numerical model for sediment transport and bed degradation in the yangtze river channel downstream of three gorges reservoir this paper presents a two dimensional morphological model for unsteady flow and both suspended load and bed load transport of multiple grain size to simulate transport of graded sediments downstream from the three gorges reservoir the model system includes a hydrodynamic module and a sediment module the hydrodynamic module is based on the depth averaged shallow water equations in orthogonal curvilinear coordinates the sediment module describing nonuniform sediment transport is developed to include nonequilibrium transport processes bed deformation and bed material sorting the model was calibrated using field observations through application to a 63 km long alluvial river channel on the middle yangtze river in china a total of 16 size groups and a loose layer method of three sublayers were considered for the transport of the nonuniform bed materials in a long term simulation predictions are compared with preliminary results of field observations and factors affecting the reliability of the simulated results are discussed the results may be helpful to the development of more accurate simulation models in the future

raman microspectroscopy of funginite from the upper silesian coal basin poland abstract raman spectral characteristics of funginite were compared with that of fusinite and semifusinite from the same coals inertinite concentrates prepared from four samples of coking coals from the upper silesian coal basin of poland were examined the examination reveals that funginite spectral characteristics have common features with that of fusinite or to smaller extent to semifusinite this suggests that the high reflectance of funginite might result from charring during wildfire activity

geophysical geological transect and tectonic evolution of the swiss italian alps a complete alpine cross section integrates numerous seismic reflection and refraction profiles across and along strike with published and new field data the deepest parts of the profile are constrained by geophysical data only while structural features at intermediate levels are largely depicted according to the results of three dimensional models making use of seismic and field geological data the geometry of the highest structural levels is constrained by classical along strike projections of field data parallel to the pronounced easterly axial dip of all tectonic units because the transect is placed close to the western erosional margin of the austroalpine nappes of the eastern alps it contains all the major tectonic units of the alps a model for the tectonic evolution along the transect is proposed in the form of scaled and area balanced profile sketches shortening within the austroalpine nappes is testimony of a separate cretaceous age orogenic event west directed thrusting in these units is related to westward propagation of a thrust wedge resulting from continental collision along the meliata hallstatt ocean further to the east considerable amounts of oceanic and continental crustal material were subducted during tertiary orogeny which involved some 500 km of n s convergence between europe and apulia consequently only a very small percentage of this crustal material is preserved within the nappes depicted in the transect postcollisional shortening is characterized by the simultaneous activity of gently dipping north directed detachments and steeply inclined south directed detachments both detachments nucleating at the interface between lower and upper crust large scale wedging of the adriatic or apulian lower crust into a gap opening between the subduced european lower crust and the pile of thin upper crustal flakes alpine nappes indicates a relatively strong lower crust and detachment between upper and lower crust

differential zooplankton aggregation due to relative vorticity in a semi enclosed bay abstract the relationship between a mesoscale cyclonic eddy and the abundance and distribution of zooplankton in the bay of la paz gulf of california in the summer of 2009 is presented the water density distribution the geostrophic current velocity and the vertical component of relative vorticity indicate a mesoscale cyclonic eddy located in the alfonso basin with a diameter of 30 km the zooplankton trophic groups along the bay presented a radial distribution using a bray curtis similarity cluster analysis three different zones were delimited 1 the alfonso basin where the cyclonic eddy is centered 2 the strip from southern bay to the boca grande which is the periphery of the eddy and 3 outside the bay the results indicated that the mesoscale cyclonic eddy might be the dominant physical feature influencing the horizontal distribution of the different trophic groups of zooplankton in the bay of la paz our results confirm that the mesoscale cyclonic eddy retains a biological composition that is markedly different from that of its surroundings zooplankton biomass was substantially higher inside the eddy than at its periphery however outside the bay the biomass was comparable to that found in the center of the eddy the trophic group composition exhibits a predominance of herbivorous zooplankton in the center of the eddy a predominance of omnivorous zooplankton in its periphery and a high abundance of carnivorous zooplankton in the region adjacent to the gulf of california

wind driven nutrient and subsurface chlorophyll a enhancement in the bay of la paz gulf of california abstract nutrient and chlorophyll a distributions in the bay of la paz gulf of california mexico were analyzed during the late spring of 2004 to assess their relations to hydrography and circulation patterns the results show the presence of both gulf of california water and subtropical subsurface water water circulation was dominated by wind stress driven cyclonic circulation along f h contours f is planetary vorticity and h is depth and upwelling resulting from the divergence shows a vertical velocity of 0 4 m d 1 nutrient concentrations were higher in the center of the cyclonic pattern where a rise in the nutricline contributed nutrients to the euphotic layer as a result of ekman pumping the vertical section showed the presence of a chlorophyll a maximum at the thermocline shoaling to a depth of only 12 m along the surface two peaks of chlorophyll a were observed one at boca grande and another off san juan de la costa associated with upwelling and mixing derived from current interactions with abrupt topographies the chlorophyll a maximum increased from 0 8 mg m 3 in the external part of the cyclonic pattern to 2 0 mg m 3 in its center the vertically integrated chlorophyll a concentrations followed a similar pattern rising from 10 to 20 mg m 2 and reaching their highest values in the center of the cyclonic circulation pattern a schematic model was developed to describe processes that occur in late spring the wind stress driven cyclonic structure promotes upward nutrient flux which in turn drives an enhancement of chlorophyll a upwelling was found to be the main mechanism of fertilization responsible for the enhancement of productivity levels by means of nutrient transport into the euphotic zone during spring other chlorophyll enhancement areas point to the occurrence of additional fertilization processes that may derive from interactions between cyclonic circulation patterns and the topography off of san juan de la costa where phosphate mining occurs

numerical modeling of bed deformation in laboratory channels a depth average model using a finite volume method with boundary fitted grids has been developed to calculate bed deformation in alluvial channels the model system consists of an unsteady hydrodynamic module a sediment transport module and a bed deformation module the hydrodynamic module is based on the two dimensional shallow water equations the sediment transport module is comprised of semiempirical models of suspended load and nonequilibrium bedload the bed deformation module is based on the mass balance for sediment the secondary flow transport effects are taken into account by adjusting the dimensionless diffusivity coefficient in the depth average version of the k e turbulence model a quasi three dimensional flow approach is used to simulate the effect of secondary flows due to channel curvature on bed load transport the effects of bed slope on the rate and direction of bed load transport are also taken into account the developed model has been validated by computing the scour hole and the

oxidation of methane at the ch4 h2o co2 transition zone in the external part of the central alps switzerland evidence from stable isotope investigations abstract with the aim of understanding the mechanisms that control the metamorphic transition from the ch 4 to the h 2 o co 2 dominated fluid zone in the helvetic domain of the central alps of switzerland fluid inclusions in quartz illite crystallinity index vitrinite reflectance and the stable isotope compositions of vein and whole rock minerals and fluids trapped in quartz were investigated along four cross sections increasing temperature during prograde metamorphism led to the formation of dry gas by hydrocarbon cracking in the ch 4 zone fluid immiscibility in the h 2 o ch 4 co 2 nacl system resulted in cogenetic ch 4 and h 2 o dominated fluid inclusions in the ch 4 zone fluids were trapped at temperatures 270 5 c the end of the ch 4 zone is marked by a sudden increase of co 2 content in the gas phase of fluid inclusions at temperatures 270 5 c in the h 2 o zone the total amount of volatiles within the fluid decreased below 1 mol with no immiscibility this resulted in total homogenization temperatures of h 2 o co 2 ch 4 nacl inclusions below 180 c hydrogen isotope compositions of methane in fluid inclusion have d values of less than 100 in the ch 4 zone typical for an origin through cracking of higher hydrocarbons but where the methane has not equilibrated with the pore water d values of fluid inclusion water are around 40 in isotopic equilibrium with phyllosilicates of the whole rocks within the ch 4 to h 2 o co 2 transition zone d h 2 o values in fluid inclusions decrease to 130 interpreted to reflect the contribution of deuterium depleted water from methane oxidation in the h 2 o zone d h 2 o values increase again towards an average of 30 which is again consistent with isotopic equilibrium with host rock phyllosilicates 13 c values of methane in fluid inclusions from the ch 4 zone are around 27 in isotopic equilibrium with calcite in veins and whole rocks the 13 c ch 4 values decrease to less than 35 at the transition to the h 2 o zone and are no longer in equilibrium with the carbonates in the whole rocks 13 c values of co 2 are variable but too low to be in equilibrium with the wall rock fluids compatible with a contribution of co 2 from closed system oxidation of methane differences in isotopic composition between host rock and alpine fissure carbonate are generally small suggesting that the amount of co 2 produced by oxidation of methane was small compared to the c budget in the rocks and local pore fluids were buffered by the wall rocks during precipitation of calcite within the fissures

