fabric evolution in salem attur shear zone south india and its implications on the kinematics abstract domains of opposing shear sense relative to the overall kinematic framework often add to the ambiguities in the interpretation of movement picture along major shear zones rheologic properties strain partitioning as well as rotation of fabric are the principal mechanisms that contribute to the evolution of fabric during shearing the relative dominance of these mechanisms varies with progressive strain leading to the development of domainal fabric departing from the regional stress strain vectors the salem attur shear zone exhibits imprints of multiphase shearing and domains of meso to micro fabrics indicating opposing shear sense resulting in conflicting interpretations of the regional kinematics since the sense of movement is a major constraint in matching the shear zones in gondwana fragments this paper focuses on understanding the movement picture of the shear zone and the mechanism of evolution of domainal fabric

closed form solution for finger width in sandy soils at different water contents wetting front instability and gravity driven fingers can occur during infiltration in sandy soil these soils overlay many major aquifers finger width and velocity are important parameters in predicting the risk of groundwater pollution in these soils in previous studies closed form solutions were developed for air dry soil in uniformly wet soils where the fingers are much wider predictive finger width equations have failed so far in this paper we simplify further the parlange hill closed form solution for dry soil and show that by taking hysteresis into account it applies to fingers emanating from a point source in a sandy test soil at two widely different moisture contents

comment on piezometric response in shallow bedrock at cb1 implications for runoff generation and landsliding by david r montgomery william e dietrich and john t heffner

preferential flow of a nonaqueous phase liquid in dry sand geotechnical centrifuge testing is used to examine the preferential fingered flow of a nonaqueous phase liquid napl in a uniform dry sand the results of nine experiments containing a total of 87 observations of napl finger behavior are analyzed the observed finger tip velocities range from 0 01 to 0 3 cm s while the observed finger widths range from 0 3 to 3 6 cm from the experimental data it is concluded that asymptotically the napl fingers are not fully saturated for comparison the behavior of water fingers is examined using the same experimental setup in contrast to the napl fingers and in agreement with other work reported in the literature the water fingers are found to be fully saturated in addition it is confirmed that the water finger properties can be well predicted from known porous medium and fluid properties a scaling analysis is presented that allows the napl finger properties to be inferred from models developed to describe water finger properties the analysis predicts napl finger velocities to within 15 and napl finger widths to within 50 if both finger types are assumed saturated by adjusting the analysis to account for the fact that the napl fingers are not fully saturated napl finger widths can be predicted within to 10 and napl finger velocities to within 30

linking hydrological infinite slope stability and land use change models through gis for assessing the impact of deforestation on slope stability in high andean watersheds in the ecuadorian andes episodic slope movements comprising shallow rotational and translational slides and rapid flows of debris and soil material are common consequently not only considerable financial costs are experienced but also major ecological and environmental problems arise in a larger geographical area sediment production by slope movement on hillslopes directly affects sediment transport and deposition in downstream rivers and dams and morphological changes in the stream channels in developing countries world wide slope movement hazards are growing increasing population pressure and economic development force more people to move to potentially hazardous areas which are less suitable for agriculture and rangelands this paper describes the methods used to determine the controlling factors of slope failure and to build upon the results of the statistical analysis a process based slope stability model which includes a dynamic soil wetness index using a simple subsurface flow model the model provides a time varying estimate of slope movement susceptibility by linking land use data with spatially varying hydrologic soil conductivity evapotranspiration soil wetness and soil strength properties the slope stability model was applied to a high andean watershed gordeleg catchment 250 ha southern ecuadorian andes and was validated by calculating the association coefficients between the slope movement susceptibility map of 2000 and the spatial pattern of active slope movements as measured in the field with gps the proposed methodology allows assessment of the effects of past and future land use change on slope stability a realistic deforestation scenario was presented past land use change includes a gradual fragmentation and clear cut of the secondary forests as observed over the last four decades 1963 2000 future land use change is simulated based on a binary logistic deforestation model whereby it was assumed that future land use change would continue at the same rate and style as over the last 37 years 1963 2000 c 2002 elsevier science b v all rights reserved

