modeling of rainfall triggered shallow landslide by integrating hydrological modeling with the infinite slope stability analysis a rainfall triggered shallow landslide model was developed by iverson water resour res 36 1897 1910 2000 in iverson s model the infiltration capacity is assumed to be equivalent to the saturated hydraulic conductivity for finding pressure heads analytically however for general infiltration process the infiltration capacity should vary with time during the period of rain and the infiltration rate is significantly related to the variable infiltration capacity to avoid the unrealistically high pressure heads iverson employed the beta line correction by specifying that the simulated pressure heads cannot exceed those given by the beta line in this study the suitability of constant infiltration capacity together with the beta line correction for hydrological modeling and landslide modeling of hillslope subjected to a rainfall is examined by amending the boundary condition at ground surface of hillslope in iverson s model the modified iverson s model with considering general infiltration process is developed to conduct this examination the results show that the unrealistically high pressure heads from iverson s model occur due to the overestimation of infiltration rate induced from the assumption that the infiltration capacity is identical to the saturated hydraulic conductivity considering with the general infiltration process the modified iverson s model gives acceptable results in addition even though the beta line correction is applied the iverson s model still produces greater simulated pressure heads and overestimates soil failure potential as compared with the modified iverson s model therefore for assessing rainfall triggered shallow landslide the use of constant infiltration capacity together with the beta line correction needs to be replaced by the consideration of general infiltration process

scale invariance of soil moisture variability and its implications for the frequency size distribution of landslides abstract power spectral analyses of soil moisture variability are carried out from scales of 100 m to 10 km on the microwave remotely sensed data from the washita experimental watershed during 1992 the power spectrum s k has an approximate power law dependence on wave number k with the exponent 1 8 this behavior is consistent with the behavior of a stochastic differential equation for soil moisture at a point and it has important consequences for the frequency size distribution of landslides we present the cumulative frequency size distributions of landslides induced by precipitation in japan and bolivia as well as landslides triggered by the 1994 northridge california earthquake large landslides in these regions despite being triggered by different mechanisms have a cumulative frequency size distribution with a power law dependence on area with an exponent ranging from 1 5 to 2 we use a soil moisture field with the above statistics in conjunction with a slope stability analysis to model the frequency size distribution of landslides in our model landslides occur when a threshold shear stress dependent on cohesion pore pressure internal friction and slope angle is exceeded this implies a threshold dependence on soil moisture and slope angle since cohesion pore pressure and internal friction are primarily dependent on soil moisture the cumulative frequency size distribution of domains of shear stress greater than a threshold value with soil moisture modeled as above and topography modeled as a brownian walk is a power law function of area with an exponent of 1 8 for large landslide areas this distribution is similar to that observed for landslides the effect of strong ground motion from earthquakes lowers the shear stress necessary for failure but does not change the frequency size distribution of failed areas this is consistent with observations this work suggests that remote sensing of soil moisture can be of great importance in monitoring landslide hazards and proposes a specific quantitative model for landslide hazard assessment

mineralogy geochemistry and the origin of high phosphorus oolitic iron ores of aswan egypt abstract the coniacian santonian high phosphorus oolitic iron ore at aswan area is one of the major iron ore deposits in egypt however there are no reports on its geochemistry which includes trace and rare earth elements evaluation texture mineralogy and origin of phosphorus that represents the main impurity in these ore deposits have not been discussed in previous studies in this investigation iron ores from three localities were subjected to petrographic mineralogical and geochemical analyses the aswan oolitic iron ores consist of uniform size ooids with snowball like texture and tangentially arranged laminae of hematite and chamosite the ores also possess detrital quartz apatite and fine grained ferruginous chamosite groundmass in addition to fe 2 o 3 the studied iron ores show relatively high contents of sio 2 and al 2 o 3 due to the abundance of quartz and chamosite p 2 o 5 ranges from 0 3 to 3 4 wt showing strong positive correlation with cao and suggesting the occurrence of p mainly as apatite x ray diffraction analysis confirmed the occurrence of this apatite as hydroxyapatite under the optical microscope and scanning electron microscope hydroxyapatite occurred as massive and structureless grains of undefined outlines and variable size 5 150 m inside the ooids and or in the ferruginous groundmass among trace elements v ba sr co zr y ni zn and cu occurred in relatively high concentrations 62 240 ppm in comparison to other trace elements most of these trace elements exhibit positive correlations with sio 2 al 2 o 3 and tio 2 suggesting their occurrence in the detrital fraction which includes the clay minerals ree ranges between 129 5 and 617 ppm with strong positive correlations with p 2 o 5 indicating the occurrence of ree in the apatite chondrite normalized ree patterns showed lree enrichment over hree la yb n 2 3 5 4 and negative eu anomalies eu eu 0 75 0 89 the oolitic texture of the studied ores forms as direct precipitation of iron rich minerals from sea water in open space near the sediment water interface by accretion of feo sio 2 and al 2 o 3 around suspended solid particles such as quartz and parts of broken ooliths the fairly uniform size of the ooids reflects sorting due to the current action the geochemistry of major and trace elements in the ores reflects their hydrogenous origin the oolitic iron ores of the timsha formation represent a transgressive phase of the tethys into southern egypt during the coniacian santonian between the non marine turonian abu agag and santonian campanian um barmil formations the abundance of detrital quartz positive correlations between trace elements and tio 2 and al 2 o 3 and the abundance mudstone intervals within the iron ores supports the detrital source of fe this prediction is due to the weathering of adjacent land masses from cambrian to late cretaceous the texture of the apatite and the ree patterns which occurs entirely in the apatite exhibits a pattern similar to those in the granite thus suggesting a detrital origin of the hydroxyapatite that was probably derived from the precambrian igneous rocks determining the mode of occurrence and grain size of hydroxyapatite assists in the maximum utilization of both physical and biological separation of apatite from the aswan iron ores and hence encourages the use of these ores as raw materials in the iron making industry

phosphorus in foraminiferal sediments from north atlantic ridge cores and in pure limestones samples of foraminiferal ooze from two north atlantic cores were cleaned and progressively dissolved most of the p fe and mn was released during the first of two reductive cleaning steps most of the remainder of these elements and most of the ca were released during the final acid dissolution step the p in these samples is present largely in fe and mn rich coatings not as a constituent of the foraminiferal shells themselves our results are consistent with those of earlier studies the concentration of p in carbonate oozes in which it is clearly associated with coatings is similar to that of modern calcareous sediments in general and with that of reasonably pure limestones of all ages phosphorus is apparently associated with fe mn oxide coatings in many carbonate sediments the rate of removal of p from the oceans as a constituent of such sediments depends on the rate of formation of fe mn coatings not on the rate of incorporation of p into calcium carbonate

early diagenetic processes in deep labrador sea sediments reactive and nonreactive iron and phosphorus a sequential extraction procedure was applied to separate the oxides and lithogenous phases of iron and manganese and the organic and inorganic phosphorus phases in four box cores and one piston core from the slopes and rises of the labrador sea sedimentation rate rather than the location in the basin appears as a master variable of the diagenetic transformations of fe mn and p high sedimentation rate characteristic of two of the box cores led to the creation of zones near the redox boundary of partial reprecipitation of dissolved fe mn and p released in the deeper reducing portions of the sediments in contrast surficial sediments from box cores with 10 times lower sedimentation rate only have sufficient reductive capacity to remobilize mn hydroxides while leaving the fe oxyhydroxides intact under these conditions there is evidence for a redistribution of reactive inorganic p leading to the crystallization of carbonate fluorapatite in the top 30 cm of the cores gradual transformation of bur

