constant elevation of southern tibet over the past 15 million years the uplift of the tibetan plateau an area that is 2 000 km wide to an altitude of about 5 000 m has been shown to modify global climate and to influence monsoon intensity mechanical and thermal models for homogeneous thickening of the lithosphere make specific predictions about uplift rates of the tibetan plateau but the precise history of the uplift of the plateau has yet to be confirmed by observations here we present well preserved fossil leaf assemblages from the namling basin southern tibet dated to approximately 15 myr ago which allow us to reconstruct the temperatures within the basin at that time using a numerical general circulation model to estimate moist static energy at the location of the fossil leaves we reconstruct the elevation of the namling basin 15 myr ago to be 4 689 895 m or 4 638 847 m depending on the reference data used this is comparable to the present day altitude of 4 600 m we conclude that the elevation of the southern tibetan plateau probably has remained unchanged for the past 15 myr

degassing history and carbon cycle of the earth from an impact induced steam atmosphere to the present atmosphere abstract the recent theoretical studies on the formation and evolution of the atmosphere and oceans of the earth are reviewed impact degassing during accretion of the earth would probably generate an impact induced steam atmosphere on the proto earth at the end of accretion the steam atmosphere became unstable and condensed to form the proto ocean with almost the present mass of ocean the steam atmosphere would have thus evolved to the proto co2 atmosphere during the earliest history of the earth because co in the proto atmosphere may be photochemically converted to co2 however co2 in the proto atmosphere has decreased with time through the global carbon cycle which may have stabilized the terrestrial environment against an increase in the solar luminosity the continental growth during hadean and archean would therefore have a significant influence on the carbon cycle and the surface temperature it is also suggested that the continental growth is a necessary condition for the terrestrial environment to evolve to the present state both the impact degassing and the subsequent continuous degassing are suggested to have played a major role in the formation and evolution of the atmosphere and ocean in particular most of n2 may have been produced by the impact degassing during accretion and the contribution of the subsequent continuous degassing is at most 10 for n2 as a consequence after the co2 level decreased to less than 1 bar the atmosphere may have been at about 1 bar and composed mainly of n2 for most of the subsequent history of the earth

wet surge deposits at la fossa di vulcano depositional and eruptive mechanisms abstract wet surge deposits of different volcanic cycles of the recent fossa activity at vulcano have been measured on a bed by bed basis with data recorded to millimeter detail the wet surge layers are varicoloured with variable thickness with the most recurrent thickness being about 1 cm the beds consist of fine ash without internal structures textural features include a accretionary lapilli of maximum size of 0 5 cm dispersed thoroughout the layer or forming continuous layers of submillimeter size b vesiculated layers which represent 10 to 65 of the total deposit vesicles have different shapes and smooth walls varying in volume from 1 to 15 20 c soft sediment types of bedding deformation such as gravity flowage ripples load cast and slumps the slope angle has not influenced either the concentration and size of the accretionary lapilli or the shape size and distribution of vesicles only the thickness of the layers decreases with distance from the vent sem investigations show features indicating the hydromagmatic origin of the deposits and stressing the role of the fluid phase noteworthy is the presence of vesiculated grains produced by magmatic exsolution which show chilling effects on the internal walls of the broken bubbles grain size analyses reveal that the layers are not graded and most of the samples have a median size finer than 50 m the grain size distributions are frequently polymodal suggesting several closely timed explosions as all the beds exhibit the same textures grain size and particle morphology a single mechanism can explain their deposition the depositional unit formed at the base of the cloud through the lateral expansion on the ground of a sticky muddy medium consisting of ash and fluid in general each layer lost its plasticity before the deposition of the next layer the deposition occurred in a nearly continuous sequence without periods of rest long enough to permit erosional discontinuity the eruptions are hydromagmatic and occur where magma at least partially fragmented comes into effective contact with subsurface water the process follows a model suggested by wohletz 1983b 1986 developing in more than one fragmentation event in the turbulent surge cloud both severe hydration and alteration of glassy grains and the formation of accretionary lapilli occur

stable isotope based paleoaltimetry abstractthe quantitative estimation of paleoaltitude has become an increasing focus of earth scientists because surface elevation provides constraints on the geodynamic mechanisms operating in mountain belts as well as the influence of mountain belt growth on regional and global climate the general observation of decreasing 18o and 2h values in rainfall as elevation increases has been used in both empirical and theoretical approaches to estimate paleoelevation these studies rely on the preservation of ancient surface water compositions in authigenic minerals to reconstruct the elevation at the time the minerals were forming in this review we provide a theory behind the application of stable isotope based approaches to paleoaltimetry we apply this theory to test cases using modern precipitation and surface water isotopic compositions to demonstrate that it generally accords well with observations examples of the application of paleoaltimetry techniques to himalaya tibet and the andes are discussed

palaeoaltimetry from energy conservation principles a knowledge of past changes in the mean elevations of large continental areas is important for understanding both dynamic processes in the earth s mantle 1 and the evolution of the global climate 2 but virtually all methods for determining palaeoelevations are problematic in part because changes in either elevation or climate can give rise to the same observed geological phenomena 4 ideally palaeoelevations would be inferred directly from estimates of palaeopressure and it has recently been shown 5 that vesicles in basaltic lava flows preserve a record of atmospheric pressure at the altitude of emplacement however the elevations thus obtained have large errors 1 4 km and the method can at present be applied only to lavas that have had a simple emplacement history 5 palaeobotanical methods for estimating palaeoelevation have received much attention 6 12 but they rely on empirical temperature elevation relationships the uncertainties in which are difficult to evaluate for past climates here we describe an alternative palaeobotanical approach based on energy conservation in the atmosphere in which fossil leaf assemblages are used to infer enthalpy rather than temperature this approach is relatively insensitive to palaeoclimate with an expected error in palaeoelevation of 700 m

magnetic fabric and remanent magnetization of pyroclastic surge deposits from vulcano aeolian islands italy abstract tufi di grotte dei rossi inferiori are unwelded fine grained pyroclastic deposits of hydromagmatic origin emplaced between 21 and 11 8 6 ka at vulcano aeolian islands italy by deposition through surges spreading laterally from inside the la fossa caldera in this study the deposit s magnetic properties were investigated and interpreted in terms of eruptive and emplacement dynamics rock magnetism data were supplemented by grain size and textural characteristic analyses as well as scanning electron microscope sem investigations curie point measurements isothermal remanent magnetization and microprobe analyses showed that magnetization is carried by low ti titanomagnetite the size of the grains ranges from about 20 to 300 micrometres their shape from equidimensional to highly elongated the magnetic fabric is typical of fine grained pyroclastics foliation is well developed and in most sites lineation is directed towards the source area of the la fossa caldera the remanent magnetization consists of two components whose blocking temperature spectra partially overlap the direction of the low temperature component is close to that of the axial dipole and consistent with the palaeosecular variation curve for the aeolian islands the high temperature component is systematically shallowed and close to the direction of the magnetic lineation the overall results suggest that the high temperature component was acquired before and the low temperature component after the actual deposition of grains immediately after eruption the grains cooled and moved as free particles in the turbulent cloud during the expansion of the surge flows those particles with high blocking temperatures acquired a thermal remanence they were then deposited and shear at the very base of the flow oriented them and imprinted the rock s fabric and high temperature magnetization component volcanological and magnetic data suggest turbulent transportation and traction deposition of particles finally the rock cooled down and acquired the low temperature magnetization according to this model remanence acquisition in pyroclastic rocks deposited at temperatures lower than the curie point of their ferromagnetic grains depends on both the fluid dynamic forces and cooling history and must therefore be more complex than in pyroclastics deposited at higher temperatures such as welded ignimbrites

late cenozoic uplift of mountain ranges and global climate change chicken or egg the high altitudes of most mountain ranges have commonly been ascribed to late cenozoic uplift without reference to when crustal thickening and other tectonic processes occurred deep incision and recent denudation of these mountain ranges abundant late cenozoic coarse sediment near them and palaeobotanical evidence for warmer climates where high mountain climates today are relatively cold have traditionally been interpreted as evidence for recent uplift an alternative cause of these phenomena is late cenozoic global climate change towards lower temperatures increased alpine glaciation a stormier climate and perturbations to humidity vegetative cover and precipitation

new unspiked k ar ages of volcanic rocks of the central and western sector of the aeolian islands reconstruction of the volcanic stages abstract a geochronological study of the filicudi salina lipari and vulcano islands aeolian archipelago using the unspiked potassium argon technique provides new age data which combined with stratigraphic correlation better constrain the temporal evolution of volcanism the unspiked k ar age of the oldest exposed lavas on filicudi 219 5 ka is significantly younger than the previous estimation of 1 02 ma in the general context of aeolian volcanism this new date suggests that the volcanism of the western sector of the aeolian archipelago is younger than previously thought geochronological data point out on the rapid transition from calc alkaline to potassic volcanism the distribution of the k ar ages within the salina lipari vulcano group shows that the volcanism started on lipari and propagated over time northward on salina and southward on vulcano geochronological and geophysical data suggest that the onset of volcanism in the central sector of the aeolian arc may be due to a mantle upwelling structure located below lipari a change in the style of the eruptions occurred in the salina lipari vulcano system at about 100 ka from the present low energy magmatic eruptions occurred between 188 and about 100 ka from about 100 ka to the present higher energy eruptions and low energy events due to magma water interaction also occurred this change in the style of activity together with the appearance of evolved products i e rhyolites during the last 50 ka is consistent with the formation of magmatic reservoirs located at shallower depth with respect to those of the 188 100 ka period the new geochronological data and available petrological models reveal that a change in the deep source of the primary magmas occurred in a relatively short time interval

unroofing the ladakh batholith constraints from autochthonous molasse of the indus basin nw himalaya the indus molasse records orogenic sedimentation associated with uplift and erosion of the southern margin of asia in the course of ongoing india eurasia collision detailed field investigation clarifies the nature and extent of the depositional contact between this molasse and the underlying basement units we report the first dataset on detrital zircon u pb ages hf isotopes and apatite u pb ages for the autochthonous molasse in the indus suture zone a latest oligocene depositional age is proposed on the basis of the youngest detrital zircon u pb age peak and is consistent with published biostratigraphic data multiple provenance indicators suggest exclusively northerly derivation with no input from india in the lowermost parts of the section the results provide constraints on the uplift and erosion history of the ladakh range following the initial india asia collision supplementary material method description sample locations figures s1 and s2 and tables s1 to s3 are available at https doi org 10 6084 m9 figshare c 4858848

transition from calc alkaline to potassium rich magmatism in subduction environments geochemical and sr nd pb isotopic constraints from the island of vulcano aeolian arc the problem of mantle metasomatism vs crustal contamination in the genesis of arc magmas with different potassium contents has been investigated using new trace element and sr nd pb isotopic data on the island of vulcano aeolian arc the analysed rocks range in age from 120 ka to the present day and cover a compositional range from basalt to rhyolite of the high k calc alkaline hkca to shoshonitic sho and potassic ks series older vulcano products 30 ka consist of hkca sho rocks with sio2 48 56 they show lower contents of k2o rb and of several other incompatible trace element abundances and ratios than younger rocks with comparable degree of evolution 87sr 86sr ranges from 0 70417 to 0 70504 and increases with decreasing mgo and compatible element contents 206pb 204pb ratios display significant variations 19 31 to 19 76 and are positively correlated with mgo 143nd 144nd 0 512532 0 512768 207pb 204pb 15 66 15 71 and 208pb 204pb 39 21 39 49 overall geochemical and isotopic data suggest that the evolution of the older series was dominated by assimilation fractional crystallisation afc with an important role for continuous mixing with mafic liquids magmas erupted within the last 30 ka consist mostly of sho and ks intermediate and acid rocks with minor mafic products except for a few acid rocks they display moderate isotopic variations e g 87sr 86sr 0 70457 0 70484 206pb 204pb 19 28 19 55 but 207pb 204pb 15 66 15 82 which suggest an evolution by fractional crystallisation or in some cases by mixing with little interaction with crustal material the higher sr isotopic ratios 87sr 86sr 0 70494 0 70587 of a few low volume intermediate to acid rocks support differentiation by afc at shallow depths for some magma batches new radiogenic isotope data on the aeolian islands of alicudi and stromboli as well as new data for lamproites from central italy are also reported in order to discuss along arc compositional variations and to evaluate the role of mantle metasomatism geochemical and petrological data demonstrate that the younger k rich mafic magmas from vulcano cannot be related to the older hkca and sho ones by intra crustal evolutionary processes and point to a derivation from different mantle sources the data from alicudi and stromboli suggest that even though interaction between magma and wall rocks of the calabrian basement during shallow level magma evolution was an important process locally a similar interpretation can be extended to the entire aeolian arc

