microscopy and mineralogy of airborne particles collected during severe dust storm episodes in beijing china 1 asia dust storm ads samples were collected during two severe dust storm episodes in beijing china high resolution field emission scanning electron microscopy fesem and environmental scanning electron microscopy energy dispersive x ray detector esem edx coupled with an image analysis system were used to study the morphology chemical compositions and number size distributions of ads particles fesem analysis indicated that beijing ads samples were mainly composed of irregularly shaped mineral particles more than 50 of the ads particles were larger than 1 m measured as equivalent spherical diameter esd image analysis showed that when the dust storm episodes ended in beijing the number of anthropogenic particles such as soot aggregates and coal fly ash in the samples increased and the number of mineral particles decreased analysis of individual ads particles showed that about one fifth of all the particles were mineral aggregates and at least one fourth of the particles contained sulfur x ray diffraction xrd was used to quantify the phase and the clay mineral compositions of ads samples phases in the ads sample collected during the 20 march 2002 dust storm episode included clay minerals noncrystalline materials quartz calcite plagioclase potassium feldspar pyrite hornblende and gypsum in descending order clay minerals were mainly illite smectite mixed layers 78 followed by illite 9 kaolinite 6 and chlorite 7 particulate matter pm less than 10 m were enriched with clay minerals and deficient with quartz by mass compared with the total suspended particulates collected during an ads episode the pm less than 10 m collected during the two severe dust storm episodes was characterized by the absence of dolomite high quartz clay ratio and dominance of illite smectite mixed layers in clay minerals

evolving fluvial transitional marine deposition through the cambrian sequence of jordan abstract the cambrian sequence in jordan crops out in a belt like pattern extending over more than 300 km from the arabian nubian shield source rock in the south located on a stable shelf platform to the invading southern baltic side of the tethys seaway the analysis of the lithofacies association ichnofossil content together with the architecture of fluvial and paralic sandstone bodies reveals the development of the depositional environments of the cambrian deposits of jordan the depositional environment evolved from proximal alluvial fans into major sand flats of braided rivers or directly into distal braidplains dominated by 3 d megaripples in the following depositional phase various marine environments prevailed including platform carbonates clastic carbonate and mixed tidal flats and supratidal sabkhas and less common lagoons all these marine or marine influenced environments changed back into distal braidplains or sand flats of braided streams the latter persisted through the remaining period of the cambrian the study has revealed that shales containing cruziana interbedded within the fluviatile sandstone sequence are time markers that can be used for correlation and could be deposited in a braidplain if the detrital influx was very low it is the latter that enabled the cruziana producing trilobites to migrate from the sea through river mouths to reach distal braidplains and lagoons

geochemistry and mineralogical composition of the airborne particles of sand dunes and dust storms settled in iraq and their environmental impacts five dust storms that occurred in 2008 15 march 11 april 28 april 25 may and 26 june in addition to the many sand dunes disseminated in the western desert of iraq are sampled the worse dust storm that occurred in iraq in 11 april 2008 covered 75 of the iraq area and deposited 6 9 million tons approximately as a total weight of fallout during just 8 h declining temperature 6 c during the episodes of dust storms visibility decreased enormously no more than 30 m many people were taken to hospitals after sustaining breathing problems some of them died clay fraction is the dominant part in the dust storms forming 70 besides a little silt 20 6 and sand 9 4 then classified as mature arkose of clay to sandy clay whereas sand dunes are formed from 72 7 sand 25 1 silt and 2 19 clay then classified as mature arkose of silty sand sand dunes have much maturity mineralogical composition of dust storms and sand dunes are quartz 49 2 67 1 feldspar 4 9 20 9 calcite 38 5 gypsum 4 8 0 4 dolomite 0 8 1 and heavy minerals 3 2 6 6 respectively heavy mineral suites in the dust storms are represented by zircon pyroxene hornblende chlorite and magnetite whereas the sand dunes are represented by zircon tourmaline garnet and pyroxene concentrated within sand fraction heavy minerals according to satellite images revealed the dry land of sahara desert in north africa and the arabian peninsula as well as syria and jordan were a major source of the dust storms that have occurred in asia including iraq

observed evolution of tropical deep convective events and their environment abstract using a compositing technique the temporal progression of tropical convective systems and the mean atmospheric state in their vicinity is constructed from a time series of geostationary satellite and operational rawinsonde data the technique establishes the stage in the life cycle of convection prevailing at a given place and time by a simple objective method using time series of satellite brightness temperature tb histograms collected from a region surrounding the site soundings are classified according to their placement in the convective life cycle and composites formed that represent the areal mean state of the convecting atmosphere at each stage for several scales of horizontal averaging the temporal structure found here for the mesoscale mean atmosphere closely resembles existing observations of the horizontal structure of a tropical squall line albeit with certain reductions in amplitude and stabilization rate this supports the generality of previous findings that the physical m

turbidite provenance in the lower palaeozoic manx group isle of man implications for the tectonic setting of eastern avalonia the provenance of turbidites from the predominantly arenig aged manx group has been constrained using petrographical and geochemical techniques petrographical analysis of sandstones reveals that mono and poly crystalline quartz grains of cratonic origin are dominant major trace and rare earth element concentrations in both sandstones and mudstones complement the petrographical data indicating that the source of the sediments consisted of quartzose basement and mature sedimentary rocks there is little evidence of a juvenile volcanic input but a minor palaeovolcanic component of active continental margin affinity is present there are indications of a more immature character in the oldest units but on the whole geochemical data from the manx group suggest an overall passive margin setting these results suggest that eastern avalonia was attached to gondwana during deposition of the manx group and that iapetus oceanic crust did not subduct beneath the region before the end of the arenig

zonal and vertical structure of the madden julian oscillation abstract a statistical study of the three dimensional structure of the madden julian oscillation mjo is carried out by projecting dynamical fields from reanalysis and radiosonde data onto space time filtered outgoing longwave radiation olr data mjo convection is generally preceded by low level convergence and upward motion in the lower troposphere while subsidence cooling and drying prevail aloft this leads to moistening of the boundary layer and the development of shallow convection followed by a gradual and then more rapid lofting of moisture into the middle troposphere at the onset of deep convection after the passage of the heaviest rainfall a westerly wind burst region is accompanied by stratiform precipitation where lower tropospheric subsidence and drying coincide with continuing upper tropospheric upward motion the evolution of the heating field leads to a temperature structure that favors the growth of the mjo the analysis also reveals distinct differences in the vertical structure

