tektites apollo the crust and planets a life with trace elements stuart ross taylor msc university of new zealand phd indiana university scd university of oxford faa ac always called ross grew up on a farm near ashburton new zealand ross has worked on a wide variety of topics in trace element geochemistry including the composition and evolution of the moon the continental crust tektites impact glasses and island arc rocks in 1969 he carried out the first chemical analysis of the first returned lunar sample at nasa in houston he has published 10 books and 240 papers in scientific journals he was awarded the v m goldschmidt award of the geochemical society in 1993 in 1994 he was elected a foreign associate of the national academy of sciences in 1998 he was awarded the leonard medal of the meteoritical society in 2002 the bucher medal of the american geophysical union and in 2012 the shoemaker distinguished lunar scientist medal of the nasa lunar science institute asteroid 5670 is named rosstaylor

comparison of the geochemistry of ophiolitic pyroxenites with a strongly fractionated dyke of pyroxenite from the sakhakot qila ophiolite pakistan abstract exceptionally strong fractionation has been found amongst the pyroxenite dykes crosscutting the ultramafic rocks of the sakhakot qila ophiolite pakistan one such dyke an fe websterite is particularly fractionated and anomalously feenriched and mg depleted this is supported by the data from whole rock analyses of major trace and rare earth elements as well as by the mineral chemistry of the constituent chromian spinel olivine clinopyroxene orthopyroxene and magmatic amphibole secondary sulphides of the fe websterite include troilite pentlandite instead of the awaruite heazle woodite pentlandite assemblage typical of all the other ultramafic rocks of the host ophiolite the non cumulate parent liquid of the magnesian pyroxenites crystallized in an initial episode when the surrounding cumulates were still hot in a belated second episode the fe websterite may have crystallized in isolated pockets after its differentiation to an extent much greater than that known from most pyroxenite dykes in ophiolites

ferro andesites in the grande ronde basalt their composition and significance in studies of the origin of the columbia river basalt group flows from the grande ronde basalt of the columbia river basalt group include several with the chemical composition of ferro andesites these flows have sio2 55 mgo 4 and also have higher fe mg than the average value for grande ronde basalt they are also distinctly richer in cs rb k ba la ce th and u than the remainder of the grande ronde basalt flows and possess small negative eu anomalies their pb isotopic compositions define a mixing line with a negative slope on a 206pb 204pb versus 207pb 204pb plot their nd isotopic compositions lie between 143nd 144nd 0 51252 and 0 51264 and their sr isotopic compositions lie between 87sr 86sr 0 7055 and 0 7060 these values define the enriched end of the columbia river basalt group spectrum on a sr nd epsilon diagram excluding the saddle mountains basalt these ferro andesite flows also form a compositional end member of the columbia river basalt group and are sufficiently distinctive to warrant special consideration we compare them with

a methane bubble curtain in meromictic sakinaw lake british columbia hydroacoustic surveys in meromictic sakinaw lake found an approximate 20 m wide dual column bubble curtain originating from a depth of 42 60 m all around the main basin at the interface between the chemocline and the sediments with the exception of the small upper basin sakinaw lake is oligotrophic and permanently salt stratified with a 30 m mixolimnion overlying an anoxic monimolimnion containing high concentrations of sodium chloride and dissolved sulfide nitrogen is the major factor limiting the lake s phytoplankton productivity the mainly methane bubbles in the curtain have a fairly narrow range of sizes with most of the bubbles 75 having radii between 600 and 850 mm with a peak at 735 mm which is close to a third of the size of bubbles reported for kinneret lake in israel we hypothesize that different bubble generation mechanisms cause this difference a simple bubble evolution model that includes gas dissolution and buoyancy is in good agreement with the acoustically observed bubble characteristics and is used to infer bubble densities and gas flux rates few of the bubbles reach the surface with any methane left in them the bubble flux of methane into the upper part of the lake is 3 mg m22 yr21 the dual column nature of the bubble plume and the extensive and persistent nature of the bubble curtain around the lake suggest that there may be unique physical and biological conditions in sakinaw lake affecting methane generation and bubble ebullition

geochemistry of muong nong type tektites iv selected trace element correlations muong nong type tektites are distinct from other tektites in their shape size petrographical characteristics and chemistry volatile elements are enriched but other trace elements do not show large differences when compared to normal splash form tektites an analysis is made of nineteen muong nong type tektites for 40 50 elements fifteen nonvolatile elements are discussed in this paper it is shown that the muong nong type tektites are very restricted in chemical composition and are almost indistinguishable from the australasian tektites elemental ratios calculated from the data reported here show the same genetic connection all elementary abundances and ratios are fully consistent with terrestrial sediments the nonvolatile elements may record more about the conditions of the origin

the composition and evolution of the continental crust rare earth element evidence from sedimentary rocks the composition of the present day upper crust inferred from the uniformity of sedimentary rock r e e rare earth element patterns is close to that of granodiorite a revised andesite model is used to obtain total crustal composition the lower crust is the composition remaining assuming that the upper crust one third of the total is derived from intracrustal partial melting the upper crustal r e e pattern has pronounced eu depletion eu eu 0 64 the lower crustal pattern has eu enrichment eu eu 1 17 and the total crust has no eu anomaly relative to chondritic abundances the eu depletion in the upper crust is attributed to retention of eu in plagioclase in the lower crust because plagioclase is not stable below 40 km 10 kbar the anomaly is intracrustal in origin the archaean upper crust has a different r e e pattern to that of the present day upper crust being lower in total r e e and la yb ratios and lacking an eu anomaly these data are used to infer the archaean upper crustal composition which resembles that of the present day total crust except that ni and cr contents are higher the archaean crustal composition can be modelled by a mixture of tholeiites and tonalite trondhjemites the latter have steep light r e e enriched heavy r e e depleted patterns consistent with equilibration with garnet and hence probable mantle derivation there is little reason to suppose that the archaean lower crust was different in composition from the upper crust except locally where partial melting episodes occurred the r e e evidence is consistent with isotopic and geological evidence for a low continental growth rate in the early archaean a massive increase to about 70 of the total crust between about 3000 and 2500 ma b p and a slow increase until the present day the change from archaean to post archaean r e e patterns in the upper crust is not isochronous but is reflected in the sedimentary rock r e e patterns at differing times in different continents on the basis of a model composition for the mantle 36 of the potassium 30 of uranium 15 of lanthanum and 3 of ytterbium are concentrated in the present continental crust this enrichment is related to ionic size and valency differences from common mantle cations e g mg fe pre 3 9 ga b p crusts were obliterated by meteorite bombardment no geochemical evidence exists for primordial anorthositic sialic or mafic crusts

nd and sr isotopic systematics of central australian granulites chronology of crustal development and constraints on the evolution of lower continental crust nd and sr isotopic data are reported for a granulite terrain in the proterozoic arunta block of central australia sm nd data from a wide range of rock types define a crust formation age of 2 070 125 ma and provide further evidence for voluminous crustal growth in the proterozoic an nd value of 1 5 0 8 indicates a depleted mantle source for this crustal segment and there is no evidence for a large component of significantly older sialic crust field relationships geochemistry and rb sr data for mafic and felsic granulites indicate that intracrustal differentiation and polyphase deformation were followed by granulite facies metamorphism rb depletion at 1 800 ma rb sr data for strongly retrogressed granulites define an age of 1 700 ma which is interpreted as the time of retrograde biotite growth partial melting at the presently exposed crustal level and anatexis at deeper crustal levels were broadly coeval with the retrograde metamorphism sm nd and rb sr isotopic systematics of minerals indicate that the terrain cooled slowly did not experience significant uplift until 1 000 ma and remained at temperatures above 320 c until the late palaeozoic the mineral data are consistent with geological relationships and petrological evidence for a prolonged period of isobaric cooling followed by uplift late in the metamorphic evolution of the terrain the granulite protoliths appear to have formed in a rift which closed within 280 ma of initial separation deformation and granulite facies metamorphism at 1 800 ma are interpreted to be a consequence of collision between the continental blocks which defined the rift regional retrogression and granitoid magmatism at 1 700 ma are attributed to underthrusting of the granulites by lower grade rocks in the final stages of collision subsequent events in the cooling and uplift history appear to have been controlled by the presence of long lived major faults in the crust and a prolonged history of episodic compression in the continental lithosphere the results of this study suggest that granulite terrains in general cannot be equated with lower continental crust but instead represent assemblages of mainly supracrustal rocks which in some instances have been involved in major collision events

rb cs fractionation a link between granulite metamorphism and the s process abstract high grade metamorphism of pelitic sediments produces large cs losses with little k and rb depletion island arc volcanics contain an enhanced cs component relative to k and rb we suggest a connection between these two processes whereby fluids or melts removed from feldspar bearing subduction assemblages under high grade metamorphic conditions are enriched in cs relative to k and rb these cs enriched components infiltrate subarc mantle and lead to ubiquitous cs enrichment in arc volcanics normal oceanic magmatism is not effective in fractionating rb cs therefore the canonical oceanic basalt value of 85 for rb cs is distinctive relative to processes involving sediments recycling fluid melt metamorphism and arc volcanism

afromontane foragers of the late pleistocene site formation chronology and occupational pulsing at melikane rockshelter lesotho this paper provides a preliminary chronostratigraphic and palaeoenvironmental framework for the late pleistocene archaeological sequence at melikane rockshelter in mountainous eastern lesotho renewed excavations at melikane form part of a larger project investigating marginal landscape use by late pleistocene foragers in southern africa geoarchaeological work undertaken at the site supports in eld observations that melikane experienced regular often intensive input of groundwater via ssures in the shelter s rear wall this strong hydrogeological connection resulted in episodic disturbances of the sedimentary sequence exacerbated by other processes such as bioturbation despite this taphonomic complexity a robust chronology for melikane has been developed based on tightly cross correlated accelerator mass spectrometry ams 14 c with acid base wet oxidation stepped combustion abox sc pretreatment and single grain optically stimulated luminescence osl dating the results show that human occupation of melikane was strongly pulsed with episodes of late pleistocene occupation at w80 w60 w50 w46e38 and w24 ka at least three additional occupational pulses occurred in the holocene at w9 ka w3 ka and in the second millennium ad but these are dealt with only brie y in this paper implications of the late pleistocene pulsing for the colonisation of high elevations by early modern humans in africa ahead of dispersals into challenging landscapes beyond the continent are discussed

geochemical effects of decoupled fractional crystallization and crustal assimilation most models of crustal assimilation assume that the amount of assimilant added to the magma is proportional to each infinitesimally small amount of solid removed during crystallization afc in some magmatic systems however assimilation and crystallization are not strictly related and the mass assimilated is decoupled from and therefore varies independently of the mass crystallized fca the geochemical consequences of fca are examined and compared to those of afc the behavior of incompatible elements is identical during afc and fca and ratios of these elements do not allow discrimination between the two processes major oxide least squares mass balance models do not discriminate between afc and fca at f 0 7 f fraction of melt remaining however fca yields magmas richer in compatible elements and with higher sr isotopic ratios than afc at a given value of f repeated cycles of fca and afc combined with magma mixing fam may result in unusual geochemical trends such as the evolution of a calc alkaline basaltic parent to a tholeiitic daughter magma or the evolution of low and medium k calc alkaline basalts to high k andesites dacites trachyandesites or trachydacites lavas erupted by the volcano micro profitis ilias on santorini hellenic arc greece provide an example of magmas which evolved by combined fractionation assimilation by fca and mixing

a paleohydrologic reinterpretation of the homeb silts kuiseb river central namib desert namibia and paleoclimatic implications abstract slack water deposits are usually fine grained fine sand and coarse silt flood sediments deposited in areas of the floodplain that are sheltered from high velocity flood flows slack water deposits have been recognized by many investigators in a wide variety of physiographic and climatic settings late quaternary slack water deposits have not been described from the extremely arid namib desert of southwestern africa fine grained flood sediments in the kuiseb valley near homeb accumulated between 23 000 and 19 000 14c years bp have been interpreted by previous workers as i sediments deposited behind dune dams ii river endpoint accumulations and iii flood deposits of an aggrading river controlled either by a base level change in the lower reaches or a change in the hydrological regime in the catchment area furthermore the so called homeb silts could document more arid climatic conditions in the kuiseb catchment area during the last glacial maximum lgm our research shows that the homeb silts are slack water deposits and that in many valleys of the namib desert slack water sediments are observed most commonly at the junctions of major rivers and minor tributaries in bedrock canyon settings here we present evidence that these slack water deposits accumulated as a result of more humid conditions and or more intense precipitation events in the upper reaches of the river they do not document climatic changes in the desert itself as postulated by many researchers