pressure dependence of graphitization implications for rapid recrystallization of carbonaceous material in a subduction zone we report the results of kinetic experiments of graphitization at various pressures 0 5 8 0 gpa and durations 1 s to 24 h at 1200 c the natural carbonaceous material in sedimentary rocks from the shimanto accretionary complex and the hidaka metamorphic belt japan underwent systematic changes in crystallinity and morphology with increasing pressure to assess the pressure dependence of graphitization we adopted three approaches to formulating the graphitization kinetics using a power law rate model a johnson mehl avrami kolmogorov model and a superposition method activation volumes of 21 7 3 0 to 45 7 4 5 cm3 mol 1 and 0 7 0 2 to 16 8 1 8 cm3 mol 1 were obtained for pressures from 0 5 to 2 0 gpa and 2 0 to 8 0 gpa respectively such large negative activation volumes might arise from structural modification and compression in the primary carbonaceous material we applied the experimental data to the arrhenius type equation of graphitization extrapolated to geological p t t conditions our model predicts that carbonaceous material undergoing metamorphism for 10 myr at pressures of 0 5 3 0 gpa will begin to crystallize at around 350 420 c and transform fully to ordered graphite at around 450 600 c depending on the peak pressure thus natural graphitization might proceed much more rapidly than previously estimated owing to the large negative activation volumes for the reaction rate this indicates that subducted carbonaceous materials will completely convert to fully ordered graphite by rapid recrystallization and metamorphic devolatilization before reaching sub arc depths 100 km

cooling induced strain localization in carbonate mylonites within a large scale shear zone glarus thrust switzerland abstract the glarus thrust switzerland offers a great field example of strain localization under retrograde conditions along the thrust mylonitic microfabrics are characterized by a temperature stress controlled balance of grain size reducing mechanisms and grain growth consequently mean grain sizes decrease along the thrust with decreasing metamorphic conditions and towards the thrust contact in an opposite manner calcite twin densities increase towards the contact cpos are strongest between 0 5 and 15 m away from the thrust but become generally weaker in the last centimeters where also cataclasites occur the cpo weakening and grain size reduction towards the shear zone point to a change from predominant dislocation creep to granular flow finally ending in cataclastic deformation the microfabric changes correlate with a decrease in 13c and 18o towards the thrust contact indicating the presence of fluids during cycles of brittle and plastic deformation based on the microfabric changes variations in stable isotopes and cross cut relationships a subdivision into a low and high temperature shear zone can be made the microfabric modifications resulted from changes in deformation conditions due to ongoing thrusting and exhumation induced cooling promoting further strain localization of an existing high strain shear zone

evolution of the raman spectrum of carbonaceous material in low grade metasediments of the glarus alps switzerland terra nova 22 354 360 2010 abstract the raman spectrum of carbonaceous material cm from advanced diagenesis 200 c to low grade metamorphism 320 c is documented in the helvetic flysch of the glarus alps switzerland the spectrum is complex with several defect bands at 1200 d4 1350 d1 1500 d3 and 1620 d2 cm 1 we document the evolution of these bands relative to the graphite g band with increasing metamorphic grade and we show that this qualitative evolution may be used as a proxy for temperature in the glarus alps we develop a robust peak fitting method and propose quantitative parameters that may be used as proxies for thermal metamorphism in this region further work in other geological contexts is needed to assess whether the spectral evolution observed in the glarus alps may be generalized and to critically assess the potential for calibrating a general empirical and quantitative thermometer based on the raman spectrum of cm in low grade rocks

mesozooplankton biomass and grazing responses to cyclone opal a subtropical mesoscale eddy as part of e flux iii cruise studies in march 2005 plankton net collections were made to assess the effects of a cyclonic cold core eddy cyclone opal on the biomass and grazing of mesozooplankton mesozooplankton biomass in the central region of cyclone opal an area of uplifted nutricline and a subsurface diatom bloom averaged 0 8070 24 and 1 5170 59 g dw m 2 for day and night tows respectively these biomass estimates were about 80 higher than control out stations with increases more or less proportionately distributed among size classes from 0 2 to 45 mm though elevated relative to surrounding waters south of the hawaiian islands hawai i lee total biomass and size distribution in cyclone opal were almost exactly the same as contemporary measurements made at stn aloha 100 km north of the islands by the hot hawaii ocean time series program mesozooplankton biomass and community composition at the out stations were also similar to aloha values from 1994 to 1996 preceding a recent decadal increase these comparisons may therefore provide insight into production characteristics or biomass gradients associated with decadal changes at stn aloha gut fluorescence estimates were higher in opal than in ambient waters

three dimensional computation of flow around groyne the three dimensional 3d numerical simulation of a steady shallow turbulent flow around a groyne in a rectangular channel is presented a method used to track a moving surface boundary and to follow its evolution using a one phase 3d reynolds solver with rigid grids by means of a transient fraction of fluid or porosity field is applied some results are compared with experimental data such as the isolines of water depths and the mean velocity field a comparison of the reattachment length prediction using the free surface model and the rigid lid assumption is given other results concerning the pressure field turbulence or shear stress distribution are presented and analyzed

extending the applicability of the raman carbonaceous material geothermometer using data from contact metamorphic rocks the degree of graphitization of carbonaceous material cm has been widely used as an indicator of metamorphic grade previous work has demonstrated that peak metamorphic temperature t o f regional metamorphic rocks can be estimated by an area ratio r2 of peaks recognized in raman spectra of cm the applicability of this method to low pressure 50 that adequately reflects the range of sample heterogeneity using this procedure with 532 nm laser and adapting our new calibration the errors of the raman cm geothermometer for contact metamorphic rocks decrease to 30 c

three dimensional numerical model for flow and bed deformation around river hydraulic structures this paper describes a numerical model developed to simulate flow and bed deformation around river hydraulic structures the model solved the fully three dimensional reynolds averaged navier stokes equation expressed in a moving boundary fitted coordinate system to calculate the flow field with water and bed surfaces varying in time a nonlinear k e turbulence model was employed in order to predict flow near the structure where three dimensional flow is dominant the temporal change in bed topography was calculated by coupling a stochastic model for sediment pickup and deposition using a momentum equation of sediment particles in order to account for the effect of nonequilibrium sediment transport in validating the numerical model a spur dike and a bridge pier which are considered to be typical river engineering structures were selected by comparing the numerical results with observed laboratory experimental data the model was found to reproduce flow and scour geometry around these structures with

very low grade metamorphism of the taveyanne greywacke glarus alps switzerland detailed textural and chemical data for mineral assemblages on a regional scale are presented for the metaandesitic eocene oligocene taveyanne greywacke of the glarus alps eastern switzerland presented data indicate an increase of metamorphic grade from zeolite facies to prehnite pumpellyite and pumpellyite actinolite facies low grade outcrops contain laumontite minor corrensite and pumpellyite assemblage type 1 whereas outcrops of higher metamorphic grade contain prehnite and two populations of pumpellyite type 2 prehnite pumpellyite al white mica type 3 a single outcrop shows pumpellyite actinolite facies type 4 from the zeolite to prehnite pumpellyite pumpellyite actinolite facies there are indications for an increase of the chemical equilibrium domain size for the critical paragenesis from a single detrital grain 1 mm in type 1 to a few millimetres in type 2 and to a whole thin section in type 3 metamorphic p t conditions were determined by a combination of chlorite thermometry fluid inclusion and vitrinite reflectance data peak temperatures range from 170 190d c for zeolite facies to 270 310d c for prehnite pumpellyite and pumpellyite actinolite facies for the higher temperature range pressures of 2 3 kbar are derived indicating a geothermal gradient of 24 32d c km 1 the well constrained temperature estimations derived for the assemblages provide a useful test of the different empirical calibrations of chlorite thermometers recently proposed the best correspondence to the temperatures determined here is for the cathelineau calibration in addition in the lower grade samples differences in textures and calculated temperatures provide a mean to distinguish between detrital and newly formed chlorites

laminated sediments in the bay of la paz gulf of california a depositional cycle regulated by pluvial flux core bap96 cp sampled from the deepest part of the bay of la paz gulf of california has been analysed sedimentologically taking into account regional climate and oceanography laminated sediments at the bottom of the bay are essentially not bioturbated by benthic fauna a subanoxic condition o 2 0 2 ml l 1 inhibits the proliferation of benthic fauna within the bay the relative abundances of terrigenous and biogenic inputs change periodically the terrigenous input is greater than the biogenic input and apparently experiences larger fluctuations the terrigenous input dominates in dark laminae whereas the biogenic input mostly occurs in light laminae thus it is assumed that down the core the alternation of dark and light laminae represents cycles in the extent of dilution of the biogenic input by terrigenous input the terrigenous input into the bay of la paz is mostly regulated by pluvial runoff thus its temporal fluctuation follows the periods shown by the regional pluvial regime particularly the 11 2 year period this is equal to the frequency of sunspot cycles