new observations of ambient inclusion trails aits and pyrite framboids in the ediacaran doushantuo formation south china ambient inclusion trails aits are intriguing microtubular structures that commonly occur in association with pyrite in precambrian organic rich cherts and phosphorites they are thought to be created by the migration of pyrite or other crystal grains through a lithified substrate driven by pressure solution from the in situ thermal decomposition of organic matter new phosphorite samples of the ediacaran doushantuo formation south china contain abundant aits exhibiting diverse morphotypes which may be distinguished from filamentous microfossils and endolithic microborings with a suite of morphological criteria based on optical microscopy and scanning electron microscopy sem black shales of the baizhu section contains abundant pyrite framboids whose size distributions reveal significant temporal variations of redox conditions in shallow marine waters that probably promoted the formation of the doushantuo phosphorites aits in the phosphorites are categorized into three types and further into five subtypes i a i b ii a ii b and iii based on their morphologies and observed or interpreted associations with various kinds of terminal pyrite crystals among these subtype ii a single striated microtubes 2 10 m wide are interpreted to have resulted from migration of intact pyrite framboids those of subtype ii b dense clusters of outward radiating microtubes with consistent widths and inward facing cuspate ridges likely have formed by explosive disintegration and propulsion of pyrite framboids due to highly concentrated carbon dioxide gas during the oxidation of organic matter during early diagenesis formation of euhedral and framboidal pyrites involve a suite of biogeochemical and physical processes including non biological oxidation of organic matter and reduction of sulfate in the presence of ferrous iron following the burial of pyrites further oxidative degradation of organic matter produced abundant co2 gas which drives the pyrites to move through the solid but not yet fully lithified phosphatic gel composing granules this model explains the formation of previously reported but unexplained star burst type aits and it may be tested by experimental studies our new observations provide evidence for the widespread occurrence of aits in the doushantuo phosphorites and urge careful petrographic examinations and differentiation between aits and morphologically similar biogenic microstructures

hydromechanical triggering of landslides from progressive local failures to mass release 1 water infiltrating during intense rainfall on steep slopes gradually weakens the wet soil mass inducing localized failures that may initiate a cascade of load redistributions and successive failures propagating across a hillslope the challenge of linking the progressive nature of local events culminating in an abrupt landslide is addressed by a new hydromechanical triggering model that links key hydrologic processes with threshold based mechanical interactions a hillslope is represented as assembly of soil columns interconnected by frictional and tensile mechanical bonds represented as virtual bundles of fibers increasing water load exerted on mechanical bonds causes gradual failure of fibers until restraining forces are exceeded following failure at the soil bedrock interface the load on a column is redistributed to its neighbors via intact mechanical primarily tensile bonds which in turn may also fail and transmit the load downslope as compressive stresses when soil internal compressive strength is exceeded a load bearing column may liquefy and initiate a landslide release that could propagate downslope or retrogressively upslope the model reproduces observed power law frequency magnitude relationships of landslides with exponents ranging between 1 0 and 2 2 in agreement with landslide inventory data we applied a criticality measure defined by ramos 2011 to evaluate the specific influences of slope angle soil texture and root reinforcement on attainment of hillslope criticality in which a small local failure may trigger release of a large soil mass the model provides new insights on the conditions giving rise to an abrupt transition from a seemingly stable hillslope to a catastrophic landslide

topographic controls of landslides in rio de janeiro field evidence and modeling landslides are common features in the serra do mar located along the southeastern brazilian coast most of them associated with intense summer storms specially on the soil mantled steep hillslopes around rio de janeiro city where the favelas slums proliferated during the last few decades on february 1996 hundreds of landslides took place in city of rio de janeiro triggered by intense rainstorms since then many studies have been carried out in two experimental river basins in order to investigate the role played by the topographic attributes in controlling the spatial distribution of landslides inside them landslide scars and vegetation cover were mapped using aerial photographs and field observations a detailed digital terrain model 4 m 2 resolution of the basins was generated from which the main topographic attributes were analyzed producing maps for slope hillslope form contributing area and hillslope orientation by comparing these maps with the spatial distribution of the landslide scars for the 1996 event a landslide potential index lpi for the many classes of the different topographic attributes was defined at the same time field experiments with the guelph permeameter were carried out and a variety of scenarios were simulated with the shalstab model a process based mathematical model for the topographic control on shallow landslides the results suggest that most of the landslides triggered in the studied basins were strongly influenced by topography while vegetation cover did affect landslide distribution between the topographic attributes hillslope form and contributing area played a major role in controlling the spatial distribution of landslides therefore any procedure to be used in this environment towards the definition of landslide hazards need to incorporate these topographic attributes d 2003 elsevier b v all rights reserved

disseminated phosphorus in oceanic sediments a review abstract the content of disseminated phosphorus in sediments of the world oceans fluctuates between 0 01 and 4 36 terrigenous and hemipelagic sediments contain on average about 0 07 phosphorus higher concentrations are characteristic of sediments enriched in iron and manganese hydroxides or bone detritus and phosphoritic material the general features of the phosphorus distribution in surface sediments depend on the ratio of continental runoff area to basin area which diminishes from the atlantic to the indian and pacific areas the relative extent of the nearshore phosphorus rich zone contracts whereas that of the pelagic phosphorus rich zone widens in the transition from the atlantic through the indian to the pacific areas the distribution of phosphorus in vertical sections of sediments gives some evidence of the diagenetic mobilisation of phosphorus and its partial loss to bottom water the rate of phosphorus accumulation in oceanic sediments is evaluated as between 10 g cm 2 k y 1 the bulk mass of phosphorus is accumulated in marginal zones of the oceans

organic carbon cycling and modern phosphorite formation on the east australian continental margin an overview during 1987 the australian bureau of mineral resources conducted a multidisciplinary investigation of the modern phosphorites on the continental margin of southeastern australia between 28 and 32 s the objectives of the work were to examine the processes controlling the cycling of organic carbon and bioactive elements nitrogen phosphorus sulphur and iron in the sediments and to investigate the roles which these processes played in the formation of the modern phosphorites bacterial productivities sulphate reduction rates sedimentary oxygen and pore water concentrations of nitrate ammonia phosphate iron sulphate and fluoride were measured at sea the highest rates of microbial productivity were found in the surficial 0 20 mm sediments of the modern phosphorite zone in 350 460 m water depth these rates were about double those in shallower shelf 300 m sediments and 3 4 fold those rates in mid slope 600 1000 m sediments aerobic and anaerobic oxidation rates of organic matter calculated from sediment oxygen profiles and sulphate reduction rates were highest in the surface sediments in the modern phosphorite zone the recycling of sedimentary iron via reductive dissolution of iron oxyhydroxides and reprecipitation at the oxic anoxic boundary results in a near surface sedimentary trap for iron in the phosphorite zone sediments phosphate released from organic matter in the interfacial sediments and fluoride from seawater are scavenged by iron oxyhydroxides in the top few centimetres of sediment phosphorus in this way is decoupled from organic carbon in the near surface sediments and linked to the redox cycling of iron phosphate and fluoride scavenged onto iron oxyhydroxides and concentrated in the surficial sediments are subsequently released to pore waters in the anoxic sediments when iron oxyhydroxides are buried and dissolve the recycling process releases phosphate and fluoride for incorporation into apatite fluoride is depleted from pore waters at depths 18 cm phosphorite nodules form within anoxic sediments at depths 18 cm and continue to accumulate iron and phosphorus while resident in the mixed layer combinations of rapid sediment mixing rates a slow sedimentation rate and a mixed layer to about 18 cm result in an average particle residence time in the phosphorite zone sediments which is about ten fold that of the mid slope sediments long residence times and rapid mixing promote the oxidation of organic carbon and release of phosphate while the continuous recycling of iron and phosphate concentrates the phosphorus for apatite precipitation and accumulation into phosphorite nodules phosphorite nodules are not found in mid slope sediments probably because of combinations of relatively rapid sedimentation rates ineffective iron phosphorus and fluoride recycling and trapping mechanisms plus dilution and dissemination of any incipient apatite

