growth of volcanic ash aggregates in the presence of liquid water and ice an experimental approach key processes influencing the aggregation of volcanic ash and hydrometeors are examined with an experimental method employing vibratory pan aggregation mechanisms of aggregation in the presence of hail and ice pellets liquid water 30 wt and mixed water phases are investigated at temperatures of 18 and 20 c the experimentally generated aggregates examined in hand sample impregnated thin sections sem imagery and x ray microtomography closely match natural examples from phreatomagmatic phases of the 27 ka oruanui and 2010 eyjafjallajokull eruptions laser diffraction particle size analysis of parent ash and aggregates is also used to calculate the first experimentally derived aggregation coefficients that account for changing liquid water contents and subzero temperatures these indicate that dry conditions 1 in contrast liquid saturated conditions 15 20 wt liquid promote less size selective processes crystalline ice was also capable of preferentially selecting volcanic ash 31 m under liquid free conditions in a two stage process of electrostatic attraction followed by ice sintering however this did not accumulate more than a monolayer of ash at the ice surface these quantitative relationships may be used to predict the timescales and characteristics of aggregation such as aggregate size spectra densities and constituent particle size characteristics when the initial size distribution and water content of a volcanic cloud are known the presence of an irregularly shaped millimeter scale vacuole at the center of natural aggregates was also replicated during interaction of ash and melting ice pellets followed by sublimation fine grained rims were formed by adding moist aggregates to a dry mixture of sub 31 m ash which adhered by electrostatic forces and sparse liquid bridges from this we infer that the fine grained outer layers of natural aggregates reflect recycled exposure of moist aggregates to regions of volcanic clouds that are relatively dry and dominated by 31 m ash

the collapse of megafaunal populations in southeastern brazil whether humans or climate change caused the extinction of megafaunal populations is actively debated caves in the lagoa santa provide mixed assemblages of megafauna and human remains however it remains uncertain the extent to which humans and megafauna interacted or overlapped temporally here we present the first paleoecological record from lowland south america that tracks the decline of megafauna and its ecological implications we provide a data set for pollen charcoal and sporormiella from two lakes in southeastern brazil that span the last 23 000 yr the data showed reduced abundances of sporormiella and an inferred megafaunal population decline that began 18 000 yr ago with the functional extinction occurring between 12 000 and 11 500 yr ago population declines coincided with wet events the age of the final megafaunal decline is within the range of the first human occupation of the region our data are consistent with climate causing the population collapse with humans preventing population recovery and inducing extinction we did not observe some of the ecological repercussions documented at other sites and attributed to the megafaunal extinction habitat specific ecological consequences of the extinction add to the heterogeneity of late pleistocene and early holocene landscapes

ice nucleation and overseeding of ice in volcanic clouds 1 water is the dominant component of volcanic gas emissions and water phase transformations including the formation of ice can be significant in the dynamics of volcanic clouds the effectiveness of volcanic ash particles as ice forming nuclei in is poorly understood and the sparse data that exist for volcanic ash in have been interpreted in the context of meteorological rather than volcanic clouds in this study single particle freezing experiments were carried out to investigate the effect of ash particle composition and surface area on water drop freezing temperature measured freezing temperatures show only weak correlations with ash in composition and surface area our measurements together with a review of previous volcanic ash in measurements suggest that fine ash particles equivalent diameters between approximately 1 and 1000 m from the majority of volcanoes will exhibit an onset of freezing between 250 260 k in the context of explosive eruptions where super micron particles are plentiful this result implies that volcanic clouds are in rich relative to meteorological clouds which typically are in limited and therefore should exhibit distinct microphysics we can expect that such overseeded volcanic clouds will exhibit enhanced ice crystal concentrations and smaller average ice crystal size relative to dynamically similar meteorological clouds and that glaciation will tend to occur over a relatively narrow altitude range

multiparametric observation of volcanic lightning sakurajima volcano japan we recorded volcanic lightning generated by vulcanian explosions at sakurajima volcano using a synchronized multiparametric array physical properties of lightning are related to plume dynamics and associated electromagnetic field variations are revealed by video observations high speed and normal speed together with infrasound and high sampling rate magnetotelluric signals data show that volcanic lightning at sakurajima mainly occurs in the plume gas thrust region at a few hundred meters above the crater rim where the overpressure of the turbulent volcanic jets determines the electrification of particles generating a complex charge structure in the growing plume organization of charges may be achieved at later stages when the plume transitions from the jet phase to the convective phase comparison with atmospheric sounding and maximum plume height data show that the effect of hydrometeors on flash generation at sakurajima is negligible and can be more prudently considered as an additional factor contributing to the electrification of volcanic plumes

new understandings of ni mo mineralization in early cambrian black shales of south china constraints from variations in organic matter in metallic and non metallic intervals abstract the well known ni mo ores hosted in early cambrian black shales of south china are one of the research highlights in economic geology for the past few decades however their origin is complex and still debated here based on a case study in the huangjiawan ore of zunyi city guizhou province we generate several new understandings regarding ni mo mineralization through a comparative investigation of organic matter in metallic and non metallic stratigraphic intervals including abundance type maturity and relationship to mineralization we find new direct evidence for biotic impacts on mineralization organic matter and rhodophyte cystocarps red algae in particular may be significantly correlated to mineralization as it accumulates mineralized ni and mo however this organic material as well as disseminated and amorphous organic matters is not the sole and predominant factor controlling mineralization as implied from the nonlinear correlation between organic matter abundance maturation and mineralization other fluid sources e g hydrothermal and or seawater also contribute to mineralization which may be influenced by hydrothermal activity ni and mo may have mineralized independently as suggested by their differential accumulation in different structures of the cystocarps different relationships between organic matter abundance and thermal maturation and mineralized element concentration as well as the large variation in element accumulation coefficients the history of mineralization is complex as ni and mo may be or not be deposited together during the same stage of mineralization these results might also have broader implications for understanding the origin of sediment hosted ores worldwide

detection of plumes at redoubt and etna volcanoes using the gps snr method abstract detection and characterization of volcanic eruptions is important both for public health and aircraft safety a variety of ground sensors are used to monitor volcanic eruptions data from these ground sensors are subsequently incorporated into models that predict the movement of ash here a method to detect volcanic plumes using gps signals is described rather than carrier phase data used by geodesists the method takes advantage of attenuations in signal to noise ratio snr data two datasets are evaluated the 2009 redoubt volcano eruptions and the 2013 2015 eruptions at mt etna snr based eruption durations are compared with previously published seismic infrasonic and radar studies at redoubt volcano snr based plume detections from mt etna are compared with l band radar and tremor observations to place these snr observations from redoubt and etna in context a model of the propagation of gps signals through both water water vapor and tephra is developed neither water nor fine ash particles will produce the observed attenuation of gps signals while scattering caused by particles 1 cm in diameter potentially could

early cambrian ocean anoxia in south china the cause of the most marked changes in the evolution of life which define the first order stratigraphic boundary between the precambrian and the phanerozoic eon remains enigmatic and a highly topical subject of debate a global ocean anoxic event triggered by large scale hydrogen sulphide h 2 s release to surface waters has been suggested by wille et al on the basis of two data sets from south china and oman to explain the fundamental biological changes across the precambrian cambrian pc c boundary here we report a new precise shrimp u pb zircon age of 532 3 0 7 million years myr ago fig 1 for a volcanic ash bed in the critical unit that reflects the ocean anoxic event the lowermost black shale sequence of the niutitang formation in the guizhou province south china this age is significantly younger than the precise pc c boundary age of 542 0 0 3 myr ago approximately 10 myr younger than the extinction of the ediacaran fauna and thus challenging the view of a major ocean anoxic event having been responsible for the major changes in the direction of evolution at the pc c boundary

nickel isotopic variation in black shales from bohemia china canada and finland a reconnaissance study we present 60ni values for black shales determined by double spike mc icp ms the samples comprise paleoproterozoic talvivaara ni zn co cu black shales from finland neoproterozoic black shales from the tepla barrandian unit czech republic early cambrian ni mo rich black shales from the yangtze craton and devonian ni zn pge black shales from yukon canada in addition the sample set includes a black smoker sample from the logatchev hydrothermal field mid atlantic ridge the 60ni values vary from 0 84 0 09 to 0 62 0 04 2sd with a median of 0 10 n 28 ni isotopic compositions were predominantly lighter than those of abiotic terrestrial and extraterrestrial samples 0 15 and 0 27 mantle 0 23 gall et al 2017 present day seawater 1 44 cameron and vance 2014 dissolved ni from riverine input 0 84 cameron and vance 2014 ferromanganese crusts 0 9 2 5 gall et al 2013 devonian mississippian organic rich marine sediments lower jurassic organic rich marine sediments 0 2 2 5 average 0 92 n 18 porter et al 2014 and euxinic sediments of the black sea 0 14 0 51 vance et al 2016 however the range of 60ni values in our black shale samples was close to that of the weathering products of mafic ultramafic rocks ore and soil samples ranging from 0 60 to 0 30 ratie et al 2015 spivak birndorf et al 2018 ni sulfide ores hosted by archean komatiites from australia and canada 0 10 to 1 03 average 0 70 n 8 gueguen et al 2013 and archean ni rich magmatic sulfides from zimbabwe 0 28 to 0 47 n 6 hoffman et al 2014 based on our observations and considering the extremely low contribution of direct biological uptake of ni and a dominant ni residence in early fe ni sulfides we suggest that our mostly light ni isotopic compositions in metal rich black shales result from sulfidization of organic matter and ni removal into sulfides

