the rare earth element ree mineralisation potential of highly fractionated rhyolites a potential low grade bulk tonnage source of critical metals abstract the rare earth elements ree have become crucial for modern industry technology and medicine with the increase in demand for these elements over the past few years currently being met by relatively few well known mineral deposits this lack of a secure supply of the ree has led to increased research into potential alternative sources of these in demand elements the primary fractionation processes involved in the petrogenesis of highly fractionated high silica rhyolites can cause the magmas that form these units to become preferentially enriched in the ree especially in the more valuable heavy ree hree although this is dependent on the mineral assemblages fractionated by the system in question a factor that is in turn a function of the source and tectonic setting of a given magmatic event the mineralogy of the ree is also important with volatile exsolution and vapour phase activity within highly evolved rhyolite systems potentially having a key role in concentrating the ree and other elements into concentrations and more importantly potentially acid leachable and therefore processable minerals that may be economically viable to extract this combined with the fact these rhyolites are often enriched in other critical and or economically important metals e g y nb ta be li f sn rb th and u means that these volcanic units should be considered as potential sources of these critical metals in addition the large volume nature of these rhyolites combined with the fact they frequently crop out at the earth s surface makes them ideally suited for more economical bulk open pit extraction this suggests that these high silica ree enriched rhyolites should be considered potential ree analogues of bulk tonnage low grade porphyry cu deposits warranting further investigation to determine whether these rhyolites are a viable new source of the ree especially the hree and are potential targets for future mineral exploration

occurrence stratigraphy and geochemistry of late quaternary tephra layers in the aegean sea and the marmara sea abstract several discrete tephra layers occur in 2 5 10 3 m long cores from the aegean sea whereas a single tephra is identified in 3 5 9 7 m long cores from the marmara sea major and trace element data on these tephras delineate eight distinct groups the geochemical data and multivariate statistics allow the correlation of the tephra layers with six previously described marine tephras from the eastern mediterranean sea potential terrestrial sources are suggested for the others the chronostratigraphy of the tephra layers was established using several radiocarbon dates and the oxygen isotope stratigraphy from two long piston cores four widespread tephra layers occur within the upper quaternary sediments of the aegean sea the two youngest widespread tephra layers were derived from the santorini volcano of south central aegean sea z2 the minoan eruption ca 3 6 ka and y2 the cape riva eruption ca 21 7 ka the y2 tephra is also identified in three piston cores from the marmara sea the two older widespread tephra layers originated from the eruptions which emplaced the campanian ignimbrite of the italian volcanic provinces i e the y5 tephra ca 39 3 ka and from the nisyros volcano of the southeastern aegean sea the consistent occurrence of the nisyros tephra below the y5 tephra confirms similar findings in a lake core on the island of lesbos linear extrapolations using the oxygen isotope stratigraphy suggest an age of 42 44 ka for the nisyros eruption three additional tephra layers with a limited regional distribution are identified in the aegean sea cores two of these tephras originated from the yali volcano of the southeastern aegean sea and from the aeolian islands i e x1 tephra a series of six mugearite tephra beds in the south skiros basin is interpreted as a set of redeposited turbidites

a new contribution to the late quaternary tephrostratigraphy of the mediterranean aegean sea core lc21 tephra layers preserved in marine sediments can contribute to the reconstruction of volcanic histories and potentially act as stratigraphic isochrons to link together environmental records recent de velopments in the detection of volcanic ash tephra at levels where none is macroscopically visible so called crypto tephra have greatly enhanced the potential of tephrostratigraphy for synchronising environmental and archaeological records by expanding the areas over which tephras are found in this paper crypto tephra extraction techniques allow the recovery of 8 non visible tephra layers to add to the 9 visible layers in a marine sediment core lc21 from the se aegean sea to form the longest single core record of volcanic activity in the aegean sea using a novel shard specific methodology sources of the tephra shards are identified on the basis of their major and trace element single shard geochemistry by comparison with geochemical data from proximal mediterranean volcanic stratigraphies the results indicate that the tephra layers are derived from 14 or 15 separate eruptions in the last ca 161 ka bp 9 from santorini 2 or 3 from kos yali or nisyros 2 from the campanian province and one from pan telleria the attributions of these tephra layers indicate that 1 inter plinian eruptions from santorini may have produced regionally significant tephra deposits 2 marine tephrostratigraphies can provide unique and invaluable data to eruptive histories for island volcanoes and 3 tephra from both pantelleria and campania may be used to correlate marine records from the aegean sea to those from the tyrrhenian adriatic and ionian seas

depletion of light rare earth elements in felsic magmas contrary to simple generalizations about their behavior light rare earth elements lree do not act as incompatible elements in very felsic magmas in fact lree concentrations typically decrease often drastically during differentiation of such magmas the simplest explanation for this depletion involves the separation of minute easily overlooked quantities of an extremely lree rich accessory mineral either monazite or allanite our data indicate that felsic liquids with 50 ppm lree may be saturated in either of these accessories and that the concentration required for saturation decreases in increasingly felsic liquids this accounts for incompatible behavior of lree even at high concentrations in mafic magmas in contrast to compatible behavior at low concentrations in felsic magmas partitioning of lree into solid rather than liquid has important implications for trace element and nd isotope modeling of crustal anatexis as well as for magma differentiation

the last 40 ka tephrostratigraphic record of lake ohrid albania and macedonia a very distal archive for ash dispersal from italian volcanoes abstract a 1075 cm long core lz1120 was recovered in the south eastern part of the lake ohrid republics of macedonia and albania and sampled for identification of tephra layers magnetic susceptibility investigations show rather high magnetic values throughout the core with peaks unrelated to the occurrence of tephra layers but instead to the relative abundance of detrital magnetic minerals in the sediment naked eye inspection of the core allowed us to identify of two tephra layers at 896 897 cm and 1070 1075 cm laboratory inspection of the grain size fraction 125 m allowed for the identification of a third cryptotephra at 310 315 cm major element analyses on glass shards of the tephra layers at 896 897 cm and 1070 1075 cm show a trachytic composition and indicate a correlation with the regionally dispersed y 3 and y 5 tephra layers dated at ca 30 and 39 cal ka bp the cryptotephra at 310 315 cm has a mugearitic benmoreitic composition and was correlated with the fl eruption of mt etna dated at 3370 70 cal yr bp these ages are in agreement with five 14 c ams measurements carried out on plant remains and macrofossils from the lake sediments at different depths along the core the recognition of distal tephra from italian volcanoes allows us to link the lake ohrid succession to other archives located in the mediterranean area and in eastern europe the benmoreitic mugearitic tephra layer at 310 315 cm is the first recognition in the balkan area of a distal ash deposit from a mid intensity explosive eruption of mt etna as far as 600 km from the source