seismic precursory patterns before a cliff collapse and critical point phenomena 1 we analyse the statistical pattern of seismicity before a 1 2 103 m3 chalk cliff collapse on the normandie ocean shore western france we show that a power law acceleration of seismicity rate and energy in both 40 hz 1 5 khz and 2 hz 10khz frequency range is defined on 3 orders of magnitude within 2 hours from the collapse time simultaneously the average size of the seismic events increases toward the time to failure these in situ results are derived from the only station located within one rupture length distance from the rock fall rupture plane they mimic the critical point like behavior recovered from physical and numerical experiments before brittle failures and tertiary creep failures our analysis of this first seismic monitoring data of a cliff collapse suggests that the thermodynamic phase transition models for failure may apply for cliff collapse

diagenetic formation of interlayer deficient fluorophlogopite as a clay mineral in early cambrian phosphorite lesser himalaya india the trioctahedral analog of illite the occurrence of a trioctahedral analog of illite the dioctahedral interlayer deficient k mica has long been debated due to the inherent difficulties of determining structure and chemical composition of the extremely fine grained material earlier descriptions based on separated material are equivocal here we describe low temperature diagenetic formation of fluorophlogopite which is interlayer deficient and therefore analogous to illite using high resolution in situ methods transmission electron microscopy tem with preparation by focused ion beam milling combined with wavelength dispersive analysis by field emission gun electron microprobe the average composition is k0 5mg2 8v0 01fe0 005 si3 15al0 85o10 oh 0 65f1 35 including minor amounts of nh4 for charge compensation as determined by electron energy loss spectroscopy the k deficient mg mica occurs in layer packages of 10 layers and no indications for interlayering with other sheet silicate layers such as chlorite or vermiculite could be identified with tem x ray powder diffraction patterns of separated material confirm the absence of smectite components the mineral was identified in phosphorites from the lowermost cambrian tal group mussoori syncline lesser himalayas india the rocks are alternating phosphatic mudstones and phosphatic dolostones at times interbedded with phosphate poor carbonate layers which are rich in organic matter sedimentary fluorophlogopite occurs in both rock types and in two textural associations one in vesicles filled with amorphic organic matter the other as reaction rims around illite which contains up to 5 wt v2o3 in its rims textural arguments favor an early diagenetic formation of both v bearing illite and fluorophlogopite closely associated with organic matter and linked to dolomitization the high f content stabilizes phlogopite to low temperatures our findings confirm that the stability field of fluorophlogopite extends from magmatic to metamorphic and sedimentary conditions

weathering profile of non welded ignimbrite and the water infiltration behavior within it in relation to the generation of shallow landslides the mechanism underlying rain induced shallow landslides of non welded ignimbrite is found to be a special type of weathering profile and the behavior of water infiltrating through that profile according to our study of ito ignimbrite in southern kyushu japan rhyolitic volcanic glass the primary component of ignimbrite is first hydrated and dissolved forming halloysite halloysite near ground surface is then transported through the ignimbrite by infiltrating water and becomes clogged in interstices to form clay bands suction monitoring across a weathering profile indicated that downward infiltration of water is disrupted once by a zone of less permeable clay bands and again at the weathering front this disruption at the front is caused by a capillary barrier effect caused by the structure where finer weathered material overlies coarser fresh material this results in a well defined weathering front particularly beneath a slope where water flux is parallel to the front whereas the front is transitional beneath a ridge top where the front is nearly horizontal and the water flux is normal to the front infiltrating water from rain increases the weight of weathered material and decreases the suction within the material which is the final trigger of a shallow landslide of non welded ignimbrite long term weathering which proceeds on the order of years provides slide material

a physically based model for the topographic control on shallow landsliding a model for the topographic influence on shallow landslide initiation is developed by coupling digital terrain data with near surface through flow and slope stability models the hydrologic model topog o loughlin 1986 predicts the degree of soil saturation in response to a steady state rainfall for topographic elements defined by the intersection of contours and flow tube boundaries the slope stability component uses this relative soil saturation to analyze the stability of each topographic element for the case of cohesionless soils of spatially constant thickness and saturated conductivity the steady state rainfall predicted to cause instability in each topographic element provides a measure of the relative potential for shallow landsliding the spatial distribution of critical rainfall values is compared with landslide locations mapped from aerial photographs and in the field for three study basins where high resolution digital elevation data are available tennessee valley in marin county california mettman ridge in the oregon coast range and split creek on the olympic peninsula washington model predictions in each of these areas are consistent with spatial patterns of observed landslide scars although hydrologic complexities not accounted for in the model e g spatial variability of soil properties and bedrock flow control specific sites and timing of debris flow initiation within areas of similar topographic control

role of bacterial mats in oxygen deficient marine basins and coastal upwelling regimes preliminary report bacterial mats play an important role in the sedimentation history of many marine biogenic regimes observations of the living mats suggest that in shallow waters they are dominated by photosynthetic cyanobacteria while in deeper waters the mats are dominated by nonphotosynthetic sulfur oxidizing bacteria fossilized remains of analogous mat structures from the miocene monterey formation are commonly associated with oil producing and phosphate rich zones preliminary observations suggest that bacterial mats may be a source of the organic matter that in time is thermally altered to hydrocarbons

modelling the probability of occurrence of shallow landslides and channelized debris flows using geotop fs this paper describes a coupled distributed hydrological geotechnical model geotop fs which simulates the probability of occurrence of shallow landslides and debris flows we use a hydrological distributed model geotop which models latent and sensible heat fluxes and surface runoff and computes soil moisture in 3 d by solving richards equation numerically together with an infinite slope geotechnical model geotop fs the combined model allows both the hydraulic and geotechnical properties of soil to be considered and realistically modelled in particular the model has been conceived to make direct use of field surveys geotechnical characteristics and soil moisture measurements in the model the depth of available sediments is also used to characterize the hydraulic properties of the area examined to account for the uncertainty related to the natural variability in the factors influencing the stability of natural slopes the safety factor is computed with a probabilistic approach in order to determine the likelihood of slope failures soil parameters are assigned distributions instead of single deterministic values the analysis presented was carried out for an alpine watershed located in the friuli region italy for which some geological and geotechnical data were available in the past this watershed experienced landslides and debris flows during intense storms following long and moderate intensity rainfall events the distributed coupled geotop fs model was calibrated by reproducing some of these events and validated in order to map future failure probabilities

eolian derived siltstone in the upper permian phosphoria formation implications for marine upwelling previously described organic rich shale facies of the meade peak member of the phosphoria formation at soda springs idaho consist of well sorted laminated siltstone containing little or no clay the planar parallel fabric preserved in many of the siltstone beds suggests suspension settling onto the outer shelf or upper slope most likely under low oxygen conditions evidence for transport of silt to the depositional site by sediment gravity flows is absent as are sandstone beds we propose that meade peak siltstone facies record subaqueous deposition of windborne silt that was transported southward from central montana as such they provide the first direct geologic evidence of a wind regime favorable for marine upwelling the process commonly postulated to have localized the deposition of permian phosphatic sediments they may also provide indirect evidence of upwind eolian sand transport at that time