heat treatment in the south african middle stone age temperature induced transformations of silcrete and their technological implications abstract it was recently found that silcrete raw material was heat treated during the south african middle stone age msa for altering its flaking properties this finding led to hypotheses about the implications for the msa hunter gatherers such as the cost of thermal treatment in terms of investment and firewood to date these hypotheses lack a solid basis for data on the thermal transformations of south african silcrete and hence the necessary heating procedure and heating environment is missing in order to produce such data we conducted an experimental study within the framework of the diepkloof project this work is based on the petrographic mineralogical and structural analysis of south african silcrete from the west coast and its thermal transformations our results shed light on the nature of these transformations the ideal heating temperatures and the tolerated heating speed the processes occurring in silcrete are comparable to flint i e the loss of chemically bound water and the formation of new si o si bonds but their intensity is less pronounced effective heating temperatures are significantly higher than for flint and the heating speed tolerated by south african silcrete is relatively fast these findings imply that silcrete heat treatment cannot be directly compared with flint heat treatment unlike flint heating silcrete does not require the setup of a dedicated heating environment and may have been performed in the same time as other fire related activities this would represent only a minor supplementary investment in time and firewood these results have broad implications for the discussion about technological evolution and the acquisition of specialised knowledge in the msa

methane efflux from bubbles suspended in ice covered lakes in syowa oasis east antarctica 1 this is the first estimation of methane efflux from bubbles in lake ice in antarctica bubbles suspended in shallow ice in 20 lakes were observed as part of the operations of the 45th japanese antarctic research expedition in ice free rocky areas along the eastern coast of lutzow holm bay syowa oasis in east antarctica in 2004 anomalous methane concentrations in bubbles suspended in lake ice and anomalous dissolved methane concentrations in lake water were frequently found methane concentrations in bubbles varied of 5 orders of magnitude from 1 9 ppmv to 18 vol vol a procedure that makes estimations of methane flux from ice bubbles possible has been developed on the basis of a relationship between bubble density distribution brightness observed by digital photographs and methane concentration in bubbles such a procedure applied to lake oyako ike in the skarvsnes area where the maximum methane concentration was observed suggests that total bubble volume is about 0 6 of ice volume and the mass of methane in bubbles in the lake is about 74 kg almost all gases in bubbles are released to the atmosphere in the early ice melt season a period of a few weeks in december and january by applying area fraction frequency distributions to methane concentration ranges for 20 lakes surveyed extrapolation to the whole syowa oasis including 110 lakes would give a provisional estimate of total emission of about 2 tons ch4 yr

the origin and earliest state of the earth s hydrosphere the origin and earliest history of the earth s hydrosphere the inventory of excess volatiles defined by rubey in 1951 can be constrained within wide but useful limits by a consideration of empirical and theoretical evidence from astrophysics and geology models for the evolution of the solar system from the protoplanetary nebula and for the growth of the earth to its present dimensions suggest quite strongly that the hydrosphere came into being during accretion its format with h2o mostly in the oceans co2 mostly in sediments and a residual atmosphere dominated by n2 co2 and h2o was established at a very early date and has persisted without large destabilizing climatic excursions until the present day alternative accounts of early history in which the earth either loses a massive primordial atmosphere or acquires its secondary atmosphere by gradual degassing seem improbable on the basis of a series of circumstantial but cumulatively persuasive arguments the difficulty of dissipating a massive atmosphere of solar composition in reasonable times the likelihood that accretion was a highly energetic process and that it triggered early segregation of the core and the tendency of the planet to accumulate volatiles preferentially in the later stages of accretion are examples of arguments favoring an early origin for the hydrosphere several geological isotope systems which can be sampled today require early separation of the atmosphere and probably the hydrosphere as a whole these systems record radiogenic enrichment patterns in the noble gases and stable isotope fractionations which suggest an early origin of the biosphere certain geological indicators of atmospheric composition and the broadly equable character of the rock record are also consistent with a hydrosphere established in the earliest stages of history and having an initial neutral or weakly reduced composition the climatic stability of such a hydrosphere poses crucial questions especially since the early sun was less luminous we find that it is not paradoxical to have an early earth with surface temperature close to that of the present day if the major hydrospheric constituent is liquid water a near global ocean and a cloudy atmosphere provide thermal feedbacks which suffice to maintain climatic stability against the perils of the deep freeze and the runaway greenhouse large quanltities of atmospheric greenhouse gases are not required for climatic stability although co2 may well have been present in amounts larger than today s large expanses of dry land are however difficult to accommodate in the picture which we present but the evidence favors differentiation of the continents later in geological history than the early times which we consider localized glacier ice is permitted and perhaps likely and may provide a milieu favorable for chemical evolution

regional o sr and pb isotope relationships in late cenozoic calc alkaline lavas of the andean cordillera quaternary recent volcanism in the andes has occurred in three regions 45 33 s 28 16 s and 2 s 5 n each of which has a distinct plate tectonic setting and contains volcanic suites with different chemical and isotopic characteristics isotope ratios of o and sr are lowest and those of pb least variable in the southern volcanic zone svz where medium k lavas have isotopic characteristics equivalent to volcanics from intraoceanic arcs where continental crust is absent the svz lavas were probably derived from an asthenospheric mantle source above a shallow benioff zone parental basaltic magmas rose largely unmodified through thin continental crust where differentiation occurred by low pressure crystal fractionation without concurrent modification of isotopic composition the slight enrichment of 206 pb in the northern volcanic zone nvz where the crust is thin and the benioff zone deep suggests a greater subduction zone component for parental medium k magmas the slight 18 o enrichment suggests a small amount of lower crustal interaction isotope ratios of o and sr are highest and those of pb most variable in the central volcanic zone cvz parental magmas in the cvz were probably generated within the same mantle source region as those in the svz and nvz subsequently during transit through the exceptionally thick continental crust of the central andes high k magmas were produced by a combination of bulk contamination in the lower crust and later low pressure fractional crystallization assimilation processes in the upper crust which altered both chemical and isotopic compositions

new ages for the post howiesons poort late and final middle stone age at sibudu south africa abstract optically stimulated luminescence osl measurements are reported for single grains of quartz from deposits within sibudu rock shelter such measurements enable rejection of unrepresentative grains and application of the finite mixture and central age models to obtain the most reliable age estimates three types of single grain equivalent dose de distributions were observed one sample represented a single dose population three samples indicated mixing between iron age ia and middle stone age msa deposits and 10 samples in addition to the three mixed samples showed scattered distributions the latter type resulted from differences in the beta dose received by individual grains for these samples the beta doses were modelled and adjusted accordingly ages for the 14 samples collected from msa deposits post dating the howiesons poort hp resulted in three age clusters which are stratigraphically consistent with the three informally named cultural phases at sibudu namely the post hp late msa and final msa weighted mean ages of 58 5 1 4 ka 47 7 1 4 ka and 38 6 1 9 ka were calculated for these phases respectively the three phases were separated by two occupational hiatuses with durations of 10 8 1 3 ka and 9 1 3 6 ka we hypothesise that the punctuated presence of humans at sibudu was determined by large scale fluctuations in climate during oxygen isotope stage ois 3 which resulted in alternating wet and dry periods phases of occupation correspond to wet periods when fresh water was available in the tongati river whereas intervals of site abandonment correspond to dry periods when people were forced to migrate in search of a reliable source of fresh water where people migrated to remains unresolved

tectonics and evolution of venus the global tectonics of venus differs significantly from that of earth most markedly in that the surface is covered predominately by gently rolling terrain there apparently are no features like ocean rises the gravity is positively correlated with topography at all wavelengths and the few highlands are estimated to be supported or compensated at a depth of approximately 100 kilometers the surface of venus appears to be covered mainly by an ancient crust the high surface temperature making subduction difficult it seems likely that well over 1 billion years ago water was destabilized at the surface and soon after plate tectonics ceased the highlands appear to be actively supported presumably as manifestations of long enduring hot spots

no water no granites no oceans no continents water is essential for the formation of granite and granite in turn is essential for the formation of continents earth the only inner planet with abundant water is the only planet with granite and continents the moon and the other inner planets have little or no water and no granites or continents

nature and significance of the howiesons poort to post howiesons poort transition at klein kliphuis rockshelter south africa abstract this paper considers the transition from howiesons poort to post howiesons poort technologies at the rock shelter site of klein kliphuis south africa the transition at this site is shown to be gradual with incremental changes in material selection and in the size and shapes of flakes and cores implements which appear to blend characteristics of those distinctive of the earlier and later industries appear briefly at the mid point of the transition the results suggest that there is unlikely to have been an occupational hiatus between the howiesons poort and post howiesons poort explanations for the howiesons poort phrased in terms of population expansion and contraction are also difficult to support technological changes at this time may relate to environmental variation though the limited nature of terrestrial archives documenting changes in resource productivity necessitate that any such suggestion be made with caution

influence of palaeoclimate and hydrothermal activity on organic matter accumulation in lacustrine black shales from the lower cretaceous bayingebi formation of the yin e basin china abstract the lacustrine black shales of the lower cretaceous bayingebi formation are an important hydrocarbon source rock in the yin e basin it is important to understand the mechanism of organic matter accumulation in these shales to reconstruct the palaeoenvironment and palaeoclimate in the early cretaceous in northwestern china and search for potential oil and gas resources based on petrological elemental geochemical and organic geochemistry analyses of typical field profile samples the influence of palaeoclimate and hydrothermal activity on organic matter accumulation in different sedimentary units unit i ii and iii is revealed unit ii has the highest total organic matter abundance tocavg 5 95 mainly type i kerogen lamalginite which is in the immature to low mature stage organic carbon isotope data 13corg element ratios sr cu and c value and weathering indexes including cia ciw and pia together revealed that the region experienced a semihumid to semiarid palaeoclimate in the middle of the early cretaceous the increase in rainfall in unit ii enhanced the abundance of lake algae and surrounding terrestrial vascular vegetation and elevated the lake level which contributed to adequate sources and favourable preservation conditions for organic matter accumulation several lines of evidence including high sulfur contents the combination of vein pyrite and micritic dolomite positive eu anomalies and element geochemical correlations confirm the existence of intermittent low temperature white smoker type hydrothermal activity the decrease of oxygen content in lake bottom water may be related to the input of hydrothermal fluid which provided necessary nutrient elements for biological productivity according to palaeontological and radioisotope dating data it can be inferred that the black shales of the bayingebi formation are the product of the combined effect of global palaeotemperature rise in the early aptian stage of the early cretaceous and intermittent low temperature hydrothermal activity

the mineral chemistry of new titanates from the jagersfontein kimberlite south africa implications for metasomatism in the upper mantle new members of the crichtonite mineral series are described in which k ba ca and ree are in significant concentrations 5 wt oxides filling the a formula position in am21o38 these phases are chromium 16 wt cr2o3 titanates 58 wt tio2 enriched in zro2 5 wt and constitute a mineral repository for refractory and large ion lithophile elements in the upper mantle the mineral senes coexists with mg cr ilmenite nb cr rutile and ca cr nbzr armalcolite that have equally unusual chemistries kimberlitic crichtonites are depleted in the intermediate lanthanides but highly enriched in lree and hree with chondrite normalized abundances of 103 to 105 crichtonite armalcolite and nb cr rutile occupy a compositional range in tio2 contents bridging the gap between ilmenite and rutile two minerals having a widespread distribution in kimberlites and mantle derived nodule suites in common with other associations and based on similarities in mineral chemistry it is concluded that these minerals formed at p 20 30 kb 900 1100 c by reaction of peridotite with metasomatizing fluids kimberlitic crichtonite may be expressed as spinel cr ferropseudobrookite and armalcolite is equivalent to cr geikielite rutile in the system femg tio2 cr2o3 this system contains a number of cr ti compounds not found as minerals but it is proposed that the ubiquitous occurrence of ilmenite intergrowths in kimberlitic rutile results from decomposition of high pressure pbo2 type crystallographic shear structures the new minerals have exotic chemistries and the high k affinities broaden the scope for the origin of alkalic rocks the generation of highly potassic magmas in the upper mantle and suggest that alkali metasomatism may be pervasive

