new age constraints on the lan sang gneiss complex thailand and the timing of activity of the mae ping shear zone from in situ and depth profile zircon and monazite u th pb geochronology abstract the mae ping shear zone mpsz is one of four major strike slip systems in thailand and a key structural element in some models of the cenozoic tectonic evolution of southeast asia in northwestern thailand the mpsz exposes a 5 km wide core of intensely deformed high grade metamorphic and minor undeformed magmatic rocks the lan sang gneiss complex lsgc despite previous efforts to determine the chronology of the lsgc and ultimately the mpsz the evolution of this gneiss complex remains incompletely resolved here we present new zircon and monazite u th pb la mc icp ms ages and whole rock geochemical analyses from three peraluminous high k meta igneous granitic rocks augen gneiss sheared granodiorite undeformed subvolcanic dike of the lsgc our zircon u pb dating suggests that the granitic protolith of the augen gneiss intruded metasedimentary basement of sibumasu as early as 235 220 ma zircon rim and monazite u th pb ages from the same sample attest to periods of metamorphic recrystallization and overgrowth in the late triassic early jurassic early cretaceous and eocene the latter event had started by 45 ma and culminated in partial melting of the basement gneisses and the intrusion of granodiorite magma into the lsgc at 35 ma contemporaneous with ductile deformation along the mpsz a late undeformed subvolcanic dike that crosscuts the mylonitic fabric of the calc silicate and marble core of the mpsz dated in this study at 22 ma may indicate that ductile shearing had ceased by that time thus our study provides the first evidence for late eocene early miocene magmatism in the lsgc

monitoring soil water and displacement conditions leading to landslide occurrence in partially saturated clays abstract shallow landslides frequently occur during transient rainfall infiltration and under partially saturated conditions however a detailed analysis of what triggers them particularly in clayey soils is often hindered by the lack of field measurements it is uncommon in fact to capture their occurrence in an instrumented natural slope this paper presents results from an integrated field experiment monitoring the soil water and displacement conditions that lead to the occurrence of a shallow landslide in partially saturated clays the integration of a variety of experimental techniques allowed for the examination of interplay between soil hydrological and mechanical properties this research also evaluates a slope stability model based on the suction stress concept since the model was applied after the occurrence of the landslide the results are interpreted as a hind casting technique for model evaluation nevertheless the detailed field measurements acquired during the monitoring activity and the occurrence of a landslide during the experiment provided significant information on model parameters and data interpretation the station provides remote satellite monitoring of data on weather variables soil water content and soil suction a time domain reflectometry cable was installed vertically to detect potential soil failure the experimental area had a high probability of landslide occurrence indeed slope failure occurred during the observation period showing the effectiveness of the station in detecting the occurrence time and depth of landslides the landslide was triggered in consequence of changes in suction stress the failure plane occurred at a depth of 1 4 m corresponding to the interface between a superficial layer of higher permeability of 1 to 1 45 m thickness slipping over a compacted substrate having lower permeability the analysis allowed for testing of the validity of the model and the description of the triggering mechanisms of the observed shallow landslide in unsaturated conditions indicating that oscillations in soil matric suction were the dominant variables determining soil failure

temporal changes of groundwater pressure in a natural slope of nonfissured clay this paper presents results from a field investigation in which groundwater pressures were measured in a natural slope of soft clay over a 10 year period measurements of piezometric levels are reported together with calculated annual changes of safety factor of the slope using consolidation theory predictions were made of changes of piezometric levels for the condition of zero infiltration based on the postulate that these changes were the direct result of changes of hydraulic conditions at the ground surface the predictions were in agreement with the field measurements a method is suggested for estimating the most severe groundwater pressures that a clay slope can be expected to experience using this method estimates were made of the minimum expected value of safety factor of the slope at the test site keywords natural slope clay pore pressures field measurements stability long term

revisiting the tectonic evolution of the triassic palaeo tethys convergence zone in northern thailand inferred from detrital zircon u pb ages

complex conductivity imaging for the understanding of landslide architecture abstract geophysical methods are widely used for landslide investigation to delineate depth and geometry of the sliding plane in particular electrical resistivity tomography ert is often used because both porosity and water saturation control the electrical resistivity of the subsurface materials and are critical for slope stability moreover ert can be employed to monitor changes in pore fluid pressure which is an important factor triggering landslides however the interpretation of ert results in clay rich landslides can be challenging considering that high electrical conductivity values may not only be related to an increase in saturation but also to the surface conduction mechanism which becomes dominant in the presence of clays recently environmental investigations have demonstrated an improved subsurface characterization through induced polarization ip imaging an extension of the ert method which permits to gain information about electrical conductive and capacitive i e polarization effect properties of the subsurface as the polarization effect is mainly controlled by surface charge which is large in clays ip images are expected to improve the lithological interpretation and overcome the limitations of the ert method additionally measurements collected over a broad frequency bandwidth the so called spectral ip sip have been successfully used in laboratory experiments to quantify textural and hydrogeological parameters however the application of sip field measurements for the delineation of hydrogeological structures in landslides has not been addressed to date to fill this gap in this study we present sip imaging results for data collected at the la valette landslide south east french alps where an existing geotechnical model of the landslide is available for evaluation moreover our study provides a detailed revision on the collection and processing of sip datasets as well as a description of the diverse sources of error in ip surveys to stress the importance of data error quantification for a quantitative application of the sip method our results demonstrate that adequate data processing allows obtaining consistent results at different frequencies and independently of the measuring protocol furthermore the frequency dependence of the complex conductivity obtained in the field scale sip survey is consistent with earlier laboratory experiments in conclusion our study shows the potential of the sip method to improve our understanding of subsurface properties and an improved delineation of the contact between the mobilized material and the bedrock as well as variations in the clay content within the landslide and the bedrock

a microstructurally based effective stress for unsaturated soils current alternative choices of stress state variables in unsaturated soils are described and compared with a special focus on the use of an effective stress experimental data on stiffness and shear strength evolution with suction suggest that the proportion of suction contributing to the effective stress is often much smaller than predicted by the term suction times degree of saturation generally used in effective stress expressions of the bishop type it is suggested that effective stress in unsaturated soils should be related to soil microstructure an effective degree of saturation is defined as describing the volume of water partially filling the soil macroporosity this effective degree of saturation defines the proportion of the prevailing suction that actually contributes to the effective stress two alternative expressions piecewise linear and non linear are proposed for the effective degree of saturation they offer a similar performance available data on stiffness and shear strength varia

the leaky thermocline a model for the vertical structure of ocean gyres is presented that extends the ideal thermocline theories of rhines and young and luyten et al to include a cross layer volume flux associated with geostrophic eddy transfer a two and one half layer model is considered that assumes that the intensity of the eddy transfer depends on the local strength of the current the ideal thermocline models emerge in the limit where the parameter characterizing the cross layer volume flux is asymptotically small inclusion of the eddy induced volume flux resolves the nonuniqueness of the sverdrup dynamics in the unventilated pool attached to the western boundary layer in the ventilated region solutions of the model equations converge to their ideal counterparts the circulation is closed explicitly by developing a western boundary layer theory based entirely on the effects of the cross isopycnal volume flux due to eddies unlike most models of western intensification the leaky boundary layer here is active and its dynamics are essential for determining the structure of the interior field

postfailure mechanics of landslides laboratory investigation of flowslides in pyroclastic soils of all landslides subaerial flowslides are the most dangerous according to the literature flowslides in saturated granular deposits are caused by static liquefaction induced by loss of stability however the catastrophic flowslides that occurred on steep slopes in campania southern italy in 1998 1999 and 2005 were triggered by rainwater infiltration into shallow deposits of pyroclastic soils which were initially unsaturated starting from the experience collected during the investigations of some of these landslides the writers consider flowslide evolution as a result of a mechanical chain process characterized by saturation increase due to rainwater infiltration mechanical degradation volumetric collapse and static liquefaction culminating in complete fluidization of the soil in the paper this chain process is investigated through wetting tests both in suction controlled triaxial apparatuses and in a well equipped small scale slope model

a review of numerical ocean modeling 1983 1986 midlatitude mesoscale and gyre scale for the years 1983 to the present numerical modeling of midlatitude ocean circulation on the mesoscale and gyre scale is reviewed numerical results have shown great similarity to recent thermocline theories but also some important differences in particular ventilation of the pool zone caused by convective processes is substantial also solutions employing explicitly resolved eddies differ significantly from their equilibrium counterparts inverse methods have provided improved estimates of meridional heat transport and tropical upwelling of tracers the crucial influence of the western boundary on the circulation of the gyre interior is beginning to be understood research has focused on the conditions for radiation by jets the relationship between a jet s structure and its stability and the generation of deep mean flows by eddy activity near the surface constraints on the structure of isolated vortices imposed by instability mechanisms have been explored with new balanced models which provide an inexpensive but accurate alternative to primitive equation models for many oceanic processes transport of salinity by gulf stream rings has been found to be comparable to the effects of evaporation and precipitation in the slope water it has also been shown that radial circulation in warm core rings cannot be disregarded as a possible cause of ring spin down in anticipation of a dramatic increase in the oceanic observational data base from altimetry scatterometry tomography and in situ measurement new modeling techniques for data assimilation and prediction are beginning to be developed

triggering and predisposing factors for flow like landslides in pyroclastic soils the case study of the lattari mts southern italy abstract shallow flowslides debris flows and debris avalanches are rainfall induced landslides consisting in the shear failure of few metres of soils or in some cases even less than a metre which greatly increase downslope in volume and flow velocity the southern italian region of campania has been historically affected by such events involving pyroclastic soils mainly resting on steep carbonate slopes this paper deals with the analysis of factors influencing the occurrence of flow like landslides adopting the lattari mts in campania as a case study the results of two investigation campaigns carried out in the area allowed effective large scale geological and geotechnical characterization to be set up stratigraphic profiles mean physical properties and typical friction angles at the critical state for each soil layer were investigated the effect of suction on peak and critical shear strength whose drop is responsible for soil failure was analysed using detailed information on both the stratigraphic and geotechnical features of the soils involved in past flow like landslides typical triggering models were selected representing locally recurrent geomorphologic conditions at the basin scale the identified models were adopted for slope stability analyses carried out on four cross sections of flowslides occurring prior to the event to back analyse the triggering conditions from the evidence on the triggering mechanisms and the results of analyses the infinite slope approach is not always suitable to model slope stability conditions properly because the onset of landslides is also affected by local topographic and stratigraphic factors

field hydrological monitoring of a sloping shallow pyroclastic deposit many mountainous areas in campania southern italy are characterized by steep slopes covered by unsaturated volcanic deposits shallow landslides are frequently triggered by intense and persistent

