an experimental study of the kinetics of decompression induced crystallization in silicic melt 1 experiments were conducted to study the temporal evolution of feldspar crystallization kinetics during isothermal decompression pinatubo dacite was held at 780 c 220 mpa fo2 nno 2 h2o saturated conditions for an equilibration period decompressed to final pressures pf ranging from 175 to 5 mpa and then held for 0 3 931 hours according to the plagioclase liquidus curve in ph2o t space for the relevant melt composition these decompressions impose effective undercoolings teff of 34 266 c growth of preexisting phenocrysts and newly formed sparse microlites dominate crystallization at 75 pf 150 mpa teff 34 93 c and equilibrium crystal modes are achieved in 168 hours microlite nucleation is the dominant transformation process for 10 pf 50 mpa teff 125 241 c and chemical equilibrium is not attained by 168 hours under these conditions slow steady decompressions typically produced normally zoned euhedral and planar faceted feldspar crystals although anhedral morphologies were produced at very low pf contrary to expectation slowly decompressed samples were usually further from chemical equilibrium than rapidly decompressed samples after similar durations below the initial pressure although counterintuitive these trends are consistent with new constraints on the relative rates of feldspar nucleation and growth controlled by teff and melt viscosity experienced during each decompression path analysis of liquid to solid transformation kinetics using ttt style diagrams shows that crystallization occurs most rapidly at 100 mpa by a crystal growth mechanism the next most efficient crystallization conditions are at 25 mpa in a crystal nucleation dominated regime

flowgo a kinematic thermo rheological model for lava flowing in a channel we present a kinematic self adaptive numerical model to describe the down flow thermal and rheological evolution of channel contained lava as our control volume of lava advances down a channel it cools and crystallizes an increasingly thick and extensive surface crust grows and its heat budget and rheology evolve by estimating down flow heat and velocity loss our model calculates the point at which the control volume becomes stationary giving the maximum distance lava flowing in the channel can extend modeled effusion rates velocities widths surface crust parameters heat budget cooling temperature crystallinity viscosity and yield strength all compare well with field data collected during eruptions at mauna loa k lauea and etna modeled lengths of 25 27 2 5 5 7 and 0 59 0 83 km compare with measured lengths of 25 27 4 and 0 75 km for the three flows respectively over proximal flow portions we calculate cooling crystallization viscosity and yield strength of 1 10 c km 1 0 001 0 01 volume fraction km 1 103 104 pa s and 10 3 102 pa respectively at the flow front cooling crystallization viscosity and yield strength increase to 100 c km 1 0 1 volume fraction km 1 106 107 pa s and 103 104 pa respectively all of which combine to cause the lava to stop flowing our model presents a means of a analyzing lava flow thermo rheological relationships b identifying important factors in determining how far a channel fed flow can extend c assessing lava flow hazard and d reconstructing flow regimes at prehistoric unobserved or remote flows

treeline and timberline dynamics on the northern and southern slopes of the retezat mountains romania during the late glacial and the holocene abstract to investigate treeline and timberline dynamics in the retezat mountains romanian carpathians late glacial and holocene sediment sequences from four lakes were studied the south and north slopes of the mountain range were compared using two lakes from the north flank lake brazi 1740 m a s l and lake gales 1990 m a s l and two from the south flank lake lia 1910 m a s l and lake bucura 2040 m a s l macrofossil and stomata analyses were performed to assess changes in the local vegetation supplemented by pollen charcoal and loss on ignition analyses our results show that treeline reached lake brazi on the northern side during the late glacial ca 14 000 cal yr bp and then lake gales between 11 000 and 10 800 cal yr bp during the early holocene the upper limit of closed forest the timberline reached and passed lake brazi and has stayed above it since but it has never reached lake gales at 1990 m a s l the expansion of larix decidua in the late glacialand early holocene around lake brazi is unique stomata and macrofossils of abies alba are also more abundant in the northern records on the southern flank treeline reached lake lia at around 12 000 cal yr bp and was either very close to or at the elevation of lake bucura between ca 8600 and 3000 cal yr bp timberline reached lake lia at ca 8000 cal yr bp some 3000 years after lake brazi only 170 m lower on the north slope local fire events delayed the advance of timberline around lake lia in the early holocene in a dry continental climate the surrounding forest was dominated by picea abies with individuals of pinus cembra and stands of p mugo until about 3000 cal yr bp when timberline retreated below the lake maximum elevation of timberline was attained between ca 8000 and 3000 cal yr bp after which it descended in response to climate cooling regional climate change appears to be the main driver of treeline dynamics but it was modified by local climatic differences due to slope aspect the first signs of human disturbance appeared ca 4200 cal yr bp when naturally open areas were used as alpine pastures human impact in the treeline ecotone mainly burning and grazing was intensified after ca 2600 cal yr bp contributing to the widening of the ecotone and the lowering of the timberline

on estimating crystal shape for crystal size distribution analysis abstract the accurate determination of three dimensional crystal habit long intermediate short axis is a requirement to enable correct stereological conversion of 2d crystal size measurements to true 3d crystal size distributions csds in this contribution we introduce a database and spreadsheet program which provides an objective estimate of true crystal habit from raw 2d measurements the database compares the sample s 2d measurements with 2d shape curves for random sections through 703 different habits the output gives the five best match curves and corresponding crystal habits based on a least squares fit between sample and database the minimum sample size required to give good shape estimates from 2d data is tested using random runs of sections through known shapes with different population densities at minimum 75 crystal sections are required to robustly determine crystal habit for csd measurements if crystals are tabular in shape with more acicular shapes requiring a minimum of 250 sections suggesting a sample size of 250 sections to be used for shape determination in natural examples where the true 3d shape is unknown the crystal habit of the best match shape can then be used to provide a more robust csd analysis which in turn can be used to investigate magmatic processes with more certainty