fluvial deposits as an archive of early human activity progress during the 20 years of the fluvial archives group fluvial sedimentary archives are important repositories for lower and middle palaeolithic artefacts throughout the old world especially in europe where the beginning of their study coincided with the realisation that early humans were of great antiquity now that many river terrace sequences can be reliably dated and correlated with the globally valid marine isotope record potentially useful patterns can be recognized in the distribution of the find spots of the artefacts that constitute the large collections that were assembled during the years of manual gravel extraction this paper reviews the advances during the past two decades in knowledge of hominin occupation based on artefact occurrences in fluvial contexts in europe asia and africa as such it is an update of a comparable review in 2007 at the end of igcp project no 449 which had instigated the compilation of fluvial records from around the world during 2000 2004 under the auspices of the fluvial archives group an overarching finding is the confirmation of the well established view that in europe there is a demarcation between handaxe making in the west and flake core industries in the east although on a wider scale that pattern is undermined by the increased numbers of lower palaeolithic bifaces now recognized in east asia it is also apparent that although it seems to have appeared at different places and at different times in the later lower palaeolithic the arrival of levallois technology as a global phenomenon was similarly timed across the area occupied by middle pleistocene hominins at around 0 3 ma

large fractionations of c and h isotopes related to methane oxidation in arctic lakes microbial oxidation of methane ch4 plays a central role in carbon cycling in arctic lakes reducing potential ch4 emissions associated with warming isotopic signatures of ch4 13c and 2h are indicators of microbial oxidation wherein the process strongly enriches 13c and 2h in residual ch4 we present 13c and 2h measurements obtained from sampling the water column and sediment for dissolved ch4 from three small arctic lakes in western greenland under both open water and ice covered conditions from 2013 to 2014 despite substantial variations in aquatic chemistry among the lakes 13c and 2h of ch4 suggested that ch4 was produced predominantly by acetoclastic methanogenesis in the littoral sediments and hydrogenotrophic methanogenesis in the profundal sediments in all of the lakes surprisingly large variations for both 13c and 2h of ch4 were observed with 13c extending from 72 to 7 4 and 2h from 390 to 250 the ch4 isotopic values reported here were significantly more enriched p 0 0001 in both 13c and 2h than values reported from other arctic freshwater environments as is characteristic of methanotrophy the enrichment in 13c and 2h was associated with low ch4 concentrations we suggest that the ch4 most enriched in 13c and 2h may reflect unusually efficient methanotrophic communities in arctic ice margin lakes this study provides the first measurement of 2h for ch4 in an arctic freshwater environment at concentrations 10 m the extreme enrichment of 13c and 2h of ch4 from arctic methanotrophy has significant implications for interpreting sources and sinks of ch4 without knowledge of local geology stable isotope values of ch4 higher than 30 for 13c and 150 for 2h could be misinterpreted as thermogenic geothermal or abiogenic origins given crystalline bedrock and the strong positive correlation between 13c and 2h throughout the water columns in three arctic lakes confirms that ch4 heavily enriched in 13c and 2h is the result of methanotrophy

mantle convection and early crustal evolution abstract the existence of peridotitic komatiites in the archaean suggests that the archaean mantle was significantly hotter than the modern mantle this evidence is contradicted by estimates of archaean continental geothermal gradients based on the pressure and temperature recorded in metamorphic rocks which suggest that there is no marked difference between archaean and modern continental geothermal gradients numerical modelling shows that small changes in the mantle temperature can have an important influence on convection if the average temperature of the upper mantle is increased by 200 c convection within the mantle becomes chaotic and an upper mantle partial melt zone encircles the globe the crust formed during this period will be komatiitic in composition but will be unstable and will be mixed back into the mantle by subduction later when the mantle temperature falls to 100 c above its present level the upper mantle partial melt zone contracts away from subduction areas it is suggested that the first primitive felsic magmas were generated at subduction zones the appearance of these magmas at 3 8 ga permitted the formation of buoyant continents and eventually led to crustal thickening as a consequence of this thickening the proto continents consisting of a bimodal suite of basalts and sodic granodiorites contained two types of latent energy 1 radioactive energy held in elements such as th k and u and 2 potential energy resulting from the elevation of the continents above sea level the potential energy of the continents led to sedimentation the increase in the rate of sedimentation during the archaean resulted from increased crustal buoyancy at the same time heat released by radioactive elements in the deep crust built up under the insulating blanket of the upper crust this caused a major metamorphic metasomatic and crustal melting event which produced the potassic granites of the late archaean once the radioactive elements had been removed from the lower crust that region of the continent become tectonically stable the proterozoic shelf sediments were deposited at the margins of these stable cratons convection models of the archaean mantle show hot diapirs rising from the boundary layer above the core mantle interface we suggest that these diapirs began to melt at a depth of 450 km giving rise to komatiitic magmas this model requires the average temperature of the archaean upper mantle to be 100 c above that of the modern mantle the similarity between archaean and modern continental geothermal gradients can be explained if archaean continents formed above subduction zones raising the temperature of the archaean mantle by 100 c 1 halves the thickness of the oceanic lithosphere 2 increases the oceanic geothermal gradient at the mid point of a convection cell 3 decreases the viscosity of the mantle by at least an order of magnitude the combination of these effects produces a marked decrease in the strength of the archaean lithosphere and mantle thus the form of archaean tectonics can be expected to have been very different from modern tectonics

chemical inhomogeneity of the mantle geochemical considerations geochemical considerations on the overall abundances for major chemical elements of the earth and ci chondrites indicate that the lower mantle is probably more enriched in silica than the upper mantle it is concluded that about 95 of the lower mantle is composed of material having the perovskite modification and that the 650 km seismic discontinuity represents a chemical boundary at which the lower mantle is about 30 to 40 richer in silicon than the upper mantle these results support those reached earlier on the basis of geophysical constraints thus about half of the earth either by weight or volume is composed of ferromagnesium silicate with the perovskite structure

palaeoflood record of the tagus river central spain during the late pleistocene and holocene abstract palaeoflood hydrology of the tagus river central spain was reconstructed from slackwater deposits and palaeostage indicators in two canyon reaches located at el puente del arzobispo in the central part of the catchment 35 000 km 2 in drainage area and in alcantara at the lower part of the catchment 52 000 km 2 in drainage area near the portuguese border the palaeoflood record with more than 80 flood events shows clusters of floods at specific periods from 9440 to 9210 14 c yr bp 8540 8110 bc 8500 to 8000 14 c yr bp 7500 7000 bc 6750 14 c yr bp 5000 bc 1200 to 950 14 c yr bp ad 785 1205 410 14 c yr bp ad 1450 1500 170 to 80 14 c yr bp ad 1670 1950 the largest flood s occurred during the periods 9440 to 9210 14 c yr bp 6750 14 c yr bp and 1200 to 950 14 c yr bp reaching minimum discharge estimates of between 4000 and 4100 m 3 s 1 in the el puente del arzobispo reach and 13 700 15 000 m 3 s 1 in the alcantara reach these periods with increased flood magnitude and or frequency in the tagus river are strongly related to increased moisture influx and winter precipitation in the iberian peninsula especially in the western zone proxy records sensitive to winter precipitation such as lake levels and vegetation changes indicated by pollen records are in good agreement with the clusters of floods found in the tagus river this flood variability seems to correspond to changes in the prevailing atmospheric circulation pattern affecting the iberian peninsula

origin of basal dolomitic claystone in the marsili basin tyrrhenian sea abstract red brown dolomitic claystones overlay the marsili basin basaltic basement at odp site 650 sequential leaching experiments reveal that most of the elements considered to have a hydrothermal or hydrogenous origin in a marine environment such as fe cu zn pb co ni are present mainly in the aluminosilicate fraction of the dolomitic claystones their vertical distribution content and partitioning chemistry of trace elements and ree patterns suggest enhanced terrigenous input during dolomite formation but no significant hydrothermal influence from the underlying basaltic basement positive correlations in the c and o isotopes in the dolomites reflect complex conditions during the dolomitization the stable isotopes can be controlled in part by temperature variations during the dolomitization majority of the samples however form a trend that is steeper than expected for only temperature control on the c and o isotopes the latter indicates possible isotopic heterogeneity in the proto carbonate that can be related to arid climatic conditions during the formation of the basal dolomitic claystones in addition the dolostones stable isotopic characteristics can be influenced by diagenetic release of heavier 18o from clay dehydration and or alteration of siliciclastic material strontium and pb isotopic data reveal that the non carbonate fraction the dye of the dolomitic claystones is controlled by saharan dust 75 80 and by material with isotopic characteristics similar to the aeolian arc volcanoes 20 25 the non carbonate fraction of the calcareous ooze overlying the dolomitic claystones has a sr and pb isotopic composition identical to that of the dolomitic claystones indicating that no change in the input sources to the sedimentary basin occurred during and after the dolomitization event combination of climato tectonic factors most probably resulted in suitable conditions for dolomitization in the marsili and the nearby vavilov basins the basal dolomitic claystone sequence was formed at the initiation of the opening of the marsili basin 2 ma which coincided with the consecutive glacial stage the glaciation caused arid climate and enhanced evaporation that possibly contributed to the stable isotope variations in the proto carbonate the conductive cooling of the young lithosphere produced high heat flow in the region causing low temperature passive convection of pore waters in the basal calcareous sediment we suggest that this pumping process was the major dolomitization mechanism since it is capable of driving large volumes of seawater the source of mg2 through the sediment the red brown hue of the dolomitic claystones is terrigenous contribution of the glacially induced high eolian influx and was not hydrothermally derived from the underlying basaltic basement the detailed geochemical investigation of the basal dolomitic sequence indicates that the dolomitization was most probably related to complex tectono climatic conditions set by the initial opening stages of the marsili basin and glaciation

settlement patterns during the earlier and middle stone age around langebaan lagoon western cape south africa the landscape around langebaan lagoon in the western cape of south africa contains a rich archive of middle and late pleistocene hominin behavior stone age localities of all ages are abundant and present a valuable perspective on the region s settlement history a complex pattern of land use is evident starting with an analysis of the earlier stone age esa collections from anyskop combined with a review of data from elandsfontein and duinefontein these late acheulian assemblages demonstrate an emphasis on handaxe production the exploitation of medium and large game and use of non local raw materials while seasonal pans provided water for animals and humans at these esa localities anyskop is distinctive because of its hilltop setting lacking water and direct access to game middle stone age msa assemblages from geelbek and anyskop combined with a review of data from hoedjiespunt sea harvest and ysterfontein provide further evidence for a regional settlement system that also incorporated non local raw materials into the lithic provisioning strategy some msa lithic technologies in the western cape were aimed at the production of bifacial points and blades as well as backed elements subsistence strategies expanded to encompass the utilization of both terrestrial and marine resources although symbolic artifacts are rare from these sites worked ochre is present at hoedjiespunt these behavioral patterns suggest that the middle and late pleistocene hominins who left these esa and msa materials behind were adept masters of their environment with adaptations well suited to the west coast landscape

late quaternary dynamics of southern africa s winter rainfall zone abstract variations in the nature and extent of southern africa s winter rainfall zone wrz have the potential to provide important information concerning the nature of long term climate change at both regional and hemispheric scales positioned at the interface between tropical and temperate systems southern africa s climate is influenced by shifts in the intertropical convergence zone the westerlies and the development and position of continental and oceanic anticyclones over the last glacial interglacial cycle substantial changes in the amount and seasonality of precipitation across the subcontinent have been linked to the relative dominance of these systems central to this discussion has been the extent to which the region s glacial climates would have been affected by expansions of antarctic sea ice equatorward migrations of the westerlies more frequent intense winter storms and an expanded wrz this paper reviews the developing body of evidence pertaining to shifts in the wrz and the evolution of ideas that have been presented to explain the patterns observed dividing the region into three separate axes along the western and southern margins of the continent and across the interior into the karoo and the kalahari a range of evidence from both terrestrial sites and marine cores is considered and potential expansions of the wrz expansions are explored despite the limitations of many of the region s proxy records a coherent pattern has begun to develop of a significantly expanded wrz during phases of the last glacial period with the best documented being between 32 17 ka while more detailed inferences will require the recovery and analysis of longer and better dated records this synthesis provides a new baseline for further research in this key region

