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

acoustic backscatter measurements from littoral seabeds at shallow grazing angles at 4 and 8 khz direct measurement of acoustic scattering from the seabed at shallow grazing angles and low kilohertz frequencies presents a considerable challenge in littoral waters specifically returns from the air water interface typically contaminate the signals of interest to address this issue drdc atlantic has developed a sea going research system for measuring acoustic scatter from the seabed in shallow water environs the system known as the wideband sonar wbs consists of a parametric array transmitter and a superdirective receiver in this paper backscatter measurements obtained with the wbs at two sandy shallow water sites off north america s atlantic coast are presented data were collected at 4 and 8 khz at grazing angles from 3 15 the backscattering strength is similar at both sites and below about 8 it appears to be independent of frequency within the statistical accuracy of the data the measurements show reasonable agreement with model estimates of backscatter from sandy sediments a smal

the cryptotephra record of the marine isotope stage 12 to 10 interval 460 335 ka at tenaghi philippon greece exploring chronological markers for the middle pleistocene of the mediterranean region abstract precise chronologies that allow direct correlation of paleoclimate archives are a prerequisite for deciphering the spatiotemporal characteristics of short term climate variability such chronologies can be established through the analysis of tephra layers that are preserved in the respective sedimentary archives here we explore the yet untapped tephrochronological potential of the eastern mediterranean region for the middle pleistocene specifically for the interval spanning marine isotope stages mis 12 10 460 335 ka high resolution cryptotephra analysis was carried out on peat cores spanning the mis 12 10 interval that have been recovered from the iconic climate archive of tenaghi philippon ne greece eighteen primary cryptotephras were identified and major and trace element analyses of single glass shards from all cryptotephras were performed in order to correlate them with their eruptive sources the results suggest origins from both italian and aegean arc volcanoes specifically one cryptotephra layer could be firmly correlated with the cape therma 1 eruption from santorini which makes it the first distal tephra finding for this eruptive event while eight further cryptotephras could be tentatively correlated with their volcanic or even eruptive sources the provenance of another nine cryptotephras as yet remains unknown the relatively large number of cryptotephras that could not be assigned to specific volcanic sources and eruptive events reflects the still considerable knowledge gap regarding the geochronology and geochemistry of proximal tephra deposits from the middle pleistocene of the central and eastern mediterranean regions due to the lack of well dated middle pleistocene eruptions we provide age estimates for all cryptotephra layers identified in the mis 12 10 interval at tenaghi philippon based on high resolution pollen data from the same cores while eight of the identified cryptotephras were deposited within mis 12 438 427 ka one cryptotephra was deposited at the onset of mis 11 419 ka five cryptotephras during the younger part of mis 11 391 367 ka and four cryptotephras during mis 10 359 336 ka the high number of cryptotephras from multiple sources as recorded in the mis 12 10 interval at tenaghi philippon highlights the key role of this archive for linking tephrostratigraphic lattices for the middle pleistocene of the central and eastern mediterranean regions

revised chronology of the sulmona lacustrine succession central italy we present new stratigraphic palaeomagnetic 87sr 86sr and 40ar 39ar data from a lacustrine succession of the sulmona basin central italy which according to an early study included six unconformity bounded lacustrine units from sul6 oldest to sul1 youngest spanning the interval 600 to 2 ka the results of the present study on the one hand confirm some of the previous conclusions but by contrast reveal that units sul2 and sul1 previously attributed to the holocene are actually equivalent to the older sul6 and sul5 units here dated to 814 530 ka and 530 457 ka respectively and that the u series dates previously published for both former sul2 and sul1 units yielded abnormally young ages in light of the present results a reassessment of the chronology of the sulmona basin succession and a revision of the tephrostratigraphy of the sul2 sul6 and sul1 sul5 units is in order copyright 2013 john wiley sons ltd

fitting data but poor predictions reverberation prediction uncertainty when seabed parameters are derived from reverberation measurements for many decades researchers have been developing inverse techniques for estimating seabed parameters from reverberation data notably scattering strength generally the angular dependence of the scattering kernel is unknown and is either solved for or assumed fixed in either case agreement is typically quite good between the measured reverberation and that modeled by fitting scattering parameters however what are the resulting uncertainties in a reverberation prediction if the ocean or geometry changes the main results of the paper are that 1 these prediction uncertainties are surprisingly large of order 10 db at 10 km and thus 2 traditional current methods for reverberation inversion should be augmented mitigating the large prediction uncertainties by an additional measurement several options for additional measurements are discussed

the montalbano jonico marine succession an archive for distal tephra layers at the early middle pleistocene boundary in southern italy abstract the lithological content and mineralogical assemblage of main tephra layers v1 v2 v3 v4 v5 v7 embedded in the montalbano jonico succession have been fully characterized major element analyses were carried out on the juvenile glass fractions and main crystal phases and trace element contents were determined on glasses extracted from the thickest layer of the sequence v5 single crystal 40 ar 39 ar laser fusions were performed on sanidine from the v4 layer yielding a weighted mean age of 773 9 1 3 ka the vulture volcano is likely the source of two tephra layers v3 and v4 embedded to the middle part of the interval b of the sequence which represent the oldest products of this center ever found moreover the v4 layer was emplaced near the matuyama bruhnes chron boundary and thus serves as an important chronostratigraphic marker complete chemical characterization of v5 allows us to suggest the campanian volcanic zone as its eruptive source corroborating the idea that activity there began at 720 ka and spanned most of the middle pleistocene finally we insert our new framework from the montalbano jonico sequence into a reappraised tephra sequence from the middle pleistocene to present in southern italy which results in a more robust series of tephrostratotypes and improves the reliability of inter archive correlations

tephrochronological dating of varved interglacial lake deposits from pianico sellere southern alps italy to around 400 ka the sediment record from the pianico palaeolake in the southern alps is continuously varved spans more than 15 500 years and represents a key archive for interglacial climate variability at seasonal resolution the stratigraphic position of the pianico interglacial has been controversial in the past the identification of two volcanic ash layers and their microscopic analysis provides distinct marker layers for tephrochronological dating of these interglacial deposits in addition to micro facies analyses reconstructing depositional processes of both tephra layers within the lake environment their mineralogical and geochemical composition has been determined through major element electron probe micro analysis on glass shards comparison with published tephra data traced the volcanic source regions of the pianico tephras to the campanian volcanic complex of roccamonfina italy and probably the puy de sancy volcano in the french massif central available dating of near vent deposits from the roccamonfina volcano provides a robust tephrochronological anchor point at around 400 ka for the pianico interglacial these deposits correlate with marine oxygen isotope stage mis 11 and thus are younger than early to middle pleistocene previously suggested by k ar dating and older than the last interglacial as inferred from macrofloral remains and the geo logical setting copyright 2006 john wiley sons ltd

