saharan wind regimes traced by the sr nd isotopic composition of subtropical atlantic sediments last glacial maximum vs today new nd sr isotopic data on the 30 m lithic particles of surface and last glacial maximum sediments recovered along the african margin between the equator and the gibraltar strait are presented in combination with grain size measurements this 30 m size fraction allows us to eliminate any hemipelagic contribution that could occur in the coarser fractions in the eolian fraction both sr and nd isotopic tracers reveal the same major northwestern origin mauritania mali southern algeria and morocco the archaean formations of the western saharan shield could be the source of the very unradiogenic ratios observed here the more southern regions senegal guinea act only as secondary sources a similar pattern is observed for the lgm lithic particles are mostly transported by both trade and saharan air layer sal winds along an approximate ne sw axis this main feature matches the southern plume characterizing the dust transport observed during winter no significant latitudinal shift of the belt winds is observed between the lgm and today at the lgm however dust fluxes were 2 4 times higher than today leading to a more archaean type imprint in the deposits we do not observe any clear relationship between the latitudinal variability of the upwelling systems identified in this region at the lgm and the location of the major wind systems both enhanced aridity on the continent and increased wind speed probably occurred together over western tropical africa during the last glacial period

sources of non glacial loess size quartz silt and the origins of desert loess abstract descriptions of peridesertic loess deposits and possible non glacial origins for silt size quartz are reviewed including direct release from weathered bedrock results from salt and frost weathering experiments are presented and methods by which sufficient energy can be imparted to sand size grains to release silt size fragments are identified these fragments may then be entrained by aeolian or fluvial action results from fluvial comminution experiments indicate that high energy mixed sediment fluvial systems may be very effective in generating quartz silt purely aeolian attrition is also seen as a major source of silt size and finer material results from aeolian abrasion experiments performed using crushed quartz sand are complemented by trials using sands from deeply weathered granite and pannonian sands from hungary field and laboratory observations are therefore seen to argue for the existence of deposits that can be classified as desert loess

chemistry and microstructures of clay particles in smectite rich shelf sediments south shetland islands antarctica the clay mineralogy of a holocene sediment core from the shelf of livingston island south shetland islands antarctica has been investigated by x ray diffraction xrd lattice imaging bulk chemical analysis of fine clay fractions and analytical transmission electron microscopy atem the clay minerals identified by xrd of 2 m fraction are smectite 63 chlorite 25 and illite 12 with little downcore variation lattice imaging of clay particles has confirmed the presence of interstratified illite smectite and interstratified chlorite smectite atem of ca saturated samples showed that the smectitic clay particles are rich in k fe and mg k in the smectitic particles is mostly present as a fixed cation in the interlayer confirming the presence of interstratified illite a comparison of the mineralogy of the bedrock soils in the probable source area and the core sediment strongly supports the view that the clay minerals must have originated by glacial erosion physical weathering and reworking of hydrothermally altered volcanic bedrock and tephra of the south shetland islands

geochemistry of the pliocene red clay formation in the chinese loess plateau and implications for its origin source provenance and paleoclimate change abstract recent field observations and sedimentological studies suggest the eolian origin of the late tertiary red clay formation underlying the pleistocene loess soil sequence in the loess plateau thereby extending the wind blown record from 2 6 ma down to 7 0 ma in north central china to address the source provenance of the red clay major and trace element concentrations were analyzed on the samples from a north south loess transect of the loess plateau and a red clay section at jiaxian results show that there is a good agreement of both major and trace element compositions between the last glacial interglacial loess soil units and the jiaxian red clay record the ree distribution patterns of the loess soil and red clay samples are remarkably similar in shape with enriched lree and fairly flat hree profiles and clear negative eu anomaly the geochemical features of the red clay are also identical to those of upper continental crust these chemical characteristics provide further evidence for eolian sedimentation of the red clay from the relations both between na2o al2o3 and k2o al2o3 ratios and between u pb and th pb ratios the eolian loess and red clay materials must have been subject to thorough sedimentary differentiation and moderate chemical weathering in the source area the chemical similarity between soil unit s1 and the red clay implies that such an environment as occurred in the last interglacial period may have already formed in northwestern china during the late tertiary comparison of down section variations in elemental ratios with field observations of pedogenic development of the red clay suggests that cao al2o3 sr rb and sr ba are more sensitive to climate changes than magnetic susceptibility and can be used to reconstruct the climate history of the late cenozoic

is quartz cathodoluminescence color a reliable provenance tool a quantitative examination abstract we examined cathodoluminescence cl colors of quartz by using red 590 780 nm green 515 590 nm and blue 380 515 nm optical filters interfaced with a cathodoluminescence cl detector attached to a scanning electron microscope sem sem cl images taken through these filters were captured digitally and transferred to a computer luminescence intensities luminosities of the images were measured by using available commercial software measured luminosities of these cl images are directly related to relative intensities of red green and blue cl emissions luminosity data were then used to construct plots that display relative luminosities of the cl images acquired through the red green and blue filters an unfiltered cl image of each quartz grain generated by photons with wavelengths ranging from 200 700 nm was also acquired by subtracting the numerical luminosity values of the images acquired through the red green and blue filters from the luminosity value of the unfiltered image the contribution to total luminosity provided by cl emission in the near ultraviolet uv was calculated the cl colors of quartz from a variety of volcanic plutonic and metamorphic rocks and hydrothermal deposits were examined volcanic quartz phenocrysts have the most restricted cl color range with strongest emission intensity in the blue wavelength band cl colors of plutonic quartz overlap those of volcanic phenocrysts but extend over a broader range to include quartz that displays higher intensity of red emission cl emission in hydrothermal vein quartz is similar to that in plutonic quartz although some hydrothermal quartz exhibits stronger green cl emission than does plutonic quartz the cl colors of metamorphic quartz exhibit the widest variation overlapping the color fields of both volcanic and plutonic quartz and extending further into the red cl emission in the near uv makes a significant contribution 5 85 percent to the total luminosity of sem cl images particularly images of plutonic quartz because of overlap in the cl color ranges of volcanic plutonic metamorphic and hydrothermal quartz unambiguous identification of quartz provenance on the basis of cl color alone is problematic it is difficult to distinguish between volcanic and some plutonic quartz and between some plutonic and hydrothermal quartz or to distinguish magmatic quartz from metamorphic quartz that exhibits blue cl color only metamorphic quartz that exhibits moderately strong red emission appears distinguishable on the basis of color from quartz of other origins our work thus suggests that cl color is not a reliable indicator of quartz provenance

iron rich nanoparticles formed by aeolian abrasion of desert dune sand 1 iron rich nanoparticles in aeolian mineral dust are of considerable importance to biogeochemical cycles a major determinant of the chemical characteristics of nanoparticles is the parent sediment they are sourced from the abrasion of dune sand has previously been shown to produce coarse dust 1 m during the occurrence of aeolian saltation in this study australian red dune sands were laboratory abraded and emission of particles 18 414 nm was observed throughout the experiment duration 1 h the mean size of particles was 130 nm at the start of the test but this gradually decreased to 110 nm at the end the number concentration of particles approximately trebled over the course of the experiment with results suggesting that collisions between mobile sand grains led to the production of new nanosized particles over time chemical analysis revealed that these nanoparticles were highly abundant in iron with some aluminium present this chemical composition suggests that nanoparticles are produced from the clay coatings surrounding the parent sand grains the study shows that abrasion from saltation occurring in australian dune sands can release iron rich nanoparticles making them available for downwind transport during blowing dust events

on the use of seismic data to monitor the injection of co2 into a layered aquifer abstract one method to monitor the migration of co2 through a confined layered aquifer is to use time lapse seismic reflection data we examine how such information may be combined with a flow model for a co2 plume spreading through a water saturated aquifer to provide constraints on the migration of a plume of injected co2 we focus on the estimation of the partitioning of the injected flux between the different layers in a multi layer geological formation and on estimation of the permeability of each layer since there is a minimum depth of the injected co2 which is detectable seismically we show that even in a one layer formation the model predicts two different possible permeabilities for the formation corresponding to a fast pressure driven flow and a slower buoyancy controlled flow these two estimates of the permeability are sensitive to changes in the seismic detection threshold if there is additional data on the bottom hole well pressure we can distinguish between the solutions in a multi layer system supplied from a single well the non uniqueness in the inversion process leads to uncertainty in both the partitioning of the flux between the layers and the permeability of the different layers in the formation the model constraints lead to a relatively small range of possible distributions of the flux but if there is a lack of information about the relative pressure in the different layers near the well there is a much larger range of possible values for the permeability of each layer we develop some simple bounds on the problem by considering the case in which the near well pressure difference between the layers is related to either the vertical hydrostatic or the vertical co2 static pressure difference we examine the implications of the technique for interpreting the historic data set relating to co2 injection at the sleipner field north sea in which there are nine distinct layers in the formation this leads to estimates for the possible flux partitioning between the layers and also some constraints on the possible range of effective permeability in each layer estimates of the partitioning of the flux can inform estimates of the efficiency of co2 injection in the different layers however the uncertainty in the estimate of the effective permeability leads to uncertainty in estimates of the propagation speed of the flow in each layer and hence assessments of the hazards of leakage and of the rate of capillary trapping or dissolution of co2 following injection

multiple steady states in exchange flows across faults and the dissolution of co2 this is the author accepted manuscript the final version is available from cup via http journals cambridge org download php file 2fflm 2fflm769 2fs0022112015001007a pdf code 58f6f56d3a1302266ca4bcf617ba24df