raman spectra of carbonaceous material in metasediments a new geothermometer metasedimentary rocks generally contain carbonaceous material cm deriving from the evolution of organic matter originally present in the host sedimentary rock during metamorphic processes this organic matter is progressively transformed into graphite s s and the degree of organisation of cm is known as a reliable indicator of metamorphic grade in this study the degree of organisation of cm was systematically characterised by raman microspectroscopy across several mesozoic and cenozoic reference metamorphic belts this degree of organisation including within sample heterogeneity was quantified by the relative area of the defect band r2 ratio the results from the schistes lustres western alps and sanbagawa japan cross sections show that 1 even through simple visual inspection changes in the cm raman spectrum appear sensitive to variations of metamorphic grade 2 there is an excellent agreement between the r2 values calculated for the two sections when considering samples with an equivalent metamorphic grade and 3 the evolution of the r2 ratio with metamorphic grade is controlled by temperature t along the tinos cross section greece which is characterised by a strong gradient of greenschist facies overprint on eclogite facies rocks the r2 ratio is nearly constant consequently the degree of organisation of cm is not affected by the retrogression and records peak metamorphic conditions more generally analysis of 54 samples representative of high temperature low pressure to high pressure low temperature metamorphic gradients shows that there is a linear correlation between the r2 ratio and the peak temperature t c 445 r2 641 whatever the metamorphic gradient and probably the organic precursor the raman spectrum of cm can therefore be used as a geothermometer of the maximum temperature conditions reached during regional metamorphism temperature can be estimated to 50 c in the range 330 650 c a few technical indications are given for optimal application

sediment transport modeling review current and future developments the use of computational models for solving sediment transport and fate problems is relatively recent compared with the use of physical models several considerations govern the choice between physical and computational models namely the nature of the problem that needs to be solved the available resources and the overall cost associated with the problem solution in some specific problems a combination of physical and computational models can be used to obtain a better understanding of the processes under investigation de vries 1973 using computational hydrodynamic sediment transport models in general involves the numerical solution of one or more of the governing differential equations of continuity momentum and energy of fluid along with the differential equation for sediment continuity an advantage of computational models is that they can be adapted to different physical domains more easily than physical models which are typically constructed to represent site specific conditions another advantage of computational models is that they are not subject to distortion effects of physical models when a solution can be obtained for the same flow conditions identical reynolds and froude numbers same length scale in the three directions etc as those present in the field with the rapid developments in numerical methods for fluid mechanics computational modeling has become an attractive tool for studying flow sediment transport and associated pollutant fate processes in such different environments as rivers lakes and coastal areas representative processes in these environments include bed aggradation and degradation bank failure local scour around structures formation of river bends fining coarsening and armoring of streambeds transport of point source and nonpoint

proterozoic ocean redox and biogeochemical stasis the partial pressure of oxygen in earth s atmosphere has increased dramatically through time and this increase is thought to have occurred in two rapid steps at both ends of the proterozoic eon 2 5 0 543 ga however the trajectory and mechanisms of earth s oxygenation are still poorly constrained and little is known regarding attendant changes in ocean ventilation and seafloor redox we have a particularly poor understanding of ocean chemistry during the mid proterozoic 1 8 0 8 ga given the coupling between redox sensitive trace element cycles and planktonic productivity various models for mid proterozoic ocean chemistry imply different effects on the biogeochemical cycling of major and trace nutrients with potential ecological constraints on emerging eukaryotic life here we exploit the differing redox behavior of molybdenum and chromium to provide constraints on seafloor redox evolution by coupling a large database of sedimentary metal enrichments to a mass balance model that includes spatially variant metal burial rates we find that the metal enrichment record implies a proterozoic deep ocean characterized by pervasive anoxia relative to the phanerozoic at least 30 40 of modern seafloor area but a relatively small extent of euxinic anoxic and sulfidic seafloor less than 1 10 of modern seafloor area our model suggests that the oceanic mo reservoir is extremely sensitive to perturbations in the extent of sulfidic seafloor and that the record of mo and chromium enrichments through time is consistent with the possibility of a mo n colimited marine biosphere during many periods of earth s history

numerical model for channel flow and morphological change studies in this paper a depth integrated 2d hydrodynamic and sediment transport model cche2d is presented it can be used to study steady and unsteady free surface flow sediment transport and morphological processes in natural rivers the efficient element method is applied to discretize the governing equations and the time marching technique is used for temporal variations the moving boundaries were treated by locating the wet and dry nodes automatically in the cases of simulating unsteady flows with changing free surface elevation in channels with irregular bed and bank topography two eddy viscosity models a depth averaged parabolic model and a depth averaged mixing length model are used as turbulent closures channel morphological changes are computed with considerations of the effects of bed slope and the secondary flow in curved channels physical model data have been used to verify this model with satisfactory results the feasibility studies of simulating morphological formation in meandering chan

structure and origin of the gold mineralization in the nacimiento block the los burros deposits central california abstract the los burros gold deposit is located within the franciscan complex of the nacimiento block california although this deposit was mined during the late 19th and early 20th centuries its origin and its relationship with the regional metamorphism and deformation are unclear in order to better understand the mode of formation of the deposit and its possible link with a post subduction thermal anomaly we performed a detailed geological and structural mapping within the los burros district coupled with a u th he thermochronological study on apatite and zircon fluid inclusion and stable isotope o and c analyses of the ore deposit provide constraints on the temperature and potential source of the fluid s responsible for the los burros gold formation our results demonstrate that the los burros au deposit formed from a metamorphic aqueous co2 ch4 fluid at temperatures of 300 c results from raman spectroscopy of carbonaceous materials confirm the presence of a thermal anomaly in the range 260 320 c near the los burros mining district as previously inferred by vitrinite reflectance techniques our structural and preliminary thermochronological analyses show that the los burros au deposit consists of a series of meter wide quartz calcite sulfide en echelon veins formed during a late transpressive event related to san andreas fault activity and the subduction of a slab window during the past 30 ma our new data suggest that the thermal anomaly recorded in the vicinity of the los burros mining district is not associated with a magmatic derived hydrothermal system such as described within the epithermal mclaughlin deposit in northern california but rather with a late transpressive deformation event that uplifted deeply buried metamorphic rocks possibly connected to a local metamorphic overprint

shortening of the axial zone pyrenees shortening sequence upper crustal mylonites and crustal strength abstract the strength of the lithosphere may be constrained qualitatively by field observations on localized vs distributed modes of deformation and by the mineral assemblages formed during deformation the internal deformation of the bielsa basement unit of the pyrenean axial zone is investigated through structural microstructural and thermometric data in this area shortening is widely distributed as attested by the folded attitude of the interface between the basement and its sedimentary triassic cover shortening is estimated around 1 7 km 13 from a regional balanced cross section and should be considered in pre pyrenean reconstructions shortening probably occurred before strain localization on crustal ramps as suggested by zircon fission track analysis distributed shortening is characterized at small scale by low temperature mylonites and cataclasites in thin section feldspar originally present in the magmatic protolith is partially to totally sericitized this transformation led to significant weakening of the rock and took place in the 250 350 c temperature range sericitization is ubiquitous even in un deformed granodiorites this shows that the weakening effect of sericitization not only occurs in ultra mylonites ultra cataclasites and phyllonites but also more generally in the upper crust early during the shortening history with implications for the shortening style estimates of the geothermal gradient suggest that inherited thermicity may also have influenced the style of shortening we propose that the upper crust was very weak before or at the onset of its shortening due to high thermal gradients and fluid circulation that induced large scale sericitization in greenschist facies conditions this has strong implications on the rheological evolution of the upper crust submitted to metamorphic alteration in the greenschist facies and below

carbon isotopes as biogeochemical recorders of life over 3 8 ga of earth history evolution of a concept ever since pioneering studies in the late 1930s had shown that the conversion of inorganic carbon into biogenic substances entails sizeable redistributions of the stable carbon isotopes biologically mediated 13c 12c fractionations have come to be recognized as a common corollary of biochemical reactions meanwhile it is firmly established that the universal bias in favour of 12c characterizing biological materials primarily derives from a kinetic isotope effect that is imposed on the first carbon fixing enzymatic carboxylation reaction in the primary metabolism of co2 fixing autotrophic organisms this preference for 12c has turned out to be one of the most enduring relics of the ordered state of the biological precursor substances that may be preserved in fossil organics over billions of years with the currently known sedimentary record at hand it can be stated with confidence that biological carbon isotope fractionations have persisted throughout 3 8 ga of recorded earth history indicating that microbial prokaryotic and archaeoprokaryotic ecosystems had been prolific already on the archean earth while for the time span 3 5 ga the isotopic evidence is unequivocal the information encoded in the preceding record is commonly blurred by a metamorphic overprint this holds particularly for the metasediments of the 3 8 ga old isua supracrustal belt of west greenland which apart from widespread metasomatism have suffered amphibolite grade metamorphism it is known that 13c 12c exchange occurs in organic kerogenous rock constituents during both amphibolite and granulite facies metamorphism if a second carbon partner is available as either fluids or carbonate with isotopic re equilibration often only partially achieved due to the sluggish kinetics of the exchange reaction thermodynamic equilibria predict however that 13c 12c ratios in kerogen and graphite increase during this process hence high t exchange equilibria are always bound to drive 13c values in positive direction the lowermost values encountered being consequently the least exchanged and most pristine with the lowest values of reduced graphitic carbon obtained in early isua studies falling into the range 22 to 28 pdb we had straightforward evidence since the late 1970s that carbon constituents with the isotopic composition of biogenic matter were indeed present in the pre metamorphic isua suite it was therefore by no means surprising that the results of recent isotope work performed on apatite hosted carbonaceous microdomains in isua banded iron formation utilizing advanced techniques of instrumental microanalysis had prompted similar conclusions hence the mainstream of the sedimentary carbon isotope record can be best interpreted as the geochemical manifestation of the isotope discriminating properties of the principal co2 fixing reactions s in biological carbon assimilation suggesting an extreme degree of evolutionary conservatism in the biochemistry of autotrophic carbon fixation as a consequence biological modulation of the geochemical carbon cycle had been established at least 3 8 ga ago having been fully operative by the time of formation of the earth s oldest sediments

