structural evolution of the sarandi del yi shear zone uruguay kinematics deformation conditions and tectonic significance the sarandi del yi shear zone is a crustal scale shear zone that separates the piedra alta terrane from the nico perez terrane and the dom feliciano belt in southern uruguay it represents the eastern margin of the rio de la plata craton and consequently one of the main structural features of the precambrian basement of western gondwana this shear zone first underwent dextral shearing under upper to middle amphibolite facies conditions giving rise to the reactivation of pre existing crustal fabrics in the easternmost piedra alta terrane afterwards pure shear dominated sinistral shearing with contemporaneous magmatism took place under lower amphibolite to upper greenschist facies conditions the mylonites resulting from this event were then locally reactivated by a cataclastic deformation this evolution points to strain localization under progressively retrograde conditions with time indicating that the sarandi del yi shear zone represents an example of a thinning shear zone related to the collisional to post collisional evolution of the dom feliciano belt that occurred between the meso to neoproterozoic 600 ma and late ediacaran lower cambrian times

hafted armatures and multi component tool design at the micoquian site of inden altdorf germany abstract excavation of the micoquian site inden altdorf weisweiler 124 near the former german capital bonn in western germany has revealed the first valid open site habitation features with hut like structures and associated hearths for the middle palaeolithic in central europe it has been dated to the eemian interglacial ois 5e a warm interglacial between 128 and 115 ka bp various wear traces and especially organic residues have been detected on a large number of stone tools using microscopic use wear analysis of lithics recovered from the site a multi level analysis developed through an experimental framework and archaeological study using optical light microscopes scanning electron microscopes and energy dispersive x ray microprobes identified the adhering residues as birch pitch birch pitch is the oldest synthetically produced material and was used as an adhesive to attach lithic implements to wooden shafts while such hafting technology is commonly associated with modern humans in the upper palaeolithic the birch pitch residues found on the micoquian tools of inden altdorf suggest that hafting technologies and the frequent use of multi component tools already existed in the middle palaeolithic c 120 ka bp in central europe

climate instability during the last interglacial period recorded in the grip ice core isotope and chemical analyses of the grip ice core from summit central greenland reveal that climate in greenland during the last interglacial period was characterized by a series of severe cold periods which began extremely rapidly and lasted from decades to centuries as the last interglacial seems to have been slightly warmer than the present one its unstable climate raises questions about the effects of future global warming

bitumen as a hafting material on middle palaeolithic artefacts a scraper and a levallois flake discovered in the mousterian levels dated around 40 000 bc of the umm el tlel site in syria were submitted to an organic geochemieal study to identify a black substance occurring on their surface the shape of this black substance suggests that the organic traces are remnants of a hafting material used by middle palaeolithic people to glue handles onto their tools gas chromatography mass spectro metry gc ms analyses of both c15 alkanes and c15 aromatics confirm that the black substance is a highly weathered bitumen the source of which remains unknown according to some diagnostic molecular information for example the occurrence of fluoranthene and pyrene it seems that the raw bitumen used has been subjected to extreme temperature the scraper and the levallois flake described here are to the best of our knowledge the first reported examples of middle palaeolithic artefacts hutted with bitumen to handles

understanding the storage conditions and fluctuating eruption style of a young monogenetic volcano blue lake crater 3 ka high cascades oregon abstract blue lake crater 13 m s this study illustrates the pre eruptive and eruptive complexities of monogenetic volcanoes and highlights the minimal warning that may precede future eruptions

the neoproterozoic glacial record in the rio de la plata craton a critical reappraisal neoproterozoic glacial successions have been described in south america but the glacial deposits of the rio de la plata craton have been neglected in previous studies addressing the global distribution of glacially influenced successions the rio de la plata craton contains neoproterozoic glacial deposits in the sierra del volcan formation tandilia system argentina glacial influenced deposits in the playa hermosa and zanja del tigre formations dom feliciano belt uruguay and suspected glacially influenced deposits in passo da areia sao gabriel block brazil the tandilia system glacial record includesdiamictites dropstonesand rhythmitesdepos ited in glaciomarine conditions in a tectonically stable depositional setting the dom feliciano belt includes a thin section with ice rafted clasts in carbonates and a thicker section containing diamictites rhythmites outsized clasts and deformed beds in a volcano sedimentary succession the sao gabriel block occurrence deserves more attention to confirm any glacial influence in the fine grained part of the succession glaciation is considered to be contemporaneous with the gaskiers glaciation 580 ma with the exception of the carbonates with dropstones that may represent a previous event correlative with one of the glaciations described in the kalahari craton prior to kalahari rio de la plata assembly in the proto western gondwana margin

phanerozoic low temperature evolution of the uruguayan shield along the south american passive margin the crystalline basement of uruguay was assembled during the brasiliano orogeny in the neoproterozoic era and was later affected by discrete tectonic activity a new multi method low temperature dataset including u th he ages from both zircon and apatite t t modelling and k ar dating of fine sericite fractions and fault gouge reveal a detailed post orogenic geological history spanning the phanerozoic eon the juxtaposition of the terranes that compose the area was achieved in the ediacaran period and post collision was marked by intense exhumation in which the crystalline basement reached near surface conditions by the early to mid palaeozoic regional subsidence promoted sedimentation in the parana basin until the permian covering and reheating much of the basement that is at present exposed afterwards deposition and volcanism were mostly confined to its current limits regional exhumation of the shield during the permo triassic exposed much of the northern portion of the basement and the south was further affected by the opening of the south atlantic ocean during the mesozoic little exhumation affected the uruguayan shield during the cenozoic as reflected in its modest topography the reactivation of inherited neoproterozoic structures influenced the development of mesozoic basins and the present day landscape supplementary material supplementary data sample locations u th he data and k ar data are available at https doi org 10 6084 m9 figshare c 3702043

tectonic setting of the late proterozoic lavalleja group dom feliciano belt uruguay abstract the lavalleja group exposed along the dom feliciano orogenic belt is located in the southeast of uruguay this group consists of volcano sedimentary rocks developed during the neoproterozoic brasiliano cycle the geochemical signature of the igneous rocks of the lavalleja group mainly metagabbros and basic and acidic metavolcanic rocks indicates a back arc basin tectonic setting the metamorphic grade increases to the southeast from very low grade lower green schist facies in the minas formation to a medium grade amphibolite facies in fuente del puma and zanja del tigre formations the metamorphic mineral assemblages correspond to a low pressure regional metamorphism associated with a high thermal gradient a compressive deformational event that probably corresponds to the closure of the lavalleja basin during a continental collision was recognized the petrology geochemistry metamorphic grade and tectonic setting are consistent with a back arc basin setting for the lavalleja group

use of vertical profiles of δ18o to constrain estimates of hydraulic conductivity in a thick unfractured aquitard vertical distributions of 18o were used to constrain hydraulic conductivity k in a thick unfractured aquitard previous investigations utilizing permeability tests at a variety of scales keller et al 1989 indicated that bulk k at the site ranges from 3 5 0 11 m s to 1 2 10 10 m s advective displacements calculated on the basis of these k values lead to a wide range of predicted distributions of natural tracers after 11 000 years comparison of 18o distributions and simulated advection diffusion profiles provide a more precise constraint on advective displacement and hence on k the simulations cast in terms of a peclet number p v2t d ranging in value from 0 to 12 indicate that transport is diffusion controlled and that k is actually less than 1 2 10 11 m s p greater than 0 1 k 1 2 10 11 m s overestimates transport this result indicates that conventional permeability tests in very tight media tend to overestimate k in practical terms advective transport at the site is negligible and transport can be simulated with diffusion only p o

melt inclusion evidence for mantle heterogeneity and magma degassing in the deccan large igneous province india abstract silicate melt inclusions mi trapped in minerals provide direct tools to evaluate source characteristics and magma evolution including magma chamber processes here we present results from the study of mis in basalts from the western ghats region of the deccan large igneous province lip in india the mis in plagioclase and clinopyroxene phenocrysts were analyzed the mis exhibit post entrapment modification by in situ crystal fractionation chemical interaction with the host phenocryst plagioclase or clinopyroxene degassing decrepitation and crystallization of daughter minerals during cooling the mis display variable silica sio2 41 68 wt low potassium and high fe ti contents corresponding to differentiation of basaltic to andesitic magma our data indicate h2o content of about 2 wt which is consistent with recent evidence for elevated primary h2o content in the deccan and other lips corresponding to elevated h2o in the lithospheric mantle and plumes passing through the mid mantle inheriting the hydrous nature