composite life cycle of maritime tropical mesoscale convective systems in scatterometer and microwave satellite observations this study examines scatterometer observed surface wind divergence and vorticity along with precipitable water pw across the life cycle of tropical maritime mesoscale convective systems mcss as resolved in 0 5 data simple composites were constructed around first appearances of cold 210 k cloud tops in infrared ir data at 3 hourly resolution many thousands of such events from the tropical indopacific in 2000 were used composites of subpopulations were also constructed by subdividing the dataset according to ir event size and duration as well as by prevailing values of pw and vorticity at a 5 scale the composite mcs life cycle here spans about a day and covers a few hundred kilometers with a remarkable sameness across subpopulations surface wind convergence and pw buildup lead cold cloud appearance by many hours afterward there are many hours of divergence indicative of downdrafts contrary to motivating hypotheses the strength of this divergence relative to convergence is scarcely different in humid and dry subpopulation composites normalized time series of composite vorticity show an evolution that seems consistent with vortex stretching by this convergence divergence cycle with peak vorticity near the end of the period of convergence 3 h prior to cold cloud appearance in rotating conditions the common 1 day mcs life cycle is superposed on large scale mean vorticity and convergence approximately in proportion which appear to be well scale separated covering the whole of the 48 h and 5 10 averages and are as strong as or stronger than the mcs signature

african dust observed over canary islands source regions identification and transport pattern for some summer situations bulk filtration samples of dust were collected on fuerteventura canary islands in july 1985 in order to investigate african dust transport over this region during summer air mass trajectories and elemental and mineralogical analyses allowed us to distinguish between oceanic and continental influences three african dust transport cases occured during this period geochemical and mineralogical tracers combined with air mass trajectories indicate that two different source regions of dust sahelian and moroccan ones are involved each of these exhibits specific si al and fe al ratios that can be considered as tracers of dust origin a meteorological study based on satellite imagery meteorological maps and air mass trajectories confirms the previous identification of the source region it is also possible to describe the meteorological situation controlling the atmospheric pathway of the dusts from the source regions up to the canary islands this study suggests that some source regions especially the sahelian one of dust affecting the canary islands during summer are rather different from the moroccan ones observed in a spring situation by coude gaussen et al 1987

mechanisms of dike propagation in layered rocks and in massive porous sedimentary rocks the mechanisms of dike propagation are analyzed through detailed examination of small structures associated with the dike intrusion exposures in the ramon area israel offer an opportunity to evaluate theoretical models of tensile fracture propagation and to better understand the factors governing the dike geometry dike related structures are studied in two jurassic units the ardon formation a well stratified sequence of shales and dolomites and the inmar formation which is composed of porous massive sandstones with a few shale lenses it is shown that for the different host rocks the propagation mechanisms and structures differ significantly dikes in the ardon formation are dominated by 1 20 m wide segments confined to distinct layers the mechanisms of segment containment are determined by calculating the stress intensity factor for an extension crack approaching a mechanical interface it is apparent that dike segmentation and containment is controlled mainly by in situ stress and shear moduli differences between adjacent layers and partly by bedding plane slippage dikes in the inmar formation are dominated by smaller segments and by 1 10 cm wide and 10 100 cm long fingers with intermittent smooth patches and slickensides opposite dike walls display exact mirror images of these features dikes propagate in alternating stages of viscous flow and brittle deformation the viscous stages include fluidization of the sandstone by the dike related fluids and increase of the pore pressure in the rock a viscous instability develops between the highly viscous fluidized sandstone and the less viscous dike related fluids forming a zone of viscous fingering in front of the dike stages of brittle fracturing occur when the pore pressure is released and the flux of fluids is insufficient to fluidize the rock

sand composition in an iberian passive margin fluvial course the tajo river the tajo river the 10th largest river in europe drains part of the western passive margin of europe that includes multiple tectonic elements of the iberian plate modern fluvial sand composition in the tajo river drainage basin reflects the nature of the source region which lies in the central part of the iberian peninsula four fluvial petrographic provinces a b c and d can be established in the tajo drainage basin corresponding well with the four principal structural units drained 1 the iberian range 2 the hesperian massif 3 the tertiary tajo basin and 4 the neogene santarem lisboa basin province a corresponds to the tajo river head and is characterized by quartzolithic sedimenticlastic sands qm67f4lt29 and rs79rg3rm18 these sands have been derived from diverse mesozoic siliciclastics and carbonates of the iberian range province b appears in the upper reaches of the tajo river course and is quartzofeldspathic qm57f34lt9 with diverse rock fragments rs34rg23rm43 sources are hercynian granitoids and metasediments and neogene clastics and minor carbonates of the tertiary tajo basin province c extends along the middle course of the tajo river with quartzofeldspathic metamorphiclastic sand modes qm60f33lt7 rs4rg21rm75 the sources are metamorphic rocks intruded by plutonites of the hesperian massif province d is quartzofeldspathic qm55f39lt6 with a dominance of phaneritic rock fragments rs5rg33rm62 and corresponds to the lower reaches of the tajo river where siliciclastic deposits of the neogene santarem lisboa basin are the main sources sands plot on provenance discrimination diagram qmflt within the recycled orogen field tajo river head and continentalblock fields upper middle and lower course in addition we have proven the usefulness of the rsrgrm diagram to discriminate the defined fluvial provinces originating from heterogeneous parent rock textures and mineralogy climate does not exert any strong influence on the petrogenesis of the tajo river drainage basin sand and erosion in the source areas may be described in terms of weathering limited denudation regime by contrast mixing with tributary supplies is the main process that modifies composition in the tajo river sand the establishment of fluvial provinces related to the main bedrock structural units reflects the great relevance of tributaries from each province in the generation of the tajo river sand and the low significance of inherited sandy load from previous provinces the abundance of granitoid rock fragments rsrgrm rg in fluvial sand of both tributaries and main channel of the tajo river drainage basin faithfully represents the relative abundance of granodiorite monzogranite bedrock exposure in each subbasin metasedimentary and metamorphic bedrock outcrop area is overrepresented by metamorphic rock fragments rsrgrm rm in both sand from tributaries and from the tajo main trunk river this is manifested by differences of 18 23 between means of metasedimentary outcrop area and the rsrgrm rm mean in the sand from provinces b and c d respectively sedimentary mainly carbonate outcrop area is underrepresented or not represented by sedimentary rock fragments rsrgrm rs in sand of the tajo river this underrepresentation causes a difference between means of sedimentary outcrop area and the rsrgrm rs mean of 21 17 1 and 10 7 in sands from province a b and c d respectively this fact confirms the rapid loss of these grains during transport because of their labile nature