impact of biomineralization on the preservation of microorganisms during fossilization an experimental perspective abstract the biogenicity of fossil microbial biomorphs is often debated because their morphologies are poorly informative and the chemical structural and isotopic signatures of putative biogenic organic molecules have been altered during their incorporation into the sediments and the geological history of the host rock here we investigated the effect of encrustation by biominerals on the morphological and chemical degradation of escherichia coli cells during experimental thermal treatments non calcified e coli cells and e coli cells encrusted by calcium phosphates were exposed to heating under an argon atmosphere at two different temperatures 300 c 600 c for 20 h two additional experiments were performed on non calcified e coli cells at 300 c for 2 h and 100 h to discuss the influence of experiment duration organic residues of all experiments were characterized at a multiple length scale using a combination of scanning electron microscopy transmission electron microscopy raman microspectroscopy electron paramagnetic resonance epr spectroscopy fourier transform infrared ft ir spectroscopy and x ray absorption near edge structure spectroscopy xanes at the carbon k edge in the absence of encrusting biominerals the morphological structure of the organic residues of e coli cells was completely lost after heating at 300 or 600 c even after short 2 h long heating experiments the content of aromatic functional groups of the organic residues of non calcified e coli cells increased during heat treatment at 600 c for 20 h while the amide functional groups were lost as indicated by ft ir spectroscopy consistently the epr spectrum of these organic residues indicated important transformation as a comparison this spectrum appeared similar to epr spectra of ancient organic carbons such as carbons from the apex chert ca 3460 myr indicating a similar concentration of aromatic moieties in contrast calcified e coli exposed to the same conditions showed only limited morphological alteration as observed by electron microscopy as well as lower chemical transformation as detected by ft ir and epr spectroscopies despite the difficulties to relate experimental conditions directly to geological conditions these experiments evidence the influence of cell encrustation by minerals on their chemical and morphological preservation potential during fossilization processes

graphitization in a high pressure low temperature metamorphic gradient a raman microspectroscopy and hrtem study the graphitization of carbonaceous material cm in a high pressure metamorphic gradient is characterized along a cross section in the schistes lustres formation western alps along this 25 km cross section both the cm precursor and the host rock lithology are homogeneous and the prograde evolution of the pressure temperature metamorphic conditions from the lower blueschist facies 13 kbar 330 c to the eclogite facies 20 kbar 500 c is tightly constrained by literature data raman microspectroscopy shows that at the micrometre scale this process is progressive and continuous with increasing metamorphic grade and that the structure of cm is very sensitive to temperature variations at the nanometre scale hrtem the cm is composed of a mixture of a microporous phase and an onion ring like phase both known as non graphitizing under the effect of temperature at ambient pressure the hp lt graphitization produces structurally and microtexturally heterogeneous cm with increasing metamorphic grade the graphitization of the two types of cm proceeds up to the triperiodic graphite stage because of microtextural and structural changes that are specific to each type of cm the microporous material is progressively transformed into graphite through a macroporous transitional stage in this case graphitization mainly occurs on the pore walls as a result of pore growth in the case of concentric onion ring like material graphitization occurs in the regions with the largest radius of curvature i e on the outer part of the ring in comparison with 1 bar experiments pressure seems to induce microtextural changes which allows the subsequent structural modifications of the starting material

structural characterization of kerogen in 3 4 ga archaean cherts from the pilbara craton western australia hydrogen lean kerogen atomic h c 0 46 isolated from the 3 4 ga strelley pool chert in the north pole area pilbara craton western australia were studied by vibrational spectroscopy fourier transform infrared ftir spectroscopy and raman spectroscopy nuclear magnetic resonance spectroscopy solid state 13 c nmr spectroscopy catalytic hydropyrolysis followed by gas chromatography mass spectrometry hypy gc ms and isotope ratio mass spectrometry irms the kerogen occurs in sedimentary rocks as clasts and clots deposited together with other detrital materials that are finely disseminated throughout a chert matrix the bulk kerogen 13 c values range from 28 3 to 35 8 solid state 13 c nmr spectroscopy and ftir spectroscopy reveals that the kerogen is highly aromatic fa varying from 0 90 to 0 92 and contains only minor aliphatic carbon or carbon oxygenated c o functionalities the raman carbon first order spectra for the isolated kerogens are typical of spectra obtained from disordered sp 2 carbons with low 2 d ordering biperiodic structure the implications of the raman results show low 2 d ordering throughout the carbonaceous network indicate the incorrect usage of the term graphite in the literature to describe the kerogen or carbonaceous material in the warrawoona cherts hydropyrolysates contain aromatic compounds consisting of 1 ring to 7 ring polycyclic aromatic hydrocarbons which were covalently bound into the kerogen as well as alkanes linear branched and cyclic which were most probably trapped in the microporous network of the kerogen these pahs have mainly c1 and c2 alkylation while c3 substitued aromatics are low in abundance and do not show a high degree of branched alkylation for the first time we have shown a correlation between elemental analysis h c atomic ratios raman spectroscopic parameters id1 ig id1 id1 ig and la and the degree of alkylation of bound polyaromatic molecular constituents generated from hypy for archaean kerogens similarities in molecular

morphological modeling using a fully coupled total variation diminishing upwind biased centered scheme high resolution morphological modeling of fluvial processes with complex rapidly varying flows has been limited so far by model accuracy or computational efficiency one of the most widely used numerical algorithms is based on the total variation diminishing method solved by either upwind or centered approaches an upwind scheme preserves high accuracy but is complex and computationally demanding whereas the simplicity and efficiency of a centered approach compromise the accuracy the present paper extends a recent upwind biased centered scheme originally developed for clear water and scalar transport over a rigid bed to sediment laden flows over an erodible bed it does so by developing a fully coupled 2 d mathematical model using a finite volume method for structured grids the complete set of noncapacity based governing equations involving the effects of bed deformation and sediment density variation as well as the influences of turbulence and sediment diffusion and the temporal and spatial scales needed for sediment adaptation is solved at one time to obtain synchronous solutions for the entire computational domain for stability a two stage splitting approach together with a second order runge kutta method is employed for the source terms the model is verified in a number of tests covering a wide range of complex sediment laden flows the model is demonstrated to accurately simulate shock waves and reflection waves but also rapid bed deformations at high sediment transport rates the combination of high numerical accuracy and computational efficiency makes the model an important tool to forecast flood events in morphologically complex areas

stable and sr isotope evidence for fluid advection during thrusting of the glarus nappe swiss alps at the glarus thrust in the swiss helvetic alps permian verrucano siltstones are allochthonously superimposed over tertiary flysch with an intermediate about 1 metre thin layer of intensively deformed calcmylonite of probable mesozoic provenance the h o c and sr isotope compositions of minerals from the calc mylonite and strongly mylonitized verrucano siltstones were determined in order to assess 1 equilibrium disequilibrium relationships 2 isotopic composition of the fluid phase its provenance and water rock ratios 3 sources of sr in the calc mylonite 4 deformation temperatures the isotopic composition of cale mylonite micro samples from five sites along the thrust varies from 22 to 12 and 2 to 10 for 18o and 13c respectively all samples are 18o depleted by up to 14 relative to the presumed marine helvetic carbonate protoliths 18o 25 4 2 a pronounced geographic trend of 18o depletion from 22 in the north to 12 in the south is observed in calc mylonites 87sr 86sr ratios range from typical mesozoic marine carbonate protolith signatures 0 708 0 005 to more radiogenic values as high as 0 722 a variable contribution of radiogenic 87sr to the calc mylonite is though to reflect interaction with fluids that aquired their sr from the hercynian granitic basement chlorites and muscovites from the calc mylonite and verrucano have uniform 18o values but display d values from 40 to 147 the d enriched values correspond to the primary metamorphic or formational fluids expelled during thrusting whereas the d depleted samples reflect selective h isotope exchange with meteoric fluids during uplift of the alpine belt the isotopic composition of the calc mylonites requires exchange with 18o depleted 87sr enriched fluids at very high water rock ratios possible sources for these are dewatering of the underlying flysch and or metamorphic fluids or formation brines expelled along the thrust from greater depth these could be derived from compaction and dewatering of the flysch in the northern part of the thrust in the south however where verrucano is thrust over 18o rich mesozoic carbonates the extreme 18o depletion of the calc mylonite has to be explained either by fluid advection within the verrucano hanging wall and thrust zone or alternatively by exchange with metamorphic fluids from greater depth expelled along the thrust microstructural evidence abundant veins stylolites breccias suggests that fluids played an important role in deformation and strain localization excepting albite all major components quartz chlorite muscovite calcite are both dynamically recrystallized and crystallized as secondary minerals in pressure shadows and syn mylonitic veins indicating that these minerals were potentially open to oxygen isotopic exchange during alpine metamorphism and thrust deformation within the mylonitized verrucano silstones isolated quartz chlorite and quartz calcite fractionations yield temperatures of around 320 c close to values obtained from calcite dolomite thermometry 355 c 30 and in agreement with the regional lower greenschist facies metamorphism quartz calcite and quartz albite fractionations indicate slightly lower temperatures around 250 c owing to selective lower temperature re equilibration of the calcite and albite during post peak metamorphism