results of a functional study on the middle to early upper pleistocene lithic assemblages from the azokh 1 cave site south caucasus abstract the study of the lithic artefacts exploited by early hominins and the manner in which they were used is a key aspect of lithic studies azokh cave in the southern caucasus comprises a complete stratigraphic sequence of five archaeological units units v i and has yielded large middle to early upper pleistocene lithic and faunal assemblages in association with hominin remains the aim of this study was to evaluate the state of preservation of the lithic assemblages recovered from a marginal area at the rear of the cave and to test the feasibility of functionally analysing these artefacts the study focused on a sample of archaeological pieces that at the macroscopic scale exhibit fresh surfaces and unaltered edges these were analysed using various microscopes the results obtained revealed that some archaeological artefacts from different units do preserve diagnostic use wear traces microwear on the archaeological pieces and a comparison of that wear with experimental results enabled us to identify features related to longitudinal actions and the working of soft material and those related to transversal actions and the working of hard material based on this information we interpreted that these artefacts were used for activities related to butchery hideworking and at times woodworking

macro and micro traces of hafting on quartz tools from pleistocene sites in the sierra de capivara in piaui brazil abstract a series of attributes observed on a number of quartz tools from pleistocene deposits in sierra de capivara piaui brazil are described these attributes or traces are mainly notches retouching and fractures on non active parts of the tools which were possibly made in order to haft those implements in some way these morphological alterations and other probable microscopic traces are identified and described as hafting wear and are compared with the traces attributed to the use of the tools in other productive tasks

igneous garnet and amphibole fractionation in the roots of island arcs experimental constraints on andesitic liquids to evaluate the role of garnet and amphibole fractionation at conditions relevant for the crystallization of magmas in the roots of island arcs a series of experiments were performed on a synthetic andesite at conditions ranging from 0 8 to 1 2 gpa 800 1 000 c and variable h2o contents at water undersaturated conditions and fo2 established around qfm garnet has a wide stability field at 1 2 gpa garnet amphibole are the high temperature liquidus phases followed by plagioclase at lower temperature clinopyroxene reaches its maximal stability at h2o contents 9 wt at 950 c and is replaced by amphibole at lower temperature the slopes of the plagioclase in boundaries are moderately negative in text t text x text h 2 text o space at 0 8 gpa garnet is stable at magmatic h2o contents exceeding 8 wt and is replaced by spinel at decreasing dissolved h2o the liquids formed by crystallization evolve through continuous silica increase from andesite to dacite and rhyolite for the 1 2 gpa series but show substantial enrichment in feo mgo for the 0 8 gpa series related to the contrasting roles of garnet and amphibole in fractionating fe mg in derivative liquids our experiments indicate that the stability of igneous garnet increases with increasing dissolved h2o in silicate liquids and is thus likely to affect trace element compositions of h2o rich derivative arc volcanic rocks by fractionation garnet controlled trace element ratios cannot be used as a proxy for slab melting or dehydration melting in the deep arc garnet fractionation either in the deep crust via formation of garnet gabbros or in the upper mantle via formation of garnet pyroxenites remains an important alternative despite the rare occurrence of magmatic garnet in volcanic rocks

a new greenland deep ice core the polar ice sheets are rich sources of information on past atmospheric conditions including paleoclimates a new deep ice core has been drilled in south greenland comparison of the oxygen isotopic profile with that from camp century and with a deep sea foraminifera record indicates that the new core reaches back to about 90 000 years before present in a continuous sequence the details in the wisconsin part of the ice core records seem to be climatically significant and the general trends reveal all of the relevant emiliani stages recorded in deep sea cores the redated camp century record suggests a dramatic termination of the eem sangamon interglacial

the pre eruptive volatile contents of recent basaltic and pantelleritic magmas at pantelleria italy abstract pantelleria island located in the sicily channel rift zone italy is the type locality for the peralkaline rhyolitic rocks called pantellerites in the last 50 ka after the large green tuff caldera forming eruption volcanic activity at pantelleria has consisted of effusive and explosive eruptions mostly vented inside and along the rim of the caldera and producing silicic lava flows lava domes and poorly dispersed pantelleritic pumice fall deposits basaltic cinder cones and lava flows are only present outside the caldera in the nw sector of the island the most recent basaltic cuddie rosse 20 ka and pantelleritic cuddia randazzo and cuddia del gallo 6 ka pyroclastic products were sampled to investigate magmatic volatile contents through the study of melt inclusions the melt inclusions in pyroxene and olivine phenocrysts of cuddie rosse scoriae have an alkali basalt composition the dissolved volatiles comprise 0 9 1 6 wt h2o several hundred ppm of co2 1600 2000 ppm of sulphur and 500 900 ppm of chlorine the water carbon dioxide couple gives a confining pressure 2 kbar prior to the eruption this result indicates that episodes of magma ponding and crystallization occurred in the upper crust prior to eruption the melt inclusions in feldspar fayalite and aenigmatite phenocrysts of cuddia del gallo and cuddia randazzo pumice have a pantelleritic composition agpaitic indices 1 3 2 1 up to 4 4 wt h2o 8700 ppm cl 6000 ppm f and co2 below the detection limit sulphur averaging 420 ppm has been measured in cuddia randazzo melt inclusions these data indicate relatively high volatile contents for these low energy strombolian type eruptions melt inclusions in cuddia del gallo pumice show the most evolved composition agpaitic indices 2 2 1 and the highest volatile content in agreement with fluid saturation conditions in the magma chamber prior to the eruption this implies a confining pressure of 1 kbar for the top of the pantelleritic reservoir the composition of melt inclusions and mineralogical assemblage of cuddia randazzo pumice indicate that it has a lower evolutionary degree agpaitic indices 1 3 1 8 and lower pre eruptive cl and h2o contents than cuddia del gallo pumice an increase in pressure due to the exsolution of volatiles in the upper part of the pantelleritic reservoir may have triggered the cuddia del gallo explosive eruption evidence of widespread pre eruptive mingling between trachytes and pantellerites suggests that the intrusion of trachytic magma into the pantelleritic reservoir likely played a major role in destabilizing the magma system just prior to the cuddia randazzo event

variability and complexity in calcite based plaster production a case study from a pre pottery neolithic b infant burial at tel roʻim west and its implications to mortuary practices in the southern levant abstract the production of lime plaster is considered as one of the hallmarks of the pre pottery neolithic b ppnb period in the southern levant where lime plaster has been used not only in architectural but also in mortuary contexts in this study we investigate the technology used to produce plaster associated with an infant burial found in the ppnb layers at the site of tel ro im west trw bulk sediment samples and undisturbed impregnated sediment block samples were studied using fourier transform infrared ftir spectroscopy micromorphology and micro ftir in addition we report the results of experimental heating of chalk and marl used as geological reference materials the results indicate that plaster associated with the burial appears in various compositions and that none of them is based on pyrogenic production of lime rather these plaster materials are composed of calcite based crushed ground local marl and or chalk that were mixed with anthropogenic remains including fired clay aggregates burnt carbonised chalk fragments bones and vegetal matter the latter clearly used as temper the case study from trw provides new insights regarding the production of non pyrogenic calcite based plasters in mortuary contexts during the ppnb this study calls for a re consideration of archaeological plaster technology while in the field it is often assumed that ppnb plaster is a product of pyrotechnology our results suggest that in certain cases archaeologists should consider other non pyrogenic technologies of plaster production we argue for a more widespread use of non pyrogenic calcite based plaster than previously suggested not only in architectural but also in mortuary contexts we discuss the social ecological and technological roles plaster production played in ppnb societies in the southern levant

sea level and climate changes during ois 5e in the western mediterranean palaeontological geomorphological and sedimentological data supported by isotopic dating on oxygen isotopic stage ois 5e deposits from the spanish mediterranean coast are interpreted with the aim of reconstructing climatic instability in the northern hemisphere data point to marked climatic instability during the last interglacial ois 5e with a change in meteorological conditions and consequently in the sedimentary environment the oolitic facies generated during the first part of ois 5e ca 135 kyr shift into reddish conglomeratic facies during the second part ca 117 kyr sea surface temperature sst and salinity are interpreted mainly on the basis of warm senegalese fauna which show chronological and spatial differential distribution throughout the western mediterranean present hydrological and meteorological conditions are used also as modern analogues to reconstruct climatic variability throughout the last interglacial and this variability is interpreted within the wider framework of the north atlantic record all the available data indicate an increase in storminess induced by an increase in the influence of northwesterlies a slight drop of sst in the northern western mediterranean and an important change in meteorological conditions at the end of ois 5e 117 kyr these changes correlate well with the decrease in summer insolation and with the climatic instability recorded in north atlantic high latitudes

a new palaeolithic discovery tar hafted stone tools in a european mid pleistocene bone bearing bed two stone flakes partly covered in birch bark tar and a third without tar on it were discovered in fluvial gravel and clay in central italy in association with the bones of a young adult female elephas palaeoloxondon antiquus and several micromammals the probable chronology of the stone flakes is compatible with the late middle pleistocene suggested by the site s small mammals and geological context the fauna indicates a cool stadial episode before isotope stage 6 that age means the flakes are the oldest ever found hafted with tar and indicate a greater capacity for late middle pleistocene hominins to utilize raw materials available during cold phases