crystal morphologies in pillow basalts implications for mid ocean ridge processes abstract we present the results of a detailed petrological study of a sparsely phyric basalt mapco ch98 dr11 dredged along the mid atlantic ridge 30 41 n the sample contains microphenocrysts of olivine that display four different rapid growth morphologies comparison of these morphologies with those obtained in dynamic crystallization experiments allows us to constrain the thermal history of the sample the dendritic morphology swallowtail chain and lattice olivine is directly related to the final quenching during magma seawater interaction in contrast the three other morphologies namely the complex polyhedral crystal the closed hopper and the complex swallowtail morphology result from several cycles of cooling heating corresponding to a maximum degree of undercooling of 20 25 c during crystal growth these thermal variations occurred before eruption and are interpreted to be the result of turbulent convection in a small magmatic body beneath the ridge the results suggest that the mid atlantic ridge is underlain by a mush zone that releases batches of liquid during tectonic segregation aphyric basalts are emitted during eruptions controlled by the tectonic activity whereas phyric basalts correspond to small fractions of magma from the mush zone mobilized by reinjections of primitive magmas

neolithic to copper age woodland impacts in northeast hungary evidence from the pollen and sediment chemistry records a 4 5 m sedimentary sequence collected from sirok n rjes to in northeast hungary reveals a record of environmental change from 10000 bp to the present day palaeoenvironmental analyses pollen charcoal geochemistry and physical properties of the sequence reveal an environment where parkland com posed of coniferous and broadleaved taxa existing at the start of the holocene developed rapidly into deciduous broadleaved forest from c 8200 cal bp corylus expanded rapidly and dominated the pollen assemblage until a series of fluctuations involving corylus and carpinus betulus which resulted in changes to the forest compo sition these changes occurred over timescales of 72 288 years and are attributed to neolithic and copper age forest use perhaps under a woodland management regime such as coppicing or pollarding sedimentolog ical and geochemical records for this period are stable suggesting that soil erosion was not occurring natural forest processes resumed following copper age settlement shifts bu

magnetic and petrologic characterization of synthetic martian basalts and implications for the surface magnetization of mars 1 a suite of synthetic martian basalts is generated with the objective of providing fundamental material properties data for use in modeling and interpretation of mission data we systematically evaluate the effects of major element composition oxygen fugacity fo2 and cooling rate on phase chemistry and magnetic mineralogy grain size and intensity of remanent magnetization the range of experimental compositions and fo2 are chosen to bracket the range expected in the martian crust our results should therefore span the range of possible mineralogies textures and magnetic properties in rapidly cooled mars crustal materials two starting compositions are used for the sample synthesis 1 an fe rich al poor composition patterned after snc basaltic meteorites and 2 a composition based on thermal emission spectrometer tes data with a much lower fe al ratio the resulting magnetic phase in samples generated at the quartz fayalite magnetite qfm buffer is a spinel structured oxide with varying amounts of cr ti mg and al compositional differences depend on bulk composition cooling rate differences in crystallization sequence and the kinetics of silicate mineral nucleation and growth oxide abundance and magnetic intensity are most strongly influenced by fo2 with more subtle composition and cooling rate effects moderately oxidizing qfm conditions result in an intense magnetization 2 3 10 5 am2 kg 1 to 1 4 10 2 am2 kg 1 especially in the meteorite derived basalts however an increase of magnetic grain size into the multidomain range meteorite type and or low unblocking temperatures resulting from increased cr substitution tes type may affect the long term stability of the remanence in qfm samples

late holocene hydrous mafic magmatism at the paint pot crater and callahan flows medicine lake volcano n california and the influence of h2o in the generation of silicic magmas this paper characterizes late holocene basalts and basaltic andesites at medicine lake volcano that contain high pre eruptive h2o contents inherited from a subduction related hydrous component in the mantle the basaltic andesite of paint pot crater and the compositionally zoned basaltic to andesitic lavas of the callahan flow erupted approximately 1000 14c years before present 14c years b p petrologic geochemical and isotopic evidence indicates that this late holocene mafic magmatism was characterized by h2o contents of 3 to 6 wt h2o and elevated abundances of large ion lithophile elements lile these hydrous mafic inputs contrast with the preceding episodes of mafic magmatism from 10 600 to 3000 14c years b p that was characterized by the eruption of primitive high alumina olivine tholeiite haot with low h2o 0 2 wt lower lile abundance and different isotopic characteristics thus the mantle derived inputs into the medicine lake system have not always been low h2o primitive haot but have alternated between haot and hydrous subduction related calc alkaline basalt this influx of hydrous mafic magma coincides temporally and spatially with rhyolite eruption at glass mountain and little glass mountain the rhyolites contain quenched magmatic inclusions similar in character to the mafic lavas at callahan and paint pot crater the influence of h2o on fractional crystallization of hydrous mafic magma and melting of pre existing granite crust beneath the volcano combined to produce the rhyolite fractionation under hydrous conditions at upper crustal pressures leads to the early crystallization of fe mg silicates and the suppression of plagioclase as an early crystallizing phase in addition h2o lowers the saturation temperature of fe and mg silicates and brings the temperature of oxide crystallization closer to the liquidus these combined effects generate sio2 enrichment that leads to rhyodacitic differentiated lavas in contrast low h2o haot magmas at medicine lake differentiate to iron rich basaltic liquids when these fe enriched basalts mix with melted granitic crust the result is an andesitic magma since mid holocene time mafic volcanism has been dominated primarily by hydrous basaltic andesite and andesite at medicine lake volcano however during the late holocene h2o poor mafic magmas continued to be erupted along with hydrous mafic magmas although in significantly smaller volumes

chironomid inferred holocene temperature changes in the south carpathians romania we present a holocene summer air temperature reconstruction based on fossil chironomids from lake brazi 1740 m a s l a shallow mountain lake in the south carpathians summer air temperature rec

