapid and brief excursion just before the close of the substage the subsequent fall must have been rapid in order to leave the notch profile intact and mobilize windward lagoon ooids into dunes before cementation could anchor them in order to explain the rapid rise to 6 m glacial surging is invoked the subsequent fall also rapid may be a consequence of the surge flooding high latitudes and providing enough moisture to initiate reglaciation and drawdown

sub orbital sea level change in early mis 5e new evidence from the gulf of corinth greece abstract new evidence from uplifted marine isotope stage mis 5e carbonate deposits in the gulf of corinth demonstrate two rapid sub orbitally forced sea level oscillations in the early part of mis 5e microbial bioherms with inter grown marine coralline algae are interpreted as early highstand deposits presence of thin vadose flowstone speleothem coating inter bioherm surfaces mark a short lived regression of 10 m followed by sea level recovery and re establishment of the highstand marked by coralline algae coating inter bioherm cavity surfaces these marine algae are then coated by a younger vadose flowstone thick enough to provide an uncontaminated u th date of 134 8 2 0 ka the dated flowstone is itself encrusted by marine fauna and the entire sequence overlain by highstand marine sediments and marine aragonite cements dated to 114 118 ka part of the sustained mis 5e highstand the age of the younger flowstone demonstrates that the early highstand occurred before 134 8 2 0 ka and uplift arguments suggest that the bioherms are unlikely to be older than 136 ka these data are consistent with the notion that most of termination ii tii sea level rise had occurred before 135 ka indeed they suggest sea level at this time reached about 2 4 4 m below present sea level 6 18 4 m higher than previous estimates this early highstand was itself punctuated by a rapid sea level oscillation of 10 m as yet undated and this oscillation supported by new tii sea level data from the red sea siddall m bard e rohling e j hemleben c 2006 sea level reversal during termination ii geology 34 817 820 probably occurred in about 1000 yr the flowstone dated at 134 8 2 0 ka is interpreted to record the early part of the aladdin s cave regressive event from papua new guinea although in greece only the first 16 m of the event is recorded the new data presented here support a recently published red sea tii sea level curve they also highlight minor discrepancies in the absolute dating of these early mis 5e sea level events worldwide

understanding the structural setting in the southern apennines italy insight from gravity gradient tensor abstract the lucania apennines form the frontal part of the apennines in southern italy this orogenic belt was formed in response to late miocene early pleistocene shortening and allochthon emplacement toward the northeast and was subsequently affected by extensional faulting which migrated to northeast ahead of the thrust system as a result contraction structures are found associated to pliocene early pleistocene thrust top basins in the ne part of the area whereas extensional faults shape middle pleistocene holocene basin on the sw sector the main structural grain of the belt is nw se but e w structures are widespread in the area as a result of phases of non coaxial thrusting and strike slip faulting the analysis one by one of the components of the gravity gradient tensor ggt has proved to yield a fine image of the structural setting of the investigated area ggt is a second rank tensor containing the second spatial derivatives of the gravity potential and in this paper is used instead than the more traditional gravity data the tzz component allows an accurate description of the location and of the shape of basins and other structures but different components of the ggt provide even more detailed insights for such structures in particular we found that the tzy and tyy locate well those structures trending closer to the e w direction for both thrust top and extensional basins and their termination against the main nw se structures the combined use of components of ggt provides a finer definition of the anomaly sources particularly if a good knowledge of their strike and depth is independently estimated with other geological and geophysical investigations

boron isotope fractionation during supercritical phase separation abstract boron isotopic fractionation between vapor and brine phases separated under supercritical conditions has been experimentally examined using a na ca k cl fluid experiments were conducted at 425 440 and 450 c phase separation was controlled by adjusting pressure fractionation between the coexisting phases was less than 0 5 in contrast fractionation between trigonal and tetrahedral b at these temperatures has been predicted to be approximately 8 the lack of fractionation suggests that the trigonal tetrahedral speciation of b is similar in the two phases although this result may not be general for other fluid compositions it is relevant to ridge crest hydrothermal solutions and indicates that the boron isotopic compositions of these solutions reflect the proportions of b from seawater and crustal sources and not phase separation

the 8 june 2008 mw 6 4 earthquake in northwest peloponnese western greece a case of fault reactivation in an overpressured lower crust abstract on 8 june 2008 a strong m w 6 4 earthquake occurred in the area of northwest peloponnese western greece the event originated in the lower crust and was caused by the rupture of a previously unknown fault probably inherited from past tectonic phases in this study we perform a stress inversion of all available focal mechanisms in this area in order to obtain an estimate of the regional stress field it is shown that the maximum principal stress axis has an azimuth of n273 e and forms an angle of 63 with the fault s strike which is well constrained by seismological observations this implies that the fault was severely misoriented with respect to the prevailing stress field assuming friction coefficients in the range 0 65 0 85 calculation of pore fluid factors for a variety of input parameters seems to confirm the presence of elevated fluid pressure near the hypocenter because they reach superhydrostatic to lithostatic values 0 80 1 0 the source of these fluids is probably of deep origin and may have to do with upper mantle degassing this suggestion is supported by the presence of mantle helium in spring waters close to the epicenter and by low pn velocities consistent with partially molten mantle beneath northwest peloponnese