co2 solubility in primitive martian basalts similar to yamato 980459 the effect of composition on co2 solubility of basalts and the evolution of the martian atmosphere to determine the influence of basalt composition on the co2 solubility in martian lavas we investigated experimentally a synthetic melt based on the martian meteorite yamato 980459 y 980459 an olivine phyric shergottite and a picritic rock 19 wt mgo thought to be a near primary liquid derived from high temperature 1540 c partial melting of the martian mantle experiments were performed in a piston cylinder apparatus at 1 2 gpa and 1600 1650 c co2 contents in quenched glasses were determined using fourier transform infrared spectroscopy ftir and range from 0 45 1 26 wt despite large differences in feo and mgo contents the co2 solubilities in y 980459 are similar to that in a less primitive synthetic martian basalt based on the humphrey rock and to a hawaiian tholeiite the lack of enhanced solubility in fe2 and mg2 rich melts is likely owing to the complex structural role of these cations in silicate melts acting partly as network formers rather than network modifiers the small sensitivity of co2 solubility to compositional variations among martian and tholeiitic basalts means that the experimentally determined solubilities may be applicable to a wide spectrum of martian magmatic products using experimentally determined co2 solubilities of y 980459 and humphrey allows the calibration of the thermodynamic parameters governing dissolution of co2 vapor as carbonate in martian basalts this relation facilitates calculation of the co2 dissolved in magmas derived from graphite saturated martian basalt source regions as a function of p t and f o2 the hot conditions in the source of y 980459 1540 10 c and 1 2 0 5 gpa are plausible for plume related magmas forming the giant tharsis volcanic complex which accounts for 50 of martian igneous activity since stabilization of the primordial crust if oxygen fugacity in the sources of hot tharsis magmatism were equivalent to that at the iron wustite buffer iw or 1 log unit above iw 1 respectively then the entire tharsis event would outgas 30 300 mbars of co2 to the martian atmosphere which is far from the 2 bars required to stabilize an equable climate in the late noachian and early hesperian epochs this mismatch could be reconciled if significant martian igneous activity derived from comparatively oxidized mantle sources i e iw 2 similar to those responsible for the nakhlite meteorites

abrupt increase in greenland snow accumulation at the end of the younger dryas event the warming at the end of the last glaciation was characterized by a series of abrupt returns to glacial climate the best known of which is the younger dryas event1 despite much study of the causes of this event and the mechanisms by which it ended many questions remain unresolved1 oxygen isotope data from greenland ice cores2 4 suggest that the younger dryas ended abruptly over a period of about 50 years dust concentrations2 4 in these cores show an even more rapid transition 20 years this extremely short timescale places severe constraints on the mechanisms underlying the transition but dust concentrations can reflect subtle changes in atmospheric circulation which need not be associated with a large change in climate here we present results from a new greenland ice core gisp2 showing that snow accumulation doubled rapidly from the younger dryas event to the subsequent preboreal interval possibly in one to three years we also find that the accumulation rate change from the oldest dryas to the bo11ing allerod warm period was large and abrupt the extreme rapidity of these changes in a variable that directly represents regional climate implies that the events at the end of the last glaciation may have been responses to some kind of threshold or trigger in the north atlantic climate system

the flickering switch of late pleistocene climate change polar ice contains a unique record of past climate variations previous greenland ice cores have documented relatively warm interstadial periods during the last glaciation and short centuryscale returns to colder conditions during the glacial to interglacial warming see for example ref 1 these climate features have also been observed to varying degrees in ocean sediment cores2 4 and terrestrial pollen and insect records5 7 here we report electrical conductivity measurements from a new greenland ice core which confirm these previous observations and also reveal a hitherto unrecognized mode of rapid climate variation fluctuations in ice conductivity on the scales of 5 20 years reflect rapid oscillations in the dust content of the atmosphere this flickering between two preferred states would seem to require extremely rapid reorganizations in atmospheric circulation

southernmost exposures of the arroyo del soldado group vendian to cambrian uruguay palaeogeographic implications for the amalgamation of w gondwana abstract the occurrence of the vendian to lowermost cambrian arroyo del soldado group asg is reported from an area located to the sw of minas which was formerly mapped as part of the lavalleja group the yerbal polanco and cerro espuelitas formations of the asg occur there as a rather continuous microfossil rich sedimentary cover intruded by granites of probable cambrian age minas granite organic walled microfossils recovered from the yerbal and polanco formations include bavlinella faveolata leiosphaeridia tenuissima soldadophycus bossii soldadophycus major siphonophycus solidum glenobotrydion aenigmatis and filament mats the acritarch dyctiotidium sp is described for the first time from the yerbal formation essentially the same microfossil assemblage occurs in five samples of this unit collected immediately to the north of minas no identifiable microfossils were found in fifteen samples of organic rich lithologies of the lavalleja group based on detailed geological mapping litho and biostratigraphic data we show that the contact between the arroyo del soldado and lavalleja groups is of tectonic nature arroyo la plata lineament the latter being pre vendian in age the villa serrana block is defined and consists of the carape and lavalleja groups las ventanas and playa hermosa formations an unnamed siliciclastic ultrabasic succession showing low grade metamorphism and various granitic intrusions mostly of neoproterozoic to cambrian age its boundaries are the sarandi del yi piriapolis shear zone to the w the sierra ballena shear zone to the e the arroyo la plata lineament to the n and the rio de la plata to the s the villa serrana block could be an allochthonous terrane or alternatively a part of the nico perez terrane that was thrusted onto the asg no continuity exists between the brusque and porongos groups of southern brazil and the lavalleja group according to available data these units are probably not coeval and do not represent the suture between the cratonic areas to the w rio de la plata craton and the remnants of a neoproterozoic magmatic arc to the e cuchilla dionisio pelotas terrane accretion of these blocks was controlled by sinistral continental scale megashears the geology of the area is far too complex to be explained in terms of a single orogeny following one wilson cycle

a micro reflectance ir spectroscopy method for analyzing volatile species in basaltic andesitic phonolitic and rhyolitic glasses volatile contents of geologic glasses are used to model magma chamber and degassing processes thus there is considerable interest in small scale analytical techniques for analyzing volatiles in glasses infrared ir spectroscopy has the advantage of determining volatile speciation in glasses e g oh molecular h 2 o molecular co 2 and co 3 2 however sample preparation for the most common ir method used micro transmission ir spectroscopy is complicated because glasses must be prepared as thin parallel sided wafers raman analysis while valuable for fe poor samples can be difficult to use for fe rich glasses we have calibrated a micro reflectance infrared method for determining volatile species using calculated kramers kronig absorbance kk abs spectra that requires that only one side of a glass be polished the method is easier to use than other reflectance methods where it is difficult to determine the baseline for the ir bands total h 2 o wt m 3600 cm 1 kk abs where m is the slope of the calibration line that is obtained from a fit to the data the m value is related to the calculated refractive index n for a range of aluminosilicate glass compositions allowing the technique to be applied to samples with unknown calibration slopes for calc alkaline andesite glasses we determined calibration slopes for micro reflectance ir measurements of molecular h 2 o molecular co 2 and co 3 2 the method has been calibrated for glasses with up to 6 76 wt total h 2 o but is useful for glasses with more than 20 wt total h 2 o and has been calibrated for glasses with up to 0 575 wt total co 2 this technique provides a means to analyze volatile abundances in samples that are not possible to analyze or prepare for analysis with transmission micro ir techniques we have determined volatile contents in fragile samples such as cracked vesicular or crystal bearing glasses formed by volcanic or impact processes or in high pressure bubble nucleation experiments and h diffusion experiments we have monitored h uptake during weathering of basaltic glasses that cannot be polished and determined volatiles in melt inclusions and pumice

a salt oscillator in the glacial atlantic 1 the concept as shown by the work of dansgaard and his colleagues climate oscillations of one or so millennia duration punctuate much of glacial section of the greenland ice cores these oscillations are characterized by 5 c air temperature changes severalfold dust content changes and 50 ppm co2 changes both the temperature and co2 change are best explained by changes in the mode of operation of the ocean in this paper we provide evidence which suggests that oscillations in surface water conditions of similar duration are present in the record from a deep sea core at 50 n based on this finding we suggest that the greenland climate changes are driven by oscillations in the salinity of the atlantic ocean which modulate the strength of the atlantic s conveyor circulation

textures and fabrics in the grip ice core a comprehensive study of textures and fabrics has been carried out on the greenland ice core project grip ice core crystal sizes and c axis orientations have been measured on thin sections with conventional techniques yielding new information on the growth rotation and recrystallization of ice crystals in the greenland ice sheet normal grain growth is found to persist to a depth of 700 m in the core where the onset of polygonization due to increasing strain prevents a further increase in grain size in the holocene ice smaller crystals are observed in the wisconsin ice larger crystals are found in the eemian ice and the crystal size is found to vary with climatic parameters in these periods this dependence which probably results from variable impurity content in the ice persists to a depth of 2930 m coarse grained ice probably resulting from rapid growth of crystals at comparatively high temperatures is found in the lowest 100 m of the core the data on c axis orientations reveal a steady evolution of the fabric from random near the surface to a strong single maximum in the lower part of the ice sheet a significant strengthening is not observed at the holocene wisconsin transition the fabric development indicates that vertical compression at the ice divide is the main mode of deformation down to a depth of 2850 m the evolution toward a single maximum fabric hardens the ice against vertical compression but softens it against simple shear evidence of simple shear deformation is clearly observed between 2850 m and 2950 m depth stretched fabrics in coarse grained ice in the lowest 100 m could be due to tensional stresses this ice is unlikely to be undergoing any significant horizontal deformation at the present time