tracking the last sea level cycle seafloor morphology and shallow stratigraphy of the latest quaternary new jersey middle continental shelf seafloor geomorphology and surficial stratigraphy of the new jersey middle continental shelf provide a detailed record of sea level change during the last advance and retreat of the laurentide ice sheet 120 kyr b p to present a nw se oriented corridor on the middle shelf between water depths of 40 m the mid shelf paleo shore and 100 m the franklin paleo shore encompasses 500 line km of 2d huntec boomer profiles 500 3500 hz an embedded 4 6 km2 3d volume and a 490 km2 swath bathymetry map we use these data to develop a relative stratigraphy core samples from published studies also provide some chronological and sedimentological constraints on the upper 5 m of the stratigraphic succession the following stratigraphic units and surfaces occur from bottom to top 1 r a high amplitude reflection that separates sediment 46 5 kyr old by ams 14c dating from overlying sediment wedges 2 the outer shelf wedge a marine unit up to 50 m thick that onlaps r 3 channels a reflection sub parallel to the seafloor that incises r and appears as a dendritic system of channels in map view 4 channels fill the upper portion of which is sampled and known to represent deepening upward marine sediments 12 3 kyr in age 5 the t horizon a seismically discontinuous surface that caps channels fill 6 oblique ridge deposits coarse grained shelly units comprised of km scale shallow shelf bedforms and 7 ribbon floored swales bathymetric depressions parallel to modern shelf currents that truncate the oblique ridges and cut into surficial deposits we interpret this succession of features in light of a global eustatic sea level curve and the consequent migration of the coastline across the middle shelf during the last 120 kyr the morphology of the new jersey middle shelf shows a discrete sequence of stratigraphic elements and reflects the pulsed episodicity of the last sea level cycle r is a complicated marine non marine erosional surface formed during the last regression while the outer shelf wedge represents a shelf wedge emplaced during a minor glacial retreat before maximum wisconsin lowstand i e marine oxygen isotope stage 3 1 channels is a widespread fluvial subarial erosion surface formed at the late wisconsin glacial maximum 22 kyr b p the shoreline migrated back across the mid shelf corridor non uniformly during the period represented by channels fill oblique ridges are relict features on the new jersey middle shelf while the ribbon floored swales represent modern shelf erosion there is no systematic relationship between modern seafloor morphology and the very shallowly buried stratigraphic succession

volcanological evolution of mount erciyes stratovolcano and origin of the valibaba tepe ignimbrite central anatolia turkey abstract mount erciyes 3917 m is the largest stratovolcano of central anatolia turkey the volcanological evolution of mount erciyes from pliocene quaternary to historical times exhibits two distinct stages 1 koc dag and 2 erciyes during the koc dag stage basaltic and andesitic lava flows were emitted from the cinder cones of kizil tepe and topakkaya tepe then koc dag pyroclastics were emplaced leading to a caldera collapse of 14 18 km in diameter with a volume estimated at 110 km3 two eruption phases separated by scoria fall and mud flow deposits are recognised associated with the caldera forming event during phase 1 plinian fall and pumice flows were emplaced on the eastern part of the volcano plinian fall deposits occur more than 50 km away from the source area the volume of tephra is estimated at 63 3 km3 16 km3 dense rock equivalent dre including 62 km3 of plinian fall and 1 3 km3 pumice flow deposits phase 2 mainly consists of pyroclastic flow deposits two pumiceous flow units and valibaba tepe ignimbrite vti the pumiceous flow deposits 4 2 km3 dre extend 30 km from the inferred source area towards the north and northeast the final pyroclastic flows of phase 2 occurred 2 8 ma ago and produced the vti the vti is a low aspect ratio welded ignimbrite and its volume is estimated at 40 km3 dre plinian fall deposits 0 8 km3 dre preceded the vti and are only observed on the eastern part of the volcano covering an area of 1500 km2 during the erciyes stage two eruptive cycles are defined the first cycle 2 6 0 17 ma is characterised by effusive extrusive and weakly explosive activity with emplacement of andesitic lava flows dacitic dome flows basaltic andesite lava flows and andesitic cones the second cycle involved dacitic extrusive and explosive activity located at the summit area and produced block and ash flows derived from rhyodacitic domes plinian fall surge and pumice flow deposits were emplaced prior to rhyodacitic dome extrusions the last event was the emplacement of debris avalanche deposits related to sector collapse caldera

icebergs not the trigger for north atlantic cold events a delay between surface cooling and the arrival of ice rafted debris at a site southwest of iceland over the past four glacial cycles implies that icebergs typically arrived too late to have triggered cooling although the freshwater derived from melting icebergs may provide a positive feedback for cold stadial conditions much attention has been paid to the causes of abrupt climate change as recorded by the greenland ice cores one theory implicates disruption caused by vast armadas of icebergs introducing fresh water to the surface ocean increasing density gradients and changing ocean circulation and hence climate limited evidence has suggested that this might not be the case as the iceberg releases sometimes seem to follow not lead the climate changes stephen barker and colleagues now present a record of ice rafted debris and a temperature sensitive planktonic foraminifer and conclude that during the past 425 000 years at least icebergs generally arrived too late to induce abrupt climate change abrupt climate change is a ubiquitous feature of the late pleistocene epoch1 in particular the sequence of dansgaard oeschger events repeated transitions between warm interstadial and cold stadial conditions as recorded by ice cores in greenland2 are thought to be linked to changes in the mode of overturning circulation in the atlantic ocean3 moreover the observed correspondence between north atlantic cold events and increased iceberg calving and dispersal from ice sheets surrounding the north atlantic4 has inspired many ocean and climate modelling studies that make use of freshwater forcing scenarios to simulate abrupt change across the north atlantic region and beyond5 6 7 on the other hand previous studies4 8 identified an apparent lag between north atlantic cooling events and the appearance of ice rafted debris over the last glacial cycle leading to the hypothesis that iceberg discharge may be a consequence of stadial conditions rather than the cause4 9 10 11 here we further establish this relationship and demonstrate a systematic delay between pronounced surface cooling and the arrival of ice rafted debris at a site southwest of iceland over the past four glacial cycles implying that in general icebergs arrived too late to have triggered cooling instead we suggest that on the basis of our comparisons of ice rafted debris and polar planktonic foraminifera abrupt transitions to stadial conditions should be considered as a nonlinear response to more gradual cooling across the north atlantic although the freshwater derived from melting icebergs may provide a positive feedback for enhancing and or prolonging stadial conditions10 11 it does not trigger northern stadial events