volcanic plume electrification experimental investigation of a fracture charging mechanism although ashfall from particulate volcanic plumes is known to be highly electrically charged little is known about the charging mechanism we describe experiments designed to investigate the particle charges generated from the fracture of pumice small silicate particles were produced in the laboratory during collisions between two samples cut from pumice clasts the net charge magnitudes detected on these particles are similar to those previously measured on ashfall from volcanic plumes 10 5 to 10 6 c kg 1 this net charge is also shown to be the result of a small imbalance between the sums of individual particle charges of both polarities which are up to several orders of magnitude larger than the net charge the magnitude of both the net and single polarity specific charges were only weakly affected by changes of relative humidity but single polarity charges increased steadily with increasing sample impact velocities the dominant charging process during the experiments was that of material fracture the charging mechanism is thus interpreted to be fractoemission the release of nuclear particles from fresh crack surfaces occurring during the production of the silicate particles this implies that the electrification of volcanic plumes could be the result of brittle fragmentation of magma or pumice clasts within the upper regions of the conduit and in the jet region of the plume

observations of volcanic lightning during the 2009 eruption of redoubt volcano abstract observations of volcanic lightning during the eruption of redoubt volcano in march and april 2009 were made with the lightning mapping array during the eruption twenty three distinct episodes of volcanic lightning were observed electrical activity occurred as either a volcanic lightning storm with up to thousands of lightning discharges or as a weak electrical event with only a handful of lightning discharges during the volcanic lightning storms we observed two phases of electrical activity the explosive phase and the plume phase the explosive phase consisted of very small discharges on the order of 10 100 m occurring directly above the vent while an explosive eruption was ongoing whereas the plume phase was comprised of discharges occurring throughout the plume subsequent to the explosive eruption the area of discharges during the explosive phase ranged from less than 1 km2 to 50 km2 or more the electrical activity at the beginning of the plume phase was dominated by small discharges over time the horizontal extent of the flashes increased with the largest flashes occurring at the end of the plume phase the distribution of the horizontal size of the discharges over the lifetime of the storm indicate that the charge structure of the plume evolved from a complex and clumpy structure to a more simple horizontally stratified structure plume height was shown to be a key factor in the quantity of lightning in a storm the volcanic lightning storms occurred in plumes with column heights greater than 10 km the tall plumes may contribute to the efficiency of charge generation through ice collisions by providing strong updrafts from the large thermal energy input from the eruption

inferring compressible fluid dynamics from vent discharges during volcanic eruptions observations at numerous volcanoes reveal that eruptions are often accompanied by continual radio frequency crf emissions the source of this radiation however has remained elusive until now through experiments and the analysis of field data we show that crf originates from proximal discharges driven by the compressible fluid dynamics associated with individual volcanic explosions blasts produce flows that expand supersonically generating regions of weakened dielectric strength in close proximity to the vent as erupted materialcharged through fragmentation friction or other electrification processtransits through such a region pyroclasts remove charge from their surfaces in the form of small interparticle spark discharges or corona discharge discharge is maintained as long as overpressured conditions at the vent remain beyond describing the mechanism underlying crf we demonstrate that the magnitude of the overpressure at the vent as well as the structure of the supersonic jet can be inferred in real time by detecting and locating crf sources

formation of fe mn si oxide and nontronite deposits in hydrothermal fields on the valu fa ridge lau basin abstract hydrothermal fe mn si oxides and nontronite are pervasive in the hine hina vai lili and mariner hydrothermal fields along the central valu fa ridge lau basin morphometric and mineralogical analyses reveal that the iron rich filaments are the most important constituents of these fe mn si oxide deposits both the morphologies and chemical composition of the filaments indicate that neutrophilic fe oxidizing bacteria have played a key role in the formation of these deposits a key process of the formation of these deposits is the creation of a complicated filamentous network in which a series of metabolic activities and passive sorption and nucleation processes occur the precipitation of dissolved si in unsaturated and saturated states leads to a two generation growth model in the hydrothermal vents the precipitation of amorphous opal occurs in a relatively narrow temperature range 41 1 42 9 c based on oxygen isotope analyses indicating a fast precipitation rate of opal a when conductive cooling of the hydrothermal fluid occurrs patchy nontronite in the mariner fields is a product of the direct precipitation from hydrothermal fluids at a temperature of 87 9 c whereas the scattered nontronite at the hine hina field is the product of the replacement of hydrothermal fe si oxides at a temperature of 46 2 c

an sem study of microfossils in the black shale of the lower cambrian niutitang formation southwest china implications for the polymetallic sulfide mineralization abstract the black shale in the lower cambrian niutitang formation on the southeastern margin of the yangtze platform hosts a layer of polymetallic sulfide ores containing extremely high concentrations of ni up to 3 8 wt and mo up to 7 5 wt abundant micrometer sized microfossils were observed in the ni mo sulfide enriched layer under scanning electron microscopy the microfossils include vesicles with clear organic wall structures and permineralized internal contents these structures resemble unicellular green algae both biomass adsorbed transition metals and biological structural protein metals could be accumulated and mineralized from the blooming algae followed by anoxic microbial reduction and immobilization the biotic impact may be a substantial mechanism for the massive ni and mo sulfide deposition in a typical restricted ocean basin environment

uranium mineralization and its radioactive decay induced carbonization in a black shale hosted polymetallic sulfide ore layer southwest china the black shale in the lower cambrian niutitang formation southwest china which has been dated to 532 3 0 7 ma by u pb radiometric measurements hosts a sedimentary layer with abnormally high ni mo pge au contents this layer is enriched in ni up to 3 8 wt mo up to 7 7 wt and u up to 595 ppm but its genesis is still controversial here we report the first direct observation of uranium bearing minerals and their radioactive effects on the surrounding matter in the polymetallic sulfide ore x ray absorption fine structure analyses confirmed the reduced valence state of uranium in combination with high resolution electron microscopy and electron probe microanalysis the mineral was identified as coffinite usio4 a strong positive correlation between the sizes of the coffinite crystals and their surrounding carbonized rings reveals that the coffinite is authigenic and its crystallization produced radiation resulted in the radiolysis of surrounding organic matter the association of various biogenic metal sulfides phosphates and abundant organic substances within the ni mo sulfide enriched ore suggests that biological adsorption may have participated in the enrichment of soluble u vi and that microbial sulfate reduction might have facilitated the uranium mineralization

cyclic sedimentation in brazilian caves mechanisms and palaeoenvironmental significance abstract caves associated with doline slopes in the tectonically stable area of eastern brazil display remarkable sequences of clastic sediment intercalated with calcite layers sediment erosion has also occurred allowing access to formerly sediment filled passages the palaeoenvironmental meaning and chronology of these three processes i e clastic sediment input clastic sediment erosion and speleothem precipitation were studied in both semi arid campo formoso and sub humid lagoa santa areas through 230 th dating and stratigraphical analyses the dry climate of the campo formoso area prevents speleothem deposition at present but soil erosion results in valley aggradation and cave infilling growth periods of speleothems and travertines in this area have allowed the recognition of recurrent past phases of increased humidity correlated with wet conditions recorded in southeastern brazil speleothem calcite at the lagoa santa area there is limited speleothem precipitation and sediment input at present however sediment entrainment is actively exhuming speleothems and exposing cave passages sediment erosion inside caves in the area is interpreted as being due to intermediate climatic conditions not wet enough to favour speleothem deposition and not too dry to allow doline slope erosion and sediment transport into caves due to the low rates of denudation and isostatic rebound inherent to tectonically stable areas cave passages will remain within the range of sediment infill and erosion for a much longer time than in tectonically active areas spanning in average at least three full glacial interglacial cycles as uplift proceeds cave passages will be decoupled from the doline bottom and no longer will be affected by erosion or infilling episodes sediment filled passages in many caves in the lagoa santa region are relict features that display ancient clastic and chemical precipitation the three processes described above have occurred throughout the life history of the caves resulting in complex sediment assemblages that can however show significant intra and inter site variations

did ice charging generate volcanic lightning during the 2016 2017 eruption of bogoslof volcano alaska the 2016 2017 shallow submarine eruption of bogoslof volcano in alaska injected plumes of ash and seawater to maximum heights of 12 km more than 4550 volcanic lightning strokes were detected by the world wide lightning location network wwlln and vaisala s global lightning dataset gld360 over 9 months lightning assisted monitoring efforts by confirming ash producing explosions in near real time but only 32 out of the 70 explosive events produced detectable lightning what led to electrical activity within some of the volcanic plumes but not others and why did the lightning intensity wax and wane over the lifetime of individual explosions we address these questions using multiparametric observations from ground based lightning sensors satellite imagery photographs acoustic signals and 1d plume modeling detailed time series of monitoring data show that the plumes did not produce detectable lightning until they rose higher than the atmospheric freezing level approximated by 20 c temperatures for example on 28 may 2017 event 40 the delayed onset of lightning coincides with modeled ice formation in upper levels of the plume model results suggest that microphysical conditions inside the plume rivaled those of severe thunderstorms with liquid water contents 5 g m 3 and vigorous updrafts 40 m s 1 in the mixed phase region where liquid water and ice coexist based on these findings we infer that thunderstorm style collisional ice charging catalyzed the volcanic lightning however charge mechanisms likely operated on a continuum with silicate collisions dominating electrification in the near vent region and ice charging taking over in the upper level plumes a key implication of this study is that lightning during the bogoslof eruption provided a reliable indicator of sustained ash rich plumes and associated hazards above the atmospheric freezing level