mechanisms of hydrovolcanic pyroclast formation grain size scanning electron microscopy and experimental studies pyroclasts produced by explosive magma water interactions are of various sizes and shapes data from analysis of over 200 samples of hydrovolcanic ash are interpreted by comparison with experimentally produced ash grain size and scanning electron microscopy sem reveal information on the formation of hydrovolcanic pyroclasts strombolian explosions result from limited water interaction with magma and the pyroclasts produced are dominantly centimeter sized with increasing water interaction hydrovolcanism increases in explosivity to surtseyan and vulcanian activity these eruptions produce millimeter to micron sized pyroclasts the abundance of fine ash 63 m diameter increases from 5 to over 30 percent as water interaction reaches an explosive maximum this maximum occurs with interactions of virtually equal volumes of melt and water five dominant pyroclast shape types determined by sem result from hydrovolcanic fragmentation 1 blocky and equant 2 vesicular and irregular with smooth surfaces 3 moss like and convoluted 4 spherical or drop like and 5 plate like types 1 and 2 dominate pyroclasts greater than 100 m in diameter types 3 and 4 are typical of fine ash type 5 pyroclasts characterize ash less than 100 m in diameter resulting from hydrovolcanic fragmentation after strong vesiculation fragmentation mechanisms observed in experimental melt water interactions result from vapor film generation expansion and collapse fragments of congealed melt are products of several alternative mechanisms including stress wave cavitation detonation waves and fluid instability mixing all result in rapid heat transfer these mechanisms can explain the five observed pyroclast shapes stress wave fracturing cavitation of the melt results from high pressure and temperature gradients at the melt water interface simultaneous brittle fracture and quenching produces type 1 pyroclasts type 2 develops smooth fused surfaces due to turbulent mixing with water after fracture and before quenching fluid instabilities promote turbulent mixing of melt and water and produce fine ash this kind of fragmentation occurs during high energy explosions the increased melt surface area due to fine fragmentation promotes high efficiency heat exchange between the melt and water shapes of resulting pyroclasts are determined by maximum surface area type 3 and surface tension effects type 4 type 5 pyroclasts result from nearly simultaneous vesicle burst and melt water fragmentation

paleobotanical evidence for high altitudes in nevada during the miocene leaf physiognomy provides estimates of environmental parameters including mean annual enthalpy which is a thermodynamic parameter of the atmosphere that varies with altitude analyses of 12 mid miocene floras from western nevada indicate that this part of the basin and range province stood 3 kilometers above sea level at 15 to 16 million years ago which is 1 to 1 5 kilometers higher than its present altitude much if not all of the collapse to present day altitudes seems to have been achieved by 13 million years ago the crust in much of this area has been extended and thinned throughout the past 40 to 50 million years and the isostatic balance of a thinning crust requires subsidence not uplift as suggested by previous paleobotanical work

quantitative experiments on phreatomagmatic explosions abstract an experimental set up for controlled generation of thermal explosions fuel coolant interactions has been built by an interdisciplinary research group of volcanologists physicists and engineering scientists the tee haus thermal explosion experiment during the last 3 years more than 500 experimental runs were performed aim of the project was not to build a mini volcano but to produce igniteable mixtures of water and hot melt on a small scale in order to investigate basic physical aspects such small scale mixtures however most probably also occur during phreatomagmatic events in nature mixtures of water and magma on a large scale may be modelled by combination of small elements earlier experimental studies of thermal explosions were carried out with the use of metal melts nearly exclusively therefore a carbonate melt approx 0 3 kg of 1 1 mass ratio na2co3 k2co3 was used for initial experimental series because of easy handling and more magma similarity by injection of water into this melt explosive mixtures were produced and ignited self triggering explosive interactions occurred in a wide melt temperature range 720 to 1040 c at melt temperatures exceeding 1000 c co2 increasingly degassed presence of non condensible gas bubbles in the melt strongly reduced the explosivity the intensity of explosions only slightly increased with higher melt temperatures but strongly increased with higher water injection velocities because of more intensive mixing a minimum injection velocity was found to be approx 0 7 m s 1 experiments with silicate melts derived from diverse remelted volcanic rocks were carried out with a slightly modified set up explosions were ignited by an additional trigger a shock wave of approx 8 j in volcanic systems shock waves of this magnitude are abundant volcanic tremor etc strong explosions with silicate melts were produced at melt temperatures between 1350 and 1750 c the produced explosions exerted repulsion forces of up to 24 000 n with a typical pulse duration of 1 ms carbonate melt resp 1 5 ms silicate melts the ejection velocity was found to be in a range between 200 and 400 m s 1 explosion energy values up to 500 j were calculated the maximum explosion pressure was calculated to be in the range between 10 and 100 mpa only part of the melt so called interactive melt reacts explosively with injected water most of the melt is passively ejected by and after the thermal explosion different fragmentation processes result in specific grain size and grain shape populations that can be distinguished from each other particles resulting from the fine fragmentation process that precedes and causes the thermal explosion are characterized by angular to subrounded shapes and grain sizes ranging from 20 m to 180 m the amount of interactive melt is proportional to the intensity of the explosion the maximum amount of water vapourized at the explosive interaction so called interactive water was estimated thus the water melt mass ratio for explosive interactions could be calculated the values range between 1 25 and 1 35 carbonate melt resp between 1 6 and 1 25 silicate melts

oxygen isotopes and sea level from the time that detailed oxygen isotope records derived from foraminifera living in the constant temperature environment of the abyssal ocean became available there has been a discrepancy between the ice volume record that these records imply and that derived from the altitude of dated coral terraces around the world here we re examine the data and conclude that the temperature of the abyssal ocean has been an actively varying component of the climate system

quantification of uncertainties in fossil leaf paleoaltimetry does leaf size matter 1 the utility of multivariate foliar physiognomy specifically the climate leaf analysis multivariate program clamp to yield reliable estimates of enthalpy and hence paleoelevation has been demonstrated by comparison with other proxies yet concerns have arisen regarding uncertainties arising from 1 apparent ambiguities in the scoring regime and 2 the way leaf size is scored regarding the first concern scoring ambiguities are examined by reporting on scoring tests with novice users and interlaboratory comparisons the uncertainties were found to be less than those arising from the statistical methodology underpinning clamp in respect to the second concern the effect of removing all size data both from modern test sites and fossil data was tested specifically the effect of removing leaf size data from the 15 ma namling data set from south central tibet was investigated removal of all size data from modern sites demonstrated that size data contributes little to estimates of mean annual temperature and enthalpy similarly the removal of leaf size information from the namling data set alone but with calibration unchanged and from both the namling site and calibration sites this time with recalibration still yield paleoelevation estimates that have been independently matched by oxygen isotope techniques moreover the removal of all leaf size information results in only small increases in uncertainty 52 m

the influence of a grain shape fabric on the mechanical behaviour of rock salt results from deformation experiments abstract in order to assess the effect of shape preferred orientation spo of halite grains on deformation of rock salt ductile plane strain deformation experiments have been conducted natural halite cubes with and without an spo from the asse mine of northern germany were deformed at 345 c atmospheric pressure and a strain rate of 10 7 s 1 the spo was oriented at different angles s 0 45 and 90 to the main shortening direction z the sample is confined in the y direction and can freely move to the principal stretching direction x most of the strain was accommodated by dislocation creep the qualitative analysis of the stress strain data shows the clear influence of the spo on the mechanical data at a shortening strain of ca 10 the samples with 0 and 45 are weaker than the samples without an spo in contrast the sample with 90 is stronger than the samples without an spo a new spo is formed in all samples with the long axis of the grain shape fabric being subparallel to the principal stretching axis x at these larger shortening strains the samples show similar strength with an exception of the 90 oriented sample that is still stronger than the samples without an spo even though the experimental set up has to be improved to obtain quantitative results on the influence of spo on mechanical strength of rock salt the results show that the spo of rock salt likely has to be taken into account when building a repository for nuclear waste and could have an effect on the stability of caverns

rapid uplift of the altiplano revealed through 13c 18o bonds in paleosol carbonates the elevation of earth s surface is among the most difficult environmental variables to reconstruct from the geological record here we describe an approach to paleoaltimetry based on independent and simultaneous determinations of soil temperatures and the oxygen isotope compositions of soil waters constrained by measurements of abundances of 13 c 18 o bonds in soil carbonates we use this approach to show that the altiplano plateau in the bolivian andes rose at an average rate of 1 03 0 12 millimeters per year between 10 3 and 6 7 million years ago this rate is consistent with the removal of dense lower crust and or lithospheric mantle as the cause of elevation gain

strength of jointed rock masses jointed rock masses comprise interlocking angular par ticles or blocks of hard brittle material separated by discontinuity surfaces which may or may not be coated with weaker materials the strength of such rock masses depends on the strength of the intact pieces and on their freedom of movement which in turn depends on the number orientation spacing and shear strength of the discontinuities a complete understanding of this problem presents formidable theoretical and experi mental problems and hence simplifying assumptions are required in order to provide a reasonable basis for estimating the strength of jointed rock masses for engineering design purposes this paper summarizes some of the basic information upon which such simplifying assumptions can be made a simple empirical failure criterion is presented and its application in engineering design is illustrated by means of a number of practical examples des masses jointives de rochers comprennent des particules angulaires enchevetrees ou des

pyroclastic surges of the pleistocene monte guardia sequence lipari island italy depositional processes the 20 16 ka monte guardia sequence of lipari island southern italy is a complex succession of silicic pyroclastic surge deposits produced in part by hydromagmatic explosions near sea level most surges were directed to the east north east and north of the vent and climbed the 12 southern slopes of monte sant angelo in the central part of the island a series of thin distinctive key bed sets containing oxidized ash and accretionary lapilli allow a detailed correlation of sections and the lateral tracing of deposits of single pyroclastic surges across the island facies analysis reveals that the proximal to distal facies changes are different from those suggested by a previous study based on a statistical approach to lateral facies distribution single dry surge deposits evolve downcurrent from 1 beds of disorganized medium to coarse grained lapilli containing scattered blocks to 2 bipartite disorganized stratified beds of fine to coarse grained lapilli with ash matrix to 3 dunes formed of coarse grained ash to medium grained lapilli to 4 planar beds of fine grained lapilli this facies sequence is similar to published models for some korean surge deposits and records decelerating surges which experienced a downflow decrease in turbulence particle concentration and suspended load fall out rate and an increase in traction processes as the monte guardia surges climbed the opposing slopes of monte sant angelo they bifurcated into eastern and western tongues which experienced rapid deceleration leading to a rapid downcurrent thinning and fining of the surge deposits two fluid dynamical approaches suggest that monte guardia surges travelled at speeds of more than 75 85 m s 1 before climbing monte sant angelo flows with this vigour and distribution are capable of destroying animal and plant populations on lipari