petrography and the ree composition of apatite in the paleoproterozoic pilgujarvi sedimentary formation pechenga greenstone belt russia the first globally significant phosphorous rich deposits appear in the paleoproterozoic at around 2 ga however the specific triggers leading to apatite precipitation are debated we examine phosphorous rich rocks up to 8 wt p2o5 in 1 98 1 92 ga old pilgujarvi sedimentary formation pechenga greenstone belt russia phosphates in these rocks occur as locally derived and resedimented sand to gravel pebble sized grains consisting of apatite cemented muddy sediments phosphatic grains can be subdivided into four petrographic types a d each has a distinct ree signature reflecting different early to late diagenetic conditions and or metamorphic overprint pyrite containing petrographic type d which typically has a flat ree pattern negative ce anomaly and positive eu anomaly is the best preserved of the four types and best records conditions present during apatite precipitation type d phosphatic grains precipitated under sub oxic basinal conditions with a significant hydrothermal influence these characteristics are similar to zaonega formation phosphates of nw russia s onega basin and consistent with phosphogenesis triggered by the development of anoxic sulfidic sub oxic redoxclines at shallow sediment depth during the paleoproterozoic

quaternary phosphorites from the continental margin off chennai southeast india analogs of ancient phosphate stromatolites abstract pleistocene phosphorites occur on the continental margin off chennai abundantly in the depth range of 186 293 m they are associated with outer shelf glauconites and carbonate skeletals including large shells of molluscs and rhodoliths these are primary phosphate deposits and are similar to phosphate stratiform stromatolites this is the first report of phosphate stratiform stromatolites during the quaternary and modern times and they provide a quaternary analog for ancient phosphorites thin sections of phosphorites exhibit laminated phosphatized microbial mats consisting of mechanically deposited clastic particles or of phosphatic molds clay particles are scattered throughout the matrix sem studies reveal that the laminated phosphate matrix is made of thin sheets of tightly packed apatite globules densely packed intertwined microfilaments or filament molds phosphate with obscured laminae is composed of phosphate tubules cell like structures resembling coccoid cyanobacteria or their botryoidal aggregates are common carbonate fluorapatite and low magnesium and high magnesium calcites are the major mineral phases the structural co2 content of apatite ranges from 4 to 5 5 quartz feldspar and goethite are accessory minerals the microbial mats were formed on the outer shelf most probably during conditions of low sea level in the quaternary and microbial processes played a major role in direct phosphatization of these mats the primary phosphorus source seems to have been the continental supply and degradation of organic matter associated with benthic microbial communities the phosphate stratiform stromatolites thus formed were subsequently reworked into a shelf margin depression and resulted in the occurrence of condensed phosphorites

development of progressive landslide failure in cohesive materials the development of progressive failure in slopes is a poorly understood process and relatively few advances in terms of the mechanics of the development of failure have been made since 1967 however advances in the understanding of the development of fractures in brittle materials provide new insights into landslide mechanics in addition the link between the deformation mechanism and movement type allows interpretation of displacement records to determine the mechanisms acting within a slope this paper utilizes these insights into deformation processes combined with reinflation stress path triaxial experiments to propose a new model for the development of a progressive first time failure within a slope this model is able to explain the development of failure when the factor of safety is greater than unity the existence of saito linearity a linear trend when the reciprocal of velocity prior to failure is plotted against time during tertiary creep and the development of failures during periods of apparently increasing normal effective stress

ree y uptake and diagenesis in recent sedimentary apatites abstract rare earth elements and yttrium ree y distribution in authigenic phases are frequently used as proxies for reconstructing past seawater conditions sedimentary apatite precipitates near the sediment water interface and is therefore capable of recording the ree y composition of the overlying water column while the overprinting of primary ree y signal during late stage diagenesis is a widely known phenomenon less is known about early diagenetic effects in this study we investigate the ree y distribution in recent sedimentary apatites found on the namibian shelf using in situ mapping by laser ablation inductively coupled plasma mass spectrometry la icp ms the namibian phosphorite deposits consist of reworked and redeposited pelletal apatitic grains ranging from miocene to pleistocene in age and pristine concretionary apatitic grains that formed during pleistocene to recent the results of this study show that the ree y signatures of pelletal and concretionary apatitic grains are different with both types showing intragranular variability and differences between grain centers and rims the ree y are concentrated in the external part of the apatitic grains forming a 10 20 m wide enrichment zone while the central parts of apatitic grains are low in ree y ree y

the diagenesis of phosphorus in a nearshore marine sediment abstract chemical analyses have been made for total inorganic phosphorus total organic phosphorus and organic carbon in plankton and in anoxic sediments from long island sound u s a when combined with laboratory experiments the measurements of other studies on the same sediments and mathematical modelling the results indicate that 1 1 a large proportion of dissolved phosphate in the upper 10 cm of sediment zone of bioturbation is provided by the release of adsorbed phosphate during the reduction of ferric oxyhydroxides 2 2 below the zone of bioturbation phosphate is liberated to solution solely via organic matter decomposition and the release is stoichiometrically coupled to bacterial sulfate reduction and ammonia formation 3 3 a steady state diagenetic model can be used to predict the profile of organic phosphorus from that of dissolved phosphate at depths below the zone of bioturbation 4 4 the flux of dissolved phosphate out of the sediment must arise largely from phosphate liberation occurring very close 5 5 there is a large preferential loss of phosphorus relative to carbon from organic matter at the time of or prior to burial whereas after burial phosphorus is not lost preferentially at this location

landslides on coastal sage scrub and grassland hillslopes in a severe el nino winter the effects of vegetation conversion on sediment delivery during the 1997 1998 el nino record rainfall triggered 150 shallow landslides within a 9 5 km2 area near santa barbara cal ifornia they were studied to analyze the sediment delivery to val ley floors from landslides in coastal sage scrub and converted grasslands the conversion of coastal sage to grasslands primarily to provide pasturage for cattle is common in the region and the landscape s response may affect water quality reservoir infilling and debris flow hazards we explore the relationship between lateral root reinforcement and landslide volume by developing a slope stability analysis that incorporates root cohesion along the sides of the failure the stability analysis correctly predicts an inverse re lationship between landslide volume and hillslope angle in the sage the volumes of failures in the grasslands do not vary systemati cally with slope and are generally smaller than those in the sage from aerial photograph analysis and field mapping we find that there are 22 9 failures per square kilometer in the grasslands com pared to 13 2 failures per square kilometer in the sage despite the lower failure density in the coastal sage greater failure volumes and longer transport distances delivered more sediment to valley floors with a specific volumetric flux of 2 8 3 10 2 m 3 m 1 for this el nino compared to 1 73 10 2 m 3 m 1 in the grasslands we con clude that the conversion from vegetation with stronger and deeper roots coastal sage to vegetation with weaker and shallower roots grass has caused a pulse of increased landsliding in the grasslands because the soils are currently too thick for the prevailing root reinforcement we suggest that over time soils in the grassland hollows will become thinner as the evacuation by landslides is re peated until the landsliding rate declines to balance the soil sup plied from local colluvium production and diffusive processes upslope