prediction of some weathering trends of plutonic and volcanic rocks based on thermodynamic and kinetic considerations abstract the exposed crust consists mainly of plagioclase 35 quartz 20 k feldspar 11 volcanic glass 12 biotite 8 and muscovite 5 quartz is a resistate thus feldspars and glass represent approximately 75 percent of the labile minerals the weathering characteristics of these constituents are summarized in the context of thermodynamic mass balance and kinetic considerations experimentally determined release rate constants were used to predict the proportions of ca na and k released by feldspars of plutonic rocks granites to gabbros to weathering solutions the chemical weathering trends of the weathered residues calculated from the kinetic data conform closely to the initial trends observed in some recent weathering profiles demonstrating the accuracy of the predictions since the weathering of feldspars is controlled by processes that should not change through geological time the relative release rates of ca na and k from the feldspars of granitic rocks can be calculated for future and past episodes of continental weathering experimentally determined release rate constants are not available for a wide range of volcanic glass compositions but the limited data indicate that compositional trends are predictable in weathering profiles developed on volcanic rocks the kinetic data available for rhyolitic glasses accurately predict the initial weathering trends observed in a recent rhyolite weathering profile

the magma ocean concept and lunar evolution the model of lunar evolution in which the anorthositic plagioclase rich oldest crust of the moon is formed over a period of 300 myr or less by crystallization as it floats on a global ocean of magma tens or hundreds of km thick is examined in a review of petrological and theoretical studies consideration is given to the classification of lunar rocks the evidence for primordial deep global differentiation constraints on the depth of the molten zone the effects of pressure on mineral stability relationships mainly liquid vs mainly magmifer ocean models and the evidence for multiple ancient differentiation episodes a synthesis of the model of primordial differentiation and its aftereffects is presented and the generalization of the model to the earth and to mars mercury venus and the asteroids is discussed

heat focussing granite genesis and inverted metamorphic gradients in continental collision zones abstract the thermal conductivity of sedimentary rocks is usually much lower than that of crystalline rocks gneisses and granites continental collision zones are characterized by large scale thrusts which superpose crystalline basement and sedimentary layers this leads to heat refraction effects of significant magnitude sedimentary layers act as a barrier to the transport of heat we show that the peculiar geometry of a gently sloping sedimentary layer thrust into more conductive rocks is very efficient in diverting the vertical flux of heat temperatures can vary by more than 50 along the horizontal and reach a marked maximum at the top of crystalline layers these results are in general agreement with the main features of orogenic belts as exemplified by the himalayas they explain why the young leucogranites of the main central thrust mct are confined to a narrow belt at the top of the basement slab they also account for the inverted metamorphic gradient observed there in a crustal accretionary wedge folding and thrusting modify the structure of the upper crust by thickening the sedimentary cover and by introducing sedimentary rocks at depth this leads to high temperatures at shallow depths in specific places les zones de collision continentale se caracterisent par de grands chevauchementsafaible pendage qui empilent les unes sur les autres des couches de socle cristallin et des couches sedimentaires cette structure particuliere engendre d importants effets de refraction thermique en effet leur conductibilitethermiqueetant normalement bien plus faible que celle des roches cristallines les formations sedimentaires font office de barrieres pour le transfert thermique le flux de chaleur se trouve fortement devie dans un plan horizontal la temperature peut varier de plus de 50 les maximaetant situesal interface superieur des dalles cristallines en ces endroits precis les isothermes profonds remontent tres significativement ces resultats rendent bien compte de plusieurs faits essentiels observes dans l himalaya zoneographie inverse du metamorphisme localisation des leucogranites le long d une bandeetroite situee au sommet de la dalle du tibet

geochemical records of qionghai lake sediments in southwestern china linked to late quaternary climate changes abstract knowledge of the chemical weathering history under the subtropical monsoonal climate will help to resolve the discrepancies regarding how climate conditions constrain chemical weathering major element and rare earth element ree compositions of the qionghai lake sediments in sichuan province southwestern china were analyzed aiming to provide information on sediment source discrimination and history of chemical weathering intensities and its responses to variations of indian summer monsoon ism and paleoclimate conditions as revealed by the a cn k diagram and other provenance proxies including tio2 zr ratio th sc vs zr sc and la th vs hf diagrams as well as the ree characteristics the source of qionghai lake sediments was felsic rocks additionally these sediments were subjected to small changes in provenance sedimentary sorting and recycling and weak diagenesis after deposition and or metasomatism indicating original signals were maintained on the intensity of chemical weathering of source area the chemical weathering intensities inferred from cia chemical index of alteration values have significantly fluctuated over the past 28 kyr reflecting three stages of paleoclimate evolution which is consistent with grain size characteristics carbonate contents low frequency magnetic susceptibilities toc and biomarker proxy paq the cia values changed significantly during the typical warm and cold climate events including the last glacial maximum heinrich 1 cold event younger dryas and holocene climatic optimum and generally exhibited an increasing trend in amplitude correspondingly in concert with the climate shifting from cold and dry to warm and humid conditions generally warm and humid climate conditions suggest enhanced chemical weathering intensity whereas weak chemical weathering denotes cold and dry climate in the ism region in addition sequential variations of the cia values during the past 28 kyr may reflect changing chemical weathering processes in responses to the varying intensities of indian summer monsoon and the climate conditions forced by the northern hemisphere solar insolation

lunar and terrestrial crusts a constrast in origin and evolution abstract planetary crusts differing in composition from that of the bulk planet and containing large concentrations of incompatible elements such as k u and th may arise in two distinctly different ways the first exemplified by the moon involves flotation of a feldspathic crust during an initial melting episode in which much of the planetary body was molten the second probably more common type of crust is formed as a consequence of partial melting in response to radioactive heating in the planetary interior and the eruption of basaltic lavas examples include the lunar maria and the oceanic crust of the earth subsequent partial melting episodes involving recycling into the mantle or lower crustal melting episodes produce more acidic crusts of which the terrestrial continental crust forms the type example the upper crust requires at least three successive partial melting events

a model for continental crust genesis by arc accretion rare earth element evidence from the irish caledonides abstract the formation of continental crust is a complex problem with a paradox at its center continental material is believed to form by arc magmatism a model that does not reconcile the bulk mafic and light rare earth element lree depleted composition of intra oceanic arcs with the andesitic lree enriched composition of continents we present evidence supporting an arc origin for continental crust by demonstrating significant changes in magmatic chemistry during arc continent collision we use as an example the connemara region of the western irish caledonides where metamorphism and orogenesis of dalradian sedimentary sequences record the collision of the oceanic lough nafooey arc with the passive margin of laurentia at 475 ma arenig this arc was mafic and lree depleted during its oceanic activity during collision rhyolites more lree enriched than the surrounding continental crust were erupted while the mid crust was intruded by similarly lree enriched gabbro and diorite crystal fractionation caused lree enrichment to exceed that expected by assimilation of continental crust alone we propose that subsequent loss of the corresponding lower crustal cumulates into the mantle removed this lree depleted material from the net crust added to the continent the combined processes of crystal fractionation and lower crustal loss during arc continent collision drive the average bulk arc composition toward that of average continental crust

origins of stratiform and stratabound fe cu zn horizons in the lower proterozoic moran lake group labrador central mineral belt zn cu and fe are concentrated as stratiform and stratabound sulphide rich beds in the lower proterozoic warren creek formation moran lake group central labrador upper member sedimentary rocks have a hydrothermal like fe enrichment but a dominantly hydrogenous signature as indicated by high al2o3 relative to sio2 and high al and fe relative to mn the upper member shales and sulphide rich beds were deposited as fe rich pelagic sediments the paucity of mn and abundance of fe in typical shale samples and lack of cu pb and zn fractionation in stratiform massive sulphide beds that contain up to 4702 ppm zn 533 ppm cu and 15 ppm pb suggest that deposition occurred in restricted brine pools i e cu and zn were precipitated rapidly and were not fractionated stratabound sphalerite mineralization containing 3 7 zn and 121 ppm cu but no pb was deposited in a porous lithology at the top of the warren creek formation and represents a unique style of metal concentration the stratiform deposits proba

the howiesons poort and msa iii at klasies river main site cave 1a we present the results of a technological analysis of the howiesons poort and msa iii lithic artifacts from cave 1a at klasies river we studied most of the debitage and retouched pieces from deacon s excavations about 3000 pieces and all the cores and retouched pieces from three layers of singer and wymer excavations 640 pieces our analysis shows 1 that hp blade production was based on the use of marginal percussion by soft stone hammer as at rose cottage 2 that impact scars at klasies rose cottage and sibudu indicate that the backed pieces were hafted in two differentways and 3 that the hp backed pieces were an innovativeway of hafting spear tips but are not clear evidence of the invention of bows and arrows we document the gradual evolution of debitage techniques within the hp sequence with progressive abandonment of the hp technological style very similar trends occur in the upper part of the hp sequence at rose cottage the similarity in temporal trends between sites separated by more than 600 km has significant implications for the disappearance of the hp industry we suggest that the disappearance of the hp was not due to a phenomenon of population contraction and isolation that caused the collapse of social networks the internal evolution and parallel process of change documented at klasies and rose cottage speak against a collapse of social systems and are associated with evidence of environmental and subsistence changes at the transition mis 4 3

mafic and ultrapotassic rocks from the canyon domain central grenville province geochemistry and tectonic implications the canyon domain and the banded complex in the manicouagan area of the grenville province preserve a re cord of magmatic activity from 1 4 to 1 ga this study focuses on 1 4 1 2 ga mafic rocks and 1 ga ultrapotassic dykes geochemistry and sm nd isotopic signatures were used to constrain the origin of these rocks and evaluate the changing role of the mantle with time and tectonic setting from the late evolution of the laurentian margin to the grenvillian orogeny in the manicouagan area the mafic rocks include layers inferred to represent flows homogeneous bodies in mafic migma tite and deformed dykes all of which were recrystallized under granulite facies conditions during the grenvillian orogeny in spite of the complexities inherent in these deformed and metamorphosed mafic rocks we were able to recognize suites with distinctive geochemical and isotopic signatures integration of this data along with available ages is consistent with a 1 4 ga continental arc cut by 1 2 ga non arc basalts derived from depleted asthenospheric mantle with varied degrees of crustal contamination and inferred to represent magmatism in an extensional environment the 1 ga ultrapotassic dykes postdate the grenvillian metamorphism they are extremely enriched in incompatible elements have negative nb anomalies relatively unradiogenic sr isotopic compositions initial 87 sr 86 sr 0 7040 and nd 3t o 15 some dykes have composi tional characteristics consistent with derivation from the mantle ruling out crustal contamination as a major process in their petrogenesis the most likely source region for the ultrapotassic dykes is a metasomatized subcontinental lithospheric man tle with thermal input from the asthenosphere in association with post orogenic delamination

genesis of granitoid batholiths of peninsular malaysia and implications for models of crustal evolution evidence from a ndsr isotopic and upb zircon study nd sr and u pb isotopic data for the late triassic west coast province batholiths and permian to triassic east coast province batholiths of peninsular malaysia allow estimates of the ages of the crustal fragments comprising the peninsula to be made initial nd and sr values for granitoids from the west coast province range from 6 to 10 and 160 0 716 to 660 0 751 respectively nd model ages calculated based on a depleted mantle evolution model tdmnd range from 1300 ma to 1800 ma and are in general agreement with the mid proterozoic upper intersection ages of u pb zircon reverse discordia 1500 1700 ma initial nd and sr values for granitoids from the east coast province range from 0 8 to 6 and 10 0 705 to 130 0 714 respectively calculated tdmnd ages of 900 1400 ma for these granitoids are comparable to two u pb zircon reverse discordia intercepts that yield 800 ma and 1350 ma the general agreement of u pb zircon inheritance ages and tdmnd ages are interpreted to correspond to the proterozoic crust formation ages of the continental fragments represented by the west coast and east coast batholithic provinces mid proterozoic 1300 1900 ma crust formation ages are commonly shown by other phanerozoic continental margin plutonic and volcanic belts the ubiquitous mid proterozoic crust formation ages and the absence of archaean signatures suggest voluminous juvenile additions to the continental crust in the mid proterozoic such ages at continental margins would imply that many continental blocks had achieved very much their present day extent by the mid proterozoic