application of a textural geospeedometer to the late stage magmatic history of mil 03346 dynamic crystallization experiments performed on fe rich al poor basalt are employed as a textural calibration set to quantify the late stage igneous history of nakhlite miller range mil 03346 the ratio of crystal melt surface area to volume typifying morphologically distinct populations of ca pyroxene has been shown to vary as a strong function of cooling rate hammer 2006 furthermore a texture of phenocrysts surrounded by finer grained groundmass crystals arises by sequential nucleation events during constant rate cooling but multiple populations nucleate only if the cooling rate is 72 c h 1 textural analysis of meteorite mil 03346 reveals at least two distinct populations the ca pyroxene phenocryst and microphenocryst three dimensional 3d aspect ratios are 112 8 3 and 1530 160 mm 1 respectively by comparison with the calibration set the range of cooling rates consistent with 3d aspect ratios of both populations in mil 03346 is 20 c h 1 an additional experiment was performed approximating a conductive heat transfer profile in order to interpret and apply results of constant rate cooling experiments to the natural cooling of magma results suggest that the textures of constant rate experiments parallel the initial period of rapid cooling in natural magma initial cooling rates of 20 c h 1 in the lava hosting mil 03346 occur in conductively solidifying lava at depths of 0 4 m constraining the minimum total thickness to 0 8 m crystal accumulation beginning in a subsurface reservoir and continuing after lava emplacement as an inflated pahoehoe sheet satisfies all textural constraints on the late stage igneous history of mil 03346

recurring taiga forest steppe habitats in the carpathian basin in the upper weichselian many loess pro les some lake sediments and archaeological sites in di erent parts of the carpathian basin were analysed in respect of their geology sedimentology molluscs and macro charcoal remains radiocarbon dating was also carried out on charcoal remains as well as on molluscan shells the loess pro les prove to have been formed during the last glacial period between ca 70 000 and 15 000 years bp two well developed and a weakly developed charcoal layer can be found at the sites dating from that period all rest on the top of a palaeosol on the basis of palaeoecological investigations of these charcoal layers and the molluscs found within the loess it is concluded that recurring boreal forest steppe habitats characterised the carpathian basin the woodlands mostly consisting of picea trees in the north and pinus sylvestris in the south as well as six other arboreal species by reference to the subsequent charcoal layers reforestation occurred every 2000 5000 years with the same composition although their density may have varied these forests thus recur in the same places after extensive forest res how often and why these reforestation events took place and how much time was needed for the forests steppes to redevelop needs further clari cation 2001 published by elsevier science ltd

late quaternary expansion of norway spruce picea abies l karst in europe according to pollen data abstract lateglacial and holocene expansion of norway spruce picea abies l karst in europe is reconstructed in steps of 1000 radiocarbon years on the basis of pollen data collected from literature and databases pollen thresholds for the lateglacial of 0 1 2 5 and 10 and for the holocene of 2 were used spruce pollen representation and limitations of pollen data are discussed we assume that the 2 threshold tracks the advance of the main spruce front but might fail to detect small populations or those present in low density the history of spruce expansion was distinctly different in northern and southern parts of its range 1 in ne europe spruce expanded during the allerod reaching southwards to n byelorussia during the younger dryas spruce populations contracted north of ca 60 n but expanded strongly in the region approximately 53 60 n 23 32 e where they declined at the beginning of the holocene we infer that the lateglacial expansion in ne europe concerned mainly p abies subsp obovata 2 holocene expansion in n europe concerned mainly p abies subsp abies southward expansion within the northern range is continuing to the recent millennium 3 in central europe spruce expanded vigorously during the allerod contracted or stagnated during the younger dryas and then strongly re expanded during the preboreal following the simple expectation that climatic warming had a positive impact on its development 4 holocene westward and northward expansion of spruce in its southern range central europe was rapid 10 8 ka 14 c bp very slow 8 6 ka 14 c bp and rapid 6 5 ka 14 c bp when the present day western limits were reached 5 the 2 spruce pollen threshold is too high to detect the fact that the northern and southern ranges of spruce have joined in the holocene the persistence of low spruce abundance in the transitional area is explained mainly by the strong anthropogenic deforestation ever since spruce grew there

late holocene palaeoclimate variability the significance of bog pine dendrochronology related to peat stratigraphy the puścizna wielka raised bog case study orawa nowy targ basin polish inner carpathians abstract the results of dendrochronological and palynological analyses of subfossil pine trees occurring in the peat deposits of the pu cizna wielka raised bog polish carpathians southern poland the only site with numerous subfossil pine trees in the mountainous regions of central europe presently known indicate that the majority of the tree populations grew in the peat bog during the periods ca 5415 3940 cal bp and 3050 2560 cal bp several forestless episodes dated to 5245 5155 cal bp 4525 4395 cal bp and 3940 3050 cal bp were preceded by tree dying off phases caused by an extreme periodical increase in humidity and general climate cooling trends these events are documented based on analyses of pollen and non pollen palynomorph assemblages dendrochronological analyses of the trees as well as numerous radiocarbon datings of the sediment horizons occurring within the peat bog profile the phases of germinations and in turn of tree and shrub invasions of the peat bog areas have been closely connected to drying and occasional warming of the regional climate the last of the forestless periods began about 2600 years ago and continued up to the very recent times currently as a result of desiccation of the peat bog and the lowering of the groundwater level due to improved water drainage system pine trees have returned the peat bog again these results demonstrate that studies of subfossil bog pine trees are quite effective in documenting and reconstructing periods of humidity fluctuation that occurred within the carpathian region over the last several millennia