scavenging of pollutant acid substances by asian mineral dust particles 1 uptakes of sulfate and nitrate onto asian dust particles during transport from the asian continent to the pacific ocean were analyzed by using a single particle time of flight mass spectrometer observation was conducted at tsukuba in japan in the springtime of 2004 sulfate rich dust particles made their largest contribution during the dust event in the middle of april 2004 as a result of detailed analysis including backward trajectory calculations it was confirmed that sulfate components originating from coal combustion in the continent were internally mixed with dust particles even in the downstream of the outflow far from the continental coastline significant contribution of asian dust to sulfate was observed asian dust plays critical roles as the carrier of sulfate over the pacific ocean

loess stratigraphy in central china abstract loess sequences in central china provide a detailed record of climate changes during the last 2 5 million years at least 44 major shifts from glacial to interglacial conditions occurred during this time in china prolonged loess deposition lasting more than 40 millennia occurred eleven times with only four of these intervals in brunhes chron the climate oscillations took place with increased frequency between 2 4 and 0 5 ma compared to the last half million years major shifts toward cooler and drier climates occurred at about 2 4 ma 1 2 ma and 0 5 ma while less pronounced shifts are dated to 1 65 ma 0 8 ma and 0 2 ma three of the last four reversals of the earth s magnetic field whose lithostratigraphic position has been detail are recorded in a glacial deposit the low field magnetic susceptibility of loess and soils which reflects the concentration of ultrafine magnetite is related to the degree of pedogenesis and serves as a proxy measure of climate the accumulation rate of the magnetite was fairly constant throughout the last 1 2 million years and can serve as a measure of time susceptibility records from localities near xifeng and luochuan located 160 km apart are compared and used to define informal lithostratigraphic units in the loess plateau of china

gravity currents with residual trapping motivated by geological carbon dioxide co 2 storage we present a vertical equilibrium sharp interface model for the migration of immiscible gravity currents with constant residual trapping in a two dimensional confined aquifer the residual acts as a loss term that reduces the current volume continuously in the limit of a horizontal aquifer the interface shape is self similar at early and at late times the spreading of the current and the decay of its volume are governed by power laws at early times the exponent of the scaling law is independent of the residual but at late times it decreases with increasing loss owing to the self similar nature of the current the volume does not become zero and the current continues to spread in the hyperbolic limit the leading edge of the current is given by a rarefaction and the trailing edge by a shock in the presence of residual trapping the current volume is reduced to zero in finite time expressions for the up dip migration distance and the final migration time are obtained comparison with numerical results shows that the hyperbolic limit is a good approximation for currents with large mobility ratios even far from the hyperbolic limit in gently sloping aquifers the current evolution is divided into an initial near parabolic stage with power law decrease of volume and a later near hyperbolic stage characterized by a rapid decay of the plume volume our results suggest that the efficient residual trapping in dipping aquifers may allow co 2 storage in aquifers lacking structural closure if co 2 is injected far enough from the outcrop of the aquifer

bimodal character of the late paleozoic glaciations in argentina and bipolarity of climatic changes abstract the upper paleozoic sedimentary rock sequences of argentina show an outstanding record of climatic fluctuations during this interval and the complexity and rapidity of the climatic changes there were two distinct events of cooling or glacial periods the older in the middle carboniferous late visean bashkirian and the younger in the early permian asselian tastubian and these were separated by a long lasting interval of warming during the late pennsylvanian it is postulated that climatic fluctuations in the northern paleotemperate realm may have had the same causes as in argentina and that these periods of cooling and warming probably occurred at the same time in both hemispheres in western argentina and central patagonia the occurrence of the early permian glacial phase and the absence of the younger phases like those present in eastern argentina and south africa suggest that during the final deglaciation in gondwana thawing gradually progressed to the east then located closer to the paleopolar region

source regions and formation of the loess sediments on the high mountain regions of northwestern china loess on the high mountains of northwestern china is largely controlled by the topographic features distributed mainly on the northern slopes of the tianshan and kunlun mountains as well as in the ili valley between the northern and central tianshan ranges loess distributed in different regions has different ages with the oldest early pleistocene loess occurring in the ili valley geochemical mineralogical and granulometric analyses demonstrate that the loess in the three different regions has different provenance the loess on the northern tianshan and kunlun mountains is mainly derived from the junggar and taklimakan deserts respectively whereas the loess in the ili valley is derived mainly from the sary ishikotrau desert located in the republic of kazakhstan however these deserts serve mostly as holding areas for the silts rather than original source regions the production of the silt sized particles is mainly associated with glacial abrasion and tectonic induced rock denudation thus the loess in the studied regions can be described as mountainous loess rather than simply glacial loess or desert loess it is unlikely that the mechanisms of loess formation are the same in different regions given their dependence on specific geomorphological conditions and associated processes

making the material the formation of silt sized primary mineral particles for loess deposits abstract in 1911 e e free wrote it may be well to point out that there are really two problems of the loess a problem of the origin of material and a problem of deposition the problem of the origin of material has been relatively neglected in comparison to problems of deposition of the formation of deposits and latterly in comparison to studies of loess stratigraphy if we are to understand the true nature of loess this fascinating material we need to be aware of all the significant events in the processing of the particles which form a deposit a large amount of silt sized primary mineral material has to be produced to make a loess deposit loess is a quaternary phenomenon and we see the entire process being completed in quaternary times some powerful quaternary forces are able to produce very large amounts of granular material glacial grinding vigorously supported by smalley 1966a provides an obvious source for some loess material but the vast deposits of north china and central asia have no obvious glacial connection however they are adjacent to high asia a region of vast tectonic activity and an enormous release of terrestrial energy in the last several million years high asia is a large producer of loess silt much of which finds its way south to make the ganges delta but large amounts are moved north and east to make huge loess deposits africa presents a problem recent work e g coude gaussen 1987 suggests that there is a region of peri saharan loess but earlier observations e g penck indicate quite clearly that the sahara region is free of loess rathjens 1928 in his study of tripolitania indicated the presence of loess like deposits and described their nature but he did point out that 90 of the granular material was greater than 100 pm in diameter which would remove it from a strict loess definition on the soil taxonomy map of africa there is a belt of soil d3 which could include considerable loess deposits it stretches from the matmata loess in tunisia across northern libya to the western part of the egyptian coastal region if d3 contains loess this points to a genuine desert loess particle producing mechanism operating in the sahara

geochemical mineralogical and sedimentological studies on the taklimakan desert sands major element composition mineral composition and grain size distribution have been studied for quaternary aeolian sediments from the taklimakan desert north western china together with the variation of chemical and mineralogical compositions of different grain size fractions aeolian sediments from the taklimakan desert have higher ratios of feldspar quartz and calcite quartz finer grain size poorer roundness of quartz and feldspar grains and lower abundances of frosted quartz than found in aeolian sediments from other deserts such as the saudi arabian desert in spite of these immature mineralogical and sedimentological features the aeolian sediments from the taklimakan desert show low regional variations in major element and mineral compositions and are homogenized these observations confirm that two processes glacial activity within surrounding mountains and aeolian activity at the tarim basin are important in the homogenization of the taklimakan desert sands taklimakan desert sediments are constantly and effectively supplied from basement rocks in the surrounding mountains by glacial erosion the supplied sediments are further homogenized by aeolian activity in the desert and are partly blown away serving as the source of chinese aeolian loess compositional differences are observed between loess mainly 10 40 m particles and the 45 m fraction of the taklimakan desert sediments as well as between loess and whole rock of the taklimakan desert sediments these observations provide constraints for precise modelling of loess formation and for assessment of the chemical composition of the upper continental crust based on the chemical composition of aeolian loess

buoyant dispersal of co2 during geological storage carbon capture and storage is currently the only technology that may allow significant reductions in co2 emissions from large point sources seismic images of geological co2 storage show the rise of co2 is influenced by horizontal shales the buoyant co2 spreads beneath impermeable barriers until a gap allows its upward migration the large number and small scale of these barriers makes the prediction of the co2 migration path and hence the magnitude of co2 trapping very challenging we show that steady buoyancy dominated flows in complex geometries can be modeled as a cascade of flux partitioning events this approach allows the analysis of two dimensional plume dispersal from a horizontal injection well we show that the plume spreads laterally with height y above the source according to y h 1 2 l where l is the width of the shales and h is their vertical separation the fluid volume below successive shale layers and therefore the magnitude of trapped co2 increase as y h 5 4 above the source so that every additional layer of barriers traps more co2 than the one below upscaling small scale flow barriers by reducing the vertical permeability common in numerical simulations of co2 storage does not capture the dispersion and trapping of the co2 plume by the flow barriers

provenance of loess material and formation of loess deposits on the chinese loess plateau abstract results of a multiple isotopic chemical and mineralogical analysis of loess from the three northwestern inland basins the junggar basin the tarim basin and the qaidam basin and the loess plateau region of china are summarized they suggest a qualification of the conventional views that the three northwestern basins were the important source areas of the loess plateau and that the sand deserts were the primary single source of the chinese loess it is argued that the gobi stony desert in southern mongolia and the adjoining gobi and sand deserts the badain jaran desert tengger desert ulan buh desert hobq desert and mu us desert in china rather than the three inland basins are the dominant source areas of the loess plateau however although these gobi and sand deserts are regarded as the main source regions they serve as dust and silt holding areas rather than dominant producers the mountain processes including glacial grinding frost weathering salt weathering tectonic processes and some fluvial comminution in the gobi altay mts hangayn mts and the qilian mts have played an important role in producing the vast amounts of loess sized material for forming the loess plateau