influence of andean uplift on climate and paleoaltimetry estimates article i nfo article history recent elevation reconstructions of the andean plateau suggest a rapid 2 5 1 0 km rise of the central andes between 10 and 6 ma this rapid rise has been attributed to a catastrophic removal of a dense lithospheric mantle root beneath the andes however these findings are based on the assumption that climate did not change during deposition of paleoaltimetry proxies here we evaluate south american climate change due to andean uplift and its influence on interpretations of plateau elevation from climate sensitive paleoaltimetry data a series of experiments are presented using the regcm3 regional general circulation model rcm to characterize changes in andean precipitation amount surface temperature and wind direction vapor source as a function of changing plateau elevation results indicate that south american and andean climate changed significantly in response to plateau growth more specifically rising of the plateau results in up to a 900 mm increase in rainy season december january february precipitation over the plateau plateau uplift also results in a decrease in non adiabatic surface temperature of up to 6 5 c in addition to adiabatic cooling directly related to elevation change through the lapse rate finally the prevailing wind direction and the vapor source for precipitation switches from the south pacific ocean to the equatorial atlantic as plateau elevation increases above of its present day elevation taken together these changes in paleoclimate would have substantially depleted the oxygen isotopic concentration of paleoprecipitation through the cenozoic unless this climatic effect is taken into consideration paleoaltimetry reconstructions based on stable isotope methods may overestimate the rapid rise of the andes by up to several kilometers we conclude that some or all of the apparent rapid rise of the andean plateau from paleoaltimetry data could be an artifact of large changes in paleoclimate

predicting the response of leaf stomatal frequency to a future co 2 enriched atmosphere constraints from historical observations the majority of the water flux from the earth s land surface to the atmosphere passes through the tiny pores stomata in the leaves of land plants the maximum conductance to diffusion of the leaves determined by the number and geometry of stomata has a profound effect on the terrestrial water and energy balance among tree species there is ever increasing evidence that anthropogenic increase in atmospheric co2 concentrations results in a decrease in stomatal frequency the rate of historical co2 responsiveness of individual tree species can be used to calibrate empirical models of non linear sigmoid stomatal frequency response to co2 increase modelled response curves for european tree birches betula pendula betula pubescens and durmast oak quercus petraea predict different response limits to co2 increase 350 and 400 ppmv respectively indicating that non linear stomatal frequency responses may vary from one tree species to another information on a wider selection of species is needed but the models suggest that the maximum effect of anthropogenic co2 increase on stomatal frequency has already been reached further research is required to establish the effect of rapidly declining response rates on future stomatal conductance of the ecologically contrasting trees of boreal temperate subtropical and tropical forests

petrology and geochemistry of volcanic rocks from the island of panarea implications for mantle evolution beneath the aeolian island arc southern tyrrhenian sea abstract major trace element and radiogenic isotope sr nd pb data are reported for a suite of rocks from the panarea volcano a large structure that is largely hidden below sea level and outcrops only as a group of small islands between lipari vulcano and stromboli in the eastern aeolian arc the exposed rocks mostly consist of high potassium calc alkaline hkca andesites dacites and some rhyolites shoshonitic basalts have been collected from submarine centres mafic calc alkaline ca rocks occur as thin layers of late erupted strombolian scoriae major and trace element data are scattered but define generally linear trends on inter element diagrams sr isotope ratios do not display significant increase with evolution although rough positive trends of 87sr 86sr versus sio2 and rb sr can be recognised within some units the mafic rocks display varying enrichment in potassium from ca to shoshonitic compositions and are characterised by variable abundances of incompatible trace elements which increase with potassium there is an increase of 87sr 86sr ratios and a decrease of 143nd 144nd and 206pb 204pb ratios from ca to hkca and shoshonitic mafic rocks the scattered and incomplete nature of the outcrops make it difficult to constrain magmatic evolution at panarea geochemical and isotopic data suggest that afc and mixing were important evolutionary processes however geochemical modelling does not support the possibility that the first order compositional variations observed in the mafic rocks are the result of these processes and suggests a genesis in a heterogeneous mantle source recent studies have highlighted strong differences in terms of incompatible trace element ratios and isotopic signatures between the western central and the eastern aeolian arc rocks from the western islands alicudi filicudi salina vulcano have typical magmatic arc geochemical signatures and relatively unradiogenic sr isotope compositions by contrast the eastern island of stromboli has a more radiogenic sr isotope signature and shows trace element abundances and ratios that are intermediate between arc and intraplate compositions panarea mafic rocks have geochemical and isotopic signatures that are intermediate between those observed in the two sectors of the arc the late erupted ca scoriae of panarea have trace element and isotopic compositions similar to those of the mafic rocks from the western islands of filicudi and alicudi whereas the hkca and shoshonitic mafic rocks have isotopic and trace element signatures that are closer to those of stromboli this reflects the particular position of panarea which is sited midway between the western central arc and stromboli according to some recent views subduction of the ionian sea plate is actively occurring beneath the eastern aeolian arc with rollback of the subduction zone toward the southeast the tindari letoianni malta escarpment fault zone is considered to be the boundary between the active subducting plate in the east and the african plate and western aeolian arc in the west it is suggested that the rollback of the ionian plate generated inflow of mantle material from below the western arc into the mantle wedge above the subducting ionian slab this situation generated a hybrid mantle beneath panarea which resulted in a mixture of western type and resident eastern arc mantle materials the latter had a composition akin to the source of stromboli magmas early hkca and shoshonitic magmatism tapped such a hybrid source whereas the younger ca activity has been derived from melting of unmodified western type mantle material the late eruption of ca rocks with a composition similar to western arc can be explained by assuming that a continuing inflow process had increased the amount of western type mantle with time thus favouring the late appearance of ca magmas this hypothesis accounts for the overall decrease of potassium with time which is the opposite of the trend observed in other aeolian islands

quantitative uncertainty analyses of ancient atmospheric co2 estimates from fossil leaves the relationship between atmospheric co 2 and ancient climate is of fundamental importance for gauging the climate sensitivity of the earth system to a changing co 2 regime one of the most widely adopted paleobiological co 2 proxies for reconstructing earth s atmospheric co 2 history exploits the inverse relationship between leaf stomatal index the fraction of leaf epidermal cells that are stomatal structures and atmospheric co 2 however fossil leaf based co 2 reconstructions make a prioii assumptions about the form of the empirical relationship between si and co 2 required for transfer functions and have failed to correctly propagate error terms these effects can translate into erroneous interpretations that undermine the value of the proxy here we report the development and application of a rigorous generalized statistical framework overcoming these limitations that generates probability density functions for each atmospheric co 2 estimate the utility of our statistical tools is demonstrated by showing how they revise earlier atmospheric co 2 estimates from fossil cuticles of ginkgo and metasequoia trees during the early eocene and middle miocene warm periods upwards by 150 to 250 ppm to 450 to 700 ppm the revised co 2 reconstructions therefore help to resolve the paradox of warm paleogene and neogene greenhouse climates co existing with near present day levels of co 2 and support the emerging view from independent paleoclimate studies for a high climate sensitivity of the earth system the statistical tools presented are sufficiently versatile to permit their use in other investigations of paleoco 2 estimates from fossil leaves

stomatal response of swordfern to volcanogenic co2 and so2 from kilauea volcano 1 the experimentally determined relationship between atmospheric pco2 and plant stomata has been used to interpret large but transient changes in atmospheric composition such as may have resulted from the eruptions of flood basalt however this relationship has not been tested in the field i e in the vicinity of active volcanoes to examine the specific effects of volcanogenic emissions moreover the interpretation of paleoatmospheric pco2 from fossil stomatal data assumes that the stomatal response resulted solely from variation in pco2 and ignores the potential effect of outgassed so2 we hypothesize that volcanogenic so2 also has a significant effect on leaf stomata and test this hypothesis by measuring the stomatal index of the common swordfern nephrolepis exaltata in the plumes of the actively outgassing vents of kilauea volcano we find that compared to control locations stomatal index is lowest at sample sites in the plume of halema uma u crater where concentrations of both co2 and so2 are much higher than background however sites located directly in the plume of pu u o o where so2 levels are high but co2 levels are not also yield low values of stomatal index we propose that shifts in the stomatal index of fossil leaves may record transient atmospheric increases in both so2 and co2 such as may be caused by eruptions of flood basalts calculations of pco2 based on stomatal frequency are likely to be exaggerated

velocity resistivity versus porosity permeability inter relations in dead sea salt samples abstract this study is intended to investigate dead sea ds salt porosity permeability hydraulic conductivity inter relations as well as their relationship to geophysical parameters such as compression and shear wave velocities vp vs respectively and specific resistivity x in laboratory and field conditions to estimate representative properties affected by porosity changes during sinkhole development some 41 salt samples were subjected to porosity measurements and 25 samples were tested to reveal hydraulic conductivity the salt of the coastal dead sea area composed of halite is revealed in 10 200 10 800 year old layers the halite commonly appears as rock salt the 7 30 m thick salt unit is located below the groundwater table at depths of 20 50 m from the surface salt layers are very conductive hydraulically and water saturated with the ds brine is of very high salinity with total dissolved solids tds of 340 380 g l two types of salt have been studied crystalline transparent salt cts distributed along the entire ds s western shore and white massive salt wms found locally along the southern ds and along the dike salt porosity measured in samples varies in the range of 5 21 whereas hydraulic conductivity varies between 10 5 to 10 9 m s density is changed in the range of 1681 2116 kg m 3 in wet samples and between 1638 and 2106 kg m 3 in dry samples during the laboratory testing of ds salt samples we have measured the following geophysical parameters vp 3700 4460 m s vs 1900 2620 m s and x 2 100 m on the other hand our previous field studies based on s wave seismic refraction surface wave prospecting swp and transient electromagnetic tem methods have shown that in in situ salt velocities vp range between 2900 and 4240 m s vs varies between limits of 750 m s to more than 1650 m s and x is of 0 8 to 2 5 m these values are considerably less than the analogous parameters measured in the salt samples the same conclusion has been made from the comparison of salt sample properties and borehole logging both studied by ultrasonic method geophysical data testify that in situ porosity calculated using relationships obtained during this study exceeds those in the laboratory samples especially in zones of heightened voidness where it is 25 hydraulic conductivities in the same zones exceed a value of 10 6 m s and even 10 5 m s we expect that in larger salt volumes these parameters can yet increase

computer simulation of transport and deposition of the campanian y 5 ash analyses of grain size and modal composition of the campanian tuff ash layer y 5 from 11 deep sea cores have been carried out this layer represents ash fall that has been correlated with the 38 000 y b p campanian ignimbrite thunell et al 1979 a deposit formed by the largest eruption documented in the mediterranean region during the late pleistocene barberi et al 1978 the bulk deposit is bimodal in grain size and dominated by glass shards the calculated mean grain size of the coarse mode of the individual size distributions decreases with distance from the source and progressively approaches a near constant fine mode of approximately 13 microns distal samples are unimodal in grain size these data combined with a set of vertical profiles of wind 10 year average have been used as input to a computer model that simulates fallout of tephra modelling indicates that the downwind variation of grain size of the coarse mode can be accurately reproduced with transport of ash between 5 and 35 km the observed fine mode of the deposit cannot however be generated by transport of ash as individual particles at these elevations such transport would result in deposition of virtually all of the fine ash beyond the studied area deposition of fine ash within the studied distance of 1600 km from source can only occur by fallout as particle aggregates from a high eruption plume or as individual particles from co ignimbrite ash clouds with a maximum elevation of 3 km the large volume of ash in the fine mode 70 wt and the irregularity in azimuth of low level winds argue against major low level transport of co ignimbrite ash rather the ash may have been derived from both a plinian eruption column and high altitude clouds of co ignimbrite ash with settling of fine ash as particle aggregates