limits on the validity of infinite length assumptions for modelling shallow landslides the infinite slope method is widely used as the geotechnical component of geomorphic and landscape evolution models its assumption that shallow landslides are infinitely long in a downslope direction is usually considered valid for natural landslides on the basis that they are generally long relative to their depth however this is rarely justified because the critical length depth l h ratio below which edge effects become important is unknown we establish this critical l h ratio by benchmarking infinite slope stability predictions against finite element predictions for a set of synthetic two dimensional slopes assuming that the difference between the predictions is due to error in the infinite slope method we test the infinite slope method for six different l h ratios to find the critical ratio at which its predictions fall within 5 of those from the finite element method we repeat these tests for 5000 synthetic slopes with a range of failure plane depths pore water pressures friction angles soil cohesions soil unit weights and slope angles characteristic of natural slopes we find that 1 infinite slope stability predictions are consistently too conservative for small l h ratios 2 the predictions always converge to within 5 of the finite element benchmarks by a l h ratio of 25 i e the infinite slope assumption is reasonable for landslides 25 times longer than they are deep but 3 they can converge at much lower ratios depending on slope properties particularly for low cohesion soils the implication for catchment scale stability models is that the infinite length assumption is reasonable if their grid resolution is coarse e g 25 m however it may also be valid even at much finer grid resolutions e g 1 m because spatial organization in the predicted pore water pressure field reduces the probability of short landslides and minimizes the risk that predicted landslides will have l h ratios less than 25

response of the u pb chronometer and trace elements in zircon to ultrahigh temperature metamorphism the kadavur anorthosite complex southern india abstract zircon from quartzites in the contact aureole and wider environs of the kadavur anorthosite complex se india was studied by laser ablation icp ms to assess the response of the u pb isotope system and trace element concentrations to ultrahigh temperature uht contact metamorphism 1000 c combined cathodoluminescence imaging and la icp ms analyses show that zircon grains contain detrital cores which yield ages between 3 4 ga and 1 8 ga and exhibit a large spread in ree concentrations these cores are associated with one or two rims that provide concordant age populations at 955 16 ma and 810 7 ma 2 and relatively uniform ree patterns the older ages of ca 955 ma record the imprints of regional early neoproterozoic metamorphism related to rodinia assembly the younger age is interpreted to date anorthosite emplacement and its associated contact metamorphism during a second regional metamorphic episode coeval with the intrusion of a type granites in the area zircon grains from the country rocks away from the anorthosite show additional rims yielding ages from 590 to 490 ma corresponding to regional pan african tectonometamorphism the zircon rims are either newly grown domains or represent recrystallized and re equilibrated parts of precursor zircon discordance is only observed in 25 of the detrital cores these cores have relatively high u concentrations 400 ppm which strongly suggests that pb loss occurred under u ht conditions by partial recrystallization annealing of zircon that had become metamict the preservation of old concordant ages and source ree characteristics by the low u i e weakly to non metamict detrital cores shows that pristine zircon is extremely robust to thermal disturbance and that its u pb systematics can remain unaffected despite multiple u ht metamorphic episodes these observations imply that u pb ages in zircon cannot be reset by volume diffusion under any crustal conditions disturbance of the u pb system in individual zircon crystals or parts thereof can only be achieved by recrystallization of radiation damaged zircon

stability of gravity driven multiphase flow in porous media 40 years of advancements 1 gravity driven multiphase flow in porous media is ubiquitous in the geophysical world the classic case in hydrology is vertical infiltration of precipitation into a soil for homogenous porous media infiltrations are sometimes observed to be stable and laterally uniform but other times are observed to be unstable and produce preferential flow paths since saffman and taylor 1958 researchers have attempted to define criteria that determine instability saffman and taylor s analysis consisted of two regions of single phase flow while parlange and hill 1976 integrated this analysis with the multiphase flow equations to provide testable predictions in the subsequent 40 years great advances have been made determining the complex interactions between multiphase flow and instability theoretically the stability of the standard multiphase flow equations has been verified showing the necessity of extensions to the multiphase flow equations to describe the observed unstable flow experimentally it has been shown that the instability is related to a phenomena in 1 d infiltrations called saturation or pressure overshoot in this review the connection between overshoot and instability is detailed and it is described how models of overshoot can simplify the analysis of current and future models of instability and multiphase flow