biogenic origin of intergrown mo sulphide and carbonaceous matter in lower cambrian black shales zunyi formation southern china abstract the lower cambrian zunyi formation in southern china hosts complex intergrown phases of mo sulphides and anthracite like carbonaceous matter and graphite mosc pyrite and ni sulphides these sulphides occur in a few centimeters thick polymetallic stratiform layer in black shales above phosphorites cherts dolomites and barite the ore horizon contains 7 wt mo 2 wt ni 19 wt s and 13 wt c org and c tot co 2 58 wt 14 wt cao 1 2 wt as 2000 ppm se 5400 ppm zn 450 ppm u and v and up to 1 ppm platinum group elements three types of mosc phases always including framboidal pyrite are distinguished 1 rounded structures few hundred microns large 2 relict inclusions in diagenetic pyrite 3 grains interstitial to sulphurised and phosphatised organic matter at the nanoscale mosc is represented by nanometric porous rounded structures of mos 2 finely intergrown with carbonaceous matter of typical nano onion structures mosc also contains nanocrysts of quartz clays ca sulphate carbonate and ni sulphides micro raman spectroscopy shows that the carbon phase has a maturation grade of anthracite indicating temperatures below 300 c mosc is mainly composed of 25 wt mo 23 wt s 5 6 wt fe 2 5 wt ni 33 wt c 1 5 wt o 0 6 wt n and several hundreds of ppm of cu as se sb pd zn co and sn electron energy loss spectra show that n is related to nanosized carbonaceous matter the mean c n ratio 57 of mosc is similar to those observed in marine organic matter and those reported from zooplankton at hydrothermal vents the mineralized shales are crosscut by hydrothermal veins composed of carbonate or barite always associated with quartz apatite and fe and zn sulphides a paragenesis also observed as nanocrysts in mosc although mo originated from seawater its extreme concentration is due to an enhanced growth of bacterial consortia in a diffuse hydrothermal vent system these consortia may be dominated by nitrogen fixing and mo dependant hyperthermophilic or mesophilic species containing nitrogenase composed also of mo s fe organic matter decay led thus to the formation of mosc and the included framboidal pyrite

metal sources for the polymetallic ni mo pge mineralization in the black shales of the lower cambrian niutitang formation south china abstract total organic carbon content toc trace element and platinum group element pge concentrations were determined in the black shales of the lower cambrian niutitang formation in the nayong area guizhou province south china in order to study the polymetallic ni mo pge mineralization the results demonstrate that numerous elements are enriched in the polymetallic ores compared to those of the nearby black shale particularly ni mo zn toc and total pge which can reach up to 7 03 wt 8 49 wt 11 7 wt 11 5 wt and 943 ppb respectively the elemental enrichment distribution patterns are similar to those in the zunyi and zhangjiajie areas except that the nayong location is exceptionally enriched in zn whereas positive correlations are observed between the ore elements of the polymetallic ores no such correlations are observed in the black shale these positively correlated metallic elements are classified into three groups co ni cu pge zn cd pb and mo tl toc the geological and geochemical features of these elements suggest that proterozoic and early palaeozoic mafic and ultramafic rocks dolomites and or pb zn deposits of the neoproterozoic dengying formation and seawater could be the principal sources for co ni cu pge zn cd pb and mo tl toc respectively furthermore the chondrite normalized patterns of pges with pd pt pd ir and pt ir indicate that pge enrichment of the polymetallic ores is most likely related to hydrothermal processes associated with the mafic rocks in contrast pge enrichment in the black shale resembles that of the marine oil shale with terrigenous and seawater contributions our investigations of toc trace elements and pge geochemistry suggest that multiple sources along with submarine hydrothermal and biological contributions might be responsible for the formation of the polymetallic ni mo pge mineralization in the black shales of the lower cambrian niutitang formation across southern china

reconstructing habitats in central amazonia using megafauna sedimentology radiocarbon and isotope analyses abstract a paleomegafauna site from central amazonia with exceptional preservation of mastodons and ground sloths allows for the first time a precise age control based on 14 c analysis which together with sedimentological and 13 c isotope data provided the basis to discuss habitat evolution within the context of climate change during the past 15 000 yr the fossil bearing deposits trapped within a depression in the paleozoic basement record three episodes of sedimentation formed on floodplains with an intermediate unit recording a catastrophic deposition through debris flows probably favored during fast floodings the integrated approach presented herein supports a change in humidity in central amazonia through the past 15 000 yr with a shift from drier to arboreal savanna at 11 340 50 14 c yr b p and then to a dense forest like we see today at 4620 60 14 c yr b p

identification and importance of critical depositional gaps in pitfall cave environments the fossiliferous deposit of cuvieri cave eastern brazil abstract the majority of extinct brazilian late quaternary mammal i e megafauna remains comes from cave deposits and was retrieved through excavations lacking detailed stratigraphical context this poses a major problem since these deposits present multifaceted processes of formation based on the meticulous excavation of a pitfall site within cuvieri cave minas gerais eastern brazil this article describes a critical albeit subtle temporal discontinuity between different fossiliferous sedimentary facies and discusses its significance to the contextualization of the paleontological remains recovered from the site the discontinuity was described based on sedimentary analyses bone deposition processes taxonomy and ams radiocarbon chronology two facies were distinguished and named according to their color and texture an upper dark brown silt loam bsl and a lower dark reddish brown silt loam rbsl besides color differences they present differences in grain size distribution and chemical composition these analyses show that the rbsl has in its composition only half the sand and one third more the silt than bsl it also shows that mean percent values for the rbsl in comparison to the bsl are higher for silica 42 35 versus 15 80 aluminum 18 63 versus 7 58 and iron 8 45 versus 3 79 and lower for calcium 10 07 versus 36 14 and volatiles 13 86 versus 30 10 these differences are attributed to changes in sediment source and entrance route differences were also observed in the faunal remain analyses rbsl has abundant megafauna remains originally deposited within this facies while the scarce megafauna material found in bsl is the result of mixing processes despite these differences animal entrapment is considered the best scenario to explain bone accumulation in both facies ams radiocarbon dates indicate that the bsl was deposited during the holocene with dates ranging from 8580 cal yr bp to the present while the rbsl deposition dates to the holocene pleistocene transition 13 600 10 660 cal yr bp radiocarbon dating also indicates that the subtle erosional surface that limits both facies represents a temporal gap between a minimum age of 8 4 cal kyr bp and a maximum age of 11 0 cal kyr bp the recognition of this discontinuity allows for a more accurate interpretation of bone accumulation enabling the differentiation of faunal assemblages that might otherwise be considered part of a continuum

petrology and hydrocarbon potential of microalgal and macroalgal dominated oil shales from the eocene huadian formation ne china abstract a series of oil shales of middle to late eocene age occur in the huadian area of jinlin province northeast china analytical results from 22 rock samples collected from an underground mine in the guanglangtou district in the huadian basin show that the total organic carbon toc contents of the oil shale layers are very high 10 6 wt to 39 6 wt with vitrinite reflectance ro values of 0 41 0 02 and rock eval hydrogen index hi values up to 887 biomarker analyses show a high proportion of hopenes and hopanes with stereochemistry indicative of low maturity detailed organic petrologic analysis demonstrates that the organic matter is dominated by lamalginite and telalginite the presence of botryococcus in the telalginite indicates that the depositional environment of the oil shale is lacustrine this is consistent with low si and s contents and high c s ratios fragments from a newly identified benthic macroalgal rhodophyte were found in some thin layers raising the possibility that the depositional environment of some oil shale layers may have been influenced by marine flooding since rhodophyta are uncommon in freshwater systems two oil shale samples with different algal compositions were selected for assessment of hydrocarbon generation potential sample hd 21 is dominated by phytoplanktic lamalginite with a high hi value of 869 mg hc g toc while sample hd 20 has a lower hi value 490 mg hc g toc and contains high contents of the benthic rhodophyte as well as some phytoplanktic lamalginite hi values and thermal simulation experiments showed that the phytoplankton dominated shale hd 21 has a much higher hydrocarbon generation potential than the rhodophyte dominated oil shale hd 20 even though the toc content of hd 20 was much higher indicating that the benthic macroalgal macerals have a much lower capacity to generate oil when thermally mature

using lightning observations as a volcanic eruption monitoring tool lightning commonly occurs in the eruption columns produced by explosive volcanic eruptions there are several different kinds of lightning detection instruments that could be employed to help monitor volcanoes each with their own advantages and disadvantages very low frequency vlf instruments have the ability to detect lightning at long ranges but tend to have low sensitivity due to network geometry and typically can provide only the time and 2 d location of a cloud to ground return stroke or similar high amplitude pulse produced by an intracloud discharge low frequency lf and medium frequency mf instruments typically have more sensitivity than a vlf network but can only be used for detection on a regional scale very high frequency vhf lightning mapping instruments also provide only regional coverage but detect all lightning within their range during the 2009 eruption of redoubt volcano alaska usa each of these types of instruments detected lightning from redoubt s ash plume the vhf system consistently detected lightning before the other two during each distinct explosive event and also detected more lightning than the others by one or two orders of magnitude lightning observations could be used to confirm and in some cases detect explosive volcanic activity the rapid response provided by lightning monitoring is a valuable tool for fast identification of potentially hazardous ash clouds

ichnofossils and their significance in the cambrian successions of the parahio valley in the spiti basin tethys himalaya india abstract the spiti basin exposes well preserved cambrian successions in the tethys himalaya the present ichnofossil assemblage is reported from the debsakhad member of the kunzum la formation the ichnofossils includes the ichnogenera bergaueria chondrites cruziana didymaulichnus dimorphichnus diplichnites helminthorhaphe merostomichnites monocraterion monomorphichnus nereites palaeopascichnus palaeophycus phycodes planolites rusophycus skolithos scolicia treptichnus etc along with annelid worm burrow and scratch marks these ichnogenera can be assigned to cubichnial repichnial pascichnial to fodinichnial behaviors the ichnofossils reported from this section provide evidence regarding the developmental patterns during the early phase of life in absence of trilobites the present assemblage of ichnofossils is very significant in assigning the age of the debsakhad member the abundance of ichnofossils in sandstone siltstone and in shale beds indicate that the ichnocenosis is dominated by a high behavioral diversity ranging from the suspension to deposit feeders three lithofacies were observed in this section they show a vertical disposition which further reflects general upward coarsening trend ichnofossils are mostly produced by arthropods along with crustacean polychaetes and polyphyletic vermiforms due to the paucity of body fossil as well as microbiota in the lowermost beds of the debsakhad member the precambrian cambrian boundary could not be demarcated however the presence of treptichnus and phycodes can be considered as a horizon marker for the beginning of lower cambrian in this section