evaluating the influence of meteorite impact events on global potassium feldspar availability to the atmosphere since 600 ma potassium feldspar present in global mineral aerosol 30 by combining crater size and tectonic reconstructions we are able to provide a quantitative and self consistent assessment of changes to global potassium feldspar availability considerable differences in potassium feldspar availability following meteorite impact events are revealed different impact events generated dust containing different amounts of potassium feldspar differing levels of influence upon climate are hypothesized and should now be tested by looking at stratigraphic records of these events to reveal the sensitivity of climate to different dust mineralogy supplementary material figures showing palaeolatitude determinations using various methods and reconstruction models and estimates of alkali feldspar abundance and distribution across contemporary continental landmasses for meteorite impact events are available at https doi org 10 6084 m9 figshare c 4253312

cathodoluminescence characterization of quartz particles in mature arenites a combination of cathodoluminescence cl microscopy with digital image analysis and spectroscopic analysis allows the detailed investigation of the commonly occurring colour shift from initial to final cl colours in detrital quartz with increasing irradiation a method for the quantification of the colour shift is presented and applied to different quartz sands unlithified sands of the lower cretaceous kuhfeld formation from ottenstein w germany and holocene sands from the barrier island of wangerooge n germany the colour shift depends on the defect structure of the quartz grains the defect structure is determined by the physico chemical conditions during crystallization and therefore can help trace the source of quartz grains a total of 25 different types of quartz grains in the ottenstein sands indicates a highly variable southern provenance many of the grains have recycled quartz cement overgrowths indicating an at least second cycle origin in contrast only 16 different quartz types have been observed in the wangerooge sands reflecting a less varied plutonic to metamorphic scandinavian provenance the study demonstrates the potential of quantified cl initial colour and colour shift in assessing the provenance of quartz rich sands and sandstones

loess is not just the accumulation of dust most regrettably there is much misuse of terminology in connection with the concept of loess and the interpretation of its origin people often speak and write incorrectly about loess accumulation even loess specialists who are aware of the fact that loess as a concept has to satisfy at least 10 criteria loess is not simply dust carried and deposited by wind dust only becomes loess after the passage of a certain amount of time in a given geographical zone i e only through diagenesis in certain ecological environments to state that loess is of aeolian origin is an oversimplification and an incorrect definition because an aeolian origin applies only to the dust from which the loess has been formed we are aware of the fact that airborne dust cannot be transformed into loess in every geographical environment but only under those conditions typical of semi arid grassland or steppe or forested steppe the process primarily occurs where the rate of dust accumulation exceeds sheet wash or weathering soil formation rates if the rate of dust accumulation is less than that of surface erosion or of soil biogenetic processes the dust then develops into soil or through intensive weathering and increased precipitation into loam or clay only part of the aeolian dust transported and deposited in a zone suitable for loess formation remains there permanently and is transformed in situ into loess dust not affected by diagenesis is usually further transported by snowmelt or rainwash and is only transformed into loess after it has been redeposited the loess itself however is easily erodible and its minerals are readily reworked and reaccumulated and given the appropriate conditions it readily undergoes diagenesis again we do not always have sufficient evidence to determine whether a given loess body is of primary or secondary origin traditionally the minerals making up primary loess have been regarded as originating in dust accumulated by aeolian processes secondary loess by contrast is different from typical loess in many ways and it is not unusual to find various loess series in which superimposed dust fractions have been transformed into loess by different processes recently we have observed that the origin of various types of loess is governed by differences in litho ecological conditions rather than by the way in which the mineral material from which the loess is derived dust has been primarily accumulated loessification is therefore determined by environmental conditions

controls on the dissolution of co2 plumes in structural traps in deep saline aquifers 1 sequestration of carbon dioxide in deep saline aquifers has been proposed and investigated as a viable solution to help mitigate carbon emissions from fossil fuels much research has been directed at understanding the transitions of supercritical co2 from being a mobile fluid phase to being trapped by capillarity or dissolved in groundwater such transitions lead to a reduction in mobility of co2 and hence in the risk of leakage to the surface following injection buoyant plumes of co2 migrate updip towards structural traps in the geological strata however some of this co2 may be capillary trapped in pore spaces or dissolved in groundwater en route since co2 saturated groundwater only has a small co2 concentration the dissolution of any large structurally trapped plumes of co2 may be controlled by the availability of unsaturated groundwater in an aquifer of finite vertical extent this may be rate limited by a combination of i the background hydrological flow coupled with ii the slow lateral exchange of relatively dense co2saturated groundwater with unsaturated groundwater in an inclined aquifer this may be controlled by the slow along aquifer component of gravity structurally trapped plumes of co2 may therefore persist for many thousands of years and since they are potentially highly mobile may represent an important contribution to the long term risks associated with co2 sequestration at particular sites

first carboniferous and permian marine macrofaunas from antarctica and their tectonic implications the first carboniferous and permian marine macrofaunas from the antarctic continent are described from three sites near mount king alexander island antarctic peninsula they include bivalves brachiopods bryozoans crinoids gastropods a possible monoplacophoran nautiloids and a possible serpulid or microconchid overall the faunas of two localities are carboniferous in age and compare well with the levipustula levis zone of argentina and eastern australia and are of namurian serpukhovian bashkirian age based mainly on the brachiopod and bryozoan faunas less positive brachiopod evidence from a third locality indicates the presence of a linoproductid fauna of possible carboniferous or permian gzhelian artinskian age having affinities with the argentinian cancrinella fauna the lithological and structural characteristics of the mount king beds are comparable to the accretionary complex of the lemay group hitherto of only proven jurassic cretaceous age of alexander island in which they are provisionally placed however the beds may also correlate with the trinity peninsula group carboniferous triassic of the northern antarctic peninsula the features of the mount king beds are consistent with the presence of an accretionery complex related to an island arc in the late palaeozoic but are not necessarily conclusive proof of the presence of such a terrane at that time in what is now alexander island

modelling carbon dioxide accumulation at sleipner implications for underground carbon storage an analytical solution to the equations describing the flow of a buoyant fluid released into a porous medium below a horizontal impermeable boundary is used to model the growth of co2 accumulations beneath thin mudstone beds in the utsira sand reservoir at sleipner in the north sea here supercritical co2 has been injected at a rate of 1 mt yr since 1996 and imaged by time lapse seismic data in 1999 2001 and 2002 the co2 rises as a narrow plume and is partially trapped by a number of thin mudstones before reaching the caprock to the reservoir the radii of the individual layers of trapped co2 increase as the square root of time since initiation as predicted by the modelling for constant input flux however apparent negative initiation times for horizons low in the reservoir suggests that net input fluxes for these layers have decreased with time most probably as the spreading layers have increased their leakage rates accumulation of co2 in the layers higher in the reservoir was initiated up to 3 yr after injection started modelling of the thickness profiles across three of the higher layers suggests that their net input fluxes have increased with time the observation that the central thicknesses of the deeper layers have remained approximately constant or have slightly decreased since first imaged in 1999 is consistent with the model predictions that the central thickness is directly proportional to net input flux however estimates of the permeability of the reservoir from the rate of increase of the radii of the co2 accumulations are an order of magnitude less than measured permeabilities on the reservoir sandstone permeabilities estimated from the modelling of layer thickness changes scatter in the same range these discrepancies may arise from 1 approximations in the model not being valid 2 the measured permeabilities not being representative of the permeability for two phase flow on the scale of the reservoir or considered less likely 3 that much less co2 is being stored in the imaged co2 accumulations than estimated from the seismic reflection profiles the most probable cause of the discrepancy is that the relative permeability for the co2 phase is significantly reduced at lower co2 saturations

provenance of the north pacific sediments and process of source material transport as derived from rb sr isotopic systematics abstract rb sr isotopic systematics of 111 samples of sediments in nine cores from the north pacific of quaternary and pliocene ages have been investigated they provide information on the provenance the process of particle transport and temporal variation in the flux of source material the rb sr isotopic systematics of the core sediments show well correlated pseudo isochrons the pseudo isochrons reflect the mixing of two types of material i e the asian continental material with high 87 rb 86 sr ratios 4 5 6 5 and high 87 sr 86 sr ratios 0 723 0 727 and the volcanic material with low 87 rb 86 sr ratios and low 87 sr 86 sr ratios from island arc volcanics such as the izu ogasawara mariana and the japanese islands and oceanic islands such as the hawaiian islands 0 0 2 0 0 703 0 708 the clearness of the pseudo isochrons implies that the rb sr isotopic composition of the weathering products derived from the asian continental crust is extremely homogenized the fine fraction a few m with a high 87 rb 86 sr ratio 5 0 6 5 is widely transported into the north pacific by the middle latitude westerlies and contributes largely to pelagic sediments the coarser fraction with a lower 87 rb 86 sr ratio