tracking the sources and the evolution of the late neoproterozoic granitic intrusions in the brusque group dom feliciano belt south brazil la icp ms and shrimp geochronology coupled to hf isotopic analysis abstract the central domain of the neoproterozoic dom feliciano belt in the brazilian state of santa catarina is mainly composed of a metavolcano sedimentary sequence the brusque group and its crystalline basement such as the camboriu complex this association was intruded in its late deformational stage by voluminous granitic magmatism related to the metamorphic climax of the area the intrusions share a distinct crustal affinity and are divided into three suites from oldest to youngest as indicated by field criteria sao joao batista valsungana and nova trento we present seven new la icp ms and two shrimp u pb zircon ages coupled with in situ analysis of hf isotopes and use them to discuss the magmatic sources and evolution of the intrusions and propose an evolutionary model for this plutonic association intrusion mostly took place at 615 585 ma but the field stratigraphy is not necessarily reflected by u pb ages which establish considerable overlaps between intrusions from different suites inherited zircon crystals are common and reflect a long geological history that matches the geochronological record of the brusque group and the camboriu complex hf ratios are remarkably widespread but strengthen the characteristic crustal signature of the magmatism and partially overlap with whole rock isotopic data for the same rocks we propose that the intrusions were caused by a regional heating event within the central domain of the dom feliciano belt in santa catarina with limited direct mantellic contribution and more significant indirect thermal contribution through the voluminous magmatism of the recently juxtaposed florianopolis batholith this triggered large scale partial melting of the local continental crustal and formed the studied granites the long lasting magmatic event promoted the protracted generation and emplacement of numerous distinct intrusions synchronically leading to contrasts between the field and u pb stratigraphy the suites varied geochemical and isotopic characteristics probably reflect a combination of the heterogeneities of their source rocks with the impact of different magmatic processes during granitogenesis and emplacement while the valsungana and nova trento suites were probably generated within a deeper crustal level and underwent some degree of magmatic interaction the peraluminous sao joao batista suite has an upper crust signature that indicates the assimilation of metasedimentary rocks

reconstructing projectile technology during the pre pottery neolithic b in the levant an integrated approach to large tanged points from halula abstract large tanged points made on bidirectional blades constitute the most characteristic tool type during the pre pottery neolithic b in the levant studies on projectile typology and on bidirectional technology have revealed important stylistic differences reflecting chronological and geographical patterning contributing significantly to the understanding of early farming communities in the near east however the reconstruction of the weapons these large tanged points were part of has not received the same attention this investigation aims to fully characterize stone point production at halula a ppnb settlement in the middle euphrates valley and reconstruct the type of weapons and delivery mechanisms used our study also includes the analysis of various ballistic attributes using a series of recent morpho metric methods and comparison with ethnographic and experimental data about projectiles of known use results indicate that byblos points might have been used as dart points propelled with the help of spear throwers indicating a shift from bow to spear thrower in projectile technology associated with the appearance and expansion of bidirectional blade technology during the ppnb in the levant and synchronous with the consolidation of agricultural systems in the region

volatiles in submarine basaltic glasses from the northern kerguelen plateau odp site 1140 implications for source region compositions magmatic processes and plateau subsidence submarine pillow basalts 34 ma recovered from the northern introduction kerguelen plateau at odp site 1140 contain abundant unaltered the kerguelen plateau and broken ridge formed mostly glass providing the first opportunity to measure the volatile contents during the cretaceous as a single giant oceanic plateau of tholeiitic basaltic magmas related to the kerguelen mantle plume that is interpreted to represent voluminous magmatism the glasses have la sm and nb zr ratios that vary from values associated with emplacement of a mantle plume head similar to southeast indian ridge seir morb unit 1 to below young indian ocean lithosphere duncan slightly more enriched unit 6 to values transitional between storey 1992 weis et al 1992 during ocean drilling seir morb and basaltic magmas formed by melting of the program odp leg 183 igneous basement rock and kerguelen plume units 2 and 3 volatile contents for glasses in sediment cores were obtained from five sites on the units 1 and 6 are similar to depleted mid ocean ridge basalt kerguelen plateau and two on broken ridge fig 1 the morb values 0 25 0 27 wt h2o 1240 1450 ppm s results combined with subsequent radiometric dating 42 54 ppm cl in contrast h2o contents are higher for the demonstrate that from south to north the age of the enriched glasses unit 2 0 44 wt h2o unit 3 0 69 wt uppermost crust decreases from 120 110 ma in the as are s 1500 ppm and cl 146 206 ppm cl k ratios southern kerguelen plateau to 110 to 95 ma in the for all glasses are relatively low 0 03 0 04 indicating that central kerguelen plateau broken ridge and elan bank assimilation of hydrothermally altered material did not occur during to 35 ma in the northern kerguelen plateau coffin shallow level crystallization h2o ce for the enriched glasses et al 2000 pringle duncan 2000 duncan 2002 at units 2 and 3 is significantly lower than pacific and south six of seven basement sites as well as at four sites drilled atlantic morb values suggesting that low h2o ce may be an on earlier odp cruises subaerially erupted basalt flows inherent characteristic of the kerguelen plume source vapor saturation were recovered indicating that the growth rate of the pressures calculated using the h2o and co2 contents of the glasses kerguelen large igneous province lip was sufficient to indicate that 1700 m of subsidence has occurred on this part of form a subaerial landmass however a sequence of the plateau since eruption of the basalts at 34 ma subsidence submarine erupted pillow basalt flows of 90 m thickness estimates for site 1140 and other odp drill sites indicate that the was drilled at site 1140 on the northern kerguelen various parts of the kerguelen plateau subsided at a rate comparable plateau coffin et al 2000 with that for normal indian ocean lithosphere the site 1140 submarine glasses provide the first

the deep magmatic system of the campi flegrei caldera italy 1 melt inclusions in phenocrysts of the minopoli2 shoshonite and fondo riccio latite eruptive products campi flegrei caldera 10 2 to 9 5 ka bp constrain the nature of deep phlegraean magmatic fluids their role in volcanism and give new insights into the magmatic plumbing system the analyzed melt inclusions show that co2 is an abundant gaseous species confirming the results of geochemical studies on the magmatic gas fraction involved in present day fumarolic emissions volatile concentrations within the melt inclusions require gas melt equilibria between 8 and 9 km depth and closed system degassing in presence of ascending co2 rich fluids of deep provenance magmas later re equilibrate at depths up to 3 2 km i e above the top of the carbonate basement these observations correlate well with independent geophysical and geochemical evidence and are useful constraints for volcanic hazards assessment at campi flegrei

composite projectiles and hafting technologies at ohalo ii 23 ka israel analyses of impact fractures morphometric characteristics and adhesive remains on microlithic tools abstract this study focuses on the correlation between the production of backed microliths in the levant during the late upper palaeolithic and their use as side elements of composite projectile weapons the investigation is based on assemblage sample of microliths from ohalo ii a 23 000 years old submerged campsite and involves analyses of diagnostic impact fractures location of adhesive remains and morpho metric characteristics of the tools two distinct adhesive materials have been also analyzed and the preliminary results indicate the use of both calcareous and organic substances the use of backed microliths as side elements of composite projectiles has been followed for scalene triangles a microlithic type unknown from the earlier upper palaeolithic in the levant the reconstruction of their use has been established based upon all the three evidence lines i e patterns of impact fractures as well as the location of adhesive remains and the morpho metric characteristics of the microliths the results of the study show an upper palaeolithic epipalaeolithic continuity in the approach to the design of hunting weapons and hafting technologies it is also suggested that the origins of composite projectiles in the levant may be found in the earlier phases of the upper palaeolithic