a 600 000 year long continental pollen record from lake van eastern anatolia turkey abstract lake van is the fourth largest terminal lake in the world 38 5 n 43 e volume 607 km 3 area 3570 km 2 maximum water depth 460 m extending for 130 km wsw ene on the eastern anatolian high plateau turkey the sedimentary record of lake van partly laminated obtains a long and continuous continental sequence that covers multiple interglacial glacial cycles promoted by the potential of the sedimentary sequence for reconstructing the paleoecological and paleoclimate development of the near east a deep drilling operation was carried out in 2010 supported by the international continental scientific drilling program icdp the 219 m long continental pollen record presented here is based on a well dated composite profile drilled on the so called ahlat ridge in water depth of 360 m encompassing the last 600 000 years it is the longest continuous continental pollen record of the quaternary in the entire near east and central asia obtained to date the glacial interglacial cycles and pronounced interstadials are clearly reflected in the vegetation development based on millennial scale time resolution in general the glacial stadial vegetation is characterized by dwarf shrub steppe and desert steppe whereas the climax vegetation of past interglacials can be described as oak steppe forest similar to the present interglacial in this sensitive semi arid region between the black caspian and mediterranean seas by comparing the lake van pollen record with other western asian and southern european long continental pollen sequences as well as marine and ice core records the regional variability of the climate signals is also discussed

four climate cycles of recurring deep and surface water destabilizations on the iberian margin centennial climate variability over the last ice age exhibits clear bipolar behavior high resolution analyses of marine sediment cores from the iberian margin trace a number of associated changes simultaneously proxies of sea surface temperature and water mass distribution as well as relative biomarker content demonstrate that this typical north south coupling was pervasive for the cold phases of climate during the past 420 000 years cold episodes after relatively warm and largely ice free periods occurred when the predominance of deep water formation changed from northern to southern sources these results reinforce the connection between rapid climate changes at mediterranean latitudes and century to millennial variability in northern and southern polar regions

eruptive history of a low frequency and low output rate pleistocene volcano ciomadul south harghita mts romania based on a new set of k ar age data and detailed field observations the eruptive history of the youngest volcano in the whole carpathian pannonian region was reconstructed ciomadul volcano is a dacitic dome complex located at the southeastern end of the c limani gurghiu harghita neogene volcanic range in the east carpathians it consists of a central group of extrusive domes the ciomadul mare and haramul mare dome clusters and the koves ponk dome surrounded by a number of isolated peripheral domes some of them strongly eroded balvanyos puturosul and others topographically well preserved haramul mic dealul mare one of the domes dealul cet ii still preserves part of its original breccia envelope a large number of bread crust bombs found mostly along the southern slopes of the volcano suggest that the dome building activity at ciomadul was punctuated by short vulcanian type explosive events two late stage explosive events that ended the volcanic activity of ciomadul left behind two topographically well preserved craters disrupting the central group of domes the larger diameter shallower and older mohos phreatomagmatic crater and the smaller deeper and younger sf ana sub plinian crater phreatomagmatic products of the mohos center including accretionary lapilli bearing base surge deposits and poorly sorted airfall deposits with impact sags are known close to the eastern crater rim a key section studied in detail south of b ile tusnad shows the temporal succession of eruptive episodes related to the sf ana sub plinian event as well as relationships with the older dome building stages the age of this last eruptive event is loosely constrained by radiocarbon dating of charcoal pieces and paleosoil organic matter at ca 27 35 ka the age of the mohos eruption is not constrained but we suggest that it is closely related to the sf ana eruption the whole volcanic history of ciomadul spans over ca 1 myr starting with the building up of peripheral domes and then concentrating in its central part ciomadul appears as a small volume ca 8 74 km3 and very low frequency and low output rate volcano ca 9 km3 myr at the terminus of a gradually diminishing and extinguishing volcanic range a number of geodynamically active features strongly suggest that the magma plumbing system beneath ciomadul is not completely frozen so future activity cannot be ruled out

impact of volcanism on the evolution of lake van ii temporal evolution of explosive volcanism of nemrut volcano eastern anatolia during the past ca 0 4ma thirty two new single crystal ages document 400 000 years of widespread explosive volcanism of historically active nemrut volcano towering over huge alkaline lake van eastern anatolia the dated deposits were selected to monitor the volcanic and compositional evolution of nemrut volcano through time and thus to provide a rigorous temporal framework for the tephra record of the paleovan drilling project tephra samples were taken from large volume deposits or those that occur in medial to distal localities well exposed stratigraphic sections or from the initial phase of an eruptive sequence mainly fallout deposits were chosen because most ignimbrites show more complex and corroded feldspar populations owing to compositional zoning and magma mixing moreover fallout deposits held the promise to be more clearly identifiable with and correlatable to 300 tephra layers in the paleovan drill cores even though commonly in amounts marginal or insufficient in thickness to allow well supported single crystal dating the crystals dated are dominantly anorthoclase the main phenoctyst phase in the trachytic to rhyolitic slightly to strongly peralkaline nemrut magmas ages obtained so far range from ca 400 ka to ca 30 ka for nemrut volcano the causes of significant changes in the frequency volume and composition of tephra layers per unit time are discussed in terms of external erosion climate changes geodynamic factors and internal forcing changes in magma supply and composition and incubation periods preceding large volume rhyolitic eruptions for example the low frequency of tephra layers deposited prior to ca 200 ka may be due to low explosive activity severe erosion between mis 9 and mis 11 or both nevertheless the overall frequency of explosive eruptions appears to have increased during the past ca 200 ka we also recognize a slight peak in explosive eruptions during warm periods e g mis 5 and mis 7 and speculate on lithospheric unloading triggering increased partial melting or magma reservoir unloading following massive glacier melting the ages of 5 dated ignimbrites span ca 250 000 years suggesting that nemrut volcano went through a polycyclic evolution with multiple caldera collapses and major pyroclastic flow eruptions the oldest dated so far as 265 ka the widely held view of the impressive nemrut caldera now dated to have formed at ca 30 ka as the main paroxysmal event during the evolution of the volcano is no longer tenable distinct and coherent compositional characteristics especially in trace element concentrations characterize several groups of trachytic tephras we speculate that the growth of nemrut volcano caused the isolation of the lake van basin on account of their mineralogical anorthoclase hedenbergite fayalite aenigmatite and alkalic chemical compositions and large volume dated nemrut fallout tephras are likely to represent excellent markers in lakes and other sites of paleoclimatological or archeological interest in neighboring countries to the northeast of lake van as far as the caspian sea in what may be called the east anatolian tephra province