the contemporary physical and chemical flux of aeolian dust a synthesis of direct measurements of dust deposition abstract the deposition of aeolian or windblown dust is widely recognized as an important physical and chemical flux to ecosystems dust deposition adds exogenous mineral and organic material to terrestrial surfaces and can be important for the biogeochemical cycling of nutrients there have been many studies that characterize the physical and chemical composition of dust however few studies have synthesized these observations in order to examine patterns geochemical fluxes we have compiled observations of dust deposition rates particle size distributions psd mineralogy and bulk elemental and organic chemistry the rates of dust deposition observed across the globe vary from almost 0 to greater than 450 g m 2 yr 1 sites receiving dust deposition can be partitioned into broad categories based on there distance from dust source regions when compared to global dust models our results suggest some models may underestimate dust deposition rates at the regional and local scales the distance from the source region that dust is deposited also influences the particle size distributions mineralogy and chemical composition of dust however more consistent dust sampling and geochemical analyses are needed to better constrain these spatial patterns on average the concentrations of most major elements si al fe mg ca k in aeolian dust tend to be similar 20 to the composition of the upper continental crust ucc but there is substantial variability from sample to sample in contrast some elements tend to be depleted na or enriched ti in dust likely as a result of soil weathering processes prior to dust emissions trace elements especially heavy metals are consistently enriched in dust relative to the ucc ecologically important nutrients such as n and p are also present in dust deposition the geochemical flux attributable to dust deposition can be substantial in ecosystems located proximal to dust source regions we calculate estimates of elemental flux rates based on the average chemical composition of aeolian dust and varying rates of deposition these estimated flux rates are useful as a rough gauge of the degree to which dust deposition may influence biogeochemical cycling in terrestrial ecosystems and should be utilized to better constrain deposition estimates of global dust models

optical constants for asian dust in midinfrared region asian dust aerosols are composed of quartz plagioclase k feldspar calcite and phyllosilicates the optical constants for mixtures of these minerals are important not only to understand the effects of asian dust on climate but also to retrieve the properties of asian dust in this work the optical constants for labradorite and orthoclase representative minerals of plagioclase and k feldspar respectively are determined for the spectral range of 500 2000 cm 1 using bidirectional reflectance data from the advanced spaceborne thermal emission and reflection radiometer assuming an internal mixture of component minerals the effective refractive indices for asian dust are calculated using bruggeman s rule the results are proposed as optical constants for asian dust and differ from those for other dust aerosols such as the refractive indices for saharan dust derived from aerosol samples collected at barbados the imaginary refractive index for asian dust is larger indicating more absorptive than the index for saharan dust in the range of 1000 1300 cm 1 using the optical constants derived in this study the brightness temperatures of satellite measurements are simulated for typical loading scenarios of asian dust aerosols the simulated brightness temperatures exhibit a notable decrease with wave number in the region of 800 1000 cm 1 the results also corroborate the spectral features of the atmospheric infrared sounder airs measurements for an asian dust storm airs brightness temperatures near 1223 cm 1 lower than the maximum near 830 cm 1 can also be simulated using the derived optical constants for asian dust

possible formation mechanisms for the modal coarse silt quartz particles in loess deposits abstract the first major event in the formation of a loess deposit is the production of silt sized quartz particles many particle production methods have been proposed the bulk of loess particles appear to be produced by a glacial grinding to give ice sheet loess or b cold weathering in high regions to give mountain loess there are close relationships between mountain loess and desert loess loess material can be seen as a product of the cold phase of the glacial cycle

a mineral tracer toward high resolution dust provenance on the chinese loess plateau sem tem and sulfur isotopes of sulfate inclusions in biotite the most important terrestrial archive of the quaternary climate is the chinese loess plateau clp distributed over a vast region peripheral to the deserts of inner asia numerous paleoclimatic studies have examined magnetic chemical and isotopic proxies from deep loess paleosol sections however the highly uniform mineralogy of the clp has made it difficult to track the provenance transportation and deposition of dust particles here we report that the micrometer scale mineralogical heterogeneity of the loess particles has a significant potential in determining high resolution loess provenance scanning and transmission electron microscopy of the chinese loess reveals that biotite particles commonly have microinclusions of ba sr sulfates displacing the micaceous layers along cleavages chemical compositions varied widely from barite to celestine within the same biotite grain the ba rich sulfates precipitated first followed by an overgrowth of sr rich sulfates the frequency of sulfate bearing biotite varied greatly over several loess sections implying a specific source and sedimentation process their abundance on the western clp and sulfur isotopic composition support their derivation from porous sedimentary sequences reacted with hypersaline solutions e g arkosic sandstone probably located west of the clp covering the qilian mountains qaidam basin and surrounding mountains of the tibetan qinghai plateau the sulfate bearing biotite is the first microscopic mineral tracer in the clp provoking further search for other microscopic heterogeneities of the chinese loess and their equivalents in the source regions

changes in mineralogy of loess paleosol sections across the chinese loess plateau quantitative mineralogical analysis of bulk samples and single particles was carried out on three loess sections of different local climate settings on the chinese loess plateau clp mineralogy geochemistry and single particle petrography of loess and paleosols are relatively uniform over the clp however in detail there are mineralogical changes related to eolian process and chemical weathering particle size sorting eastward from western sources led to an eastward increase of the total phyllosilicate contents enriched in fine illitic clay minerals after deposition detrital minerals susceptible to chemical weathering were sequentially altered in a progressive fashion with increasing precipitation in the order of calcite dolomite biotite illite chlorite amphibole and plagioclase the weathering of biotite chlorite and illite resulted in a significant increase of expandable phyllosilicate contents the sequential weathering of the minerals is reflected chemically in the decrease of na and mg and the increase of iron oxidation mineralogy of the chinese loess at individual sites reflects the effects of size fractionation during eolian transportation and progressive sequential weathering along the climatic gradient and it is essential to consider both effects when using mineralogical and dependent chemical data in the paleoclimatic reconstruction of the clp

asian dustfall in the st elias mountains yukon canada in april 2001 a major atmospheric dustfall event occurred in the st elias mountains yukon territory canada field samples were collected and analyzed for particle size mineralogy chemical composition and sr nd and pb isotopes dusts found above 3000 m had their source in the gobi desert region of northern china and inner mongolia and were transported to the yukon following a series of major dust storms that took place in early april dusts found below 3000 m had local yukon or mixed source s the asian dusts had a modal volume diameter of 4 m typical of far traveled mineral aerosols however larger 10 m particles were also found at 5000 m suggesting a very rapid trans pacific transport in the mid troposphere we estimate that the april 2001 event deposited from 5500 to 6335 tons of dust over an area of 21 000 km2 in the southwestern yukon most of which probably fell within a week our findings are consistent with instrumental observations and model simulations of the april 2001 event while the dust cloud was reportedly mixed with volatile pollutants from asia we found no evidence of metal pollution associated with the dustfall in the yukon our findings contribute to clarify the dynamics and the geochemical impact of asian dust long range transport events and to better estimate eolian fluxes of dustborne elements e g fe to the ocean associated with such events they may also assist in identifying past asian dust events in ice cores drilled from the st elias mountains icefields to develop a long term record of their frequency magnitude and source s

development of the late paleozoic glaciations of the south american gondwana in western argentina abstract the late paleozoic ice age in the south american segment of gondwana consisted of several glaciations which can be grouped into two main glacial periods the oldest of them occurred in late early to early late carboniferous time and the younger in early permian time paleontological evidence in the western argentine precordillera supports a late visean age for the beginning and a probable early westphalian age for the end of the carboniferous glacial period in this span of time subsidence and deposition of glacial debris took place in the western mobile belt and in patagonia but no sediments of that age were deposited in the eastern portion of the south american gondwana where subsidence started later a carboniferous glacial sequence is remarkably well preserved in the san eduardo group on the western flank of the precordillera where at least three distinct glaciations are recognized this sequence can be taken as a reference section for the carboniferous glacial deposits shorter than the former and probably restricted to the asselian epoch the permian glacial period is better known the evidence for it is well developed in eastern south american gondwana although a relic is also present in the precordillera the recognition of two glacial periods within the late paleozoic ice age is supported by the existence of a long lasting interglacial which seemingly began in the late westphalian and lasted until the end of the carboniferous period this major interglacial period is inferred from the total absence of glacial features in the upper carboniferous sequences in spite of the existence of a mountainous belt parallel to the pacific during the carboniferous period the presence of marine beds and glacial drift well to the east of these ranges suggests that it was not altitude that was the main factor in determining the formation of glaciers but latitude plus a global change in temperature it is argued that the ice sheets extended greatly during the carboniferous glaciations and reached neighboring areas of the paganzo basin in central argentina

contemporary geochemical composition and flux of aeolian dust to the san juan mountains colorado united states 1 dust deposition in the rocky mountains may be an important biogeochemical flux from upwind ecosystems seasonal winter spring dust mass fluxes to the san juan mountains during the period from 2004 to 2008 ranged from 5 to 10 g m 2 with individual deposition events reaching as high as 2 g m 2 dust deposited in the san juan mountains was primarily composed of silt and clay sized particles indicating a regional source area the concentrations of most major and minor elements in this dust were similar to or less than average upper continental crustal concentrations whereas trace element concentrations were often enriched in particular dust collected from the san juan mountain snowpack was characterized by enrichments of heavy metals including as cu cd mo pb and zn the mineral composition of dust partially explained dust geochemistry however based on results of a sequential leaching procedure it appeared that trace element enrichments were associated with the organic and not the mineral fraction of dust our observations show that the dust derived fluxes of several nutrients and trace metals are substantial and because many elements are deposited in a mobile form could be important controls of vegetation soil or surface water chemistry the flux measurements reported here are useful benchmarks for the characterization of ecosystem biogeochemical cycling in the rocky mountains