higher himalayan shear zone zanskar indian himalaya microstructural studies and extrusion mechanism by a combination of simple shear and channel flow thin section studies of the zanskar shear zone zsz rocks reveal a top to sw and subsequent primary and secondary top to ne ductile shearing brittle ductile and brittle extensions top to sw brittle shear steep normal faulting and fracturing in the proposed two phase model of ductile extrusion of the higher himalayan shear zone hhsz a top to sw simple shearing during 22 18 ma was followed by a combination of top to sw simple shear and channel flow at 18 16 ma the second phase simulates a thin zsz characterized by a top to ne shearing the channel flow component ceased around 16 ma the extruding hhsz entered the brittle regime but the top to sw shearing continued until perturbed by faults and fractures variation in the extrusion parameters led to variable thickness of the zsz shear strain after the extrusion is presumably maximum at the boundaries of the hhsz and falls towards the base of the zsz which crudely matches with the existing data the other predictions 1 spatially uniform shear strain after the first stage 2 fastest extrusion rate at the base of the zsz and 3 a lack of continuation of the zsz along the himalayan trend are not possible to validate due to paucity of suitable data non parabolic shear fabrics of the zsz indicate their heterogeneous deformation

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

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

structural fabric of the southern indian shield as defined by gravity trends abstract southern indian shield represents a mosaic comprised of several smaller structural domains separated by discrete shear zones here we present a horizontal bouguer gravity gradient map of the indian shield south of 14 n to define a continental mosaic of gravity trends domains akin to structural domains the gravity gradient image is based on 7862 newly collected observations merged with 6359 old gravity data this combined dataset delineates structural boundaries of the five gravity domains related to the eastern dharwar craton the eastern ghats mobile belt the extended eastern ghats mobile belt the southern granulite terrain and the western dharwar craton other belts of significant gravity gradients are found associated with the eastern and the western coasts the loci of closepet granite and kolar schist belts do not manifest themselves as boundary zones between two distinct gravity domains of the eastern dharwar craton lack of a gravity gradient across karur oddanchatram kodaikanal and karur kambam painavu trichur shear zones may be attributed to a lack of gravity measurements caused by difficulties in collecting data in topographically difficult terrain the subdued gravity gradient across the palghat cauvery shear zone and a weak gradient across the achankovil shear zone indicates a lithological and or morphological boundary rather than a terrane boundary alternatively structural domains encompassing palghat cauvery and achankovil shear zones may have been in a neighbouring position during the gondwana assembly when pan african thermal perturbation reactivated the structures and reworked partly or totally obliterating earlier crustal fabric

modeling and field evidence of finger formation and finger recurrence in a water repellent sandy soil with prolonged rainfall infiltrating wetting fronts in water repellent soils may become unstable leading to the formation of high velocity flow paths the so called fingers finger formation is generally regarded as a potential cause for the rapid transport of water and contaminants through the unsaturated zone of soils for the first time field evidence of the process of finger formation and finger recurrence is given for a water repellent sandy soil theoretical analysis and model simulations indicate that finger formation results from hysteresis in the water retention function and the character of the formation depends on the shape of the main wetting and main drainage branches of that function once fingers are established hysteresis causes fingers to recur along the same pathways during following rain events leaching of hydrophobic substances from these fingered pathways makes the soil within the pathways more wettable than the surrounding soil thus in the long term instability driven fingers might become heterogeneity driven fingers