early miocene kirka phrigian caldera western turkey eskisehir province preliminary volcanology age and geochemistry data abstract large rhyolitic ignimbrite occurrences are closely connected to the early miocene initiation of extension in the central western anatolia crossing the tavsanli afyon zones field and laboratory data performed at the apex of the eskisehir afyon isparta volcanic area allowed recognition of newly identified caldera structure named here kirka phrigian caldera transtensive distensive tectonic stresses since 25 ma ago resulted in the nnw sse elongation of the magma chamber and influenced the roughly elliptical shape of the subsided block caldera floor the caldera which is roughly oval 24 km 15 km in shape formed during a series of collapse events starting at 19 ma by the generation of a huge volume of extra and intracaldera ignimbrites intracaldera post collapse sedimentation and further volcanism at the northern edge at 18 6 ma were controlled through subsidence related faults with generation of a series of volcanic structures domes and lavas showing a large compositional range enriched mantle components within the subcontinental lithospheric mantle began to melt via decompression melting during the initiation of extension the heat resulting from the fractionation of ascending mantle melts produced the silicic compositions in large mushy crustal reservoirs interaction of these melts with fertile crustal rocks further caused crustal anataxis and consequently two different compositions rhyolite 1 and rhyolite 2 the eruptions of kirka phrigian caldera related ignimbrites were probably triggered by basaltic intrusion rock volumes and geochemical evidence suggest that silicic volcanic rocks come from a long lived complex magma chamber system after caldera generation there was a northern shift to small volume extra and intra caldera episodic rhyolitic basaltic trachy andesitic trachytic and lamproitic volcanism the latter being the youngest 16 2 ma indicating a more primitive magma input which originated in an enriched mantle lithosphere the rock succession provides a direct picture of the state of the magmatic system at the time of eruptions that generated caldera and post caldera structures and offers an excellent example of silicic magma generation and associated potassic and ultrapotassic intermediate mafic rocks in a post collisional extensional setting

seismicity in the hellenic volcanic arc relation between seismic parameters and the geophysical fields in the region summary a study of the spatial distribution of seismicity and seismic hazard and geophysical parameters is undertaken along the hellenic volcanic arc hva seismicity of the area is divided in a cellular manner allowing analysis of the localized seismicity parameters and representation of their regional variation as contour maps extreme value analysis locates a zone of highest seismicity just west of centre of the hva around the cyclades islands non probabilistic modelling of the strain energy release process in terms of magnitudes equivalent to the average annual energy release rate m and the maximum possible energy release in a seismic cycle m3 enhances this picture maximum values of m and m3 are more tightly localized in the central cyclades west of amorgos island and also in the east of the hva in the sporadhes north west of rhodes isocyclic contours of the waiting times for m3 show values in excess of 70 years in the cyclades and eastern sporadhes i e the zones of largest earthquakes show the longest strain accumulation periods the waiting time for the hva as a whole is about 54 years and at present it appears to be about 75 per cent through to accumulation of the notional maximum strain energy the b value of the magnitude frequency distribution shows a consistent spatial variation along the hva which is not sensitive to subdivision into different focal depth ranges regional contour maps of the b values and maps of local values of heat flow magnetic and electrical anomalies compared with the bouguer gravity anomaly map indicate correlations which reflect the deformation of the aegean shallow crust in relation to the deep intrusive magmatic processes the correlations between the different geophysical fields are displaced commensurate with an aegean extension of approximately 45 km

unified local magnitude scale for earthquakes of south balkan area a homogeneous earthquake catalog spanning 1964 1995 for the southern balkan area is presented by expressing the size of the earthquakes in a unified local magnitude scale the strategy followed to produce this catalog is also presented local magnitudes calculated by six balkan seismological centers ath the isk tir ttg sko have been used in order to obtain relations between the estimated m l values from the greek seismological centers ath and the and the remaining four balkan stations since it was found that local magnitudes estimated by ath and the are almost identical they have been used as one data set so as to correlate with the data of each one of the remaining four seismological stations based on the proposed relations a unified local magnitude m lgr is given for each earthquake of the regional catalog a published scaling relation between the m l values from ath and the networks and the corresponding seismic moment magnitude m w was used in combination with the above relations in order to enable the conversion of any m l value from any station into m w the catalog completeness has been checked and the b value has been calculated for the complete data sample

the intav intercomparison of electron beam microanalysis of glass by tephrochronology laboratories results and recommendations abstract the international focus group on tephrochronology and volcanism intav of the international union for quaternary research inqua has conducted an intercomparison of tephrochronology laboratories with electron beam microanalytical data on volcanic glasses submitted from 27 instruments at 24 institutions in 9 countries this assessment includes most active tephrochronology laboratories and represents the largest intercomparison exercise yet conducted by the tephrochronology community the intercomparison was motivated by the desire to assess the quality of data currently being produced and to stimulate improvements in analytical protocols and data reporting that will increase the efficacy of tephra fingerprinting and correlation participating laboratories were each supplied with a mount containing three samples for analysis 1 rhyolitic lipari obsidian id3506 2 phonolitic sheep track tephra from mt edziza british columbia canada and 3 basaltic laki 1783 a d tephra a fourth sample rhyolitic old crow tephra was also distributed most laboratories submitted extensive details of their analytical procedures in addition to their analytical results most used some combination of defocused or rastered beam and modest beam current to reduce alkali element migration approximately two thirds reported that they routinely analyze one or more secondary standards to evaluate data quality and instrument performance despite substantial variety in procedures and calibration standards most mean concentrations compare favorably between laboratories and with other data typically four or fewer data contributions had means for a given element on a given sample that differed by more than 2 standard deviations from the overall means obtaining accurate na 2 o concentrations for the phonolitic tephra proved to be a challenge for many laboratories only one half of the data sets had means within 1 standard deviation of the 8 2 wt na 2 o value obtained by other methods one mean is higher and 14 are lower three of the data set means fall below 7 wt na 2 o most submissions had relative precision better than 1 5 for the major elements for low abundance elements the precision varied substantially with relative standard deviations as small as 10 and as large as 110 because of the strong response to this project the tephrochronology community now has a large comparative data set derived from common reference materials that will facilitate improvements in accuracy and precision and which can enable improved use of published data produced by the participating laboratories finally recommendations are provided for improving accuracy precision and reporting of electron beam microanalytical data from glasses

acigol rhyolite field central anatolia part ii geochemical and isotopic sr nd pb δ18o constraints on volcanism involving two high silica rhyolite suites the acigol rhyolite field erupted the most recent high silica rhyolites within the cappadocian volcanic province of central anatolia turkey it comprises two sequences of domes and pyroclastic rocks with eruption ages of 150 200 ka eastern group and 20 25 ka western group compositionally the eastern rhyolite group lavas are less evolved sio2 74 76 wt whereas the western group has higher silica abundance sio2 77 wt with extremely depleted feldspar compatible trace elements within each group compositional variability is small and 143nd 144nd 0 51257 0 51265 and pb isotope compositions 206pb 204pb 18 87 18 88 207pb 204pb 15 65 15 67 and 208pb 204pb 38 94 38 98 are homogeneous the western group rhyolites have 18o zircon overlapping mantle values 5 7 0 2 whereas eastern group rhyolites are enriched in 18o by 0 5 consistent with a tendency to lower end values by contrast western group rhyolites have markedly more radiogenic 87sr 86sr ratios 0 7065 0 7091 compared to those of the eastern group 0 7059 0 7065 the presence of angular granitic xenoliths and a correlation between hydration based on loss on ignition data and 87sr 86sr in the western lavas however indicates that sr was added during the eruption or post eruption alteration isotope constraints preclude the possibility that the rhyolite magmas formed by partial melting of any known regional crystalline basement rocks basalts and andesites erupted in the periphery of the acigol field are characterised by 87sr 86sr ratios between 0 7040 and 0 7053 143nd 144nd 0 51259 0 51300 206pb 204pb 18 85 18 87 207pb 204pb 15 646 15 655 208pb 204pb 38 90 38 97 the isotopic and trace element data favour an origin of the rhyolites by mixing of basaltic andesitic magmas with minor amounts of crustal melts and followed by extensive fractional crystallization