diet and habitat of toxodont megaherbivores mammalia notoungulata from the late quaternary of south and central america abstract the toxodont megaherbivores toxodon and mixotoxodon were endemic to south and central america during the late quaternary isotopic signatures of 47 toxodont teeth were analyzed to reconstruct diet and ancient habitat tooth enamel carbon isotope data from six regions of south and central america indicate significant differences in toxodont diet and local vegetation during the late quaternary toxodonts ranged ecologically from c3 forest browsers in the amazon mean 13c 13 4 to mixed c3 grazers and or browsers living either in c3 grasslands or mixed c3 forested and grassland habitats in honduras mean 13c 9 3 buenos aires province argentina 13c 8 7 and bahia brazil mean 13c 8 6 to predominantly c4 grazers in northern argentina 13c 4 4 to specialized c4 grazers in the chaco of bolivia 13c 0 1 although these toxodonts had very high crowned teeth classically interpreted for grazing the isotopic data indicate that these megaherbivores had the evolutionary capacity to feed on a variety of dominant local vegetation in the ancient amazon region carbon isotope data for the toxodonts indicate a c3 based tropical rainforest habitat with no evidence for grasslands as would be predicted from the neotropical forest refugia hypothesis

charge mechanism of volcanic lightning revealed during the 2010 eruption of eyjafjallajokull 1 volcanic lightning has intrigued observers through the centuries several likely processes have been proposed to explain the electrification of volcanic plumes including quenching magma water interactions the fracturing or internal friction of fine grained ash and the freezing of plume water at height scarce measurements of volcanic lightning have not been able to distinguish between proposed ideas the eyjafjallajokull volcanic eruption in iceland in april may 2010 may have revealed its charge mechanism during its 39 days the eruption went through a few phases while the conditions of the ambient atmosphere also changed but at different times the most surprising change in the lightning activity occurred on 11 may with no obvious change in the physical eruption character or strength during 3 10 may there was no lightning recorded by long range networks followed by intense activity 11 20 may the change in lightning activity coincided with a change in the conditions of the ambient atmosphere at this time the altitude of the isotherms for droplet freezing about 20 c dropped drastically below the plume top therefore it appears that the atmospheric conditions around the plume were influencing or even controlling some of the lightning activity the critical plume top temperature which appears to have turned on and off the observed lightning activity during the eyjafjallajokull eruption is estimated to be between 20 and 24 c we conclude that a significant charge generation process of the observed volcanic lightning is probably analogous to processes in meteorological thunderclouds

megafauna from the late pleistocene holocene deposits of the upper ribeira karst area southeast brazil abstract the carbonate caves of the upper ribeira valley southeastern sao paulo state brazil preserve an abundant fossil record of pleistocene holocene south american megafauna nevertheless in comparison with other localities of the country its paleontological knowledge still can be considered sparse and in need of further research this work presents an update taxonomic survey of the megafauna material collected since the beginning of the explorations in the area based on this it discusses paleobiogeographic and paleoecological questions the fossil megafauna of the upper ribeira karst region include eremotherium laurillardi nothrotherium maquinense lestodon armatus catonyx cuvieri ocnopus gracilis ahytherium aff aureum glyptodon clavipes g reticulatus hoplophorus cf toxodon spp stegomastodon waringi equidae hippidion cf tapirus terrestris panthera onca and smilodon populator only p onca and t terrestris still remain in the region despite the occurrence of some typical taxa of the pampean paleobiogeographical province the fossil assemblage recorded shows greater affinity to the mega mammal community of the intertropical region the ecology of species found suggests the previous occurrence of fairly different environmental settings than the existing one in the area there were more temperate climates both dry and wet until the current mesophytic forest was finally established the studied material does not show any kind of chrono correlation given the type of genesis of the cave accumulations these fossils depict different faunistic moments related to climate changes during the quaternary to better understand the information provided by these deposits efforts on dating and detailed taphonomic investigations should be conducted the studies of the quaternary fauna in the state of sao paulo fill an important gap in the intricate biogeographical history of the south american megafauna

characterisation of post depositional taphonomic processes in the accumulation of mammals in a pitfall cave deposit from southeastern australia mceachern s deathtrap cave g49 50 is a classic pitfall trap located in southeastern australia which has been collecting terrestrial animals since the late quaternary dispersal and breakage of fossil bone elements are recognised as dominant taphonomic processes the sedimentary sequence contained within the cave consists of an upper and lower sequence where two distinct types of bone modification are identified the degree of bone breakage gradually increases with depth and is attributed to sediment compression and trampling minor in situ breakage has occurred as a result of rock fall and or trampling bone dispersal processes are indicated by a deficit in element representation required to account for whole skeletons based on mni calculations bone elements that are easily transportable by flowing water have a low frequency of representation in the sedimentary sequence in the cave floor bone lag deposit shallow intermittent flowing water is suggested by the dominance of transverse limb orientations and the low frequency of stable orientations that only occur in the most sensitive flow indicators e g pelves

localization and possible social aggregation in the late pleistocene and early holocene on the north coast of peru abstract early circular living structures made of rough field stone radiocarbon dated between 10 800 and 8300 bp and probably affiliated with the paijan culture on the north coast of peru are discussed in terms of possible proto household economies that are localized and socially aggregated in compressed environmental zones along the lower western slopes of the andes the technological settlement and economic data recovered from several sites in the zana and jequetepeque valleys are discussed briefly their broader implications are presented as well

sims u pb zircon ages and ni mo pge geochemistry of the lower cambrian niutitang formation in south china constraints on ni mo pge mineralization and stratigraphic correlations abstract in comparison with previous studies on the ni mo pge ore deposits within the deep water lower cambrian black shales of the niutitang formation around hunan and guizhou provinces this study focused on the shallow water ni mo pge enriched layer of the niutitang formation around hubei province by means of an integrated geochronological pge ree and trace element geochemical study the results suggest the ni mo pge enriched layer has a dominant seawater origin whereas the ni mo pge ore deposits have mixed seawater hydrothermal and terrigenous origins trace metals precipitated from ambient seawater under anoxic suboxic settings at exceedingly slow sedimentation rates with episodic injections of fresh oxidized seawater organic matter played an important role in sourcing transporting and precipitating trace metals however decay of organic material by means of sulfate reducing reactions and or fluid reworking overprinted primary relationships with trace metal contents however the positive linear relationships are clearly shown between organic carbon and trace metal contents new sims u pb ages constrained the depositional age of the ni mo pge enriched layer to be 532 527 ma which argues against previous assumption that the anoxic event recorded in the ni mo pge took place at the ediacaran cambrian boundary furthermore new radiometric ages suggest the shuijingtuo niutitang formation could be correlated with shiyantou formation dahai and upper zhongyicun members whereas yanjiahe formation correlated with daibu and lower zhongyicun members in yunnan province respectively

lapa das boleiras rockshelter stratigraphy and formation processes at a paleoamerican site in central brazil abstract lapa das boleiras rockshelter a paleoamerican archaeological site in central brazil was intensely occupied by humans from 10 000 14c bp 11 8 cal kyr bp until approximately 7500 14c bp 8 4 cal kyr bp in this paper we present some interpretations about the formation processes operating on the site one of our main conclusions is that the bulk of accumulated sediments at the site is of anthropogenic origin they are constituted by volumetrically significant quantities of plant ash remains what is somewhat unexpectedly in view of prevailing models about the lifestyle of paleoamerican hunter gatherers in south america the evidence we discuss below is also consistent with paleoenvironmental data that suggest a dry period during the mid holocene in the region probably leading to a decrease in human occupation araujo a g m neves w pilo l b atui j p 2005 holocene dryness and human occupation in brazil during the archaic gap quaternary research 64 298 307 we surmise that both factors underpin a surprising reduction in sediment accumulation at the site during the mid holocene

gold and platinum in shales with evidence against extraterrestrial sources of metals abstract few black shales contain concentrations of precious metals higher than average continental crust i e 5 ppb au yet au and pt alloys have been reported from the kupferschiefer in poland moreover thin sulfide beds in certain chinese and canadian shales contain several hundred ppb au pd and pt and average 4 mo and 2 5 ni in an association that is difficult to explain volcanic and non volcanic exhalations hydrothermal epigenesis involving either igneous or sedex fluids biogenic processes and low temperature secondary enrichment are among the possible factors involved in deriving ni pge and au for black shales and sulfide beds in black shales extraterrestrial sources have been invoked in some cases e g the cambrian of china however available data on abundances of pge indicate relatively low values for ir