neogene quaternary magmatism and geodynamics in the carpathian pannonian region a synthesis in the carpathian pannonian region in neogene times westward dipping subduction in a land locked basin caused collision of two lithospheric blocks alcapa and tisia with the southeastern border of the european plate calc alkaline and alkaline magmatism was closely related to subduction rollback collision and extension from the spatial distribution of the magmatic activity four segments can be defined western segment magmatism occurring on the alcapa block central segment magmatism occurring on both alcapa and the tisia blocks south eastern segment and interior segment both on the tisia block most calc alkaline magmatism in the region resulted from melting of a heterogeneous asthenospheric mantle source modified by addition of fluids and sediment assimilation and fractionation processes at shallow crustal levels occurred in most of the segments strongly masking the deeper source processes long term subduction rollback and or delamination led to contamination of the asthenosphere beneath the western segment here large volume partial melts of the contaminated mantle caused underplating and crustal anatexis leading to mixing of mantle derived calc alkaline magmas with crustal melts in the central segment calc alkaline magmas were formed by subduction and rollback followed by back arc extension and slab breakoff avariable mantle source is indicated in the back arc setting and larger amount of fluid induced metasomatism source enrichment and assimilation nearer to the trench in the interior segment evolution from typical calc alkaline magmas to adakite like ones was related to extension due to fast rotations and transtensional tectonics here calc alkaline magmas formed by decompression melting of a heterogeneous crust mantle lithosphere while adakite like melts resulted from fliud dominated melting of the lithosphere along the south eastern segment slab breakoff was responsible for the generation of typical calcalkaline magmas but in the extreme south of the segment shallow level tearing of the slab followed breakoff strike slip tectonics allowed the rise of hot asthenosphere and generation of adakite like magmas via slab melting along the torn edge of the east european plate alkalic basaltic volcanism with an oib like asthenosphere source followed the calc alkaline stage

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

high resolution swath sonar investigation of sand ridge dune and ribbon morphology in the offshore environment of the new jersey margin abstract sand ridges on the northeast us atlantic shelf form in the near shore environment most likely in response to storm driven flows as the holocene transgression has continued the ridges have been transferred to an offshore hydrodynamic regime where currents are not constrained by the coast and storms do not influence bottom currents as frequently or as strongly here we qualitatively and quantitatively investigate the morphology of offshore sand ridges and smaller scale features in an effort to place constraints on bedform development in these deeper waters a recent high resolution swath sonar survey mapped a portion of the new jersey shelf from 20 m water depth to the shelf break 120 m imaging both sand ridges and smaller scaled dunes and ribbons in far greater detail than has been previously possible using a robust statistical analysis we find that the gross morphology of ridges height width length does not change with depth beyond 20 m water depth and changes in ridge orientation generally mirror changes in regional contour orientation hence ridges have not continued to grow since transgression has brought them into the offshore hydrodynamic regime however on the inner shelf 20 m water depth to the mid shelf shore we do find evidence in the ridge shape which has an asymmetry opposite to that seen near shore and in the complex backscatter response that some important modifications to ridges are taking place at these water depths in contrast on the mid shelf from the mid shelf shore to the franklin shore ridges tend to have higher backscatter at the crests implying that these are largely winnowed relict features lineated smaller scale 100 500 m wavelength

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

acigol rhyolite field central anatolia part 1 high resolution dating of eruption episodes and zircon growth rates protracted pre eruptive zircon residence is frequently detected in continental rhyolites and can conflict with thermal models indicating briefer magma cooling durations if scaled to erupted volumes here we present combined u th and u th he zircon ages from the acigol rhyolite field central anatolia turkey which is part of a quaternary bimodal volcanic complex unlike other geochronometers this approach dates crystallization and eruption on the same crystals allowing for internal consistency testing despite the overall longevity of acigol rhyolite volcanism and systematic trends of progressive depletion in compatible trace elements and decreasing zircon saturation temperatures we find that zircon crystallized in two brief pulses corresponding to eruptions in the eastern and western part of the field during middle and late pleistocene times respectively for late pleistocene zircon resolvable differences exist between interior average 30 7 0 9 ka 1 error and rim 21 9 1 3 ka crystallization ages these translate into radial crystal growth rates of 10 13 to 10 14 cm s broadly consistent with those constrained by diffusion experiments rim crystallization and u th he eruption ages 24 2 0 4 ka overlap within uncertainty evidence for brief zircon residence at acigol contrasts with many other rhyolite fields suggesting that protracted zircon crystallization in or recycling from long lived crystal mushes is not ubiquitous in continental silicic magma systems instead the span of pre eruptive zircon ages is consistent with autochthonous crystallization in individual small volume magma batches that originated from basaltic precursors

tsunami source inversion using tide gauge and dart tsunami waveforms of the 2017 mw8 2 mexico earthquake on september 8 2017 utc a normal fault earthquake occurred 87 km off the southeast coast of mexico this earthquake generated a tsunami that was recorded at coastal tide gauge and offshore buoy stations first we conducted a numerical tsunami simulation using a single fault model to understand the tsunami characteristics near the rupture area focusing on the nearby tide gauge stations second the tsunami source of this event was estimated from inversion of tsunami waveforms recorded at six coastal stations and three buoys located in the deep ocean using the aftershock distribution within 1 day following the main shock the fault plane orientation had a northeast dip direction strike 320 circ dip 77 circ and rake 92 circ the results of the tsunami waveform inversion revealed that the fault area was 240 km 90 km in size with most of the largest slip occurring on the middle and deepest segments of the fault the maximum slip was 6 03 m from a 30 30 km2 segment that was 64 82 km deep at the center of the fault area the estimated slip distribution showed that the main asperity was at the center of the fault area the second asperity with an average slip of 5 5 m was found on the northwest most segments the estimated slip distribution yielded a seismic moment of 2 9 times 10 21 nm mw 8 24 which was calculated assuming an average rigidity of 7 times 10 10 n m2

isotopic sr nd and major element fingerprinting of distal tephras an application to the middle late pleistocene markers from the colli albani volcano central italy abstract we describe the diagnostic lithological and chemical features of distal tephras from major middle late pleistocene 560 36 ka explosive eruptions of the colli albani volcanic district central italy in particular we explore the time dependent variability of the sr and nd isotope compositions as a tool for recognising and pinpointing individual colli albani tephra in distal settings the distal tephras investigated are in lacustrine and fluvial sediments of central apennine intermountain basins located 70 km 100 km east of colli albani the recognition of the colli albani tephras is essentially based on the k foiditic composition of their glass which within the italian volcanological framework is a distinctive character of the colli albani pyroclasts in detail these tephras are attributed to the following eruptive units tufo pisolitico di trigoria 561 2 ka tufo del palatino tufo di bagni albule 530 2 527 2 ka tufo di bagni albule pozzolane rosse air fall sequence 517 1 to 500 3 ka pozzolane rosse 457 4 ka villa senni 365 4 ka and albano 5 7 41 7 to 36 1 ka these correlations are supported by 40 ar 39 ar dating of the distal tephras correlated to the pozzolane rosse 457 4 1 7 ka villa senni 365 2 ka and albano 5 7 41 9 ka and by 87 sr 86 sr measured on clinopyroxene crystals and fresh glassy scoria from distal colli albani tephras that range from 0 711 to 0 709 these ratios are similar to those that characterise the individual proximal correlative units and show the same decreasing trend over time in contrast the 143 nd 144 nd ratios for proximal and distal bulk samples and clinopyroxene increase from 0 51212 to 0 51215 from the oldest to the youngest tephra deposit in summary the study of sr and nd isotope compositions that is here applied on products from the colli albani volcanic district is a powerful complementary tool to the more traditional tephrostratigraphic methods e g componentry and electron microprobe analysis for fingerprinting of distal tephras over a large region of the central mediterranean and over a large time interval such as from 560 ka to 36 ka