new constraints on the early formation of the western dharwar craton india from igneous zircon u pb and lu hf isotopes abstract the western dharwar craton wdc is an archean crustal segment for which the earliest stages of development have remained poorly constrained because the oldest identified lithologies are chronologically indistinguishable despite vastly different compositions and origins i e 3352 110 ma sargur group komatiites and 3342 6 ma hassan gorur ttg gneiss indication for older crust come from ancient detrital zircons 3450 3610 ma although their genetic link to the wdc is purely conjectural in order to bring new understanding to early development of the wdc we studied orthogneisses around the holenarsipur schist belt hsb for their petrography major oxide concentrations zircon u pb geochronology and lu hf isotope systematics our results reveal that the wdc igneous record contains crust older than 3350 ma in the form of a 3410 8 3 6 ma granitic gneiss and inherited zircons with ages ranging from 3295 18 to 3607 16 ma that were found within a 3178 10 ma trondhjemitic gneiss and a biotite rich enclave found within it the presence of muscovite and the peraluminous signature of the granitic gneiss in spite of mildly depleted hf isotopic signature ehf 2 2 0 6 at 3410 8 ma suggest that this sample formed by reworking of a felsic precursor with short crustal residence time possibly marking the beginning of wdc formation the oldest inherited zircons display variable ehf ranging from 10 4 at 3414 ma to 2 3 at 3607 ma that did not seem to have influenced the hf isotopic composition of granitoids of the wdc that formed between 3200 and 3410 ma except perhaps in the sargur area we suggest that the wdc formed remote from continental crust until a crustal block containing 3410 ma zircons was accreted to it 3200 my ago this event resulted in the stabilization of the wdc which is marked by diapiric granitoids to which the 3178 ma trondhjemitic gneiss belongs after 3200 ma the crustal block together with granitoids formed between 3410 and 3200 ma buffered the hf isotopic signature of newly formed granitoids hence indicating that by then the wdc already was a stable continental segment

nature of the crust along kuppam palani geotransect south india from gravity studies implications for precambrian continental collision and delamination abstract closely spaced 3000 gravity measurements around kuppam palani geotransect indicate the presence of an ancient continental collision along the moyar bhavani mettur shear zone and crustal delamination beneath the palghat gap paired gravity anomaly along with the faulted contact dip reversal in seismic reflectivity pattern northward vergence of the southern domain and high pressure temperature granulites exposed on the shevaroy hills are characteristic features of crustal thrusting through a late archaean continental collision along the moyar bhavani mettur shear zone a unified 2 1 2 d gravity model along the seismic line is consistent with a tectonic history in which the eastern dharwar craton has been transported beneath the southern granulite terrain the gravity modeling further defines a 10 km thick high density 2 89 g cm3 crustal body at 10 15 km depth and a moho warped up to a depth of about 38 km beneath the palghat gap the high density intrusive body together with the upwarped moho signifies the crust mantle interaction in the palghat gap region late archaean continental collision and subsequent delamination are suggested as the twin cause mechanism for the present day crustal configuration along the geotransect