comments on an anthropogenic modification in an eremotherium tooth from northeastern brazil over150yearsago peterw lundproposedthatlatequaternaryextinct megafauna henceforth just megafauna and homo sapienscoexisted in brazil lund 1844 but only recently his hypothesiswas supported by direct radiocarbon dating on megafauna bones neves and pilo 2003 hubbe et al 2007 2009 2011 these datesshowed that in some brazilian regions at least some speciessurvived until the beginning of the holocene and became extinctafter the arrival of the rst human groups besides the chronolog ical evidence which indicates that humans and megafauna lived inthe same region at the same time there are also claims that theymayhaveinteractedmoreactivelybasedonthe ndingofsingle orvery few bones or bone fragments associated with human occu pation levels near archeological material or showing marks thatsuggest their usage by humans however based on the meticulousrevision provided by prous 2002 it is possible to rule out most ofthese cases due to theircontroversial nature in fact few of those ifany can be held as solid evidence of this close interaction notconsidering scavengingon bones from a long ago deceased animal prous and fogaca 1999 recently dantas et al in press reported the nding of a singletooth fragment of the ground sloth eremotherium in sergipe state northeastern brazil that according to the authors presentsanthropogenic marks that favor the coexistence of this species andh sapiens however in our opinion their work does not providesolid evidence of an interaction of this nature and therefore theaim of this comment is to discuss the validity of their nding asreliable evidence of megafauna more speci cally eremotherium and humans coexistence in sergipe the coexistence and notablythe close interaction between the former and the later may haveimportant implications to the understanding of the initial humanoccupation of south america hence this kind of nding should notbe taken as granted but rather should be analyzed with rigorouscriteria in the following comments we question the interpretationof the marks seen in the tooth as human made cutmarks based on1 thenatureandlocationofthecutmarksand2 thearchaeologicalandpaleontologicalcontextof the nding furthermore wediscussreasons why the conclusions based on this nding could beseverely distorted dantas et al in press 1 described the marks found on thereported tooth as an effort to build a triangular object based onthe material the location of the marks and the scant informationprovided e g it is notclear if morebones fromeremotheriumwerefound if there are more bones from other species with marks whichother species were found it is hardtoaccept that the marksobserved are the result of human intervention on the tooth themarks are described by dantas et al in press 1 as being humanbecause they have parallel grooved striations narrower anddeeper which follow the curvature of the tooth along apical andlateral borders unfortunately these characteristics are unclear tous in the pictures presented by the authors fig 2f shows onlystriations fig 2g appear to show microwear striations when thescaleofthephoto 0 1mm istakenintoaccount andfig 2hshowsa network of shallow striations that crisscross the surface in everydirection in summary it is not possible to see the diagnosticfeatures in the pictures presented by the authors to justify theirconclusions of an anthropogenic origin for them added to the diagnostic dif culties of the marks in this tooth their occurrence is not in accordance to the standard patternsobserved for food processing in ethnographic and archaeologicalcontexts e g walker 1978 lupo 2002 lyman 2005 martinez 2009 thus diminishing the possibility of butchering marks onthis tooth indeed dantas et al in press never claimed thesemarks were the result of butchering however it is very hard to

insights into holocene megafauna survival and extinction in southeastern brazil from new ams 14 c dates abstract the extinction of late quaternary megafauna in south america has been extensively debated in past decades the majority of the hypotheses explaining this phenomenon argue that the extinction was the result of human activities environmental changes or even synergism between the two although still limited a good chronological framework is imperative to discuss the plausibility of the available hypotheses here we present six new direct ams 14 c radiocarbon dates from the state of sao paulo brazil to further characterize the chronological distribution of extinct fauna in this part of south america the new dates make evident that ground sloths toxodonts and saber toothed cats lived in the region around the pleistocene holocene transition and in agreement with previous studies also suggest an early holocene survival for the ground sloth catonyx cuvieri taken together with local paleoclimatic and archaeological data the new dates do not support hunting or indirect human activities as a major cause for megafauna extinction although more data are required parsimony suggests that climatic changes played a major role in this extinction event

u series dating and taphonomy of quaternary vertebrates from brazilian caves abstract the geochronology and taphonomy of internationally important fossil bearing cave deposits were studied both in the semi arid northern bahia area and the subtropical southeastern lagoa santa area of brazil taphonomic analysis suggests that the processes responsible for bone accumulation in the brazilian caves vary between sites and taphonomic bias can therefore be significant in causing differences in faunal composition in the toca da boa vista caves the presence of single articulated skeletons and the entrance related distribution indicate that random penetration of animals is the main mechanism of fossil accumulation a process that biases the assemblage to smaller species and takes place over extended time periods in nearby toca dos ossos cave transport by runoff in the cave river is predominant and biases the fauna remains to larger more robust bones and species deposition probably also occurred only at times of enhanced runoff giving a more contemporaneous assemblage similar processes were responsible for emplacement of the copious fossil remains in the more humid lagoa santa area where terrigenous fossil deposits are found intercalated by massive speleothem calcite layers in this area runoff under a drier climate probably accounts for the sediment emplacement inside caves in both areas the mode of emplacement implies bias in the fossil record resulting in fossil assemblages that do not mirror surface faunas limiting palaeoenvironmental reconstruction mass spectrometric u series analysis of speleothem calcite overlaying fossil remains gives minimum ages for fossil deposition these ages confirm the previous view that many of the deposits derive from the late glacial but also show that much older material some 350 000 yr is also present the habitat requirements of critical fossil species such as bats and monkeys strongly suggest that they derive from much wetter periods when forest cover was present in the currently semi arid northern bahia area taphonomy exerts a major control on the diversity and mode of emplacement of cave fossil deposits in eastern brazil and thus detailed sedimentological and hydrological studies coupled with a sound geochronological approach are essential in quantifying the relative importance of each taphonomic processes before faunal and palaeoecological interpretations can be attempted

volcanic plume monitoring using atmospheric electric potential gradients by monitoring perturbations of the natural atmospheric electric potential gradient it is possible to detect and track particle laden volcanic plumes the perturbations are produced by electrical charge that resides on the solid particles and liquid droplets of the plume and the ions within it a network of potential gradient monitoring stations around a volcano can provide data on eruption time magnitude plume dispersion direction and areas of ashfall our laboratory experiments have produced electrically charged ash by fragmenting pumice these results support the theory that charging is due to the magma fragmentation process and should therefore be ubiquitous in all particulate volcanic plumes

measurements of electric charge distribution in volcanic plumes at sakurajima volcano japan measurements of perturbations in the atmospheric potential gradient around volcanic plumes at multiple from two to five sites and measurements of the charge mass ratio of ash particles falling from volcanic plumes were carried out at sakurajima volcano japan results from 28 and 29 october 1995 show that the nature of the perturbations depends on the intensity of plume activity although plume activity was vigorous on 28 october negative perturbations were predominant as plume activity peaked the magnitude of negative perturbations decreased just below the plume and increased at an off axis site during the peak period positively charged ash particles fell out from the plume this suggests that the active plume dominantly contained negatively charged materials and that positively and negatively charged materials were added to the lower and upper parts of the plume respectively during the peak period on the other hand as plume activity became less vigorous on 29 october the perturbations were characterized by a positive anomaly followed by a negative anomaly because wind velocity increased with altitude that day we infer that positive and negative charges were distributed in the upper and lower parts of the plume respectively the differences in perturbations observed on 28 and 29 october suggest that volcanic plumes are generally composed of three parts an upper part with positively charged gas and aerosol a middle part with negatively charged fine ash particles and a lower part with positively charged coarse ash particles the compilation of present and previous results from sakurajima and other volcanoes indicates that the effect of the negative charge in the middle part was predominant in most cases although positive perturbations caused by the upper part were observed around some weak plumes the effect of positively charged particles in the lower part was observable only when plume activity was sufficiently strong because positively charged coarse particles tended to fall out near the vent

submarine hydrothermal contribution for the extreme element accumulation during the early cambrian south china throughout the geological history of the earth submarine hydrothermal activity has played an important role in seawater chemistry biological evolution and enrichment of metals in the earth crust however the prospect of hydrothermal activity for extreme element accumulation during the early cambrian a key geological period in south china has not been well constrained this study reports geochemical e g ree and sr isotope investigations of a coarse grained limestone layer and associated calcite veins in zunyi and nayong areas guizhou province to constrain the hydrothermal activity and evaluate the significance of hydrothermal contribution to extreme element accumulation during the early cambrian south china our results reveal positive eu anomalies and higher initial 87sr 86sr ratios 0 7083 0 7150 for carbonate samples than those of early cambrian seawater indicating the presence of hydrothermal processes combined with constraints from the spatial relationships and coincidence with adjacent mineralization these hydrothermal processes provide the most probable contribution for polymetallic ni mo pge mineralization furthermore there are abundant hydrothermal dolomite and barite calcite veins in the dolostone of the dengying formation indicating the occurrence of a variety of hydrothermal fluids overall multi stage hydrothermal pulses with different fluid compositions spanned the ediacaran cambrian transition in south china in particular these hydrothermal fluids with positive eu anomalies and enriched radiogenic sr originating from proterozoic mafic ultramafic rocks may have flowed through the underlying precambrian silicate clastic rocks e g xiajiang banxi and lengjiaxi groups and may have been crucial for the marine environment biological diversity and extreme element accumulation during the early cambrian south china

geochemical investigation of the lower cambrian mineralised black shales of south china and the late devonian nick deposit canada abstract lower cambrian tommotian black shales of the niutitang formation south china host a thin accumulation 5 20 cm of ni mo platinum group elements pge au ni as zn cu v and rare earth elements ree of all known deposits the late devonian ni mo pge sulphide horizon in black shales of the nick deposit selwyn basin in canadian yukon presents the strongest similarity with the niutitang formation polymetallic layer in the present study samples of the mineralised layer and host shales in south china from two mine sites zunyi and sancha were investigated in order to further characterise the prevailing redox conditions and mechanisms involved in the metal concentration process at both sites additional comparison with the nick deposit mineralised layer was also undertaken bulk geochemical analysis including pge analysis were conducted on all samples along with m scale investigation of metal distributions and associations by x ray fluorescence xrf mapping and synchrotron xrf mapping the comparison of the two sites from south china highlights strong similarities in metal enrichment factors pge and ree distribution patterns are also highly similar and suggest a source from seawater strong variations in elemental distributions at m scale were observed at both sites most likely related to intense variations in redox conditions in the sediment the comparison with the nick deposit highlights a stronger enrichment in ni and zn in the nick deposit and a greater variety of minerals in the niutitang shales the pge and ree distributions of both the nick deposit and the niutitang shales however present highly similar patterns and support an origin from seawater the present study provides further insight into mineralisation style and processes in these mineralised black shales highlighting the importance of redox conditions and re emphasizing the role of organic matter in the formation of these mineralised layers

the brazilian megamastofauna of the pleistocene holocene transition and its relationship with the early human settlement of the continent abstract one of the most intriguing questions regarding the brazilian late quaternary extinct megafauna and homo sapiens is to what extent they coexisted and how humans could have contributed to the former s extinction the aim of this article is to review the chronological and archaeological evidences of their coexistence in brazil and to evaluate the degree of direct interaction between them critical assessment of the brazilian megafauna chronological data shows that several of the late pleistoscene early holocene dates available so far cannot be considered reliable but the few that do suggest that at least two species catonyx cuvieri ground sloth smilodon populator saber toothed cat survived until the beginning of the holocene in southeast brazil archaeological data indicates that the first human groups arrived in brazil and were inhabiting this region during the last millennia of the pleistocene and consequently they coexisted with the extinct fauna in some parts of brazil for at least one thousand years there is no robust evidence favoring any kind of direct interaction between humans and megafauna prior to their extinction to date it is not possible to properly judge the indirect influence of humans landscape transformation introduction of predators among others in this extinction event intense and to some extent unique climate changes between the last glacial maximum and the holocene favors the interpretation that they had a major contribution to the megafauna extinction although the scarcity of data impedes the proper testing of this hypothesis