role of cumulus congestus in tropical cyclone formation in a high resolution numerical model simulation abstractthe role of cumulus congestus shallow and congestus convection in tropical cyclone tc formation is examined in a high resolution simulation of tropical cyclone fay 2008 it is found that cumulus congestus plays a dominant role in moistening the lower to middle troposphere and spinning up the near surface circulation prior to genesis while deep convection plays a key role in moistening the upper troposphere and intensifying the cyclonic circulation over a deep layer the transition from the tropical wave stage to the tc stage is marked by a substantial increase in net condensation and potential vorticity generation by deep convection in the inner wave pouch region this study suggests that tc formation can be regarded as a two stage process the first stage is a gradual process of moisture preconditioning and low level spinup in which cumulus congestus plays a dominant role the second stage commences with the rapid development of deep convection in the inner pouch region after the air colum

a preliminary morphology of precipitation systems in tropical northern australia a preliminary morphology of convective systems observed in the vicinity of darwin australia is presented several types of tropical convection during monsoonal and break season flow are identified using specific examples and compared with a range of systems observed worldwide in the general context of the bulk richardson number a significant spectrum of convective activity ranging from low shear and low convective available potential energy cape to high shear and moderate to high cape typical of mid latitude severe storms is identified significant differences between monsoonal flow and break season systems are apparent the formation of convective lines perpendicular to the low level shear and the apparent balance between advancing shallow cold pools and the shear are ubiquitous features convective scale downdraughts and mesoscale descent appear to be responsible for redistribution of 700 mb momentum to the planetary boundary layer pel the motion of the break season squall lines appears to result from an equilibrium between the cold pool and the undisturbed environmental pel flow deviations from this balance are hypothesized to result in the observed propagating and non propagating or slow moving modes examples of these modes are given showing the classical continuous development of new cells in a balanced state along the leading edge of long lived squalls and in the propagating case the discontinuous development of new cells on the cold pool ahead of the squall

petrography and geochemistry of the cambro ordovician wajid sandstone southwest saudi arabia implications for provenance and tectonic setting abstract the wajid sandstone of probable cambro ordovician age rests unconformably on peneplained precambrian crystalline rocks on the southeastern margin of the arabian shield the sandstone is composed of varicolored siliciclastic rocks mainly coarse to fine grained sandstones with granule conglomerate and siltstone interbeds displaying diverse sedimentary primary structures such as planar and trough cross bedding and flat bedding they form repeated fining upward cycles typical of deposition from braided streams current indicators indicate that flow was from sw to nne petrographically all samples of the wajid sandstone are of quartz arenite type highly enriched in quartz but poor in heavy minerals feldspar and lithic fragments the provenance and tectonic setting of the wajid sandstone have been assessed using integrated petrographic and geochemical studies petrographic analysis reveals that mono and poly crystalline quartz grains and heavy minerals from metamorphic and igneous rocks of a craton interior setting were the dominant sources chemically major and trace element concentrations in the rocks of the wajid sandstone indicate deposition in a passive continental margin setting petrographic and geochemical data suggest that the sediments were derived from metamorphic and igneous rocks forming the adjacent precambrian basement rocks of the arabian shield and were deposited on a passive continental margin deposition took place after stabilization of the arabian shield following the late precambrian pan african orogeny the wajid sandstone can be correlated with similar deposits elsewhere in arabia and north africa which were deposited on a low lying landmass forming the stable continental margin of the arabian nubian shield flanking the southern margin of the paleo tethys ocean

statistical characteristics of convective clouds over the western ghats derived from weather radar observations x band radar observations at mandhardev 18 04 n 73 85 e are used to investigate statistics of convective clouds over the western ghats during monsoon season june september 2014 convective storms cells are identified using an objective tracking method to examine their spatio temporal variability thus quantifying the time continuous aspects of convective cloud population over the region for the first time an increased frequency of storm location and initiation along the windward mountains compared to coastal and lee side highlights orographic response to southwesterly flow with superimposed diurnal cycle an eastward progression of convective activity from upstream the barrier through windward slopes of mountains over to the lee side is observed storm area height and duration follow lognormal distributions wherein small sized storms contribute more to total population and unimodal distribution of 35 dbz top heights peaking at 5 5 km depicts the dominance of shallow convection storms exhibit a pronounced diurnal cycle with a peak in afternoon hours while the convective area maximum is delayed by several hours to that of precipitation flux cell lifetime and propagation show that cells move with slow speeds and have mean duration of 46 minutes they align east west nearly parallel to mountain ridges and their direction of movement is steered mostly by large scale winds at lower levels based on top heights convective cells are further classified into cumulus congestus and deep clouds in general congestus deep cells are most abundant in the windward leeward side a lead lag relationship between congestus and deep cells indicates midtroposphere moistening by congestus cells prior to deep convection

structural and statistical characterization of joints and multi scale faults in an alternating sandstone and shale turbidite sequence at the santa susana field laboratory implications for their effects on groundwater flow and contaminant transport abstract this paper describes the properties of faults and fractures in the upper cretaceous chatsworth formation exposed at santa susana field laboratory and its surroundings simi hills california where groundwater flow and contamination have been studied for over three decades the complex depositional architecture of this turbidite consisting of alternating sandstones and shales interacting with formative stress conditions are responsible for multi scale fault hierarchies and permeable fractures in which nearly all groundwater flow occurs intensity and distribution of background fractures and their relation to bedding thickness are established for sandstones the dominant lithology the architecture of faults with increasing displacement is described and relationships among fault dimensional parameters captured data from 400 boreholes and piezometers reveal the effect of faults and fractures on groundwater flow large hydraulic head differences observed across fault zones with shale rich cores indicate these structures as cross flow barriers moreover hydraulic head profiles under ambient conditions and pumping tests suggest strong hydraulic connectivity in all directions to depth of hundreds of meters this outcrop based structural characterization relates the horizontal hydraulic conductivity to the observed well connected fracture network and explains the strong vertical connectivity across low hydraulic conductivity shales as faults and sheared fractures provide flow pathways