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

a distributed slope stability model for steep forested basins a distributed physically based slope stability model dslam based on an infinite slope model a kinematic wave groundwater model and a continuous change vegetation root strength model is presented it is integrated with a contour line based topographic analysis and a geographic information system gis for spatial data extraction and display the model can be run with either individual rainfall events or long term sequences of storms these inputs can be either actual storm records or synthesized random events based on monte carlo simulation the model is designed to analyze rapid shallow landslides and the spatial distribution of safety factor fs in steep forested areas it can investigate the slope stability problem in both temporal and spatial dimensions for example the impact of timber harvesting on slope stability either at a given time or through an extended management period the probability of landslide occurrence for a given year and the delivery of landslide sediments to headwater streams the dslam model was applied in a steep forested drainage of cedar creek in the oregon coast ranges using actual spatial patterns of timber harvesting and measured rainfall during a major storm which triggered widespread landslides in that area in 1975 simulated volume and number of failures were 733 m3 and 4 respectively these values agreed closely with field measurements following the 1975 storm however the effect of parameter uncertainty may complicate this comparison for example when soil cohesion values of 2 0 and 3 0 kpa were used the failure volume changed by factors of 2 04 and 0 41 respectively compared with the average condition of 2 5 kpa used in the simulation for soil depths 30 higher and lower than the standard condition the failure volume changed by factors of 2 0 and 0 27 respectively when maximum root cohesion changed from 12 5 kpa average condition to 10 kpa the failure volume increased 1 73 fold for the case of 15 kpa the failure volume changed by a factor of 0 55 the simulated failures caused by the storm were mostly in hollows the simulations show that the spatial distribution of fs is controlled mainly by topography and timber harvesting patterns and is greatly affected by groundwater flow patterns during major rainstorms most areas with fs 3 0 corresponded with the distribution of blocks clear cut in 1968 and all elements with fs 2 0 were in areas clear cut in 1968 areas with low fs 1 0 1 6 expanded dramatically during the rainstorm and decreased at a slow rate after the storm factors of safety in hollows declined sharply during the storm

implications of channel flow analogue models for extrusion of the higher himalayan shear zone with special reference to the out of sequence thrusting the higher himalayan shear zone hhsz contains a ductile top to n ne shear zone the south tibetan detachment system lower stdsl and an out of sequence thrust oost as well as a top to n ne normal shear at its northern boundary and ubiquitously distributed compressional top to s sw shear throughout the shear zone the oost that was active between 22 ma and the holocene varies in thickness from 50 m to 6 km and in throw from 1 4 to 20 km channel flow analogue models of this structural geology were performed in this work a newtonian viscous polymer pdms was pushed through a horizontal channel leading to an inclined channel with parallel and upward diverging boundaries analogous to the hhsz and allowed to extrude to the free surface a top to n ne shear zone equivalent to the stdsu developed spontaneously this also indirectly connotes an independent flow confined to the southern part of the hhsz gave rise to the stdsl the pdms originally inside the horizontal channel extruded at a faster rate through the upper part of the inclined channel the lower boundary of this faster pdms defined the oost the model oost originated at the corner and reached the vent at positions similar to the natural prototype some time after the channel flow began the genesis of the oost seems to be unrelated to any rheologic contrast or climatic effects profound variations in the flow parameters along the hhsz and the extrusive force probably resulted in variations in the timing location thickness and slip parameters of the oost variation in pressure gradient within the model horizontal channel however could not be matched with the natural prototype channel flow alone presumably did not result in southward propagation of deformation in the himalaya

cretaceous to cenozoic evolution of the northern lhasa terrane and the early paleogene development of peneplains at nam co tibetan plateau abstract highly elevated and well preserved peneplains are characteristic geomorphic features of the tibetan plateau in the northern lhasa terrane north northwest of nam co the peneplains were carved in granitoids and in their metasedimentary host formations we use multi method geochronology zircon u pb and u th he dating and apatite fission track and u th he dating to constrain the post emplacement thermal history of the granitoids and the timing and rate of final exhumation of the peneplain areas la icp ms u pb geochronology of zircons yields two narrow age groups for the intrusions at around 118 ma and 85 ma and a third group records paleocene volcanic activity 63 58 ma in the nam co area the low temperature thermochronometers indicate common age groups for the entire nam co area zircon u th he ages cluster around 75 ma apatite fission track ages around 60 ma and apatite u th he ages around 50 ma modelling of the thermochronological data indicates that exhumation of the basement blocks took place in latest cretaceous to earliest paleogene time by middle eocene time the relief was already flat documented by a thin alluvial sediment sequence covering a part of the planated area the present day horst and graben structure of the peneplains is a late cenozoic feature triggered by e w extension of the tibetan plateau the new thermochronological data precisely bracket the age of the planation to early eocene i e between ca 55 and 45 ma the erosional base level can be deduced from the presence of early cretaceous zircon grains in eocene strata of bengal basin the sediment generated during exhumation of the nam co area was transported by an early cenozoic river system into the ocean suggesting that planation occurred at low elevation