seismic characteristics and seismic hazard assessment source region of the 2015 nepal earthquake mw 7 8 in central himalaya seismicity and seismic characteristics like b value fractal dimension energy release and recurrence period are assessed for the region 80 e 89 e and 26 n 31 n which includes the 2015 large nepal earthquake mw 7 8 in central himalaya the international seismological centre isc catalogue of earthquakes with mb 3 8 for the period august 1964 january 2013 are used the b values are estimated using the maximum likelihood and least square methods the fractal dimension is estimated using the correlation integral method the events are also used for estimating radiated energy in the region the probability of occurrence of moderate earthquakes mb 5 0 using isc data and mw 6 0 using usgs data for the period 1964 2015 during a specified interval of time is estimated on the basis of three probabilistic models namely weibull gamma and lognormal the model parameters are estimated by the maximum likelihood estimates it is found that there is a 99 probability for occurrence of at least one earthquake mb 5 0 in this region in a time window of 2 3 years from the year 2013 and in 20 30 years for an earthquake mw 6 0 from the year 2015 the b value maps identified variable stressed zones and the fractal dimension maps fractal characteristics of the active fault zones the energy release map identified the zones of higher and lower energy release the percent probability maps prepared using the poisson distribution identify the zones of higher and lower probability earthquakes and thus indicate the areas of future probable earthquakes

the reset project constructing a european tephra lattice for refined synchronisation of environmental and archaeological events during the last c 100 ka this paper introduces the aims and scope of the reset project response of humans to abrupt environmental transitions a programme of research funded by the natural environment research council uk between 2008 and 2013 it also provides the context and rationale for papers included in a special volume of quaternary science reviews that report some of the project s findings reset examined the chronological and correlation methods employed to establish causal links between the timing of abrupt environmental transitions aets on the one hand and of human dispersal and development on the other with a focus on the middle and upper palaeolithic periods the period of interest is the last glacial cycle and the early holocene c 100 8 ka during which time a number of pronounced aets occurred a long running topic of debate is the degree to which human history in europe and the mediterranean region during the palaeolithic was shaped by these aets but this has proved difficult to assess because of poor dating control in an attempt to move the science forward reset examined the potential that tephra isochrons and in particular non visible ash layers cryptotephras might offer for synchronising palaeo records with a greater degree of finesse new tephrostratigraphical data generated by the project augment previously established tephra frameworks for the region and underpin a more evolved tephra lattice that links palaeo records between greenland the european mainland sub marine sequences in the mediterranean and north africa the paper also outlines the significance of other contributions to this special volume collectively these illustrate how the lattice was constructed how it links with cognate tephra research in europe and elsewhere and how the evidence of tephra isochrons is beginning to challenge long held views about the impacts of environmental change on humans during the palaeolithic

b values of shallow earthquakes in taiwan abstract in taiwan the b values of earthquakes with focal depths of less than 35 km are smaller offshore than on land on land except for the coastal range the b value correlates to the degree of metamorphism of rocks which decreases inland from east to west small b values appear at the leading edge of the subducting slab of the philippine sea plate that plunges underneath northern taiwan possibly indicating high stress due to a bending of the slab large b values in an area including the volcano groups in northern taiwan may be due to the remnant geothermal effect after past volcanic activities besides small b values on land are mainly associated with low bouguer gravity anomalies offshore small b values are related to high bouguer gravity anomalies particularly in regions with a large gravity gradient

seismicity of the eastern mediterranean region perspective from the sinai subplate we conducted a comprehensive study of the seismicity of the eastern mediterranean and examined its relation to the regional plate tectonics based on various published catalogs we have constructed a new list of ml 4 earthquakes which were recorded during the years 1900 1991 and represents most of the seismic moment released in the area over this period b values are 1 02 1 0 and 1 07 for the whole sinai subplate the dead sea transform and the cypriot arc respectively seismic efficiency of the dead sea transform is very low about 7 stressing the role of aseismic deformation in that plate border most of the major and moderate events ml 5 occur in belts associated with the geologically documented borders of the sinai subplate the cypriot convergent arc in the north the dead sea transform in the east and the rift of suez in the southwest the latter like the gulf of eilat aqaba was considered aseismic during the first half of the century the northwestern border however could not be delineated low level activity appears within the subplate especially north of latitude 32 n reflecting the breakdown of this part of sinai as it approaches the cypriot convergence zone though most of the seismic moments tend to concentrate along the subplate borders some moderate activity spreads out in wide belts which reflect the complexity of deformation accompanying motion along the subplate borders

variable spatio temporal clustering of microseismicity in the hellenic subduction zone as possible indicator for fluid migration abstract this study investigates the variability of spatio temporal microseismicity clustering and the occurrence of mutual triggering of events along the subduction interface in south eastern aegean as indication for fluid flow along and above the plate interface we quantify spatial temporal and spatio temporal microseismicity clustering from the outer to the inner forearc and at intermediate depths waveform similarity indicates a decreasing of spatially clustered events from the outer and central towards the inner forearc and at intermediate depths highly similar events cross correlation 0 9 used as proxy for spatial clustering decrease from the outer 30 2 and central forearc 34 9 towards the inner forearc 20 5 and at intermediate depth 6 9 such highly similar events show increasing median inter event times from the outer and central towards the inner forearc and at intermediate depth 0 35 0 34 16 45 and 70 days respectively the epidemic type aftershock sequences etas model employed to investigate microseismicity temporal clustering indicates an increase of the percentage of independent events from the outer 32 and central 46 forearc to the inner forearc 93 and at intermediate depth 93 hence etas results suggest that mutual triggering of events is significant in the outer and central forearc and it is almost absent in the inner forearc and at intermediate depths autocorrelation analysis investigating spatio temporal clustering shows the tendency of earthquakes to occur close in space and time in the outer and central forearc while in the inner forearc and especially at intermediate depth earthquakes are more homogeneously and randomly distributed combining the results from spatial temporal and spatio temporal analysis we suggest that the different spatio temporal patterns hint at systematic variations in the presence of migrating fluids on active faults close to failure triggering of seismicity is significant in the outer and central forearc indicating fluid flow from the subduction interface and it is diminishing towards the inner forearc at intermediate depths the nearly complete absence of mutual triggering of earthquakes indicates that there is little evidence for migration of fluids on active faults close to failure because intermediate depth seismicity in the hellenic subduction zone occurs at p t conditions where dehydration reactions are expected fluids released by dehydration reactions within the slab are very likely migrating directly into the overlying mantle without triggering earthquakes