a billion years of environmental stability and the emergence of eukaryotes new data from northern australia carbon isotopes through 6km of fully cored drill holes in 1 7 to 1 5 ga carbonates of the mount isa and mcarthur basins australia which host the earliest known eukaryote biomarkers provide the most comprehensive and best dated delta 13c stratigraphy yet obtained from such ancient rocks both basins reveal remarkably stable temporal delta 13c trends mean of 0 6 2 pdb peedee belemnite and confirm the impression of delta 13c stasis between 2 0 and 1 0 ga which together with other evidence suggest a prolonged period of stability in crustal dynamics redox state of surface environments and planetary climate this delta 13c stasis is consistent with great stability in the carbon cycle controlled we suggest by p limitation of primary productivity recent evidence shows that p depletion is a major factor in obligate associations between photosymbionts and host cells we argue that a billion years of stability in the carbon and nutrient cycles may have been the driving force that propelled prokaryotes toward photosymbiosis and the emergence of the autotrophic eukaryote cell

retrieving shallow stream bathymetry from uav assisted rgb imagery using a geospatial regression method abstract bathymetric mapping is a prerequisite procedure to conduct assessments of water quality habitat and environmental flow for riverine ecosystems using hydraulic modelling this study evaluates the capability of a geographically weighted regression gwr model which can capture a spatially heterogeneous relationship between inputs and an output to retrieve bathymetry of a shallow stream of which water depth is less than about 1 m from simple rgb imagery a field experiment was performed for measuring water depth and simultaneously for acquiring remotely sensed data with rgb digital numbers dn using a digital camera mounted on an unmanned aerial vehicle uav a 2d shallow water model which was validated by comparison with the field surveyed data was used to simulate the water depth of unmeasured regions band ratios of ln dng dnr was selected as an optimal spectral input of bathymetric inversion models through the principal component analysis pca results showed that global inversion models based on multiple linear regression mlr and artificial neural network ann resulted in large discrepancy between estimation and observation due to the spatially varying response of the pca selected band ratio to water depth over the experimental channel in contrast the gwr model successfully alleviated the biases of the conventional models as r2 increased to 0 85 from 0 60 by accurately modelling the effect of spatial heterogeneity which arose from variable bottom types attributed to submerged vegetation on the remote sensing radiance water depth relationship

non hydrostatic finite element model for coastal wave processes abstract this paper presents the application of the depth integrated non hydrostatic finite element model cche2d nhwave wei and jia 2014 for simulating several types of coastal wave processes specifically the model is applied to 1 predict the swash zone hydrodynamics involving wave bore propagation 2 resolve wave propagation breaking and overtopping in fringing reef environments 3 study the vegetation effect on wave height reduction through both submerged and emergent vegetation zones using the drag force term technique and 4 simulate tsunami wave breaking in the nearshore zone and inundation in the coastal area satisfactory agreement between numerical results and benchmark data shows that the non hydrostatic model is capable of modeling a wide range of coastal wave processes furthermore thanks to its simple numerical formulation the non hydrostatic model also demonstrates a better computation efficiency when comparing with other numerical models

three dimensional numerical simulation and analysis of flows around a submerged weir in a channel bendway to improve navigation conditions for barges passing through river channels many submerged weirs sws have been installed along the bendways of many waterways by the u s army corps of engineers this paper presents results from three dimensional numerical simulations that were conducted to study the helical secondary current hsc and the near field flow distribution around one sw the simulated flow fields around a sw in a scale physical model were validated using experimental data the three dimensional flow fields around a sw the influence of the sw on general hsc and the implication of effectiveness of submerged weirs to realign the flow field and improve navigability in bendways were analyzed the numerical simulations indicated that the sw significantly altered the general hsc its presence induced a skewed pressure difference cross its top and a triangular shaped recirculation to the downstream side the over top flow tends to realign toward the inner bank and therefore improves conditions for navigation

on the quantification of the bed development time of alluvial meandering streams this paper concerns the quantitative evaluation of the time of bed development of alluvial meandering streams in agreement with the prevailing approach it is assumed that the stream centerline follows a sine generated curve the banks are rigid the flow is turbulent and subcritical and the flow width is much larger than the flow depth the movable bed is flat at time t 0 at t tb the bed reaches its equilibrium or developed state with the aid of dimensional and physical considerations an expression is found for the duration of bed development tb according to this expression tb is proportional to the square of the flow width b and inversely proportional to the specific volumetric bed load rate corresponding to the channel averaged flow the proportionality factor is found to be a function of the initial deflection angle 0 alone the form of this function is investigated on the basis of a series of experimental runs carried out by the writers in a sine generated channel having an intermediate

the structure of the helvetic nappes and its relation to the mechanical stratigraphy abstract this paper discusses structure and variations in structural style due to changes in mechanical stratigraphy of the helvetic nappes based on five cross sections the ratio n of the thickness of mechanically weak to the thickness of adjacent mechanically strong layers is of particular importance a low value of n favours imbricate thrusting and harmonic folding a high value favours detachment and disharmonic folding the transition at around n 0 5 is characterized by polyharmonic folding stratigraphic thickness variations due to local basin subsidence resulted in arcuate fold hinges and important plunges upon basin inversion lateral variations in the overall structure of the helvetic nappes is largely controlled by the initial irregular arrangements of the various small basins one more or less coherent thrust sheet the cretaceous stockwerk of the wildhorn drusberg santis nappe can be traced along the entire fold and thrust belt

a molecular and isotopic geochemical study of meso to neoproterozoic 1 73 0 85 ga sediments from the jixian section yanshan basin north china abstract this paper systematically describes the molecular and isotopic characteristics of meso to neoproterozoic 1 73 0 85 ga sediments from the jixian section yanshan basin north china a correlation is made between molecular fingerprints and paleoenvironmental and paleontologic data acquired from these strata the agreement between these parameters suggest that the biomarkers preserved in these proterozoic sediments are good indicators of the evolution of the paleoenvironment and early life in the yanshan basin the fact that extended regular isoprenoids c20 were detected in most of the studied samples suggest a sustained lipid input to sedimentary organic matter from halophiles and other possible archaebacteria through meso to neoproterozoic two dehydroabietin isomers i e 18 and 19 norabieta 8 11 13 trienes were unexpectedly present in these samples which provides evidence suggesting that the compounds with abieta structure could be derived from primitive organisms such as algae the stable carbon isotope characteristics of kerogen and coexisting carbonate show a rapid decline in atmospheric co2 concentration from 1 73 to1 58 ga and a stable concentration afterwards the difference c in isotopic composition between carbonate and associated kerogen lies in zonal variations along the stratigraphic sequence which can be attributed to the alternations of marine transgressions and regressions that occurred in the yanshan basin during the proterozoic the carbon isotope relationships between kerogen and alkanes from these strata are consistent with the hypothesis that before 1 4 ga both n alkanes and isoprenoids had been derived mainly from heterotrophic halophiles and other archaebacteria but after that only isoprenoids originated from archaebacteria whereas n alkanes were possibly derived from photosynthetic organisms changes in the source of n alkanes around 1 4 ga may suggest a decline of heterotrophic reworking to primary lipids which can be related to the formation of a quiet shallow water environment of an epicontinental sea at this stage in the yanshan basin

raman spectroscopic carbonaceous material thermometry of low grade metamorphic rocks calibration and application to tectonic exhumation in crete greece we present new raman spectra data of carbonaceous material cm to extend the range of the raman spectra of cm thermometer rscm to temperatures as low as 100 8c previous work has demonstrated that raman spectroscopy is an excellent tool to describe the degree of graphitization of cm a process that is independent of pressure but strongly dependent on metamorphic temperature a linear relationship between temperature and the raman parameter r2 derived from the area of the defect band relative to the ordered graphite band forms the basis of a previous thermometer because r2 shows little variability in low temperature samples 330 8c serves as a lower limit on the existing thermometer herein we present raman spectra from a suite of low temperature 100 to 300 8c samples from the olympics mountains and describe other aspects of the raman spectra of cm that vary over this range in particular the raman parameter r1 the ratio of heights of the disordered peak to ordered peak varies regularly between 100 and 350 8c these data together with published results from higher temperature rocks are used to calibrate a modified rscm thermometer applicable from 100 to 700 8c application to low grade metasediments in the otago region in the south island of new zealand gives temperatures consistent with previous estimates demonstrating the reliability of the modified rscm thermometer we apply the modified rscm thermometer to 53 samples from crete to evaluate the role of the cretan detachment fault in exhuming miocene high pressure low temperature metamorphic rocks exposed there the metamorphic rocks below the detachment the plattenkalk and phyllite quartzite units give metamorphic temperatures that range from 250 to 400 8c consistent with previous petrologic estimates we also demonstrate that the tripolitza unit which lies directly above the detachment gives an average metamorphic temperature of about 260 8c the modest break in metamorphic temperature in central crete indicates that the cretan detachment accounts for only 5 to 7 km of exhumation of the underlying hp lt metamorphic rocks which were initially accreted at 35 km we argue that the bulk of the exhumation 28 km out of 35 km total occurred by pervasive brittle stretching and erosion of structural units above the detachment d 2005 elsevier b v all rights reserved