onset of the persistent activity at stromboli volcano italy stromboli known worldwide as the lighthouse of the mediterranean is commonly believed to have been in a state of persistent activity for the past 2000 2500 years however historical sources older than 1000 a d are not accurate enough to assess if the activity of the volcano was exactly the same as we see at present in order to attempt to identify the onset of the present eruptive regime and assess if it has been maintained with the same characteristics through time stratigraphic and radiometric studies of the recent tephra deposits were undertaken up to 4 m deep stratigraphic trenches dug at a height of approximately 500 m on the ne flank of the volcano exposed a conformable tephra pile containing charcoal fragments one of the most interesting finds was the discovery of a 7 cm thick weathered bed rich in organic matter thin palaeosol approximately 3 m below the surface the sequence underneath the palaeosol consists of decimetre thick lapilli fallout beds alternating with ash deposits bearing small charcoals with calibrated ages of between the fourth century b c and the first century a d the sequence above the palaeosol is charcoal free and consists of coarse ash deposits with discrete centimetre thick lapilli fallout beds composed of crystal poor golden pumice and subordinate crystal rich black scoriae similar to scoria pumice pairs emitted during the more energetic explosions of the present day activity the data collected indicate that between the third and seventh centuries a d after a period of quiescence the activity resumed with an eruptive style identical to the present one we conclude that the lighthouse of the mediterranean actually began its activity in a period much later than previously thought

identifying magma water interaction from the surface features of ash particles the deposits from explosive volcanic eruptions those eruptions that release mechanical energy over a short time span1 are characterized by an abundance of volcanic ash2 3 this ash is produced by fragmentation of the magma driving the eruption and by fragmenting and ejecting parts of the pre existing crust host rocks interactions between rising magma and the hydrosphere oceans lakes and ground water play an important role in explosive volcanism4 5 because of the unique thermodynamic properties of water that allow it to very effectively convert thermal into mechanical energy although the relative proportion of magma to host rock fragments is well preserved in the pyroclastic rocks deposited by such eruptions it has remained difficult to quantitatively assess the interaction of magma with liquid water from the analysis of pyroclastic deposits2 3 4 5 here we report the results of a study of natural pyroclastic sequences combined with scaled laboratory experiments we find that surface features of ash grains can be used to identify the dynamic contact of magma with liquid water the abundance of such ash grains can then be related to the water magma mass ratios during their interaction

a geotechnical study of evaporitic lacustrine sediments in the saline environment of the dead sea area this paper is the third by the authors relating to the geotechnical properties of the evaporitic lacustrine sediments of the saline environment in the dead sea area the earlier papers identified difficulties involved in establishing the water content of sediments in a saline environment a different approach was adopted whereby fluid content rather than water content was used to define geotechnical properties the present paper expands on the geological background presented in the previous papers and discusses additional geotechnical aspects of the materials behavior the three major sediment types encountered in the region are fluvial granular soil cohesive lime carbonate deposits and granular to massive halite sediments the granular soils composed predominantly of sand and pebbles of dolomite with minor chert and limestone have gradations which vary widely both with depth and laterally shear wave velocities are higher than those estimated from common existing correlations with standard penetration test spt blow counts while compression indices cc and cyclic shear response of the saturated lime carbonates are consistent with behavior of clay soils their effective friction angle of about 34 on average is significantly higher than that of clays the geotechnical properties of the rock salts encountered in the region are shown to be intimately related to the extent of diagenesis and burial with very significant difference between the younger more porous deposits of holocene age and the older mt sdom diapiric salt wall of upper miocene age the latter are seen to have properties consistent with those of older rock salt deposits at greater depths reported in the literature

habitat responses of fossil plant species to palaeoclimate possible interference with co2 abstract one important tool for palaeoclimate reconstruction uses climate space data of extant species representing the nearest living relatives of fossil taxa under the assumption of taxon specific climate demands remaining unchanged through time this is problematic because the calibration of these proxies is based on current vegetation that has grown under current co2 atmospheric co2 may interfere with taxon specific climate demands particularly water availability because stomatal conductance is negatively correlated with co2 in order to assess direct effects of co2 on gas exchange results of numerous experimental studies are available to provide benchmark data experiments will however always provide data which are restricted to response ranges that living plants are able to express simulation models of plant gas exchange offer additional possibilities to explore the influence of co2 on gas exchange and to consider evolutionary adaptation to gas exchange in this study the potential effects of a changing co2 level on photosynthesis performance under simultaneously changing water availability and temperature is evaluated by using a model based on optimized gas exchange including different scenarios of photosynthesis regulation that may result from evolutionary adaptation the results illustrate the impact of changing co2 on water and temperature demands under these various conditions indicating 1 a particularly substantial influence of co2 under low co2 380 ppm a decreasing influence under further increasing co2 and 3 the relevance of possible evolutionary adaptation of the photosynthetic machinery to a changing co2 level downregulation of photosynthesis for instance leads to a distinctly enhanced response of gas exchange to increasing co2 particularly under low to moderate levels 180 ppm 380 ppm changes in atmospheric co2 therefore adds an additional source of uncertainty to those already considered for nlr based methods it may however also offer new possibilities for palaeoecophysiological research

timing of colorado plateau uplift initial constraints from vesicular basalt derived paleoelevations we have developed a technique for measuring paleoelevation on the basis of the vesicularity of basaltic lava flows we are currently applying this technique to determine the timing and extent of cenozoic uplift of the colorado plateau because the technique measures paleoatmospheric pressure it is not subject to uncertainties stemming from the use of proxies that depend on environmental factors other than elevation alone vesicular lavas preserve a record of paleopressure at the time and place of lava emplacement because the difference in internal pressure in bubbles at the base and top of a lava flow depends on atmospheric pressure and lava flow thickness the modal size of the vesicle bubble population is larger at the top than at the bottom this leads directly to paleoatmospheric pressure and thus elevation because the thickness of the flow can easily be measured in the field and the vesicle sizes can be measured in the laboratory on the colorado plateau volcanic fields are generally found around the margins of the plateau basaltic lavas range in age from 0 to 23 ma present elevations range from 1 7 km to 3 3 km samples were collected from lava flows in the areas of marysvale springerville grand mesa and the san juan mountains and analyzed to determine the timing and extent of uplift the analysis of the samples using x ray computed tomography imaging and our numerical techniques for determining vesicle population statistics indicate uplift of 350 2200 m depending on age there is a clear relationship between age and amount of uplift original elevation subtracted from present elevation the results indicate slow uplift of 40 m m y between 25 ma and 5 ma only 800 m of uplift during that time and rapid uplift of 220 m m y since 5 ma 1100 m during that time these results reconcile the long standing controversy between interpretations of ancient versus recent uplift by providing an uplift history curve for the colorado plateau

stomatal evidence for a decline in atmospheric co2 concentration during the younger dryas stadial a comparison with antarctic ice core records a recent high resolution record of late glacial co2 change from dome concordia in antarctica reveals a trend of increasing co2 across the younger dryas stadial gs 1 these results are in good agreement with previous antarctic ice core records however they contrast markedly with a proxy co2 record based on the stomatal approach to co2 reconstruction which records a ca 70 ppm mean co2 decline at the onset of gs 1 to address these apparent discrepancies we tested the validity of the stomatal based co2 reconstructions from kru akenes by obtaining further proxy co2 records based on a similar approach using fossil leaves from two independent lakes in atlantic canada our late glacial co2 reconstructions reveal an abrupt ca 77 ppm decrease in atmospheric co2 at the onset of the younger dryas stadial which lagged climatic cooling by ca 130 yr furthermore the trends recorded in the most accurate high resolution ice core record of co2 from dome concordia can be reproduced from our stomatal based co2 records when time averaged by the mean age distribution of air contained within dome concordia ice 200 to 550 yr if correct our results indicate an abrupt drawdown of atmospheric co2 within two centuries at the onset of gs 1 suggesting that some re evaluation of the behaviour of atmospheric co2 sinks and sources during times of rapid climatic change such as the late glacial may be required copyright 2002 john wiley sons ltd journal of quaternary science

the geology of vertical movements of the lithosphere an overview defining and quantifying horizontal movements of the earth s crust has been a common activity for geoscientists during the last decades due to the success of structural geology in measuring magnitudes of shortening or extension via balanced cross sections and strain analysis coupled with the popularization of continental drift and plate tectonics theory on the larger scale on the other hand vertical movements of rocks or of the surface of the earth although perceived for over two centuries have been more elusive because of the smaller magnitude of translations the difficulties in finding unambiguous markers and because more often their characterization requires the concurrence of integrated approaches some of them recently developed downward movements i e subsidence associated with the formation of sedimentary basins are better quantified and understood but often not coupled with the areas experiencing upward vertical movements over the past decades considerable progress has beenmade in the understanding and quantification of vertical motions of the lithosphere and in particular of the earth s surface thanks to the implementation of new tectonic geomorphologic geochemical and geophysical techniques largely motivated by the strong implications of uplift and subsidence for landscape and environmental issues in addition there is an increased perception that areas experiencing upward and downwardmovements mountains and basins should be looked at as parts of a single tectonic geomorphic and sedimentologic system a significant number of challenges remain to be addressed an inspection of the recent literature clearly indicates that the geology of vertical movements is a field of very active multidisciplinary research the esf sponsored topoeurope initiative with its national counterparts topoiberia toposcandia etc is an obvious demonstration of the increased attention of the geoscience community towards processes controlling the development of continental topography with this in mind on 28 31 september 2007 we convened a workshop entitled the geology of vertical movements uplift and subsidence mountains and basins in the framework of the international lithosphere program s task force on sedimentary basins the workshop was hosted by the 1 convention of the moroccan association of petroleum geologists mapg and the venue was the town of marrakech in the frame of the superb moroccan mountains and basins e g fig 1 which have been the recent objective of many studies thus the workshop intended a particular emphasis on african

fragmentation versus transportation mechanisms in the pyroclastic sequence of monte pilato rocche rosse lipari italy abstract monte pilato is a rhyolitic pumice cone formed about 1400 years ago during the last volcanic activity which occurred at lipari its activity consisted of numerous explosive episodes ending with the extrusion of the rocche rosse obsidian lava flow we have identified nine different pyroclastic lithofacies of which four main lithofacies represent 90 of the erupted products they include 1 deposits consisting of decimeters to meters thick well sorted graded beds of pumice lapilli which are of fall origin 2 massive deposits consisting of decimeters thick beds of pumice lapilli in an ash matrix interpreted as being of pyroclastic flow origin 3 deposits of centimeters thick ash beds of surge origin 4 decimeter thick fine ash layers with scattered subcentimetric accretionary lapilli of turbulent flow origin the complex grain size distributions of the main lithofacies were distinguished using a multivariate statistic analysis r mode factor analysis variations of the grain size characteristics in relation to the distance from the vent area have been investigated in order to discriminate the roles played by fragmentation and transportation processes in the lithofacies 1 fall deposits the grain size distribution is always unimodal and varies from a rosin type distribution near the vent to a gaussian one in the distal outcrops this is caused by the transport process and the different particle trajectories in lithofacies 2 3 and 4 the grain size distributions are always polymodal the polymodality is not caused by preferential processes occurring during transportation but seems rather to be connected with the original fragmentation of the pyroclastic material the pumice lapilli present both in lithofacies 1 and 2 have mean vesicularity index values always in excess of 65 and the value is homogeneous throughout the sample these data suggest that for these two lithofacies the pumice lapilli originated from exsolution of magmatic gases in contrast the fine ash particles in lithofacies 2 and also the main mode of lithofacies 3 and 4 deposits show typical features of hydromagmatic fragmentation processes the grain size population is always centered at 4 5 0 032 0 064 mm and interestingly the same grain size has been obtained recently zimanowski et al 1991 for fragments produced by experimental magma water interaction field and laboratory data suggest that during monte pilato rocche rosse eruptions magmatic and hydromagmatic mechanisms were frequently operative at the same time