polymetallic mineralization at the browns deposit rum jungle mineral field northern territory australia the rum jungle mineral field northern territory australia forms part of the paleoproterozoic pine creek orogen the geology of the area comprises two archean granitic basement domes overlain by a paleoproterozoic sequence of metasedimentary and subordinate metavolcanic rocks the rocks have been deformed and metamorphosed to greenschist facies during the 1880 ma barramundi orogeny but the original stratigraphic succession has been preserved the browns deposit browns and its extension browns east hosted within black carbonaceous pelites of the paleoproterozoic whites formation is the largest base metal deposit found to date in the pine creek orogen present resource estimates are 39 million metric tons mt at 0 44 percent cu 3 61 percent pb 0 11 percent co and 0 09 percent ni browns and 31 mt at 1 29 percent cu 1 28 percent pb 0 13 percent co and 0 13 percent ni browns east major sulfide minerals in the ore zone are galena sphalerite chalcopyrite pyrite and the main carrier of ni and co siegenite ni co 3 s 4 digenite group minerals and bornite ca bearing plumbogummite pbal 3 po 4 2 oh 5 h 2 o arsenopyrite and gersdorffite are present in minor quantities ore minerals occur as fine grained wisps parallel to the main bedding parallel foliation and as coarse grained mono and polyminerallic aggregates that crosscut the foliation total noncarbonate carbon contents of unaltered rocks range from 1 07 to 7 51 wt percent total sulfur contents range from 2 13 to 6 14 wt percent petrographic studies and raman spectroscopy identify three varieties of carbonaceous matter primary syngenetic premetamorphic epigenetic grain coating and postmetamorphic epigenetic uraniferous migrated altered rocks are rarely encountered values of 34 s for sulfides range from 5 to 15 per mil and are interpreted to reflect a combination of inorganic thermochemical reduction of seawater and bacterial activity no specific sulfur isotope patterns for individual minerals can be established indicating nonequilibrium conditions homogeneous lead isotope signatures of galena 206 pb 204 pb 16 20 16 22 207 pb 206 pb 15 48 15 51 208 pb 207 pb 35 86 35 92 suggest that all pb was derived from a single crustal source and paragenetically late crosscutting galena appears to have been remobilized from bedding parallel galena despite the occurrence of uranium in similar rocks nearby uranium is quantitatively insignificant in the browns deposit and is not genetically related to base metal mineralization instead it is linked to brittle deformation in the waning stages of orogenesis the browns deposit differs from other well known sediment hosted stratiform ore deposits both the zambian copperbelt and the polish kupferschiefer deposits are copper dominant and hosted in sedimentary sequences with significant psammitic components the pb zn ag deposits of the proterozoic australian zinc province also have significant carbonate in their host rocks e g carbonaceous dolomitic and siltstone at mcarthur river and lack economically interesting cu co and ni the nearby woodcutters pb zn ag deposit in rocks of similar age also differs in structural setting veins dominant metals and pb isotopes from the browns deposit

early use of pressure flaking on lithic artifacts at blombos cave south africa pressure flaking has been considered to be an upper paleolithic innovation dating to 20 000 years ago 20 ka replication experiments show that pressure flaking best explains the morphology of lithic artifacts recovered from the 75 ka middle stone age levels at blombos cave south africa the technique was used during the final shaping of still bay bifacial points made on heat treated silcrete application of this innovative technique allowed for a high degree of control during the detachment of individual flakes resulting in thinner narrower and sharper tips on bifacial points this technology may have been first invented and used sporadically in africa before its later widespread adoption

klipdrift shelter southern cape south africa preliminary report on the howiesons poort layers abstract surveys for archaeological sites in the de hoop nature reserve southern cape south africa resulted in the discovery of a cave complex comprising two locations klipdrift cave and klipdrift shelter excavations commenced in 2010 with later stone age deposits initially being recovered at the former site and middle stone age deposits at the latter the lithic component at klipdrift shelter is consistent with the howiesons poort a technological complex recorded at a number of archaeological sites in southern africa the age for these deposits at klipdrift shelter obtained by single grain optically stimulated luminescence spans the period 65 5 4 8 ka to 59 4 4 6 ka controlled and accurate excavations of the discrete layers have resulted in the recovery of a hominin molar marine shells terrestrial fauna floral remains organic materials hearths lithics ochre and ostrich eggshell more than 95 pieces of the latter distributed across the layers are engraved with diverse abstract patterns the preliminary results from klipdrift shelter presented in this report provide new insights into the howiesons poort in this sub region and contribute further to ongoing knowledge about the complex behaviours of early homo sapiens in southern africa excavations at the klipdrift complex will continue in the future

quantifying rates of methanogenesis and methanotrophy in lake kinneret sediments israel using pore water profiles full seasonal sets of chemical and isotope profiles from the pore water of lake kinneret sea of galilee israel were produced to study methanogenesis and methanotrophy processes and the couplings between methane ch4 sulfur and iron sulfate is depleted within the upper 10 cm of the sediment mainly by traditional bacterial sulfate reduction by organic matter maximum sulfate reduction rates calculated from sulfate concentration profiles are found at the water sediment interface 0 1 cm 2 1 4 3 10212 6 0 2 3 10212 mol cm23 s21 ch4 concentrations and modeling of dissolved inorganic carbon dic and its stable carbon isotope d13cdic suggest that maximum methanogenesis rates of 2 5 3 10213 6 1 5 3 10213 mol cm23 s21 occur at 5 12 cm depth in the sediments and that it ends at 20 cm of the produced ch4 50 75 is converted to gas bubbles of ch4 before it reaches the bottom water model results suggest the occurrence of anaerobic oxidation of ch4 aom in the deep sediments of the lake below the zone of methanogenesis methane ch4 is an important greenhouse gas with emissions from anthropogenic and natural sources roughly estimated to be around 350 and 120 tg c yr 21 tg 2 1 3 1012 g respectively wuebbles and hayhoe 2002 among the natural sources continental emissions contribute more than 70 wuebbles and hayhoe 2002 however the parameters controlling these emissions are not well understood therefore it is essential to resolve the rate of the processes behind ch4 emissions from continental systems this study aims at this objective investigating lacustrine environment using a geochemical approach ch4 in its natural sources is produced mainly through microbial processes methanogenesis chemical profiles in pore water of organic rich sediments indicate that various microbes use a series of electron acceptors during the remineralization of organic matter in the order of decreasing chemical potential and methanogenesis accounts for the last stage of the microbial respiration in stratified lakes developing an anoxic hypolimnion methanogenesis and sulfate reduction are key terminal

the influence of sediment recycling and basement composition on evolution of mudrock chemistry in the southwestern united states this paper reports systematic changes in mudrock composition through time on a single con tinental cmstal block the changes reflect both sediment recycling processes and changes through time in the composition of crystalline material being added to the sedimentary system and are related to tectonic evolution as the block matures from a series of accreted arc terranes to a stable craton the major and trace element distributions reflect different aspects of the provenance of the mudrocks in this study major elements record sediment recycling processes as well as changing proportions of sedi mentary and first cycle source rocks with the exceptions of kzo which tends to increase and sioz and a o3 which show no trend most major oxides tend to decline in relative abundance in younger mud rocks patterns shown by the index of compositional variability fe03 kro naao cao mgo mno tiojialro and by k20 a1203 indicate that the major oxide trends are due to decreasing proportions of nonclay silicate minerals and a concomitant increase in the proportion of clay minerals probably due to decreasing input of first cycle detritus coupled with recycling of sedimentary material excursions from progressive trends marked by increases in mgo k20 and cao reflect episodes of large scale input of nonclay first cycle minerals from crystalline source rocks due to large scale basement uplift the chemistry of low solubility trace elements in contrast is not sensitive to recycling effects and reflects the composition of first cycle input incompatible elements are progressively enriched relative to compatible elements in younger mudrocks and values for chondrite normalised rare earth elements also increase in addition the eu anomaly becomes systematically more negative in younger samples these trends cmnot be explained by diagenetic or weathering processes and therefore indicate that the proportion of fnc tionated granitic first cycle detritus being added to the sedimentary system becomes greater with time these results confirm the importance of tectonic setting in controlling mudrock chemistry and also demonstrate that there is a dynamic relationship between the tectonic evolution of a continental block and the composition of its sedimentary mantle

uranium thorium systematics of two canadian coals abstract a detailed study of u th distribution in two lower cretaceous coals in canada shows that for these coals formed in a continental fluvial and deltaic environment with no marine influence the u contents are in the range 0 07 7 5 ppm with th in the range 0 3 11 0 ppm average th u ratios are near 2 which indicates slight uranium enrichment the environments of the two coals show different degrees of weathering montmorillonite illite and kaolin gibbsite and u values are lowest in the more weathered environment in sedimentary profiles associated with the coals the maximum uranium values are not in the coals but in carbonaceoss clay sediments above and below coal seams uranium distribution patterns can be correlated cith ni cu rb pb sr and zr indicating contributions from heavy minerals plus more mobile species possibly simple organic compounds which are adsorbed or bonded onto claysor organic matter

the significance of mis 5 shell middens on the cape coast a lithic perspective from klasies river and ysterfontein 1 in this paper lithic assemblages from two mis 5 middens on the cape coast klasies river main site and ysterfontein 1 are compared klasies river on the southern cape coast has provided an abundant sample of stone artefacts from mis 5 the msa 1 and msa 11 techno complexes recent work at ysterfontein site has yielded the largest lithic sample so far of a comparable age from the cape west coast the assemblages from klasies river and ysterfontein 1 represent three clearly discernable techno complexes at klasies river the msa 1 or klasies river techno complex is characterized by a recurrent strategy to produce elongated products this is followed by the msa 11 also termed the mossel bay in which a strategy with unipolar convergent levallois characteristics was followed the msa 1 and msa 11 are different techno complexes even though the products are morphometrically somewhat similar the ysterfontein 1 techno complex differs from the klasies river mis 5 assemblages in terms of in raw material composition technology and dimensions of the flaked products in the ysterfontein 1 techno complex relatively short blades and flakes were produced from platform and two volume cores scrapers notches and denticulates comprise the retouched component of all three assemblages insight into the technological capabilities of mis 5 populations is important to understand subsequent techno complexes such as the still bay and howiesons poort the technical behavior of humans that lived around 100 000 years ago on the cape coast is of more than parochial interest cultural changes in all of africa in mis 5 provide a window into sapient cognitive and adaptive conventions