salinity stratification in the permian phosphoria sea a proposed paleoceanographic model the late permian phosphoria formation of the western united states contains 1 7 10 12 t of phosphate and locally as much as 32 9 total organic carbon the mineral wealth of the phosphoria formation is generally attributed to late permian upwelling along the western margin of the continent unlike in most modern environments upwelling in the late permian occurred proximal to a broad shallow evaporative sea rather than an abrupt continental margin evaporite deposits that are contemporaneous with the organic and phosphate rich strata are present within the phosphoria and adjacent basins elevated concentrations of the biomarker gammacerane are ubiquitous in the organic rich facies of the phosphoria formation which suggests that the basin was salinity stratified depositional environments incorporating both upwelling and salinity stratification are unusual and poorly documented in modern settings we infer the presence of salinity stratification in the phosphoria basin and propose a paleoceanographic model of the phosphoria sea during the deposition of organic and phosphate rich sediment from the western margin of the continent upwelling water flowed into the evaporative phosphoria sea replacing and overriding hypersaline bottom water that drained westward this paleoceanographic model of the phosphoria sea may help to explain the distribution and preservation of organic and phosphate rich strata in the phosphoria formation

pore water fluoride in peru continental margin sediments uptake from seawater abstract fluoride analyses display downward decreasing pore water gradients in peru shelf phosphatic muds that require diffusion from the overlying seawater into the sediment column and removal by reaction within the upper few tens of centimeters presumably by incorporation into carbonate fluorapatite the profiles can be modeled as first order f removal with rate constants of 3 yr 1 and asymptotic f concentrations deep in the cores of 35 45 m almost one half the seawater value the integrated flux of fluoride from seawater into organic rich shelf sediments in coastal upwelling zones phosphatic muds yields a contemporaneous global f burial of 0 54 10 10 mol f yr 1 about one fifth the burial in other sinks mostly carbonates and opal the associated burial flux of phosphorus in shelf phosphorites is about 1 6 10 10 mol p yr 1 comparable to p burial in the deep sea with organic matter 1 4 10 10 mol yr 1 and biogenic carbonates 1 4 10 10 mol yr 1 thus phosphorite formation on the peru shelf is a significant contemporaneous process

cenozoic history of phosphogenesis recorded in the ferromanganese crusts of central and western pacific seamounts implications for deepwater circulation and phosphorus budgets abstract ages of seamount phosphatization episodes have been revised for 14 mid plate seamounts in the western and central pacific using the most up to date marine sr isotope curve and 87 sr 86 sr data from the literature the new ages provide a composite geologic history of phosphatization consistent with cenozoic climate history phosphatization on mid pacific seamounts took place only between 36 and 12 ma and it peaked at the eocene oligocene e o transition 34 ma the unprecedented appearance of prominent amounts of phosphorites at the e o transition and frequent recurrences of it afterwards suggests that a new mechanism came into play at that time namely the intensification of the advective flow of bottom water which accelerated the phosphorus cycle in contrast the absence of phosphorites younger than 12 ma suggests another fundamental change in process associated with the shift to a dry and cold climate that probably resulted in a decrease in the riverine input of labile phosphorus the drastic decrease in the frequency of hiatuses in ocean floor depositional records also indicates weakened bottom currents as a possible explanation for the absence of seamount phosphorite since 12 ma a phosphorus flux is a critical variable in modeling the response of the earth system to climate forcing in the geologic past thus the changes in phosphorus flux across the e o boundary and around 12 ma justify further study

model for the prediction of shear strength with respect to soil suction experimental studies on unsaturated soils are generally costly time consuming and difficult to conduct shear strength data from the research literature suggests that there is a nonlinear increas

the phosphorus cycle phosphogenesis and marine phosphate rich deposits abstract phosphorus in the form of phosphate is an essential nutrient and energy carrier on many different levels of life and a key element in mediating between living and lifeless parts of the biosphere one of the most important aspects of the phosphorus cycle is its vital role in governing productivity thereby interacting with the exogenic part of the carbon cycle which in turn is important in regulating earth s climate phosphorus is a prime element to be traced in earth s history because it allows for the reconstruction of long term feedback mechanisms between climate environment and ecology and of global change as such marine sedimentary phosphate deposits are particularly suited to study aspects of the phosphorus cycle because in the case of ubiquity their origin may result from a general acceleration of the global phosphorus cycle sources of sedimentary phosphate are microbial breakdown of buried organic matter and redox driven phosphate desorption from iron and manganese oxyhydroxides dissolved sea water phosphate represents an additional source which may become important in the formation of phosphatic hardgrounds the main locus of phosphogenesis is near the sediment water interface but phosphogenesis also occurs at greater sediment depths current induced winnowing and transport processes along the sea floor concentrate phosphate precipitates into deposits which exhibit internal stratification patterns typical for the prevailing hydraulic energy regime in a sequence stratigraphic context phosphate deposits preferentially occur along marine or maximum flooding surfaces consequent sedimentary reworking may result in the transfer of phosphates to highstand or lowstand deposits bio chemical weathering on continents represents the most significant source of bioavailable phosphorus this implies that long term changes in marine phosphorus levels and with these changes in marine ecology productivity rates and ratios of exported carbonate carbon and organic carbon are a response to changes in continental weathering rates a compilation of marine sedimentary phosphorus burial rates for the last 160 myr suggests that natural variations have occurred that span one order of magnitude for the late jurassic cretaceous and most of the paleogene the phosphorus cycle appears to have been accelerated in times of climate warming which was most likely due to the spreading of zones of humid climate and more intense continental weathering in the neogene the phosphorus cycle appears to have responded to changes in glacially induced weathering this suggests that uniform interpretations with respect to the emplacement of major phosphorite deposits should be treated with caution integrated analyses of the sedimentary and biogeochemical context of phosphorite occurrences may help to identify paleoenvironmental conditions as well as to improve our understanding of periods of enhanced phosphate accumulation periods which were usually characterized by steep gradients in the development of climate and environment with regard to the complexity of feedback mechanisms between the phosphorus cycle and the biosphere the present day input rates of phosphate into the world s oceans should be of great concern they are more than doubled by anthropogenic means and affect ecological systems on a rapidly increasing scale

sedimentary phosphate formation in warm shallow waters new insights into the palaeoceanography of the permian phosphoria sea from analysis of phosphate oxygen isotopes abstract oxygen isotopic analyses of the structural phosphate 18 o p in sedimentary phosphorites of the upper permian phosphoria formation reveal that phosphogenesis occurred across a broad range of palaeoenvironments the 18 o p values from well preserved hand picked phosphate grain separates range from 20 2 to 13 7 0 5 smow with the lowest values in the most landward shallow water deposits and the highest values in the most basinward deeper water deposits the relationship between the maximum burial depth and 18 o p is opposite to that predicted if burial diagenesis was responsible for the isotopic signature of these phosphate grains this suggests that the regional trend in oxygen isotopic data is not due to burial diagenesis the range in oxygen isotopic values does correspond to the potential range of palaeotemperatures in the shallow and broad epicontinental phosphoria sea the range is 14 42 c 3 5 c assuming a seawater 18 o of 2 5 smow palaeotemperatures along an offshore to onshore transect indicate that upwelling involved temperate 14 26 c mean of 21 c but not cold waters and that warming across the palaeoshelf resulted in mean shallow water temperatures of 34 37 c the latter values approximate those predicted by climate and ocean circulation models these warm palaeotemperatures provide further evidence that phosphogenesis in the epicontinental phosphoria sea occurred under palaeoceanographic conditions that were different from modern phosphorite depositional systems this suggests that a purely actualistic approach to the interpretation of the phosphoria phosphorites is not valid