climate independent paleoaltimetry using stomatal density in fossil leaves as a proxy for co2 partial pressure existing methods for determining paleoelevation are primarily limited by 1 large errors 450 m 2 a reliance on incorrect assumptions that lapse rates in terrestrial temperature decrease with altitude in a globally predictable manner and or 3 are inherently climate dependent here i present a novel paleoelevation tool based on a predictable globally conserved decrease in co 2 partial pressure p co 2 with altitude as indicated by increased stomatal frequency of plant leaves the approach was validated using historical populations of black oak quercus kelloggii these analyses demonstrate highly significant inverse relationships between stomatal frequency and p co 2 r 2 0 73 independent of ecological or local climatic variability as such this is the first paleobotanical method to be globally applicable and independent of long term cenozoic climate change further tests on modern leaves of known elevations indicate that species specific application to the fossil record of q kelloggii q pseudolyrata will yield paleoelevation estimates within average errors of 300 m representing a significant improvement in accuracy over the majority of existing methods

changes of the geomagnetic field vector obtained from lava sequences on the island of vulcano aeolian islands sicily abstract a combined geochronologic k ar and palaeomagnetic study has been conducted on five volcanic sections 70 flows on the island of vulcano the sections span the interval from 15 2 to 135 4 ka with large hiatuses rock magnetic investigations indicate that the natural remanent magnetisation nrm is carried by titanomagnetites in the four oldest sections with a contribution from high coercivity magnetic minerals in the youngest section palaeomagnetic directions obtained by thermal demagnetisation document a large magnetic excursion at around 110 ka with virtual geomagnetic poles vgps that lie over eastern siberia these directions may represent a volcanic record of the termination of the blake event only about 15 of the samples from 19 flows proved suitable for palaeointensity thellier and thellier determinations these measurements indicate that the geomagnetic field has varied at vulcano between 16 and 53 t in the explored time interval when combined with previous results obtained at mt etna for the period from 140 to 60 ka tric et al 1994 phys earth planet inter 85 113 129 these results document a broad low at around 115 ka the palaeointensity values from vulcano and etna are consistent with global values suggesting the presence of a dominant dipole field contribution these values on the other hand are significantly smaller than those recently obtained from la reunion in the southern hemisphere this suggests that large long lived non dipolar components of the geomagnetic field may be present at la reunion in the interval from 130 to 90 ka these observations are consistent with the fact that the vgp angular dispersion calculated from non excursional data is significantly smaller at vulcano than at la reunion

event stratigraphy of a caldera forming ignimbrite eruption on tenerife the 273 ka poris formation the 273 ka poris formation in the bandas del sur group records a complex compositionally zoned explosive eruption at las canadas caldera on tenerife canary islands the eruption produced widespread pyroclastic density currents that devastated much of the se of tenerife and deposited one of the most extensive ignimbrite sheets on the island the sheet reaches 40 m thick and includes plinian pumice fall layers massive and diffuse stratified pumiceous ignimbrite widespread lithic breccias and co ignimbrite ashfall deposits several facies are fines rich and contain ash pellets and accretionary lapilli eight brief eruptive phases are represented within its lithostratigraphy phase 1 comprised a fluctuating plinian eruption in which column height increased and then stabilized with time and dispersed tephra over much of the southeastern part of the island phase 2 emplaced three geographically restricted ignimbrite flow units and associated extensive thin co ignimbrite ashfall layers which contain abundant accretionary lapilli from moist co ignimbrite ash plumes a brief plinian phase phase 3 again dispersing pumice lapilli over southeastern tenerife marked the onset of a large sustained pyroclastic density current phase 4 which then waxed phase 5 covering increasingly larger areas of the island as vents widened and or migrated along opening caldera faults the climax of the poris eruption phase 6 was marked by widespread emplacement of coarse lithic breccias thought to record caldera subsidence this is inferred to have disturbed the magma chamber causing mingling and eruption of tephriphonolite magma and it changed the proximal topography diverting the pyroclastic density current s down the guimar valley phase 7 phase 8 involved post eruption erosion and sedimentary reworking accompanied by minor down slope sliding of ignimbrite this was followed by slope stabilization and pedogenesis the fines rich lithofacies with abundant ash pellets and accretionary lapilli record agglomeration of ash in moist ash plumes they resemble phreatomagmatic deposits but a phreatomagmatic origin is difficult to establish because shards are of bubble wall type and the moisture may have arisen by condensation within ascending thermal co ignimbrite ash plumes that contained atmospheric moisture enhanced by that derived from the evaporation of seawater where the hot pyroclastic currents crossed the coast ash pellets formed in co ignimbrite ash clouds and then fell through turbulent pyroclastic density currents where they accreted rims and evolved into accretionary lapilli

a new approach to stable isotope based paleoaltimetry implications for paleoaltimetry and paleohypsometry of the high himalaya since the late miocene the change in oxygen isotopic composition of precipitation is modeled using equilibrium fractionation during rayleigh distillation linked to the thermodynamics of atmospheric ascent and water vapor condensation the primary controllers of the vertical variation in isotopic composition with elevation are the low elevation temperature and relative humidity as these control the vertical distribution of condensation an empirical fit of precipitation versus model condensation based on alpine stations is derived this fit is represented in the model as the weighted mean composition of condensation within a 1000 m thick air parcel 1500 500 m above the ground surface and is used for all other regions comparison of model versus observed modern precipitation reveals a close fit particularly of more highly elevated sites comparison of modern waters in the himalayas and southern tibet with model predictions particularly as revealed by comparison of observed and predicted hypsometry provides additional support to the validity of the model finally application of this model to estimates of paleo waters in the himalayas and southern tibet reveals that this region had already achieved its present hypsometry by the late miocene about 10 ma ago fl 2001 published by elsevier science b v

late quaternary ancient shorelines at lipari aeolian islands stratigraphical constraints to reconstruct geological evolution and vertical movements indicators of three fossil shorelines located at elevations of 43 45 m asl i order 23 27 m ii order and about 12 m iii order are recognized on the island of lipari detailed evaluation of the stratigraphic relationships to the volcanic substratum allows their correlation with late quaternary eustatic highstands of tyrrhenian age corresponding to marine oxygen isotope substages 5e 124 ka 5c 100 ka and 5a 81 ka marine deposits related to the ancient shorelines represent useful stratigraphic markers as related unconformities constrain the geological evolution of lipari this is interpreted as a result of two main stages of volcanic activity pre and post tyrrhenian spaced out by one stage characterized by prevalent marine erosional episodes tyrrhenian chronological and altimetrical data concerning the ancient shorelines have been used to estimate the vertical mobility of the volcanic edifice of lipari which is characterized by a continuous uplift at an average rate of 0 34 mm a during the last 125 ka this estimation is fully concordant with the values obtained during the same time period from the nearby islands of filicudi 0 31 mm a and salina 0 36 mm a suggesting a similar uplift trend induced by the prevalence of regional tectonic processes

the campanian ignimbrite and codola tephra layers two temporal stratigraphic markers for the early upper palaeolithic in southern italy and eastern europe tephra layers from archaeological sites in southern italy and eastern europe stratigraphically associated with cultural levels containing early upper palaeolithic industry were analysed the results confirm the occurrence of the campanian ignimbrite tephra ci ca 40 cal ka bp at castelcivita cave southern italy temnata cave bulgaria and in the kostenki borshchevo area of the russian plain this tephra originated from the largest eruption of the phlegrean field caldera represents the widest volcanic deposit and one of the most important temporal stratigraphic markers of western eurasia at paglicci cave and lesser sites in the apulia region we recognise a chemically and texturally different tephra which lithologically chronologically and chemically matches the physical and chemical characteristics of the plinian eruption of codola a poorly known late pleistocene explosive event from the neapolitan volcanoes likely somma vesuvius for this latter we propose a preliminary age estimate of ca 33 cal ka bp and a correlation to the widespread c 10 marine tephra of the central mediterranean the stratigraphic position of both ci and codola tephra layers at castelcivita and paglicci help date the first and the last documented appearance of early upper palaeolithic industries of southern italy to ca 41 40 and 33 cal ka bp respectively or between two interstadial oscillations of the monticchio pollen record to which the ci and codola tephras are physically correlated corresponding to the greenland interstadials 10 9 and 5 in eastern europe the stratigraphic and chronometric data seem to indicate an earlier appearance of the early upper palaeolithic industries which would predate of two millennia at least the overlying ci tephra the tephrostratigraphic correlation indicates that in both regions the innovations connected with the so called early upper palaeolithic encompassing subsistence strategy and stone tool technology appeared and evolved during one of the most unstable climatic phases of the last glacial period on this basis the marked environmental unpredictability characterising this time span is seen as a potential ecological factor involved in the cultural changes observed

cycles of passive versus active diapirism recorded along an exposed salt wall abstract although it has long been recognised that passive salt diapirism may encompass sub ordinate cycles of active diapirism where sedimentary overburden is periodically shed off the roof of the rising salt there has been very little study of this process around exposed salt halite diapirs however the late miocene pliocene sedom salt wall on the western side of the dead sea basin presents an opportunity for detailed outcrop analysis of diapiric salt and the associated depositional and deformational record of its movement during both passive and active phases of diapirism the sub seismic scale record of diapirism includes sedimentary breccia horizons interpreted to reflect sediments being shed off the crest of the growing salt wall together with exceptional preservation of rotated unconformities and growth faults areas of more pronounced dips directed towards the salt wall are capped by unconformities and interpreted to represent withdrawal basins within the overburden that extend for at least 1500 m from the salt margin elsewhere broad areas of upturn directed away from the salt extend for up to 1250 m and are marked by a sequence of rotated unconformities which are interpreted to bound halokinetic sequences the margins of the salt wall are defined by steep extensional boundary faults that cut upturned strata and have enabled rapid and active uplift of the salt since the holocene the sedom salt wall therefore charts the transition from passive growth marked by withdrawal basins growth faults and unconformities to more active intrusion associated with major boundary faults that enable the rapid uplift of overburden deposited on top of the salt to 100 m above regional elevations in the past 43 ka individual cycles of passive and active diapirism occur over timescales of

tectonic and volcanic evolution of panarea aeolian islands italy abstract based on new geophysical volcanological structural and radiometric data a morphological structural reconstruction of the submarine part of the panarea volcanic edifice is provided and a model for the evolution of the entire complex is proposed panarea is a small part of a much larger submarine edifice whose overall shape is one of a truncated cone with an eastern protrusion the base of the cone is about 1500 m below sea level it has a diameter of about 23 km and an area of 460 km2 several lobes are present on the steep eastern slopes of the cone and the wide submarine top is of a morphology which is more complex than previously thought the evolution of the panarea volcanic complex occurred in three stages 1 1 development of a central volcano in the western sector of the complex the island of panarea represents the top of this volcano 2 2 eastward shifting of volcanic activity producing development of the lobed eastern sector of the complex 3 3 extensive caldera collapse of the central part of the complex and emplacement within the collapsed area of domes and lava bodies of various affinities some of which are basaltic ne sw oriented structures seem to have had a fundamental role during the development of the panarea volcanic complex these structures have been active until recent times and are of regional significance indeed the evolution of nearby stromboli has been controlled by the ne sw trending structures panarea and stromboli also display similar magnetic anomaly trends geochemical affinities and temporal relationships in volcanism