zircon u pb geochronology and elemental and sr nd hf o isotopic geochemistry of post collisional rhyolite in the chiang khong area nw thailand and implications for the melting of juvenile crust volcanic rocks are widely exposed within the chiang khong lampang tak igneous zone in nw thailand a representative rhyolite sample from the chiang khong area yielded a zircon u pb age of 230 7 1 1 ma n 20 mswd 0 98 the chiang khong rhyolites are characterized by low tio2 0 29 0 62 wt and mgo 0 04 0 82 wt with a cnk values of 0 95 1 06 one outlier at 1 47 and can be classified as highly fractionated i type rhyolites they are enriched in liles and lrees and depleted in hfses two representative samples have 87sr 86sr i ratios of 0 70497 and 0 70527 and the end t values fall at 1 1 and 1 3 respectively ehf t and 18o in zircon are between 4 7 to 12 0 and 5 3 to 5 9 respectively our geochemical data suggest that the chiang khong rhyolites formed by partial melting of juvenile mafic lower crust in a post collisional setting deep crustal anatexis was probably induced by upwelling asthenospheric mantle shortly after slab detachment subsequent to closure of the paleo tethys

preface for the special issue geology geodynamics and mineral resources of se asia insights from geosea xv congress hanoi 2018 se asia is an assembly of gondwana derived crustal blocks and an important piece for the geodynamic understanding of the asian continent since the phanerozoic this area experienced several significant geodynamic events the separation of many continents and microcontinents from gondwana through rifting lead to the opening of oceanic domains the closure of these oceanic basins and the subsequent continental collision is attested by subduction related magmatism accretionary complexes high pressure and high temperature metamorphisms crustal melting and magmatism including volcanism and plutonism the mesozoic tectono magmatism the cenozoic intracontinental tectonics related to the india collision and the recent magmatism and tectonics are also significant events recognized in se asia these geodynamic events represent the general framework for the numerous ore deposits recognized in the area

the granites of the southeast asian tin belt four granite provinces have been delineated each with its own distinctive pattern of mineralization 1 the main range province endogenous greisen bordered vein swarms of cassiterite and wolframite 2 the eastern province magnetite cassiterite skarns base metal sulphides with antimony in thailand 3 the western peninsular thailand burma province endogenous greisen bordered vein swarms and pegmatites of cassiterite and wolframite 4 the north thailand migmatitic province endogenous vein and skarn replacement scheelite and fluorite deposits with some tin and local antimony in all provinces but particularly in the main range granitoids designated as two phase variants have been recognized where xenocrysts and xenoliths of coarse primary texture granite are enclosed in and corroded by an invasive equigranular quartzo feldspathic matrix these rocks form an essential part of the granite sequence in all provinces and have probably resulted from the infiltration and disruption of the host granite by late stage magmatic fluids whole rock geochemistry from peninsular malaysia shows that the granites from the main range and eastern provinces comprise two contrasted suites which correspond approximately to the i and s type categories advocated by chappell white 1974 in addition it is shown that individual plutons within batholiths in the two provinces have distinctive geochemical parameters variation diagrams of plutons having the intrusive sequence primary texture granite two phase granite microgranite show linear trends with increasing sio 2 na 2 o rb w sn and u and decreasing sr ba th and all other major elements

development of the khao khwang fold and thrust belt implications for the geodynamic setting of thailand and cambodia during the indosinian orogeny abstract the indosinian orogeny in thailand is often viewed as having developed between strongly linear terranes which today trend approximately n s the terranes were subsequently disrupted by later tectonics particularly nw se trending cenozoic strike slip faults the ene wsw to ne sw striking thrusts and folds in the khao khwang platform area of the saraburi group on the sw margin of the indochina terrane are not easily explained in the context of this traditional view reversal of the clockwise rotation shown to have affected the block north of the mae ping fault zone only enhances the e w orientation of structures in the fold and thrust belt and moves the belt further east towards cambodia one solution for the trend that fits better with regional understanding from hydrocarbon exploration of the khorat plateau is that the indochina terrane was actually a series of continental blocks separated by permian rifting during the early triassic the early stages of collision south china cathaysian terrane collision with vietnam indochina resulted in the amalgamation of disparate blocks that now form the indochina terrane by closure along the rifts at the same time or following on from the collision there was closure of the back arc area between indochina and the sukhothai zone the rift basins were thrusted and inverted during the early stages of the indosinian orogeny and only underwent minor reactivated when later sibumasu collided with sukhothai zone indochina terrane margin during the late triassic the scenario described above requires the presence of a minor e w trending suture in nw cambodia evidence for this suture is suggested by the presence of permo triassic calc alkaline volcanism

stability analyses of rainfall induced landslides the slope stability issues concerning rainfall induced slope failures are investigated and presented specifically the effect of both negative and positive pore water pressures on the stability of initially unsaturated slopes are carefully explained and coupled with infinite slope analysis methods in order to present a predictive formulation of slope failures that occur as a result of rainfall events the formulation serves as a baseline analysis method for evaluating potentially unstable soil slopes that are subject to surface infiltration and explains the various triggering mechanisms that may occur based on individual combinations of the slope geometry soil strength and infiltration parameters a procedural method is outlined for utilizing the analytical formulation to predict the change in the factor of safety for a slope subject to infiltration and a detailed analysis of a case study is presented to verify the method quantitative statements are made concerning the time and depth of failure in relationship to the soil slope and rainfall parameters

on the time averaged flow of quasi geostrophic wind driven gyres the time averaged flow of a three layer eddy resolving quasi geostrophic ocean model is considered in the light of two analytical models of wind driven gyres in which the vertical structure of the gyre is set by assuming that potential vorticity is uniform beneath layers exposed to forcing the first due to young and rhines 1982 supposes that the depth integrated meridional transport is set by the imposed wind stress curl in contrast in the baroclinic fofonoff gyres of marshall and nurser 1986 1988 inertial aspects of the flow are emphasized without imposing a sverdrup constraint the mean fields from the model are seen to lie between the two extremes represented by these analytical solutions in the interior of the gyre away from inertial boundary currents and jets the sverdrup constraint is obeyed and the mean flows resemble the young and rhines solution however the essential character of the overspun recirculation including the weakly depth dependent nature of the currents in its return flow seem to be well captured in the inertial limit considered by marshall and nurser

four dimensional imaging of moisture dynamics during landslide reactivation landslides pose significant risks to communities and infrastructure and mitigating these risks relies on understanding landslide causes and triggering processes it has been shown that geophysical surveys can significantly contribute to the characterization of unstable slopes however hydrological processes can be temporally and spatially heterogeneous requiring their related properties to be monitored over time geoelectrical monitoring can provide temporal and volumetric distributions of electrical resistivity which are directly related to moisture content to date studies demonstrating this capability have been restricted to 2d sections which are insufficient to capture the full degree of spatial heterogeneity this study is the first to employ 4d i e 3d time lapse resistivity imaging on an active landslide providing long term data three years highlighting the evolution of moisture content prior to landslide reactivation and showing its decline post reactivation crucially the time lapse inversion methodology employed here incorporates movements of the electrodes on the unstable surface although seasonal characteristics dominate the shallow moisture dynamics during the first two years with surficial drying in summer and wetting in winter in the months preceding reactivation moisture content increased by more than 45 throughout the slope this is in agreement with independent data showing a significant rise in piezometric heads and shallow soil moisture contents as a result of prolonged and intense rainfall based on these results remediation measures could be designed and early warning systems implemented thus resistivity monitoring that can allow for moving electrodes provides a new means for the effective mitigation of landslide risk

late triassic post collisional granites related to paleotethyan evolution in se thailand geochronological and geochemical constraints abstract a set of new u pb geochronological elemental and sr nd hf isotopic data is presented to constrain the formation age and petrogenesis of granites in se thailand which are significant for understanding eastern paleotethyan tectonic evolution and regional correlation in se asia six granite samples from the chonburi rayong bang lamung and chanthaburi plutons yielded similar crystallization ages of 222 218 ma these granites can be geochemically classified into s type group 1 and i type group 2 granites both groups have similar chondrite normalized ree and primitive mantle normalized multi element patterns but distinctly different sr nd hf isotopic compositions group 1 is characterized by more enriched initial 87sr 86sr i ratios 0 7101 0 7272 and lower end t values 12 0 to 13 2 compared with those of group 2 with 87sr 86sr i of 0 7027 0 7053 and end t of 0 6 to 1 2 consistently zircons from group 1 yield negative ehf t values of 7 3 to 27 4 and mesoproterozoic or older hf model ages tdm 1 53 2 63 ga distinct from those of group 2 with positive ehf t values 5 0 11 3 and younger tdm 0 42 0 67 ga group 1 granites mainly originated from ancient greywackes but group 2 from juvenile mafic crust with the input of meta sedimentary component these data along with available observations synthetically indicate that these granites formed in the post collisional gravitational collapse setting of the thickened crust in response to the assemblage of the indochina with sibumasu blocks they linked northerly and easterly to the late triassic granitoids in nw thailand and east malay peninsula related to the paleotethyan tectonic regime respectively

some aspects of the initiation of debris avalanches in the campania region the role of morphological slope discontinuities and the development of failure abstract in may 1998 a prolonged period of rainfall caused disastrous landslides in the sarno quindici area campania southern italy the landslides initiated as small debris slides and developed into debris avalanches and debris flows involving the shallow pyroclastic deposits that lie on the steep vegetated slopes of this area in view of the potential for such events to occur again in this area an understanding of the initial failure mechanism is crucial if assessments are to be made of the hazard levels in this paper the results of detailed surveys of the morphological characteristics of the source areas are presented statistical analyses and parametrical relationships have been performed on key parameters demonstrating that the initial failures were associated with the presence of morphological discontinuities such as limestone scarps and road cuts notably the presence of man made cuts appears to have been responsible for about the 60 of the initial debris slides morphometric analysis has shown that the debris avalanches are characterised by a typical triangular shape statistical analyses have been used to try to relate the apex angles to relevant geomorphological parameters allowing for differences in local morphology the findings show some significant correlation

probing into thailand s basement new insights from u pb geochronology sr sm nd pb and lu hf isotopic systems from granitoids

zircon u pb dating and the petrological and geochemical constraints on lincang granite in western yunnan china implications for the closure of the paleo tethys ocean abstract lincang granite is a batholith located in the sanjiang region and is an important research subject for understanding subduction and collision during the paleo tethyan period it is widely exposed in the lincang terrane and extends south into burma based on various petrological and geochemical investigations performed from south to north across the lincang granite a new set of data which includes zircon chronological and hf isotopic data is presented to discuss the origin of the lincang granite and its tectonic significance the lincang granite is a peraluminous high k calc alkaline body with sub parallel ree patterns and a strong negative eu anomaly this anomaly is characteristic of a post collision peraluminous s type granitic batholith the 200 230 ma formation age of the lincang granite was determined using la icp ms zircon u pb dating thus it has been confirmed that the granite formed during the late triassic period and the formation process lasted for approximately 30 ma geochemical and isotopic compositions indicate that the primary magma of lincang granite most likely originated from a crustal source and possibly underwent an assimilation fractionation crystallization afc process during its emplacement the lincang granite formed during the continental collision between the baoshan gengma terrane and the lanping simao terrane after the northeast subduction of the paleo tethyan oceanic plate therefore the late triassic lincang granite is important evidence for the closure of the paleo tethyan ocean