the nature origin and accumulation of loess abstract loess can be defined simply as a terrestrial clastic sediment composed predominantly of silt size particles which is formed essentially by the accumulation of wind blown dust there are three fundamental requirements for its formation 1 a sustained source of dust 2 adequate wind energy to transport the dust and 3 a suitable accumulation site most loess has been modified to some degree by local reworking bioturbation and syn depositional weathering but a process of loessification is not necessary for a dust deposit to qualify as loess the terms primary loess and secondary loess have previously been used to described wind deposited loess and redeposited loess respectively but it is more accurate to describe material reworked and redeposited by non aeolian processes as loess derived colluvium or loess derived alluvium during the quaternary loess formed in three main situations 1 mid continental shield areas beyond the limits of ice sheets periglacial loess 2 on the margins of high mountain ranges perimontane loess and 3 on the semi arid margins of some lowland deserts peridesert loess peridesert loess is relatively poorly developed partly due to the limited efficiency of silt generating mechanisms in low land deserts compared with glaciation but also important is the tendency in arid areas for dust to be dispersed over a wide area and to be rapidly reworked after deposition particularly in areas which experience frequent climatic changes the remarkably thick loess of china and central asia results from an unusual combination of conditions which has persisted for much of the last 2 3 million years namely rapid uplift of the tibetan plateau and surrounding mountain ranges high rates of sediment production and supply to adjacent basins a strong northwesterly and westerly wind regime and the existence of effective dust traps downwind of the source regions

isotope geochemistry of quaternary deposits from the arid lands in northern china abstract quaternary deposits of various types lacustrine desert sand river loess and loess like deposits from the southwestern tarim basin north tianshan northeast china and the central loess plateau exhibit an nd 0 range from 5 to 12 8 and a 147 sm 144 nd range from 0 110 to 0 140 their nd depleted mantle model ages are between 1 50 and 1 92 ga with a mean value of 1 7 ga th sc ratios vary over a wide range from 0 1 to 2 comparison of these geochemical signatures with those of the old australian shales and modern pacific ocean dust suggests a continuous input of mantle derived material into the crust over geological time the deposits from the north tianshan show clearly different chemical and isotopic features with significantly higher sm nd high 143 nd 144 nd low 87 sr 86 sr and low la lu and th sc ratios relative to those in the deposits from the other areas this indicates a geological control on the local source which has an overall young age and an enrichment of basic components the ce 0 values of two loess samples from the central loess plateau are 1 8 and 3 9 corresponding to depleted mantle model ages of 2 2 and 3 4 ga like the rb sr system the evolution of the la ce isotopic system in the crust may be to some extent decoupled from the sm nd system due to la ce fractionation by sedimentary processes the loess deposits and the desert sand are not distinguishable in isotopic composition but show somewhat different chemical compositions we conclude that the loess can have originated from desert processes since the difference in the chemistry of the desert sand and loess may result from mineral sorting during desert processes and aeolian transportation the loess deposits on the central loess plateau chemically and isotopically resemble the desert loess deposits in the southwestern tarim basin but do not resemble those of the north tianshan accordingly the loess on the plateau may have a source region in the tarim basin but clearly not in the north tianshan

the gondwanan carboniferous permian boundary revisited new data from australia and argentina abstract the identification and correlation of the carboniferous permian gzhelian asselian boundary within the sedimentary sequences of gondwana has always been a topic of debate type latest carboniferous and earliest permian marine sequences are characterised by warm tropical faunas and come from the uralian region of russia and kazakhstan faunas include conodonts and fusulinid foraminiferids which are prime tools for correlation such faunal groups are absent from most gondwanan sequences where reliance for correlations must be placed primarily on brachiopods bivalve molluscs and palynology the western australian marine sequences with their contained ammonoids provide a pivotal link for the dating and correlating of early permian gondwanan sequences with those of the type regions and their palynostratigraphical record is essential for trans australian correlations and correlations elsewhere throughout gondwanaland new data from the fully cored dm tangorin ddhl bore hole drilled in the cranky corner basin new south wales australia reveals a sequence of descending faunal zones the stratigraphically highest zone with eurydesrna cordaturn encompasses the late sakmarian sterlitamakian the middle zone with torniopsis elongata sulciplica c r a m and trigonotreta tangorini straddles the sterlitamakian tastubian boundary with the palynomorphs pseudoreticulatispora pseudoreticulata high in the zone and granulatisporites confluens low in the zone an impoverished fauna with trigonotreta nov low in the granulatisporites confluens zone is probably of latest asselian or tastubian age significant new data from argentina has revealed marine faunas from below the occurrence of granulatisporites confluens these are considered to be of asselian age outcrops of the tupe formation with a marine fauna at la herradura creek in the western paganzo basin san juan province are best regarded as being of mid to late asselian age the tupe fauna has been recognised as the tivertonia jachalensis streptorhynchus inaequiornatus zone previously this fauna was considered to be of late carboniferous or stephanian age three faunal associations are known from the rio del peii6n formation rio blanco basin la rioja province the middle assemblage with tivertonia costaturnulus kochiproductus and trigonotreta appears to correlate well with the tupe formation fauna the lower assemblage with streptorhynchus etherilosia costaturnulus trigonotreta and a punctate spiriferid as well as indeterminate productids probably of early asselian age the youngest assemblage includes a species ofrhynchopora that is close to rhynchopora australasica from the latest asselian early tastubian of western australia the marine biostratigraphical data from argentina has enabled a much greater understanding of the earliest permian marine faunas to be achieved a story that is apparently absent from the other cold and cool temperate regions of gondwana

late quaternary dust flow on the chinese loess plateau abstract the dust flux of over 25 g cm2 103yr was reached in the central part of the chinese loess plateau during the last glacial maximum this is more than three times higher than during the last interglacial and early glacial time the grain size of the pleniglacial dust reached a peak shortly after 20 000 years ago and testifies to the occurrence of strong winds and frequent dust storms

origin of desert loess from some experimental observations a longstanding problem of quaternary geology has been the origin of the silty deposit known as loess of the many explanations for its formation and distribution1 2 the most commonly accepted is that the silt is produced by subglacial grinding processes1 3 4 followed by redistribution and deposition by the wind the large expanses of loess in central europe are therefore considered to be the consequence of quaternary glaciation5 there is however a view6 7 that loessic silt may also originate as the product of processes in hot deserts some proponents of the desert loess hypothesis consider that silt size material is the product of weathering processes7 which may include salt weathering8 or weathering down incipient cracks9 an alternative mechanism is aeolian attrition of sand grains although probably as a result of the experimental work of kuenen10 smalley and krinsley11 consider that only fine silt 2 6 m is produced in large quantities by the abrasion of quartz grains we have simulated aeolian attrition of angular quartz grains previously produced by weathering in deserts the products of abrasion show that both coarse and fine silt sizes are produced these findings suggest that desert aeolian processes can produce loess we also suggest that much of this material from many deserts has been deposited in the sea but that the chinese loess could have been produced in the gobi desert the finest particles produced by such attrition may be a source of silica for silcrete formation

provenance of dust in the pacific ocean eolian dust preserved in deep sea sediment cores provides a valuable indicator of past atmospheric circulation and continental paleoclimate in order to identify the provenance of eolian dust nd and sr isotopic compositions and rb sr and rare earth element ree concentrations have been determined for the silicate fractions of deep sea sediments from the north and central pacific ocean different regions of the pacific ocean are characterized by distinct air borne inputs producing a large range in end 10 to 1 stsr 86sr 0 705 0 721 la yb 5 15 eun eu 0 6 1 0 and sr nd 4 33 the average nd isotopic composition of pacific deep sea sediments eno 6 is more radiogenic than the average from the atlantic ena 8 in contrast the average 1475m 14and ratio for pacific sediments 0 114 is identical to that of atlantic sediments and to that of global average riverine suspended material the values of ena and 147sm 144nd are positively correlated for the pacific samples but negatively correlated for atlantic samples reflecting a fundamental difference between the dominant components in the end members with radiogenic nd island arc components in the pacific and lree enriched intraplate ocean island components in the atlantic samples from the north central pacific have distinctive unradiogenic end values of 10 87sr 86sr 0 715 high la yb 12 and low eun eu 0 6 and sr nd 3 6 these data are virtually identical to the values for loess from asia and endorse the use of these sediments as indicators of asian paleoclimate and paleowind directions island arc contributions appear to dominate in the northwest pacific resulting in higher end 1 to 1 and lower 87sr 86sr 0 705 and la yb 5 sediments from the eastern pacific tend to have intermediate sr and nd isotopic compositions but regionally variable sr nd and ree patterns they appear to be derived from the west margin of the north and south american continents rather than from asia our results confirm that dust provenance can be constrained by isotopic and geochemical analyses which will facilitate reconstructions of past atmospheric circulation and continental paleoclimate

mineralogical and morphological properties of individual dust particles in ice cores from the tibetan plateau using a field emission scanning electron microscope and energy dispersive x ray spectrometer fesem eds individual insoluble dust particles in ice cores recovered from the northern dunde western murtagata and south eastern palong zangbo tibetan plateau were analysed in order to reveal the mineralogical and morphological characteristics of the analogue of long range transported asian dust the results reveal that the dust particles are mainly composed of quartz 17 36 number abundance clay 37 48 and feldspar 12 18 illite and chlorite are the dominant clay species while kaolinite is rarely observed for the three sites regional differences in the mineral assemblages are significant in particular the abundance of quartz chlorite and muscovite species reflecting the regional provenance of these dust particles and the climatic regime in their source areas oxide ratios in clays indicate different weathering strengths of the particles in their source regions with a higher k2o sio2 al2o3 in the western and northern tibetan plateau the individual particles have modes of 1 48 and 1 53 in the aspect ratio and circularity distribution respectively no significant relationship between aspect ratio and circularity was found quartz and feldspar particles have a narrow aspect ratio distribution muscovite particles have the coarsest grain size while chlorite particles have the finest