attenuation of s waves in the lithosphere of the sea of crete according to obs observations five obs were installed in the sea of crete in 1987 during a period of nine days 430 local earthquakes were recorded hypocentres were determined for 85 microearthquakes a correlation between magnitude ml and duration of seismic events on the records of the ocean bottom seismographs obs was found from data of 14 shocks recorded simultaneously by obs and some land based greek stations a magnitude frequency relationship for earthquakes recorded by obs was obtained in the magnitude range ml 2 4 amplitude curves describing the attenuation of body waves in the lithosphere of the sea of crete were compiled assessment of quality factor qs was made by comparison of empirical and theoretical amplitude curves the values of qs for the lithosphere of the sea of crete were calculated and found equal to 200 300 low values of qs and consequently strong attenuation of s waves in the lithosphere of the sea of crete could be explained by extension of the lithosphere accompanied by its partial contamination with melted magma

the seismic parameter b of the frequency magnitude relation and its association with the geological zones in the area of greece abstract the parameter b of the frequency magnitude relation has been accurately calculated for each of the 21 seismic zones into which the aegean and surrounding area 34 n 43 n 18 e 30 e has been divided on the basis of several seismotectonic criteria these 21 seismic zones have been geographically separated into three a b c groups regions according to the values of the parameter b the outer region a is characterized by a relatively high value 1 03 the middle region b by an intermediate value 0 84 and the innermost region c by a low value 0 60 the boundaries of these three groups of zones almost coincide with the boundaries of well known geological zones this observation is interpreted in terms of mechanical heterogeneity of the material and of structural and stress conditions in the area

scale in tephrostratigraphic correlation an example from turkish pleistocene archaeological sites issues of scale are persistent but rarely made explicit in tephrostratigraphy eruption magnitude the nature of available outcrop and the resolution and type of data available define the scale of any proposed correlation different scales require different approaches to demonstrate or more accurately to estimate the likelihood of correlation among two or more deposits this is emphasized through a probabilistic approach to the correlation of proximal and distal tephra deposits associated with lower and middle paleolithic archaeological sites from central turkey through the use of discriminant analyses and multiple analyses of variance

seismic faults in the aegean area abstract reliable fault plane solutions of shallow earthquakes and information on surface fault traces in combination with other seismic geomorphological and geological information have been used to determine the orientation and other properties of the seismic faults in the aegean and surrounding area thrust faults having an about nw se strike occur in the outer seismic zone along western albania westernmost part of mainland of greece ionian sea south of crete south of rhodes the inner part of the area is dominated by strike slip and normal faulting strike slip with an about ne sw slip direction occurs in the inner part of the hellenic arc along the line peloponnesus cyclades dodecanese southwest turkey as well as along a zone which is associated with the northern aegean trough and the northwesternmost part of anatolia all other regions in the inner part of the area are characterized by normal faulting the slip direction of the normal faults has an about sw ne direction in crete n38 e and an about e w direction n81 e in a zone which trends n s in eastern albania and its extension to western mainland of greece in all other regions central greece southern yugoslavia and bulgaria western turkey the slip of the normal faults has an about n s direction

the southern tyrrhenian subduction zone deep geometry magmatism and plio pleistocene evolution abstract we report on a high resolution vp vp vs and qp model of the southern tyrrhenian subduction zone obtained by the inversion of p and s wave arrival times and t values from intraslab seismicity the arcuate shape of the southern apennines calabrian arc sicilian maghrebides is perfectly mirrored by two rather continuous low and high vp bands lying beneath the belt system at ca 25 and 100 km respectively between 100 and 300 km two independent high vp slabs lie beneath the neapolitan region and the southern tyrrhenian sea separated by unperturbed mantle we suggest that the ca 150 km wide slab window beneath the southern apennines opened after a tear occurring within a composite subduction system formed by the apulian continental lithosphere and the ionian oceanic slab the abrupt slab rupture induced ultrafast southeastward retreat of the ionian slab and the 19 cm yr spreading of the back arc oceanic marsili basin between ca 2 1 and 1 6 ma ago the 25 km low vp zone beneath the arc denotes continental upper crustal rocks below the chain its striking continuity requires a unique orogenic wedge at 25 km depth below the southern apennines the calabrian arc and the sicilian maghrebides the alternative explanation would imply the ubiquitous occurrence of autochthonous lower plate rocks at 25 km depth i e a puzzling autochthonous continental calabria the ionian slab beneath calabria shows high vp high qp and low vp vs anomalies typical of old oceanic lithosphere intermediate depth seismicity is concentrated within its thin oceanic crust suggesting the occurrence of vigorous metamorphism the slab dehydration promotes the melting of the overlying mantle as testified by high vp vs and low qp anomalies between the slab and the aeolian magmatic arc

the role of cryptotephra in refining the chronology of late pleistocene human evolution and cultural change in north africa abstract sites in north africa hold key information for dating the presence of homo sapiens and the distribution of middle stone age msa middle palaeolithic mp and later stone age lsa cultural activity in the late pleistocene here we present new and review recently published tephrochronological evidence for five cave sites in north africa with long msa mp and lsa cultural sequences four tephra horizons have been identified at the haua fteah cyrenaica libya they include cryptotephra evidence for the campanian ignimbrite ci eruption dating to 39 ka that allows correlation with other palaeolithic sequences in the eastern mediterranean and as far north as russia cryptotephra have also been recorded from the moroccan sites of taforalt rhafas and dar es soltane 1 at taforalt the geochemical composition suggests a provenance in the azores while examples from sodmein egypt appear to derive from central anatolia and another unknown source in these latter examples chemical compositional data from relevant proximal volcanic centres is currently lacking so the identification of tephra in layers of known age and cultural association provides the first reliable age determinations for distal volcanic events and their geographical extent the future potential for tephrochronological research in north africa is also discussed

occurrence patterns of large earthquakes in the seismic zones along the hellenic arc occurrence patterns of large shallow and intermediate depth earthquakes in the seismic zones along the hellenic arc have been investigated it is shown that throughout this active region the earthquakes tend to occur in a rather systematic manner at each time period earthquakes occur within a discrete activated segment of the arc these occurrence patterns are considered to offer an insight into identifying where large earthquakes are expected to occur in the future

seismicity of the hellenic subduction zone in the area of western and central crete observed by temporary local seismic networks temporary local seismic networks were installed in western crete in central crete and on the island gavdos south of western crete respectively in order to image shallow seismically active zones of the hellenic subduction zone more than 4000 events in the magnitude range between 0 5 and 4 8 were detected and localized the resulting three dimensional hypocenter distribution allows the localization of seismically active zones in the area of western and central crete from the mediterranean ridge to the cretan sea furthermore a three dimensional structural model of the studied region was compiled based on results of wide angle seismics surface wave analysis and receiver function studies the comparison of the hypocenter distribution and the structure has allowed intraplate and interplate seismicity to be distinguished high interplate seismicity along the interface between the subducting african lithosphere and the aegean lithosphere was found south of western crete where the interface is located at about 20 to 40 km depth an offset between the southern border of the aegean lithosphere and the southern border of active interplate seismicity is observed in the area of crete the offset varies laterally along the hellenic arc between about 50 and 70 km a southwards dipping zone of high seismicity within the aegean lithosphere is found south of central crete in the region of the ptolemy trench it reaches from the interface between the plates at about 30 km depth towards the surface in comparison the aegean lithosphere south of western crete is seismically much less active including the region of the ionian trench intraplate seismicity within the aegean plate beneath crete and north of crete is confined to the upper about 20 km between 20 and 40 km depth beneath crete the aegean lithosphere appears to be seismically inactive in western crete the southern and western borders of this aseismic zone correlate strongly with the coastline of crete