formation of a martian pyroxenite a comparative study of the nakhlite meteorites and theo s flow the unusual composition of the nakhlites a group of pyroxenitic martian meteorites with young ages presents an opportunity to learn about nonbasaltic magmatic activity on another planet however the limited number of these meteorites makes unraveling their history difficult a promising terrestrial analog for the formation of the nakhlites is theo s flow in ontario canada this atypical 120 m thick flow differentiated in place forming distinct layered lithologies of peridotite pyroxenite and gabbro theo s pyroxenite and the nakhlites share strikingly similar petrographies with concentrated euhedral to subhedral augite grains set in a plagioclase rich matrix these two suites of rocks also share specific petrologic features mineral and whole rock compositional features and size and spatial distributions of cumulus grains the numerous similarities suggest that the nakhlites formed by a similar mechanism in a surface lava flow or shallow intrusion their formation could have involved settling of crystals in a phenocryst laden flow or in situ nucleation and growth of pyroxenes in an ultramafic lava flow the latter case is more likely and requires steady state nucleation and growth of clusters of pyroxene grains and olivine in the nakhlites circulating in a strongly convecting melt pool followed by settling and continued growth in a thickening cumulate pile trapped pockets of intercumulus liquid in the pile gradually evolved finally growing fe enriched rims on cumulus grains with sufficient evolution the melt reached plagioclase supersaturation causing rapid growth of plagioclase sprays and late stage mesostasis growth

response of a spring fed fen ecosystem in central eastern europe nw romania to climate changes during the last 4000 years a high resolution multi proxy reconstruction we document the long term development of a spring fed fen assessing its sensivity to climate changes over the last ca 4000 years our investigation is based on high resolution continuous plant macrofossil remains and mollusc records complemented by pollen geochemical analysis and radiocarbon dating of valea morii located in the feleac hills transylvanian depression in nw romania central eastern europe based on our palaeocological data we have distinguished three stages of wet habitat conditions two stages between 4000 and 2450 cal yr bp and one in the last 800 cal yr bp and one dry stage between ca 2450 and 800 cal yr bp these local habitat conditions appear to reasonably reflect regional climate characteristics high resolution analysis of two replicated cores documented a mostly comparable pattern of local plant and mollusc succession and stable isotope values from ca 500 cal yr bp the appearance of c mariscus during the last two centuries may be related to increased wetness and associated active caco3 precipitation which allowed this plant to colonise the spring fed fen studied however it can be not excluded that the occurrence and spread of a cladium mariscus population at this site during the last two centuries might have been partly favoured by the warming of the climate after the little ice age the potential of carbonate oxygen stable isotope values as an indicator of major trends in climatic change both temperature and humidity in mountain spring fed fen deposits is shown carbon isotopes in the carbonates were found to be useful in reconstruction of changes in vegetation soil development and the dissolution of bedrock carbonates primarily as a reaction to changes in climate humidity

the late quaternary environmental history of batorliget n e hungary abstract a sedimentary sequence extending back into the last glacial has been obtained from batorliget marsh in n e hungary reconstruction of the environmental history of the region using the techniques of pollen analysis molluscan analysis and geochemistry has revealed an important late quaternary refugium during the last glacial a refugium for temperate flora and fauna existed within a landscape dominated by coniferous forest predominantly made up of pinus and picea the lateglacial postglacial transition at 10 000 yr b p resulted in a dramatic shift from coniferous but also including betula woodland to deciduous woodland following the lateglacial postglacial transition a highly diverse woodland became established in the early postglacial accompanied by an equally diverse molluscan assemblage this diversity remained throughout the early postglacial although the types present within the woodland changed a number of times at c 7000 yr b p anthropogenic disturbance resulted in the destruction of the mixed forest and the development of agricultural land the importance of this region as a refugial area both in the lateglacial and early postglacial is discussed and the influence that it had on the postglacial development of the fauna and flora of northeastern hungary is reviewed

the parent magma of the nakhla snc meteorite inferred from magmatic inclusions abstract the nakhla meteorite one of the snc group of putative martian origin is an igneous rock a cumulate of augite and olivine that does not represent a magma composition samples of its parent magma were trapped as magmatic inclusions in its cumulus olivine crystals the inclusions range from 10 350 m in diameter and consist of augite rich in ti and al silica rich glass iron oxides ilmenite apatite and rare amphibole each inclusion has a rind of augite and chromite against its host olivine and a core of radiating sprays of augite set in glass and feldspar these textures are consistent with an origin as trapped silicate liquid twenty four inclusions were analyzed by electron microprobe by averaging series of rastered beam analyses on average the analyses are independent of the size of the inclusion most clearly for inclusions larger than 70 m diameter and variations among analyses are consistent with small differences in the proportions of augite glass and iron oxides exposed on thin section surfaces the average inclusion analysis is calculated to represent 28 host olivine and 72 inclusion composition the inclusion rinds are calculated to be 13 of the inclusion composition for which a small correction is made the inclusion composition is then corrected for mg fe exchange with the host olivine to chemical equilibrium with the cumulus augite cores and crystallization of 13 olivine onto the host crystal to yield a magma composition with the proper mgo feo ratio and with olivine and augite on its liquidus this composition nk93 is an estimate of nakhla s parent magma originally trapped in the inclusions nk93 is basaltic rich in iron and poor in aluminum compared to terrestrial basalts its abundances of al ti and na are consistent with the geochemistry of the snc meteorites as a whole nk93 is similar to the parent magmas proposed in an independent study of magmatic inclusions in nakhla but unlike other proposed compositions one proposed parent magma based on mass balance and the assumption that nakhla was a closed system after crystal accumulation is inconsistent with the magmatic inclusion studies and nakhla s petrography this suggests that nakhla was not a closed system but was infiltrated by post cumulus basaltic magmas another suggested parent magma was derived from element distribution between augite and basaltic magma but that calculation relied on an incorrect augite composition using a correct augite composition in that calculation yields a parent magma much closer in composition to nk93 thus three independent approaches converge in requiring that nakhla originally formed from a low al low mgo feo basalt like nk93