capillary entry pressure and the leakage of gravity currents through a sloping layered permeable rock we examine the motion of a buoyant fluid injected into a water saturated porous rock as it spreads along a thin inclined low permeability barrier we account for leakage of the fluid across the barrier once the current is sufficiently deep so that the pressure exceeds the capillary threshold we show that at some distance from the source the pressure decreases below this threshold and all the remaining flux spreads laterally along the barrier we examine the controls on the partitioning of the flow between the draining flux and the laterally spreading flux and also the controls on the lateral extent of the draining region for the case of an instantaneous release and a maintained release of fluid we consider the implications of our work for the dispersal of co 2 plumes which may be sequestered in deep saline aquifers

loess stratigraphy in central china abstract the loess deposits in central china record world wide climate changes of the last 2 5 ma numerous climatic oscillations are marked by alternating loess and soil units with continuous coverage of the matuyama and brunhes epochs magnetic susceptibility of the deposits correlates closely with the oxygen isotope record of the deep sea sediments and provides an independent measure of climate and time the key marker bed of the chinese loess sequence is the paleosol s5 the time equivalent of the mid brunhes oxygen isotope stages 13 14 and 15 it marks a prolonged interval of warm humid climate lasting from approximately 615 to 470 thousand years ago several episodes of river downcutting coincide with deposition of the exceptionally thick loess units l1 oceanic oxygen isotope stages 2 to 4 l2 stage 6 l5 stage 12 l6 stage 16 l9 stage 22 l15 stage 38 about 1 15 ma and ws4 about 2 3 ma these erosional events are interpreted as a result of episodic uplift of the loess plateau the deposition of the earliest loess layers between 2 5 and 2 3 ma ago marks a first order shift from warm and humid environments toward harsh continental steppes comparable to those of the middle and late pleistocene little if any lithologic or paleontologic changes were noted within or above the olduvai magnetozone so that the proposed plio pleistocene boundary at approximately 1 65 ma has no lithostratigraphic and biostratigraphic representation in the chinese loess series comparison with the deep sea drilling program core 552a in the north atlantic and with the santerno river section near bologna shows that the occurrence of the earliest loess in china coincides with the timing of the first significant ice rafting in the north atlantic and with the appearance of cold water foraminifers in the marine deposits of northern italy an extension of the stage system of the oxygen isotope signal extended back to the gauss matuyama boundary is proposed

deposition and weathering of asian dust in paleolithic sites korea abstract paleolithic stone artifacts in korea typically occur in brown clay silt bcs sequences the origin and depositional environment of these sequences are important for reconstructing the paleoenvironment as well as for establishing chronologies of artifact bearing stratigraphic units we investigated four bcs bearing sections in foothills and river and marine terraces in korea by applying quantitative mineralogical geochemical microtextural and k ar isotopic methods in all four sections the lower units are colluvial and fluvial deposits strongly influenced by diverse local lithology whereas the upper units are characterized by bcs units mineralogical geochemical compositions grain sizes and colors converge into common properties in the upper bcs units in all sections these common properties are consistent with the eastward trends of increasing weathering degree and grain size fining throughout the loess paleosol sections of the chinese loess plateau clp k ar detrital ages of the sections also converge upward into a narrow range similar to the age ranges of the loess and paleosols in the clp the top bcs unit in the jeongok section the thickest section is underlain by an additionally weathered bcs unit with strong red chroma indicating a change from warm to cold climate we did not observe any clear evidence of climatic changes in other thinner sections which may be due to a superposition of cold stage accumulation and warm stage deep weathering the common properties of the bcss in korean sections and their relationship to the clp loess and paleosols indicate widespread deposition of asian dust and subsequent weathering in the late quaternary forming bcs sequences in this respect the bcs sequences investigated here are considered to be the additionally weathered equivalents of the clp loess paleosol sequences having been exposed to the high annual precipitation of the korean peninsula given the wide distribution of bcs sequences at paleolithic sites throughout the peninsula the findings of this study are important for the ongoing debate surrounding the depositional environments of the paleolithic deposits and provide a foundation for the establishment of the chronological framework of the paleolithic artifact bearing layers and lithic assemblages

oxygen isotope signatures of quartz from major asian dust sources implications for changes in the provenance of chinese loess abstract we present a systematic investigation of the oxygen isotopic composition of quartz in both fine and coarse fractions 18 o values of both the fine and coarse fractions from the various sources are overlapped to varying degrees thus making it difficult to differentiate them nevertheless the quartz 18 o values of both fractions exhibit an increasing trend from the mongolian gobi to the northern chinese deserts and then to the taklimakan desert this implies that the geological settings of the source areas are different which in turn results in differing contributions of high temperature igneous rocks the combination of quartz 18 o results with other quartz based provenance tracers can clearly differentiate the three major source areas i e the taklimakan desert the mongolian gobi and the northern chinese deserts in addition comparison of our results with previous 18 o measurements of fine grained quartz from the luochuan loess sequence suggests the likely glacial interglacial fluctuations in dust provenance finally we suggest that the combination of quartz 18 o signatures and other dust provenance tracers can potentially improve the recognition of long term fluctuations in the provenance of chinese loess red clay deposits

87sr 86sr variation in north pacific sediments a record of the milankovitch cycle in the past 3 million years abstract temporal variations of sr isotopic compositions in the detrital component of north pacific sediments have been precisely examined the sr isotopic composition is controlled by the flux of eolian material from the asian continent with a high 87 sr 86 sr ratio 0 724 0 726 relative to volcanic material with a low ratio 0 703 0 705 from the izu ogasawara mariana arc and oceanic islands such as the hawaiian islands assuming that the volcanic flux is constant the temporal variation in sr isotopic ratio reflects the amount of eolian input from the continent the major characteristics of the temporal variations and the interpretation of them are summarized as follows 1 the 87 sr 86 sr records show cyclic fluctuations of 400 ky and 100 ky periodicities which are associated with the eccentricity of the earth s orbit milankovitch cycle 2 between 3 and 0 8 ma the 87 sr 86 sr ratio in the north central pacific sediment increases gradually this reflects an increased eolian input from the arid region in east asia the increase must be related to aridification of the asian continent 3 the decreased 87 sr 86 sr ratio during the past 0 8 m y implies a decreased eolian input the age of 0 8 ma may relate to the climatic event known as the middle pleistocene shift all of these phenomena reflect a fluctuation of the eolian flux corresponding to the paleoclimatic cycle of aridity in the asian continent the sr isotopic composition of pelagic sediment in the north pacific is sensitive to changes in the eolian input reflecting to the aridity of the asian continent

asian provenance of glacial dust stage 2 in the greenland ice sheet project 2 ice core summit greenland samples of dust from the greenland ice sheet project 2 gisp2 ice core summit greenland dated within marine isotope stage 2 between 23 340 and 26 180 calendar years b p around the time of the coldest local last glacial temperatures have been analyzed to determine their provenance to accomplish this we have compared them with approximately coeval aeolian sediments mostly loesses sampled in possible source areas psas from around the northern hemisphere the 5 m grain size fraction of these samples was analyzed on the basis that it corresponds to the atmospheric dust component of that time and locale which was sufficiently fine grained to be transported over long distances on the basis of comparison of the clay mineralogy and sr nd and pb isotope composition with ice dust and psas and assuming that we have sampled the most important psas we have determined that the probable source area of these gisp2 dusts was in eastern asia the dust was not derived from either the midcontinental united states or the sahara two more proximal areas that have been suggested as potential sources based on atmospheric circulation modeling except for a brief period during an interstadial when dust transport was exceptionally low for glacial times and had a mineralogical composition indicative of a slightly more southern provenance the source area of the dust did not change significantly during times of variably higher fluxes of dust with larger mean grain size or lower fluxes of dust with smaller mean grain size this includes the high dust period that correlates with the heinrich 2 period of major iceberg discharge into the north atlantic variable wind strengths must therefore be invoked to account for these abrupt and significant changes in dust flux and grain size

co2 dissolution in the presence of background flow of deep saline aquifers we study the effect of background flow on the dissolution and transport of carbon dioxide co2 during geological storage in saline aquifers and include the processes of diffusion advection and free convection we develop a semianalytical model that captures the evolution of the dissolution in the absence of free convection using the semianalytical solution we determine scaling relations for the steady rate of dissolution that follow either jst pe r or jst pe depending on the value of pe r where r represents the ratio of the extent of co2 plume to the aquifer thickness and pe is the peclet number using direct numerical simulations we provide detailed behavior of the convective mixing during the dissolution we establish the criteria for forced and mixed combined free and forced convection in aquifers that is governed by the background flow accordingly we provide the scaling relations jst pe r and jst ra r representing the forced and free convection asymptotes respectively where ra is a rayleigh number based on aquifer thickness the results reveal that the background velocity can delay the onset of free convection and can alter the subsequent mixing this phenomenon is more profound in the systems subject to strong background flows wherein horizontal component of the velocity field generated by background flow hinders the establishments of vertical component of the velocity field finally by applying the proposed relations to several potential storage sites we demonstrate the screening process in finding aquifers where the background flow exerts an important influence on the dissolution