can the western boundary layer affect the potential vorticity distribution in the sverdrup interior of a wind gyre abstract the question posed in the title of this paper is answered in the affirmative by investigating a two layer quasi geostrophic model of the wind driven circulation the two layers model the thermocline rather than the whole depth of the ocean the wind stress is balanced by interfacial and bottom drag this is perhaps the simplest baroclinic extension of stommel s 1948 barotropic circulation model it differs from an earlier model of welander 1966 in that the vortex stretching nonlinearity is of primary importance in this model the dynamics of the frictional western boundary layer determine the vertical structure of the wind driven flow in the sverdrup interior thus in a sense the boundary layer is active and cannot be appended to an arbitrary interior flow rather it partially determines the interior circulation by setting the functional relationship between the streamfunction and the potential vorticity in the lower layer in previous studies rhines and young 1982b this functional rel

did oligocene crustal thickening precede basin development in northern thailand a geochronological reassessment of doi inthanon and doi suthep the doi inthanon and doi suthep metamorphic core complexes in northern thailand are comprised of amphibolite grade migmatitic gneisses mantled by lower grade mylonites and metasedimentary sequences thought to represent cordilleran style core complexes exhumed through the mobilization of a low angle detachment fault previous studies have interpreted two metamorphic events late triassic and late cretaceous followed by ductile extension between the late eocene and late oligocene a model which infers movement on the detachment at ca 40 ma and which culminates in a rapid unroofing of the complexes in the early miocene the chiang mai basin the largest such cenozoic basin in the region lies immediately to the east its development is related to the extension observed at doi inthanon and doi suthep however it is not definitively dated and models for its development have difficulty reconciling miocene cooling ages with eocene detachment movement here we present new in situ la icp ms and sims u pb age data of zircon and monazite grains from gneiss and leucogranite samples taken from doi inthanon and doi suthep our new zircon data exhibit an older age range of 221 210 ma with younger ages of ca 72 ma and 32 26 ma our monazite data imply an older age cluster at 83 67 ma and a younger age cluster of 34 24 ma while our data support the view of indosinian basement being reworked in the cretaceous they also indicate a late eocene oligocene tectonothermal event resulting in prograde metamorphism and anatexis we suggest that this later event is related to localized transpressional thickening associated with sinistral movement on the mae ping fault coupled with thickening at the restraining bend of the mae yuan fault to the immediate west of doi inthanon further this upper oligocene age limit from our zircon and monazite data would imply a younger miocene constraint on movement of the detachment which when combined with the previously recorded miocene cooling ages has implications for a model for the onset of extension and subsequent development of the chiang mai basin in the early mid miocene

steep slope monitoring in unsaturated pyroclastic soils based on monitoring results the paper describes the hydrological response of a steep hillslope covered by unsaturated pyroclastic soils the instrumented site is located just beside an area which experienced a catastrophic flowslide two years prior to the survey monitoring involved rainfall and matric suction measured at different locations and depths investigations focused on the hydrological response of the slope so as to model the effects of rainfall and then predict the onset of slope failure triggered by critical rainfall

p t t constraints on the development of the doi inthanon metamorphic core complex domain and implications for the evolution of the western gneiss belt northern thailand abstract the western gneiss belt in northern thailand is exposed within two overlapping cenozoic structural domains the extensional doi inthanon metamorphic core complex domain located west of the chiang mai basin and the mae ping strike slip fault domain located west of the tak batholith new p t estimates and u pb and 40ar 39ar age determinations from the doi inthanon domain show that the gneiss there records a complex multi stage history that can be represented by a clockwise p t t path u pb zircon and titanite dating of mylonitic calc silicate gneiss from the mae wang area of the complex indicates that the paragneissic sequence experienced high grade medium pressure metamorphism m1 in the late triassic early jurassic ca 210 ma in good agreement with previously determined zircon ages from the underlying core orthogneiss exposed on doi inthanon late cretaceous monazite ages of 84 and 72 ma reported previously from the core orthogneiss are attributed to a thermal overprint m2 to upper amphibolite facies in the sillimanite field u pb zircon and monazite dating of granitic mylonite from the doi suthep area of the complex provides an upper age limit of 40 ma late eocene for the early stage s of development of the actual core complex by initially ductile low angle extensional shearing under lower amphibolite facies conditions m3 accompanied by near isothermal diapiric rise and decompression melting 40ar 39ar laserprobe dating of muscovite from both doi suthep and doi inthanon provided miocene ages of ca 26 15 ma representing cooling through the ca 350 c isotherm and marking late stage development of the core complex by detachment faulting of the cover rocks and isostatic uplift of the sheared core zone and mantling gneisses in the footwall similarities in the thermochronology of high grade gneisses exposed in the core complex and shear zone domains in the western gneiss belt of northern thailand and also in northern vietnam laos yunnan and central myanmar suggest a complex regional response to indentation of southeast asia by india

dating multiple generation of zircons from granites and gneiss from thailand implication for the crustal evolution of the sibumasu terrane abstract the widespread granitic rocks of the sibumasu terrane were emplaced during the collision of the sibumasu and indochina in the triassic previous studies have suggested that each granite had a simple single step magmatic evolution in situ la mc icp ms u pb zircon dating of granites and gneiss from thailand revealed the evolution of these rocks inherited zircon core ages 515 130 ma from a granite of the chonburi pluton in the central granitoid belt are coeval with an orthogneiss protolith age 513 6 9 2 ma from hua hin area similar cambrian ages were also reported from the khao tao area in southern thailand moreover there are a series of inherited zircon core ages from neo proterozoic 1017 43 and 984 56 ma ordovician 449 26 ma devonian 385 15 ma carboniferous 316 12 ma to permian 276 31 and 266 12 ma taken together these neo proterozoic to permian protolith ages are interpreted to represent the basement of the sibumasu terrane in thailand two magmatic zircon growth events can be distinguished at approximately a 241 8 8 2 to 235 12 ma and b 230 6 3 4 to 213 4 3 0 ma we concluded that the sibumasu and indochina collision during the triassic caused a two step magmatic evolution of the granites of the sibumasu terrane the first magmatic crystallization during the middle triassic corresponded to the sibumasu and indochina collision and the second magmatic crystallization during the late triassic was related to the late collisional stage

rainfall patterns triggering shallow flowslides in pyroclastic soils in the context of landslide prone pyroclastic soils this paper investigates the physical significance of antecedent rainfalls in relation to the major rainfall event and the influence exerted by evaporation the work is based on results from tests using a physical model developed to characterise the hydraulic response of a pyroclastic soil volume subjected to actual meteorological conditions rainfall evaporation water storage soil suction and soil volumetric water content were continuously monitored over a meteorological window exceeding two years interpretation of the experimental results provides three characteristic values of water storage which are used to explain the physical significance of antecedent and triggering precipitations and shed light on the aspects of major rainfall events triggering landslides

geophysical monitoring of moisture induced landslides a review author s whiteley js chambers je uhlemann s wilkinson pb kendall jm abstract 2018 the authors geophysical monitoring of landslides can provide insights into spatial and temporal variations of subsurface properties associated with slope failure recent improvements in equipment data analysis and field operations have led to a significant increase in the use of such techniques in monitoring geophysical methods complement intrusive approaches which sample only a very small proportion of the subsurface and walk over or remotely sensed data which principally provide information only at the ground surface in particular recent studies show that advances in geophysical instrumentation data processing modeling and interpretation in the context of landslide monitoring are significantly improving the characterization of hillslope hydrology and soil and rock hydrology and strength and their dynamics over time this review appraises the state of the art of geophysical monitoring as applied to moisture induced landslides here we focus on technical and practical uses of time lapse methods in geophysics applied to monitoring moisture induced landslide the case studies identified in this review show that several geophysical techniques are currently used in the monitoring of subsurface landslide processes these geophysical contributions to monitoring and predicting the evolution of landslide processes are currently underrealized hence the further integration of multiple parametric and geotechnically coupled geophysical monitoring systems has considerable potential the complementary nature of certain methods to map the distribution of subsurface moisture and elastic moduli will greatly increase the predictive and monitoring capacity of early warning systems in moisture induced landslide settings

petrochemistry u pb zircon age and palaeotectonic setting of the lampang volcanic belt northern thailand two ne trending belts of mainly subaerial dacitic to rhyolitic flows and tuffs occur in the area between the towns of lampang and denchai in northern thailand in the western belt doi ton the rocks have been pervasively altered to quartz keratophyre rocks in the eastern belt doi luang are generally less altered mobile chemical components such as na 2 o and k 2 o show wide variation particularly in samples from the doi ton belt however low zr tio 2 ratios and low nb and ta contents support an origin at a convergent plate margin a positive epsilon nd value of 4 9 for rhyolite from the doi luang belt supports derivation from a primitive crustal source a rhyolite sample from the doi luang belt yielded a u pb zircon age of 240 1 ma early mid triassic the doi ton and doi luang belts are part of the lampang volcanic belt which can be traced to the north into the lincang jinghong volcanic belt in southern china comparison with published petrological data from the lincang jinghong belt shows strong similarity including the widespread development of keratophyric mineralogy and chemistry the lampang lincang jinghong belt formed at an early mid triassic convergent plate margin and is similar in age and tectonic setting to the more mafic phetchabun volcanic belt on the east side of the nan river suture zone these data constrain the timing of final amalgamation between the indochina and shan thai terranes to mid triassic or younger

soil water balance in an unsaturated pyroclastic slope for evaluation of soil hydraulic behaviour and boundary conditions flowslides in granular soils pose a major threat to life and the environment their initiation in unsaturated soils is regulated by rainfall infiltration which reduces the matric suction and hence shear strength analysis of such phenomena is of strategic importance especially when it aims to mitigate landslide risk by means of early warning systems ewss in this framework physically based models need to reproduce the hydro mechanical behaviour of the slopes through numerical analyses whose main uncertainty concerns the hydraulic conditions at the boundaries of the studied domain and hydraulic conductivity functions of unsaturated soils hence consummate knowledge of both these factors is absolutely necessary for efficient predictions in this paper hydraulic boundary conditions and hydraulic conductivity functions are investigated at the scale of the slope through an application of soil water balance based on in situ monitoring at the test site of monteforte irpino southern italy meteorological data matric suction and soil water content measurements were collected over four years at the test site the soil water balance was analysed on a seasonal time scale with regard to the whole pyroclastic cover resting on the steep limestone substratum infiltration and runoff are estimated interaction between the soil cover and the substratum is investigated and the hydraulic conductivity functions operative at the site scale are defined

building physically based models for assessing rainfall induced shallow landslide hazard at the catchment scale the case study of the sorrento peninsula italy the assessment of rainfall induced shallow landslide hazards at the catchment scale poses a significant challenge traditional empirical approaches for landslide hazard assessment often assume that

a performance based method for the design of drainage trenches used to stabilize slopes abstract drainage trenches are widely used as a measure for slope stabilization their effect is generally quantified in terms of a safety factor against a possible collapse mechanism of the slope a more rational and economical design approach consists in admitting the occurrence in some time intervals of limit conditions in the slope and evaluating the performance of the slope in terms of accumulated permanent displacements of the unstable soil mass the resulting displacements should avoid the occurrence of significant damage and preserve the serviceability of existing structures in this context a new method is proposed in the present paper for the design of drainage trenches used to control the mobility of translational landslides periodically activated by rainfall this method is based on some analytical equations that relate rain to the groundwater regime as modified by the trenches and a simple sliding block model to evaluate the landslide displacements the proposed method also accounts for the delay of the hydraulic response at different depths the above mentioned equations are validated by several comparisons with numerical results obtained using a finite element code or published in the literature finally the method is applied to some case studies to show the effectiveness of the drainage trenches to control the landslide mobility owing to rainfall