chemostratigraphy of mesoproterozoic and neoproterozoic carbonates of the nico perez terrane rio de la plata craton uruguay abstract increasing evidence shows that mesoproterozoic rocks are widespread in the rio de la plata craton carbon and strontium isotope analyses were carried out for three different carbonate bearing successions in the southern nico perez terrane the parque ute group is erected comprising from base to top the mainly volcanogenic canada espinillo formation the dolomitic mina valencia formation and the mixed carbonate siliciclastic cerro del mastil formation a 13 c curve was obtained for carbonates of the parque ute group which is characterized by a plateau at 1 to 1 6 v pdb bracketed between two negative excursions 1 8 v pdb at the base and 3 3 v pdb at the top these values are consistent with a mesoproterozoic depositional age for the unit as indicated by u pb ages of synsedimentary volcanics and gabbros of 1429 21 and 1492 4 ma respectively the mataojo formation and the marcos de los reyes formation were previously thought to be of similar age the chemostratigraphic data however show that there is a hiatus of at least 700 myr between these units and that neither is correlative of the parque ute group dolomitic marbles of the mataojo formation yielded a 13 c curve that varies within a narrow range around 0 v pdb 0 6 to 0 4 this along with the youngest u pb detrital zircon ages of 1802 ma constrains deposition between 1 8 and 1 5 ga late palaeoproterozoic early mesoproterozoic in contrast with the latter unit the marco de los reyes formation yielded 13 c values defining moderate to high amplitude 13 c excursions between 4 4 v pdb and 3 2 v pdb corresponding 87 sr 86 sr values range between 0 7070 and 0 7080 both c and sr chemostratigraphy point to a later neoproterozoic possibly ediacaran age for the marco de los reyes formation it is here proposed that modest 13 c seawater enrichment and low amplitude 13 c excursions following a long period of isotopic invariance around 0 v pdb began already around 1 50 1 45 ga thereafter the amplitude of 13 c excursions increased gradually until the late neoproterozoic one important conclusion emerging from the data presented in this paper is that mesoproterozoic rocks are common in the rio de la plata craton and probably fringe it at both its western and eastern side this suggests a rather central position of the craton within rodinia as also suggested by other lines of evidence such as detrital zircon ages and a widespread thermal overprint at 1 25 ga

growth history of kilauea inferred from volatile concentrations in submarine collected basalts abstract major element and volatile h2o co2 s compositions of glasses from the submarine flanks of kilauea volcano record its growth from pre shield into tholeiite shield stage pillow lavas of mildly alkalic basalt at 2600 1900 mbsl on the upper slope of the south flank are an intermediate link between deeper alkalic volcaniclastics and the modern tholeiite shield lava clast glasses from the west flank of papau seamount are subaerial mauna loa like tholeiite and mark the contact between the two volcanoes h2o and co2 in sandstone and breccia glasses from the hilina bench and in alkalic to tholeiitic pillow glasses above and to the east were measured by ftir volatile saturation pressures equal sampling depths 10 mpa 1000 m water for south flank and puna ridge pillow lavas suggesting recovery near eruption depths and or vapor re equilibration during down slope flow south flank glasses are divisible into low pressure co2 0 5 wt s 1000 1700 ppm and high pressure groups co2 40 ppm s 1000 ppm corresponding to eruption sea level at moderate water depths 300 1000 m or shallower but in disequilibrium and in deep water 1000 m saturation pressures range widely in early alkalic to strongly alkalic breccia clast and sandstone glasses establishing that early k lauea s vents spanned much of mauna loa s submarine flank with some vents exceeding sea level later south flank alkalic pillow lavas expose a sizeable submarine edifice that grew concurrent with nearby subaerial alkalic eruptions the onset of the tholeiitic shield stage is marked by extension of eruptions eastward and into deeper water to 5500 m during growth of the puna ridge subaerial and shallow water eruptions from earliest kilauea show that it is underlain shallowly by mauna loa implying that mauna loa is larger and kilauea smaller than previously recognized

uranium series dating of fen peat horizons from pit nachtigall in northern germany abstract peat and other terrestrial sediments are important archives of climate forcing this study discusses the numerical age determination of stratigraphically important quaternary sequences from clay pit nachtigall near holzminden in northern germany which have been the subject of debate concerning their chronological classification since they were first described by grupe in 1929 uranium series dating 230 th u of different organic horizons as well as sedimentology including loss on ignition loi and palynology was carried out to set up a more reliable chronological framework for the weser river area 230 th u ages were calculated using an isochron approach with the leachate leachate method for chemical preparation open system requirements and specification of sample selection criteria for organic samples are investigated by determination of uranium and thorium composition of the rim layers different organic sediments are investigated the organic deposits from nachtigall show middle pleistocene 230 th u ages ranging from 227 9 8 ka to 201 15 13 ka and appear to represent a warm temperate phase preceding the eemian interglacial mis 5e and the drenthe stadial mis 6 indicating a correlation with marine isotope substage mis 7c these results are in good agreement with the investigation of the pollen spectra indicating a correlation with a warm stage within the lower saalian complex

technological and behavioural complexity in expedient industries the importance of use wear analysis for understanding flake assemblages abstract expedient lithic technology has been described as unchanging and without or very limited presence of formal tool types however this premise seems to limit the discussion on technological and behavioural complexity when studying amorphous flake industries to address this issue we employed multi stage use wear analysis to identify features that are not detectable through macroscopic approach our analysis of chert tools from leang sarru north sulawesi indicated the use of both unmodified flakes and retouched tools for plant processing and we detected evidence for the manufacture of composite tools microscopic wear traces on unretouched flakes show that these were attached to shafts for possible use as hafted tools but not necessarily as projectiles our results suggest that simple flake assemblages can be part of complex tool production and present an alternative view on the seemingly unchanging lithic technology from the late pleistocene to the holocene furthermore our current understanding of expedient lithic technology should be reassessed as features that are not observable with standard morphological and technological analyses may be detected through use wear analysis overall the applied methodology and results of this study are relevant to pleistocene and early holocene archaeological sites and assemblages that exhibit the dilemma of inferring technological and behavioural complexity through the analysis of simple stone tools

the abrupt termination of the younger dryas climate event previous studies on two deep greenland ice cores have shown that a long series of climate oscillations characterized the late weichselian glaciation in the north atlantic region1 and that the last glacial cold period the younger dryas ended abruptly 10 700 years ago2 here we further focus on this epoch defining event and present detailed heavy isotope and dust concentration profiles which suggest that in less than 20 years the climate in the north atlantic region turned into a milder and less stormy regime as a consequence of a rapid retreat of the sea ice cover a warming of 7 c in south greenland was completed in about 50 years

a late eemian aridity pulse in central europe during the last glacial inception how do ice ages begin it s an obvious question to ask as we enjoy the relative luxury of an interglacial but a hard one to answer a look at past transitions may give some clues as to how this period will one day come to an end a climate reconstruction based on sediments found beneath a lake in the eifel mountains in germany provides evidence of an extreme climate event lasting 468 years right at the end of the last interglacial dust storms aridity bushfires and the loss of trees associated with a warm climate coincided with a southward shift of the warm waters of the north atlantic drift in terms of insolation the rate of delivery of the sun s radiation to earth conditions then were similar to those we have now investigating the processes that led to the end of the last interglacial period is relevant for understanding how our ongoing interglacial will end which has been a matter of much debate see for example refs 1 2 a recent ice core from greenland demonstrates climate cooling from 122 000 years ago3 driven by orbitally controlled insolation with glacial inception at 118 000 years ago4 5 6 7 8 here we present an annually resolved layer counted record of varve thickness quartz grain size and pollen assemblages from a maar lake in the eifel germany which documents a late eemian aridity pulse lasting 468 years with dust storms aridity bushfire and a decline of thermophilous trees at the time of glacial inception we interpret the decrease in both precipitation and temperature as an indication of a close link of this extreme climate event to a sudden southward shift of the position of the north atlantic drift the ocean current that brings warm surface waters to the northern european region the late eemian aridity pulse occurred at a 65 n july insolation of 416 w m 2 close to today s value of 428 w m 2 ref 9 and may therefore be relevant for the interpretation of present day climate variability

experimental constraints on the deep magma feeding system at stromboli volcano italy new experiments have been performed on a high k basalt pst 9 from stromboli volcano italy to constrain the physical conditions of golden pumice magmas at their storage level and discuss their petrogenesis fluid present h2o and co2 bearing near liquidus experiments were performed at 11508c between 100 and 400mpa and under oxidizing conditions glasses were analyzed by fourier transform ir spectroscopy and their h2o and co2 concentrations compared with those in glass inclusions most glass inclusions cluster near the 200mpa isobar suggesting entrapment at a depth of 8 km golden pumice magmas have viscosities of 7 9 pa s and densities of 2 48 2 57 g cm3 compositions of experimental fluids coexisting with melts along the liquidus have been estimated by mass balance they range from co2 rich xh2o 0 2 at 400mpa to h2o rich xh2o 0 8 at 100mpa the free fluid phase present at the reservoir level has an xh2o of 0 6 consistent with equilibration with a near liquidus golden pumice magma below 300mpa clinopyroxene is the liquidus phase in all highpressure experiments either fluid absent h2o or fluid present h2o co2 in contrast at 0 1mpa cpx and ol appear together on the liquidus and olivines are more fo rich up to 89 1 than those crystallizing at high pressures up to 87 3 the composition of cotectic liquids multiply saturated in cpx and ol has been experimentally determined most pumices and a majority of melt inclusions have compositions of cotectic melts in contrast pst 9 plots in the cpx field and is representative of less evolved ankaramitic magmas parental to golden pumices melt inclusions trapped in fo 487 olivines form a group of ultra calcic compositions plotting in the cpx field interpreted as boundary layer melts locally generated by cpx dissolution in the deep reservoir ankaramitic melts in the stromboli feeding system are proposed to derive from primitive mantle melts by combined crystallization mixing wall rock interaction and assimilation