detrital modes of recent deep sea sands and their relation to tectonic setting a first approximation complete petrographic analyses of modern deep sea sands are surprisingly rare but are needed if problems such as the influence of tectonics on petrology or changes in petrology due to diagenesis are to be understood in ancient sandstones this paper is a first attempt using data from our own study of 80 sands plus data from the literature to establish a baseline for modern deep sea sands with which ancient sandstones can be compared we assigned sands to five plate tectonic categories each of which has a distinct average petrologic composition 1 basins associated with trailing edge continental margins q62f26l12 2 with leading edge continental margins either subduction q16f53l31 or 3 strike slip q34f39l27 4 back arc basins q20f29l51 5 fore arc basins q8f17l75 the amount and type of lithic fragments and the type of feldspar are particularly important discriminators the amount of quartz less so trailing edge and fore arc basins have quite distinctive compositions but back arc basins and basins near the two types of leading edge margins show some overlap and thus may be hard to differentiate in ancient sandstones

the four cumulus cloud modes and their progression during rainfall events a c band polarimetric radar perspective 1 there is no objective definition to separate cumulus congestus clouds from the shallow cumulus and deep clouds this has generated misinterpretation about the role of congestus clouds to promote deep convection through the potential of moistening the middle troposphere in this study an objective identification for the different tropical cumulus modes is found by examining the occurrence frequency of the cloud cell top heights cths and near ground at 2 5 km height rainfall properties of these cells using a three season database of the darwin c band polarimetric radar four cumulus modes were identified namely a shallow cumulus mode with cth in the trade inversion layer 1 3 km a congestus mode with tops in the highly stable middle troposphere 3 6 5 km a deep convective mode with tops in the region of free convection 6 5 15 km and an overshooting convection mode with tops in the tropical tropopause layer cth 15 km the study also investigates the connections between these cumulus modes during heavy rainfall events the congestus mode occurs predominantly from 10 h prior to the peak rainfall event to 2 h past the event the deep cloud populations modes 3 and 4 have their maxima at and shortly after the time of the rainfall peak with maximum occurrence just below the tropical tropopause layer a comparison of the heavy rainfall events occurring in morning oceanic conditions against the afternoon continental conditions revealed a higher ratio of the shallow to the deep cloud population and a shorter transition time from the shallow to the onset of deep population in the morning oceanic conditions than the afternoon land conditions it is also found through the analysis of the large scale moisture budget data set that for both the morning and afternoon events the moistening peaked before the peak in the congestus populations

further analysis of the composite wind and thermodynamic structure of the 12 september gate squall line abstract an objective analysis technique is applied to the time composite wind and thermodynamic fields of the 12 september gate tropical squall line previous subjective analyses described by gamache and houze are confirmed and several new results are obtained in the previous analyses mesoscale upward motion was found in the upper troposphere of the stratiform precipitation region immediately trailing the squall line mesoscale downward motion was found in the lower troposphere of the stratiform region the convective clouds were found to be the source of condensate for more than half of the stratiform precipitation but mesoscale updraft condensation was also found to be substantial in these previous studies thermodynamic structure was not analyzed the wind analyses were limited by the number of levels included and vorticity was not analyzed by employing an objective analysis method in the present study we have refined and extended the previous work by including more levels computing vorticity a

deep convective system evolution over africa and the tropical atlantic in the tropical african and neighboring atlantic region there is a strong contrast in the properties of deep convection between land and ocean here satellite radar observations are used to produce a composite picture of the life cycle of convection in these two regions estimates of the broadband thermal flux from the geostationary meteosat 8 satellite are used to identify and track organized convective systems over their life cycle the evolution of the system size and vertical extent are used to define five life cycle stages warm and cold developing mature cold and warm dissipating providing the basis for the composite analysis of the system evolution the tracked systems are matched to overpasses of the tropical rainfall measuring mission satellite and a composite picture of the evolution of various radar and lightning characteristics is built up the results suggest a fundamental difference in the convective life cycle between land and ocean african storms evolve from convectively active systems with frequent lightning in their developing stages to more stratiform conditions as they dissipate over the atlantic the convective fraction remains essentially constant into the dissipating stages and lightning occurrence peaks late in the life cycle this behavior is consistent with differences in convective sustainability in land and ocean regions as proposed in previous studies the area expansion rate during the developing stages of convection is used to provide an estimate of the intensity of convection reasonable correlations are found between this index and the convective system lifetime size and depth

convection in gate the difficult problem of parameterizing tropical convection in large scale models of the atmosphere led to the global atmospheric research program s atlantic tropical experiment gate whose goal was to improve basic understanding of tropical convection and its role in the global atmospheric circulation a dense network of instrumented ships equipped with upper air sounding equipment and quantitative weather radars were located over the atlantic ocean in the intertropical convergence zone itcz just west of equatorial africa the ship network was supplemented by a fleet of research aircraft and a geosynchronous meteorological satellite the data obtained show that the deep convection in the itcz was concentrated in two types of cloud clusters rapidly moving squall clusters and slowly moving nonsquail clusters the clusters were characterized by large mid to upper level cloud shields or anvil clouds that emanated from penetrative cumulonimbus convection accompanying the deep cumulonimbus in each cluster was a log normal spectrum of smaller convective features ranging from moderate cumulonimbus down to tiny nonprecipitating cumulus the large cumulonimbus were typically grouped within a cluster into one or more mesoscale precipitation features or mpf s which were apparently triggered in mesoscale regions of intensified low level convergence as an mpf matured it developed a region of stratiform precipitation adjacent to its active deep convective cells the stratiform precipitation fell from the anvil cloud associated with the stratiform precipitation were a mesoscale downdraft below the anvil cloud and an apparent mesoscale updraft within the anvil cloud itself above the mesoscale downdraft these mesoscale drafts were distinct from the convective scale updrafts and downdrafts of the cumulus and cumulonimbus cells of the cluster downdrafts both convective scale and mesoscale filled the planetary boundary layer in the vicinity of cumulonimbus with stable air of low moist static energy these wakes of downdraft air exerted a strong control on where future convection broke out the results of gate show that to simulate the effects of tropical convection in large scale numerical models of the atmosphere a variety of phenomena must be accounted for including not only convective scale updrafts and downdrafts but anvil clouds with mesoscale updrafts and downdrafts downdraft induced boundary layer transformations and mesoscale convergence patterns experimentation with ways of including some of these features of tropical convection in large scale diagnostic and prognostic studies is under way but much work remains to be done