two and three dimensional electrical resistivity imaging at a heterogeneous remediation site geometrically complex heterogeneities at a decommissioned sour gas plant could not be adequately characterized with drilling and 2d electrical resistivity surveys alone in addition 2d electrical resistivity imaging profiles produced misleading images as a result of out of plane resistivity anomalies and violation of the 2d assumption accurate amplitude and positioning of electrical conductivity anomalies associated with the subsurface geochemical distribution were required to effectively analyze remediation alternatives forward and inverse modeling and field examples demonstrated that 3d resistivity images were needed to properly reconstruct the amplitude and geometry of the complex resistivity anomalies problematic 3d artifacts in 2d images led to poor inversion fits and spurious conductivity values in the images at depths close to the horizontal offset of the off line anomaly three dimensional surveys were conducted with orthogonal sets of wenner and dipole dipole 2d resistivity survey lines the

the closure of palaeo tethys in eastern myanmar and northern thailand new insights from zircon u pb and hf isotope data abstract two of the major granite belts of southeast asia are the main range and eastern province together these are interpreted to represent the magmatic expression of the closure of palaeo tethys during late palaeozoic to early mesozoic times recent geochronological and geochemical work has better delineated these belts within peninsular malaysia thereby providing important constraints on the timing of palaeo tethys suturing however the northern extension of this palaeo tethyan suture is less well understood here we present new ion microprobe u pb zircon age data from northern thailand and eastern myanmar measured ages of 219 and 220 ma from the kyaing tong granite imply northern extension of the main range province into eastern myanmar the tachileik granite in far eastern myanmar yields an age of 266 ma consistent with published eastern province ages and this therefore constrains the northern extension of the palaeo tethys suture in eastern myanmar we further discuss how this suture may extend northwards into yunnan a late cretaceous age 70 ma measured in thailand represents later magmatic activity and is similar to published magmatic ages from central myanmar this younger magmatism is interpreted to be related to the subduction of neo tethys prior to india asia collision further we present new laser ablation zircon hf isotope data from eastern myanmar which suggest that palaeoproterozoic crust underlies both the main range and eastern province granites our ehf model age of ca 1750 ma from sibumasu the basement underlying eastern myanmar lies within the range of other model ages reported thus far for the baoshan block north in yunnan interpreted by some to be the northern extension of sibumasu

coupling of hydraulic and mechanical behaviour in unsaturated compacted clay an experimental study was carried out to investigate the shear strength of a compacted non active clay speswhite kaolin a total of 33 statically compacted specimens were prepared at vertical stresses of 300 600 and 1200 kpa and water contents ranging from 0 24 to 0 34 this made it possible to explore a broad range of initial compaction induced conditions and hence to examine whether differences in water retention characteristics and shear strength are due to differences in initial compaction induced state or are to be attributed to fundamentally different microfabrics a shearbox was modified to allow the direct measurement of negative pore water pressure using trento high suction tensiometers tests were carried out at constant water content by monitoring suction changes in these tests it was possible to investigate the transition from unsaturated to saturated states in the first stage of the test the specimen was compressed at constant water content the specimen was therefore wetted in the s

electrical resistivity tomography technique for landslide investigation a review abstract in the context of in situ geophysical methods the electrical resistivity tomography ert is widely used for the near surface exploration of landslide areas characterized by a complex geological setting over the last decade the technological improvements in field data acquisition systems and the development of novel algorithms for tomographic inversion have made this technique more suitable for studying landslide areas with a particular attention to the rotational translational and earth flow slides this paper aims to present a review of the main results obtained by applying ert for the investigation of a wide spectrum of landslide phenomena which affected various geological formations and occurred in different geographic areas in particular significant and representative results obtained by applying 2d and 3d ert are analyzed highlighting the advantages and drawbacks of this geophysical technique finally recent applications of the time lapse ert tl ert for landslide investigation and the future scientific challenges to be faced are presented and discussed

assessment of active landslides using field electrical measurements abstract landslide characterization and hazard assessments require multidisciplinary approaches that connect geologic processes with geotechnical parameters preexisting landslide activity geology and geomorphology soil strength and hydrologic conditions are complex factors that affect landslide behavior often the connections among these factors are not made for hazard assessments forecasting or slope stability modeling therefore geophysical and geotechnical techniques for landslide investigations are typically assessed independently this study aims to bring together different techniques to develop a methodology that connects electrical measurements and shear strength a framework has been developed for using electrical resistivity measurements that will support and facilitate the prediction of shear strength within a slope in situ volumetric water content soil water potential suction and electrical conductivity were measured from two shallow colluvial landslides in kentucky repeated surface electrical resistivity survey measurements were used to characterize the failure zone and lithology and to compare with the in situ hydrologic measurements the data show that subsurface moisture conditions over time can be reflected in the inversions of repeated er surveys thus allowing electrical measurements and geotechnical parameters to be correlated this study demonstrates that electrical resistivity can be used as a tool for landslide monitoring and to assess shear strength these parameters are pertinent to investigating the stability of landslides that are often triggered or reactivated by rainfall

timing of metamorphism of the lansang gneiss and implications for left lateral motion along the mae ping wang chao strike slip fault thailand the mae ping fault mpf western thailand exhibits dominantly left lateral strike slip motion and stretches for 600 km reportedly branching off the right lateral sagaing fault in myanmar and extending southeast towards cambodia previous studies have suggested that the fault assisted the large scale extrusion of sundaland that occurred during the late eocene early oligocene with a geological offset of 120 150 km estimated from displaced high grade gneisses and granites of the chiang mai lincang belt exposures of high grade orthogneiss in the lansang national park part of this belt locally contain strong mylonitic textures and are bounded by strike slip ductile shear zones and brittle faults geochronological analysis of monazite from a sample of sheared biotite k feldspar orthogneiss suggests two episodes of crystallization with core regions documenting th pb ages between c 123 and c 114 ma and rim regions documenting a significantly younger age range between c 45 37 ma these data are interpreted to represent possible magmatic protolith emplacement for the lansang orthogneiss during the early cretaceous with a later episode of metamorphism occurring during the eocene textural relationships provided by in situ analysis suggest that ductile shearing along the mpf occurred during the latter stages of or after this metamorphic event in addition monazite analyzed from an undeformed garnet two mica granite dyke intruding metamorphic units at bhumipol lake outside of the mae ping shear zone produced a th pb age of 66 2 1 6 ma this age is interpreted to date the timing of dyke emplacement implying that the mpf cuts through earlier formed magmatic and high grade metamorphic rocks these new data when combined with regional mapping and earlier geochronological work show that neither metamorphism nor regional cooling was directly related to strike slip motion

first evidence of the cambrian basement in upper peninsula of thailand and its implication for crustal and tectonic evolution of the sibumasu terrane abstract although the sibumasu terrane in asia was previously considered to be composed of phanerozoic rocks with cambrian crystalline basement no reliable or direct radiometric dating evidences of such crystalline basement was ever reported our new in situ zircon u pb dating of the khao tao orthogneiss yields a concordant age of 501 5 7 5 ma 2 which provides the first robust evidence for the cambrian crust in upper peninsula of thailand the zircon ehf t values range from 3 7 to 6 1 with model ages tcdm of 1244 1827 ma suggests a mixed crust mantle source the chemical similarity and spatial continuity of the khao tao orthogneiss with other pre neotethys marginal eurasian and sibumasu granitoids indicate the linear paleogeographic association under a similar magmatic arc related regime along the gondwana india australia margin as part of the pan african orogeny system

structure and kinematics of a landslide in a complex clayey formation of the italian southern apennines abstract this paper describes the geometrical structure and the main kinematic features of an ancient and active landslide which develops in structurally complex formations of the southern apennines italy a scaly clayey formation in the medium and lower part of the slope and a stratified marly calcareous rock formation in the upper part the landslide 3d geometry was reconstructed by using topographic data stratigraphies from continuous coring boreholes and inclinometer data the analysis of the kinematic features was based on the measurement of deep and superficial displacements laboratory tests were carried out to evaluate shear strength parameters it was found that in each investigated transversal section of the landslide channel the displacements can be considered uniform and that the decrease of the displacement rates from upslope to downslope mostly depends on the increase in the areas of transversal sections the soil discharge variations being slight stability analyses confirmed that shear strength close to the residual value is available on the slip surface the large difference between residual strength and peak strength of the landslide material is consistent with the displacement uniformity

u pb zircon geochronology of early permian to late triassic rocks from singapore and johor a plate tectonic reinterpretation article i nfo the results of u pb zircon geochronology of permian to middle triassic granitoids from singapore and neighbouring johor are presented rhyolite from pulau sibu is 276 5 ma gabbros from singapore give ages of 260 2 to 249 2 ma granites from singapore give ages from 249 2 to 230 6 ma and rhyolite from telkuma gives an age of 238 2 ma u pb detrital zircon age spectra from a late triassic conglomerate from singapore show carboniferous mid dle triassic and late triassic spikes at 350 245 and 217 ma respectively these new data when combined with published u pb zircon ages allow a revision of the plate tectonic evolution of the malaysian peninsula region a tin bearing magmatic arc evolved in the eastern malaysian peninsula part of indochina from the early permian to the middle triassic when the palaeo tethys ocean was subducted and sibumasu continental lithosphere was rifted from pangea this opened up the neo tethys ocean that the granitoid ages show a progressive decrease in age from pulau sibu 276 5 ma to singapore 230 6 ma suggests that during this andean type orogenic phase the subduction zone rolled back and steepened causing the locus of mainly i type magmatism to migrate from east to west in present day coordinates across the eastern and central belts and stretch the lithosphere as it did so in the late triassic sibumasu collided with indochina causing the western belt sibumasu to over thrust the central belt indochina along the bentong raub suture the lower half of the thickened crust formally the tin bearing indochina plate was partially melted and pre dominantly s type tin bearing granites were intruded into the upper crust formally sibumasu this late triassic collisional phase is the indosinian orogeny in peninsular malaysia

the role of strike slip faults in the displacement of the palaeotethys suture zone in southeast thailand abstract six n s tectono stratigraphic belts can be recognized in southeast thailand each with a distinct stratigraphy and igneous history the westernmost belt i is thought to be part of the sibumasu block and the easternmost v to include part of the indochina block between those belt iii comprises acid volcanic rocks volcaniclastics and carboniferous to triassic sedimentary rocks with distinctive faunas interpreted to be a volcanic arc belt iv comprises triassic rocks of back arc basin origin belt v is interpreted as a permian accretionary complex on the western flank of indochina and vi is an unconformable cover of jurassic cretaceous red beds correlating with the khorat group a history of the triassic indosinian orogeny is proposed leading to the cratonization of southeast thailand by the end triassic the apparent absence in southeast thailand of rocks from the devonian triassic palaeotethys ocean the inthanon zone of northern thailand is suggested to have resulted from a phase of post indosinian oblique to longitudinal sinistral strike slip faulting that phase is thought to have included displacement on the mae yuam fault which bounds the inthanon zone in northern thailand then followed a phase of transverse sinistral strike slip faulting which offset the tectono stratigraphic belts and faults of the earlier phase