carbonaceous biosignatures of diverse chemotrophic microbial communities from chert nodules of the ediacaran doushantuo formation the ediacaran doushantuo formation dst is renowned for exceptionally preserved precambrian fossils including metazoans some of these fossils particularly microfossils such as multicellular algae and acanthomorphic acritarchs are preserved in dst chert nodules to better understand the geomicrobiological processes that contributed to the authigenic formation of dst chert nodules and facilitated exceptional fossil preservation we analyzed organic matter in these chert nodules and the surrounding matrix calcareous mudstone using multiple in situ techniques confocal laser raman spectroscopy micro fourier transform infrared spectroscopy ftir and secondary ion mass spectroscopy sims we found strong ultrastructural chemical and isotopic heterogeneities in the organic matter as indicated by the raman spectral parameter i 1350 1600 ranging from 0 49 to 0 88 the infrared spectral index r3 2 from 0 12 to 0 90 and an estimated 13corg sims range of 44 v pdb these micron scale heterogeneities imply that the organic matter preserved in the dst chert nodules is derived from different carbonaceous sources in a diverse microbial ecosystem including eukaryotic and or prokaryotic photoautotrophs as well as chemotrophs involved in the fermentation and probably anaerobic oxidation of organic remains thus the microbial ecosystems in ediacaran ocean waters and sediments were more complex than previously thought and these microbial processes controlled dynamic micro environments in dst sediments where chert nodules were formed and fossils were mineralized the results also show that variations in the relative abundances activities and interactions of co existing microorganisms in dst sediments may have modulated 13corg shifts causing local decoupling between 13corg and 13ccarb as measured in bulk samples

biological markers in 1 7 billion year old rock from the tuanshanzi formation jixian strata section north china abstract n alkanes isoprenoids steranes hopanes and gammacerane have been found in a 1 7 ga old sedimentary rock 13c values of n alkanes are almost identical 30 1 whereas phytane and pristane have 13c values of 28 0 5 similar to those in modern sediments these compounds are also present in the kerogen thermolysis product indicating that they are indigenous

excellent source rocks discovered in the cryogenian interglacial deposits in south china geology geochemistry and hydrocarbon potential abstract the cryogenian 720 635 ma is characterized by the well known sturtian and marinoan glaciations which plays a key role in understanding remarkable climate and sea level changes and oxygenation events that occurred during the neoproterozoic era however less attention has been paid to the interglacial deposits recently we paid great attentions to the excellent hydrocarbon source rocks toc 2 in the cryogenian interglacial datangpo formation 663 4 ma 654 3 8 ma in south china which mainly consists of black shales with thin manganese interbeds making the interglacial interval a new focus to elucidate their characteristics and depositional environments petrological and geochemical studies were conducted on fresh rock samples collected from six sections gucheng sanlian xiaoxi gaodongyuan xiaochayuan yanglizhang in manganese mining areas at southeastern south china sedimentary reconstructions suggest a transition from restricted to open ocean environment during the deposition of the datangpo formation and this formation records variations from warm and humid to dry and cold climate black shales were deposited in its lowest member during the warm period and showed greatest thicknesses more than 20 m at depocenters microscopic observations of the black shale samples exhibited abundant benthic algae with great diversities indicating a gradual recovery of the ecosystem biomarker analyses further reveal that these algae combined with bacterial microorganisms prosperous in low salinity reducing environments were the dominant organic contributors to the source rocks which were inferred by low pristane pr to phytane ph ratio pr ph low gammacerane high tricyclic terpene and high c27 sterane contents trace element records combined with isotopic data suggest that the deposition of source rocks in datangpo formation were related to a burst in surface water productivity due to warm climate and better preservations resulted from anoxic waters within a stratified water column these findings indicate the cryogenian source rocks may provide a new potential field for future explorations of shale gas and deep oil and gas

mesoscale variability and nutrient phytoplankton distributions off central southern chile during the upwelling season the influence of mesoscale eddies abstract mesoscale features are recurrently found in the coastal transition zone ctz off central southern chile 35 40 s a region characterized by seasonal wind driven coastal upwelling in this study oceanographic data from two consecutive cruises carried out during the upwelling season january 2009 were combined with satellite time series data in order to characterize the structure and evolution of mesoscale eddies and to explore their influence on phytoplankton structure and nutrient distribution in the context of organic carbon exchanges between the coastal upwelling zone and the ctz two coastally generated contiguous mesoscale eddies 2 months old were characterized a surface cyclonic eddy cc1 and a subsurface anticyclonic eddy aa1 the distributions of salinity and dissolved oxygen together with nutrients suggested that both eddies were sites of vertical injection of high nutrient concentrations from the equatorial subsurface water mass essw into the upper layer in the ctz in addition eddy aa1 in combination with an upwelling plume was involved in the offshore advection of nutrients from the core of the essw located in the coastal zone at shallow depths

raman spectrum of carbonaceous material a possible metamorphic grade indicator for low grade metamorphic rocks raman spectral analyses of carbonaceous material cm extracted from pelitic samples along two sections traversing the metamorphic belt of taiwan were carried out in the present study the results show similar spectral variations of cm with metamorphic grade as those documented in the literature however continuous sampling from zeolite facies through prehnite pumpellyite facies to greenschist facies metamorphic rocks in the present study does reveal some interesting features on the raman spectra of cm that were not noted before both the raman d disordered o ordered peak area i e integrated intensity ratio and the d o peak width i e full width at half maximum fwhm ratio of the cm decrease with progressive metamorphism but the most prominent change in the d o peak area ratio occurs in samples of lower greenschist facies metamorphic grade while the most significant decrease in the d o peak width ratio occurs in samples near the boundary of prehnite pumpellyite facies and greenschist facies this phenomenon is interpreted as a result of the decoupling of the changing rates of in plane crystallite size and degree of defects of cm with progressive metamorphism it is postulated that the raman spectrum of cm can serve as a metamorphic grade indicator to distinguish samples of prehnite pumpellyite facies metamorphic grade from those of greenschist facies metamorphic grade

raman characterization of carbonaceous material in the macraes orogenic gold deposit and metasedimentary host rocks new zealand abstract raman spectroscopic and petrographic analyses were performed on samples collected from zones distal and proximal to the macraes gold deposit in the otago schist of new zealand to characterize the features and possible origins of carbonaceous material cm and to assess the potential role of cm in the formation of gold deposits cm is a common component in meta sedimentary orogenic gold deposits and it has been proposed that cm contributes to gold mineralization processes but the details of the mechanisms responsible are not fully understood documentation of the origins of the otago schist cm will improve our understanding of the role of cm in gold deposits this work has identified four types of cm of varying thermal maturity and origins from prehnite pumpellyite grade to lower greenschist grade samples in prehnite pumpellyite and pumpellyite actinolite grade rocks low maturity cm 1 coexists with framboidal pyrite indicating an in situ sedimentary origin with a potential association with the source of gold low crystallinity cm 2 is also found in low grade samples and is likely to have been deposited from fluids unrelated to gold mobilization cm 3 is the highest maturity cm recognized cm 3 is found in samples from the highest metamorphic grades studied lower greenschist facies where bands of cm 3 cross cut the foliation cm 3 is therefore thought to have been transported by fluids though possibly only at short length scales cm 4 is less mature than cm 3 and is found in mineralized rocks in association with sulfide minerals and gold cm 4 is likely to have a depositional origin but its precise role with respect to gold mineralization has not been identified

application of several depth averaged turbulence models to simulate flow in vertical slot fishways vertical slot fishways are hydraulic structures which allow the upstream migration of fish through obstructions in rivers the velocity water depth and turbulence fields are of great importance in order to allow the fish swimming through the fishway and therefore must be considered for design purposes the aim of this paper is to assess the possibility of using a two dimensional shallow water model coupled with a suitable turbulence model to compute the flow pattern and turbulence field in vertical slot fishways three depth averaged turbulence models of different complexity are used in the numerical simulations a mixing length model a k e model and an algebraic stress model the numerical results for the velocity water depth turbulent kinetic energy and reynolds stresses are compared with comprehensive experimental data for three different discharges covering the usual working conditions of vertical slot fishways the agreement between experimental and numerical data is very satisfactory the re