provenance analysis and tectonic setting of the ordovician clastic deposits in the southern puna basin nw argentina provenance studies on early to middle ordovician clastic formations of the southern puna basin in north western argentina indicate that the sedimentary detritus is generally composed of reworked crustal material tremadocquartzrich turbidites tolar chico formation mean composition q t 89 f7 l4 are followed by volcaniclastic rocks and greywackes tolillar formation mean q t 33 f42 l25 these are in turn overlain by volcaniclastic deposits mean qt24 f30 l46 of the diablo formation late arenig early llanvirn that are intercalated by lava flows all units were deformed in the ocloyic orogeny during the middle and late ordovician sandstones of the tolar chico formation are characterized by th sc ratios 1 la sc ratios 10 whereas associated fine grained wackes show slightly lower values for both ratios lree light rare earth elements enrichment of the arenites is 50 chondrite eu eu values are between 0 72 and 0 92 and flat hree heavy rare earth elements patterns indicate a derivation from mostly felsic rocks of typical upper crustal composition the e n d t s e d values scatter around 11 to 9 the calculated nd t d m residence ages vary between 1 8 and 2 0 ga indicating contribution by a palaeoproterozoic crustal component the th sc and la sc ratios of the tolillar formation are lower than those of the tolar chico formation normalized ree rare earth elements patterns display a similar shape to paas post archaean average australian shale but with higher abundances of hrees eu eu values range between 0 44 and 1 17 where the higher values reflect the abundance of plagioclase and feldspar bearing volcanic lithoclasts average e n d t s e d values are less negative at 5 1 and nd t d m are lower at 1 6 ga this is consistent with characteristics of regional rocks of upper continental crust composition which most probably represent the sources of the studied detritus the rocks of the diablo formation have the lowest th sc and la sc ratios lower lree abundances than the average continental crust and are slightly enriched in hrees eu eu values are between 0 63 and 1 17 the nd isotopes e n d t s e d 3 to 1 t d m 1 2 ga indicate that one source component was less fractionated than both the underlying early ordovician and the overlying middle ordovician units synsedimentary vulcanites in the diablo formation show the same isotopic composition our data indicate that the sedimentary detritus is generally composed of reworked crustal material but that the diablo formation appears to contain 80 of a less fractionated component derived from a contemporaneous continental volcanic arc there are no data indicating an exotic detrital source or the accretion of an exotic block at this part of the gondwana margin during the ordovician

transient environmental sensitivities of explicitly simulated tropical convection abstract a three dimensional cloud resolving model maintained in a statistically steady convecting state by tropics like forcing is subjected to sudden 10 min stimuli consisting of horizontally homogeneous temperature and or moisture sources with various profiles ensembles of simulations are used to increase the statistical robustness of the results and to assess the deterministic nature of the model response for domain sizes near contemporary global model resolution the response to middle and upper tropospheric perturbations is predominantly local in the vertical convection damps the imposed stimulus over a few hours low level perturbations are similarly damped but also produce a vertically nonlocal response enhancement or suppression of new deep convective clouds extending above the perturbed level experiments show that the effective inhibition layer for deep convection is about 4 km deep far deeper than traditional convective inhibition defined for undilute lifted parcels both the local

vertical structure of the tropical boundary layer abstract obsemations presented show that the undisturbed subcloud layer near the itcz resembles that of the trades mixed and transition layers are also seen between cloud drafts during disturbed periods when shallow mixed layers 200 m can persist for several hours modification of the lower atmosphere during disturbed periods is most marked in the lowest 1200 m mixed layers are observed during prolonged disturbed periods disturbed mixed layers are shallower and cooler than undisturbed ones light and moderate rainfall events moisten the mixed layer but mixed layers in the environment around strong rainfall are drier it is hypothesized that that the effect of a number of downdrafts spreading laterally produces the mixed layer cooling and drying observed changes of mixed layer structure with stability measured by the ratio of mixed layer height to the monin obukhov length are presented

activation of diffuse discontinuities and folding of sedimentary layers 1 folding of sedimentary layers is often accommodated by the opening or sliding of inherited and new discontinuities which are assumed here to be diffuse so that a continuum description applies at the fold scale the rock rheology is then described with an elastoplasticity model for which the permanent deformation is of simple shear sliding or dilation opening with respect to specific orientations of the new or inherited diffuse discontinuities to illustrate the relation between folding and activation of diffuse discontinuities a three dimensional layer under compression in the two horizontal directions and sustaining the overburden lithostatic pressure is studied cylindrical buckling occurs either before elastic or after the diffuse discontinuities have been activated if buckling is elastic inherited vertical discontinuities striking obliquely to the fold geometrical axes are activated in a sliding mode in the outer arc leading to a rotation of the principal stress directions opening is then detected across new vertical planes striking obliquely to the fold axis the activation of inherited or new vertical discontinuities can be suppressed if sliding takes place along weak bedding interfaces alternatively early and homogeneous layer parallel shortening marked by a reverse fault mode drastically reduces the critical buckling load compared to the euler load and modifies the final geometry of buckling which is then more of a circular dome shape the switching in buckling mode results in the fold limbs in a change from the early reverse fault to a strike slip fault sliding and to opening across diffuse planes oriented consistently with the final circular structure

the lower palaeozoic of oman and its context in the evolution of a gondwanan continental margin the lower palaeozoic haima group of the sultanate of oman comprises a sequence dominated by siliciclastic rocks up to several kilometres thick and broadly divisible into two groups the sequence is known in outline from subsurface exploration but recent field work on outcrops in the isolated huqf area in east central oman has allowed a more detailed environmental interpretation of the succession at the base coarse continental deposits of the lower haima group rest unconformably on precambrian lower cambrian huqf group sediments mainly carbonates and evaporites the overlying upper haima group comprises from base to top the aeolian dominated amin formation the non marine coastal plain to shallow marine intertidal subtidal sediments of the andam formation the non marine to marginally marine ghudun formation and the complex cyclical deep to shallow water deposits of the safiq formation correlation of the haima group of oman with the lower palaeozoic of the arabian peninsula north africa and iran allows the evolution of the gondwanan margin to be modelled a widespread lower cambrian sequence of coarse alluvium resting on peneplained upper precambrian infracambrian huqf group strata represents the final stage of uplift and basin fill associated with the late proterozoic suturing of arabia and adjacent plates which resulted in the formation of the gondwanan continent the overlying thick sequence of continental fluvial and aeolian sediments was deposited in a series of stable intracratonic basins across the gondwanan landmass in the mid and late cambrian an overall sea level rise led to the repeated development of shallow marine shelf carbonates across the margin the subsequent replacement of this marginal carbonate sequence with a thick marginal to non marine sand dominated sequence may reflect the interplay of several events the drift of gondwana towards more southerly latitudes a phase of strong tectonic rejuvenation during the latest cambrian early ordovician and or a eustatic fall in sea level organic rich marine mudrocks were deposited over much of the gondwanan platform during a series of marked eustatic sea level rises during the mid late ordovician and early silurian in oman no evidence has yet been found for the significant late ordovician glacial event recorded from north africa and saudi arabia