the hydrogen and oxygen isotopic composition of precipitation evaporated mine water and river water in montana usa summary the isotopic composition of 42 samples of rain and snow collected in 2004 were used to construct a local meteoric water line lmwl for butte montana the derived equation d 7 31 18 o 7 5 r 2 0 987 represents one of the first published lmwls based on direct precipitation for any location in the northern rocky mountains samples of underground and surface mine waters in butte including the berkeley pit lake and a nearby tailings pond define a linear trend with a much lower slope and intercept than the lmwl d 5 00 18 o 49 5 r 2 0 991 consistent with non equilibrium evaporation at an average relative humidity of roughly 65 detailed evaporation calculations are presented which indicate that the shallow berkeley pit lake was approximately 25 evaporated in october 2003 whereas the surface of the tailings pond was at least 50 evaporated the intersection of the lmwl and mine water evaporation trend was used to calculate the average composition of recharge water to the flooded mine complex d 139 18 o 18 0 these values are considerably lighter than the weighted total of precipitation for the 2004 calendar year d 118 18 o 15 3 which is partly explained by the unusually low snowfall that montana experienced in 2004 based on this study the lmwl recently proposed by kendall and coplen 2001 kendall c coplen t b 2001 distribution of oxygen 18 and deuterium in river waters across the united states hydrological processes 15 1363 1393 from regression of isotopic data from a number of montana rivers is more accurately interpreted as an evaporation line isotopic trends based on river data should be treated with caution particularly in a semi arid region such as montana where rivers are often influenced by dams and irrigation withdrawals

experimental investigation of f cl and oh partitioning between apatite and fe rich basaltic melt at 1 0 1 2 gpa and 950 1000 c apatite melt partitioning experiments were conducted in a piston cylinder press at 1 0 1 2 gpa and 950 1000 c using an fe rich basaltic starting composition and an oxygen fugacity within the range of iw 1 to iw 2 each experiment had a unique f cl oh ratio to assess the partitioning as a function of the volatile content of apatite and melt the quenched melt and apatite were analyzed by electron probe microanalysis and secondary ion mass spectrometry techniques the mineral melt partition coefficients d values determined in this study are as follows d fap melt 4 4 19 d clap melt 1 1 5 d ohap melt 0 07 0 24 this large range in values indicates that a linear relationship does not exist between the concentrations of f cl or oh in apatite and f cl or oh in melt respectively this non nernstian behavior is a direct consequence of f cl and oh being essential structural constituents in apatite and minor to trace components in the melt therefore mineral melt d values for f cl and oh in apatite should not be used to directly determine the volatile abundances of coexisting silicate melts however the apatite melt d values for f cl and oh are necessarily interdependent given that f cl and oh all mix on the same crystallographic site in apatite consequently we examined the ratio of d values exchange coefficients for each volatile pair oh f cl f and oh cl and observed that they display much less variability k dcl fap melt 0 21 0 03 k doh fap melt 0 014 0 002 and k doh clap melt 0 06 0 02 however variations with apatite composition specifically when mole fractions of f in the apatite x site were low x f 0 18 were observed and warrant additional study to implement the exchange coefficient to determine the h2o content of a silicate melt at the time of apatite crystallization apatite based melt hygrometry the h2o abundance of the apatite an apatite melt exchange k d that includes oh either oh f or oh cl and the abundance of f or cl in the apatite and f or cl in the melt at the time of apatite crystallization are needed f if using the oh f k d and cl if using the oh cl k d to determine the h2o content of the parental melt the f or cl abundance of the parental melt is needed in place of the f or cl abundance of the melt at the time of apatite crystallization importantly however exchange coefficients may vary as a function of temperature pressure melt composition apatite composition and or oxygen fugacity so the combined effects of these parameters must be investigated further before exchange coefficients are applied broadly to determine volatile abundances of coexisting melt from apatite volatile abundances

sedimentary phosphorites an example phosphoria formation southeastern idaho u s a the phosphorous cycle filters through both the biological and geological worlds and sedimentary phosphates exist at the interface between these two portions of the global phosphorous cycle sedimentary phosphates form only when the proper physical conditions and biological activity coincide once deposited the phosphate po43 crystallizes into the mineral carbonate fluorapatite cfa this mineral with substitution of co32 for po43 compositionally falls between the familiar forms of fluorapatite found in igneous and metamorphic rocks and the apatites found in biological material including our own bones and teeth finally through mining and processing it is these sedimentary phosphates that are used as fertilizers and additives for food production and other activities and are subsequently returned to the biosphere the unique settings in which phosphorites form those areas where phosphate is concentrated millions of times above normal and sedimentation rates are drastically slowed are not fully understood and have been the subject of sometimes intense scientific debate over the last century and a half furthermore the mineralogy of these deposits is unique difficult to study and contentious because of our dependence on phosphate for use in fertilizers and other agricultural and chemical uses these deposits are interesting not only from a scientific viewpoint but from an economic standpoint as well however like many mining operations phosphate mining has environmental problems that must be addressed this chapter provides an overview of the salient points in phosphorite formation mineralogy and mining and puts into context the current work being undertaken on the phosphoria formation in southeastern idaho this chapter does not provide a full description of all the sedimentalogical mineralogical and industrial work that has been done on sedimentary phosphates indeed numerous full volumes have been published on phosphorites and more will undoubtedly follow for large scale phosphorites to

authigenic apatite formation and burial in sediments from non upwelling continental margin environments abstract evidence for precipitation of authigenic carbonate fluorapatite cfa in long island sound and mississippi delta sediments suggests that formation of cfa is not restricted to environments of active coastal upwelling we present porewater data suggestive of cfa formation in both these areas application of a sequential leaching procedure designed specifically to separate authigenic carbonate fluorapatite from other phosphorus containing phases including detrital apatite of igneous or metamorphic origin provides strong supporting evidence for authigenic apatite formation in these sediments the size of the authigenic apatite reservoir increases with depth indicating continued formation of cfa during early diagenesis this depth increase is mirrored by a decrease in solid phase organic p at both sites suggesting that cfa is forming at the expense of organic p mass balance considerations application of diagenetic models to interstitial water nutrient data and the saturation state of the interstitial water are consistent with this interpretation diagenetic redistribution of phosphorus among the different solid phase reservoirs is observed at both sites and results in near perfect retention of p by these sediments over the depth intervals sampled formation of cfa in continental margins which do not conform to the classically defined regions of phosphorite formation renders cfa a quantitatively more important sink than has previously been recognized including this reservoir as a newly identified sink for reactive p in the ocean the residence time of p in the modern ocean must be revised downward the implication for ancient oceans of cfa formation in continental margin sediments other than phosphorites is that phosphorite formation may be less a representation of episodicity in removal of reactive p from the oceans than of localized concentration of cfa in phosphatic sediments by secondary physical processes