the joffre banded iron formation hamersley group western australia assessing the palaeoenvironment through detailed petrology and chemostratigraphy abstract the joffre member of the brockman iron formation is by volume the largest single known banded iron formation bif in the world here we present detailed petrology and chemostratigraphy through the entire 355 m core section of this 2 45 billion year old unit oxide bif and silicate carbonate oxide bif dominate the lithology with minor amounts of interbedded stilpnomelane mudrock stilpnomelane rich tuffaceous mudrock and calcareous mudrock besides chert and magnetite the prominent mineralogy is riebeckite ankerite hematite stilpnomelane and crocidolite the bif is characterized by an average of 50 wt sio 2 and 44 5 wt fe 2 o 3 and an overall low abundance of al 2 o 3 2 sn of 0 24 the rey patterns also show a positive la sn anomaly no ce sn anomaly and a weakly developed positive y sn anomaly iron isotopes 56 fe with positive 56 fe values of 0 04 to 1 21 suggest that a large part of the hydrothermal iron was partly oxidized in the upper water column and subsequently precipitated as ferric oxyhydroxides no epiclastic grains have been found rather submarine hydrothermal fluids and fine grained volcanogenic detritus controlled bif chemistry the former source is reflected through a constant positive eu sn anomaly throughout the core average eu sn anomaly of 1 6 with a peak of 2 1 between 100 and 155 m depth while the latter source is best reflected through the stilpnomelane rich tuffaceous mudrock consisting of volcanic ash fall tuff with relict shards set in a stilpnomelane matrix the mudrock is overlain by well preserved wavy laminae and laminae sets of stilpnomelane microgranules that likely originated from re worked volcanic ash formed either on the seafloor or in the water column prior to deposition an enriched hree to lree pattern a high iron content 30 wt and a 56 fe value of 0 59 collectively imply that the mudrock facies interacted with the fe rich seawater prior to deposition the tio 2 zr ratio of the bif and the associated mudrocks suggest a felsic only source related to the same style of volcanics as the slightly younger woongarra rhyolites given the observation that the dominant control on the seawater chemistry was associated with felsic volcanics we speculate that the fine grained pelagic ash particles may have sourced bio available nutrients to the surface water this would have facilitated enhanced biological productivity including bacterial fe ii oxidation which is now recorded as the positively fractionated 56 fe iron oxide minerals in the joffre bif alongside submarine hydrothermal input to the basin the dominant control on the ocean chemistry seems to have been through volcanic and pyroclastic pathways thereby making the joffre bif poorly suited as a chemical proxy for the study of atmospheric oxygen and its weathering impact on local landmasses

lake untersee a first isotope study of the largest freshwater lake in the interior of east antarctica perennially ice covered lakes partially bounded by glacier ice are common in some antarctic coastal regions1 but very rare inside the continent here we describe hydrological studies on the largest freshwater lake of interior antarctica lake untersee 71 20 s 13 30 e surface area 10 km2 maximum depth 79 m 2 showing that the lake arose from a melt water pond during climatic optimum periods in the holocene at present the studied water body is thermally hydrogeochemically and isotopically homogeneous because of thermal convection during the austral summer lake untersee is fed throughout the year by underwater melting of the adjoining glacier ice isotope data suggest a permanent ice cover during its existence the drainless lake is constantly losing water through sublimation on the surface of the more than 2 5 m thick ice cover the salt content suggests that the present water body is the remainder of an amount of melt water at least 50 times as great

the f zone a negative velocity gradient near the inner outer core boundary might be adequately explained by the existence of heat producing elements in the region geochemically there should be about one third to more than a half of the earth s total resources of heat producing elements present below the upper mantle which is also consistent with observations of heat flux at the earth s surface the results of high pressure experiments further suggests that the heat producing elements would exist as dioxides which are chemically incompatible with the major mantle silicates under the temperature and pressure conditions prevailing in the lower mantle the great density of these heat producing dioxides probably greater than the liquid iron nickel core may cause them to be transported to the inner outer core boundary the f zone

geochemical and isotopic disequilibrium in crustal melting an insight from the anatectic granitoids from toledo spain in the hercynian anatectic complex of toledo act the anatectic granitoids include leucogranitic leucosomes leucogranitic massifs and restite rich granites they show a broad range of initial sr and nd isotope ratios from 0 711 to 0 720 and 0 51164 to 0 51203 respectively which clearly indicate the absence of isotopic homogenization in the melts broadly the ranges reflect the isotopic variation of the metapelitic protoliths if crustal melting occurs under water undersaturated conditions as is the case of the act the generated melts do not isotopically and chemically equilibrate with the granulitic residuum the preservation of heterogeneities could arise through a number of processes 1 duration of the process in which the presence of melts with disequilibrium features and the high solid content of several of the granites in the act point to a very short lived magmatic system 2 limited diffusion in which poorly segregated and volatile undersaturated granitoids have a very restricted opportunity for isotopic and chemical homogenization and 3 magma dynamics in which the low melting rates the high restite and low water contents and the silica rich composition of these granites together with the small volume and high viscosity values of the melts seriously restrict the physical processes leading to homogenization

putslaagte 1 pl1 the doring river and the later middle stone age in southern africa s winter rainfall zone abstract existing data suggest weak human occupation of southern africa s winter rainfall zone wrz during later marine isotope stage mis 3 the causes of which are unknown here we report briefly on the results of recent surveys of alluvial terrace sites of the doring river in the wrz which document occupation over a broad expanse of the later middle stone age msa and pleistocene later stone age we then report on test excavations at one terrace site denoted putslaagte site 1 pl1 describe in detail the assemblage of flaked stone artefacts produced from that excavation and present two osl ages obtained from 0 8 m to 1 5 m below surface the results suggest that a artefact accumulations at pl1 are dense b the technological systems documented are characteristically msa but differ in form from the range of systems known from other excavated sites in the region and c that the assemblages accumulated in mis 3 taken together with the survey data the results introduce new variation into the later msa in southern africa and imply reorganisation of land use in the wrz in late mis 3 rather than abandonment we suggest that a research emphasis on rock shelter deposits may have produced misleading depictions of regional occupation

geochemistry of high ph waters from serpentinites of the gruppo di voltri genova italy and reaction path modeling of co2 sequestration in serpentinite aquifers abstract the large number of geochemical data gathered on the gruppo di voltri springs confirm that progressive interaction of meteoric waters with ultramafic rocks variably affected by serpentinization leads initially to the formation of mg hco3 waters when the system is open to co2 and na hco3 and ca oh type water upon further interaction with the rock under highly reducing closed system conditions with respect to co2 as indicated by 3h data these high ph waters have had long residence times underground in deep aquifers hosted by serpentinitic rocks these waters are the only available evidence of the presence of such deep aquifers high pressure injection of co2 into these deep aquifers was simulated by reaction path modeling results indicate that this is a feasible methodology to reduce the inputs of anthropogenic co2 into the atmosphere serpentinitic rocks have a high capacity for co2 sequestration mainly through formation of carbonate minerals dissolution of serpentinitic rocks and precipitation of magnesite and silica minerals occurs naturally in areas of high terrestrial co2 fluxes such as in southern tuscany corroborating the feasibility of this methodology of co2 sequestration however this process causes a progressive decrease in the porosity of the aquifer at least under closed system conditions these side effects must be carefully evaluated by means of further laboratory tests and field activities

origin and formation of methane in groundwater of glacial origin from the cambrian vendian aquifer system in estonia abstract groundwater in the cambrian vendian aquifer system in estonia is characterised by the most depleted isotopic composition known in europe 18o down to 23 the water most likely originates from glacial meltwater recharge from the fennoscandian ice sheet in the pleistocene the aquifer system is characterised by relative high methane concentrations up to 50 of dissolved gases estimated absolute concentration up to 1600 mol l 1 the origin of which has so far remained unclear in this paper we focus on the origin of methane the factors controlling its spatial distribution and its isotope geochemistry in the aquifer system the data reveal a large spatial variability in methane concentration 13cch4 and 2hch4 values from 6 to 105 and from 220 to 420 respectively we show that local oxidation processes rather than different pathways of methane formation have affected the initial isotopic composition of methane using the least modified 13cch4 values from 85 to 105 we conclude that methane most likely originates from the organic material overridden by the fennoscandian ice shield during the late weichselian glaciation that was carried into the aquifer system with infiltrating glacial meltwater the estimated 18o values of the water where the methane was formed are 17 1 5 supporting the inference that the methane was formed during the middle weichselian interstadial the study shows that groundwater of glacial origin in the cambrian vendian aquifer system can serve as an alternative palaeoenvironmental archive to be used for studying the variations in climatic and environmental conditions in northern europe during glacial interglacial cycles of the pleistocene

metamorphic response and crustal architecture in a classic collisional orogen the damara belt namibia abstract the damara belt is a well exposed mid crustal section through a collisional orogen of cambrian age that closed the khomas ocean basin between passive margins on the congo and kalahari cratons collision resulted in a bi vergent orogen with a distinct paired metamorphic pattern of foreland vergent high p low t orogenic margins and a broad high grade low p high t orogen core spatial and temporal patterns of the metamorphic response to collision have been characterized for all parts of the belt using a large dataset n 240 of internally consistent quantitative pt determinations evolution of mineral parageneses and semi quantitative p t paths metamorphic mapping and quantitative metamorphic field gradients integration with deformation history structural profiles metamorphic chronology magmatic history and stratigraphy constrains a dynamic model of crustal architecture during peak metamorphic events the pattern of zonal metamorphic response is demarcated by three major metamorphic discontinuities md with steep pressure gradients inferring crustal scale structures that accommodated lateral exhumation of crustal wedges discontinuities are confirmed by deformation features in the field and metamorphic mineral growth indicates that vertical flattening at the peak of metamorphism progressing through ductile to brittle extensional structures crustal wedges along the orogenic margins experienced steep clockwise p t paths with peak pt conditions terminated by isothermal decompression during rapid exhumation in isostatic response to deep burial metamorphic chronology and over printing metamorphic fabrics constrain a sequence of foreland propagating out wedging of crustal thrust wedges that resulted in telescoping of the orogenic margins peak metamorphism at a geothermal gradient of 20 25 c km and 8 9 kb in the southern zone wedge i was attained between 517 530 ma followed by south directed out wedging at the uis pass suture accommodated by relative extension md1 at high structural levels near the boundary with the high grade orogen core out wedging of the southern zone further buried the southern margin zone wedge ii in the footwall below the uis pass suture peak metamorphism at 17 c km and 9 5 11 5 kb in the southern margin zone was attained at 517 4 ma and followed by out wedging on basal thrusts accommodated by vertical flattening and extensional reactivation of the uis pass suture md2 peak metamorphism at 17 c km and 10 5 kb in a high p low t crustal wedge in the northern margin wedge iii occurred at 510 4 ma peak metamorphism in this wedge was terminated by isothermal decompression during north directed thrusting accommodated by extension at higher structural levels near the high grade orogen core md3 granulite facies metamorphism in the high grade orogen core which formed the upper plate to the deeper thrust wedges occurred at significantly lower pressures 4 3 6 0 kb higher t depth ratios 38 47 c km and low p t clockwise p t paths indicating only moderate burial and protracted high grade conditions metamorphic chronology confirms high grade conditions 540 505 ma persisted beyond isostatic adjustment of the high p low t orogenic margins high heat flow conditions and long thermal lag are best explained by lithospheric breakoff during collision in contrast to the high p low t margins that experienced lateral exhumation in a convergent system the high grade orogen core was exhumed vertically as a broad core complex during extensional collapse of the orogen peak metamorphic conditions in the central part of the orogen core record higher pressures than marginal lower grade zones to both the north and south indicating vertical exhumation as a broad massif this post peak vertical exhumation of the central core occurred after 505 ma was accommodated by brittle extensional detachments at high stratigraphic levels with km scale omission of crustal section

blombos cave southern cape south africa preliminary report on the 1992 1999 excavations of the middle stone age levels the later and middle stone age levels at blombos cave bbc were excavated over four field seasons between 1992 and 1999 here we report on the results from the middle stone age msa levels the taphonomy and depositional history of the msa levels is complex due to faulting folding and spalling careful observations during excavation have assisted in understanding some of these taphonomic and site formation processes microstratigraphic analysis currently in progress will add to this information the uppermost msa level the still bay phase contains high densities of bifacial points the fossile directeur of the still bay industry placing the still bay within the msa culture sequence has been problematic in the past because still bay assemblages are rarely found in situ and previous excavations were inadequately recorded however with the regional data discussed in the text the still bay can be securely placed before the howiesons poort dated at 65 70 ka flaked stone makes up the greatest proportion of all artefacts with the highest incidence of retouch and use of fine grained non local materials found in the still bay levels the ochre assemblage is remarkable for the mass of material compared to other msa sites finds uncommon in an msa context are two pieces of ochre from the still bay phase engraved with a geometric design a fragment of deliberately engraved bone also 28 shaped and polished bone tools recovered mainly from a phase just below the still bay blombos cave is the first site where well preserved faunal remains have been recovered in association with the still bay allowing for unique insights into human subsistence behaviour and palaeoenvironmental reconstruction large fish bones marine shells seals and dolphins attest to extensive exploitation of aquatic resources and a wide range of terrestrial animals were hunted and gathered the few human teeth recovered are heavily worn and damaged thus the issue of morphological modernity cannot be addressed the bbc findings are a useful adjunct to findings from other msa coastal sites in the southern cape especially klasies river kr and die kelders cave 1 dk1 uniquely bbc provides insights into human behaviour during a phase of the msa never before studied in detail