a c mos2 mixed layer phase mosc occurring in metalliferous black shales from southern china and new data on jordisite a new phase composed mainly of mo s and c and referred to herein as mosc occurs widely in organic rich metalliferous cambrian black shales in south china mosc which has previously been referred to as jordisite has been studied by scanning electron microscopy sem electron microprobe analysis empa transmission electron microscopy tem powder x ray diffraction xrd extended x ray absorption fine structure exafs and catalytic activity tem data show mosc to have a layered structure with packets resembling molybdenite and graphite like carbon that average five layers in thickness analytical data are consistent with an idealized formula of mo3s6c10 but it commonly contains 1 3 wt each of fe ni and as so that its composition may be better approximated by the formula mo fe ni 3 s as 6c10 selected area electron diffraction saed patterns show a small number of broad inhomogeneous rings corresponding to randomly oriented layers arranged in subspherical cells a single broad weak peak corresponds to a 10 11 a layer spacing in powder xrd diffraction patterns pseudomorphism after fossil bacteria implies an origin by replacement of sedimentary organic material in its chemical properties and structure mosc resembles synthetic compounds used as catalysts for hydrodesulfurization hds in the petrochemical industry the large surface to volume ratio for mosc may be an important factor in its relatively strong hds catalytic activity cotype samples of jordisite from germany previously thought to be amorphous mos2 were also studied by sem and tem jordisite occurs as sequences of a few curved layers that form sub spherical units with an appearance remarkably like that of mosc however the layer spacing is 6 a like that of molybdenite the ratio of mo s is 1 2 and no carbon was detected although it coexists with kerogen jordisite is thus confirmed to be a form of mos2 but because powder diffraction like saed patterns were obtained it is not amorphous

characterization of trace elements and carbon isotopes across the ediacaran cambrian boundary in anhui province south china implications for stratigraphy and paleoenvironment reconstruction abstract characteristics of redox sensitive elements and organic carbon isotopes of a drilling section covering the ediacaran cambrian e c boundary at anhui province south china were studied total organic carbon toc organic carbon isotope values of organic compounds abundances of mo v u and ni and ratios of v v ni and th u co vary across the section suggesting that the redox condition is the main factor controlling carbon isotope values of organic matter and sequestration of trace elements the e c boundary is characterized by the lowest organic carbon isotope and the highest ratios of mo toc v toc and u toc in the section which are correlated with reported carbon isotope excursions in other regions this is the first time that signatures of mo v and u in the hetang formation at the lower yangtze platform are used for stratigraphic correlations the results highlight abnormally high ratios of mo toc v toc and u toc near the e c boundary petrological and geochemical characteristics in this section suggests that intense upwelling activities during the e c transition may be the main contributor to 13 c depleted co 2 and enrichment of trace metals the co existing pervasive transgression led to ocean anoxia and facilitated the preservation of 13 c depleted organic matter and trace metal sequestration furthermore oxidation of the bottom ocean water may have completed during the early cambrian a combination of these factors may be among the reasons for significant evolutionary changes during the e c transition

sedimentary characteristics and origin of dolomitic ooids of the terminal ediacaran dengying formation at yulin chongqing south china abstract the ediacaran was a crucial transition period in the evolutionary history of the earth ediacaran ooids in the dengying formation from the yulin section in southwestern china are important archives of paleoenvironmental information although these ooids have been totally dolomitized the cortical fabric characteristics are locally preserved well indicating that these ooids were mimetically replaced the common occurrence of concentric radial fabrics and low level of sr concentrations 60 3 8 8 ppm in the studied ooid cortex is more likely suggestive of a primary low mg calcite mineralogy and that a calcite sea might exist during deposition of the second member of the dengying formation in situ geochemical data for the ooid cortices obtained by laser ablation inductively coupled plasma mass spectrometry show that these ooids have middle rare earth element enrichment prn smn 0 7 0 1 and smn ybn 1 5 0 4 and high fe contents 8200 1800 ppm this suggests ferruginous pore waters which were related to the selective or preferential absorption and release of rees by fe mn oxyhydroxides

electron spin resonance dating of the southern brazilian pleistocene mammals from touro passo formation and remarks on the geochronology fauna and palaeoenvironments abstract quaternary mammals from touro passo formation southern brazil rio grande do sul state were studied in the 1970s and assigned to the pleistocene holocene transition approximately between 13 000 and 3500 bp subsequent dating by thermoluminescence indicated that the sediments of this formation are older between 42 and 15 ka bp and ages obtained by ams in mollusks and 14c of charcoal ranged from 16 to 10 ka bp however none of these ages were obtained directly from vertebrates in this work four teeth samples of artiodactyla indet gomphoteriidae indet 2 samples called g1 and g2 and toxodon sp from ponte velha i locality touro passo creek were dated by electron spin resonance esr the results are 34 6 ka for artiodactyla 23 5 ka for g1 28 3 ka for g2 and 19 3 ka for toxodon sp the variation in the ages of the materials corroborates the hypothesis that the fossils of ponte velha i locality have been reworked the dating contributes to the chronology of the brazilian pleistocene mammals and corroborates the previous interpretations on the timing of deposition of touro passo formation during the late pleistocene

archaeology of the pleistocene holocene boundary in brazil abstract after a short history of brazilian research about pleistocene peopling the late pleistocene early holocene changes of climate and resources are discussed claims for a very ancient presence of man before 13 000 bp itaborai toca da esperanca pedra furada and lapa vermelha sites are polemic because putative structures and artifacts could have been made by natural processes in central and northeastern brazil some sites dated between 14 000 and 10 000 bp provide clear evidence of human activities and coexistence with huge pleistocene mammals in a synthesis of our present knowledge about the 12 000 8000 bp period biological aspects of the lagoa santa people and their subsistence are discussed the main regional traditions are umbu with bifacial projectile points and humaita with heavy implements in the southern part of brazil in the central and northeastern regions the itaparica tradition is characterized by typical retouched flakes and limaces although projectile points are generally thought to be absent in the earliest levels of this tradition some have been found in boquete cave in amazonia some cultural aspects seem to have been the same as in central brazil

magnetotelluric pulses generated by volcanic lightning at sakurajima volcano japan 1 continuous magnetotelluric mt measurements were conducted at sakurajima volcano japan revealing syn eruption electric pulses and sometimes accompanying geomagnetic pulses movies of the eruptions recorded with timing provided by a gps clock show a large number of volcanic lightning flashes some mt pulses occurred simultaneously with lightning flashes pulses were observed more than 10 seconds after the onset of the eruption and tend to occur during eruptions that emit volcanic ash to high altitudes pulses were more common during mild eruptions rather than during vulcanian eruptions the observations suggest that the dominant mechanism of volcanic lighting is similar to that of lightning in thunderstorms in that it requires the collision of particles and subsequent separation of positive and negative charge

ams 14c dating of early human occupation of southern south america the time of appearance of a persistent and demographically viable hunter gatherer population in late pleistocene southern south america must be determined by evaluating evidence from as large as possible a sample of candidate archaeological sites in the region we co ordinated the ams dating of multiple bone and charcoal samples from previously excavated strata at the following sites arroyo seco 2 paso otero 5 piedra museo and cueva tres tetas all in argentina and cueva del lago sofia 1 and tres arroyos both in chile with one possible exception we did not obtain new results to confirm earlier observations of pre clovis age cultural activity at any of the sites considered in this study the possible exception arroyo seco 2 is considered in detail elsewhere politis g gutierrez m a scabuzzo c eds in press estado actual de las investigaciones en el sitio 2 de arroyo seco region pampeana argentina serie monografica incuapa 5 olavarria however our results for the samples which were the most preferred indicators of cultural events hearth charcoal and cut marked bone confirm that people were in the southern cone of south america at or soon after 11 000 bp 13 000 cal bp considered alongside recent age estimates for the clovis culture in north america these results imply the contemporaneous emergence of a consistent and archaeologically robust human occupation signal at widely separated locations across the western hemisphere such findings suggest that palaeoindian demic expansion may have involved more than one terminal pleistocene dispersal episode c 2008 elsevier ltd all rights reserved

new u pb age from the basal niutitang formation in south china implications for diachronous development and condensation of stratigraphic units across the yangtze platform at the ediacaran cambrian transition abstract the black shale dominated niutitang formation covers a large portion of the early cambrian yangtze platform in south china the base of this unit has been traditionally taken as the ediacaran cambrian boundary ca 542 ma recent radiometric ages from the basal niutitang formation and its correlative units however are significantly younger than 542 ma and raise questions about the diachrony of stratigraphic units across the yangtze platform at the ediacaran cambrian transition here we report a new u pb sensitive high resolution ion microprobe shrimp age of 522 7 4 9 ma from a tuffaceous bed of the basal niutitang formation in a deep water section in taoying guizhou province of south china this age in combination with existing ages and biostratigraphic data suggests that the base of the niutitang formation is of tommotian or upper meishucunian age and the ediacaran cambrian boundary is most likely within the liuchapo formation the depositional age of the unusual metal enriched ni mo pge sulfide deposits which are approximately 1 m above the ca 523 ma tuffaceous bed should be early tommotian upper meishucunian rather than early nemakit daldynian lower meishucunian regional correlation confirms the diachronous development and condensation of stratigraphic units across the early cambrian yangtze platform and provides important information for understanding the paleogeography and paleoceanographic events at the ediacaran cambrian transition in south china