a model to simulate recharge processes of karst massifs the recharge processes have been evaluated for two karst massifs of southern italy the mt terminio and mt cervialto characterized by wide endorheic areas the annual mean recharge has been estimated by geographic information system gis tools from regression of annual mean values of different ground elevated rain gauges and thermometers the recharge has been distinguished for endorheic areas and the other areas of spring catchment and the ratio between the output spring and input rainfall has been also estimated recharge coefficient the annual recharge has been used to calibrate a daily scale model which allows to estimate the amount of effective rainfall which is retained as soil moisture the amount reaching the water table recharge s s and the amount of rainfall which develops the runoff and leaves the catchment all these amounts vary through the hydrological year in function of soil moisture deficit and daily rainfall intensity the model allows estimating the recharge conditions through the hydrological year and it is a useful tool for water management copyright 2014 john wiley sons ltd

debris slides rapid earth flows in the carbonate massifs of the campania region southern italy morphological and morphometric data for evaluating triggering susceptibility abstract this paper examines the morphological and morphometric properties of debris slides rapid earth flows which have occurred in pyroclastic deposits of the campania region over the last few centuries the slopes bordering the main carbonate massif of western campania are covered by several metres of pyroclastic deposits from the somma vesuvio volcano that due to the steepness of the slopes are easily eroded by surface waters and periodic debris slides rapid earth flows these flows are sudden and unpredictable and have caused both damage to the environment and loss of life over the last few decades after consulting scientific papers and historical documents the areas most recently affected by debris slides rapid earth flows were analysed through aerial photographs and a geological survey an inventory of 172 landslides was produced and landslides were mapped at a scale of 1 2000 for further geomorphological and morphometric analysis morphological analysis was primarily concerned with predisposing factors it confirmed that 86 of the slope failurecrowns developed in response to man made cuts and tracks 44 or due to the presence of cliffs 42 two different kinds of slopes are affected by debris slides rapid earth flows slopes lacking drainage basins and slopes cut by one or several drainage basins typical triangular shaped earth flows with a landslide mass located at the foot of the slope unchannelled debris slides rapid earth flows were found along the former slopes in contrast channelled debris slides rapid earth flows formed along the latter slopes these originated in the drainage divide area developed along the main water segment and invaded the alluvial plain far from the foot of the slope an intermediate group of flows started as triangular shaped and then became channelled morphometric analysis also investigated the parameters most commonly found in the literature slope angle of the crown and sliding zone crown altitude areal extent of the landslide together with other parameters apical angle of the crown zone and landslide body slope relief energy and potential zone of triggering this analysis identified critical values for the steepness of crown zones and for the steepness of the sliding zone critical values of the apical angle of the crown zone for mixed and unchannelled landslides were also established correlations among some of the investigated parameters were investigated in particular the relationships between slope relief energy and areal extent of landslides or the height of the landslide crown zone all the factors and parameters analysed in this paper can be used to identify areas which need to be stabilized or monitored and could be important for planning defensive measures of debris slides rapid earth flows

u pb zircon and chime monazite dating of granitoids and high grade metamorphic rocks from the eastern and peninsular thailand a new report of early paleozoic granite abstract in order to understand the age and tectonic framework of eastern to peninsular thailand from the viewpoint of basement metamorphic and plutonic geology the la icp ms u pb zircon dating and the chemical th u total pb isochron method chime monazite dating were performed in the khao chao hub kapong to pran buri and khanom areas in eastern to peninsular thailand the la icp ms u pb zircon dating of the garnet hornblende gneiss from the khao chao area gave 229 3 ma representing the crystallization age of the gabbro and that of the garnet biotite gneisses gave 193 4 ma representing the timing of an upper amphibolite facies metamorphism the chime monazite dating of pelitic gneiss from the khao chao gneiss gave scattered result of 68 22 ma due to low pbo content and rejuvenation of older monazite grains during another metamorphism in the late cretaceous to tertiary time the u pb ages of zircon from the hua hin gneissic granite in the hub kapong to pran buri area scatter from 250 ma to 170 ma on the concordia granite crystallization was at 219 2 ma followed by the sillimanite grade regional metamorphism at 185 2 ma monazite in the pelitic gneiss from this area also preserves early to middle jurassic metamorphism and rejuvenation by later contact metamorphism by non foliated granite or by another fluid infiltration event in the late cretaceous to tertiary time the khao dat fa granite from the khanom area of peninsular thailand gave a u pb zircon age of 477 7 ma this is the second oldest granite pluton ever reported from thailand and is a clear evidence for the sibumasu block having a crystalline basement that was formed during the pan african orogeny the khao pret granite gives u pb zircon concordia age of 67 5 1 3 ma which represents the timing of zircon crystallization from the granitic melt and accompanied sillimanite grade contact metamorphism against surrounding metapelites and gneisses metamorphic rocks in the doi inthanon area also share the similar plutono metamorphic history with the khanom and the hub kapong to pran buri areas this suggests that these three areas belong to the sibumasu block and the sibumasu block records similar plutono metamorphic history from northern to peninsular thailand relative abundance of oceanic components in the khao chao gneiss their late triassic magmatic ages and the early jurassic metamorphic ages prefer the interpretation that the khao chao gneiss belongs to the sukhothai arc

tectonic setting of the permo triassic chiang khong volcanic rocks northern thailand based on petrochemical characteristics abstract the inferred permo triassic chiang khong volcanic belt is composed of felsic to mafic volcanic rocks and their pyroclastic equivalents almost all the least altered mafic volcanic rocks are lava flows a few might have occurred as dykes these mafic volcanic rocks are non foliated to weakly foliated and mostly have porphyritic textures the phenocrysts microphenocrysts in porphyritic samples are commonly plagioclase and may include clinopyroxene olivine fe ti oxide apatite and amphibole the matrix of lava flows ranges texturally from felty to trachytic but a few samples show felty to ophitic subophitic and glassy textures whereas that of possible dyke samples is holocrystalline the primary matrix constituents are largely plagioclase and variable proportions of clinopyroxene fe ti oxide amphibole olivine apatite quartz alkali feldspar and or glass all the studied samples have been subjected to greenschist facies regional metamorphism chemically the samples show narrow ranges of least mobile incompatible element ratios and range compositionally from dacite to basalt of tholeiitic series these samples are chemically analogous to those of the tertiary andesite from sardinian rift sardinia italy particularly in terms of least mobile incompatible element ratios accordingly the studied mafic volcanic rocks are interpreted to have formed in a continental volcanic arc however the problem related to the geometry of plate convergence giving rise to the continental volcanic arc still exists

triggering mechanism and reactivation probability of loess mudstone landslides induced by rainfall infiltration a case study in qinghai province northwestern china rainfall especially rainstorm is a major factor in inducing loess mudstone landslides and plays an essential role in landslide reactivation the aim of the paper is to study the triggering mechanism and reactivation probability of a loess mudstone landslide induced by rainfall infiltration in qinghai province northwestern china according to the numerical model of elastic plastic mechanics the triggering mechanism of loess mudstone landslides was revealed then the reactivation probability of the potential landslide was evaluated by the combination of the limit equilibrium and monte carlo methods for one thing the relationship between water content and shear strength of media was analyzed based on the mechanical test of materials for another the effects of rainfall conditions were analyzed on the distribution of water content in the aerated zone with the two dimensional coupling model of unsaturated saturated seepage the results show that the shear strength of media is very sensitive to water content because of water rock interaction including hydration and dissolution besides the water content significantly increases at the interface between the loess and mudstone after the rainstorm occurring owing to the permeability heterogeneous of media and topographic feature which leads to the strength deterioration although the whole landslide is stable in the rainstorm conditions its middle part can be reactivated along the original sliding zone with high probability by a geomechanical model of sliding tension therefore the landslide reactivation is controlled by the water sensitivity of media the permeability heterogeneous of media the topographic feature and the original sliding zone especially the original sliding zone this research provides a valuable reference for the occurrence and reactivation of similar landslides

geochronological elemental and sr nd hf o isotopic constraints on the petrogenesis of the triassic post collisional granitic rocks in nw thailand and its paleotethyan implications abstract new u pb geochronological petrologic elemental and sr nd hf o isotopic data for the granites from the inthanon and sukhothai zones in nw thailand in conjunction with correlations with sw china are presented to constrain the age and position of the paleotethys ocean in this region and the associated assembly of southeast asia the geochronological data show that the granitic rocks in the inthanon and sukhothai zones herein named group 1 and group 2 granites respectively yield similar crystallization ages of 230 200 ma group 1 samples are characterized by monzogranite and granite with i and s type geochemical affinity and group 2 samples by i type monzogranite and granodiorite they have generally similar chondrite normalized ree and pm normalized multi element patterns but distinct sr nd hf o isotopic compositions group 1 samples have slightly higher initial 87sr 86sr ratios 0 7111 0 7293 but lower end t values 11 1 to 14 1 than those of group 2 samples 87sr 86sr i 0 7073 0 7278 and end t 8 3 to 11 0 group 1 samples show the lower ehf t values 5 4 to 18 2 older tdm 1 62 2 40 ga and higher 18o values 7 95 to 9 94 than those of group 2 samples ehf t of 11 1 to 4 80 tdm of 0 96 1 95 ga and 18o of 4 95 to 7 98 for the triassic crystallization zircons these geochemical signatures are similar to the kwangsian and indosinian granites in the south china and indochina blocks but distinct from those of the gangdese i type granite and sibumasu paleozoic granite our data suggest that group 1 samples mainly originated from the early paleozoic supracrustal rocks containing metapelite and metavolcanic components which had previously experienced the surface weathering group 2 samples were derived from a hybridized source of an old metamorphic and a newly underplated mafic component synthesis of our data with available regional observations indicates that the inthanon zone represents the main suture zone of the eastern paleotethyan ocean in nw thailand and links with the changning menglian suture zone in sw yunnan sw china in nw thailand a switch from the eastward subduction of the paleotethyan oceanic plate to the collision of the sibumasu with indochina blocks occurred at 237 ma and syn and post collisional time being at 237 230 ma and 200 230 ma respectively the late triassic granites in the inthanon and sukhothai zones are representative of the post collisional magmatic products

hydrogeological behaviour of some fault zones in a carbonate aquifer of southern italy an experimentally based model complex flow circulation patterns are likely to be present in fault controlled groundwater flow systems such as carbonate aquifers nevertheless not much information is available for faults in carbonates and their hydrogeological behaviour is often neglected in conceptual and numerical models the understanding of this aspect of subsurface fluid flow has been improved in a carbonate aquifer where hydrogeological investigations at site scale demonstrated the existence of fault zones that act as barriers the hydraulic conductivity of the fault core is as low as that of siliciclastic rocks that represent the regional aquitard of the carbonate aquifer despite the lower permeability the fault zones allow a significant groundwater flowthrough and a good interdependence of piezometric heads upgradient and downgradient of the faults because of this discontinuous heterogeneity the aquifer looks like a basins in series system where seasonal springs can be detected along some fault zones as a function of groundwater level fluctuations