rare earth elements as reactive tracers of biogeochemical weathering in forested rhyolitic terrain article rareearthelements rees were evaluatedaspotentialtracers of biogeochemicalweathering atpedon hillslope and catchment scales in the jemez river basin critical zone observatory jrb czo valles caldera national pre serve nm usa we investigated time series of ree patterns in precipitation soil pore water groundwater and stream water and related these data to ree composition of soil rock and atmospheric dust ree signatures in stream waters are dynamic reflecting processes that occur along hydrologic flowpaths during transport to the stream including organic matter complexation primary and secondary mineral weathering water soil bedrock interaction and atmospheric deposition strong compositional similarities for the ree between soil waters and stream waters during the initial snowmelt are consistent with shallow subsurface flows to streams most bio

origin of granites in an archean high grade terrane southern india archean deep level granites in southern india are similar geochemically to young granites from continentalmargin arc systems they exhibit light ree enriched patterns with variable but chiefly positive eu anomalies this is in striking contrast to the negative eu anomalies typical in high level archean granites in addition the deep level granites are relatively enriched in ba and sr and depleted in total ree and high field strength elements hfse one pluton the sankari granite has unusually low contents of ree and hfse most of the deep level granites appear to represent cumulates with variable amounts of trapped liquid and of minor phases resulting from fractional crystallization of a granitic parent such parental granitic magmas can be produced by batch melting of archean tonalite at middle to lower crustal depths the sankari granite requires a tonalitic source depleted in ree and hfse archean tonalites and tonalitic charnockites exhibit original igneous geochemical signatures and their average composition does not show a significant eu anomaly hence they cannot represent the positive eu anomaly complement to the negative eu anomaly high level granites our results suggest that archean deep level granites may represent this complement such granite may form in waterrich zones in the middle or lower crust and be produced in response to dehydration of the lower crust by a rising co2 rich fluid phase

biogeochemistry of methane in the permanently ice covered lake untersee central dronning maud land east antarctica we found unprecedentedly high abundances of microbially produced ch4 in the anoxic deep waters of lake untersee an oligotrophic perennially ice covered antarctic freshwater lake the maximum ch4 concentration approaching 21 8 6 1 4 mmol l 21 is one of the highest observed so far in a natural aquatic ecosystem although surficial lake sediments are the predominant source of ch 4 in lake untersee methanogenesis occurs also within the anoxic waters radiocarbon labeling experiments show that h2 co2 reduction is the predominant methanogenic pathway 90 100 both in the sediments and the water column whereas acetate is only a minor ch 4 precursor this result is consistent with the stable carbon isotope fractionation between coexisting ch 4 and co2 in the water column ch4 is partly consumed by both aerobic and anaerobic microbial oxidation as evidenced by ch4 concentration patterns stable isotope analyses 13

technological successions in the middle stone age sequence of diepkloof rock shelter western cape south africa the southern african msa comprises a series of phases of unique technological innovations that fuel current models on the evolutionary processes of anatomically modern humans however the nature and variability of these technological phases remain poorly documented this study reports on the previously unpublished sequence of diepkloof rock shelter south africa and investigates the main technological changes therein particularly emphasizing the emergence succession and disappearance of the still bay sb and the howiesons poort hp we argue for technological change that occurred at different rates and under the influence of variable driving factors our model implies that the sb and the hp are not related to the influx of new populations but have regionally specific origins unlike the other techno complexes the hp at diepkloof is subdivided into different phases early intermediate and late but only the upper phases resemble the so called classic hp finally the technological sequence of diepkloof questions the homogeneous picture which has been so far assumed for the southern african msa and places emphasis on the importance of exploring long regional sequences

impact glasses from zhamanshin crater u s s r chemical composition and discussion of origin three silica rich zhamanshinites and one irghizite from the zhamanshin impact crater northern aral area u s s r have been analyzed for up to 40 major minor and trace elements all data point to a clear distinction between these impact glasses and other tektites or impact glasses e g from the australasian strewn field halogens are generally enriched in the irghizites and zhamanshinites when compared to normal splash for tektites with zhamanshinites enriched more than irghizites the same holds also for the alkali metals and a number of other volatile elements like sb and as nickel and cobalt are enriched in the irghizite sample to a considerable degree suggesting meteoritic contamination this view is also supported by gold and selenium data but for quantifications other siderophile elements need to be considered chromium is not a valid indicator of meteoritic contamination because smallamounts of ultra basic igneous material may completely alter the picture the rare earth elements do show a sedimentary pattern consistent with two or three different source materials and a variation which is probably mostly due to dilution with silica rich materials the peak pressure and temperature experienced by the irghizites was lower than for australites or other splash form tektites and even lower for zhamanshinites which is revealed by the content of volatile elements and lesser homogeneity

variability in the middle stone age lithic sequence 115 000 60 000 years ago at klasies river south africa abstract stratified samples of artefacts from the late pleistocene deposit at the klasies river main site covering some 60 000 years have been studied variability in the artefact sequence has been documented in the technologies of artefact production in addition to conventional typological analysis particular emphasis has been given to the recognition of the reduction sequences used in producing the pre formed blanks that are a feature of the middle stone age the results show that the variability is due to changes between the dominant blade and or point technological conventions traditions through time technological study supports and gives meaning to the recognition of distinct sub stages msa i klasies river msa ii mossel bay howiesons poort and a post howiesons poort at main site these sub stages are more than convenient site specific organizational entities they delineate separate technological conventions that may have relevance on a sub continental scale

tectonic environment of the devonian gramscatho basin south cornwall framework mode and geochemical evidence from turbiditic sandstones the portscatho formation within the allochthonous unit of the middle and upper devonian gramscatho group is a thick sequence of deep water sandstones and interbedded slates deposited by southerly derived turbidity currents into the gramscatho basin of south cornwall throughout an approximately 3 5 km thick sequence the portscatho formation is petrographically and chemically coherent except that the upper section shows a higher proportion of metamorphic clasts high but variable cr and low uniform zr abundances complementary framework mode and bulk geochemistry indicate that the sandstones were derived from a dissected continental magmatic arc of predominantly acidic composition similar to average upper continental crust but with an admixture of minor intermediate basic material flysch deposition took place in a fore arc setting the presence of an arc to the south of cornwall during the devonian implies that there was subduction at the margin of the gramscatho basin whose ultimate closure was accommodated by the northward stacking of flysch ophiolite nappes

osl and tl dating of the middle stone age sequence at diepkloof rock shelter south africa a clarification diepkloof rock shelter offers an exceptional opportunity to study the onset and evolution of both still bay sb and howiesons poort hp techno complexes however previous age estimates based on luminescence dating of burnt quartzites tribolo et al 2009 and of sediments jacobs et al 2008 were not in agreement here we present new luminescence ages for 17 rock samples equivalent dose estimated with a sar itl protocol instead of classical maad tl as well as for 5 sediment samples equivalent dose estimated with sar single grain osl protocol and an update of the 22 previous age estimates for burnt lithics modified calibration and beta dose estimates while a good agreement between the rock and sediment ages is obtained these estimates are still significantly older than those reported by jacobs et al 2008 after our own analyses of the sediment from diepkloof it is suspected that these authors did not correctly chose the parameters for the equivalent dose determination leading to an underestimate of the equivalent doses and thus of the ages from bottom to top the mean ages are 100 10 ka for stratigraphic unit su noel and 107 11 ka for su mark uncharacterized lower msa 100 10 ka for su lynn leo pre sb type lynn 109 10 ka for sus kim larry sb 105 10 ka for sus kerry kate and 109 10 ka for su jess early hp 89 8 ka for su jude msa type jack 77 8 ka for su john 85 9 ka for su fox 83 8 ka for su fred and 65 8 ka for su ob5 intermediate hp 52 5 ka for sus ob2 4 late hp this chronology together with the technological analyses greatly modifies the current chrono cultural model regarding the sb and the hp and has important archaeological implications indeed sb and hp no longer appear as short lived techno complexes with synchronous appearances for each and restricted to oxygen isotopic stage ois 4 across south africa as suggested by jacobs et al 2008 2012 rather the sequence of diepkloof supports a long chronology model with an early appearance of both sb and hp in the first half of ois 5 and a long duration of the hp into ois 3 these new dates imply that different technological traditions coexisted during ois 5 and 4 in southern africa and that sb and hp can no longer be considered as horizon markers

mantle derived archaean monozodiorites and trachyandesites the 2 680 2 750 myr old1 5 intrusive granite greenstone terranes6 8 in the rainy lake region ontario and in and adjacent to the vermilion district minnesota of the superior province in north america include a wide variety of volcanic and intrusive rocks with initial pb sr and nd isotope ratios close to those for the mantle4 5 9 12 the isotopic constraints require the production of large volumes of silica oversaturated magmas from silica undersaturated mantle within 100 200 myr we present here geochemical data on monzodiorites and trachyandesites from the rainy lake area which are strongly enriched in large ion lithophile elements lile we conclude that they are derived by direct melting of the mantle at depths of 50km in either anhydrous or hydrous conditions their rare earth element ree abundances and initial 143nd 144nd ratios suggest that their mantle sources were enriched in lile shortly before melting the monzodiorites trachyandesites and their granodioritic derivatives may comprise up to 20 of the exposed igneous rocks in the rainy lake region and vermilion district if these rocks are as abundant in other archaean terranes a significant part of the early continental crust could have formed by direct melting of lile enriched mantle

geochemistry and tectonic significance of the ongarbira metavolcanic rocks singhbhum district india abstract the volcanic sedimentary sequence of ongarbira occurs to the south of the singhbhum shear zone and rests uncomformably on a basement topographic low between the chakradharpur granite and the singhbhum granite structural analysis reveals that the ongarbira synform and other adjoining structures are kilometre scale first generation folds on e w striking axial planes these structures are in marked contrast with the corresponding kilometre scale first generation folds typical of the iron ore group synclinorium towards the south of the ongarbira belt the ongarbira metavolcanic rocks exhibit a limited range of tholeitic basalt compositions the basalts are grouped according to their mg and the details of their ree patterns groups i and ii are relatively unevolved and very similar to lree and lil depleted ocean ridge tholeiites the most evolved group iii with lree enrichment is most similar to lil enriched ocean floor basalts but may be contaminated with crustal materials in general the ongarbira volcanics evolve upward stratigraphically petrogenetic major element modelling of the ongarbira basalts suggests that the primary melt was generated by batch melting 30 of lherzolite at pressures of at least 1 5 gpa sequential fractionation of ol o1 cpx pl and cpx pl followed comparison of incompatible and compatible element distributions indicates a very similar batch m melting fractional crystallization sequence for ongarbira groups i and ii basalts group iii basalts may have been derived from a batch melt initially more enriched in incompatible elements trace element discrimination of the ongarbira basalts suggests that they were generated in an extensional environment primordial mantle normalized element distributions indicate that the basalts are similar to continental rift basalts but with oceanic affinities the chemical data along with the associated sediments indicate that the ongarbira basalts were probably emplaced in a mature continental rift although a back arc origin cannot be completely disregarded it is concluded that the ongarbira volcanics were emplaced as part of the same rifting event that resulted in outpourings of the proterozoic dalma and dhanjori volcanics implying that the ongarbira suite is proterozoic and not part of the archaean iron ore group the structural geometry of the ongarbira rocks is more conformable to that of the singhbhum mobile belt than to the iron ore group synclinorium in the singhbhum craton it is likely that the southern limit of the singhbhum mobile belt is defined by the interface of its e w structures with the nne structures of the iron ore group rocks thus the singhbhum shear zone does not mark the interface between the archaean singhbhum craton and the proterozoic singhbhum mobile belt in the eastern indian shield