determination of the petrologic type of cv3 chondrites by raman spectroscopy of included organic matter abstract this paper reports the first reliable quantitative determination of the thermal metamorphism grade of a series of nine cv3 chondrites allende axtell bali mokoia grosnaja efremovka vigarano leoville and kaba the maturity of the organic matter in matrix determined by raman spectroscopy has been used as a powerful metamorphic tracer independent of the mineralogical context and extent of aqueous alteration this tracer has been used along with other metamorphic tracers such as fe zoning in type i chondrules of olivine phenocrysts presolar grain abundance and noble gas abundance bulk and p3 component the study shows that the petrologic types determined earlier by induced thermoluminescence were underestimated and suggests the following values pt allende axtell 3 6 pt bali mokoia grosnaja 3 6 pt efremovka leoville vigarano 3 1 3 4 pt kaba 3 1 the most commonly studied cv3 allende is also the most metamorphosed bali is a breccia containing clasts of different petrologic types the attribution suggested by this study is that of clasts of the highest petrologic types as pointed out by iom maturity and noble gas bulk abundance cv3 chondrites have complex asteroidal backgrounds with various degrees of aqueous alteration and or thermal metamorphism leading to complex mineralogical and petrologic patterns fe mg chemical zoning in olivine phenocrysts on the borders of type i chondrules of porphyritic olivine and pyroxene rich textural types has been found to correlate with the metamorphism grade this suggests that chemical zoning in some chondrules often interpreted as exchanges between chondrules and nebular gas may well have an asteroidal origin furthermore the compositional range of olivine matrix is controlled both by thermal metamorphism and aqueous alteration this does not support evidence of a nebular origin and does not necessarily mirror the metamorphism grade through fe mg equilibration on the other hand it may provide clues on the degree of aqueous alteration vs thermal metamorphism and on the timing of both processes in particular mokoia experienced significant aqueous alteration after the metamorphism peak whereas grosnaja which has similar metamorphism grade did not

mean flow and turbulence around a laboratory spur dike the three dimensional turbulent flow field around a spur dike in a plane fixed bed laboratory open channel was studied experimentally using a microacoustic doppler velocimeter mean and turbulence characteristics in all three spatial directions were evaluated at upstream and downstream cross sections near the dike results showed that the primary flow separated in both lateral and vertical directions two counter rotating flow circulations consisting of the lateral and vertical velocity components originated at the dike section downstream of the dike the circulation in the flow separation zone is stronger than the one in the contracted primary flow zone the maximum bed shear stresses estimated using reynolds stresses is about three times as large as the mean bed shear stress of incoming flow

microstructure specific carbon isotopic signatures of organic matter from 3 5 ga cherts of the pilbara craton support a biologic origin the 3 5 ga dresser formation from the north pole dome of the pilbara craton western australia contains some of the oldest evidence for life on earth here we present a detailed study of microstructure specific carbon isotopic composition of organic matter om preserved in dresser formation bedded cherts and hydrothermal chert vein using in situ secondary ion mass spectrometry sims the om in these rocks occurs mainly as clots that together with minor fine om layers and laminae are considered primary textures formed prior to host rock lithification other than rare om rich stylolites no evidence was found for later om migration beyond the micrometer scale average 13c om values in specific microstructural types range between 33 6 and 25 7 no correlation is seen between measured 13c values and h c ratios in the studied om microstructures this lack of correlation and the low metamorphic grade of the rocks studied argue against significant modification of om isotopic composition by later metamorphic alteration it is thus concluded that the range of 13c values found in the samples represents primary om isotopic variability within some individual samples variable 13c om values are correlated with specific microstructural types this observation is not consistent with solely abiotic om formation via fisher tropsch type reactions when compared with associated 13c ankerite values average 13c om values indicate c isotopic fractionation 13c ank om of 25 33 which translates to dissolved co2 om isotopic fractionation 13c co2 om of 20 30 this range of 13c co2 om is consistent with enzymatic c fixation via the calvin cycle utilized by photoautotrophs and the reductive acetyl coa pathway utilized by chemolithoautotrophs photosynthetic om formation is supported by the relatively shallow water depth inferred for the dresser environment and the restricted occurrence of stromatolites to shallow water deposits in this unit whereas chemolithosynthesis is supported by the abundance of om in sub seafloor hydrothermal chert veins the range of 13c om values observed in the samples may therefore represent the remains of different organisms utilizing different c fixation pathways other biologic effects such as the growth rate and density of microbial communities and further heterotrophic overprinting of the autotrophic biomass may have also contributed to the observed range of 13c om values

the evolution of illite to muscovite mineralogical and isotopic data from the glarus alps switzerland thirty five illite and muscovite concentrates were extracted from triassic and permian claystones shales slates and phyllites along a cross section from the diagenetic alpine foreland tabular jura and borehole samples beneath the molasse basin to the anchi and epimetamorphic helvetic zone of the central alps concentrates and thin sections were investigated by microscopic x ray infrared mossbauer thermal dta and tg wet chemical electron microprobe k ar rb sr 40ar 39ar and stable isotope methods with increasing metamorphic grade based on illite crystallinity data xrd and ir the following continuous changes are observed i the 1md 2m1 polymorph transformation is completed in the higher grade anchizone ii k2o increases from 6 8 wt diagenetic zone to 8 5 10 anchizone to 10 11 5 epizone reflecting an increase in the total negative layer charge from 1 2 to 2 0 iii a decrease of the chemical variation of the mica population with detrital muscovite surviving up to the anchizone epizone boundary iv a shift of an endothermic peak in differential thermal curves from 500 to 750 c v k ar and rb sr apparent ages of the fraction 2 m decrease from the diagenetic zone to the epizone k ar ages being generally lower than rb sr ages the critical temperature for total ar resetting is estimated to be 260 30 c k ar and rb sr ages become concordant when the anchizone epizone boundary is approached the stable isotope data on the other hand show no change with metamorphic grade but are dependent on stratigraphic age these results suggest that the prograde evolution from 1 md illite to 2m1 muscovite involves a continuous lattice restructuration without rupture of the tetrahedral and octahedral bonds and change of the hydroxyl radicals however this is not a recrystallization process this restructuration is completed approximately at the anchizone epizone boundary the isotopic data indicate significant diffusive loss of 40ar and 87sr prior to any observable lattice reorganization the restructuration progressively introduces a consistent repartition of ar and k in the mineral lattices and is outlined by the 40ar 39ar age spectra concordant k ar and rb sr ages of around 35 30 ma with concomitant concordant 40ar 39ar release spectra are representative for the main phase of alpine metamorphism calanda phase in the glarus alps a second age group between 25 and 20 ma can probably be attributed to movements along the glarus thrust ruchi phase while values down to 9 ma in regions with higher metamorphic conditions suggest thermal conditions persisting at least until the middle tortonian

mineral templated growth of natural graphite films abstract organic material in sediments is progressively altered during diagenesis and metamorphism leading to the formation of kerogen and ultimately crystalline graphite bulk carbonaceous material in metamorphic terrains typically has attained an overall degree of structural order that is in line with peak metamorphic temperature on a micron to nano scale however carbonaceous material can display strong structural variation the main factor that drives this variation is the chemical and molecular heterogeneity of the precursor biologic material specific conditions during metamorphism however can also play a role in shaping the microstructure of carbonaceous material here we describe the structural variation of carbonaceous material in rocks of the 2 0 ga zaonega formation karelia russia raman spectroscopy indicates that bulk carbonaceous matter in these rocks has experienced peak temperatures between 350 and 400 c consistent with greenschist facies metamorphism on a nano scale however a strong structural heterogeneity is observed transmission electron microscopy tem reveals the occurrence of thin films of highly ordered graphitic carbon at mineral surfaces these graphite films consisting of 20 100 individual layers completely envelop quartz crystals and occur on specific crystal surfaces of chlorite it is proposed that minerals can act as templates for the parallel ordering of carbon crystallites causing enhanced graphitization within narrow zones at mineral surfaces alternatively oriented organic precursor molecules could have been adsorbed onto charged mineral surfaces leading to thin graphitic films during later metamorphic heating episodes overall the presented observations demonstrate that mineral surfaces can initiate and accelerate localized graphitization of sedimentary organic material during metamorphism and therefore cause distinct nano scale variation in structural order

late cenozoic metamorphism and mountain building in taiwan a review abstract the orogenic wedge of taiwan results from the late miocene collision of the chinese passive margin and the luzon volcanic arc because of the southward propagation of the collision over time and because of its extreme rates of deformation and erosion it has appeared as an ideal place to investigate mountain building processes here we review existing metamorphic and thermochronological data on late cenozoic burial and exhumation most of the island has been extensively investigated in particular in terms of zircon or apatite fission track and u th he thermochronology peak metamorphic temperatures have also been quantified from the raman spectroscopy of carbonaceous material along three transects in central taiwan the different datasets appear consistent and indicate that cooling rates and exhumation are more intense within the hsueshan range and within the tananao complex lateral variations from south to north are also observed and they can be interpreted in terms of different stages of exhumation and mountain building existing models provide a framework to analyze the data and discuss the limits of some previous interpretations in particular in terms of exhumational steady state or of recent acceleration of uplift and exhumation these models are also discussed in light of available data it appears that all of them fit thermochronological data within the tananao complex whatever the kinematics the depth of the wedge or the mechanism responsible for exhumation and that exhumation of the hsueshan range has been ignored in most models future models need therefore to consider the taiwan wedge as a whole additional constraints on peak metamorphic conditions on kinematics of shortening and exhumation or on the geometry of the wedge at depth need to be gathered to further unravel mountain building processes at the scale of the whole orogen