paleogeographic conditions in the western pelagonian margin in greece during the initial rifting of the continental area the uppermost paleozoic metaclastic sequences of the pelagonian zone in northern greece are connected to the western margin of the zone they represent paleogeographic conditions of a deltaic environment and continental slope which are related to the separation of the paleozoic continent and the initial rifting in the western ophiolite belt in greece the metaclastic sequences define the western external boundary of the pelagonian zone and are used to find the continuation of this boundary in the sporades and oinouses islands in the aegean sea in order to help answer the question of the connection between the hellenides and the taurides in turkey

correlation of the rockland ash bed a 400 000 year old stratigraphic marker in northern california and western nevada and implications for middle pleistocene paleogeography of central california abstract outcrops of an ash bed at several localities in northern california and western nevada belong to a single air fall ash layer the informally named rockland ash bed dated at about 400 000 yr b p the informal rockland pumice tuff breccia a thick coarse compound tephra deposit southwest of lassen peak in northeastern california is the near source equivalent of the rockland ash bed relations between initial thickness of the rockland ash bed and distances to eruptive source suggest that the eruption was at least as great as that of the mazama ash from crater lake oregon identification of the rockland tephra allows temporal correlation of associated middle pleistocene strata of diverse facies in separate depositional basins specifically marine littoral estuarine and fluvial strata of the hookton and type merced formations correlate with fluvial strata of the santa clara formation and unnamed alluvium of willits valley and the hollister area in northwestern and west central california and with lacustrine beds of mohawk valley fluvial deposits of the red bluff formation of the eastern sacramento valley and fluvial and glaciofluvial deposits of fales hot spring carson city and washoe valley areas in northeastern california and western nevada stratigraphic relations of the rockland ash bed and older tephra layers in the great valley and near san francisco suggest that the southern great valley emerged above sea level about 2 my ago that its southerly outlet to the ocean was closed sometime after about 2 my ago and that drainage from the great valley to the ocean was established near the present northerly outlet in the vicinity of san francisco bay about 0 6 my ago

distal record of multi sourced tephra in onepoto basin auckland new zealand implications for volcanic chronology frequency and hazards we have documented 80 tephra beds dating from ca 9 5 to 50 ka contained within continuously deposited palaeolake sediments from onepoto basin a volcanic explosion crater in auckland new zealand the known sources for distal 190 km from vent tephra include the rhyolitic taupo volcanic centre 4 and okataina volcanic centre 14 and the andesitic taranaki volcano 40 and tongariro volcanic centre 3 the record provides evidence for four new events between ca 50 and 28 ka mangaone subgroup suggesting okataina was more active than previously known the tephra record also greatly extends the known northern dispersal of other mangaone subgroup tephra ten rhyolitic tephra pre date the rotoehu eruption ca 50 ka and some are chemically dissimilar to post 50 ka rhyolites some of these older tephra were produced by large magnitude events however their source remains uncertain eight tephra from the local basaltic auckland volcanic field avf are also identified interpolation of sedimentation rates allow us to estimate the timing of 12 major explosive eruptions from taranaki volcano in the 27 5 9 5 ka period in addition 28 older events are recognised the tephra are trachytic to rhyolitic in composition all have high k2o contents 3 wt and there are no temporal trends this contrasts with the proximal lava record that shows a trend of increasing k2o with time by combining the onepoto tephra record with that of the previously documented pukaki crater 15 avf basaltic fall events are constrained at 34 6 30 9 29 6 29 6 25 7 25 2 24 2 23 8 19 4 19 4 15 8 and 14 5 ka and three pre 50 ka events this provides some of the best age constraints for the avf and the only reliable data for hazard recurrence calculations the minimum event frequency of both distal and local fall events can be estimated and demonstrates the auckland city region is frequently impacted by ash fall from many volcanoes

the seismic b value and its correlation with bouguer gravity anomaly over the shillong plateau area tectonic implications abstract clues to the understanding of intra and inter plate variations in strength or stress state of the crust can be achieved through different lines of evidence and their mutual relationships among these parameters bouguer gravity anomalies and seismic b values have been widely accepted over several decades for evaluating the crustal character and stress regime the present study attempts a multivariate analysis for the shillong plateau using the bouguer gravity anomaly and the earthquake database and establishes a causal relationship between these parameters four seismic zones zones i iv with widely varying b values are delineated and an excellent correlation between the seismic b value and the bouguer gravity anomaly has been established for the plateau low b values characterize the southwestern part zone iv and a zone zone iii of intermediate b values separates the eastern and western parts of the plateau zones i and ii which have high b values positive bouguer anomaly values as high as 40 mgal a steep gradient in the bouguer anomaly map and low b values in the southwestern part of the plateau are interpreted as indicating a thinner crustal root uplifted moho and higher concentration of stress in comparison the negative bouguer anomaly values flat regional gradient in the bouguer anomaly map and intermediate to high b values in the northern part of the plateau are consistent with a comparatively thicker crustal root and lower concentration of stress with intermittent dissipation of energy through earthquake shocks further depth wise variation in the b value for different seismic zones delineated under this study allowed an appreciation of intra plateau variation in crustal thickness from 30 km in its southern part to 38 km in the northern part the high b values associated with the depth coinciding with lower crust indicate that the shillong plateau is supported by a strong lithosphere

b values of two tectonic parts in the circum pacific belt two different data sets have been applied to compute theb parameter of the magnitude frequency relation for two different areas in the circum pacific belt these areas are a south america middle america and mexico b all the remaining island arcs of the circum pacific belt starting from alaska and the aleutian islands and proceeding southeastwards the first data set spreads over 77 years while the second one covers a 90 year period in both cases the results clearly showed that theb values are lower in the first of the above mentioned areas while respectively higher in the second this is due to the tectonic conditions in these areas as estimated during the present work

discovery of cryptotephra at middle upper paleolithic sites arma veirana and riparo bombrini italy a new link for broader geographic correlations