petrochronology based on ree minerals monazite allanite xenotime apatite ree minerals monazite xenotime and allanite are ree1 minerals sensu stricto because lanthanides la lu and yttrium are critical constituents in them apatite does not require ree but because it contains substantial ree in many rocks it is included in this review all four minerals also host unusually high radionuclide concentrations notably th and u forming the basis of their utility as geochronometers this quartet of accessory minerals is playing an increasingly important role in petrochronology because they provide ways to link robust spot ages to petrogenetic p t conditions so can lend petrogenetic context to chronology based on other minerals part i of this review assembles the basic requisites prior to integrative petrochronologic analysis individual characteristics of the four ree minerals are addressed first i e their crystal chemistry and stability relations thermobarometers and trace element geochemistry used for tracing petrogenesis are discussed next and finally their chronology is summarized part ii presents case studies to highlight the specific strengths of ree minerals used to resolve the dynamics of a broad range of processes from diagenetic to magmatic conditions finally a brief section at the end outlines a few of the current challenges and promising perspectives for future work to introduce the four ree minerals in style let us recall the origins of their names the three phosphates have well respected greek grandparents and allanite has solid scottish roots yet of all four of them show idiosyncracies in etymology or type material apatite had long puzzled naturalists as it shows great chemical and physical variability and can resemble other minerals once properly identified abraham gottlieb werner named it apatite his reasoning referred to the greek root and giving the precise latin translation decipio taken literally both mean i deceive or i mislead which sounds like an apt confession from this mineral for having fooled

fiber bundle model for multiscale modeling of hydromechanical triggering of shallow landslides 1 sudden and rapid mass movements associated with landslides and snow avalanches present a hazard to life and infrastructure yet their predictions and triggering mechanisms remain poorly understood statistical methods and correlative studies have been used to produce landslide or avalanche susceptibility maps often with limited physical basis mechanistic approaches based on factor of safety computation seldom represent the progressive transition from local failure events to a landslide and in general do not include heterogeneities associated with land cover or with subsurface material properties and hydrologic pathways focusing on rainfall induced shallow landslides we propose the use of the fiber bundle model fbm a generic yet powerful and adaptable model used in modeling fatigue and fracture of complex and disordered materials the primary strength of the fbm is its ability to represent the progressive failure of cracks and shear zones and the ruptures of highly heterogeneous bonding elements that are present in soils at all scales the model also provides a natural framework for interpretation of acoustic emission signatures from failing slopes which may form the basis of a monitoring and warning system

landslide rupture and the probability distribution of mobilized debris volumes 1 landslide driven erosion is controlled by the scale and frequency of slope failures and by the consequent fluxes of debris off the hillslopes in this paper we tackle the magnitude frequency part of the process and develop a theory of initial slope failure and debris mobilization that reproduces the heavy tailed distributions probability density function or pdfs observed for landslide source areas and volumes landslide rupture propagation is treated as a quasi static noninertial process of simplified elastoplastic deformation with strain weakening debris runout is not considered the model tracks the stochastically evolving imbalance of frictional cohesive and body forces across a failing slope and uses safety factor concepts to convert the evolving imbalance into a series of incremental rupture growth or arrest probabilities a single rupture is simulated with a sequence of weighted coin tosses with weights set by the growth probabilities slope failure treated in this stochastic way is a survival process that generates asymptotically power law tail pdfs of area and volume for rock and debris slides predicted scaling exponents are consistent with analyses of landslide inventories the primary control on the shape of the model pdfs is the relative importance of cohesion over friction in setting slope stability the scaling of smaller shallower failures and the size of the most common landslide volumes are the result of the low cohesion of soil and regolith whereas the negative power law tail scaling for larger failures is tied to the greater cohesion of bedrock

a seismic landslide susceptibility rating of geologic units based on analysis of characteristics of landslides triggered by the 17 january 1994 northridge california earthquake abstract one of the most significant effects of the 17 january 1994 northridge california earthquake m 6 7 was the triggering of thousands of landslides over a broad area some of these landslides damaged and destroyed homes and other structures blocked roads disrupted pipelines and caused other serious damage analysis of the distribution and characteristics of these landslides is important in understanding what areas may be susceptible to landsliding in future earthquakes we analyzed the frequency distribution and geometries of triggered landslides in the santa susana 7 5 quadrangle an area of intense seismic landslide activity near the earthquake epicenter landslides occurred primarily in young late miocene through pleistocene uncemented or very weakly cemented sediment that has been repeatedly folded faulted and uplifted in the past 1 5 million years the most common types of landslide triggered by the earthquake were highly disrupted shallow falls and slides of rock and debris far less numerous were deeper more coherent slumps and block slides primarily occurring in more cohesive or competent materials the landslides in the santa susana quadrangle were divided into two samples single landslides 1502 and landslide complexes 60 which involved multiple coalescing failures of surficial material we described landslide morphologies by computing simple morphometric parameters area length width aspect ratio slope angle to quantify and rank the relative susceptibility of each geologic unit to seismic landsliding we calculated two indices 1 the susceptibility index which is the ratio given as a percentage of the area covered by landslide sources within a geologic unit to the total outcrop area of that unit and 2 the frequency index given in landslides per square kilometer ls km2 which is the total number of landslides within each geologic unit divided by the outcrop area of that unit susceptibility categories include very high 2 5 landslide area or 30 ls km2 high 1 0 2 5 landslide area or 10 30 ls km2 moderate 0 5 1 0 landslide area or 3 10 ls km2 and low

analytical and observational relations between landslide volume and surface area 1 a remarkable field observation is that landslides of different sizes from different locations around the globe and triggered by different mechanisms all seem to follow a single relation with their volume to surface area ratio following a power law of 1 4 this paper presents an analytical examination of the shape of landslides on the basis of limit equilibrium principles involving the exact mathematical solution of the failure mode the obtained analytical relation between the volume and the surface area of a landslide agrees well with the function obtained from the field observations and hence a mechanical basis is given to the previously poorly understood field observations in addition this paper presents a new graphical interpretation of the factor of safety associated with slope stability analysis and its relation to the probability of failure

landslide volumes and landslide mobilization rates in umbria central italy abstract a catalogue of 677 landslides of the slide type was selected from a global database of geometrical measurements of individual landslides including landslide area al and volume vl the measurements were used to establish an empirical relationship to link al in m2 to vl in m3 the relationship takes the form of a power law with a scaling exponent 1 450 covers eight orders of magnitude of al and twelve orders of magnitude of vl and is in general agreement with existing relationships published in the literature the reduced scatter of the experiential data around the dependency line and the fact that the considered landslides occurred in multiple physiographic and climatic environments and were caused by different triggers indicate that the relationship between vl and al is largely independent of the physiographical setting the new relationship was used to determine the volume of individual landslides of the slide type in the collazzone area central italy a 78 9 km2 area for which a multi temporal landslide inventory covering the 69 year period from 1937 to 2005 is available in the observation period the total volume of landslide material was vlt 4 78 107 m3 corresponding to an average rate of landslide mobilization l 8 8 mm yr 1 exploiting the temporal information in the landslide inventory the volume of material produced during different periods by new and reactivated landslides was singled out the wet period from 1937 to 1941 was recognized as an episode of accelerated landslide production during this 5 year period approximately 45 of the total landslide material inventoried in the collazzone area was produced corresponding to an average rate of landslide mobilization l 54 mm yr 1 six times higher than the long term rate the volume of landslide material in an event or period was used as a proxy for the magnitude of the event or period defined as the logarithm base 10 of the total landslide volume produced during the event or period with this respect the new relationship to link al and vl is a starting point for the adoption of a quantitative process based landslide magnitude scale for landslide events