reconstruction of regional atmospheric circulation features during the late pleistocene in subtropical brazil from oxygen isotope composition of speleothems two high resolution oxygen isotope records of speleothems from caves located in subtropical brazil provide a broad view of regional climate variations and related forcing during the late pleistocene and holocene here we present a new record precisely dated by u series extending back to 131 kyr bp from a speleothem collected in santana cave comparison with the 116 kyr bp record from botuvera cave confirms that the seasonal change in regional rainfall distribution is primarily controlled by variations in summer insolation on milankovitch timescales however significant negative anomalies of 18 o from 60 kyr bp to 10 kyr bp in the records suggest that the northern hemisphere glacial boundary conditions in particular heinrich events impacted the mean location and or convective activity of the south american summer monsoon sasm resulting in enhanced transport of depleted moisture from the amazon basin into the region in addition comparison of the two records indicates a steep north south gradient in 18 o of rainfall throughout which is interpreted as reflecting different relative contribution of extratropical and monsoonal precipitation to the two locations for some time periods more pronounced negative 18 o anomalies occur in the northern part and more positive anomalies in the southern part of the region which appear to be associated with more abundant monsoonal and extratropical rainfall respectively the last interglacial period is characterized by the highest 18 o values in the entire st8 record indicating a dominance of extratropical winter rainfall and thus the most northward position of the summer sasm for the last 131 kyr bp 2006 elsevier b v all rights reserved

swelling of a lava plug associated with a vulcanian eruption at sakurajima volcano japan as revealed by infrasound record case study of the eruption on january 2 2007 in order to clarify the time relation of the expansion of a gas pocket and failure of its overlying plug of lava during vulcanian eruptions infrasound records and video images of the vulcanian eruption that occurred at sakurajima volcano on january 2 2007 were analyzed with respect to their origin times weak 3 pa and slowly increasing air pressure preceded the impulsive compression phase by 0 25 0 32 s and a longer period rarefaction phase of infrasound waves was recognized at all microphone stations the velocity of the compression phase was assumed to be supersonic ca 400 m s up to 850 m above the crater bottom from other recent explosions on the other hand the propagation velocity of the preceding weak signal was regarded to be similar to the air sound velocity because the lack of impulsiveness is unlikely to be related to the main compression phase therefore the estimated origin time of the main compression phase was delayed by 0 5 0 7 s from the preceding phase the origin time of the preceding phase coincided with the onset of the isotropic expansion process of the pressurized gas pocket which was obtained by the waveform inversion of the explosion earthquake in contrast the origin time of the main impulsive phase coincided with the time when the expansion rate reached its peak this observation suggests that the volumetric increase of the gas pocket caused swelling of the surface of the crater bottom and its subsequent failure when the expansion velocity exceeded a threshold level the main impulsive compression phase radiated with a high velocity by the sudden releases of the pressurized gases the volumetric change at the source was estimated to be 280 560 m3 from the preceding phase of the infrasound this volume change indicates that the vertical displacement of the swelling ground was on the order of 1 0 m assuming the radius of the lava plug was ca 10 m

changes to the turbulent kinematics of a volcanic plume inferred from lightning data the 2009 redoubt volcano eruption produced a series of explosive events the largest of which produced episodes of volcanic lightning similar to thunderstorms flash energy spectra were calculated from lightning mapping data collected during the eruption the spectra were compared to the turbulence characteristics expected from each stage of plume development small flash length scales present at early times were associated with the gas thrust and initial convective stages increases in flash length scales and flash energy as the explosive events progressed were associated with an increase in volume of the plume spectra with a large range in flash length scales 0 2 10 km and a spectral peak at small flash length scales 1 km were associated with a superposition of spectra from gas thrust convective and umbrella ash cloud regions an approximate 5 3 power law slope was observed on the order of 10 min after gas thrust forcing had ended and the transition to a drifting ash cloud was underway which may reflect the dissipating state of the drifting ash cloud

volcanic lightning global observations and constraints on source mechanisms lightning and electrification at volcanoes are important because they represent a hazard in their own right they are a component of the global electrical circuit and because they contribute to ash particle aggregation and modification within ash plumes the role of water substance water in all forms in particular has not been well studied here data are presented from a comprehensive global database of volcanic lightning lightning has been documented at 80 volcanoes in association with 212 eruptions the volcanic explosivity index vei could be determined for 177 eruptions eight percent of vei 3 5 eruptions have reported lightning and 10 of vei 6 but less than 2 of those with vei 1 2 these findings suggest consistent reporting for larger eruptions but either less lightning or possible under reporting for small eruptions ash plume heights 142 observations show a bimodal distribution with main peaks at 7 12 km and 1 4 km the former are similar to heights of typical thunderstorms and suggest involvement of water substance whereas the latter suggest other factors contributing to electrical behavior closer to the vent reporting of lightning is more common at night 56 and less common in daylight 44 reporting also varied substantially from year to year suggesting that a more systematic observational strategy is needed several weak trends in lightning occurrence based on magma composition were found the bimodal ash plume heights are obvious only for andesite to dacite basalt and basaltic andesite evenly span the range of heights and rhyolites are poorly represented the distributions of the latitudes of volcanoes with lightning and eruptions with lightning roughly mimic the distribution of all volcanoes which is generally flat with latitude meteorological lightning on the other hand is common in the tropics and decreases markedly with increasing latitude as the ability of the atmosphere to hold water decreases poleward this finding supports the idea that if lightning in large deep eruptions depends on water substance then the origin of the water is primarily magma and not entrainment from the surrounding atmosphere seasonal effects show that more eruptions with lightning were reported in winter bounded by the respective autumnal and vernal equinoxes than in summer this result also runs counter to the expectations based on entrainment of local water vapor

rhenium and osmium isotopes in black shales and ni mo pge rich sulfide layers yukon territory canada and hunan and guizhou provinces china rhenium and osmium abundances and osmium isotopic compositions were determined by negative thermal ionization mass spectrometry for samples of devonian black shale and an associated ni enriched sulfide layer from the yukon territory canada the same composition information was also obtained for samples of early cambrian ni mo rich sulfide layers hosted in black shale in guizhou and hunan provinces china this study was undertaken to constrain the origin of the pge enrichment in the sulfide layers samples of the ni sulfide layer from the yukon territory are highly enriched in re os and other pge with distinctly higher re 192os but similar pt re compared to the black shale host re os isotopic data of the black shale and the sulfide layer are approximately isochronous and the data plot close to reference isochrons which bracket the depositional age of the enclosing shales samples of the chinese sulfide layers are also highly enriched in re os and the other pge re 192os are lower than in the yukon sulfide layer re os isotopic data for the sulfide layers lie near a reference isochron with an age of 560 ma similar to the depositional age of the black shale host the osmium isotopic data suggest that re and pge enrichment of the brecciated sulfide layers in both the yukon territory and in southern china may have occurred near the time of sediment deposition or during early diagenesis during the middle to late devonian and early cambrian respectively

the dominance of an extant gregarious taxon in an attritional accumulation taphonomy and palaeoecological implications abstract a recurrent aspect of the fossil record is the observation of a disproportionate number of specimens or individuals of a single taxon in some deposits which is stated as dominance commonly the dominance is explained as the result of catastrophic or short term mass death events or are proxies for palaeoecological inferences regarding gregariousness however taphonomic stratigraphic and chronologic analyses of fossiliferous deposits have shown that this is not always true to contribute to the study of dominance in fossil assemblages we describe a probable quaternary skeletal accumulation dominated by the extant gregarious rock dwelling rodent kerodon rupestris recovered from sumidouro do sansao a 65 m deep pitfall cave in northeast brazil and discuss the palaeoecological implications of our findings we provide taxonomic identification taphonomic analyses and chronological assessment besides k rupestris minimum number of individuals mni 35 we recorded three taxonomic groups that are the ground sloth catonyx cuvieri mni 1 the anteater tamandua tetradactyla mni 1 and the cougar puma concolor mni 1 the taphonomic analysis of the k rupestris remains supports the idea that entrapment of individuals was the main process of bone accumulation and that the death of cave inhabitants followed by short transport to the main hall possibly occurred kerodon rupestris remains persisted on the surface of the cave deposit for different time spans and were exposed to fragmentation weathering invertebrate boring and encrustation inside the cave environment direct dating suggests differences in the ages obtained and intermittent deposition of the individuals inside the cave it highlights the influence of taphonomic controls on gregarious taxa such as k rupestris towards dominating attritional time averaged assemblages furthermore it demonstrates that such assemblages do not necessarily support inferences about single event mortality and gregariousness of the dominant taxon

physical properties of volcanic lightning constraints from magnetotelluric and video observations at sakurajima volcano japan abstract the lightning generated by explosive volcanic eruptions is of interest not only as a promising technique for monitoring volcanic activity but also for its broader implications and possible role in the origin of life on earth and its impact on the atmosphere and biosphere of the planet however at present the genetic mechanisms and physical properties of volcanic lightning remain poorly understood as compared to our understanding of thundercloud lightning here we present joint magnetotelluric mt data and video imagery that were used to investigate the physical properties of electrical discharges generated during explosive activity at sakurajima volcano japan and we compare these data with the characteristics of thundercloud lightning using two weeks of high sensitivity high sample rate mt data recorded in 2013 we detected weak electromagnetic signals radiated by volcanic lightning close to the crater by carefully inspecting all mt waveforms that synchronized with visible flashes and comparing with high speed 3000 frame s and normal speed 30 frame s videos we identified two types of discharges the first type consists of impulses type a and is interpreted as cloud to ground cg lightning the second type is characterized by weak electromagnetic variations with multiple peaks type b and is interpreted as intra cloud ic lightning in addition we observed a hybrid mt event wherein a continuous weak current accompanied type a discharge the observed features of volcanic lightning are similar to thunderstorm lightning and the physical characteristics show that volcanic lightning can be treated as a miniature version of thunderstorm lightning in many respects the overall duration length inter stroke interval peak current and charge transfer all exhibit values 1 2 orders of magnitude smaller than those of thunderstorm lightning thus suggesting a scaling relation between volcanic and thunderstorm lightning parameters that is independent of the type of charged particles on the other hand the polarities which are estimated by long time 3 4 yrs mt 32 samples s and video 30 frame s observations are different than those of normal thunderstorm lightning these observations are consistent with the notion that charge structures in volcanic ash plumes are highly disordered and are characterized by numerous small charged regions with high charge density