improved age estimates for key late quaternary european tephra horizons in the reset lattice abstract the research project response of humans to abrupt environmental transitions reset used tephra layers to tie together and synchronise the chronologies of stratigraphic records at archaeological and environmental sites with the increasing importance of tephra as chronological markers in sedimentary sequences both in this project and more generally comes a requirement to have good estimates for the absolute age of these volcanic horizons this paper summarises the chronology of the key tephra in the reset tephra lattice in the time range 10 60 ka bp from the existing literature from papers produced as part of the reset project and reanalysis conducted for this paper the paper outlines the chronological approach taken to the dating of tephra within the reset project and the basis for further work as part of the intimate integrating ice core marine and terrestrial records initiative for each of the tephra layers in the lattice the existing literature is discussed and where relevant date estimates updated using the latest radiocarbon calibration curves intcal13 and marine13 and methods maps show the approximate extent of tephra finds giving a visual indication of the coverage of the lattice in different time periods

a high resolution tephrochronological record of mis 14 12 in the southern apennines acerno basin italy abstract lithological mineralogical and glass chemical analyses on juvenile fragments extracted from 20 tephra layers embedded within the lacustrine sediments of the acerno basin southern apennines italy were carried out together with four sanidine 40 ar 39 ar age determinations the measured ages span the interval between 561 and 493 ka middle pleistocene eruptive activity at roman province volcanoes was identified as the main possible source of the investigated tephra layers some of them were correlated with precise terrestrial counterparts corresponding to large explosive events of the sabatini e g tufo giallo della via tiberina and alban hills volcanic districts e g tufo pisolitico di trigoria the integration of tephrochronology and pollen analyses allowed the acerno lacustrine sedimentation to be constrained between mis 14 and 12 which overlaps with several well studied lacustrine successions of the southern apennines the correlation with other tephrostratigraphic records from intramontane basins in central southern apennines testifies to the wide dispersal of at least three tephra layers that serve as marker layers thus improving the resolution of the middle pleistocene italian tephrostratotype

age and geochemistry of tephra layers from ischia italy constraints from proximal distal correlations with lago grande di monticchio unraveling the eruptive history of the island of ischia southern italy is problematic due to its burial caldera collapse resurgent uplift and erosion here we present new major and trace element glass data for 39 75 ka proximal tephra deposits including those of the caldera forming monte epomeo green tuff megt eruption correlations with the distal tephra archive preserved at lago grande di monticchio lgdm are used to constrain the timing of as yet undated eruptive events out of 13 lgdm tephras analysed from the 39 104 ka time window glass geochemical data show that all are compositionally consistent with the explosive volcanic eruptions of ischia whilst 5 of them can be correlated with specific proximal deposits pre megt pyroclastic sequences comprise three compositional groups these groups occur repeatedly in sucessive eruptions proximal distal correlations indicate that the porticello eruption occurred at 59 2 ka and the tisichiello eruption probably occurred at 76 3 ka the megt eruption is correlated with lgdm tm 19 which has been directly dated at 55 2 ka post megt tephras form compositional groups that overlap with the pre megt but are displaced to lower feo and tio2 and lower incompatible element contents proximal distal correlations indicate that the schiappone and pietre rosse eruptions occurred at 50 6 2 0 ka and 45 6 ka respectively tephra from the megt eruption span a wide compositional range broadly overlapping the three pre megt compositional groups but are displaced to higher nd and y and contain an additional less evolved glass population glass geochemistry is used to recognise and confirm distal equivalents of the megt at lgdm tm 19 and in the ionian y 7 adriatic prad 1870 and tyrrhenian c 18 md 28 seas distal occurences of megt tephra define a dispersal axis to the south southeast and are found as far as 540 km from ischia making the megt one of the most widely dispersed late quaternary pyroclastic deposit erupted in the campanian region we estimate a volume of approximately 40 km3 for the fallout portion of the megt pyroclastic sequence on the basis of proximal and distal deposit thicknesses

tephrostratigraphy and tephrochronology in the philippi peat basin macedonia northern hellas greece abstract three tephra layers have been identified in the upper 15 m of a 190 m section of peat beneath the philippi fen they provide significant lithological and chronological markers throughout the fen and the aegean region the upper tephra pht1 consists of shards of a transparent calcalkaline felsic glass and fragments of plagioclase augite hypersthene and rare hornblende magnetite apatite and quartz peat directly beneath pht1 gave a radiocarbon approximate age of 13 000 yr the middle tephra layer pht2 which resembles pht1 in chemistry and petrography but contains more crystals and lithic fragments rests on peat dated ca 18 000 14 c yr bp the lower tephra pht3 has colorless to brown glass shards with a trachytic chemistry and a mineral assemblage of sanidine sodic plagioclase biotite aegirine augite hornblende titanite and apatite bracketing radiocarbon ages imply that pht3 accumulated about 30 000 14 c yr bp the likely ages of pht1 and pht2 together with their mineralogical and chemical characteristics suggest that these tephras came from the volcanic field of thera in the hellenic arc pht2 particularly was derived from a major known explosive eruption ca 18 000 yr bp the cape riva eruption correlative to the y 2 tephra layer evidence for pht3 suggests derivation from the campanian province of italy and correlation with the campanian ignimbrite and the y 5 ash beneath the mediterranean sea

geological factors influencing the concentration of trace elements in the philippi peatland eastern macedonia greece abstract six peat samples obtained from the holocene and the weichselian of the philippi peat deposit eastern macedonia greece were analyzed for 48 trace elements by inductively coupled plasma mass spectrometry icp ms the ash contents of these samples were also determined most of the trace elements are associated with the minerals in the peat while ge mo pb se ta tl u and w display a greater affinity with the organic matter compared with crustal averages clarke concentrations the philippi peat is enriched in some elements ag as au cd mo se te u and w because of the respective mineralizations in the area the philippi peat is also enriched in cr cu mo pb sc sn t v y and zn in comparison with typical fen peats as well as in as cr mo se and u in comparison with typical coals climatic and hydrogeological conditions strongly influenced the peat forming environment resulting in a differentiation between holocene and weichselian peat generally the holocene peat contains lower concentrations of trace elements in the northern and southern part of the fen than the weichselian one the opposite trend is observed in the fen area close to the western basin margins