petrogenesis of the nakhlite meteorites evidence from cumulate mineral zoning abstract a simple igneous petrogenesis for the meteorite nakhla has previously been called into question because mg fe ratios in olivine indicate substantial disequilibrium between the predominant cumulus minerals olivine and augite comparative analyses of simulated diffusive zoning and the observed cumulus mineral zoning for all three nakhlites nakhla governador valadares and lafayette show that their current compositions do not necessarily reflect parental magma compositions instead diffusion has altered primary cumulus compositions to varying degrees nakhla being the least affected and lafayette being almost completely re equilibrated only the cores of augite grains in nakhla and governador valadares appear to have preserved their original compositions mineral zoning in each meteorite is strongly concentric around mesostasis areas suggesting that reaction with intercumulus liquid has controlled the observed zoning the presence of pigeonite and orthopyroxene overgrowths in nakhla and governador valadares and of poikilitic orthopyroxene enclosing olivine relicts in lafayette indicate substantial late magmatic reactions two pyroxene geothermometry for lafayette indicates temperatures around 950 c suggesting subsolidus equilibration as well the nakhlites appear to be a series of relatively simple cumulate rocks which have undergone various amounts of late magmatic and subsolidus diffusion possibly reflecting their relative positions in a cooling cumulate pile

the full glacial forests of central and southeastern europe the presence of trees in central and southern europe during the last full glaciation has long been a matter of debate a low but persistent presence of fossil tree pollen in central and southern european full glacial paleoecological sequences has been interpreted either as representing long distance pollen transport from southerly refuges or as representing in situ refugial populations here we present macroscopic charcoal results from 31 sequences located throughout hungary that provide unequivocal evidence for the presence of at least seven different tree types between approximately 32 500 and 16 500 14c yr b p this evidence is presented in conjunction with molluscan and pollen analyses to indicate that during the last full glaciation trees grew as far north as hungary probably in microenvironmentally favorable sites these areas provided an important cold stage refugium for the european flora and fauna

vegetation and environmental responses to climate forcing during the last glacial maximum and deglaciation in the east carpathians attenuated response to maximum cooling and increased biomass burning the carpathian mountains were one of the main mountain reserves of the boreal and cool temperate flora during the last glacial maximum lgm in east central europe previous studies demonstrated lateglacial vegetation dynamics in this area however our knowledge on the lgm vegetation compo sition is very limited due to the scarcity of suitable sedimentary archives here we present a new record of vegetation fire and lacustrine sedimentation from the youngest volcanic crater of the carpathians lake st anne lacul sf ana szent anna tto examine environmental change in this region during the lgm and the subsequent deglaciation our record indicates the persistence of boreal forest steppe vegetation with pinus betula salix populus and picea in the foreland and low mountain zone of the east carpathians and juniperus shrubland at higher elevation we demonstrate attenuated response of the regional vegetation to maximum global cooling between 22 870 and 19 150 cal yr bp we find increased regional biomass burning that is antagonistic with the global trend increased regional fire activity suggests extreme continentality likely with relatively warm and dry summers we also demonstrate xerophytic steppe expansion directly after the lgm from 19 150 cal yr bp and regional increase in boreal woodland cover with pinus and betula from 16 300 cal yr bp plant macrofossils indicate local 950 m a s l establishment of betula nana and betula pubescens at 15 150 cal yr bp pinus sylvestris at 14 700 cal yr bp and larix decidua at 12 870 cal yr bp pollen data furthermore support population genetic inferences regarding the regional presence of some temperate deciduous trees during the lgm fagus sylvatica corylus avellana fraxinus excelsior our sedimentological data also demonstrate intensified aeolian dust accumulation between 26 000 and 20 000 cal yr bp

petrology of the miller range 03346 nakhlite in comparison with the yamato 000593 nakhlite we petrologically examined the miller range mil 03346 nakhlite the main phase modal abundances are 67 7 vol augite 0 8 vol olivine and 31 5 vol mesostasis among all known nakhlites mil 03346 s modal abundance of olivine is the smallest and of mesostasis is the largest augite occurs as cumulus phenocrysts having a homogeneous core composition en36 38fs24 22wo40 which is identical with other nakhlites they accompany thin ferroan rims divided into inner and outer rims with a compositional gap at the boundary between the two rims olivine grains have magnesian cores fa 55 and show normal zoning toward ferroan rims fa 84 mesostasis consists mostly of glass 26 0 vol with minor skeletal fayalites skeletal titanomagnetites acicular phosphate massive cristobalite and sulfides we conclude that mil 03346 is the most rapidly cooled nakhlite among all known nakhlites based on the petrography we obtain the intercumulus melt composition for mil 03346 from the mass balance calculation using the modal abundances and discuss the crystallization sequence of mil 03346 in comparison with that of yamato y 000593 although magnesian olivines of y 000593 are phenocrystic magnesian olivine grains of mil 03346 seem to have texturally crystallized from the intercumulus melt after the mil 03346 magma intruded upward to the martian surficial zone the magnesian olivine crystallized and then the ferroan inner rim formed on phenocrystic core augite the outer rim of phenocrystic augites formed after the crystallization of skeletal fayalites and skeletal titanomagnetites resulting in a compositional gap between the inner and outer rims finally glassy mesostasis formed from the residual melt this crystallization sequence of mil 03346 is different from those of other nakhlites including y 000593

the parent magma of the nakhlite meteorites clues from melt inclusions abstract several forms of trapped liquid found within nakhlite meteorites have been examined including interstitial melt and magmatic inclusions within the cores of large olivine grains differences in the mineralogy and texture between two types of trapped melt inclusions and between these inclusions and the mesostasis indicate that vitrophyric inclusions are most appropriate for estimating the composition of a nakhlite parental magma in equilibrium with early forming olivine and augite parent liquids were calculated from the mineralogy of large inclusions in nakhla and governador valadares using a system of mass balance equations solved by linear regression methods the chosen parental liquids were cosaturated in olivine and augite and had mg fe values consistent with measured augite liquid kd s these parental magma compositions are similar to other published compositions for nakhla chassigny and shergotty parental melts and may correspond to a significant magma type on mars