an alternative approach to probabilistic seismic hazard analysis in the aegean region using monte carlo simulation abstract the aegean is the most seismically active and tectonically complex region in europe damaging earthquakes have occurred here throughout recorded history often resulting in considerable loss of life the monte carlo method of probabilistic seismic hazard analysis psha is used to determine the level of ground motion likely to be exceeded in a given time period multiple random simulations of seismicity are generated to calculate directly the ground motion for a given site within the seismic hazard analysis we explore the impact of different seismic source models incorporating both uniform zones and distributed seismicity a new simplified seismic source model derived from seismotectonic interpretation is presented for the aegean region this is combined into the epistemic uncertainty analysis alongside existing source models for the region and models derived by a k means cluster analysis approach seismic source models derived using the k means approach offer a degree of objectivity and reproducibility into the otherwise subjective approach of delineating seismic sources using expert judgment similar review and analysis is undertaken for the selection of peak ground acceleration pga attenuation models incorporating into the epistemic analysis greek specific models european models and a next generation attenuation model hazard maps for pga on a rock site with a 10 probability of being exceeded in 50 years are produced and different source and attenuation models are compared these indicate that greek specific attenuation models with their smaller aleatory variability terms produce lower pga hazard whilst recent european models and next generation attenuation nga model produce similar results the monte carlo method is extended further to assimilate epistemic uncertainty into the hazard calculation thus integrating across several appropriate source and pga attenuation models site condition and fault type are also integrated into the hazard mapping calculations these hazard maps are in general agreement with previous maps for the aegean recognising the highest hazard in the ionian islands gulf of corinth and hellenic arc peak ground accelerations for some sites in these regions reach as high as 500 600 cm s 2 using european nga attenuation models and 400 500 cm s 2 using greek attenuation models

spatio temporal microseismicity clustering in the cretan region abstract spatio temporal clustering of microseismicity in the central forearc of the hellenic subduction zone in the area of crete is investigated data for this study were gathered by temporary short period networks which were installed on the islands of crete and gavdos between 1996 and 2004 the similarity of waveforms is quantified systematically to identify clusters of microseismicity waveform similarities are calculated using an adaptive time window containing both the p and s wave onsets the cluster detection is performed by applying a single linkage approach clusters are found in the interplate seismicity as well as in the intraplate seismicity of the continental crust in the region of the transtensional ptolemy structure the majority of the clusters are off the southern coast of crete in a region of elevated intraplate microseismic activity within the aegean plate clusters in the gavdos region are located at depths compatible with the plate interface while cluster activity in the region of the ptolemy trench is distributed along a nearly vertical structure throughout the crust extending down to the plate interface most clusters show swarm like behaviour with seismic activity confined to only a few hours or days without a dominant earthquake and with a power law distribution of the interevent times for the largest cluster precise relocations of the events using travel time differences of p and s waves derived from waveform cross correlations reveal migration of the hypocenters this cluster is located in the region of the ptolemy trench and migration occurs along the strike of the trench at 500 m day relocated hypocenters as well as subtle differences in the waveforms suggest an offset between the hypocenters and thus the activation of distinct patches on the rupture surface the observed microseismicity patterns may be related to fluids being transported along the plate interface and escaping towards the surface in zones of crustal weakness ptolemy structure triggering swarm like cluster activity along its way

building a tephrostratigraphic framework for the paleolithic of central anatolia turkey the central anatolian volcanic province cavp in turkey preserves widespread deposits of quaternary tephra presently associated with a small but growing number of paleolithic archaeological sites we use multivariate analyses of the abundances of a suite of nine major and minor element oxides determined by electron probe microanalysis from these data we construct a classificatory model for correlating distal tephra to one of five volcanic edifices or eruptive phases within the cavp application of this model to distal deposits of primary tephra fall and reworked tuffaceous sediments from the archaeological sites of korkuyu and kaletepe deresi 3 indicates late to possibly early pleistocene ages for the artifact assemblages there and provides a fundamental tephrostratigraphic framework to examine spatial and temporal variation in hominin behavior comparable to that of other regions such as eastern africa

anomalous sulfur isotopes trace volatile pathways in magmatic arcs the cycle of sulfur an important volatile in earth9s crust is the driver of many significant processes such as biological evolution climate change and the formation of ore deposits this study investigates the ancient cycle of volatiles by tracing the indelible signal of anomalous sulfur isotopes expressed as 33 s 0 to illuminate the pathway of sulfur recycling through magmatic arcs we selected the ca 2 0 ga glenburgh gold deposit in the glenburgh magmatic arc of western australia as a natural laboratory for this study high precision multiple sulfur isotope analyses of samples from the glenburgh gold deposit and surrounding granitoid rocks yield the largest known sulfur isotope anomalies 33 s up to 0 82 in rocks 2 33 ga globally these data indicate that sulfur and possibly gold originated from multiple geochemical reservoirs in sedimentary rocks subducted beneath the magmatic arc one of which is 2 33 ga multiple sulfur isotope data are able to clarify a process that is cryptic to most other currently available data sets showing that the cycling of volatiles and metals in arc settings occurs on very large scales from the atmosphere hydrosphere through to the lithosphere during crustal generation

long term earthquake prediction in the hellenic trench arc system abstract data concerning seismic sequences which have occurred in the hellenic trench sedimentary arc tectonic system have been used to investigate the time variation of the difference d 1 between the magnitude of the main shock and that of the largest aftershock the data are well fitted by an harmonic function with period of 29 years for both the western seismic zone ionian islands s peloponnesus w crete and the south southeastern zone crete karpathos rhodos it has been observed that the largest earthquakes in both zones are associated with low values of the d 1 t function based on these observations we suggest that a strong seismic activity with earthquakes of m 7 0 will break out soon in the hellenic trench arc system the largest of these earthquakes are expected between 1983 and 1987 a quiescence in seismicity which started fifteen years ago in the southern part of the western zone also indicates the generation of a very strong earthquake in this area during the next five years or so

the early to mid holocene marine tephrostratigraphic record in the nisyros yali kos volcanic center se aegean sea abstract the kos nisyros yali volcanic region is one of the centers in the south aegean volcanic arc to exhibit holocene volcanic activity with poorly dated thin tephra layers on yali associated with neolithic artifacts this paper helps to resolve the age and character of early to mid holocene volcanism in the south aegean sea it presents the lithostratigraphic record of seven newly recovered cores from this region at the se termination of the south aegean volcanic arc the cores were scanned for magnetic susceptibility split logged and sampled at one centimeter resolution for carbonate content selected intervals were analyzed for grain size organic carbon content and feldspar content by xrd in order to identify lithostratigraphic levels with enhanced volcanic minerals subsequently textural and electron microprobe analyses of volcanic glass shards and pumice fragments were carried out on 20 samples chronology was inferred from the upper and lower limits of the s1 sapropel and from five ams 14c dates on foraminifera in several cores in the s1 interval mixed volcanic glass types that compositionally correlate with the nisyros lower and upper pumice yali pumices and kpt suggest that the volcanic glass is reworked from previous deposits and transported by turbidity currents cores from deep water northeast and northwest of yali have a single population of tephra at two or more horizons within s1 that geochemically resembles holocene yali 4 pumice on land these beds likely represent air fall ash that was dispersed at least 10 km from yali with ages of 8 and 10 ka moreover we report two or more tephra layers within s1 from the kalymnos basin that are not reworked and geochemically resemble santorini tephra this study thus confirms the occurrence of small early holocene eruptions at yali and provides possible evidence for early holocene eruptions at santorini