2001 flank eruption of the alkali and volatile rich primitive basalt responsible for mount etna s evolution in the last three decades abstract since the early 1970s enhanced eruptive activity of mount etna has been accompanied by selective geochemical changes in erupted lavas among which a gradual increase of alkalis whose origin is still debated here we provide further insight into the origin of this recent evolution based on a detailed study of the chemistry and dissolved volatile content of melt inclusions trapped in olivine crystals of unusual plagioclase poor primitive basalt that was extruded during a highly explosive flank eruption in july august 2001 two types of lava were erupted simultaneously along a n s fracture system trachybasalts from the upper vents 2950 2700 m were simply drained out by fracturing of the central volcanic conduit they are identical to summit crater lavas and contain mg poor olivines fo 70 72 with evolved and volatile poor melt inclusions that represent late stage crystallisation during shallow open conduit degassing in contrast plagioclase poor basalt 80 of total extruded through the lower vents 2550 2100 m derived from lateral dyke intrusion of a more primitive and volatile rich magma across the sedimentary basement this primitive melt is best preserved in rare fo 82 4 80 5 skeletal olivines present in lapilli deposits from the most powerful activities at the 2550 m vent its high dissolved contents of h 2 o 3 4 wt co 2 0 11 to 0 41 wt s 0 32 wt cl 0 16 wt and f 0 094 wt point to its closed system ascent from 400 to 250 mpa 12 to 6 5 km depth b s l however the predominance of euhedral olivine phenocrysts with common reverse zoning cores fo 76 78 and rims fo 78 80 and decrepited inclusions shows that most of the erupted basalt derived from a slightly more evolved crystallizing body of the same magma that was invaded by the uprising primitive melt prior to erupting the few preserved inclusions in these olivines indicate pre eruptive storage of that magma body at about 5 km depth b s l in coherence with seismic data we propose that the 2001 flank eruption resulted from gradual overpressuring of etna s shallow plumbing system due to the influx of volatile rich primitive basalt that may have begun several months in advance we find that this basalt is much richer in alkalis 2 0 wt k 2 o and has higher s cl 2 0 but lower cl k and cl f ratios than all pre 1970s etnean lavas 1 4 wt k 2 o s cl 1 5 as further exemplified by melt inclusions in entrained olivine xenocrysts combining these new observations with previously published data we argue that the 2001 basalt represents a new alkali rich basic end member feeding mt etna only few amount of which had previously been extruded during a 1974 peripheral eruption and more recently during brief paroxysmal summit events over the last three decades this new magma has progressively mixed with and replaced the former k poorer trachybasalts filling the plumbing system leading to extrusion of gradually more primitive and alkali richer lavas its geochemical singularities cannot result from shallow crustal contaminations instead they suggest the involvement of an alkali richer but cl poorer arc type component during recent magma genesis beneath etna

role of the thermohaline circulation in the abrupt warming after heinrich events evidence of rapid climate oscillations during the last glacial period has been identified in climate records from greenland ice cores1 2 and ocean sediments in the north atlantic3 4 these records show that periods of gradual cooling are terminated by abrupt warming events5 with the coldest periods coinciding with the deposition of ice rafted debris so called heinrich events throughout the north atlantic heinrich events are thought to be a signature of massive iceberg discharges owing to collapse of the laurentide ice sheet bond et al 5 have proposed that the decrease in meltwater flux following collapse and retreat of the ice sheet enhanced the ocean s thermohaline circulation6 thereby increasing advection of heat from the tropics and giving rise to abrupt climate warming here we test this idea using a simple ocean model coupled to a model of a periodically surging ice sheet we find that massive discharges of icebergs first stop the thermohaline circulation because of the consequent freshwater influx cooling the north atlantic region this is followed by a rapid restart of the circulation leading to abrupt warming thus our model can reproduce the qualitative features of the climate oscillations seen in the ice core and ocean records

stable climatic conditions in central germany during the last interglacial stable isotopic data from the high resolution limnic sequence in the opencast mine at grobern central germany confirm the relatively stable climate of the last interglacial deduced from pollen analyses after significant warming during the transition from the saalian to the eemian stable warm climatic conditions set in once the climatic optimum was reached in the course of biozones e4 to e5 from the middle of biozone e6b a gradual temperature decrease can be observed reaching a minimum at the start of biozone e7 the division of the early weichselian glacial in central germany into two stadials herning rederstall and two interstadials brorup odderade is also documented by the findings copyright 2000 john wiley sons ltd

the δ18o of atmospheric o2 from air inclusions in the vostok ice core timing of co2 and ice volume changes during the penultimate deglaciation one important question about the co2 climate connection is how increasing atmospheric pco2 levels affect climate and thereby the mass balance of continental ice sheets a record of atmospheric co2 variations over the last 160 000 years has recently been constructed by analyzing the trapped gas in the vostok ice core barnola et al 1987 the relationship between changes in atmospheric co2 and the size of the continental ice sheets has been difficult to ascertain because the co2 record is obtained from ice cores while the ice volume record has been constructed from the stable isotopic composition of biogenic caco3 in deep sea sediment cores in order to compare these two records in a more precise manner we present a record of the isotopic composition 18o of atmospheric o2 trapped in the vostok ice core and propose that it may be considered a proxy for the 18o of seawater and hence ice volume having a record of atmospheric co2 along with a continental ice volume proxy in trapped air in the same ice core allows us to compare the timing of changes in these two parameters with little uncertainty in the relative ages of important events our results suggest that during the penultimate glacial termination atmospheric co2 began to increase at least 3 kyr before the initial introduction of meltwater to the oceans possible errors in the relative age depth curve of the vostok ice core and uncertainties in the influence of biological and hydrologic processes on the 18o of atmospheric o2 introduce some uncertainty into our conclusions however our results are in general agreement with the observed phase relationship between atmospheric co2 and ice volume imbrie et al 1984 imbrie et al 1989 inferred from changes in the 13c difference between contemporaneous planktonic and benthic forams deposited in deep sea cores and the specmap ice volume record

millennial variability in an idealized ocean model predicting the amoc regime shifts abstracta salient feature of paleorecords of the last glacial interval in the north atlantic is pronounced millennial variability commonly known as dansgaard oeschger events it is believed that these events are related to variations in the atlantic meridional overturning circulation and heat transport here the authors formulate a new low order model based on the howard malkus loop representation of ocean circulation capable of reproducing millennial variability and its chaotic dynamics realistically it is shown that even in this chaotic model changes in the state of the meridional overturning circulation are predictable accordingly the authors define two predictive indices which give accurate predictions for the time the circulation should remain in the on phase and then stay in the subsequent off phase these indices depend mainly on ocean stratification and describe the linear growth of small perturbations in the system thus monitoring particular indices of the ocean state could help predict

west gondwana amalgamation based on detrital zircon ages from neoproterozoic ribeira and dom feliciano belts of south america and comparison with coeval sequences from sw africa

timing of deformation in the sarandi del yi shear zone uruguay implications for the amalgamation of western gondwana during the neoproterozoic brasiliano pan african orogeny u pb and hf zircon sensitive high resolution ion microprobe shrimp and laser ablation inductively coupled plasma mass spectrometry la icp ms ar ar hornblende and muscovite and rb sr whole rock muscovite isochron data from the mylonites of the sarandi del yi shear zone uruguay were obtained in order to assess the tectonothermal evolution of this crustal scale structure integration of these results with available kinematic structural and microstructural data of the shear zone as well as with geochronological data from the adjacent blocks allowed to constrain the onset of deformation along the shear zone at 630 625 ma during the collision of the nico perez terrane and the rio de la plata craton the shear zone underwent dextral shearing up to 596 ma under upper to middle amphibolite facies conditions which was succeeded by sinistral shearing under lower amphibolite to upper greenschist facies conditions until at least 584 ma after emplacement of the cerro caperuza granite at 570 ma the shear zone underwent only cataclastic deformation between the late ediacaran and the cambrian the sarandi del yi shear zone is thus related to the syncollisional to postcollisional evolution of the amalgamation of the rio de la plata craton and the nico perez terrane furthermore the obtained data reveal that strain partitioning and localization with time magmatism emplacement and fluid circulation are key processes affecting the isotopic systems in mylonitic belts revealing the complexity in assessing the age of deformation of long lived shear zones