the silurian passamaquoddy bay mafic dyke swarm new brunswick petrogenesis and tectonic implications the volcanic and sedimentary rocks of the passamaquoddy bay pb area of southeastern new brunswick are part of the silurian devonian coastal volcanic belt cvb an extensive belt of bimodal volca

geochemical and metallogenic relations in volcanic rocks of the southern slave province implications for late neoarchean tectonics late neoarchean volcanic belts in the southern slave province include 1 in the east the cameron river beaulieu river belts which are characterized by stratigraphically thin flow rich classic calc alkaline arc type sequences with accompanying syngenetic volcanogenic massive sulphide deposits and 2 in the west the yellowknife belt which is characterized by stratigraphically thick structurally complex pyroclastic rich adakitic back arc basin type sequences with accompanying epigenetic lode gold deposits the volcanic belt association bears persuasive chemical evidence of subduction initiated magma generation however the greenstone belts together with coeval matching patterned belts in superior province of the southern canadian shield bear equally persuasive evidence of prevailing autochthonous parautochthonous relations with respect to component stratigraphic parts and to older gneissic basement the eastern and western volcanic belts in question are petrogenetically ascribed to a westerly inclined present geography subduction zone s that produced shallower east to deeper west slab initiated mantle wedge generated parent magmas this early stage microplate tectonic process involved modest mantle subduction depths small tectonic plates and small sialic cratons in the larger context of earth s progressively cooling hence subduction deepening mantle this late neoarchean greenstone belt development 2 73 2 66 ga merged with the massive end archean tonalite trondhjemite granodiorite granite ttgg bloom 2 65 2 55 ga resulting in greatly enhanced craton stability successive subduction deepening plate craton enlarging stages with appropriate metallotectonic response across succeeding proterozoic time and beyond led to modern mode plate tectonics

intracrustal recycling and upper crustal evolution a case study from the pan african damara mobile belt central namibia abstract clastic sediments from the pan african damara mobile belt show a wide range in depositional nd nd 0 18 to 1 and several key trace element ratios notably th nd and la sm increase from 0 2 to 0 7 and 4 0 to 8 0 respectively with decreasing nd 0 such trace element ratio nd 0 data arrays are attributed to binary mixing within the sedimentary mass and the data array defined by the damara sediments is consistent with data from other regions the low nd 0 end member is characterised by high th nd th y la sm and hf zr ratios and reflects highly differentiated upper crust dominated by granitoids pb isotope data suggest that the low nd 0 end member also had relatively high time integrated th u 4 by contrast the high nd 0 end member reflects juvenile upper crust but this end member has la sm th nd and hf zr ratios 4 0 0 2 and 0 02 respectively slightly lower than those of taylor and mclennan s preferred model for bulk crust and significantly lower than those of the andesite model intracrustal differentiation is discussed in terms of bulk crust present day average upper crust post archaean shale and a highly differentiated low nd 0 end member trace element ratios which are not significantly fractionated during erosion and sedimentation e g th nd th y and la sm show relatively smooth increases between these reservoirs whereas other trace element ratios which are fractionated both by sedimentary and magmatic processes e g rb sr and rb zr increase dramatically in the more differentiated crustal reservoirs

rare earth element geochemistry of australian paleozoic graywackes and mudrocks provenance and tectonic control abstract in the paleozoic graywackes of eastern australia there is an increase in the total abundance of rare earth elements ree a light to heavy ree ratio and a decrease in the chondrite normalized eu anomaly with the increase in sio2 al2o3 and k2o na2o ratios this is due to the change in the dominant source rocks from andesite to dacite to granite gneiss and sedimentary rocks similarly an increase in total ree and a decrease in eu anomaly is also seen in the associated mudrocks with the increase in total clay content this correlation in paleozoic sedimentary rocks suggests that the ree characteristics of terrigenous sedimentary rocks reflect the depositional tectonic setting of the basin the oceanic island arc type graywackes are characterised by their lower total ree abundance only slight enrichment of lree over hree and the absence of a negative eu anomaly on chondrite normalised plots the continental island arc type graywackes are discriminated by their higher ree abundance and la yb ratio the presence of a small negative eu anomaly on the chondrite normalised plots and the significant enrichment of eu compared to paas post archean average australian shale the sedimentary rocks deposited on andean type active continental margins passive margins platform and cratonic basins are all characterised by the high enrichment of lree over hree and the presence of a pronounced negative eu anomaly on chondrite normalised plots and can not be discriminated from each other by ree patterns alone

measuring core reduction using 3d flake scar density a test case of changing core reduction at klasies river mouth south africa a new core reduction index is presented calculated as the ratio of flake scar number to 3d surface area sdi the index is tested experimentally on five types of core blade discoid levallois biface and multiplatform cores and then applied to the core assemblages from five sub stages of the middle stone age at klasies river mouth south africa preliminary results indicate that the sdi possesses the desirable attributes of a successful reduction index and is a significant improvement on traditional proxy measures of core reduction the results of the archaeological case study confirm previous untested observations that cores from the howiesons poort and msaiii sub stages are more heavily reduced than preceding and following stages and that local and exotic raw materials as well as different types of cores are all more heavily reduced during these periods the sdi fills a significant lacuna in available core reduction measures

petrograph a new software to visualize model and present geochemical data in igneous petrology a new software petrograph has been developed to visualize elaborate and model geochemical data for igneous petrology purposes the software is able to plot data on several different diagrams including a large number of classification and petrotectonic plots petrograph gives the opportunity to handle large geochemical data sets in a single program without the need of passing from one software to the other as usually happens in petrologic data handling along with these basic functions petrograph contains a wide choice of modeling possibilities from major element mass balance calculations to the most common partial melting and magma evolution models based on trace element and isotopic data results and graphs can be exported as vector graphics in publication quality form or they can be copied and pasted within the most common graphics programs for further modifications all these features make petrograph one of the most complete software presently available for igneous petrology research

black holes of the bahamas what they are and why they are black abstract black holes are vertical cave systems which have no known lateral passages and form in the interior stable regions of the larger bahamian islands they are found where the land is transitional between submerged and dry land not dissimilar to saltmarsh environments most black holes are located in the central to western side of the island of south andros in the bahamas although one has been found on the northern transitional shore of grand bahama island the water in these holes appears black in colour due to the presence of a 1 m thick microbial layer located within the upper third of the water column 18 19 m at the boundary between the oxic low salinity upper water mass and the denser anoxic saline water layer the boundary between the two water masses is characterised by sharp discontinuities in physico chemical gradients salinity increased from 12 to 35 psu temperature from 29 c to 36 c ph decreased from ph 8 6 to 6 45 and dissolved o 2 from 6 mg l to allochromatium and thiocapsa have been identified as the dominant members of this warm 36 c saline sulphide rich layer and achieve population densities 10 7 viable cells ml calculations reveal that this layer of anoxygenic phototrophic bacteria in the south andros black hole may have a biomass content of approximately 5 06 ton dry weight

growth of planetary crusts the planets and satellites of the solar system show much diversity but most have formed crusts which differ substantially from their bulk compositions three principal types of crust may be broadly distinguished primary formed after accretional heating e g lunar highlands secondary formed following partial melting in planetary mantles e g lunar maria terrestrial oceanic crust and tertiary formed by processing of secondary crusts of which the continental crust of the earth is the only identifiable example crustal growth before 3800 m y was complicated by the heavy planetesimal bombardment active erosion on the earth is likely to have destroyed the brecciated rubble resulting from over 200 mare orientale scale events in this period the mercurian crust is probably primary perhaps analogous to the lunar highlands in contrast the observable martian and venusian crusts are secondary dominated by basaltic volcanism the icy crusts of the satellites of the outer planets are mixtures of both primary and secondary crusts with complex histories ganymede is of special interest in displaying a secondary grooved terrain water ice crust which has split an older more heavily cratered possibly primary crust slight expansion has resulted probably from polymorphic transitions from high density ice viii to low density ice i the primary lunar crust 12 of lunar volume grew in 108 years secondary crusts derived by partial melting of mantles grow at a much slower rate total production of terrestrial oceanic crust over 4000 m y is only 2 of planetary volume whereas terrestrial continental crustal growth is even slower producing over the same period a volume only about 0 33 that of the earth crustal growth on the other planets appears to be an irreversible process without evidence of recycling no evidence for massive planetary expansion as required by expanding earth hypotheses is apparent on the other planets or satellites of the solar system

modeling circulation and seasonal fluctuations in perennially ice covered and ice walled lake untersee antarctica lake untersee antarctica is a freshwater perennially ice covered lake bounded along its north by the anuchin glacier the massachusetts institute of technology general circulation model used on a representative wedge shaped lake and actual bathymetry for lake untersee produces estimates for circulation and long term temperature and mixing trends modeled circulation is dominated by an anticyclonic gyre in front of the glacier with slower 3 mm s 1 flow exhibited around the lake s perimeter allowing effective mixing throughout most of the lake with time scales of one month estimated velocities bound maximal glacial flour particle size at 10 m for effective transport throughout the lake consistent with the sediment s mostly fine composition observed in field studies and mixing time scales mean nonuniformities in measured o2 concentration likely require recent or ongoing sources areas in which large temperature gradients prevent exchange of fluid demonstrate minimal mixing such as the lake s upper water layers and the anoxic basin in the south and circulation is consistently slowed in the northern sheltered bay area mean flow velocities fluctuate by about one fifth of their magnitude between summer and winter and the lake s almost homothermal body temperature varies by about one tenth of a degree over the same period while calculated temperature profiles qualitatively agree with field data the model s long term equilibrium temperature differs substantially likely due to poor description of heat transfer with the glacier model robustness tests show results differ by 10 when either grid scale or water temperature are halved

the still bay points of blombos cave south africa we present the results of a technological and morphometric analysis of all the still bay points n 371 recovered from the 1993 to 2004 excavations at blombos cave we have been able to reconstruct the manufacturing sequence of the bifacial points from initial shaping by direct internal percussion to finished morphology by direct marginal percussion identifications of impact fractures and manufacturing breaks are based on comparisons with experimental and archaeological bifacial points of verified function i e paleoindian points from bison kill sites replicates of solutrean points mounted as spear heads or arrowheads and shot into adult cattle and experimental replication on local raw materials our analysis shows that a only a minority of the points are finished forms and that a large number of pieces are production failures a situation known at bifacial point production sites of later ages b morphometric and impact scar analyses should take into account this process and distinguish finished points from preforms and unfinished points c there were at least three different kinds of raw material sources and that there is a marked increase in the frequencies of silcrete with respect to the m2 and m3 phases at blombos d three kinds of evidence prove that some of the points were hafted axially and used as spear tips e production of bifacial points was a primary activity at the site but the hypothesis of intergroup exchange of still bay points cannot be sustained on the basis of present evidence and f the still bay phase appears to initiate a trend to relatively rapid changes in specialized hunting weaponry and that this innovation is congruent with other innovations such as bone tools shell beads and engraved ochre of the m1 and m2 phases at blombos

multielement geochemistry of offshore sediments in the southeastern yellow sea and implications for sediment origin and dispersal abstract in total 116 surface sediments were collected from an offshore area of the southeastern yellow sea including a large mud belt southeastern yellow sea mud seysm and analyzed for grain size and geochemical composition organic carbon and 42 elements principal component analysis revealed that elemental compositions of the offshore sediments were mostly controlled by common aluminosilicate clay minerals and quartz most elements heavy minerals hf zr u th rare earth elements rees biogenic calcium carbonates ca sr feldspar and mica k ba pb and mn oxides mn oxide coatings on sand grains notably total ree concentrations may be associated with heavy minerals possibly zircon and monazite especially in silty grains even though heavy ree hrees concentrations are more strongly controlled by clay minerals in muddy sediments the diagnostic discrimination plots of geochemical compositions e g fe vs al mg vs al light ree vs hree and la lu ucc vs la y ucc suggested that the offshore sediments especially in seysm deposits were composed of a mixture of korean river derived silts and chinese river derived clays this demonstrated that chinese river sediments especially clay particles largely contributed to the formation of the giant mud belt in the korean coastal area furthermore the observed geochemical end members provide new markers of sediment provenance which can be used to track dispersal patterns and sediment limits from chinese and or korean rivers