temporal evolution of the roccamonfina volcanic complex pleistocene central italy abstract the roccamonfina volcanic complex rvc in southern italy is an early to middle pleistocene stratovolcano sharing temporal and morphological characteristics with the somma vesuvius and the alban hills both being associated with high volcanic hazard for the cities of naples and rome respectively the rvc is important for the understanding of volcanic evolution in the roman and campanian volcanic provinces we report a comprehensive study of its evolution based on morphological geochemical and k ar geochronological data the rvc was active from c a 550 ka to 150 ka its evolution is divided into five stages defining a volcanic pulse recurrence time of c a 90 100 kyr the two initial stages consisted in the construction of two successive stratovolcanoes of the tephrite phonolite namely high k series the first stage was terminated by a major plinian eruption emplacing the trachytic rio rava pumices at 439 9 ka at the end of the second stage the last high k series stratovolcano was destroyed by a large sector collapse and the emplacement of the brown leucitic tuff blt at 353 5 ka the central caldera of the rvc is the result of the overlapping of the rio rava and of the blt explosions the plinian eruption of the blt is related to the emptying of a stratified deep seated hks magma chamber during the upwelling of k series ks magma marking a major geochemical transition and plumbing system re organization the following stage was responsible for the emplacement of the lower white trachytic tuff at 331 2 ka and of basaltic trachytic effusive products erupted through the main vent the subsequent activity was mainly restricted to the emplacement of basaltic shoshonitic parasitic cones and lava flows and of minor subplinian deposits of the upper white trachytic tuff between 275 and 230 ka the northern crater is most probably a maar that formed by the phreatomagmatic explosion of the yellow trachytic tuff at 230 ka the latest stage of activity featured the edification of the central shoshonitic domes at c a 150 ka

distribution and chemical composition of tephra layers from eastern mediterranean abyssal sediments abstract most cores of late quaternary sediments from the eastern mediterranean sea contain many ash layers glass shards from discrete layers have been analysed chemically for major elements the layers from different cores have been correlated and unambiguously related to known volcanic events on the basis of the chemical data most of the layers are derived from explosive eruptions of the santorini volcanic complex other layers have their source in other volcanoes of the hellenic arc yali nisyros kos one layer originated from the campanian area italy

tephra correlations and climatic events between the mis6 5 transition and the beginning of mis3 in theopetra cave central greece abstract three cryptotephra layers associated with important periods of climatic change were identified in the middle palaeolithic sequence of theopetra cave greece the lower cryptotephra layer thp tii5 is correlated with the p 11 pantellerian eruption dated to 128 131 ka this cryptotephra postdates a thick sequence of combustion layers that show a complex vegetation succession quite similar to that of the last deglaciation succession in the cave two other cryptotephras thp tii10 and thp tii12 are correlated with the nisyros upper pumice and the pantellerian y6 green tuff dated to 50 ka and 45 7 ka respectively this sequence confirms the position of the nisyros upper tephra below the pantellerian green tuff in the volcanic event stratigraphy of the mediterranean moreover these two upper cryptotephras bracket an extended combustion layer with interstadial vegetation characteristics that may be coincident with the complex greenland interstadial 13 14 on the basis of this new chronology it can be deduced that the intensity of occupation and presence or absence of humans in the cave were closely related to climatic changes in addition a remarkable similarity in the pattern of occupational intensity during the last two deglaciations can be suggested

8 khz bottom backscattering measurements at low grazing angles in shallow water 8 khz bottom backscattering measurements at low grazing angles 6 degrees 31 degrees are presented the experiment was performed at a very shallow water site with a silty bottom on the south coast of korea backscattering strengths between 42 and 30 db were obtained and were compared to a theoretical backscattering model and lambert s law the fit of the theoretical model to the measurements suggests that sediment volume scattering is dominant over scattering from bottom interface roughness combining these results with previous measurements found in the published literature implies that backscattering strengths from silty sediment increase slightly as the frequency increases

fission track dating obsidians in central and northern anatolia twenty obsidian samples from central and north anatolia were dated by the fission track method split samples analyzed in two different laboratories give consistent results data presented refer to three volcanic fields and are summarized as follows orta sakaeli northern anatolia obsidians with ages from 21 23 ma gollu dagi dome complex near ciftlik central anatolia has given ages between 1 33 0 98 ma acigol caldera central anatolia shows three age groups 1 eruptions of precaldera bogazkoy obsidians with ages 0 18 0 15 ma 2 formation of the large intracaldera dome kocadag taskesiktepe at about 0 08 ma uncorrected apparent age of 0 075 ma and 3 acigol peripheral obsidian domes with plateau ages of 0 020 and 0 019 ma and an additional uncorrected age of 0 018 ma form a distinct age group this fission track parameters discriminate between the various obsidian sources of prehistoric obsidian artifacts

cryptotephras the revolution in correlation and precision dating from its icelandic origins in the study of visible tephra horizons tephrochronology took a remarkable step in the late 1980 s with the discovery of a ca 4300 year old microscopic ash layer in a scottish peat bog since then the search for these cryptotephra deposits in distal areas has gone from strength to strength indeed a recent discovery demonstrates how a few fine grained glass shards from an alaskan eruption have been dispersed more than 7000 km to northern europe instantaneous deposition of geochemically distinct volcanic ash over such large geographical areas gives rise to a powerful correlation tool with considerable potential for addressing a range of scientific questions a prerequisite of this work is the establishment of regional tephrochronological frameworks that include well constrained age estimates and robust geochemical signatures for each deposit with distal sites revealing a complex record of previously unknown volcanic events frameworks are regularly revised and it has become apparent that some closely timed eruptions have similar geochemical signatures the search for unique and robust geochemical fingerprints thus hinges on rigorous analysis by electron microprobe and laser ablation inductively coupled plasma mass spectrometry historical developments and significant breakthroughs are presented to chart the revolution in correlation and precision dating over the last 50 years using tephrochronology and cryptotephrochronology

low grazing angle bistatic sea floor scattering on the florida atlantic coastal shelf observations of bistatic scattering at moderate frequencies 3750 hz 7500 hz and 15 000 hz and low grazing angles 2 20 are presented with a geoacoustical description of the site given a source receiver separation of 80 7 m bistatic scattering strengths in the sandy sediments at the measurement site range from 70 to 15 db the observed bistatic scattering at low grazing angles depends primarily on the incident bearing angle bistatic scattering values are highest along the transect between the source and receiver maximum scattering strengths 20 to 15 db appear 30 m from the receiver regions of high scattering 30 db strength are centered along the direct path between the source and receiver the contribution of volume scattering to the observed scattering pattern is not very clear however given the sandy sediments found at the site roughness scattering is expected to be a major contributor to the observed bistatic scattering patterns