solute leaching in a sandy soil with a water repellent surface layer a simulation many sandy soils in the netherlands have a water repellent surface layer covering a wettable soil with a shallow groundwater table fingers form in the water repellent surface layer and rapidly transport water and solutes to the wettable soil in which the streamlines diverge although several field observations are available this system has not yet been studied systematically in this paper we present a model with a steady state water flow to which solutes are added as a pulse the model predicts the flow through the distribution zone and through the finger in the water repellent surface layer with a closed form solution and transport in the wettable subsoil numerically model calculations show that the travel time through the water repellent surface layer and the thickness and hydraulic conductivity of the wettable soil have the strongest effect on the arrival time of the solute pulse at groundwater level the calculations also show that assuming transport in the wettable subsoil to take place in fingers the travel time is considerably shorter than when the diverging flow in the wettable soil is included

3d lithosphere density structure of southern indian shield from joint inversion of gravity geoid and topography data abstract we present the 3d crustal and lithospheric structure and crustal average density distribution of southern indian shield south of 18 n sri lanka and adjoining oceans the model is based on the assumption of local isostatic equilibrium and is derived from joint inversion of free air gravity and geoid anomalies and topography data the derived crustal thickness of 10 25 km in the oceanic region increases to 34 35 km along the coast a crustal thickness of 34 38 km is obtained beneath the eastern dharwar craton and 36 45 km beneath the western dharwar craton and the southern granulite terrain sri lanka has a thinner crust of 30 35 km the lithosphere asthenosphere boundary is located at depths of 70 120 km under oceanic regions and 150 180 km below the dharwar craton and the northern block of southern granulite terrain a notably thinned lithosphere of 130 km near bangalore in the eastern dharwar craton 140 km beneath the southern block of southern granulite terrain and 130 km in sri lanka is observed the thickness of the lithosphere 130 km near bangalore is inferred as the frozen in signature of a small fossil mantle plume and or tectono compositional effect of a rifted margin and a suture considerable stretching and or convective removal of pristine lithosphere in the southern block of southern granulite terrain and adjoining sri lanka before disappearing completely in the archaean northern block of southern granulite terrain and dharwar craton is suggested

prediction of fingering in porous media immiscible displacement involving two fluids in a porous medium can be unstable and fingered under certain conditions in this paper the original linear instability criterion of chuoke et al 1959 is generalized considering wettability of two immiscible fluids to the porous medium this is then used to predict 24 specific flow and porous medium conditions for the onset of wetting front instability in the subsurface wetting front instability is shown to be a function of the driving fluid wettability to the medium differences in density and viscosity of the fluids the magnitude of the interfacial tension and the direction of flow with respect to gravity scenarios of water and nonaqueous phase liquid infiltration into the vadose zone are examined to predict preferential flow and contamination of groundwater the mechanisms of finger formation propagation and persistence in the vadose zone are reviewed and the existing equations for calculating the size the number and velocity of fingers are simplified for field applications the analyses indicate that fingers initiate and propagate according to spatial and temporal distribution of the dynamic breakthrough water or air entry pressures in the porous medium the predicted finger size and velocity are in close agreement with the experimental results

the triggering of debris flow due to channel bed failure in some alpine headwater basins of the dolomites analyses of critical runoff the debris deposits at the bottom of very steep natural channels and streams in high mountain areas can be mobilized by runoff triggering a water sediment mixture flow known as debris flow the routing of debris flow through human settlements can cause damage to civil structures and loss of human lives the prediction of such an event or the runoff discharge that triggers it assumes an interest in risk analyses and the planning of defence measures the object of this study is to find a method to determine the critical runoff value that triggers debris flow as a result of channel bed failure historical and rainfall data on 30 debris flows that occurred in six watersheds of the dolomites north eastern italian alps were collected from different sources field investigations at the six sites together with the hydrologic response to the rainfalls that triggered the events were performed to obtain a realistic scenario of the formation of the debris flow there occurred field observations include a survey along the channel of the triggering reach of debris flow with measurements of the channel slope and cross section and sampling of debris deposits for grain size distribution simulated runoff discharge values based on the rainfall recorded by pluviometers were then compared with values obtained through experimental criteria on the initiation and formation of debris flow by bed failure the results are discussed to provide a plausible physical based method for the prediction of the triggering of debris flow by channel bed failure copyright 2007 john wiley sons ltd