exhumation history of the west kunlun mountains northwestern tibet evidence for a long lived rejuvenated orogen abstract how and when the northwestern tibetan plateau originated and developed upon pre existing crustal and topographic features is not well understood to address this question we present an integrated analysis of detrital zircon u pb and fission track double dating of cenozoic synorogenic sediments from the kekeya and sanju sections in the southwestern tarim basin these data help establishing a new chronostratigraphic framework for the sanju section and confirm a recent revision of the chronostratigraphy at kekeya detrital zircon fission track ages present prominent triassic early jurassic 250 170 ma and early cretaceous 130 100 ma static age peaks and paleocene early miocene 60 21 ma to eocene late miocene 39 7 ma moving age peaks representing source exhumation triassic early jurassic static peak ages document unroofing of the kunlun terrane probably related to the subduction of paleotethys oceanic lithosphere in combination with the occurrence of synorogenic sediments on both flanks of the kunlun terrane these data suggest that an ancient west kunlun range had emerged above sea level by triassic early jurassic times early cretaceous fission track peak ages are interpreted to document exhumation related to thrusting along the tam karaul fault kinematically correlated to the main pamir thrust further west widespread middle late mesozoic crustal shortening and thickening likely enhanced the early mesozoic topography paleocene early eocene fission track peak ages are presumably partially reset limited regional exhumation indicates that the early cenozoic topographic and crustal pattern of the west kunlun may be largely preserved from the middle late mesozoic the main pamir tam karaul thrust belt could be a first order tectonic feature bounding the northwestern margin of the middle late mesozoic to early cenozoic tibetan plateau toward the tarim basin late oligocene early miocene steady exhumation at a rate of 0 9 km myr is likely related to initial thrusting of the tiklik fault and reactivation of the tam karaul thrust thrusting together with upper crustal shortening in the mountain front indicates basinward expansion of the west kunlun orogen at this time this episode of exhumation and uplift associated with magmatism across western tibet is compatible with a double sided lithospheric wedge model primarily driven by breakoff of the indian crustal slab accelerated exhumation of the mountain front at a rate of 1 1 km myr since 15 ma supports active compressional deformation at the margins of the northwestern tibetan plateau we thus propose that the west kunlun mountains are a long lived topographic unit dating back to triassic early jurassic times and have experienced middle late mesozoic to early cenozoic rejuvenation and late oligocene miocene expansion

nd and sr isotopic characteristics of chinese deserts implications for the provenances of asian dust silicate nd sr isotopes of the fine grained fractions of the 10 major deserts and sandy lands in north china and the loess in chinese loess plateau were systematically investigated wide ranges in nd sr isotopic compositions have been observed the results of the 7 0 b the deserts on the northern margin of tibetan plateau with end 0 ranging from 11 9 to 7 4 and c the deserts on the ordos plateau with the lowest end 0 11 5 the distribution of the threes isotopic regions is controlled by the tectonic setting in north china which implies that the materials of the deserts are derived from the locally eroded rocks from the surrounding mountains and the nd sr isotopic signatures of these deserts could be quit stable over the past million years on the sub tectonic time scales if there is any desert at those times the nd sr isotopic compositions of the loess are mostly close to those of the deserts in isotopic region b suggesting that the main source regions of the last glacial loess in the chinese loess plateau are badain jaran desert tengger desert and qaidam desert also the comparison between the nd sr isotopes of the 5 lm silicate fractions of the deserts and the ancient dust falls in the north pacific and greenland show that the asian end members of these dust falls are derived most from the deserts in the isotopic region b and less from those in the isotopic region c

mechanisms of loess sized quartz silt production and their relative effectiveness laboratory simulations the production of loess sized quartz silt is frequently ascribed to glacial grinding mechanisms in this study a series of laboratory simulations was set up the purpose of which was to demonstrate that a range of geomorphic mechanisms are capable of producing silt under laboratory conditions the geomorphic mechanisms investigated were aeolian abrasion fluvial comminution glacial grinding salt weathering and frost weathering the results confirmed that under laboratory conditions all of these mechanisms were capable of producing silt the relative effectiveness of these mechanisms at producing silt under laboratory conditions was then calculated in order to provide a starting point for a consideration of their potential effectiveness within the natural environment these results indicate that fluvial and aeolian activity are highly effective at producing quartz silt over short time periods in a dust storm of four days duration 287 g of silt could potentially be produced from every kilogram of sand entrained while fluvial comminution in a turbulent fluvial environment could potentially produce 900 g of silt from every kilogram of sand entrained within 32 h over longer periods of time the glacial grinding and weathering mechanisms represent more continuous and hence more effective silt producing mechanisms although it is realised that the relative importance of each silt producing mechanism will differ spatially and temporally due to differences in climate relief geology and geomorphic history the findings from this work do have implications for the genesis of loess deposits they demonstrate that glacial and cold weathering processes are not solely responsible for fine particle formation and that efficient silt producing mechanisms can operate within a variety of environments under suitable conditions weathering together with episodic contributions from aeolian and fluvial mechanisms could be responsible for a considerable proportion of global quartz silt production

late pleistocene and holocene aeolian dust deposition in north china and the northwest pacific ocean abstract rates of dust deposition in the north pacific and the central loess plateau of china show a poor correlation during the last 30 000 yr although in both cases the dust was derived from deserts in northern china loess accumulation rates were high at the time of the last glacial maximum while dust flux to the north pacific was low at this time maximum dust flux to the north pacific is recorded in the mid holocene but holocene rates of loess accumulation have been low these differences are shown to reflect the different nature of the wind conditions responsible for dust transport to the loess plateau and the north pacific dust transport responsible for formation of the loess occurred mainly in the lower 1 5 km of the atmosphere and was accomplished by cold low level northwesterly winds associated with cold waves emanating from the mongolian anticyclone at present such conditions occur quite frequently in winter but during the coldest phases of the pleistocene they probably also occurred in the spring and summer long range dust transport from northern china to the north pacific requires that the dust is lifted to high levels above 3 km where it can be incorporated into the strong mid latitude westerlies strong vertical motions of the atmosphere occur most frequently in the spring when the mongolian anticyclone begins to weaken and frontal depressions move across the deserts of northern china such frontal depressions were probably more frequent during the climatic optimum of the mid holocene and during previous interglacials changes in continental aridity have probably played a minor role in controlling the magnitude of the dust flux to the north pacific

eurydesma lyonia fauna early permian from the itarare group parana basin brazil a paleobiogeographic w e trans gondwanan marine connection abstract here the biocorrelation of the marine invertebrate assemblages of the post glacial succession in the uppermost portion of the late paleozoic itarare group parana basin brazil is for the first time firmly constrained with other well dated gondwanan faunas the correlation and ages of these marine assemblages are among the main controversial issues related to brazilian gondwana geology in total 118 brachiopod specimens were analyzed and at least seven species were identified lyonia rochacamposi sp nov langella imbituvensis oliveira streptorhynchus sp cyrtella sp tomiopsis sp cf t harringtoni archbold and thomas quinquenella rionegrensis oliveira and biconvexiella roxoi oliveira the presence of tomiopsis sp cf t harringtoni and the bivalve atomodesma aphanaia orbirugata harrington in the teixeira soares beds plus myonia argentinensis harrington and heteropecten paranaensis neves et al both of which recorded in deposits in the teixeira soares and mafra beds butia suggests a biocorrelation with the eurydesma fauna from the bonete formation sauce grande colorado basin argentina furthermore the presence of lyonia archbold and praeundulomya cf subelongata dickins in the taciba formation indicates affinities with deposits in the lyons group carnarvon basin and the fossil cliff member perth basin western australia suggesting a late asselian early sakmarian age even more importantly the collected data suggest the existence of an w e trans gondwanan marine seaway between the parana brazil sauce grande colorado argentina huab hardap shale of the dwyka group aranos area namibia southwest africa the carnavon western australia basins and beyond eastward to the cimmerian region a v proto rift system through two major axes of extensional basin development facilitated the w e marine connection main axes formed by a north northwesterly trending axis paralleling the future south atlantic and a broadly north northeasterly trending line of separation related to the future indian ocean this proto rift system coupled with a sea level rise of at least 100 m favored the establishment of a long narrow shallow seaway allowing the exchange of eurydesma fauna between eastern and western gondwana

earliest permian brachiopod faunas of west central argentina defining the pennsylvanian permian boundary in gondwana abstract late palaeozoic marine successions in the west central argentinian basins have one of the most complete stratigraphic records of the earliest permian in gondwana two brachiopod faunal assemblages characterize this interval the tivertonia jachalensis streptorhynchus inaequiornatus fauna widely documented in the rio blanco and western paganzo basins and the costatumulus amosi fauna identified in the earliest permian successions of the southern calingasta uspallata basin this study reviews the composition and biostratigraphy of these two brachiopod faunas with special reference to their global significance for defining the carboniferous permian boundary in gondwana and deciphering the early permian climate change in western gondwana

size dependence of iron solubility of asian mineral dust particles 1 asian mineral dust was sampled at hokkaido northern japan in spring 2004 and 2006 iron solubility of the bulk aerosol the size segregated aerosol 0 45 4 7 m we suggest that an iron solubility of around 0 4 is typical for asian mineral dust of large particles transported to hokkaido in the high nutrient low chlorophyll region of the western subarctic north pacific near the asian continent where the mineral dust deposition is dominated by large particles the iron solubility of the mineral dust entering the ocean is around 0 4