the role of pressure solution seam and joint assemblages in the formation of strike slip and thrust faults in a compressive tectonic setting the variscan of south western ireland abstract the ross sandstone in county clare ireland was deformed by an approximately north south compression during the end carboniferous variscan orogeny the initial assemblage consists of mutually abutting orthogonal arrays of 170 oriented set 1 joints veins jvs and approximately 75 oriented set 1 pressure solution seams psss formed under the same stress conditions orientations of splay jvs and psss set 2 suggest a clockwise remote stress rotation of about 35 responsible for the contemporaneous shearing of the set 1 arrays among these nearly orthogonal strike slip faults the prominent set is sub parallel to set 1 jvs these faults are formed by the linkage of en echelon segments with broad damage zones responsible for right lateral offsets of hundreds of meters thrust faults with up to 30 m of offset initiate within shale horizons and follow either the psss in the sandstones or high angle shales within tilted sequences within the large thrust fault zones compartmentalised blocks of rocks are bounded by thrust faults segments with various dip angles strike slip and thrust faults are contemporaneous and owe their existence to initial weaknesses in the form of jvs and psss rather than by switching relative stress magnitudes and orientations associated with andersonian models of faults and related stress orientations

behavior of deep convective clouds in the tropical pacific deduced from isccp radiances abstract we analyze the properties of deep convection over the equatorial pacific and its relationship to sea surface temperature sst and surface wind divergence using isccp radiance data for july 1983 and january 1984 deep convective clouds dcc are diagnosed with both a combined visible infrared threshold method and an infrared only threshold method the visible channel is important in diagnosing deep convection in different regions with different surface and atmospheric properties because of the existence of large scale variations of dcc top altitudes the itcz and spcz exhibit changes in these two months that are characteristic of both the el nino and seasonal cycles deep convection is latitudinally confined to a much smaller spatial scale than that suggested by maps of outgoing longwave radiation diurnal variations of dcc cover and associated mesoscale cirrus anvil cloud cac cover are out of phase with deep convection peaking in the early morning throughout the equatorial pacific the diurna

structural characterization of deep water deposits in a foreland basin silla syncline chilean patagonia with applications to depositional processes abstract based on our detailed structural characterization we examine possible relationships between thrust faults and strike slip faults and thrust cored folds and depositional units in the silla syncline a 4 km wide fold composed of fine grained mudstone coarse sandstone and conglomerate deposits of the cerro toro formation in the magallanes foreland basin chilean patagonia the syncline is bounded on its western flank by an asymmetric anticline and on its eastern flank by a broad zone of thrust faults and associated folds which are oriented sub parallel to the syncline axis deposition of the coarse grained units of the silla syncline appears to have taken place in this structurally defined trough controlled primarily by thrust fault related growth structures flanking the syncline the syncline and surrounding area have also been deformed by two sets of strike slip faults one right lateral and one left lateral the strike slip and thrust faulting operated contemporaneously for much of their active periods although it appears that thrust faulting confined within the fine grained units initiated slightly earlier than strike slip faulting in addition younger igneous intrusions at high angle to bedding generally localize along the strike slip faults the cross cutting relationships among the intrusions strike slip faults and flexural slip faults show that all these structures were active during the same period which extends beyond mid miocene these conclusions support the premise that structures in deep water sediments are important for understanding not only the deformation of a foreland basin but also its depositional architecture

submarine slope systems processes and products understanding of the processes operating on submarine slopes the preserved deposi tional products and post depositional modifications to sediment body geometries through instabil ity and remobilization requires integration of data from modern slopes with information derived from seismic and outcrop studies of ancient slope successions although local factors are important key generic concepts that aid in predicting submarine slope processes and products include 1 shelf accommodation lateral sediment supply variations on sediment delivery 2 the spatial tem poral distribution of characteristic styles intensities of sediment instability and remobilization and 3 a generalized model for the stratigraphic development of slope channel complexes slope fans and the temporal relationships between these major components of slope stratigraphy key remaining problems include bridging the gap between the timescales sampled by recent to late quaternary studies and those represented by ancient slope successions moreover present day highstand conditions may not provide a good analogue for lowstand slope settings future research efforts will also concentrate on better calibration of seismic facies to rock facies and linking of physical and numerical process and forward modelling techniques at different scales to observa tional datasets the future lies in integration of these complementary research directions

eastward propagating intraseasonal oscillation represented by chikira sugiyama cumulus parameterization part i comparison with observation and reanalysis abstractthe eastward propagating intraseasonal oscillation represented by the chikira sugiyama cumulus parameterization in an atmospheric general circulation model is compared with observations and reanalyses the scheme is characterized by state dependent entrainment rates that vertically vary affected by the environment the zonal wavenumber frequency power spectrum shows a strong signal corresponding to the madden julian oscillation the eastward propagating feature of the convective region and accompanying anomalous zonal wind structure is well extracted by the first and second modes of the combined empirical orthogonal function ceof with a reasonable explained variance for the first mode though the second mode is not sufficiently reproduced the basic features of the composited anomalous fields including moisture temperature and vertical and zonal winds resemble those of the reanalysis in both the free troposphere and surface air the anomalous free tropospheric moisture exhibits its westward ti