米国南西部 コロラド川伸張地域 black山脈アコモデーション帯の背斜部分における中新世伸張と伸張しゅう曲運動 原標題は英語

magmatic and metamorphic imprints in 2 9 ga chromitites from the sittampundi layered complex tamil nadu india abstract the ca 2 9 ga old sittampundi layered complex slc of south india belongs to a special group of deformed and metamorphosed archaean rocks where chromitites are interlayered with anorthosite detailed field studies have revealed that the slc comprises of a sequence of magmatic rocks consisting of clinopyroxenite anorthosite and mafic rocks of tholeiitic composition minor bif banded iron formations intercalated with the mafic rocks are the only sedimentary rock within the slc chromitite occurs as continuous to discontinuous bands a few mm up to 6 m thick within clinopyroxenite and highly calcic anorthosite an 99 100 but never in the enclosing mafic rocks chromite occurs broadly in three textural types a cumulus grains in chromitite layers b disseminated grains in clinopyroxenite and anorthosite and c small grains included in clinopyroxene and plagioclase a suite of felsic magma intruded the slc at ca 2 51 ga subsequently the entire rock sequence underwent polyphase deformation and metamorphism at ca 2 50 2 45 ga granulite facies and at 0 72 0 50 ga amphibolite facies during the latter event extensive alteration of clinopyroxene to amphibole and chlorite of plagioclase to clinozoisite and of chromite to cr poor green spinel took place chromite compositions show large variations cr 26 60 mg 4 45 fe 3 2 24 depending upon textural type and nature of the associated phases the most conspicuous compositional variation took place when chromite was metasomatically replaced by green spinel cr 3 21 mg 45 61 during amphibolite facies metamorphism on a cr vs mg plot pristine magmatic compositions of chromite define an array that suggest increasing cr with concomitant decrease in mg presumably during magmatic fractionation highly calcic plagioclase in anorthosite and fe al rich chromite in chromitite in the slc are consistent with a hydrous parental magma of tholeiitic composition this hydrous magma was generated in an oceanic arc environment and crystallized close to the surface of the earth in terms of mineralogy and field relations chromitite bearing rocks of the slc show remarkable similarity with the archaean anorthosite hosted chromitite deposits in layered magmatic complexes at fiskenaesset greenland and messina south africa but contrasts sharply with the chromitite deposits of proterozoic and phanerozoic age a change in the style of arc magmatism appears to be the controlling factor for marked change in chromite compositions across the archaean proterozoic boundary

physically based modelling of shallow landslide sediment yield at a catchment scale a shallow landslide erosion and sediment yield component applicable at the basin scale has been incorporated into the physically based spatially distributed hydrological and sediment transport modelling system shetran the component determines when and where landslides occur in a basin in response to time varying rainfall and snowmelt the volume of material eroded and released for onward transport and the impact on basin sediment yield derived relationships are used to link the shetran grid resolution up to 1 km at which the basin hydrology and final sediment yield is modelled to a subgrid resolution typically around 10 100 m at which landslide occurrence and erosion is modelled the subgrid discretization landslide susceptibility and potential landslide impact are determined in advance using a geographic information system gis with shetran then providing information on temporal variation in the factors controlling landsliding the ability to simulate landslide sediment yield is demonstrated by a hypothetical application based on a catchment in scotland