fault and basin depocentre migration over the last 2 ma in the l aquila 2009 earthquake region central italian apennines abstract morphological stratigraphical and structural investigations integrated with palaeomagnetic and tephrostratigraphic studies and 40 ar 39 ar measurements allowed us to define the quaternary tectonic sedimentary evolution of the epicentral area of the l aquila 2009 earthquake m w 6 3 this area roughly matches the paganica san demetrio castelnuovo psc intermountain basin filled by a fluvio lacustrine succession that is variously deformed by normal faults at its early stage early pleistocene ca 2 ma the basin hosted a lake that was characterised by whitish carbonate silt and mud deposition towards the end of the early pleistocene this was partly filled by a south eastward prograding deltaic system the south easternmost portion of the deltaic system was successively abandoned and eroded while sedimentation of a braided river system developed in a smaller area westwards before 780 ka this fluvio lacustrine system the lower psc syntheme ended and the area underwent erosional and pedogenic processes these processes continued up to 460 ka with the onset of fluvial gravel and volcanic rich silty sand deposition over a narrow area of the south western psc basin an earlier unit of the upper psc syntheme early middle pleistocene around 460 ka when most of this area was again subjected to denudational processes the sedimentation migrated into the previously exposed north western area of the psc basin where fluvial alluvial sediments were deposited between ca 460 ka and ca 350 ka a later unit of the upper psc syntheme between ca 350 ka and the present the sedimentation continued uninterrupted in a slight westwards restricted area of the psc basin upper late psc syntheme the significant contraction of the basin the shifting of its depocentre the variation in its geometry and in the spatial distributions and thicknesses of the units constituting the lower upper and late psc synthemes provide evidence for strong tectonic control this resulted in progressive reduction of the activity of the south easternmost tectonic structures and parallel migration of the fault activity on the westernmost structures in this perspective the fault system responsible for the l aquila 2009 earthquake can be seen as the most recent expression of a long lasting westwards polarised process of tectonic activity transfer

impact of volcanism on the evolution of lake van eastern anatolia iii periodic nemrut vs episodic suphan explosive eruptions and climate forcing reflected in a tephra gap between ca 14ka and ca 30ka fifteen lateglacial to holocene rhyolitic dominantly primary tephra layers piston cored and drilled icdp paleovan drilling project in western lake van eastern anatolia turkey were precisely correlated to either of the two adjacent and active large volcanoes nemrut and suphan based on shard textures mineralogy and mineral and glass compositions the young peralkaline comenditic to pantelleritic primary rhyolitic nemrut tephras are characterized by anorthoclase hedenbergitic to augitic clinopyroxene fayalitic olivine minor quartz and rare accessory chevkinite and zircon phenocrysts in subalkaline primary rhyolitic suphan tephras are chiefly oligoclase labradorite with minor k rich sanidine in some biotite amphibole hypersthene rare augitic clinopyroxene relatively common allanite and rare zircon two contrasting explosive eruptive modes are distinguished from each other episodic suphan and periodic nemrut the lateglacial suphan tephra swarm covers a short time interval of ca 338 years between ca 13 078 vy bp and 12 740 vy bp eruptions having occurred statistically every ca 42 years with especially short intervals between v 11 reworked and v 14 causes for the strongly episodic suphan explosive behavior might include seismic triggering of a volcano magma system unable to erupt explosively without the benefit of external triggering as reflected in pervasive faulting preceding the suphan tephra swarm seismic triggering may have caused the rise of more mafic trachyandesitic parent magma heating near surface pockets of highly evolved magma that might have formed silicic domes during this stage of volcano evolution resulting in ascent and finally explosive fragmentation of magma essentially by external factors probably significantly enhanced by magma water ice interaction explosive eruptions of the nemrut volcano system interpreted to be underlain by a large fractionating magma reservoir follow a more periodic mode of a long term relatively constant supply of parent magma b evolution by low pressure crystal fractionation resulting in sporadic relatively low volume eruption of trachytic and minor rhyolitic magmas c evolution of a large magma reservoir to the point of highly explosive large volume peralkaline rhyolitic plinian eruptions at temporal intervals of ca 20 40 ky some accompanied by ignimbrites and inferred caldera collapse a striking tephra gap between ca 14 ka and ca 30 ka i e during glacial climate conditions is postulated to be due to climate forcing via lithosphere unloading following deglaciation

measurement technique for bottom scattering in shallow water sonar performance predictions of reverberation in shallow water rely upon good estimates of the bottom scattering strength however little is understood about bottom scattering in shallow water in the frequency range 400 4000 hz particularly its dependency upon frequency and its relationship to the physical properties of the seafloor in order to address these issues a new measurement technique has been developed to probe the frequency and angular dependency of bottom scattering strength the experimental technique is described which employs either coherent or incoherent sources lightbulbs in addition measurement and modeling results for two diverse shallow water sites are presented at one site the scattering appears to arise at or near the water sediment interface at the other site scattering from a 23 m sub bottom horizon is clearly apparent in the data at and below 1800 hz the fact that our measurement technique can directly reveal the presence of sub bottom scattering is a significant advance in the development of methods to explore the physical mechanisms that control bottom scattering

volcanological and petrological evolution of the eastern vulsini district central italy on the basis of recent field mapping data stratigraphic reconstruction and k ar datings a volcanological and petrological study of the bolsena and montefiascone volcanic zones eastern vulsini district has been carried out ten main eruptive phases with both effusive and explosive activity have been recognized these are characterized by a large range of magma compositions belonging to the leucitite basanite and shoshonite magmatic series within each series near primary magmas and slightly to strongly differentiated products are present although in different proportions the great majority of differentiated products mostly trachytic outcrops in the northern sectors of the eastern vulsini district bolsena volcanic zone where lavas or pyroclastics were erupted during moderate to large volume plinian type and ignimbrite forming explosive activity by contrast abundant rather undifferentiated magmas are more frequently found in the southern sectors of the eastern vulsini district montefiascone volcanic zone the structural setting of the sedimentary substratum as well as its lithological characteristics may have played an important role in producing this magma distribution the very shallow position a few hundred meters below the topographic surface of the top of the fracturated carbonate basement would have facilitated the uprising of abundant less evolved magmas in the montefiascone volcanic zone whereas relatively large magma bodies a few kilometer deep can only be inferred in the bolsena volcanic zone bolsena caldera where a front of overthrust sheets of the tuscan and umbrian sedimentology sequences is most probably present in this area source vents of explosive activity show a tendency to shift northeastward with time feeding systems were also differently oriented e w and wnw ese in the southern sectors and nw se and nnw sse in the northern sectors while a ns system was related to a late stage activity of the whole eastern vulsini district

