topography of the variscan orogen in europe failed not collapsed the variscan orogenic collage consists of three subduction collision systems rheno hercynian saxo thuringian and massif central moldanubian devonian to early carboniferous marine strata are widespread not only in the individual foreland fold and thrust belts but also in post tectonic basins within these foreland belts and on the cadomian crust of peri gondwanan microcontinental fragments which represent the upper plates of the subduction collision zones these marine basins preclude high elevations in the respective areas and also in their neighbourhood widespread late carboniferous intra montane basins with their coal bearing sequences are likewise incompatible with high and dry plateaus while narrow belts with high elevations remain possible along active margins within the orogen comparison of the variscides with the himalaya tibetan plateau is unfounded plausible reasons for the scarcity of high variscan relief include subduction of oceanic and even continental crust subduction erosion orogen parallel extension and most important lithospheric thinning accompanied by high heat flow and magmatism in many areas timing and areal array of magmatism and ht metamorphism are not compatible with a model of tectonic thickening and subsequent gravitational collapse it is suggested instead that lithospheric thinning and heating are due to mantle activities caused by the tethys rift the lower and middle crust were thermally softened and rendered unfit for stacking and isostatic uplift in terms of topography the variscides represent a failed orogen the ht regime also explains the abundance of granitoids and ht lp metamorphic rocks typical of the variscides melting in the ht regime extracted mafic components from variscan and cadomian crust as well as from cadomian metasomatized lithospheric mantle thus mimicking subduction related magmatism the onset of the ht regime at c 340 ma may also have triggered the final ascent of hp uhp felsic metamorphic rocks

geological hazards in loess terrain with particular reference to the loess regions of china abstract the considerable morphodynamic energy provided by the continuing tectonic evolution of asia is expressed in high erosional potentials and very high rates of sediment production that make this continent unequalled as a terrestrial source of primary silt many of these environments are hazardous threatening human occupation health and livelihood especially in regions of dense population such as the loess lands of north china dry loess can sustain nearly vertical slopes being perennially under saturated however when locally saturated it disaggregates instantaneously such hydrocompaction is a key process in many slope failures made worse by an underlying mountainous terrain of low porosity rocks gully erosion of loess may yield very high sediment concentrations 60 by weight characteristic vertical jointing in loess influences the hydrology enlarged joints develop into natural sub surface piping systems which on collapse produce a loess karst terrain collapsible loess up to 20 m thick is common on the western loess plateau foundation collapse and cracked walls are common many rapid events following periods of unusually heavy monsoonal rain slope failure is a major engineering problem in thick loess terrain flow slide and spread types being common the results are often devastating in both urban and rural areas an associated hazard is the damming of streams by landslides the human population increases the landslide risk in china notably through imprudent land use practices including careless water management a number of environmentally related endemic diseases arise from the geochemistry of loess and its groundwaters including fluorosis cretinism kaschin beck disease keshan disease and goitre the chinese desert margins also have a major atmospheric dust problem the effect of such dust upon human health in these extensive regions including many large cities has yet to be evaluated but pneumoconiosis is thought to affect several million people in north and west china

the palaeozoic variscan oceans revisited abstract geological evidence supported by biogeographical data and in accord with palaeomagnetic constraints indicates that one ocean models for the variscides should be discarded and confirms instead the existence of three gondwana derived microcontinents which were involved in the variscan collision avalonia north armorica franconia and thuringia subdivided by a failed vesser rift and south armorica central iberia armorica bohemia all divided by small oceans in addition parts of south eastern europe including adria and apulia are combined here under the new name of palaeo adria which was also peri gondwanan in the early palaeozoic oceanic separations were formed by the break up of the northern gondwana margin from the late cambrian onwards most of the oceans or seaways remained narrow but much like the alpine cenozoic oceans gave birth to orogenic belts with hp uhp metamorphism and extensive allochthons the saxo thuringian ocean between north and south armorica and the galicia moldanubian ocean between south armorica and palaeo adria only the rheic ocean between avalonia and peri gondwana was wide enough to be unambiguously recorded by biogeography and palaeomagnetism and its north western arm closed before or during the emsian in europe ridge subduction under the northernmost part of armorica in the emsian created the narrow and short lived rheno hercynian ocean it is that ocean and not the rheic whose opening and closure controlled the evolution of the rheno hercynian foldbelt in south west iberia south west england germany and moravia czech republic devonian magmatism and sedimentation set within belts of early variscan deformation and metamorphism are probably strike slip related the first arrival of flysch on the forelands and or the age of deformation of foreland sequences constrains the sequential closure of the variscan seaways galicia moldanubian in the givetian saxo thuringian in the early famennian rheno hercynian in the tournaisian additional mid to late devonian and partly early carboniferous magmatism and extension in the rheno hercynian saxo thuringian and galicia moldanubian basins overlapped with variscan geodynamics as strictly defined the early carboniferous episode was the start of episodic anorogenic heating which lasted until the permian and probably relates to tethys rifting