rapid vegetation response to lateglacial and early holocene climatic fluctuation in the south carpathian mountains romania abstract high resolution pollen conifer stomata and plant macrofossil analyses of two glacial lake sediments 1740 and 1990 m a s l are used to reconstruct lateglacial lg and early holocene eh vegetation and tree line changes in the retezat mountains our results show that during the lg tree line was between 1750 and 1800 m a s l formed by larix decidua pinus mugo and picea abies early lg spread to high altitudes suggests refugia of these tree species in the mountain the younger dryas cooling resulted in regional steppe tundra expansion but tree line position and composition showed little change the abundance of trees and shrubs decreased at 1740 m a s l but species richness increased with the arrival of pinus cembra our data support climate model hindcasts for only modest decrease in accumulated growing season heat at mid high altitudes regionally the pollen records suggest enhanced aridity and seasonality in the eh tree line reached 2000 m a s l higher than today by 11 100 cal yr bp p mugo p cembra p abies established around the upper lake suggesting rapid increase in summer temperatures the eh maximum of l decidua between 11 200 10 600 cal yr bp was connected to high summer insolation high altitude expansion of abies alba between 10 600 10 300 cal yr bp suggested summer mean temperatures 2 8 c higher then today in comparison with other mountain sites in europe lg interstadial tree line was at similar altitude in the s alps and 350 m higher in the pirin mountains lg tree line fluctuation had similar low amplitude in the se alps retezat and pirin mts suggesting relatively weak influence of the north atlantic thermohaline circulation changes on growing season temperatures

petrology of the yamato nakhlites the yamato nakhlites y 000593 y 000749 and y 000802 were recovered in 2000 from the bare icefield around the yamato mountains in antarctica consisting of three independent specimens with black fusion crusts they are paired cumulate clinopyroxenites we obtained the intercumulus melt composition of the yamato nakhlites and here call it the yamato intercumulus melt yim the yim crystallized to form the augite rims the olivine rims and the mesostasis phases in the cumulates the augite rims consist of two layers inner and outer the crystallization of the inner rim drove the interstitial melt into the plagioclase liquidus field subsequently the residual melt crystallized pigeonites and plagioclase to form the outer rims and the mesostasis three types of inclusions were identified in olivine phenocrysts rounded vitrophyric angular vitrophyric and monomineralic augite inclusions the monomineralic augite inclusions are common and may have been captured by growing olivine phenocrysts the rounded vitrophyric inclusions are rare and may represent the composition of middle stage melts whereas the angular vitrophyric inclusions seem to have been derived from fractionated late stage melts glass inclusions occur in close association with titanomagnetite and ferroan augite halo in phenocryst core augites and the assemblages may be magmatic inclusions in augites we compared the yim with compositions of magmatic inclusions in olivine and augite the composition of magmatic inclusions in augite is similar to the yim phenocrystic olivines contain exsolution lamellae augite magnetite aggregates and symplectites in the cores the symplectites often occur at the boundaries between olivine and augite grains the aggregates symplectite and lamellae formed by exsolution from the host olivine at magmatic temperatures we present a formational scenario for nakhlites as follows 1 accumulation of augite olivine and titanomagnetite phenocrysts took place on the floor of a magma chamber 2 olivine exsolved augite and magnetite as augite magnetite aggregates symplectites and lamellae 3 the overgrowth on olivine phenocrysts formed their rims and the inner rims crystallized on augite phenocryst cores and finally 4 the outer rim formed surrounding the inner rims of augite phenocrysts and plagioclase and minor minerals crystallized to form mesostasis under a rapid cooling condition probably in a lava flow or a sill

holocene forest dynamics in northwestern romnania pollen analyses and ams radiocarbon measurements were carried out on peat deposits from the former crater lake preluca tiganului located in a mid altitude area of the gutaiului mountains nw romania in order to reconstruct the postglacial vegetation history at the lateglacial holocene transition the open vegetation was replaced by forest suggesting a fast response to climatic warming the rapid expansion of pinus betula and later picea may be due to their existence in the area during the lateglacial at approximately 11 250 cal yr bp the dense forest was composed primarily of ulmus and some picea betula and pinus a small population of ulmus might also have survived in the area during the lateglacial at 10750 cal yr bp quercus tilia and fraxinus followed by corylus at c 10200 cal yr bp expanded significantly in the forest the delay of approximately 550 years in their establishment as compared to the expansion of ulmus was probably due to their immigration from more distant localities

temperature constraints on the ginkgo flow of the columbia river basalt group this study provides the first quantitative estimate of heat loss for a columbia river basalt group flow a glass composition based geothermometer was experimentally calibrated for a composition representative of the 500 km long ginkgo flow of the columbia river basalt group to measure temperature change during transport melting experiments were conducted on a bulk sample at 1 atm between 1200 and 1050 c natural glass was sampled from the margin of a feeder dike near kahlotus washington and from pillow basalt at distances of 120 km vantage washington 350 km molalla oregon and 370 km portland oregon ginkgo basalt was also sampled at its distal end at yaquina head oregon 500 km comparison of the glass mgo content k 2 o in plagioclase and measured crystallinities in the experimental charges and natural samples tightly constrains the minimum flow temperature to 1085 5 c glass and plagioclase compositions indicate an upper temperature of 1095 5 c thus the maximum temperature decrease along the flow axis of the ginkgo is 20 c suggesting cooling rates of 0 02 0 04 c km these cooling rates substantially lower than rates observed in active and historic flows are inconsistent with turbulent flow models calculated melt temperatures and viscosities of 240 750 pa s allow emplacement either as a fast laminar flow under an insulating crust or as a slower inflated flow