how marine incursion influences the quality of lacustrine source rocks the paleogene nanxiang basin eastern china the impact of marine incursions during transgression i e sea level rises and the shoreline moves landward on the formation and quality of lacustrine source rocks is an important and contentious issue in this study we present a case study of the paleogene hetaoyuan formation in the biyang sag nanxiang basin eastern china paleontological trace element and biomarker data indicate that the hetaoyuan source rocks in this region were influenced by a marine incursion the paleontological evidence indicates that the marine incursion resulted in the introduction of red and brown algae which commonly inhabit marine environments trace element analyses yielded representative evidence of marine incursion e g equivalent boron content 300 ppm and b ga ratio 4 2 biomarker evidence for marine incursion includes c26 c25 tricyclic terpanes ratios of 1 3 which is the threshold for distinguishing marine organic matter from lacustrine using the b ga ratio as a typical paleosalinity indicator it was determined that the influence of marine incursion decreased from the biye 1 to cheng 2 to an 3006 wells with the b ga ratio average decreasing from 7 51 to 6 81 to 3 73 respectively with an increasing extent of marine incursion e g distance landward overall water depth and marine freshwater mixing the primary productivity of organic matter increased and the preservational environment became more reducing these changes resulted in higher contents of organic matter total organic carbon e 2 8 wt and a more favorable type of organic matter for oil generation kerogen type i ii indicating that the marine incursion had a positive effect on the formation of source rocks therefore the formation mechanism of high quality source rocks in coastal lacustrine basins during high sea level periods and associated resource potential might need to be reevaluated e g the campanian lower neslen formation along the margins of the western interior seaway of north america and the terminal oligocene early miocene in the fluvial saldanha bay at the southwestern tip of africa the results also provide useful data for regional oil and gas exploration

experimental generation of volcanic lightning explosive volcanic eruptions are commonly associated with intense electrical activity and lightning direct measurement of the electric potential at the vent where the electric activity in the volcanic plume is first observed is severely impeded limiting progress in its investigation we have achieved volcanic lightning in the laboratory during rapid decompression experiments of gas particle mixtures under controlled conditions and recorded it using a high speed camera and two antennas we find that lightning is controlled by the dynamics of the particle laden jet and by the abundance of fine particles the relative movement of clusters of charged particles generates the electrical potential which is necessary for lightning the experimental generation of volcanic lightning suggests that rapid progress can now be expected in understanding electrical phenomena in volcanic plumes to implement lightning monitoring systems and the forecasting of volcanic ash emissions

micron scale distribution of metals in cambrian metalliferous shales south china insights into local biologically driven redox disequilibrium abstract early cambrian black shales of the niutitang formation are found across the yangtze platform in a 1600 km belt extending across south china a thin organic matter rich layer in the lowermost part of this formation contains exceptional concentrations in mo ni se re os as hg sb ag au pt pd and ag due to their extreme metal enrichment these black shales provide a rare opportunity to study the interface between semi metals metals and biogenic material we report the first detailed m scale investigation of metal distributions and associations in samples from two sites zunyi and sancha located hundreds of km apart using a combination of analytical techniques including x ray fluorescence xrf mapping scanning electron microscopy sem synchrotron based xrf mapping electron probe micro analyser epma particle induced x ray emission pixe probe and x ray absorption near edge structures xanes imaging strong m scale variations in metal and semi metal distributions were highlighted by synchrotron based xrf mapping of samples from both sites at both locations u is present within phosphorite nodules arsenic mo and se are particularly abundant in the organic rich matrix showing strong associations with organic matter nickel however shows different distributions between the two sites it is mainly present in association with the organic matter at the sancha site while it is found in abundance in millerite at the zunyi site suggesting slightly different local conditions at zunyi favouring ni s associations over ni organic matter at both sites biogenic structures were re mineralised with laminations dominated by different metals indicating a likely control of organic matter over metal distributions in addition the xanes imaging highlighted different redox states of as over m scale areas while as 1 appears to be mainly present in pyrite as 3 was mainly detected in association within the carbon and mos2 mixed layer phase mosc overall the present results emphasize the complexity of metal associations in this mineralised layer the significant role of organic matter in the accumulation and precipitation of metals and semi metals in these metalliferous shales and highlight how biogenic activity can induce m scale variations in redox conditions in sediments

the brazilian sea level curves a critical review with emphasis on the curves from the paranaguaand cananeia regions abstract relative sea level curves for the mid to late holocene have been proposed for eight different sectors along the brazilian coast this paper aims to review the data used to construct the curves proposed for two sectors the paranaguaand cananeia regions in southeast brazil more specifically we analyze the palaeo sea level indicators vermetid tubes shells wood fragments and shell midden deposits related to 1 the sea level maximum of the mid holocene and 2 the two secondary oscillations that would have occurred between 4100 3800 years b p and 3000 2700 years b p the sedimentary deposits of the coastal plain as well as vermetid datings suggest a mid holocene sea level maximum between 3 5 and 4 m the great majority of the indicators used to infer the secondary oscillations in previous studies were derived from shell middens besides being unreliable palaeo sea level indicators these data also showed inconsistencies that undermine the existence of such oscillations the plot of all the data derived from vermetid samples found along the brazilian coast also indicate a rather smoother sea level fall in the last 5100 years

organic clots and their differential accumulation of ni and mo within early cambrian black shale hosted polymetallic ni mo deposits zunyi south china abstract the celebrated early cambrian ni mo deposits that occur near zunyi city of guizhou province south china are hosted in shales the ore formation has been widely accepted to be related to biotic impact but direct evidence is still lacking in the present study of the huangjiawan ore deposit organic clots are found to occur widely in the ni mo ore beds but not in the barren layers the clots are generally elliptic with sizes ranging from 200 to 600 m the clot morphology is similar to that of modern rhodophyta as reported in the literature we tentatively interpret the clots as rhodophyte cystocarps electron microprobe analysis revealed that the clots have a differential accumulation of ni and mo with ni in the inner part and mo in the outer part of the cystocarp our study seems to have provided direct evidence for the biotic impact on the ore mineralization

hydrocarbon generation capability of sinian lower cambrian shale mudstone and carbonate rocks in the sichuan basin southwestern china implications for contributions to the giant sinian dengying natural gas accumulation the giant natural gas accumulation recently discovered within the neoproterozoic dengying formation in the sichuan basin of southwestern china represents a new and important supplement to the ancient neoproterozoic cambrian petroleum systems worldwide however the source of this gas is controversial because there are five possibilities based on geology from bottom to top including the lower sinian doushantuo mudstone the upper sinian dengying algal dolomite the mudstone of the third member of the dengying formation the lower cambrian maidiping argillaceous dolomite and the lower cambrian qiongzhusi shale to improve the understanding of this issue 33 samples from the five possible source rock units in the study area were investigated for their character and maturity via petrology total organic carbon toc pyrobitumen reflectance kerogen carbon isotope and biomarker analyses based on the results we address their hydrocarbon generation capabilities and contributions to the giant gas accumulation results show that present day toc values of the samples range from 0 03 to 2 36 and vary both regionally and stratigraphically with the qiongzhusi shales in the central basin and the weiyuan ziyang area ranking the highest in contrast the organic matter source and maturity within these rocks are relatively homogenous with slight variation throughout the study area the organic matter is predominantly derived from algae and bacteria with different compositions deposited in marine reducing environments the rocks range in thermal maturity from postmature to overmature these results imply that the generation capability of source rock had been high in the past and the gas in the study area is most likely originated from oil cracking and the late generation directly from the kerogen of source rocks with the qiongzhusi shales being the dominant source rock thus the hydrocarbon migration pattern in the study area is a lateral migration from deep seated and younger cambrian source rocks in sags to shallow seated and older sinian dolomite reservoirs in uplifts the migration process occurred in the oil phase with the oil being later cracked the differences in natural gas geochemistry may be controlled by complex factors e g thermal maturity the migration accumulation process and differing contributions from source rocks besides the dominant qiongzhusi regionally the central basin and the weiyuan ziyang area have had high hydrocarbon generation capability and thus should be considered as favorable targets for natural gas exploration in the future this study of china provides an additional example of neoproterozoic cambrian petroleum systems worldwide and thus can help to synthesize the systematics of such systems and understand the sedimentary transition across the precambrian cambrian boundary

fossil bats from the quaternary of serra da capivara northeast brazil abstract the serra da capivara national park in the southeast of state of piaui is widely recognized for its important archeological sites however in the areas surrounding the park there are also paleontological sites especially limestone caves where fossils of small mammals have been found this material was recovered from deposits attributed to the late pleistocene and early holocene previous works have listed the occurrence of eight species of bats in two caves toca do gordo do garrincho and toca da janela da barra do antoniao the present study reports new data on the chiroptera from serra da capivara based on cranio mandibular fragments from three caves from toca do barrigudo we identified tonatia sp phyllostomus discolor and artibeus planirostris the latter two species have also been identified from toca do serrote do artur in addition to lophostoma sp and eptesicus fuscus from toca do gordo do garrincho the record of desmodus rotundus is confirmed along with the identification of lophostoma sp thus the following taxa are recorded for the first time for the quaternary of the serra da capivara region lophostoma sp phyllostomus discolor and eptesicus fuscus all taxa currently occur in the area except eptesicus fuscus which has previously been recorded for the quaternary of brazil in the states of rio grande do sul and bahia suggesting a much wider geographical distribution at least until the beginning of the holocene which is corroborated by the serra da capivara findings