differential distribution of diatoms and dinoflagellates in a cyclonic eddy confined in the bay of la paz gulf of california the differential distribution of diatoms and dinoflagellates in the bay of la paz gulf of california mexico was analyzed in summer of 2009 when a cyclonic eddy confined in the bay dominated the circulation an uplift of the nutricline in the eddy drove high concentrations of nutrients to the euphotic layer a differential phytoplankton distribution was observed to be associated with the eddy there was an abundance of dinoflagellates close to the center of the cyclonic eddy whereas diatoms were more abundant at the periphery a significant inverse correlation r 0 62 p 0 002 was found between the temperature at 25 m depth and the dinoflagellates abundance based on the temporal evolution of chlorophyll measured by modis satellite images and a conceptual model proposed for the lifecycle of eddies the cyclonic eddy may have been an old decaying structure the effect of the cyclonic eddy on the phytoplankton distribution in this small semienclosed region was apparently similar to that found in larger eddies in the open ocean but this is the first time such a differential distribution has been found associated to a confined eddy

carbonaceous biosignatures of the earliest putative macroscopic multicellular eukaryotes from 1630 ma tuanshanzi formation north china abstract the paleo and mesoproterozoic fossil record of multicellular eukaryotes is scarce but extremely important in studying the evolution of life in the precambrian era typically fossils heralded as multicellular eukaryotes that are older than the ediacaran are met with controversy to confront such debates we investigate the chemical isotopic and molecular structural characteristics of organic matter from carbonaceous compressions in the 1630 ma tuanshanzi formation in northern china some of the earliest putative macroscopic multicellular eukaryote fossils zhu and chen 1995 the large size and relative complexity of these fossils and similar remains from the 1 56 ga gaoyuzhuang formation have led to their interpretation as eukaryotes raman spectral parameters give an estimated peak metamorphic temperature tmax in the range of 202 286 c confirming the good preservation of the organic remains two dimensional raman maps of the carbonaceous compressions show ultrastructural variations that suggest diverse subcellular compounds being consistent with multicellular eukaryotes the organic matter has carbon isotopic composition 13corg sims between 45 3 and 32 2 and a branching index of carbon chain measured by the micro ftir spectral parameter r3 2 between 0 17 and 0 31 together with their large size and morphology the isotopic geochemical and ultrastructural data supports an interpretation of the tuanshanzi formation carbonaceous compressions as derived from phototrophic multicellular eukaryotic algae our data support the early evolution of macroscopic multicellular eukaryotes in the sulfidic and low oxygen conditions that prevailed in the paleo and mesoproterozoic oceans

rate of growth and other features of the temporal development of pool bar complexes in meandering streams despite substantial research on various aspects of bed deformation in meandering streams no systematic effort has yet been made to establish the timescales of the process additionally in past experiments as a rule the bed was not monitored throughout the development which has left undocumented essential features of the growth of meandering pool bar complexes in this paper an effort is made to penetrate some of these aspects more specifically the five laboratory runs presented by the writers in their 2009 paper in this journal are revisited with the following two objectives 1 to reveal the rate of growth of the resulting meandering pool bar complexes and 2 to document the extent if any of upstream or downstream migration of developing pool bar complexes in examples of sufficiently wide streams in which the bed deformation is primarily because of the convective behavior of flow the runs were conducted in a 70 sine generated channel having rigid banks in each run the bed was allowed to

deep hydrothermal activity driving the lusi mud eruption abstract the lusi mud eruption in east java continues unabated after more than a decade of activity as a pulsating geyser system bursting mud clasts water and gas the origin of the fluids and their properties at depth are not well constrained thus hampering our understanding and modelling of the system previous geochemical and geophysical studies show that lusi is a sediment hosted hydrothermal system with two sources of mud at depths between 0 3 2 km and another between 3 5 4 75 km here we present results of mineral thermometry using raman spectroscopy and chlorite composition on clasts erupted at lusi the results show that some of these specimens originate from the two main fluid sources and at depths consistent with the geochemical and geophysical interpretation two main clast lithotypes erupt at lusi the first lithotype is a light grey shale returned to the surface from the upper kalibeng formation the primary mud source and equilibrated at temperatures below 200 c the second lithotype is a black shale whose source is the ngimbang formation at 3800 m depth two distinct temperature clusters are recorded in these black shales one at 179 17 c consistent with the temperature estimate at 3800 m depth with the pre eruption geothermal gradient while younger minerals in the same specimen recorded substantial anomalous heating at 250 c these high temperatures indicate interaction with a heat source associated with the eruption through mixing with hydrothermal fluids this temperature jump suggests rapid heating at 4000 m depth consistent with a scenario of a magmatic intrusion and hydrothermal fluids circulation this rapid and significant temperature increase would initiate devolatilisation reactions of hydrous minerals within the deep sedimentary package and generate substantial highly overpressured fluids at depths significantly below the main source of erupted mud we infer that reactive and thermal pressurisation led to a deep and metastable system susceptible to e g seismic activity ultimately opening fluid pathways towards the surface along the watukosek fault system the two temperatures clusters recorded in the clasts show that conductive heat flow was the dominant heat transport prior to the eruption while the system is now driven by large scale convection and advective heat transport the lusi eruption occurred in a highly populated area forcing the evacuation of several tens of thousands of people this system appears unstoppable and poses a real and present hazard for the settlements still surrounding the eruption site continuous research is necessary to understand this spectacular phenomenon both for its important scientific relevance and the societal impact of this natural disaster

microstructure of graptolite periderm in silurian gas shales of northern poland abstract core samples of silurian graptolite shales from an exploration borehole within the baltic basin were examined by optical microscopy raman spectroscopy and high resolution transmission electron microscopy graptolite periderm is composed of poorly ordered carbonaceous material of mainly aromatic structures the dimension of the coherent domains is 1 2 nm they are composed of two to three stacked layers raman spectral parameters of graptolite periderm are correlated with the mean random rr and mean maximum rmax reflectance of graptolites the spectral id1 ig ratio predicts thermal maturity in a mean reflectance of graptolites rr range between 1 30 and 1 80 rmax 1 40 2 00 vitrinite reflectance equivalent vre 1 10 1 50 it is possible to calculate vreraman from the id1 ig ratio

evidence for molecular structural variations in the cytoarchitectures of a jurassic plant in this study we investigate the molecular structural characteristics of organic remains in various cellular organelles from a 180 ma jurassic royal fern belonging to the osmundaceae family of ferns and compare their carbon isotopic compositions to a now living species of royal fern osmunda regalis we discovered molecular structural variations indicated by raman and infrared spectral parameters obtained from various fossilized cellular organelles the organic remains preserved in the chromosomes and cell nuclei show marked structural heterogeneities compared to the cell walls during different stages of the cell cycle the fossil and extant fern have similar 13 c values obtained from bulk samples supporting evolutionary stasis in this plant lineage and an unchanged metabolic pathway of carbon assimilation since the jurassic the organic remains in the cellular organelles of the fossil seem to be less heterogeneous than those in the extant fern likely due to the preferential preservation of certain cellular compounds during fossilization taphonomic processes appear to have diminished the subcellular isotopic heterogeneities our research sheds light on the functioning of ancient plant cellular organelles during mitosis provides insights to the taphonomic processes operating at molecular and isotopic levels and shows the practicability of in situ techniques in studying the evolution and behaviors of ancient cells

shale tectonic processes field evidence from the parras basin north eastern mexico abstract major decollements located within buried overpressured shale commonly develop in thrust fronts accretionary prisms and sedimentary deltas controlled by gravity tectonics in seismic data it is possible to observe only large scale deformation of what is commonly designed as mobile shale but the precise geometry and the dynamic evolution of these bodies remains poorly understood it is often difficult to define if we are dealing with ductile or brittle deformation and to understand the role of the fluids in time and space during deformation for this reason large scale outcrops were studied in the parras basin mexico which makes possible a direct observation of the shale tectonic processes this work suggests changes in space and time of the deformation processes which occurred within the shale formation hosting the decollement distributed deformation was observed within the shale formation hosting the decollement compared to more localized deformation above also a change of the rheology of the shale over time occurred progressively toward brittle processes in the whole sedimentary pile xrd and microscopic studies have shown that diagenetic processes are favored in the shear zones of penetrative deformation leading notably to reverse gradient of illitization the isotopic analysis of cements in veins and the study of associated fluid inclusions have shown that fluid dynamics also evolved during time showing notably evidence for widespread fluid migration issued from rocks located below the decollement during the beginning of the deformation progressively the tectonic system located above the decollement tends to be preserved from fluid migration coming from below the decollement and to be influenced only by local fluid migration closed system