effects of martian conditions on numerically modeled cooling limited channelized lava flows 1 we used the flowgo thermorheological model to examine the effects of martian gravitational and environmental conditions on the cooling limited behavior of lava flowing in a channel the largest effect is due to the lower gravity on mars as compared to earth which causes lava to flow more slowly the lower velocity means that heat loss per distance down a mars channel is greater even though the lower velocity also produces a higher percentage cover of insulating crust gravity alone causes the mars flow to be 65 km shorter than an earth flow with an equivalent volumetric flow rate the cooler ambient mars atmosphere causes a slight increase in heat loss by forced convection this slows the flow a bit more resulting in a very slight increase in heat loss per distance by all mechanisms and decreases the modeled flow length by 1 km a difference well below our model uncertainty replacing terrestrial values of atmospheric density viscosity thermal conductivity heat capacity and cubic expansivity makes convection less efficient and increases flow length by 15 km nevertheless at the same volumetric flow rate lava flows 50 km less far under martian conditions than under terrestrial conditions our specific model flow has a volumetric flow rate of 5000 m3 s 1 and traveled 190 km down a channel on a constant 7 slope this volumetric flow rate is slightly less than the maximum rates during the 1783 1785 laki eruption and is 5 10 times greater than those of typical mauna loa eruptions

chemical stratigraphy iceland research drilling project reydarfjordur eastern iceland major element data are reported for lavas and dikes from a 3 2 km section through the eastern iceland lava pile the section includes a 1 2 km subaerial exposure and a 1 9 km sequence drilled by the iceland research drilling project irdp alteration increases down section although primary magma chemistry may be interpreted from feo al2o3 tio2 p2o5 and to a lesser extent sio2 in addition to immobile trace elements lava compositions range from mgo rich tholeiite to sio2 rich icelandite while dikes range from tholeiite to tholeiitic andesite three stratigraphic divisions based on volcanologic and trace element criteria e g ce yb and zr y are confirmed by major elements upper and lower groups are predominantly basaltic while the middle group includes a high proportion of silicic lavas variation within groups conforms to simple models combining fractional crystallization and accumulation of phenocryst plagioclase during build up of the pile eruptive phases commenced with silica rich magma and frequently terminated with basaltic or intermediate plagioclase cumulates dike chemistry resembles that of upper group lavas and also the nearby breiddalur volcano middle group lavas probably derive from a buried silicic complex while the lower group may represent the flank of a more deeply buried complex chemical stratigrapy is consistent with iterative burial with spreading of lenticular basaltic silicic complexes magma supply fractionation and mixing are considered in the framework of such kinematic models although it is premature to draw direct analogies to the active neogene zone of iceland

the importance of pahoehoe abstract pahoehoe lava flows are common in every basaltic province and their submarine variants pillow lavas and sheet flows cover the bulk of the earth pahoehoe flows are emplaced by inflation the injection of molten lava underneath a solidified crust only in the past few years has an understanding of the inflation process and the ability to recognize ancient inflated lava flows been achieved all large terrestrial basaltic flow fields studied to date including flood basalts were emplaced as thermally efficient inflated compound pahoehoe sheet flows this leads us to propose that this is the standard way of emplacing large lavas the swell hypothesis the atmospheric impact of such flood basalt eruptions could have been protracted and severe providing a plausible link between flood basalt eruptions and mass extinctions

the initial cooling of pahoehoe flow lobes in this paper we describe a new thermal model for the initial cooling of pahoehoe lava flows the accurate modeling of this initial cooling is important for understanding the formation of the distinctive surface textures on pahoehoe lava flows as well as being the first step in modeling such key pahoehoe emplacement processes as lava flow inflation and lava tube formation this model is constructed from the physical phenomena observed to control the initial cooling of pahoehoe flows and is not an empirical fit to field data we find that the only significant processes are a heat loss by thermal radiation b heat loss by atmospheric convection c heat transport within the flow by conduction with temperature and porosity dependent thermal properties and d the release of latent heat during crystallization the numerical model is better able to reproduce field measurements made in hawai i between 1989 and 1993 than other published thermal models by adjusting one parameter at a time the effect of each of the input parameters on the cooling rate was determined we show that a the surfaces of porous flows cool more quickly than the surfaces of dense flows b the surface cooling is very sensitive to the efficiency of atmospheric convective cooling and c changes in the glass forming tendency of the lava may have observable petrographic and thermal signatures these model results provide a quantitative explanation for the recently observed relationship between the surface cooling rate of pahoehoe lobes and the porosity of those lobes jones 1992 1993 the predicted sensitivity of cooling to atmospheric convection suggests a simple field experiment for verification and the model provides a tool to begin studies of the dynamic crystallization of real lavas future versions of the model can also be made applicable to extraterrestrial submarine silicic and pyroclastic flows

crystallization history of the 1984 mauna loa lava flow during a 3 week eruption in 1984 mauna loa produced vent lavas that increased in crystallinity from 1 to 30 and 27 km long flows that increased in crystallinity as they moved downstream we examined the crystallization history of these lavas using crystal size distribution csd analysis to study the rates of crystallization viscosity increase and latent heating typical average growth and nucleation rates were 5 10 9 cm s 1 and 5 cm 3 s 1 for microphenocrysts 20 to 500 m size crystals nucleated in the rift zone and 5 10 8 cm s 1 and 5 104 cm 3 s 1 for microlites 1 to 20 m size crystals nucleated in the channel these crystallization rates are high compared with those found in other csd studies of igneous rocks probably due to highly nonequilibrium conditions brought on by rapid degassing in the rift zone and cooling in the lava channel growth and nucleation rates decreased with time at the vent and with distance downstream the maximum downstream total crystallinity measured is 39 25 microlites 14 microphenocrysts in a quenched sample 14 km from the vent growth and nucleation rates cannot be calculated for postemplacement samples but they place upper limits of 53 58 on the amount of crystallization in the channel 9 20 km from the vent crystallization could have been mostly responsible for the 105 fold downstream increase in apparent viscosity although degassing and increasing incorporation of solid lava fragments also contributed another effect of crystallization on the lava flow was the sizeable latent heating 0 01 j g 1 s 1 over the first half of the flow length if the crystallinity of downstream quench samples is representative of the hot fluid core which may have been counteracted by entrainment of cooler material measurements of crystallization are shown to be crucial in the study of lava flow emplacement dynamics