environmental significance of upper miocene phosphorites at hominid sites in the lukeino formation tugen hills kenya the lukeino formation contains an important sedimentary and fossiliferous record of the late miocene 6 09 5 68 ma which has in particular yielded the fossil remains of the oldest east african bipedal hominid called orrorin tugenensis this fluvio lacustrine sedimentary succession crops out in the kenyan part of the east african rift it is mainly composed of clay to sandy clay deposits intercalated with volcanic ash horizons and localized layers of carbonates and diatomites a detailed sedimentological and mineralogical study of the lukeino formation was conducted to throw light on the environmental conditions in which the hominids lived several centimetric relatively continuous and indurated phosphatic horizons of sedimentary origin were identified at two sites sunbarua and kapcheberek mineralogical xrd and geochemical analyses as well as observations by sem which was coupled with an energy dispersive spectroscopy eds microprobe indicate that the autochthonous phosphate layers are composed of a micritic matrix of francolite 38 93 with incorporation of silicates in variable proportions from one layer to another the phosphate matrix contains very well preserved and abundant diatom frustules in the basal phosphate layer these diatoms are identified as aulacoseira granulata implying a ph of 7 8 8 2 for freshwaters of the palaeolake lukeino calcitic tubular structures linked to a possible bacterial origin are also observed locally phosphate layers occur abruptly within a thick clay sandy series associated with an intense runoff phase during the deposition of this interval of the lukeino formation the massive and cyclic input of phosphorus to the lake promoted productivity to the stage where it caused a diatom bloom the establishment of several phosphate horizons testifies to successive phases of eutrophication of palaeolake lukeino the diatom cells provided some of the organic matter which was decomposed by bacterial activity at the bottom of the lake in suboxic conditions but in insufficient quantities to fully form the phosphatic materials the rest of the organic matter needed for phosphogenesis came from terrigenous supply plant debris suggesting the presence of dense vegetation in the catchment of the palaeolake lukeino during this well drained interval of deposition of the lukeino formation

criticality in earthquakes good or bad for prediction abstract through the analysis of the correlation functions in simulations of an earthquake model the critical properties of the system are studied simulations are performed in a more realistic modification of the olami feder christensen model of earthquakes and result in uncorrelated avalanches distributed following a power law with weak signs of foreshocks and aftershocks the spatial autocorrelation function of the system and other structural variables are computed in every step of the simulation the spatial autocorrelation between points separated from each other by a constant distance equal to 1 4 and 1 8 of the linear size of the system shows large variations temporally correlated with the time series of avalanche size i e spatial correlation values are in average very high before a large earthquake very small after a large earthquake and they evolve between these two states however the temporal average of the spatial autocorrelation over the whole simulation shows values close to zero result that is in contradiction with the idea that the correlation length is of the same order as the linear size of the system diverging in an infinite system which is the main signature of a critical scenario by averaging the autocorrelation in smaller time windows the critical properties of temporal states can be used as an indication of upcoming catastrophic events the structural variables are also correlated with the occurrence of large avalanches suggesting the possibility of monitoring these variables in order to achieve prediction

power law correlations of landslide areas in central italy abstract we have studied the frequency area statistics of landslides in central italy we consider two data sets data set a contains 16 809 landslide areas in the umbria marche area of central italy they represent a reconnaissance inventory of very old old and recent modern landslides the noncumulative frequency area distribution of these landslides correlates well with a power law relation exponent 2 5 over the range 0 03 km 2 a l 2 data set b contains 4233 landslides that were triggered by a sudden change in temperature on 1 january 1997 resulting in extensive melting of snow cover an inventory of these snow melt triggered landslides was obtained from aerial photographs taken 3 months after the event these landslides also correlate well with a power law relation with exponent 2 5 over the range 0 001 km 2 a l 2 we show that the correlation of data set b is essentially identical to the correlation of 11 000 landslides triggered by the 17 january 1994 northridge california earthquake we attribute a rollover for small landslides in data set a to incompleteness of the record due to erosion and other processes and to limitations in the reconnaissance mapping technique used to complete the inventory on the other hand we conclude that rollovers for small landslides in data set b and the california earthquake data are real and are associated with the surface morphology we conclude that the power law distribution is valid over a wide range of landslide areas and discuss possible reasons we also discuss the contribution of the snow melt and earthquake triggered landslide events to the total landslide inventory

origin and age of phosphorite from the south central florida platform relation of phosphogenesis to sea level fluctuations and δ13c excursions abstract francolite carbonate fluorapatite from predominantly peloidal phosphorite grains in the miocene hawthorn group from the babcock deep core southwestern florida is highly substituted with an average composition of ca4 61na0 22mg0 14k0 05sr0 02 po4 2 23 co3 0 62 so4 0 12 f 1 04 13c values of 1 0 7 8 pdb of the francolite co3 indicate a substantial contribution of c from an organic source the sulfur isotopic composition of francolite so4 is depleted to slightly enriched relative to miocene seawater and suggests that phosphogenesis occurred during early burial diagenesis in organicrich sediments above or in the zone of sulfate reduction the uniformly high sr na mg so4 and co3 contents of the francolite the 18o values of the francolite co3 0 2 4 2 pdb and the inclusion of pyrite and organic matter in phosphorite grains suggest that the francolite has had minimal chemical alteration since its formation phosphorite from the babcock deep core has sr 87 86 ratios that range from 0 708148 0 708880 and sr derived ages that range from late oligocene 25 6 0 7 ma to early late miocene 9 2 1 4 ma the sr derived ages of relatively fragile calcareous benthic foraminifers are consistently younger than associated hard tightly cemented phosphorite and support textural evidence of extensive reworking the age of the host sediment ranges from early miocene to pliocene and its depositional history is related to sea level fluctuations approximately three quarters of the total phosphorite in the babcock deep core formed during or within 2 my before the major early to mid miocene positive 13cshift as recorded at dsdp site 588 southwest pacific one third of the total phosphorite formed just prior to the carbon shift in the short interval between 21 9 and 20 4 ma these results indicate that reworked phosphorite deposits may provide a proxy of organic carbon cycling on continental shelves that correspond to sealevel fluctuations and to variations in the 13crecord

early diagenesis of organic matter in peru continental margin sediments phosphorite precipitation abstract pore water chemistry total dissolved co 2 nh 4 no 3 no 2 po 4 si oh 4 ca mg fe mn so 4 h 2 s and f and titration alkalinity solid phase chemistry c org p org c tot n tot f si opal and s ii and sediment characteristics porosity dry bulk density and formation factors were determined on a centimeter scale spacing in the upper 20 40 cm of sediments under intense upwelling areas on the peru continental shelf these data demonstrate that carbonate fluorapatite cfa is precipitating from pore waters in the upper few centimeters of a gelatinous mud with high organic carbon content up to 20 c org very high porosity 0 96 ml cm 3 and very low dry bulk density 3 dissolved phosphate concentrations at the sediment water interface range from 20 to 100 m orders of magnitude higher than bottom water concentrations and much higher than predicted from regeneration of organic matter the mechanism of this interfacial phosphate release is unclear but is apparently uncoupled from carbon and nitrogen metabolism and thus may be linked either to dissolution of fish debris or to the presence of a microbial mat in surficial sediments fluoride is incorporated into cfa by diffusion from the overlying seawater and carbonate ions are provided from pore water alkalinity magnesium concentrations in this reaction zone are not significantly different from those of seawater suggesting that magnesium depletion is not a necessary prerequisite for cfa precipitation the environment of precipitation is interface linked rather than driven by organic diagenesis of phosphorus deeper in the sediment most of the cores display a wide range of diagenetic characteristics below the immediate interfacial region but almost all show the precipitation signature near the interface this interface linked early diagenetic porewater environment for the precipitation of cfa explains many of the geochemical characteristics of phosphorites and provides a testable model to compare the modern phosphogenic analog with ancient phosphorite deposits two of the cores display very high solid phase phosphorus and fluoride contents reflecting the presence of apparently modern pelletal apatites