further seismic properties of a spring block earthquake model summary within the context of self organized critical systems olami et al ofc 1992 proposed a spring block earthquake model this model is non conservative and reproduces some seismic properties such as the gutenberg richter law for the size distribution of earthquakes in this paper we study further seismic properties of the ofc model and we find the stair shaped curves of the cumulative seismicity we also find that in the long term these curves have a characteristic straight line envelope of constant slope that works as an attractor of the cumulative seismicity and that these slopes depend on the system size and cannot be arbitrarily large finally we report that in the ofc model the recurrence time distribution for large events follows a log normal behaviour for some non conservation levels

problems with radiocarbon dating the middle to upper palaeolithic transition in italy abstract radiocarbon dating of material from late pleistocene archaeological sites is challenging small amounts of modern 14c labelled contamination will significantly affect the reliability of dates from the period producing erroneous results recent developments in sample pre treatment chemistry have shown that problems in reliable age determination during this period are surmountable in this paper we provide an example of one such case from the middle to upper palaeolithic transitional site of the grotta di fumane in northern italy we ams dated two fractions of the same charcoal samples derived from a series of superimposed mousterian aurignacian and gravettian levels excavated at the site one fraction was treated using the routine acid base acid aba method the other with the more rigorous acid base oxidation stepped combustion abox sc method the latter method produced consistently older and almost certainly more reliable results the eruption of the known age campanian ignimbrite from the phlegrean fields near present day naples at 39 3 ka yr bp seals ulluzzian and proto aurignacian levels in the south of italy equivalent cultural levels are present at fumane and the results obtained with the abox sc methods are consistent with the ages inferred for sites in the south of italy based on the presence of the campanian ignimbrite new results from a sample found beneath the campanian ignimbrite at the russian site of kostenki obtained using both the aba and abox sc methods are also presented they support the conclusion reached at fumane by demonstrating that in many cases the abox sc treatment effectively removes contamination where the aba treatment does not the results of the work offer a sobering examination of the problems inherent in the current radiocarbon database relating to the period and highlight the dangers of an uncritical use of the corpus of 14c results obtained over the last few decades based on our results we predict that more than 70 of the 53 previously available determinations from fumane are erroneously young a way forward is suggested using these improved chemical preparation methods applying analytical methods to characterise the material dated and testing existing site chronologies to establish which previous determinations are liable to be inaccurate

re evaluation and extension of the marine isotope stage 5 tephrostratigraphy of the faroe islands region the cryptotephra record previous studies of marine sequences from the faroe islands region have identified a series of coarse grained tephra horizons deposited during marine isotope stage mis 5 here we reassess the mis

the upper and lower nisyros pumices revisions to the mediterranean tephrostratigraphic record based on micron beam glass geochemistry abstract the greek island of nisyros is the source of tephra found in distal settings throughout the aegean in this contribution we define geochemical fingerprints for the lower and upper pumice eruptions of nisyros based on micron beam major empa and trace la icp ms element data these two eruptions are compositionally distinct from each other the high phenocryst content of proximal lower and upper pumice tephra means that the differences between the two magmas are masked in whole rock analyses we demonstrate that all previous reports of distal marine and continental tephras correspond to the younger upper pumice not the older lower pumice this has important implications for the marine tephrochronology of the mediterranean and for the age of the upper and lower pumice eruptions we suggest an age of at least 47 ka for the upper pumice and an older unconstrained age for the lower pumice

developing a robust tephrochronological framework for late quaternary marine records in the southern adriatic sea new data from core station sa03 11 tephra layers are assuming an increasingly important role in the dating and correlation of late quaternary marine sequences here we demonstrate their potential by reporting a new study of the sediment sequence of marine core sa03 11 recovered from the southern adriatic sea which spans the last c 39 ka a total of 28 discrete tephra layers are reported from this sequence 10 of which are visible in the core and a further 18 are non visible cryptotephra layers these have been analysed using more than 1400 wds epma measurements of glass chemistry and results have been compared with published chemical measurements obtained from relevant proximal and distal sites which preserve eruptive material dating to within the same time interval the data show that a high proportion of the layers originate from the campi flegrei volcanic field but more distinctive layers are sourced from vesuvius the aeolian islands and vulcano and these provide key marker horizons the results show that the sequence extends in time to the campanian ignimbrite at the base that a number of the layers have robust age estimates that permit a better constrained age depth model to be constructed for the sequence and that the potential exists for importing terrestrially based age estimates into marine contexts thereby circumventing problems of incorporating reservoir uncertainties associated with marine radiocarbon dates the wds epma dataset generated here also provides important new data that constrain key late quaternary tephra layers in the central mediterranean region

a new and less destructive laboratory procedure for the physical separation of distal glass tephra shards from sediments abstract tephrochronology a key tool in the correlation of quaternary sequences relies on the extraction of tephra shards from sediments for visual identification and high precision geochemical comparison a prerequisite for the reliable correlation of tephra layers is that the geochemical composition of glass shards remains unaltered by natural processes e g chemical exchange in the sedimentary environment and or by laboratory analytical procedures however natural glasses particularly when in the form of small shards with a high surface to volume ratio are prone to chemical alteration in both acidic and basic environments current techniques for the extraction of distal tephra from sediments involve the cleaning of samples in precisely such environments and at elevated temperatures the acid phase of the cleaning process risks alteration of the geochemical signature of the shards while the basic phase leads to considerable sample loss through dissolution of the silica network here we illustrate the degree of alteration and loss to which distal tephras may be prone and introduce a less destructive procedure for their extraction this method is based on stepped heavy liquid flotation and which results in samples of sufficient quality for analysis while preserving their geochemical integrity in trials this method out performed chemical extraction procedures in terms of the number of shards recovered and has resulted in the detection of new tephra layers with low shard concentrations the implications of this study are highly significant because i the current database of distal tephra records and their corresponding geochemical signatures may require refinement and ii the record of distal tephras may be incomplete due to sample loss induced by corrosive laboratory procedures it is therefore vital that less corrosive laboratory procedures are developed to make the detection and classification of distal glass tephra more secure

seismicity and tectonics of the red sea and western arabia summary search in a number of seismological sources revealed that in the period 1913 86 some 135 earthquakes 3 m s 6 9 occurred in the red sea and western arabia between latitudes 14 and 27 2 n in the same period 49 earthquakes m s 6 9 and 247 earthquakes m c 4 9 are reported to have occurred in the gulfs of suez and aqaba respectively twenty three historical earthquakes are reported to have been felt in the region with intensities iv ix and a few more with unassigned intensities during the period ad 627 1884 the epicentral distribution of both instrumental and historical data and their characteristics show a general correlation with the regional geology and tectonics sixty per cent of the total energy released from all instrumental earthquakes is released from earthquakes epicentred within the spreading zone concentrations of activity are seen where the spreading zone is intersected by the ne transform faults and where this zone shifts in direction much of the seismicity of this region is of the swarm type and volcanic related both instrumental and historical data show an apparent lower seismicity in the northern red sea region between latitudes 22 and 27 2 n but the whole region is of a noticeable seismic risk that is mostly associated with regional land faults some of which are continuations of the red sea transform faults the instrumental seismicity of the whole region conforms with the relation log n 4 23 0 53m when historical data are considered both datasets conform with the relation log n 4 1 0 47m the b constant correlates with the shield type of environment and seems to increase gradually northwards to attain a value of 0 71 in the gulfs region this may be caused by either heterogeneity in the lithosphere or most probably asymmetry of the regional stress field in the vicinity of latitude 27 5 n or both causes