non newtonian rheological law for highly crystalline dome lavas volcanic eruption models are hampered by the lack of multiphase magmatic flow laws most rheological models estimate the viscosity of multiphase lavas via the einstein roscoe equation but this simplification cannot be used for high crystallinity and it does not consider the non newtonian strain rate dependence of viscosity we carried out parallel plate experiments on natural samples to simulate multiphase lava deformation under various stresses and strain rates multiphase lavas exhibit an important component of shear thinning and appear to invalidate the adequacy of einstein roscoe based formulations for highly crystalline lava rheology the remarkable singular dependence of viscosity on strain rate yields a novel universal rheology law at eruptive temperatures t i e log 0 993 8974 t 0 543 log our work reveals the importance of considering microcracking and viscous dissipation at very high strain rate 10 3 s 1 explaining the occurrence of seismic swarms along the conduit margins and consequently supporting plug like magma ascent models

hawaiian lava flows in the third dimension identification and interpretation of pahoehoe and a a distribution in the kp 1 and soh 4 cores 1 hawaiian lava flows are classified as pahoehoe or a a by their surface morphology as surface morphology reflects flow emplacement conditions the surface distribution of morphologic flow types has been used to study the evolution and eruptive history of basaltic volcanoes we extend this analysis to the third dimension by determining the distribution of flow types in two deep drill cores the scientific observation hole 4 soh 4 core drilled near kilauea s east rift zone erz and the pilot hole kahi puka 1 kp 1 for the hawaiian scientific drilling project hsdp drilled through distal flows from mauna loa and mauna kea flows are classified using both internal structures and groundmass textures with the latter useful when identification based on mesoscopic flow features e g surface morphology and vesicle content and distribution is ambiguous we then examine the temporal distribution of pahoehoe and a a flows in proximal soh 4 and distal kp 1 settings sequence analysis shows that the two flow types are not randomly distributed in either core but instead are strongly clustered the proximal soh 4 core is dominated by thin pahoehoe flows 60 by volume consistent with the common occurrence of surface fed pahoehoe flows in near vent settings the distal kp 1 core has a high proportion of a a 58 by volume although the proportion of pahoehoe and a a varies dramatically throughout the mauna kea sequence thick inflated pahoehoe flows dominate when the drill site was near sea level consistent with the numerous inflated pahoehoe fields on the current coastal plains of kilauea and mauna loa a a flows are abundant when the site was far above sea level as slope increases from the coastal plains to mauna kea s flank this correlation may reflect the combined effect of long transport distances and increased slopes on flow emplacement these results demonstrate that flow type and thickness variations in cores provide valuable information about both vent location and local site environment observed variations in flow type within the kp 1 core raise interesting questions about feedback between volcano evolution and flow morphology and suggest that flow type is an important variable in models of volcano growth and related models for lava flow hazard assessment

observations on basaltic lava streams in tubes from kilauea volcano island of hawai i from 1986 to 1997 the pu u o o kupaianaha eruption of kilauea produced a vast pahoehoe flow field fed by lava tubes that extended 10 12 km from vents on the volcano s east rift zone to the ocean within a kilometer of the vent tubes were as much as 20 m high and 10 25 m wide on steep slopes 4 10 a little farther away from the vent some tubes formed by roofing over of lava channels lava streams were typically 1 2 m deep flowing within a tube that here was typically 5 m high and 3 m wide on the coastal plain 1 tubes within inflated sheet flows were completely filled typically 1 2 m high and several tens of meters wide tubes develop as a flow s crust grows on the top bottom and sides of the tubes restricting the size of the fluid core the tubes start out with nearly elliptical cross sectional shapes many times wider than high broad flat sheet flows evolve into elongate tumuli with an axial crack as the flanks of the original flow were progressively buried by breakouts temperature measurements and the presence of stalactites in active tubes confirmed that the tube walls were above the solidus and subject to melting sometimes the tubes began downcutting progressive downcutting was frequently observed through skylights a rate of 10 cm d was measured at one skylight for nearly 2 months

exposure matters forest dynamics reveal an early holocene conifer refugium on a north facing slope in central europe although several studies provide a broad overview of vegetation changes in the carpathian basin during the holocene stand scale vegetation changes are lesser known because of the rarity of suitabl

variable slip rupture model of the great 1923 kanto japan earthquake geodetic and body waveform analysis abstract the available geodetic and teleseismic data sets for the 1923 kanto earthquake m s 8 1 have been combined into a joint inversion for both temporal and spatial slip variations we assumed an initial faulting model to be consistent with the geometry determined by kanamori 1971 on the basis of first motion data aftershock area and the amplitude of surface waves at teleseismic distances and also to enclose the slipped area estimated by matsu9ura et al 1980 from the geodetic data employed here we then inverted for a heterogeneous distribution of slip of the fault plane the leveling routes and triangulation stations used consisting of 225 bench marks and 31 triangulation points are from matsu9ura et al 1980 we chose to first determine the overall static slip distribution by inverting the geodetic data alone we then proceeded to gradually increase the importance of the teleseismic data always requiring a good fit to the geodetic leveling and horizontal displacements in this way we could provide a constraint on the overall static slip characteristics from the geodetic data and provide stability for the teleseismic inversion yet determine the degree of slip heterogeneity and time history most suitable for matching the waveform data and for simulating strong ground motions our analysis yields a seismic moment of 7 to 8 10 27 dyne cm m w 7 8 to 7 9 with a maximum slip of approximately 8 m the most concentrated slip is in the shallow central and western portion of the fault the location of the concentrated slip on the fault plane has important consequences for the amplitude duration and frequency content of the resulting ground motions as documented by takeo and kanamori 1993

holocene forest transformations in sandstone landscapes of the czech republic stand scale comparison of charcoal and pollen records stand scale palaeoecology in sandstone landscapes provides insight into contrasting holocene forest succession trajectories sharp geomorphological gradients in this investigated area which in add