tyrrhenian sea tephrochronology of the oxygen isotope record for the past 60 000 years abstract a chronology of the marine oxygen isotope record of the past 60 ka is proposed by correlating eight marine ash layers with terrestrial volcanic deposits dated by the 14c and or k ar methods detailed oxygen isotope analyses were made on the planktonic foraminifera of three cores collected in the central tyrrhenian sea the origin of the ash layers was determined by major and trace elements analyses then the major pyroclastic terrestrial deposits were sampled and analysed in order to provide land sea correlations two ash layers occurred during the warm event that followed the first step of the deglaciation and which was dated at 12 6 0 5 ka b p another ash layer is present near the last glacial maximum that we have dated at 17 5 0 3 ka b p during isotopic stage 3 five ash layers were recognized and dated which allowed us to assign ages to the isotopically light oxygen peaks warmer interstadials at 31 1 5 ka and 33 4 1 6 ka denekamp at 37 5 2 ka hengelo and successively at 49 2 ka 52 4 2 2 ka 57 2 2 ka and 60 5 2 2 ka moershoofd complex

influence of paleorelief on the mid miocene climate variation in southeastern washington northeastern oregon and western idaho usa abstract terrestrial climate proxy records repeatedly show spatial heterogeneity because regional climate condition is largely influenced by the relationship between large scale atmospheric circulation patterns and regional topographic features the paleosols developed on the top of columbia river basalt flows emplaced between 15 3 and 15 8 ma in the northwestern united states show significant spatial variations in the mid miocene soil forming processes the paleosol in the northwestern part of the study area has the least degree of chemical weathering fine scale and very shallow penetrating depth of root traces with the estimated paleoprecipitation and paleotemperature of about 550 mm and 16 c respectively the paleosols in the southeastern part of the study area indicate more intense chemical weathering with the estimated paleoprecipitation and paleotemperature of approximately 1400 to 1500 mm and 17 c respectively the spatial variations in paleo pedogenesis were predominantly affected by spatial heterogeneity in the mid miocene regional climate and regional paleotopographic features taking the other ancient soil forming factors including time parent rock materials and biological activities into account we suggest that intrusions of hot columbia river basalt magma into the crust were responsible for the regional surface uplift and the paleoclimate heterogeneity because the major vent systems of the columbia river basalt eruptions were located in the area where development of the mid miocene high topography existed within the blue mountains paleotopography of the earth s surface can be reconstructed by the paleoprecipitation and paleotemperature estimations from several spatially distributed chrono stratigraphic paleosols although it is difficult to estimate the magnitude of the paleorelief precisely

statistical analysis of textural data from complex pyroclastic sequences implications for fragmentation processes of the agnano monte spina tephra 4 1 ka phlegraean fields southern italy the agnano monte spina eruption 4 1 ka generated pyroclastic deposits with complex internal stratigraphy that reflects variations in eruptive style to obtain constraints on the fragmentation processes we analysed grain size and scanning electron microscopy sem data by means of multivariate statistical techniques of the cluster and factor analysis types the results allow the identification of end member deposits related to either pure magmatic activity or pure phreatomagmatic activity in addition some deposits show evidence of the contemporaneous operation of both end member fragmentation modes the presence of the two contrasting fragmentation processes during the various phases of explosive activity is tentatively interpreted to be a function in inhomogeneities in gas exsolution processes within the magma column that feeds the eruption

volcanological and magmatological evolution of stromboli volcano aeolian islands the roles of fractional crystallization magma mixing crustal contamination and source heterogeneity the present paper reports the results of a detailed stratigraphical petrological and geochemical investigation on the island of stromboli aeolian arc southern tyrrhenian sea major and trace element data determined on a large quantity of samples from well established stratigraphic positions indicate that the magmatological evolution of the island through time was more complex than previously known the activity of the exposed part of stromboli which occurred over a time span of about 100 000 years started with the emission of high k calc alkaline hkca volcanics which were covered by calc alkaline ca shoshonitic sho high k calc alkaline hkca and potassic ks products the most recent activity consists of hkca lavas and the present day sho basaltic volcanics emitted by mildly explosive strombolian activity most of the products are lavas with minor amounts of pyroclastic rocks emplaced mainly during the early stages of activity the transition from the sho to the ks cycle was associated with the collapse of the upper part of the volcanic apparatus the transition from ks to the present day sho activity has been found to have occurred at the time of the sliding of the western portion of the volcano that generated the sciara del fuoco depression the rock series cropping out at stromboli show variable enrichment in potassium incompatible trace elements and radiogenic sr which increase from ca through hkca and sho up to ks rocks major trace element and sr isotopic data agree in indicating that the hkca and sho series evolved by crystal liquid fractionation starting from different parental liquids whereas crustal assimilation appears to have been the leading process during the evolution of ks volcanics mixing processes also played a role although they can be well documented only when they occurred between magmas with different isotopic and geochemical characteristics geochemical modelling based on trace element and isotopic data indicates that the mafic magmas of the different volcanic series may be generated by melting of an upper mantle heterogeneously enriched in incompatible elements and radiogenic sr by addition via subduction of different amounts of crustal material geochemical data however are also in agreement with the alternative hypothesis that the most mafic magmas of the different series have been generated by combined processes of fractional crystallization assimilation and mixing of a ca magma in a deep sited magma chamber the mafic magmas formed by these complex processes were successively emplaced in a shallow reservoir where they evolved by simple fractional crystallization hkca and sho series and by assimilation of crustal material ks the occurrence of changes in the geochemical signatures of the magmas at the time of the structural modification of the volcano is believed to favour the hypothesis that the variable composition observed in the volcanic rocks of stromboli is the result of processes occurring within the volcanic system

effect of precipitation regime on δ d values of soil n alkanes from elevation gradients implications for the study of paleo elevation we measured dd values of long chain n alkanes isolated from 30 surface soil samples along two elevation transects on the tibetan plateau differing in precipitation regime and water source the east asian monsoon precipitation dominates the wetter regime on the eastern slope from 1230 to 4300 m of gongga shan on the eastern tibetan plateau precipitation from the polar westerlies dominates the drier region on the slope from 1900 to 5000 m in the west kunlun shan on the northwestern tibetan plateau the decrease in dd value with elevation in the wetter region greatly exceeded that in drier region by 1 9 0 1 100 m and 1 4 1 0 100 m respectively the apparent fractionation between leaf wax and precipitation ewax p values in the wetter region ca 164 were more negative than those in drier region ca 125 above 3200 m we also measured dd values in leaves of six common living trees values from 287 to 193 from gongga shan ranging from about 2900 4200 m the abundance weighted average values of the nalkanes ddwax show a strong reverse correlation with sample source elevation r 2 0 78 for soils from 2 0 85 for soils from west kunlun shan above 3200 m suggesting that n alkane ddwax faithfully records the precipitation dd and that the isotopic altitude effect of precipitation controls ddwax altitudinal gradients in the mountains the data show a fairly strong monotonic dependency of n alkane dd values on elevation for the eastern plateau but a complex relationship between n alkane dd values and elevation for the northwestern plateau the ddwax values at sites below 3200 m from the kunlun shan area exhibit an unexpected positive correlation with elevation the study confirms the potential for using sediment ddwax values to reconstruct paleo elevation in wetter regions but suggests caution in applying the approach to dry regions our results also show it is essential to consider the intricacy of the pattern of atmospheric circulation and water sources and their influence on the lapse rate of dd values with elevation

tephrostratigraphy study for the last 18 000 14 c years in a deep sea sediment sequence for the south adriatic abstract a detailed tephrostratigraphy supported by accelerator mass spectrometry ams 14c dating and isotopic and geochemical analyses has been carried out for a deep sea core collected from the southern adriatic sea which spans the last 18 14c kyr fourteen ash layers have been recognized in the marine core and the origin was determined by comparing their age and geochemistry with tephra detected in terrestrial deposits the geochemical signatures of marine ash layers indicate a prevailing campanian and subordinate etnean and eolian provenances collectively they are attributed to sources in the phlegraean fields lam lagno amendolare ln1 ln2 gm1 c 2 nyt neapolitan yellow tuff c 1 agnano pomici principali ams pf agnano monte spina ast astroni somma vesuvius l9 pomici di base l8 greenish mount etna et1 y1 biancavilla ignimbrite lipari e 1 gabellotto fiumebianco and palinuro seamount pal 1 some of these eruptions have been detected for the first time in marine cores astroni lam l9 l8 and three were detected and dated by marine tephra ln1 ln2 and pal 1 providing new more precise stratigraphic markers for the last 18 kyr in the south adriatic marine record

paleoaltimetry of the tibetan plateau from d h ratios of lipid biomarkers abstract the past elevation of the land surface provides a unique constraint on the underlying lithospheric structure during mountain and plateau formation development of new paleoaltimetry techniques that can be applied to a wide variety of sample types is therefore of continuing importance this study evaluates organic substrates that preserve the d ratio of surface waters as a new approach to reconstruct paleoaltimetry we measured the hydrogen isotope composition of n alkanes from epicuticular plant waxes preserved in lacustrine deposits to reconstruct the d of precipitation in cenozoic basins that have been elevated as part of the tibetan plateau n alkane d and carbonate 18 o inferred water compositions from the eocene miocene lunpola basin and miocene hoh xil basin plot near or at enriched values relative to the global meteoric water line as expected for evaporative lakewater and leafwater systems that have the same precipitation source n alkane d based water compositions are nearly identical to the minimum carbonate 18 o based values demonstrating that plant wax d is minimally affected by evaporation compared to lacustrine calcite 18 o this agreement strongly supports the presence of similar precipitation isotopic compositions in both archives despite different isotope systems source water reservoirs archive materials modes of incorporation and diagenetic processes paleoelevations for each basin and time period were calculated from precipitation isotope ratios using the isotope altitude relationship derived from both a simple thermodynamic model and modern precipitation sampling from the plateau region our new results from the hoh xil basin suggest 1700 to 2600 m of uplift may have occurred some time between the late eocene and early miocene the timing of this uplift is consistent with late oligocene compressional deformation of the hoh xil basin and northward growth of the tibetan plateau however the calculated uplift is not a unique solution from the paleoisotope data because of uncertainties in eocene and miocene moisture sources and isotope gradients for the northern plateau our results demonstrate the utility of lipid based estimates of paleoelevation and expand the types of deposits amenable to paleoaltimetry analysis

creep of rocksalt abstract a review is presented of the fundamental flow properties and processes in experimentally deformed natural and synthetic halite single crystals and polycrystalline aggregates included in the summary are discussions of a microstructures induced during steady state creep b creep rupture of rocksalt c experiments associated with project salt vault and more recent field studies and d brine migration a representative steady state flow law determined for natural aggregates and maximum natural deviatoric stresses deduced from subgrain sizes are applied briefly to considerations of creep in waste repositories and of salt dome dynamics while the mechanical behavior of rocksalt is probably better understood than for all other rock types further investigations especially on load path stress history and creep rupture are clearly mandated furthermore additional investigations of brine migration and of bench and field scale deformations are needed the latter incorporating realistic rocksalt flow properties into numerical simulations of natural rock mass response