hydro geomorphological modelling of ash fall pyroclastic soils for debris flow initiation and groundwater recharge in campania southern italy abstract carbonate mountain ranges surrounding volcanic centers in the campania region of southern italy are covered by discontinuous ash fall pyroclastic deposits of variable thicknesses the cover thickness and stratigraphy are relevant to hydrological controls on both rainfall induced landslides and groundwater recharge to improve understanding of the hydrologic regimes within the pyroclastic soil mantle a hydrological monitoring station was installed upslope of a debris flow source area in the sarno mountains monitoring results demonstrate consistently unsaturated conditions strong seasonal and inter annual variations in pressure head and delayed and damped dynamics at different depths related to rainfall and evapotranspiration patterns frequencies of recorded pressure head time series were analyzed to quantify the seasonal hydrological regime of the cover as a whole as well as variations within individual soil horizons for the whole ash fall pyroclastic soil cover variable seasonal frequencies of pressure head were recognized exceeding landslide alert and groundwater recharge threshold values analysis of frequencies for individual soil horizons showed a strongly delayed timing determining in winter and summer an opposite hydrological behavior between the shallowest and deepest soil horizons a model that accounts for topographic variations in cover thickness and these hydrological regimes is proposed to quantify hydro geomorphological controls on debris flows triggering and groundwater recharge the model is based on the estimation of ash fall pyroclastic soil thickness along slopes by the total thickness fallen in a given area and an inverse relationship with slope angle allowing the assessment at the distributed scale over peri volcanic mountainous areas moreover it links the spatially variable thicknesses of ash fall pyroclastic soils to the amount of soil water storage allowing the assessment of frequency of hydrological conditions leading to debris flow initiation and groundwater recharge

proprietes caracteristiques des argiles de l est du canada the compilation of numerous geotechnical data has allowed the definition of the main physical mechanical and hydraulic properties of marine and lacustrine clays of eastern canada as well as the establishment of correlations between some of these properties the possible uses of these correlations are described this study shows that the clays of eastern canada exhibit a behaviour similar to that of other clays but that they are characterized by a higher degree of structuration keywords physical properties mechanical properties hydraulic properties clays canada correlations journal translation

age tectonic setting and regional implications of the chiang khong volcanic suite northern thailand the chiang khong volcanic suite forms the northeastern part of the tak chiang khong volcanic belt in the sukhothai terrane of northern thailand it consists mainly of subaerial andesitic to rhyolitic tuffaceous rocks a rhyolitic tuff yielded a middle triassic u pb zircon age of 232 9 0 4 ma the suite displays calc alkalic chemical trends and nb p and ti depletion characteristic of subduction related magmatism based on petrological similarities the suite is correlated with the c 240 ma lampang volcanic rocks located farther to the sw in the tak chiang khong belt and with volcanic rocks of similar age in the lincang jinghong belt in yunnan in the western part of the simao block these correlations support the placement of the palaeo tethyan suture to the west of the sukhothai terrane

a study of the correlation between electrical resistivity and matric suction for unsaturated ash fall pyroclastic soils in the campania region southern italy in the territory of the campania region southern italy critical rainfall events periodically trigger dangerous fast slope movements involving ashy and pyroclastic soils originated by the explosive phases of the mt somma vesuvius volcano and deposited along the surrounding mountain ranges in this paper an integration of engineering geological and geophysical measurements is presented to characterize unsaturated pyroclastic samples collected in a test area on the sarno mountains salerno and avellino provinces campania region the laboratory analyses were aimed at defining both soil water retention and electrical resistivity curves versus water content from the matching of the experimental data a direct relationship between electrical resistivity and matric suction is retrieved for the investigated soil horizons typical of an ash fall pyroclastic succession the obtained relation turns out to be helpful in characterizing soils up to close saturation which is a critical condition for the trigger of slope failure in such a regime the water content and the matric suction have small variations while electrical resistivity variations can be appreciated in a larger range of values for this reason besides suction measurements on very small soil volumes through classical tensiometers our analyses suggest the direct monitoring of in situ electrical resistivity values as an effective tool to recognise the hydrological state of larger and more representative soil volumes and to improve early warning of dangerous slope movements

anisotropy of a shear zone the behaviour of landslides in clay is essentially governed by a shear zone located at the base of the soil mass while some data regarding the shear zones of slides are available information is rather poor about the shear zones of mudslides the paper reports some results of investigations on the shear zone located at the base of a mudslide showing the strong hydraulic and mechanical anisotropy of the material

the early triassic indosinian orogeny in vietnam truong son belt and kontum massif implications for the geodynamic evolution of indochina new structural field data at various scale and 40ar 39ar geochronological results from the basement rocks in the truong son belt and kontum massif of vietnam confirm that ductile deformation and high temperature metamorphism were caused by the early triassic event of the indosinian orogeny in the range of 250 240 ma a compilation of isotopic data obtained in other countries along the sibumasu indochina boundary broadly indicates same interval of ages this tectonothermal event is interpreted as the result of a synchronous oblique collision of indochina with both sibumasu and south china inducing dextral and sinistral shearing along e w to nw se and n s fault zones respectively the collision along song ma follows the northwards subduction of indochina beneath south china and the subsequent development of the song da zone which in turn was affected by the late triassic indosinian phase of shortening within the indochina plate internal collisions occurred coevally in the early triassic as along the poko suture at the western border of the kontum massif

an integrated geological geotechnical and geophysical approach to identify predisposing factors for flowslide occurrence abstract this study combines geological geotechnical and geophysical analyses to construct a 3d model of the subsoil based on a significant amount of data collected at a test site in the lattari mountain range in southern italy several investigation techniques were applied to study the spatial variability of the local stratigraphic setting and relevant geophysical and geotechnical parameters at the slope scale by integrating field and laboratory measurements such as geological logs soil sampling 2d and 3d electrical resistivity tomography surveys time domain reflectometry profiles and characteristic curves of electrical resistivity vs saturation degree the continuous stratigraphy of the pyroclastic cover in question was reconstructed and 3d models of effective saturation degree in different pyroclastic horizons were retrieved as the proposed procedure is applied to study flowslide initiation the test site was implemented on a 32 slope affected by historical flowslides the following factors predisposing to flowslides were identified steep stratigraphic contact between shallower soils and bedrock impermeable layers that buffer the draining of the fractured limestone preferential rainwater infiltration paths and spatial distribution of water content in the soil

seasonal groundwater regime in an unsaturated pyroclastic slope rainwater infiltration is the mechanism that leads or predisposes unsaturated pyroclastic slopes to failure by reducing matric suction and hence reducing the shear strength therefore groundwater flow analysis is an important tool to investigate slope stability as well as predict conditions caused by heavy rainfall analysis and prediction quality can be greatly improved by in situ monitoring in this framework this paper describes the results of an ongoing experimental research project on mudflows based on monitoring of a test site in a typical geological environment in western campania the site was selected to carry out extensive laboratory and in situ experimentation consisting of field monitoring of climatic conditions matric suction and water content the suction data span about 4 years while water content data cover about 2 years considered together these data allow clear identification of seasonal fluctuations of the hydraulic properties in the subsoil while giving interesting information

tectonic framework and phanerozoic evolution of sundaland abstract sundaland comprises a heterogeneous collage of continental blocks derived from the india australian margin of eastern gondwana and assembled by the closure of multiple tethyan and back arc ocean basins now represented by suture zones the continental core of sundaland comprises a western sibumasu block and an eastern indochina east malaya block with an island arc terrane the sukhothai island arc system comprising the linchang sukhothai and chanthaburi blocks sandwiched between this island arc formed on the margin of indochina east malaya and then separated by back arc spreading in the permian the jinghong nan uttaradit and sra kaeo sutures represent this closed back arc basin the palaeo tethys is represented to the west by the changning menglian chiang mai inthanon and bentong raub suture zones the west sumatra block and possibly the west burma block rifted and separated from gondwana along with indochina and east malaya in the devonian and were accreted to the sundaland core in the triassic west burma is now considered to be probably cathaysian in nature and similar to west sumatra from which it was separated by opening of the andaman sea basin south west borneo and or east java west sulawesi are now tentatively identified as the missing argoland which must have separated from nw australia in the jurassic and these were accreted to se sundaland in the cretaceous revised palaeogeographic reconstructions illustrating the tectonic and palaeogeographic evolution of sundaland and adjacent regions are presented

deformation history and u pb zircon geochronology of the high grade metamorphic rocks within the klaeng fault zone eastern thailand abstract in eastern thailand the klaeng fault zone includes a high grade metamorphic rock assemblage named nong yai gneiss which extends about 30 km in a nw se direction along the fault zone the rocks of this brittle fault strand consist of amphibolite to granulite grade gneissic rocks structural analysis indicates that the rocks in this area experienced three distinct episodes of deformation d1 d3 the first d1 formed large scale nw se trending isoclinal folds f1 that were reworked by small scale tight to open folds f2 during the second deformation d2 d1 and d2 resulted from ne sw shortening during the triassic indosinian orogeny before being cross cut by leucogranites d1 and d2 fabrics were then reworked by d3 sinistral shearing including shear planes s3 and mineral stretching lineations l3 la mc icp ms u pb zircon dating suggested that the leucogranite intrusion and the magmatic crystallization took place at 78 6 0 7 ma followed by a second crystallization at 67 1 to 72 1 0 6 ma both crystallizations occurred in the late cretaceous and it is suggested were tectonically influenced by se asian region effects of the west burma and shan thai sibumasu collision or development of an andean type margin the sinistral ductile movement of d3 was coeval with the peak metamorphism that occurred in the eocene during the early phases of the india asia collision

tectonic evolution of the sibumasu indochina terrane collision zone in thailand and malaysia constraints from new u pb zircon chronology of se asian tin granitoids three principal granite provinces are defined across se asia as follows 1 the western thailand myanmar burma province consists of hornblende biotite i type granodiorite granites and felsic biotite k feldspar garnet tourmaline granites associated with abundant tin mineralization in greisen type veins new ion microprobe u pb dating results from phuket island show zircon core ages of 212 2 and 214 2 ma and a thermal overprint with rims of 81 2 1 2 and 85 75 ma 2 the north thailand west malaya main range province has mainly s type biotite granites and abundant tin mineralization resulting from crustal thickening following collision of the sibumasu plate with indochina during the mid triassic biotite granites around kuala lumpur contain extremely u rich zircons up to 38000 ppm that yield ages of 215 7 and 210 7 ma 3 the east malaya province consists of dominantly permian triassic i type hornblende biotite granites but with subordinate s type plutons and a type syenite gabbros biotite k feldspar granites from tioman island off the east coast of malaysia also yield a zircon age of 80 1 ma showing cretaceous magmatism in common with province 1 geological and u pb geochronological data suggest that two east dipping in present day coordinates subduction zones are required during the triassic one along the bentong raub palaeo tethyan suture and the other west of the phuket burma province 1 belt supplementary material a full description of u pb analytical methods used and data tables are available at www geolsoc org uk sup18523