timing and duration of the last interglacial evidence for a restricted interval of widespread coral reef growth abstract we report new mass spectrometric u series ages for eight last interglacial fossil reefs along the continental margin of western australia corals were selected in growth position from localities that are characterized by apparently low levels of diagenesis and relative tectonic stability so that the fossil reefs provide critical information on last interglacial sea levels without requiring corrections for tectonic movements in addition we have improved the constraint on the timing of onset of reef growth by recovering drill core coral from the base of the reefs uranium and thorium isotopes were measured with high levels of precision leading to improvements in age resolution and allowing samples which have undergone diagenetic exchange of uranium and thorium to be more easily identified and discarded these data supplement our previous results for rottnest island and leander point leading to more than seventy mass spectrometric u series ages from which constraints can be placed on the timing duration and character of the last interglacial sea level highstand reliable ages show that reef growth started contemporaneously at 128 1 ka along the entire western australian coastline while relative sea levels were at least 3 m above the present level because western australia is located far from the former penultimate glacial maximum ice sheets and are not significantly effected by glacial unloading these data constrain the timing of onset of the last interglacial period to 128 1 ka assuming reef growth started soon after sea level approached interglacial levels a unique regressive reef sequence at mangrove bay constrains the timing of termination of the last interglacial period to 116 1 ka the major episode of reef building however both globally and locally along the western australian coast is restricted to a very narrow interval occurring from 128 ka and 121 ka suggesting that global ocean surface temperatures were warm and or sea levels were stable enough to allow prolific reef growth only during the earlier part of the last interglacial

comment on provenance of the arroyo del soldado group ediacaran to cambrian uruguay implications for the palaeogeographic evolution of southwestern gondwana by blanco et al precambrian res 171 2009 57 73 thus it is truly tectonics which governs stratigraphy and thetwobranchesofthegeologicalsciencesareinseparable astruc tural geologists who is not a stratigrapher is only a geometer not a geologist for he reasons about abstract surfaces and vol umes emptied of their history and a stratigrapher who neverconcerned himself with tectonics would produce only a deadstratigraphy gignoux 1950 p 3 the paper provenance of the arroyo del soldado group ediacaran to cambrian uruguay implications for the palaeogeo graphicevolutionofsouthwesterngondwana blancoetal 2009 presented new u pb shrimp sm nd and geochemical data ofsome units of arroyo del soldado group asg in order to betterconstraining the evolution of sedimentary protoliths and there fore to justify a rift tectonic setting for deposition of those units unfortunately the data presented are incapable of answering thetectonic evolution of neoproterozoic lower paleozoic brasilianounits located at the east of the uruguayan territory we point outthattheauthors interpretationisnotsubstantiatedonthedata thescarcity of geological and isotopic data obtained for dom felicianobelt dfb determinesawidespanofgeotectonicmodels blancoetal 2009 use force andadapttheavailableisotopicdatatosustaintheir tectonic model other plausible models can also explain the

irregular glacial interstadials recorded in a new greenland ice core the greenland ice sheet offers the most favourable conditions in the northern hemisphere for obtaining high resolution continuous time series of climate related parameters profiles of 18o 16o ratio along three previous deep greenland ice cores1 3 seemed to reveal irregular but well defined episodes of relatively mild climate conditions interstadials during the mid and late parts of the last glaciation but there has been some doubt as to whether the shifts in oxygen isotope ratio were genuine representations of changes in climate rather than artefacts due to disturbed stratification here we present results from a new deep ice core drilled at the summit of the greenland ice sheet where the depositional environ ment and the flow pattern of the ice are close to ideal for core recovery and analysis the results reproduce the previous findings to such a degree that the existence of the interstadial episodes can no longer be in doubt according to a preliminary timescale based on stratigraphic studies the interstadials lasted from 500 to 2 000 years and their irregular occurrence suggests complexity in the behaviour of the north atlantic ocean circulation

petrography and geochemistry of the carape granitic complex southeastern uruguay the southern sector of uruguay was intruded by numerous granitic plutons during the brasiliano cycle the granites and granodiorites of the carape complex comprise a large part of the neoproterozoic terrain exposed in southern uruguay typological and age relationships show that the characteristic of the granitic rocks changed during the brasiliano cycle four groups of granitoids can be distinguished according to their emplacement the first group corresponds to the campanero unit interpreted as a pre brasiliano basement which includes mainly preorogenic granites the second group pan de azucar and related granitoids includes synorogenic granites and granodiorites the third granitoid group dos hermanos granite and related plutons is classified as late to postorogenic granites finally the fourth group consisting of the aguila granite and related plutons is represented by alkaline amphibole biotite granites and are considered as post collisional alkaline granites which we assign to an extensional event associated with post collisional slab break off marking the end of the late proterozoic brasiliano orogenic cycle most of the granitic plutons in this area 2 300 km2 are relatively well exposed and have well defined intrusive relationships with the metamorphic country rocks these granitic rocks are the result of successive magma pulses from similar magma chambers through the late proterozoic to early paleozoic times

the partial molar volume of carbon dioxide in peridotite partial melt at high pressure abstract the partial molar volume of co2 v c o 2 in silicate melt was determined for a komatiite composition using high pressure sink float experiments in a multi anvil press the density of the experimental melt at pressure was determined by observing sinking and floating of pure forsterite fo100 and forsterite fo90 buoyancy markers values for v c o 2 were bracketed at 4 3 gpa 23 71 cm3 mol and at 5 5 gpa 22 06 cm3 mol normalized to 2123 k combining the current data with previous work we now more accurately constrain the compression curve of v c o 2 over the pressure range of 1 0 10 4 to 20 gpa these data allow the calculation of density at pressure of carbonated silicate melts such as kimberlite and silica undersaturated alkali basalts and the determination of their buoyancy and eruptibility

molecular record of secular sea surface temperature changes on 100 year timescales for glacial terminations i ii and iv high resolution palaeoclimate records based on oxygen isotope data have provided important insights into climate variability and rates of natural climate change on about a thousand year timescale1 3 little is known4 however about the variation of climate and of palaeoceanographic conditions throughout the quaternary on timescales of less than 1 000 years at frequencies far greater than those of the milankovitch orbital cycles here we show that such high time resolution is possible from molecular stratigraphic studies based on biomarker organic molecules alkenones we have sampled alkenone stratigraphic records at 70 to 200 yr intervals across glacial terminations i ii and iv in sediment cores from oop site 658 off northwest africa5 sea surface temperatures ssts derived from the alkenone uk37 index6 8vary rapidly beyond the range of analytical noise by up to 2 5 c in 300 yr showing hitherto unknown cycles with about 600 yr periodicities some of the changes parallel similar events in the oxygen isotope stratigraphy sst oscillations may be linked in part to abrupt breakdowns in atlantic deep water ventilation resulting from meltwater events of quaternary glacial terminations3 9 10

vostok ice core a continuous isotope temperature record over the last climatic cycle 160 000 years a continuous deuterium profile along the 160 000 year vostok ice core antarctica is interpreted in terms of atmospheric temperature changes this climatic record is the awaited terrestrial complement of the deep sea records supporting the existence of a relation between the pleistocene climate and orbital forcing

dielectric stratigraphy of ice a new technique for determining total ionic concentrations in polar ice cores a 133 m deep antarctic ice core from dolleman island antarctic peninsula has been profiled by dielectric measurements in the af lf 20 hz 100 khz frequency range this has revealed large variations in dielectric relaxation and conductivity down the core a comparison with the chemical stratigraphy along 45 m of the core demonstrates for the first time the decisive role played by acids and salts in determining the electrical behaviour of natural ice the total ionic concentration along the ice core can be deduced from the dielectric response this technique may be applied rapidly in the field and as it requires no contact between ice core and electrodes the core is maintained in pristine condition for later chemical analysis

prehistoric blood residues detection on tool surfaces and identification of species of origin blood residues from several animal species have been discovered on the surfaces of chert basalt and obsidian prehistoric tools 1000 to 6000 years old from open air sites along the western coast and in the northern boreal forest of canada a screening test has been developed to detect residual blood hemoglobin has been crystallized from the residues and the species of origin determined

ultra high chlorine in submarine kilauea glasses evidence for direct assimilation of brine by magma basaltic glass grains from the submarine south flank of kilauea hawai i have cl concentrations of 0 01 1 68 wt the latter being the highest cl content yet recorded for a hawaiian glass the high cl glass grains are products of brine assimilation by tholeiite magma the glasses are grains in a sandstone clast from bedded breccias draping the southwestern margin of kilauea s submarine midslope bench the clast contains two distinct suites of glass grains abundant degassed tholeiites perhaps derived from subaerial lavas of mauna loa that shattered upon ocean entry and a smaller population of kea type tholeiite n 17 analyzed that erupted subaqueously based on elevated s 780 1050 ppm h2o 0 42 1 27 wt and co2 1000 ppm six 5000 ppm and two grains have 10 000 ppm dissolved cl abundances of h2o na2o k2o and several trace elements increase regularly with cl concentration and we estimate that cl enrichment was due to up to 13 wt addition of a brine consisting of 78 h2o wt 13 cl 4 4 na 2 6 k 2 6 ca 620 ppm ba 360 ppm sr 65 ppm rb and 7 ppm pb the large amounts of brine addition argue against bulk assimilation of low porosity brine bearing rock the brine s composition is appropriate for a seawater derived hydrothermal fluid that reacted with basaltic wall rocks at t 100 c losing mg and s and gaining k ca rb ba sr and pb followed by phase separation near 500 c and 50 mpa 5 km below sea level at hydrostatic pressure brine was assimilated at or near the depth it formed as estimated on petrologic grounds but under lithostatic conditions the highest extents of assimilation either forced volatile saturation of the magma or enriched already coexisting magmatic vapor in h2o possible mechanisms for assimilation are 1 forcible injection of brine into magma during bursting of overpressured pockets heated by new dikes or 2 intrusion of magma into lenses or sills occupied by trapped brine