dilation of anisotropic rock salt evidence from mount sedom diapir the mechanical behavior of bedded rock salt is studied using constant strain rate biaxial tests performed on 24 bedded rock salt samples from mount sedom diapir careful measurements of elastic parameters in unload reload loops indicate that they are influenced by confining pressure but are not sensitive to anisotropy the yield stress is also influenced by confining pressure but not by anisotropy the stress strain curve therefore indicates isotropy up to the yield stress initiation of dilation marks the onset of dependence of volumetric strain on anisotropy major principal compressive stress at dilation 1 d is at maximum when compression is normal to bedding planes 0 the stress decreases with increasing values of and minimum values are measured when compression is parallel to bedding planes 90 beyond onset of dilation point the relative dilation with respect to stress difference v e 1 3 1 1 d mpa 1 increases with decreasing confining pressure and with increasing namely dilation is intensified with decreasing confining pressure and as the major principal compressive stress direction becomes parallel with bedding plane orientation current models for compression dilation boundary ignore anisotropy and therefore provide site specific solutions but fail to describe general rock salt behaviour a new empirical model for compression dilation boundary in anisotropic rock salt developed for a data set from mount sedom predicts that stress at onset of dilation decreases with decreasing confining pressure and with increasing value of the rate of change of 1 d with respect to decreases with decreasing confining pressure and the rate of change of 1 d decreases with increasing confining pressure for all values of

early pliocene paleo altimetry of the zanda basin indicated by a sporopollen record abstract whether the uplift of the tibetan plateau tp led to the origin and development of the indian monsoon is still in dispute a helpful indicator would be greater knowledge about the chronological development of paleo altimetry the zanda basin located on the sw margin of the tp forms one of the most extensive cenozoic sedimentary basins in tibet the modern climate of this area is controlled by the indian monsoon circulation system it is thus an appropriate region for the study of paleo altimetry in addition to research into the relation between the tp and the indian monsoon sporopollen analyses of early pliocene lacustrine strata in the zanda basin show that gymnosperm pollen is dominant av 77 and mainly composed of picea av 27 2 and abies av 24 2 fern spores occupy a lesser proportion av 17 6 while angiosperm pollen including temperate sub tropical broadleaved trees shrubs and herbs accounts for only a small proportion of the assemblage this sporopollen assemblage suggests that sub alpine dark coniferous forests were distributed around the basin and grow in a cool and wet climate rather than in a modern alpine steppe environment these characteristics indicate that the zanda basin s altitude throughout the early pliocene was most probably lower than it is at present

age and petrology of the late pleistocene brown tuffs on lipari italy late pleistocene volcanic products on lipari consist mainly of pyroclastic surge deposits monte guardia sequence and fine grained brown tuffs radiometric age determination on carbon from thin soils at the top of the tuffs indicate that they have several ages of emplacement ranging from more than 35 000 to 16 800 years ago chemical and microprobe data on glass and mineral fragments from these tuffs show that they belong to a shoshonite or high k series this composition is compatible with an origin related to the magma system of vulcano but not with the magma system on lipari

volcanic history of lipari aeolian islands italy during the last 10 000 years abstract examination of the volcanic stratigraphy of deposits younger than 10 000 years on lipari indicates four principal periods of volcanic activity related to specific centers the products from each different volcanic center are defined as volcano stratigraphic unit vsu from the oldest these are the canneto dentro gabellotto fiume bianco forgia vecchia and monte pilato rocche rosse vsus the study of textures and dispersal of the deposits permitted the vents to be localized and the recent volcanic history of lipari to be reconstructed the oldest event formed a small explosion breccia cone with a final obsidian lava in the canneto dentro area immediately afterward a complex series of explosions produced the widespread dry surge deposits of the gabellotto fiume bianco sequence this activity ended with the extrusion of a domical lava flow the renewal of activity occurred in the pirrera area with an explosive eruption that produced explosion breccia deposits the last eruptions from this vent were coeval with the first eruption of m pilato the rim of the explosion breccia cone was partially destroyed by the forgia vecchia lava flow m pilato cone grew in a very short period of time due to a continuous swarm of explosive events after a short repose time a series of more energetic and superficial explosions occurred through a vent slightly to the south the extrusion of the rocche rosse lava flow about 729 a d ended this cycle of activity all the volcanic centers follow a quite similar stochastic pattern starting with a fall or surge eruption and ending with effusion of viscous rhyolitic lavas the four centers are aligned along either nw se or ne sw fault systems according to the structural pattern of the island they can be placed into two groups the canneto dentro gabellotto centers and the forgia vecchia m pilato centers a long quiescence 3 500 years separates the activity of these two groups while inside of each the activities were nearly contemporaneous or in rapid succession

deformation of the 125 ka marine terrace in italy tectonic implications in peninsular italy marine terraces and shorelines created during oxygenisotope substage 5e known historically as the tyrrhenian highstand provide a reliable and homogeneous datum of vertical motions during the past 125 000 years published accounts of 121 locations on the tyrrhenian inner edge were reinterpreted and used to calculate both local and regional uplift rates the data show arching of southern italy between the tyrrhenian and the adriatic coasts and of the calabrian arc between the sangineto and the longi taormina tectonic lineaments at rates of up to 1 2 mm yr for the past 125 ka they also suggest that the present configuration of the southern apennines is the product of post early pleistocene regional uplift superimposed on tortonian to early pleistocene thrusting uplift patterns are characterised by different wavelength in different geodynamic settings suggesting a close link with the depth of the causative tectonic sources

quantification of large uncertainties in fossil leaf paleoaltimetry 1 estimates of paleoelevation potentially constrain geodynamic models of continental deformation and inform interpretations of landscape and climate evolution one widely used paleobotanical approach reconstructs paleoelevation from the difference in estimated atmospheric enthalpy between a known sea level and a targeted coeval elevated fossil floral site enthalpy is estimated using climate leaf analysis multivariate program clamp on 31 leaf size and shape variables that have been calibrated in living forests errors related to clamp are significantly greater than often reported and there are many sources of large potential error related to this method that are either difficult to quantify or unquantifiable and are thus not documented here we quantify one significant bias toward underestimation of leaf area in the clamp data set 50 that affects all clamp climate estimates including enthalpy crucially errors in paleoelevation when the leaf size bias is included are in the range of 2 km or more at least 2 times the previous estimates and exceeding the plausible paleoelevations of many fossil sites previously published paleoelevations derived from this technique are unlikely to be accurate either in magnitude or in estimated error

monte guardia sequence a late pleistocene eruptive cycle on lipari italy this paper documents a complex sequence of interbedded lapilli fall base surge and pyroclastic flow deposits here named the monte guardia sequence that erupted from volcanic centers in the southern part of lipari aeolian island arc radiocarbon data from ash flow tuffs above and below this sequence bracket its eruption between 22 600 and 16 800 years ago geologic evidence however suggests that this single eruptive cycle had a more restricted duration of years to tens of years the basis for our interpretations comes from data measured at 38 detailed sections located throughout the island the monte guardia sequence rests on a series of lower rhyolitic endogenous domes in the southern part of lipari and it covers the oldest lavas lahars and pyroclastic flows in the north only in the northeast part of the island is it covered by younger deposits which there consist of lapilli tuffs and lavas of the monte pilato rhyolitic cycle the deposit ranges in thickness from more than 60 m surrounding the vents in the south to less than a few decimeters at 10 km distance in the north throughout most of the island the monte guardia sequence overlies a thin andesitic lapilli fall layer which is a key bed for correlation this lapilli tuff probably erupted from a volcanic center on another island of the aeolian arc possibly salina the principal activity of the monte guardia sequence started with an explosion that formed a continuous breccia blanket covering most of the island some pumiceous blocks within this breccia are composed of alternating bands of acidic and andesitic composition suggesting that the initiation of pyroclastic activity could have been triggered by magma mixing typical monte guardia sequence consists of explosive products that grade from magmatic pumice fall to phreatomagmatic base surge character the eruptive cycle is characterized by a number of energy decreasing megarhythms that start with a lapilli fall bed and end with a base surge set that progresses through sand wave massive and planar beds isopach maps of the fall and surge deposits indicate that both types were directed to the northwest by prevailing winds existing topographic relief was an additional factor that affected the emplacement of surge products at the end of the cycle andesitic pyroclastic flows and rhyolitic endogenous domes were emplaced above the monte guardia deposits near the vent

temporal evolution of a three component system the island of lipari aeolian arc southern italy the volcanic products from lipari define an evolutionary trend with a high gradient of k enrichment similar to the calc alkaline to potassic volcanism of other islands in the aeolian arc stratigraphic reconstruction of the island based on field and geochronological data indicate that the volcanic activity can be subdivided in two stages the first stage from 223 to 42 ka consists of six eruptive cycles and is characterized by basalts and basalt andesites showing progressive increase in both sio2 and k2o contents with time the second stage consists of four cycles erupted since 42 ka and is marked by an apparent rejuvenation of the geochemical system with the appearance of the first rhyolitic products fractional crystallization assimilation and mixing models suggest that the geochemistry of lipari volcanism evolved with time by a complex interplay between two mantle derived components one sub alkaline and the other alkaline in addition to crustal melts and or crustally derived materials a petrogenetic model in which fractional crystallization was subordinate to mixing best fits the geochemical data and petrographic observations of macro and microscopic features melts from the crustal and mantle end members are almost always present in the system but the relative proportions appear to vary with time the sub alkaline mantle component source of tyrrhenian tholeiites is an important contributor to the early evolution of the volcanism in lipari input from the alkaline mantle component source of the roman comagmatic province increases with time and the crustal component becomes dominant in the later activity the preferred petrogenetic model for the temporal evolution of the volcanic system in lipari involves melting initially caused by an increase in the thermal input related to the opening of the tyrrhenian sea and or to subduction processes the quick rise of the isotherms and almost contemporaneous melting of source materials with different compositions favored complex mixing during ascent of the melts

mechanical and petrophysical behavior of organic rich chalk from the judea plains israel abstract the geomechanical and petrophysical properties of the late cretaceous organic rich chalk from the shefela basin in central israel were studied using laboratory tests performed on solid cylindrical samples from core retrieved from the resource the investigated section includes two formations the ghareb and the mishash of central israel the shefela chalk is dark brown and rich in organic matter with up to 20 toc at the middle of the ghareb formation both uniaxial compressive strength and young s modulus of the chalk display stress dependency with the mean values increasing with depth the tensile strength parallel to the bedding is found to be higher by 1 7 on average for ghareb and by 2 2 on average for mishash compared to the tensile strength normal to the bedding unconfined compressive strength appears to increase with total organic carbon toc whereas the effect of toc on tensile strength and elasticity is less conclusive a linear compression dilation boundary is defined for the shefela chalk based on analysis of uniaxial and triaxial test results the porosity is high approx 37 at the ghareb formation decreasing to 32 at the mishash formation the permeability is very low ranging between 0 001 md and 1 md and exhibits strong anisotropy with a vertical to horizontal ratio of 0 2 the porosity and permeability are found to be independent of the variation in organic content confirming co precipitation of the calcite minerals and organic matter during deposition

outward growth of the tibetan plateau during the cenozoic a review abstract the surface uplift history of the tibetan plateau tp offers a key testing ground for evaluating models of collisional tectonics and holds important implications for processes ranging from global cooling to the onset of the asian monsoon various models have been proposed to reveal the surface uplift history of the tp but controversies remain we evaluate these models using data from sedimentology and stratigraphy structural geology magmatism exhumation and paleoaltimetry studies structural analyses indicate that thrust belts which spread from the central tp outward toward its surrounding margins accommodated most of the india asia convergence and facilitated crustal shortening and thickening in the central tp eocene adakitic rocks located in the qiangtang and the lhasa blocks likely were generated by partial melting of an eclogitic source paleogene 50 30 ma potassic rocks only occur in the qiangtang block whereas late oligocene late miocene 26 8 ma potassic rocks occur both in the qiangtang and lhasa blocks low temperature thermochronologic ages in the central tp are older than 40 35 ma whereas those in the margins are younger than 20 ma mostly late miocene and pliocene pleistocene in age independent paleoaltimetry estimates suggest that the lhasa and qiangtang terranes attained their current elevations during the eocene most likely due to the initial collision between india and lhasa whereas the hoh xil basin area to the north and himalayas to the south were still low even below sea level in the latter case we argue for an inside out growth pattern for the tibetan plateau the tp grew southward and northward from a nucleus of high topography and is likely to continue expanding along the mazar tagh fault to the northwest the kuantai shan hei shan longshou shan to the northeast the longquan shan to the east and the shillong plateau to the south if the northward force of india would not diminished