karst collapse susceptibility assessment a case study on the amalfi coast southern italy abstract this paper presents a study to evaluate the collapse susceptibility of a karst cave located along a slope on the amalfi coast southern italy and the presumable geomorphological evolution of the whole slope as a result of cave roof collapse in the study area several natural karst caves with volumes varying between 1000 and 10 000 m 3 were inventoried and the most likely genetic processes were identified some of them proved to be remnants of already collapsed caves while others were in precarious stability conditions the caves are usually located upslope or very close to the main populated resorts a detailed geological geomorphological and geostructural study was performed on a very wide deep cave called the saraceno cave on which the resort town of conca de marini has been built the study was carried out through a multidisciplinary approach which included classical field geological observations sometimes requiring the support of rock climbing geologists experts in photogrammetric surveys and terrestrial laser scanning techniques tls tls surveys allowed the reconstruction of an accurate geometric and geostructural model of the cave and its relationship with the upslope conca de marini resort furthermore it allowed the thickness of the cave overburden to be determined in detail ground surfaces most susceptible to collapse were also identified in the event of possible widespread collapse several buildings and transportation infrastructures could be involved as the cave is located on a very steep slope a debris avalanche could be triggered in the event of a catastrophic failure and the landslide debris characterized by a presumably high magnitude and velocity could involve a wide slope area down to the coast the failure evolution could be very similar to that which took place in amalfi in the late 19th century

u pb zircon dating of granitoid plutons from the west coast province of peninsular malaysia u pb zircon dating of granitoid plutons from the west coast province of peninsular malaysia yields precise and unambiguous ages of 198 220 ma late triassic these ages are considerably older than previously reported k ar mica ages which have been largely reset but agree with or are younger than rb sr whole rock apparent ages the u pb zircon ages are considered to represent the best estimate of the intrusive ages of the plutons some of the problems associated with the interpretations of the pre triassic rb sr whole rock apparent ages are discussed here and alternative ways to explain these ages in the light of recent work are considered reversely discordant patterns displayed by zircon populations from a number of plutons yield consistent upper intersection ages of 1500 1700 ma that approximately date source derived inherited zircon components the precambrian ages of these inherited zircon components suggest that the west coast province s type granitoids are derived from sedimentary sources recycled at least in part from mid proterozoic crystalline basement sources

rb sr sm nd and u pb geochronology of the rocks within the khlong marui shear zone southern thailand abstract in southern thailand the khlong marui shear zone is dominated by a nne ssw striking high topographic lozenge shaped area of ca 40 km long and 6 km wide between the khlong marui fault and the bang kram fault the geology within this strike slip zone consists of strongly deformed layers of mylonitic meta sedimentary rocks associated with orthogneisses mylonitic granites and pegmatitic veins with a steeply dipping foliation the strike slip deformation is characterized by dextral ductile deformation under amphibolite facies and low to medium greenschist facies in situ u pb ages of inherited zircon cores from all zircons in the khlong marui shear zone indicate that they have the same material from the archean late triassic to late cretaceous ages obtained for zircon outer cores of the mylonitic granite are probably related to a period of magmatic activity that was significantly influenced by the west burma and shan thai collision and the subduction along the sunda trench the early dextral ductile deformation phase of the khlong marui shear zone in the early eocene suggested by u pb ages of zircon rims and the later dextral transpressional deformation in the late eocene indicated by mica rb sr ages rb sr sm nd and u pb dating correlation implies that the major exhumation period of the ductile lens was in the eocene this period was tectonically influenced in the se asia region by the early india asia collision

groundwater flow fields in infinite slopes this technical note presents an analytical description of all posssible groundwater flow fields in infinite slopes these flow fields may have any spatial orientation and may be affected by hydraulic anisotropy and heterogeneity but they may produce pore pressures or seepage forces that vary only in the co ordinate direction normal to the slope surface an equation is presented that together with its specialized forms define hydraulic gradients and hence determine pore pressure distributions and seepage forces in infinite slopes the practical ramifications of this equation are discussed

the january 10 1997 pozzano landslide sorrento peninsula italy abstract from 1997 to 1999 a huge number of slides often turning into extremely rapid debris earth flows repeatedly affected the late quaternary volcaniclastic deposits mantling the carbonate slopes of campania region italy the sorrento peninsula was the epicentral district of the 1997 regional slope instability crisis some hundred shallow mass movements took place during january 1997 in this area these were the last episode of a long series of slope failure events dating back to mid 18th century results from geological and geomorphologic surveys are presented landslide mechanism and triggering factors are analysed for the most important mass movement which occurred during the january 9 11 1997 regional event on january 10 1997 at about 8 15 pm a rainfall induced debris slide debris flow occurred at pozzano province of naples mainly affecting the 79 ad pyroclastic products following a j path the landslide destroyed a private house and invaded the state road no 145 this event resulted in four deaths 22 persons injured and road closure for about 2 months there was less than 200 mm of rainfall in the 72 h period prior to the landslide although intense precipitation had occurred during a preceding 4 month period however the slope failure event was not preceded by an extreme short term antecedent rainfall as already noticed in previous landslides of this type in campania finally following a preliminary geotechnical characterization of volcaniclastic soils a slope stability back analysis was carried out which adopted the classical infinite slope scheme this analysis gave further evidence of the role played by pore pressure in reducing the overall shear strength of pyroclastic soils

the permian fusulinoidean faunas of the sibumasu and baoshan blocks their implications for the paleogeographic and paleoclimatologic reconstruction of the cimmerian continent abstract permian fusulinoidean faunas occur in mainly four stratigraphic levels in the baoshan block of west yunnan and the sibumasu block of southeast asia which constituted part of the eastern cimmerian continent the oldest fauna from the upper part of the dingjiazhai formation in the baoshan block consists of pseudofusulina eoparafusulina and a new boultoniid genus and is assignable to the yakhtashian artinskian the second one which occurs in the basal part of the ratburi limestone and its equivalent strata in the sibumasu block is represented by monodiexodina and is probably referable to the bolorian kungurian the third fauna composed of eopolydiexodina rugososchwagerina yangchienia chusenella jinzhangia and several other genera is dated to the murgabian wordian and occurs in the lower part of the shazipo and daaozi formations in the baoshan block and the main part of the ratburi limestone in the sibumasu block the youngest fauna of probably dzhulfian wuchiapingian age is found in the upper part of the ratburi limestone and contains nanlingella reichelina codonofusiella and a few staffellid genera a smaller foraminiferal genus shanita found from the upper part of the ratburi limestone and the upper part of the shazipo formation is also an important element of the foraminiferal assemblage near the midian dzhulfian capitanian wuchiapingian boundary in the baoshan and sibumasu blocks in the eastern cimmerian continent low generic diversity throughout the permian and the paucity of tethys characterizing neoschwagerinid and verbeekinid genera during middle permian time are two remarkable features of the permian fusulinoidean faunas in the cimmerian continent the generic diversity of permian fusulinoidean faunas in space and time gradually increases from the early permian to late middle permian as well as from the eastern cimmerian areas to western ones the temporal increase of the generic diversity can be explained by the northward drift of the cimmerian continent during permian time in contrast the lower generic diversity of the eastern cimmerian permian fusulinoidean faunas against western ones is possibly due to an oblique arrangement of the continent to paleolatitude thus the western cimmerian continent was more proximal to the tropical tethyan domain than its eastern part in addition the middle permian cimmerian paleobiogeographic region is likely to be subdivided into two subregions the western tethyan cimmerian and the eastern gondwanan cimmerian based on the distribution pattern of verbeekinid and neoschwagerinid fusulinoideans and overall generic diversity the scarce occurrence or total absence of these essentially tethys indicating fusulinoideans in the baoshan and sibumasu blocks suggests that the eastern cimmerian continent was still far from the equatoro tropical cathaysian domain and was probably in a warm temperate or subtropical zone until the end of the permian the eastern cimmerian areas finally migrated into a tropical zone by the late triassic judging from well developed carnian sponge coral buildups in the chaiburi formation in the sibumasu block

hydrogeological assessment of a deep seated coastal landslide based on a multi disciplinary approach abstract this study focuses on the understanding of the hydrogeological functioning of a complex landslide affecting the coastal municipality of villerville normandy france we wish to provide a conceptual model of functioning using a multi disciplinary approach a set of geomorphological geological and hydrological data as well as in situ observations were first used to understand the main landslides processes new acquisitions were then carried out to strengthen our hypotheses thanks to passive geophysics sp and the characterization of physicochemical parameters of surface waters the joint analysis of former ert surveys and sp results is of significant interest for correlating hydrokinetic information measured at the surface with resistivity tomograms which provide internal information this study highlights 1 a division of the behaviour into three parts from east to west 2 variable internal dynamics highlighted by geology and electric fields 3 a preferential discharge of the continental water table upstream of the central area of the landslide this work tends to demonstrate that on the basis of initial in situ knowledge available on many study areas the understanding of the hydrogeological functioning can be substantially improved by implementing light and inexpensive surveys also suitable for large and complex landslides

the hydro mechanical behaviour of unsaturated pyroclastic soils an experimental investigation abstract an experimental investigation into the hydro mechanical behaviour of a pyroclastic silty sand was carried out in the framework of a research project on flowslides in pyroclastic soils in the campania region italy undisturbed soil samples were taken from the subsoil layers of a test site on a limestone relief mantled by a pyroclastic unsaturated soil cover the lab investigation was focused on the hydro mechanical behaviour of a pyroclastic silty sand originated from the ottaviano eruption of the somma vesuvius volcano some 8000 years ago the main features of the hydraulic hysteresis domain were evaluated and the matric suction range showing the peak saturation rate with respect to suction was identified using water retention data obtained by means of evaporation and soaking tests the mechanical behaviour of ottaviano pozzolana emerged from stress path controlled triaxial tests on saturated specimens and stress path and suction controlled triaxial tests on unsaturated specimens average soil skeleton stress and matric suction were adopted as stress variables to present and interpret the experimental results the effects of the unsaturated state on isotropic compressibility and on critical state shear strength are presented and discussed

rapid least squares inversion of apparent resistivity pseudosections by a quasi newton method1 a fast inversion technique for the interpretation of data from resistivity tomography surveys has been developed for operation on a microcomputer this technique is based on the smoothness constrained least squares method and it produces a two dimensional subsurface model from the apparent resistivity pseudosection in the first iteration a homogeneous earth model is used as the starting model for which the apparent resistivity partial derivative values can be calculated analytically for subsequent iterations a quasi newton method is used to estimate the partial derivatives which reduces the computer time and memory space required by about eight and twelve times respectively compared to the conventional least squares method tests with a variety of computer models and data from field surveys show that this technique is insensitive to random noise and converges rapidly this technique takes about one minute to invert a single data set on an 80486dx microcomputer

prediction of the shear deformation of a sandy model slope generated by rainfall based on the monitoring of the shear strain and the pore pressure in the slope abstract it is important to predict shear deformation of a slope due to rainfall infiltration as the basis of the time prediction of an onset of a rainfall induced landslide monitoring of deformations and soil water conditions in a sandy model slope under artificial rainfall was performed to establish the prediction method for shear deformation of the slope due to rainfall infiltration a prediction method for the relationship between shear strain and pore pressure was proposed based on the hyperbolic relationship between shear strain and pore pressure measured in the slope shear strain is predicted as a function of time before the failure of the slope based on the regression analyses of the shear strain pore pressure relationship and the time pore pressure relationship prediction of the shear strain using data until a later time could better simulate the measured values the predicted shear strain in the deeper layer fit the measured values better than that in the shallower layer a prediction method for the time surface displacement relationship was also proposed the procedure for the prediction is the same as that for the prediction of the shear strain except the surface displacement and the groundwater level replace the shear strain and the pore pressure respectively in the procedure the prediction with data even at an early stage of the experiment could simulate the time variation of the surface displacement well the proposed prediction method for the surface displacement produced better simulation results than the prediction method for the shear strain