cryptotephra as a dating and correlation tool in archaeology a new development in archaeological chronology involves the use of far travelled volcanic ash which may form discrete but invisible layers within a site s stratigraphy known as cryptotephra these horizons can provide isochrons for the precise correlation of archaeological records at single moments in time removing or at least significantly reducing temporal uncertainty within inter site comparisons when a tephra can be dated elsewhere its age can be imported between records providing an independent check on other dating methods in use and valuable age estimates for difficult to date sequences the use of cryptotephra layers to date and correlate palaeoenvironmental archives is well established and there exists a wealth of tephra compositional data and regional tephrostratigraphic frameworks from which archaeological cryptotephra studies can benefit greatly existing approaches to finding and analysing cryptotephra are easily adapted to archaeological sequences so long as the often complex nature of archaeological stratigraphies and sediment taphonomy are borne in mind

a continuous 5300 yr holocene cryptotephrostratigraphic record from northern new zealand and implications for tephrochronology and volcanic hazard assessment a continuous 5280 calendar cal yr long cryptotephrostratigraphic record of a peat core from northern new zealand demonstrates that cryptotephra studies can enhance conventional tephra records by extending the known distribution of ash fall and enabling re assessment of volcanic hazards a systematic sampling strategy was used to locate peaks in glass shard concentrations and to determine loci of individual geochemical populations and a palynological method involving spiking samples with lycopodium spores was adapted to facilitate accurate counting of glass shard concentrations using glass shard major element compositions and a core chronology based on eight ams 14c ages and two visible macroscopic tephra layers taupo tephra unit y 1688 1748 cal bp and tuhua tephra 6800 7230 cal bp 2cr age ranges four cryptotephras were correlated with known eruptions whakaipo unit v 2743 2782 cal bp stent unit q 4240 4510 cal bp and unit k 4970 5290 cal bp erupted from taupo volcanic ce

glass geochemistry of pyroclastic deposits from the aeolian islands in the last 50 ka a proximal database for tephrochronology abstract volcanic ash 1000 analyses provides a basis for proximal distal and distal distal tephra correlations tephra deposits from the different aeolian islands are geochemically diverse with some individual eruptions showing diagnostic geochemical heterogeneity recognised both stratigraphically and or spatially major element glass analyses reveal that vulcano 0 21 ka and stromboli 4 13 ka have erupted potassic shoshonitic and k series tephra with broadly overlapping compositions but data presented here demonstrates that their eruptive products can be distinguished using either tio2 contents or their hfse th ratios whilst individual volcanic sources often produce successive tephra deposits with near identical major and minor element compositions through time i e lipari vulcano trace element glass data can help to decipher successive eruptions changes in lree and th concentrations of volcanic glasses erupted spanning approximately the last 50 ka greatly enhance the potential to discriminate successive eruptive units on lipari the new proximal glass database has been used to verify new ionian sea core m25 4 12 and existing distal occurrences of aeolian island derived tephra enabling the reassessments of past ash dispersals finally proximal and distal data have been used to establish an integrated proximal distal eruptive event stratigraphy for the aeolian islands

tephrochronology of the astronomically tuned kc01b deep sea core ionian sea insights into the explosive activity of the central mediterranean area during the last 200 ka abstract we present a major trace and rare earth element characterization of single glass shards from fifteen tephra layers found in the astronomically tuned kc01b deep sea core ionian sea central mediterranean 36 15 25 n 17 34 44 e 3642 m water depth kc01b is considered a reference core for the mediterranean area since it provides a new reliable astronomical tuned timescale for the last 1 112 my lourens 2004 the studied deposits punctuate the marine record in a time span ranging from ca 16 ka to ca 191 ka b p encompassing the climatic zones y x w and v they are related to volcanic activity of the campania plain aeolian islands mt etna and pantelleria island along with major main markers of the central mediterranean area such as y 1 y 5 and x 6 astronomically dated at 16 7 ka 39 1 ka and 110 5 ka respectively the succession contains a number of well preserved deposits which can represent useful inter archive instruments of correlation the campania plain in particular sourced at least nine compositionally homogeneous tephra layers prior to the campanian ignimbrite event the data obtained in this work provide a new detailed analytical reference database for ionian sea tephrochronology and for proximal distal correlation studies they may help to unravel from the marine record the history of poorly known or unknown explosive activity on land since the middle pleistocene along with chemical composition size and dispersal of the products

interpretation of low seismicity in the eastern anatolian collisional zone using geophysical seismicity and aeromagnetic and geological data the eastern anatolia is a continental collisional zone between the arabia eurasia plates and is currently being accompanied by the westward escape of the anatolian crustal block to the west southwest along two major strike slip fault zones the natf and the eatf although these major fault zones have experienced historical earthquakes with moderate to high magnitude notably there is a low seismicity zone on the active eatf between the bitlis and poturge massifs the low seismicity zone is characterized by thinner crustal structure relative to its environs the shallow curie point depth scpd ca 12 14 km in between 39 40 e and 38 5 39 n in the easternmost part of the anatolian plate and moderate to high b values more than 0 7 we consider that the shallow cpd and moderate to high b values in the low seismicity zone characterized by thinner crustal area are closely related with the higher thermal structure of the crust which most probably resulted from crust hot asthenospheric mantle interactions

new chronological constraints for middle palaeolithic mis 6 5 3 cave sequences in eastern transylvania romania abstract the middle to upper palaeolithic transition is one of the crucial periods of change in the prehistory of europe due to the full emergence continent wide of modern human lithic technologies and detrimental of neanderthal survival knowledge about the transition is growing however the evidence for cultural and technological developments for the middle palaeolithic in the carpathian lower danube basin is still rather sparse here we discuss latest findings arising from a chronological investigation of middle palaeolithic assemblages within the varghis karst eastern transylvania romania combining our first chronological results with information from previous excavations we can distinguish two main stages of habitation albeit middle palaeolithic lithics and faunal remains appear scattered throughout the investigated profile within the abri 122 rock shelter in order to augment the typological cultural considerations we applied direct radiocarbon dating on bones and charcoal from within the occupation layers radiocarbon dating of bones suggests that the middle palaeolithic sequence is older than the upper dating limit of the method whereas direct luminescence ages on the lowermost productive horizon and immediately above it indicate surprisingly old ages of ca 106 141 ka osl optically stimulated or 99 174 ka irsl infrared stimulated multiple protocol dating of charcoal found within the two habitation layers produced ages 38 14 c ka bp also suggesting that the lowermost lithic rich horizon pertains to the middle palaeolithic industries overall the recovered lithics currently forming one of the most significant collections for romania are fully consistent with two main habitation phases connected to middle palaeolithic cultural affinities the occurrence of a volcanic ash layer within ursului cave and originating from the ciomadul volcanic complex carpathians is first reported here recently dated to 43 50 ka it might represent an important marker horizon providing that it is identified within other palaeolithic cave assemblages