ages u pb shrimp and la icpms and stratigraphic evolution of the neoproterozoic volcano sedimentary successions from the extensional camaqua basin southern brazil abstract during the ediacaran southern brazil was the site of multiple episodes of volcanism and sedimentation which are best preserved in the 3000 km2 camaqua basin the interlayered sedimentary and volcanic rocks record tectonic events and paleoenvironmental changes in a more than 10 km thick succession in this contribution we report new u pb and sm nd geochronological constraints for the 605 to 580 ma bom jardim group the 570 ma acampamento velho formation and a newly recognized 544 ma volcanism depositional patterns of these units reveal the transition from a restricted fault bounded basin into a wide shallow basin the expansion of the basin and diminished subsidence rates are demonstrated by increasing areal distribution and compressed isopachs and increasing onlap of sediments onto the basement to the west the sm nd isotopic composition of the volcanic rocks indicates mixed sources including crustal rocks from the adjacent basement both neoproterozoic and paleoproterozoic sources are indicated for the western part of the basin whereas only the older paleoproterozoic signature can be discerned in the eastern part of the basin

hafting wear on quartzite tools an experimental case from the wulanmulun site inner mongolia of north china abstract usewear analysis is one of the most important and significant methods in studying the hafting wear the raw material used in this article is quartzite gathered from identified raw material resource of wulanmulun site and the wooden handle and hemp rope are used as the binding material of accomplishing the experimental study on the hafting wear on quartzite tools the low power technique was applied in observing stone specimens the research shows that the hafting wear on quartzite tools has its own regular pattern that can be well recognized by the low power technique generally the difference of major features and patterns of hafting wear occurred and distributed at areas of the lateral edges surface ridges and basal edges of the lower part on the specimens can be well distinguished the binding material binding method processing way of binding and the morphology of stone specimen themselves can be also affected factors to the hafting wear patterns the present study may contribute a partial set of reference standards in constructing hafting wear patterns on the quartzite tools and aid interpretation of features observed on archaeological assemblages on the basis of the low power technique

mineralizations of the lavalleja group uruguay a probable neoproterozoic volcano sedimentary sequence abstract the lavalleja group is located in the southern extreme of the dom feliciano belt being tentatively correlated with the porongos and brusque groups of brazil the basement of the lavalleja group is probably represented by granitic gneissic rocks of the campanero unit with ages in the southern portion ranging from 1 75 to 2 1 ga u pb in zircon the lavalleja group is characterized by narrow bands of metasedimentary and metavolcanic rocks and it is separated in three formations namely from base to top zanja del tigre fuente del puma and minas outcrops assigned to the minas formation have been recently correlated with the arroyo del soldado group only the fuente del puma formation hosts base metals au and ag ocurrences the fuente del puma formation is divided into three informal units sedimentary volcanic and hornblenditic gabbros the sedimentary unit is characterized by an important amount of carbonates syn collisional to post tectonic granitic bodies carape complex intrudes the lavalleja group and the campanero unit several mineralizations are located in the fuente del puma formation those associated to arrospide ramallo reus chape valencia la oriental apolonia redondo hill la china and la paloma mines are the most important in addition many ocurrences of cu zn pb were recognized in the region the cu zn pb mineralization includes massive sulfides with pyrite chalcopyrite sphalerite galena pyrrothyte arsenopyrite hematite into small bodies with lenticular shape the host rock shows frequently hydrothermal alteration the geochemistry and the geological features of the mineralizations suggest besshi massive sulphide zn cu pb and sedex zn pb as most probably genetic models for the deposits related to the neoproterozoic orogeny early mineralizations are syngenetic and were formed on the sea floor although the main mineralizations are related to remobilization during syn to late metamorphic events and thrusting

h2o co2 solubility in mafic alkaline magma applications to volatile sources and degassing behavior at erebus volcano antarctica we present new equilibrium mixed volatile h2o co2 solubility data for a phonotephrite from erebus volcano antarctica h2o co2 saturated experiments were conducted at 400 700 mpa 1 190 c and nno 1 in non end loaded piston cylinders equilibrium h2o co2 fluid compositions were determined using low temperature vacuum manometry and the volatile and major element compositions of the glassy run products were determined by fourier transform infrared spectroscopy and electron microprobe results show that the phonotephrite used in this study will dissolve 0 8 wt co2 at 700 mpa and a fluid composition of x text h 2 text o 0 4 in agreement with previous experimental studies on mafic alkaline rocks furthermore the dissolution of co2 at moderate to high x text h 2 text o text fluid in our experiments exceeds that predicted using lower pressure experiments on similar melts from the literature suggesting a departure from henrian behavior of volatiles in the melt at pressures above 400 mpa with these data we place new constraints on the modeling of erebus melt inclusion and gas emission data and thus the interpretation of its magma plumbing system and the contributions of primitive magmas to passive and explosive degassing from the erebus phonolite lava lake

evidence for general instability of past climate from a 250 kyr ice core record recent results1 2 from two ice cores drilled in central greenland have revealed large abrupt climate changes of at least regional extent during the late stages of the last glaciation suggesting that climate in the north atlantic region is able to reorganize itself rapidly perhaps even within a few decades here we present a detailed stable isotope record for the full length of the greenland ice core project summit ice core extending over the past 250 kyr according to a calculated timescale we find that climate instability was not confined to the last glaciation but appears also to have been marked during the last interglacial as explored more fully in a companion paper3 and during the previous saale holstein glacial cycle this is in contrast with the extreme stability of the holocene suggesting that recent climate stability may be the exception rather than the rule the last interglacial seems to have lasted longer than is implied by the deep sea specmap record4 in agreement with other land based observations5 6 we suggest that climate instability in the early part of the last interglacial may have delayed the melting of the saalean ice sheets in america and eurasia perhaps accounting for this discrepancy

experimental and functional analysis of late middle paleolithic flake cleavers from southwestern europe france and spain the presence of flake cleavers at the end of the middle paleolithic in the vasco cantabria region southwestern france and northern spain is one element of the variability in mousterian lithic industries in southwestern europe because the function of these tools has rarely been studied we undertook a use wear analysis of them in order to gain a better understanding of the technological characteristics of late middle paleolithic industries in this geographic zone we conducted a series of experiments using these tools for activities associated with the processing of animal and vegetal materials the experimental reference collection thus constituted was subject to a low power use wear analysis and served as the basis of our interpretation of the use wear traces present on the archaeological flake cleavers of several assemblages olha i and ii gatzarria el castillo these flake cleavers revealed similarities with the experimental pieces that were hafted and used for percussion to fell trees and divide carcasses these data allow us to discuss the role of functional and cultural factors in the development of this tool type

a multi analytical methodology of lithic residue analysis applied to paleolithic tools from hummal syria abstract lithic residue analysis is traditionally based upon the morphological identification of microresidues preserved on the surfaces of stone tools in order to improve the reliability of these identifications we apply multiple techniques beyond morphological description to characterize the residues on stone tools from hummal syria we first document the residues using visible light microscopy and scanning electron microscopy and then characterize them using energy dispersive x ray spectroscopy fourier transform infrared microscopy and confocal raman microscopy our analyses confirm that some of the residues are bitumen x ray diffraction analysis of associated sediments is used to identify the other residues

age dating and the orbital theory of the ice ages development of a high resolution 0 to 300 000 year chronostratigraphy using the concept of orbital tuning a continuous high resolution deep sea chronostratigraphy has been developed spanning the last 300 000 yr the chronology is developed using a stacked oxygen isotope stratigraphy and four different orbital tuning approaches each of which is based upon a different assumption concerning the response of the orbital signal recorded in the data each approach yields a separate chronology the error measured by the standard deviation about the average of these four results which represents the best chronology has an average magnitude of only 2500 yr this small value indicates that the chronology produced is insensitive to the specific orbital tuning technique used excellent convergence between chronologies developed using each of five different paleoclimatological indicators from a single core is also obtained the resultant chronology is also insensitive to the specific indicator used the error associated with each tuning approach is estimated independently and propagated through to the average result the resulting error estimate is independent of that associated with the degree of convergence and has an average magnitude of 3500 yr in excellent agreement with the 2500 yr estimate transfer of the final chronology to the stacked record leads to an estimated error of 1500 yr thus the final chronology has an average error of 5000 yr