the relationship between potassic and calc alkaline post orogenic magmatism at vico volcano central italy abstract post orogenic magmatism in italy took place during the plio pleistocene alkaline ultrapotassic magmas and sub alkaline magmas were erupted from closely spaced volcanoes throughout the central part of italy therefore central italy is one of the best site to study the relationship between calc alkaline and alkaline magmatism in complex tectonic regimes activity at vico volcano developed in three periods between 0 419 ma and 0 095 ma vico products overlie leucite free volcanic rocks of monte cimino volcano that have a variable affinity from high potassium calc alkaline to ultrapotassic most of the vico rocks are leucite bearing roman type ultrapotassic however during the first period leucite free silicic rocks are interbedded with leucite bearing products the early erupted vico magmas are isotopically distinct from the youngest magmas age corrected sr sr i 0 71110 0 71149 and nd nd i 0 51210 0 51211 isotope ratios fall within the gap between roman type including younger vico and monte cimino rocks some leucite free vico rocks contain orthopyroxene crystals and al contents in clinopyroxenes are lower than those in clinopyroxenes from roman type rocks these characteristics are however also found in monte cimino rocks at the beginning of the first period leucite free latites to trachytes and rhyolites with high sr i 0 71127 0 71149 were erupted trachytes and leucite bearing latites with lower sr i 0 71110 0 71138 were erupted later the younger trachytes have higher rb and lre element contents than older leucite free rocks with similar sio 2 contents furthermore the onset of leucite crystallization is marked by a change in 87 sr 86 sr and sio 2 sr isotope ratios and their time related variations as well as the presence of two different trends in some trace element variation diagrams define two distinct modes of magma differentiation magmas evolved along a stratigraphically lower trend at the beginning of the activity whereas they evolved differently along a stratigraphically upper trend later in the volcanic history modelling of geochemical and sr isotope variations indicates that along the lower trend fractional crystallisation was the main evolutionary process whereas along the upper trend mixing between a leucite free magma and a leucite bearing magma occurred during crystallisation the sr isotope compositions of rocks from the early stage of activity at vico suggest mixing between magmas having different petrological affinities a leucite bearing roman type magma and a high potassium calc alkaline magma

an inter laboratory comparison of the electron probe microanalysis of glass geochemistry abstract tephrochronology commonly relies upon grain discrete analysis of glass shards to reveal the subtle geochemical differences between tephras from past explosive volcanic eruptions the use of electron probe microanalysis for this purpose is widely accepted by tephrochronologists it is widely recognised that both precision and accuracy must be maximised and that rigorous standardisation procedures must be followed in this paper the performances of seven northern european electron microprobe centres are compared using a geochemically homogeneous obsidian secondary standard the results reveal that a number of tephra oriented probe centres could benefit from exercises similar to the programme outlined within in particular it is evident that a number of these centres undertaking tephrochronological investigations have generated geochemical data that may be inadequate in terms of distinguishing between tephras inaccuracy in the determination of sodium is seen to be the main difficulty in recent years the application of distal tephrochronology to stratigraphical problems in the northern european quaternary record has become increasingly common geochemical standardisation is essential at an early stage in the development of a regional tephrochronological framework and we hope exercises such as presented here will encourage the production of reliable tephra geochemical data

revised tuning of ocean drilling program site 964 and kc01b mediterranean and implications for the δ18o tephra calcareous nannofossil and geomagnetic reversal chronologies of the past 1 1 myr 1 high resolution color reflectance records of kc01 and kc01b calabrian ridge ionian sea are presented and compared with a modified spliced high resolution color reflectance record of ocean drilling program odp site 964 this comparison revealed that kc01b is characterized by intensive deformation between 27 and 28 5 m piston depth and that some sapropels are tectonically reduced in thickness moreover the piston coring has caused considerable stretching in the top of kc01 and kc01b using a new splice of odp site 964 as guide previous astronomical tuned timescales of kc01b and odp site 964 were evaluated this evaluation resulted in a new sapropel based astronomical timescale for the last 1 1 myr the new timescale implies a much more uniform change in sedimentation rate for the ionian sea cores two prominent excursions to lighter values in the 18o record of the planktonic foraminiferal species globigerinoides ruber occur during marine isotopic stages 12 and 16 applying the new timescale these shifts correspond with maxima in obliquity and are punctuated by minima in the precession cycle they are absent in global ice volume records and are interpreted as reflecting a summer low salinity surface water lens that floats on top of extremely saline intermediate and deep waters at times of the very low sea levels during these glacial periods all biostratigraphic and magnetostratigraphic events found in kc01b and odp site 964 were re dated according to the new timescale and the ages of 33 tephra layers were reviewed the new ages for the calabrian ridge 2 and 3 magnetic events in the brunhes are concordant with minima in the global sint800 composite record derived from worldwide deep sea records of relative paleointensity and have been attributed to the big lost and la palma excursions respectively

an exceptionally thick middle pleistocene tephra layer from epirus greece abstract a newly recognized 2 m thick trachytic volcanic ash deposit from northwestern greece is dated at 374 000 7000 yr and correlated with the middle pleistocene volcanic activity of central italy the deposit represents ash fallout from one of the largest volcanic eruptions in europe of the past 400 000 yr and should provide an important stratigraphic marker within the poorly dated middle pleistocene deposits of italy and greece

invited review hydroclimatic changes in northern levant over the past 400 000 years the levant a transition zone between the temperate mediterranean domain and subtropical deserts is a key area to study the latitudinal migrations of zonal climatic belts in response to glacial interglacial conditions the region underwent large climatic shifts during the late quaternary with dramatic impacts on water resources and human populations this paper presents the unique long term hydro climatic record ca 400 ka from northern levant derived from a sediment core taken from a small tectonic basin of northern lebanon the currently wettest area of the levant combined biotic pollen biologic aquatic remains and abiotic proxies sediment properties carbonate oxygen isotopes reveal relatively high water availability during interglacials and generally drier glacials periods during the past four climate cycles these general trends are in line with pollen records from southeastern and near east mediterranean areas but differ from some paleohydrological records from the southern levant southward migrations of the rain bearing mid latitude westerlies during glacial periods and regional land topography are likely to explain the observed regional climate signatures in addition distinctive climate signatures of the successive wetter drier intervals reflect interactions between global forcing insolation atmospheric greenhouse gas concentration eastern mediterranean sea surface conditions intimately linked to north atlantic climate and to ice sheet and sea ice extent at high northern latitudes land topography and local hydrogeological processes our record brings new benchmarks for understanding the spatial heterogeneity of eastern mediterranean responses to global climate changes

the detailed tephrostratigraphy of a core from the south east black sea spanning the last 60 ka one visible volcanic ash layer and 21 non visible cryptotephra horizons have been identified in the m72 5 25 gc1 core from the south east black sea that spans the last 60 ka glass chemistry suggests that the tephras derive from italian hellenic and turkish sources the visible tephra layer is trachytic in composition and has been correlated to the 39 ka campanian ignimbrite super eruption from campi flegrei caldera italy two cryptotephra layers are associated with eruptions from acigol volcano turkey around the last glacial maximum another is linked to activity at erciyes dagi in the early holocene perikartini or karagullu and a cryptotephra layer near the top of the core correlates to the 3 6k cal a bp minoan marine z2 tephra from santorini thera greece this extends the known dispersal area for all these volcanic ash units many other calc alkaline rhyolite layers preserved in the core are likely to be from central anatolian sources but the lack of detailed proximal data for many of the volcanoes in the region prohibits further correlations the tephrostratigraphy and glass compositional data presented here allow the tephra layers to be used to correlate sedimentary archives across the region and help to extend the mediterranean tephrochronology framework towards the east