assessment of shallow landsliding by using a physically based model of hillslope stability a model for the simulation of shallow landsliding triggered by heavy rainstorms is analysed and discussed the model is applied in two mountainous catchments in the dolomites eastern italian alps the cordon catchment 5 km2 and the vauz catchment 1 9 km2 where field surveys provided a description of hydraulic and geotechnical properties of soils and an inventory of landslide scars is available the stability mapping procedure which is similar to that proposed by montgomery and dietrich 1994 water resources research30 1153 combines steady state hydrologic concepts with the infinite slope stability model the model provides an estimate of the spatial distribution of the critical rainfall which is the minimum steady state rainfall predicted to cause instability the comparison of the landslides observed in the study basins with model predictions shows that the distribution of critical rainfall obtained from the model provides a surrogate for failure initiation probability as a function of topographic location copyright 2002 john wiley sons ltd language en

moisture structures of laterally expanding fingering flows in sandy soils water sometimes infiltrates into a sandy soil along preferential flow paths called fingers rather than homogeneously in order to understand the physical fundamentals of fingering flow we carried out two dimensional infiltration tests under continuous rainfall each finger was composed of two moisture structure zones a finger core and a finger swelling zone surrounding the finger core each finger can be classified as a low swell finger lsf or a high swell finger hsf based on the swelling velocity in lsf water moves laterally across a constant potential boundary where sorptivity is a dominant factor in making the finger swell in hsf on the other hand water moves laterally through a constant flux boundary where pressure gradient is a driving force in the latter accordingly the corresponding water flux can be estimated by the hydraulic conductivity multiplied by the water pressure gradient based on these observations we propose a growth model for a finger moving downward along with subsequent lateral expansion which makes it possible to estimate the area of soil wetted by fingers the estimated area is in a fairly good agreement with that observed

modeling fingered flow of water in soils owing to wetting front instability a review abstract fingered flow in the unsaturated zone caused by wetting front instability enhances solute leaching to the groundwater this paper reviews recent progress in fingered flow research focusing on theoretical results and model development a variety of stability criteria have been derived to predict wetting front instability mainly through linear and sometimes non linear stability analysis but also by theoretically analyzing infiltration into dry soils and by stochastic methods that take into account random variations of the soil properties fluid pressure and front location these stability criteria are discussed and compared eight expressions for finger size are presented they fall into three categories based on the dependence on the ratio of the infiltration rate to the soil hydraulic conductivity in the finger next the modeling of finger growth is discussed because of its relevance to solute transport recent advances in the measurement and modeling of finger behavior in moist soils are thoroughly reviewed various models ranging from easily applied closed form equations for risk assessment to sophisticated transient numerical codes have been developed over the past 15 years these are discussed and selected results are shown finally some remaining gaps in our understanding are given among these are the role of the initial water content the nature of the flow in the distribution zone above the fingers the effect of soil heterogeneity on wetting front instability and the combined effect of soil heterogeneity and wetting front instability on field scale solute transport

imprints of archean to neoproterozoic crustal processes in the madurai block southern india madurai block the largest crustal block in the southern granulite terrane sgt of peninsular india preserves the imprints of multistage tectonic evolution here we present u pb and hf isotope data on zircons from a charnockite granite suite in the north western part of this block the oscillatory zoning and the lree to hree enriched patterns of the zircons with positive ce and negative eu anomalies suggest that the zircon cores are of magmatic origin with ages in the range of 2634 2435 ma implying neoarchean paleoproterozoic magmatism followed by subsequent metamorphism and protocontinent formation in the north western part of the madurai block a regional 550 500 ma metamorphic overprint is also preserved in the zircons coinciding with the final amalgamation of the gondwana supercontinent the hf isotopic data suggest that the granite and charnockite were derived from isotopically heterogeneous juvenile crustal domains and the charnockites show a significant contribution of mantle derived components therefore the hf isotopic data reflect mixing of crustal and mantle derived sources for the generation of neoarchean crust in the north western madurai block possibly in a suprasubduction zone setting during continent building processes c 2014 elsevier ltd all rights reserved