temperature and bulk composition control on the growth of monazite and zircon during low pressure anatexis mount stafford central australia the formation age and trace element composition of zircon and monazite were investigated across the prograde low pressure metamorphic sequence at mount stafford central australia three pairs of inter layered metapelites and metapsammites were sampled in migmatites from amphibolite facies t 600 c to granulite facies conditions t 800 c sensitive high resolution ion microprobe u pb dating on metamorphic zircon rims and on monazite indicates that granulite facies metamorphism occurred between 1795 and 1805ma the intrusion of an associated granite was coeval with metamorphism at 1802 3ma and is unlikely to be the heat source for the prograde metamorphism metamorphic growth of zircon started at t 750 c well above the pelite solidus zircon is more abundant in the metapelites which experienced higher degrees of partial melting compared with the associated metapsammites in contrast monazite growth initiated under sub solidus prograde conditions at granulite facies conditions two distinct metamorphic domains were observed in monazite textural observations petrology and the trace element composition of monazite and garnet provide evidence that the first metamorphic monazite domain grew prior to garnet during prograde conditions and the second in equilibrium with garnet and zircon close to the metamorphic peak ages from sub solidus prograde and peak metamorphic monazite and zircon are not distinguishable within error indicating that heating took place in less than 20 myr

long term investigations on the pore pressure regime in saturated and unsaturated sloping soils abstract pore pressure changes play a major role in the stability of natural slopes whose safety factor value is usually much smaller than that generally accepted in any other geotechnical problem correct assessment of potential seasonal pore pressure distributions is therefore a crucial issue in slope stability analysis based on long term monitoring of some natural slopes this paper compares the pore pressure distribution recorded in saturated fine grained deposits and in shallow unsaturated granular covers both monitored in southern italy in spite of the expected differences the soils display some common features in particular from december to mid may wet period in all examined cases the pore water pressures are quite constant over a monthly scale thus an essentially steady state pore pressure condition establishes it is in this phase which is characterised by an essentially downward flux that the safety factor drops to its lowest yearly value finally a simplified method is adopted to model the steady state pore pressure during the wet period and to calculate the average rain infiltration in equilibrium with the steady state condition the results thereby obtained are compared with the findings of an advanced approach based on the hydrological balance

a tectonic model for the tertiary evolution of strike slip faults and rift basins in se asia abstract models for the tertiary evolution of se asia fall into two main types a pure escape tectonics model with no proto south china sea and subduction of proto south china sea oceanic crust beneath borneo a related problem is which if any of the main strike slip faults mae ping three pagodas and aliao shan red river asrr cross sundaland to the nw borneo margin to facilitate continental extrusion recent results investigating strike slip faults rift basins and metamorphic core complexes are reviewed and a revised tectonic model for se asia proposed key points of the new model include 1 the asrr shear zone was mainly active in the eocene oligocene in order to link with extension in the south china sea the asrr was less active during the miocene tens of kilometres of sinistral displacement with minor amounts of south china sea spreading centre extension transferred to the asrr shear zone 2 at least three important regions of metamorphic core complex development affected indochina from the oligocene miocene mogok gneiss belt doi inthanon and doi suthep around the asrr shear zone hence paleogene crustal thickening buoyancy driven crustal collapse and lower crustal flow are important elements of the tertiary evolution of indochina 3 subduction of a proto south china sea oceanic crust during the eocene early miocene is necessary to explain the geological evolution of nw borneo and must be built into any model for the region 4 the eocene oligocene collision of ne india with burma activated extrusion tectonics along the three pagodas mae ping ranong and klong marui faults and right lateral motion along the sumatran subduction zone 5 the only strike slip fault link to the nw borneo margin occurred along the trend of the asrr fault system which passes along strike into a right lateral transform system including the baram line

unsaturated soil mechanics in rainfall induced flow landslides abstract rainfall induced flow landslides in coarse grained soils pose significant threats to populations and structures due to their high velocities long travel distance and the absence of definite warning signs during the pre failure stage the triggering phase of these phenomena is frequently related to rainfall events which significantly reduce matric suction in the shallower soil layers in this paper the processes leading to the onset of such phenomena are illustrated and some observations on their modelling are briefly recalled the failure stage at different scales is then modelled with reference to a case study from southern italy which draws on high quality experimental data sets from extensive in situ and laboratory investigation

coupled hydro mechanical analysis of two unstable unsaturated slopes subject to rainfall infiltration abstract this paper presents a case study and numerical investigation of two unstable unsaturated slopes along the taipei maokong gondola system one slope collapsed because of torrential rainfall during typhoon jangmi in september 2008 and another nearby slope developed excessive deformation under consecutive wetting and drying cycles recorded rainfall measured soil parameters site geology and slope geometry were used in coupled hydro mechanical finite element analyses to investigate the failure and deformation mechanisms of these two slopes the stress paths of these two slopes were also examined and are discussed in this paper the numerical results demonstrated that the coupled hydro mechanical analysis satisfactorily predicted the failure and deformation characteristics of the two unstable slopes in the collapse case failure occurred at a shallow depth when the surficial residual soil was saturated the slope failure was attributed to a decrease in soil shear strength when the matric suction gradually decreased as rainfall progressed in the excessive deformation case the numerical results suggested that pore water pressure pwp varied at shallow depths under wetting and drying cycles whereas positive pwp accumulated at the soil rock interface and induced non uniform lateral flows parallel to the interface the accumulated positive pwp at the interface mobilized a considerable plastic deformation in the soil examination of the relationships between the slope factor of safety and the corresponding hydrological data i e rainfall and soil pwp revealed a positive correlation between the slope factor of safety and accumulated rainfall the factor of safety predicted by the infinite slope equation significantly varied with the input of pwp this study demonstrated that the infinite slope equation using the pwp measurements obtained from the lower half of the slope could effectively predict the slope factor of safety

zircon and monazite upb dating of the doi inthanon core complex northern thailand implications for extension within the indosinian orogen abstract the doi inthanon metamorphic core complex occupies a prominent central position within the northwestern thai gneiss belt which has been inferred to be as old as precambrian and as young as permo triassic u pb dating of zircon from core orthogneisses of the complex suggests that the orthogneisses were derived from granitic protoliths with essentially the same late triassic early jurassic age as the mae cham pluton 205 3 4 ma to the west of the doi inthanon complex monazite ages from the orthogneisses indicate that low pressure and high temperature metamorphism and migmatitization occurred in the late cretaceous 84 72 ma limited published radiometric age data from elsewhere in the migmatitic gneiss belt suggest that widespread minor plutonism accompanied this thermal event a younger u pb data of 26 8 0 5 ma for zircon and monazite from the mae klang granite which intruded mylonitic gneisses on the eastern side of the doi inthanon complex indicates that there was also significant plutonism in the late oligocene these u pb ages constrain the development of the complex and hence of the migmatitic gneiss belt as a whole to an interval between late cretaceous and early miocene ductile shearing uplift and tectonic denudation via detachment faulting chronologically overlap the initiation of extensional basin development to the east and southeast of the gneiss belt and imply a genetic connection thus oligocene early miocene thermal rifting from the gulf of thailand northward into mainland thailand may have been the direct product of crustal extension rather than the transtensional product of regional strike slip faulting

zircon u pb ages in myanmar magmatic metamorphic events and the closure of a neo tethys ocean abstract previous isotopic age studies have concluded that the main metamorphism in the mogok metamorphic belt mmb in myanmar was tertiary and caused by collision with or underthrusting by india we present here results of zircon u pb age determinations on 18 samples from myanmar largely on intrusive rocks from the north trending 550 km long shan scarps segment of the sickle shaped mmb the oldest determination is 491 ma on orthogneiss north of mandalay interpreted as a protolith age and similar to the stratigraphic age of the bawdwin volcanics augen gneiss at kyaukse has a 114 ma protolith age our zircon u pb ages on undeformed intrusive rocks in the mmb range from cretaceous to miocene the oldest 128 ma on a diorite near yebokson implies an earliest cretaceous minimum age for regional metamorphism here younger ages on undeformed intrusions include 91 ma on diorite at mokpalin 72 ma on the weakly foliated garnet bearing nattaung granite 44 and 48 ma respectively on the mec and sedo granites and 17 20 ma on granite dykes for the 128 ma diorite sr and nd isotopes indicative of a continental crust component and mapped continuity of metamorphic host rocks suggest correlation with mid early cretaceous plutons in the eastern transhimalayas zircon u pb ages for the mec sedo and other granites within the mmb and slate belt help to define a late cretaceous to early eocene age range for mostly ilmenite series peraluminous granites within the western granite belt and more restricted western tin belt of myanmar and southern thailand in the wuntho popa arc west of the dextral sagaing fault our new u pb zircon age of 105 ma on diorite at salingyi supports previous k ar ages 106 93 ma for pre tertiary intrusions in the cretaceous this arc may have occupied the andaman sea and continued northwards through the mokpalin diorites and west of the mmb to the 103 80 ma i type plutons in the gandise batholith of southern tibet we interpret the mmb and slate belt as part of a western myanmar block separated in the jurassic from the shan plateau to the east by the southwestward continuation of the bangong nujiang luxi neo tethys i ocean we relate most intrusive and metamorphic events in and near the mmb to westward subduction of this ocean and end jurassic collision of the plateau with the overriding western myanmar slate belt block to orogenic polarity reversal and early cretaceous westward translation of the plateau sequence over the suture zone and to eastward subduction of the ancestral indian ocean or neo tethys ii beneath myanmar with generation of the wuntho popa arc beginning before the late cretaceous the mmb includes meta plateau rocks near mandalay but meta slate belt rocks to the north and south within the mmb previous monazite xenotime thorite ages of eocene oligocene and oligocene early miocene cooling ages on micas with no deformation in eocene granites suggest a high temperature thermal event related to intrusion of these and other granites during a previously proposed regional extension our data imply that the main fabric forming metamorphic event in the mmb pre dated the india asia collision

investigation of soil atmosphere interaction in pyroclastic soils summary this paper investigates the interaction between soil and atmosphere in pyroclastic soils with a view to understanding whether and to what extent the prediction of the hydraulic and mechanical behaviour of geotechnical problems cuts slope stabilities embankments foundation retaining structures regulated by rainfall induced fluctuations of matric suction is influenced by evaporation phenomena evaporation fluxes are quantified and compared with other fluxes precipitation run off deep drainage affecting soil water content and matric suction this work is based on the data collected through a physical model over 2 years of experimental tests the model consisted of a 1 m 3 tank filled in this case with pyroclastic soil and exposed to natural weather elements the system was extensively monitored to record atmospheric and soil variables the results provided by the experiments highlight the importance of the top soil state in determining the intensities of infiltrating rainfall and actual evaporation the results also bring to light the significance of evaporation which during the dry season largely prevails over infiltration raising suction to very high values also during the wet season evaporation gives rise to a non negligible flux with respect to the infiltrated precipitation the reliability of two pre existing empirical models to estimate evaporation flux is also investigated and appraised within this paper