transition from back arc to foreland basin development in the southernmost andes stratigraphic record from the ultima esperanza district chile during the mesozoic evolution of the southernmost andes back arc basin formation in an extensional setting was followed by foreland basin development in a compressional setting a stratigraphic record of this tectonic transition is described from jurassic and cretaceous rock units exposed in the patagonian fold thrust belt at 51 s latitude initiation of an extensional deep marine trough in late jurassic time is documented by interstratified rhyolites and marine mudstones in the tobifera formation development of the early cretaceous rocas verdes back arc basin is recorded by zapata formation submarine slope deposits which draped the west facing passively subsiding cratonic margin of the basin the onset of andean compressional orogenesis and creation of the magallanes foreland basin is marked by the influx of coarse grained sandstone turbidites of the albian cenomanian punta barrosa formation during late cretaceous time the foreland basin configuration consisted of a narrow foredeep trough bounded by a gently sloping foreland ramp on the craton to the east this geometry reflects greater flexural subsidence of the stretched and thermally weakened passive back arc basin margin beneath the load of the obducted rocas verdes basin floor changes in depositional regime and sediment dispersal patterns in the latest cretaceous together with an eastward shift in the magallanes basin depocenter record cratonward migration of deformation in the patagonian fold thrust belt loading of the thicker cratonic lithosphere caused subsidence of the foreland ramp to form a wide flexural basin

a review of deformation pattern templates in foreland basin systems and fold and thrust belts implications for the state of stress in the frontal regions of thrust wedges aesthetically appealing thrust systems and related large scale anticlines in both active and fossil foreland fold and thrust belts and the economic potential associated with the m have captured the interest of structural geologists for many decades as a consequence a large amount of data on sub seismic deformation patterns from thrust related an ticlines is available in the literature we provide a review of deformation pattern templates from fi eld data in foreland fold and thrust belts and show that the most frequent tre nds of sub seismic syn orogenic deformation structures hosted in km scale thrust related folds frequently and pa radoxically indicate a syn th rusting strike slip stress fi eld con fi guration with a near vertical 2 and a sub horizontal 3 rather than a contractional one where the latter is expected to be the vertical principal axis of the stress ellipsoid this a pparent inconsistency between sub seismic syn orogenic deformation structures and stress fi eld orientation is here named the 2 paradox field data support a possible expla nation of the paradox provided by the major role played by i nherited early orogenic extensional deformation struc tures on thrust fault nucleation nucleation of major thru sts and their propagation is facilitated and driven by the positive inversion and linkage of the early orogenic sub s eismic extensional inheritance developed in the foreland basin this process eventually leads to the development of l argereversefaultzonesandcanoccurbothincontractional and strike slip stress fi eld con fi gurations

convectively coupled equatorial waves 1 convectively coupled equatorial waves ccews control a substantial fraction of tropical rainfall variability their horizontal structures and dispersion characteristics correspond to matsuno s 1966 solutions of the shallow water equations on an equatorial beta plane namely kelvin equatorial rossby mixed rossby gravity and inertio gravity waves because of moist processes the tilted vertical structures of ccews are complex and their scales do not correspond to that expected from the linear theory of dry waves the dynamical structures and cloud morphology of ccews display a large degree of self similarity over a surprisingly wide range of scales with shallow convection at their leading edge followed by deep convection and then stratiform precipitation mirroring that of individual mesoscale convective complexes ccews have broad impacts within the tropics and their simulation in general circulation models is still problematic although progress has been made using simpler models a complete understanding of ccews remains a challenge in tropical meteorology

stratigraphic record across a retroarc basin inversion rocas verdes magallanes basin patagonian andes chile the mesozoic evolution of the andean cordillera of southern patagonia is recorded in two formations that are now part of the fold thrust belt the zapata formation and the punta barrosa formation extension in the ultima esperanza region began in the late jurassic with deposition of the marine volcaniclastic tobifera formation and eventually resulted in the full fledged oceanic rocas verdes basin the zapata formation was deposited over a time span of 50 m y in an irregular basin ultimately bordered by an early cretaceous arc to the west it is characterized by interbedded shale and siltstone mostly deposited in shallow water and in areas of oceanic crust emplacement also as deep water hemipelagic deposits sediments of the zapata formation were derived initially from local oceanic upwarps and tobifera highs and later from the ande sitic cover of the juvenile arc and or exhumed oceanic crust the paucity of sandstone in the zapata formation in the ultima esperanza region indicates a highly irregular basin partitioned by prominent horsts with sand deposition confined to sub basins closer to the arc changes in depositional regimes and sediment dispersal patterns related to the onset of andean contraction and formation of the magallanes foreland basin are recorded by sediments of the overlying punta barrosa formation this formation records the evolution of a fold thrust belt on the basis of the multimodal mineralogical and geochemical character of its sandstone and shale the presence of an arc is indicated but nearby andean metamorphic terranes are more significantly represented in punta barrosa sediments stratigraphic details across the zapata and punta barrosa formations indicate that deformation and development of a proto andean cordillera in southern south america was initiated in the late mesozoic and involved conspicuous crustal shortening

modulation of the convectively coupled kelvin waves over south america and the tropical atlantic ocean in association with the madden julian oscillation abstractin this study evidence of the strong modulation of the convectively coupled kelvin wave cckw activity by the madden julian oscillation mjo is presented with a particular focus over the south america and tropical atlantic region the mjo impacts on cckws over this region as noted in anomalous fields of rainfall as well as vertical profiles of wind moisture and temperature are primarily through the modulation of kelvin wave amplitude with secondary effects on vertical structure and little impact on wavenumber cckw activity is enhanced during mjo phases 8 1 and 2 and damped during mjo phases 4 5 and 6 further analyses reveal that the strong modulation of the mjo on the cckw activity could be largely through two factors namely the vertical zonal wind shear and the lower to middle tropospheric specific humidity the cckw activity tends to be enhanced during mjo phases when the easterly vertical wind shear and positive low to midtroposphere moisture anomalies are present and vice ve

characteristics of tropopause penetrating convection determined by trmm and cosmic gps radio occultation measurements distribution and influence of convection in the upper troposphere and lower stratosphere have been investigated case by case or on regional to global scale however previous studies were limited by using proxies for convection or the bias of the tropopause data here the tropopause penetrating convection is investigated based on the sole use of observational products from tropical rainfall measuring mission trmm precipitation radar data and constellation observing system for meteorology ionosphere and climate cosmic the result shows that the frequency of precipitation top heights above the monthly mean tropopause in the tropics is reduced logarithmically if the cold point tropopause is adopted instead of the lapse rate tropopause using the collocated cosmic and precipitation radar observations the tropopause penetrating convection i e the convection with the precipitation top height above the lapse rate tropopause can be found over the summer monsoon regions and some continental regions the averaged relative precipitation top heights of tropopause penetrating convective clusters are about 0 2 0 5 km without significant land ocean difference while equivalent radii of clusters are 2 7 3 5 km over land and 0 2 0 5 km larger than those over ocean these areal and vertical extents are smaller than those reported by previous studies furthermore the collocated temperature profiles show that the tropopause penetrating convection generates warming in the upper troposphere and cooling near the lapse rate tropopause and in the lower stratosphere moreover the tropopause penetrating convection leads to a rapid within 20 min lift of the lapse rate tropopause by the adiabatic lofting within the convection within a 10 km radius