a novel palaeoaltimetry proxy based on spore and pollen wall chemistry understanding the uplift history and the evolution of high altitude plateaux is of major interest to a wide range of geoscientists and has implications for many disparate fields currently the majority of palaeoaltimetry proxies are based on detecting a physical change in climate in response to uplift making the relationship between uplift and climate difficult to decipher furthermore current palaeoaltimetry proxies have a low degree of precision with errors typically greater than 1 km this makes the calculation of uplift histories and the identification of the mechanisms responsible for uplift difficult to determine here we report on advances in both instrumentation and our understanding of the biogeochemical structure of sporopollenin that are leading to the establishment of a new proxy to track changes in the flux of uv b radiation over geological time the uv b proxy is based on quantifying changes in the concentration of uv b absorbing compounds uacs found in the spores and pollen grains of land plants with the relative abundances of uacs increasing on exposure to elevated uv b radiation given the physical relationship between altitude and uv b radiation we suggest that the analysis of sporopollenin chemistry specifically changes in the concentration of uacs may offer the basis for the first climate independent palaeoaltimetry proxy owing to the ubiquity of spores and pollen in the fossil record our proposed proxy has the potential to enable the reconstruction of the uplift history of high altitude plateaux at unprecedented levels of fidelity both spatially and temporally

the elevation history of the tibetan plateau and its implications for the asian monsoon abstract the determination of the evolving palaeoaltitude of the tibetan plateau since the india eurasia collision underpins our understanding of how orography in central asia affects the intensity of the monsoon and hence global climate change palaeoaltitudes however cannot be measured directly and need to be inferred from proxy observations that are usually model dependent differing tectonic models for the behaviour of the lithosphere during continental collision have contrasting implications for the elevation of the plateau however two techniques recently employed for determining palaeo elevation are independent of tectonic models the first involving the variation with altitude of oxygen isotopes in precipitation and the second involving the change of leaf morphology with moist static energy of the atmosphere elevation studies have focused on southern tibet largely due to the relative ease of access to the region there is a remarkable unanimity amongst the diverse techniques applied that the altitude of the southern plateau has not significantly changed since at least the mid miocene ca 15 ma arguing for an onset of the monsoon system during or before the early miocene a range of tectonic studies suggest that the northern and eastern parts of the plateau are younger geomorphological features but there are few quantitative constraints of the timing of elevation from these regions of tibet since both the elevation and the surface area of the plateau impact on atmospheric circulation palaeoaltitude studies need to be extended to chart the increasing areas of elevated land surface through time

stratigraphy and significance of brown tuffs on the aeolian islands southern italy abstract brown tuffs bt are volcaniclastic ash deposits prominently represented in the stratigraphic profiles of all the aeolian islands and capo milazzo on the northern coast of sicily detailed stratigraphy and tephrochronology together with available radiometric ages suggest that they were emplaced over a long time interval spanning from the end of the last interglacial period ca 80 ka bp up to 4 5 ka bp age of the overlying punte nere pyroclastic products on vulcano the most complete bt succession is documented on lipari where 14 distinct and successive units are subdivided by the interbedding of widespread tephra layers local volcanic products paleosols and epiclastic deposits and the occurrence of local erosive surfaces inter island occurrence of ischia tephra a widely known tephra layer in the aeolian archipelago dated at 56 ka bp and monte guardia pyroclastics from lipari dated at 22 20 ka bp subdivides the bt succession in upper ubt intermediate ibt and lower bt units lbt which can be correlated at regional level the lbt was emplaced between 80 and 56 ka bp the ibt between 56 and 22 ka bp and the ubt between 20 and 4 5 ka bp on the basis of stratigraphy similarity in lithology and textural features morphology of glass fragments composition and consistency of thickness and grain size variations ubt units correlate with piano grotte dei rossi tuffs on vulcano island they were generated by pulsating hydromagmatic explosive activity giving rise to pyroclastic density currents spreading laterally from a source located inside the la fossa caldera on vulcano island composition is in agreement with this hypothesis since ubt compositional features match those of vulcano magmas erupted in that period the effect of co ignimbrite ash clouds or associated fallout processes from sustained eruptive columns is seen to explain the presence of ubt in areas further away from the suggested source e g salina and lipari islands and capo milazzo the origin of ubt exposed on panarea island is still a matter of debate due to contrasting compositional data due to large uniformity of lithological textural and componentry characters with respect to the ubt the lower portions of the bt succession lbt ibt are considered to be the result of recurrent large scale hydromagmatic eruptions of similar type moreover for the ibt units the correlation with monte molineddo 3 pyroclastics of vulcano island on the basis of lithological compositional and stratigraphic matching again suggests source s related to the vulcano plumbing system and located within the la fossa caldera

reconstruction of altitudinal transportation range of leaves based on stomatal evidence an example of the early pleistocene fagus leaf fossils from central japan abstract fossil plant assemblages play a critical role in paleoenvironment estimation especially for the cenozoic however the extent that the fossil assemblage reflects the source forest is difficult to estimate the comparison between modern assemblages and their subfossil assemblages shows a significant difference indicating that the transportation of plant organs can affect the accuracy of paleoenvironment analysis in this study we aim to detect leaf transport based on stomatal frequency stomatal index and stomatal density variation of 30 fossilized fagus crenata leaves from the sayama formation 1 54 1 66 ma we distinguished the sun and shade morphotype of fossil leaves by using undulation index and calculated stomatal frequency variation of only sun fossil leaves considering the stomatal index variation of fossil fagus crenata leaves the paleo pco2 variation in a warm period between 1 54 ma and 1 66 ma was estimated as ca 35 0 to 39 6 pa based on this paleo pco2 variation altitudinal transportation range of the early pleistocene fossil fagus crenata leaves was estimated at over 1000 m we presume that leaves of fagus crenata in the fossil assemblage possibly had come from a wide range of altitudes near the fossil site during the early pleistocene this provides an example of altitudinal transportation of plants before their deposition which suggests a consideration when reconstructing the palaeovegetation and palaeoclimate from fossil assemblages

lapse rates and other variables applied to estimating paleoaltitudes from fossil floras abstract a previous method for determining paleoaltitude from fossil floras has used the difference between sea level and upland paleotemperatures which is then multiplied by the reciprocal of a normal lapse rate the present study examines other variables that can significantly influence such results terrestrial lapse rates have been calculated for 39 areas of the world based upon mean annual temperature mat mean warm month temperature mat and mean cold month ttemperature cmt these show regional and seasonal variability that is explained by factors including continentality elevation of large massifs or high base levels cold air drainage fog mountain barrier effects and the location of the subtropical high pressure zone lapse rates and projected sea level temperatures based on data from the western united states show distinct regional patterns these indicate that within this region the highest lapse rate and temperature values are correlated with 1 continental climates in the subtropical high pressure zone and 2 areas having relief where the lowest elevation land surfaces base levels occur at high altitude the data are applied to evaluate and revise the methodology for estimating paleoaltitudes variables of climatic change sea level fluctuation and paleogeography are also considered limitations in application of the method are emphasized the method is exemplified by application to the latest eocene florissant flora of colorado u s a although the results are conjectural they strongly suggest that the late eocene erosion surface in the southern rocky mountains occurred at a much higher paleoaltitude than previously thought this high elevation may have resulted from earlier laramide crustal thickening

eruptive and emplacement mechanisms of widespread fine grained pyroclastic deposits on vulcano island italy tufi di grotte dei rossi inferiori are thick ash deposits representing the most voluminous stratigraphic unit on vulcano island the deposits are related to hydromagmatic eruption which occurred under shallow water inside a caldera depression grain size data and results of sem investigation allow the character of the transporting medium solid material concentration in the cloud during the lateral expansion and the nature and role of the fluids present at the time of deposition to be constrained we suggest that the eruption was characterized by closely timed hydromagmatic pulses giving rise to eruption clouds rich in water vapor and steam the coarser material was not significantly transported in the eruptive cloud and it probably deposited in the caldera depression area the finer material was extensively transported in the cloud creating turbulent flows which surmounted the caldera rim barrier and dispersed in a southward direction forming widespread deposits in the piano area lower concentrated flows produced laminated deposits of more limited dispersion whereas higher concentrated flows formed more dispersed thicker massive layers

evolution of dilatancy and permeability in rock salt during hydrostatic compaction and triaxial deformation combined gas permeability and p and s wave velocity measurements were carried out on rock salt samples from the gorleben salt dome and the morsleben salt mine under hydrostatic and triaxial loading condions mostly at room temperature permeabilities in the as received samples vary between 10 16 and 2x10 20 m 2 the initial permeability is primarily due to decompaction induced by drilling core retrieval and sample preparation hydrostatic loading gives rise to a marked decrease of permeability and a coeval significant increase of p and s wave velocities due to progressive closure of grain boundary cracks tending to approach the in situ matrix permeability 18 mpa differential stress at 10 mpa confining pressure to similar to 30 mpa at confining pressures above similar to 70 mpa dilatancy is due to the opening of grain boundary and 100 cleavage cracks and depends on the applied confining pressure the orientation of the open cracks is primarily controlled by the loading geometry system compression extension as a consequence permeability increases dramatically with progressive dilatancy followed by a period of plus minus constant permeability during strain hardening up to 10 axial strain or even more this suggests that the evolution of permeability is not only a function of dilatancy but also of microcrack linkage importantly the anisotropic crack array within the samples causes a strong directional dependence of permeability

volcanological and petrological evolution of vulcano island aeolian arc southern tyrrhenian sea petrological and geochemical data are reported for volcanic rocks from vulcano island the subaerial volcanism 120 ka to present built up a nw se elongated composite structure affected by two intersecting multistage calderas volcanics older than 20 ka consist mostly of high k calc alkaline hkca to shoshonitic sho mafic rocks these magmas interacted significantly with the continental crust which generated variable sr isotopic ratios 0 70412 0 70520 however a major role was also played by input of parental liquids into the magma chamber which prevented further evolution of the magmas hkca sho and potassic ks rocks formed from 20 to 8 ka display a much larger range of sio2 from shoshonites to rhyolites and higher concentrations of incompatible elements with respect to the previous stage sr isotopic ratios show small variations 0 70448 0 70486 mixing of silicic and mafic liquids and fractional crystallization processes fc were the main evolutionary processes during this stage volcanics younger than 8 ka consist of sho and leucite bearing ks mafic rocks with abundant intermediate and silicic products mafic and intermediate rocks display similar incompatible element abundances and sr isotopic ratios as the previous stage volcanics whereas higher 87sr 86sr 0 70494 0 70583 are observed in some rhyolites these products originated from a complex interplay of fc crustal assimilation and magma mixing processes the most mafic rocks show increasing incompatible element abundances rb sr rb ba mg al mg ca and a decrease in large ion lithophile to high field strength element ratios passing from older hkca sho to the younger sho ks volcanics these variations suggest a shifting of magma sources from a slightly metasomatized asthenosphere fertile peridotite to a more strongly metasomatized lithospheric mantle residual peridotite time related petrological and geochemical variations have been used to develop a model for the evolution of the vulcano plumbing system