high precision u pb calibration of carboniferous glaciation and climate history paganzo group nw argentina the duration and geographic extent of carboniferous glacial events in southern gondwana remain poorly constrained despite recent evidence for a more dynamic glacial history than previously considered we report 10 high precision 2 0 1 u pb ages for the permian carboniferous paganzo group nw argentina that redefi ne the chronostratigraphy of the late paleozoic paganzo and rio blanco basins and signifi cantly refi ne the timing of glacial events and climate shifts in the western region of southern gondwana radiometric calibration of the paganzo group indicates three pulses of carboniferous glaciation in the mid visean the late serpukhovian to earliest bashkirian and between the latest bashkirian to early moscovian an abrupt shift in depositional style from high sinuosity single storied fl uvial deposits and clay rich paleosols to low sinuosity multi storied feldspathic fluvial deposits inter calated with eolianites and calcic paleosols is constrained to the latest moscovian and earliest kasimovian these constraints indicate a relatively abrupt climate shift from humid subhumid to nonseasonal semiarid regional climate conditions that occurred signifi cantly earlier than previously inferred early permian this period of high latitude aridity was contemporaneous with a shift to dryland depositional environments and a major vegetation regime shift documented throughout the pangean paleotropics in the pennsylvanian

bulk and single particle mineralogy of asian dust and a comparison with its source soils 1 the mineralogical properties of asian dust have been examined in detail and the results have been compared with the chinese source soils using high resolution scanning electron microscopy transmission electron microscopy x ray diffraction and chemical analysis mineralogical classification of asian dust particles showed that the most common single particles were clay aggregates 48 that were often mixed with nanosized calcite followed by particles of quartz 22 plagioclase 11 coarse calcite 6 k feldspar 5 muscovite chlorite kaolinite amphibole gypsum fe and ti oxides which were either partly or entirely attached with clay size mineral grains the clay minerals in asian dust were mostly illite and interstratified illite smectite the average mineral composition of the bulk dust samples by x ray diffraction was quartz 28 plagioclase 11 k feldspar 8 calcite 8 illite 19 interstratified illite smectite 22 chlorite 2 smectite 1 and kaolinite 1 in the silty soils from the source regions the clay minerals and nanosized pedogenic calcite aggregated and covered silt size minerals while the sands were mostly composed of quartz and feldspars and were lined with clay minerals the mineralogy of asian dust was similar to that of the silty soil from the loess plateau but the total phyllosilicate content increased from desert sands 7 silty soil 23 to asian dust 45 fining eastward the optical properties of asian dust and its interaction with atmospheric gases and cloud are probably affected by the clay rich mineral composition the aggregation and attachment of the clay minerals on the coarser minerals and the nanosized calcite

ice nucleation properties of the most abundant mineral dust phases 1 the ice nucleation properties of the nine most abundant minerals occurring in desert aerosols quartz albite microcline kaolinite montmorillonite illite calcite gypsum and hematite were investigated by environmental scanning electron microscopy esem in this instrument the pure minerals are exposed to water vapor at variable pressures and temperatures the crystallization of ice on the mineral particles is observed by secondary electron imaging and the supersaturation for an activated particle fraction of 1 3 is determined as function of temperature in all experiments condensation of water prior to ice formation was not observed within detectable limits even at water supersaturation the highest temperatures for 1 3 activation vary between 10 c and 16 c for the nine minerals investigated and the corresponding onset relative humidities relative to ice rhi between 107 and 117 supersaturation temperature curves for initial ice formation 1 3 activation in the temperature range typical for mixed phase clouds were measured for all nine minerals the temperature dependence of the onset relative humidity is strongly dependent on mineralogy kaolinite montmorillonite and hematite show a strong increase in rhi with decreasing temperature whereas rhi is almost constant for illite albite quartz and calcite the highly variable ice nucleation properties of the various mineral dust components should be considered for parameterization schemes illite and kaolinite are the most important minerals to consider as they have high ice nucleation efficiency and are common components of desert aerosols

a geochemical study of loess and desert sand in northern china implications for continental crust weathering and composition abstract chemical compositional variations of desert sands and loess loess like deposits river deposits and saline lacustrine deposits collected mostly from the southern margin of the taklimakan desert china provide strong constraints on the chemical weathering processes of continental crust and also on the provenance compositions of these quaternary deposits constant but lower concentrations of al relative to the average upper continental crust ucc in these quaternary deposits could be attributed to chemical weathering of al rich minerals such as feldspar and mica and removal of clay minerals by wind and water large variations of mobile na ca mg and sr compared to relatively immobile al k and ba resulted from the chemical weathering of plagioclase and carbonate minerals salinization and carbonation of the arid lands most trace elements are not significantly fractionated their variations in absolute concentration are caused by the dilution of quartz evaporates and carbonate minerals variations in sn concentrations probably depend on relative contents of some heavy minerals high sr ba low th u k cs ratios of the saline lake deposits suggest differences in aqueous chemistry of these elements the occurrence of the m type tetrad effect a ree pattern with four convex curves of ree compositions found mainly in the river deposits is considered the result of water particle interaction during chemical weathering of crustal materials y ho ratios of these samples are significantly higher than those of chondrite and the ucc this suggests different chemical behavior of these two elements and possibly the enrichment of carbonate materials the low lree hree feature of the saline lake deposits can be interpreted as due to the different aqueous chemical behavior of the ree s however it can also be reasonably considered as the result of inheritance from their provenance since lree and lree hree variations may be related to the geological setting of the source according to some elements that are not significantly fractionated the average provenance composition of these quaternary deposits are probably characterized by enrichments of ni cr and v over fe higher la th lower la sc and th sc and lower ta w and nb w ratios compared with the ucc composition

nanofiber calcite in asian dust and its atmospheric roles 1 calcite is the most important mineral in asian dust and it reacts with atmospheric gases during its long range transport mineralogical and chemical analyses of asian dust and source soils showed two types of calcite that differ greatly in morphology and origin i micron sized irregular particles derived from the erosion of bedrock and ii nanosized fibers that were chemically precipitated in soils in asian dust aerosol particles these nanofibers were internally mixed with clay minerals often coating quartz and feldspar grains together with clay minerals nanofiber bearing aerosol particles were more abundant than the coarser calcite particles the nanofibers reacted to form sulfate coatings on minerals providing a significant contribution to the optical chemical and hygroscopic modifications of asian dust due to their enhanced reactivity asian dust is basically a mineral aerosol and its mineralogical diversity needs to be characterized before a proper estimation of its climatic geochemical and ecological roles and provenance

glacial comminution of quartz sand grains and the production of loessic silt a simulation study abstract traditional views have attributed the formation of loess sized quartz silt particles to glacial processes glacial grinding was considered to be the only mechanism capable of producing loessic silt in the quantities necessary for the formation of loess deposits this idea has been strengthened by the apparent close association between present or former glacierised regions and major global loess deposits however some doubts exist as to whether or not glacial grinding is capable of producing sufficient quantities of quartz silt because of the difficulties entailed in the observations and direct measurement of subglacial abrasion and crushing this paper describes and discusses the results of a simulation study designed to examine abrasion and size reduction of quartz grains under grinding conditions analogous to those experienced in a subglacial environment the findings from these experimental runs suggest that although particle breakage and comminution does occur little silt sized material is actually produced the amount of silt produced ranges from approximately 9 of the original sample in one experimental run to less than 1 for the other seven runs it is suggested that the results obtained may show considerably less abrasion and loessic silt production than may be expected to occur within a natural subglacial environment because 1 subglacial grains experience much greater overburden pressures for much longer periods of time 2 the use of sand sized grains may represent a stable component resistant to further size reduction through crushing or abrasion and 3 the use of a monomineralic sample of relatively sound quartz grains although care must be taken when relating results obtained from these experimental runs to silt production within a glacial environment findings from this work do question whether large amounts of quartz silts are produced within subglacial environments the importance of glacial processes in the formation of loess deposits may lie in the reworking of pre existing sediments by ice rather than the actual production of vast quantities of silt this in turn suggests that care should be taken in the interpretation of the provenance of particles comprising loess deposits

mineralogical composition of african dust delivered by red rains over northeastern spain the african dust deposition mineralogy source regions and influence on rain chemistry were analyzed for a site in the montseny mountains catalonia northeastern spain for the period august 1 1983 through august 1 1994 dust deposition was highly variable two events collected on november 9 11 1984 and march 22 25 1991 accounted for 62 of the total dust input in the 38 red rain events recorded in the period the average annual dust deposition was 5 3 g m 2 se 2 6 three source regions in the african continent were identified with back trajectory analysis 1 western sahara 2 moroccan atlas and 3 central algeria events from the moroccan atlas predominated in terms of number of events amount of rainfall and dust deposition the meteorological situations during red rains were identified western sahara events occurred principally with a depression at high latitudes 50 n forming a trough in the north atlantic moroccan atlas events occurred with a depression in front of portugal and events from central algeria were associated with a depression over spain or north africa by order of abundance median of n 13 the minerals identified in the dust by x ray diffraction were as follows illite quartz smectite palygorskite kaolinite calcite dolomite feldspars differences in mineralogy between source regions were significant for smectite kaolinite quartz and dolomite smectite and kaolinite content was highest in the algerian events while quartz and dolomite content was lowest events from the moroccan atlas had the lowest smectite and kaolinite the red rain soluble chemistry was clearly influenced by the dissolution of calcite high alkalinity calcium concentration and basic ph and by marine components high na cl arid mg 2 concentrations because of the very alkaline character of red rains they had a strong weight on the annual mean ph of rainwater this was reflected by the significant relationship r 0 71 p 0 01 between the percentage of annual precipitation as red rain and annual mean precipitation ph red rains provided 25 45 of the annual dissolved input of the major ions in precipitation and 34 of the calcium required for holm oak quercus ilex l forest growth at the study site