provenance interpretation of quartz by scanning electron microscope cathodoluminescence fabric analysis we used a cathodoluminescence cl detector attached to a scanning electron microscope sem to study patterns of variable intensity cl in quartz grains from a variety of igneous metamorphic sedimentary and shock deformed meteorite impact rocks distinctive fabrics in quartz grains revealed by sem imaged differential cl include zoning healed fractures complex shears planar features shocked quartz dark cl streaks and patches indistinct mottled texture and nondifferential low contrast cl zoning is common in volcanic quartz and some plutonic quartz zoned plutonic quartz is distinguished from volcanic quartz by the presence of closed fractures and dark cl streaks and patches metamorphic quartz displays either an indistinct mottled texture or nearly uniform nondifferential cl quartz from rocks severely deformed by tectonism displays a complex pattern of multiple small scale shears quartz from meteorite impact sites and some system boundaries is characterized by intricate patterns of planar features presumably created by shock metamorphism thus the sem cl fabric analysis technique provides a rapid method for distinguishing quartz from a variety of source rocks

fault and fracture systems in a fold and thrust belt an example from bolivia this paper presents an outcrop analog study of fractures in low porosity sandstones in the subandean thrust belt we analyze the evolution of fault and joint systems in these sandstones quantify their density along the structural trend and identify the main factors controlling their variability we show that faults and joints occur at different scales in a hierarchical fashion as a consequence of progressive shearing the first generation is an orthogonal set of joints one parallel and the other perpendicular to the bedding azimuth shearing along these joints transformed them into small faults and created new sets of fractures oblique to the bedding attitude linkage of these small faults facilitated the formation of larger faults with significant strike slip offset shearing along bedding planes created subvertical splay joints that induced the formation of conjugate normal faults in this thrust belt subordinate strike slip and normal faults are concomitant products of compressive deformation this study documents a hierarchical correspondence between spacing of structural heterogeneities and stratigraphic architecture we measured spacings of joints and outcrop scale faults along the backlimb of the abra del condor anticline we subdivided the structural discontinuities into four main groups joints small faults intermediate faults and fault zones spacing of joints small faults and intermediate faults has a lognormal distribution whereas spacing of fault zones shows a normal distribution the mean of these distributions is about the same as the thickness of the confining stratigraphic intervals therefore spacing and dimensions of joints and faults have a first order relationship to the thickness of the confining stratigraphic sequences

back arc extension in the southern andes a review and critical reappraisal the interpretation that the mafic rocas verdes green rocks complex of the southern andes represents part of the uplifted floor of a late jurassic to early cretaceous back arc basin has proved particularly useful in understanding the geological evolution of the southern andes the north scotia ridge and the antarctic peninsula clear field evidence of the back arc setting of the 9rocas verdes gabbro sheeted dyke pillow lava ophiolitic assemblages has encouraged fruitful petrological and geochemical comparison with mid ocean ridge and marginal basin basalts other onshore ophiolite complexes and archaean greenstone belts uncertainty still surrounds estimates of the original width and depth of the basin as well as the proportion of new mafic crust compared with relict sialic crust in the basin floor these questions are unresolved owing mainly to the considerable lower cretaceous turbiditic basin infill and the effects of mid cretaceous compressional deformation while the field relations clearly indicate that the rocas verdes basin is not an older piece of ocean floor trapped behind a volcanic arc it is not yet clear whether the basin is directly subduction related or falls in the category of back arc leaky transforms like the proto gulf of california or apparent rip off features like the andaman sea

the formation of conjugate normal fault systems in folded sandstone by sequential jointing and shearing waterpocket monocline utah 1 we report conjugate normal fault development by the formation and subsequent shearing of joints during flexure and associated extension of the jurassic wingate and navajo sandstones at the core of the waterpocket monocline utah geometry and structural components across fault zones were quantified from an incipient stage to a relatively well developed stage where the zone is 120 m wide and accommodates more than 3 5 m of slip shearing of joints leads to the formation of splay fractures near the joints tip subsequently these splay fractures are sheared and a new generation of splay fractures forms multiple generations of splay fractures cause the width of the fault damage zone to expand into the surrounding host rock producing unusually wide fault damage zones with respect to fault offset these extensive fault damage zones are stratigraphically confined and develop with low strains at small bed dips during folding the faults formed by this sequential process develop a characteristic fault architecture distinguished by the type of component structures their geometric relationships and their distribution we conclude that cyclic joint formation shearing accompanied by splay fracture formation and repeated shearing produce a geometric pattern similar to a classical conjugate fault system however the mechanism identified here has different implications for fault intersection angles stress inversion and fault architecture

the euphrates tigris karun river system provenance recycling and dispersal of quartz poor foreland basin sediments in arid climate we present a detailed sediment provenance study on the modern euphrates tigris karun fluvial system and mesopotamian foreland basin one of the cradles of humanity our rich petrographic and heavy mineral dataset integrated by sand geochemistry and u pb age spectra of detrital zircons highlights the several peculiarities of this large source to sink sediment routing system and widens the spectrum of compositions generally assumed as paradigmatic for orogenic settings comparison of classical static versus upgraded dynamic petrologic models enhances the power of provenance analysis and allows us to derive a more refined conceptual model of reference and to verify the limitations of the approach sand derived from the anatolia zagros orogen contains abundant lithic grains eroded from carbonates cherts mudrocks arc volcanics obducted ophiolites and ophiolitic melanges representing the exposed shallow structural level of the orogen with relative scarcity of quartz k feldspar and mica this quartz poor petrographic signature characterizing the undissected composite tectonic domain of the entire anatolia iranian plateau is markedly distinct from that of sand shed by more elevated and faster eroding collision orogens such as the himalaya arid climate in the region allows preservation of chemically unstable grains including carbonate rock fragments and locally even gypsum and reduces transport capacity of fluvial systems which dump most of their load in mesopotamian marshlands upstream of the arabian persian gulf allochemical carbonate factory quartz poor sediment from the anatolia zagros orogen mixes with quartz rich recycled sands from arabia along the western side of the foreland basin and is traced all along the gulf shores as far as the rub al khali sand sea up to 4000 km from euphrates headwaters

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