the loess of north central china geotechnical properties and their relation to slope stability abstract loess is an aeolian deposit consisting of predominantly silt sized quartz particles and containing variable amounts of clay sized minerals loess is generally classified as a water softening material because upon wetting the loess fabric rapidly weakens or collapses the strain hardening of malan loess and the brittle failure of lishi and wucheng loess are in strong contrast to the failure behaviour of these loess deposits in a remoulded state from tests carried out on samples with varying moisture contents using a modified bromhead ring shear apparatus it was found that the effective apparent cohesion gradually increases and the effective internal friction angle decreases with an increase in moisture content when the moisture content reaches a material specific threshold the effective cohesion decreases rapidly and the effective internal friction angle stabilises at a residual value the frequent failure of loess slopes in the western part of the chinese loess plateau is closely related to progressive weathering along zones in these slopes which causes a dramatic decrease in strength from the peak strength condition progressive weathering is common in the loess slopes in the western part of the chinese loess plateau during the process shear strength reduction along potential slip surfaces may be achieved by leaching of readily soluble salts destruction of cementation bonds and redistribution of particles localized collapse of the loess fabric causes internal deformation and consequently peak strength conditions are concentrated on a progressively smaller area of the failure plane therefore the mode of failure of loess slopes is generally determined by brittle failure of the undisturbed and unweathered central parts of the slopes it is important that both the weathered and unweathered strength of the loessmaterials in this area be established in order to analyze the stability of existing loessslopes many of which are steepand lie directly above domestic and industrial urban areas

evolution of the rheic ocean the rheic ocean which separated laurussia from gondwana following the closure of iapetus is arguably the most important ocean of the palaeozoic its suture extends from mexico to turkey and its closure produced the climactic variscan alleghanian ouachita orogeny that assembled the supercontinent pangaea following protracted cambrian rifting that represented a continuum from neoproterozoic orogenic processes the rheic ocean opened in the early ordovician with the separation of several neoproterozoic arc terranes from the continental margin of northern gondwana separation occurred along the line of a former neoproterozoic suture following the onset of subduction in the outboard iapetus ocean the timing of rift drift transition and drive for subsequent spreading was likely governed by slab pull accounting for the rapid rate 8 10 cm yr at which the rheic ocean widened during the ordovician the ocean broadened at the expense of iapetus and attained its greatest width 4000 km in the silurian by which time baltica had sutured to laurentia and the neoproterozoic arc terranes had accreted to laurussia closing iapetus in the process closure of the rheic ocean began in the devonian and was facilitated by northward subduction beneath southern baltica and southward subduction beneath northwest gondwana closure was largely complete by the mississippian as gondwana and laurussia sutured to build pangaea north africa colliding with southern europe to create the variscan orogen in the devonian carboniferous and west africa and south america suturing to north america to form the alleghanian and ouachita orogens respectively during the carboniferous permian the rheic ocean consequently plays a dominant role in the basement geology of southern europe in the appalachian ouachita orogeny of north america and in the palaeozoic sedimentary structural and tectonothermal record from middle america to the middle east with its closure the ocean brought about the assembly of pangaea and brought the palaeozoic era to an end

geological and geotechnical characteristics of some loess and loessic soils from china and britain a comparison abstract derbyshire e and mellors t w 1988 geological and geotechnical characteristics of some loess and loessic soils from china and britain a comparison eng geol 25 135 175 loess and loessic deposits cover some 630 000 km 2 of the surface of mainland china the loess plateau of shanxi shaanxi gansu and ningxia being the type region of this formation loess thickness generally exceeds 100 m over large areas of the loess plateau the maximum recorded thickness being 335 m in eastern gansu province near the city of lanzhou in britain loess and loessic deposits form part of a group of materials collectively known as brickearth they occur predominantly as sporadic accumulations in the southeast of england and rarely attain a thickness of more than four metres despite their geographical separation the deposits from china and britain have a remarkable similarity in some of their physical and geotechnical characteristics samples from both locations have been examined and tested in the laboratory and the results are presented the scope of the testing programme involved mineralogical analyses soil microfabric studies using a scanning electron microscope index testing including plasticity grading and density measurements and the investigation of the compressibility characteristics of the soils with particular reference to their susceptibility to collapse a soil structure model based on scanning electron microscope studies is presented and discussed in relation to the perceived mode of formation of the soils and their postdepositional history

baltic provenance of top famennian siliciclastic material of the northern rhenish massif rhenohercynian zone of the variscan orogen the provenance of top famennian sedimentary rocks linked to the hangenberg crisis from the northern rhenish massif germany was investigated by the means of detrital zircon u pb geochronology based on the obtained age spectra three main tectonothermal domains are recognized as possible sources paleo and mesoproterozoic 2000 1000 ma units of baltica and early paleozoic caledonian orogen 500 400 ma our interpretation of the detritus having been derived from northern source areas i e baltica and the scandinavian caledonides with a minor input of german polish rugen pomeranian caledonides contradicts the traditional view that during the upper devonian the northern rhenish massif was supplied by detritus from the south complementary mineralogical textural and geochemical analyses point to a derivation of the detritus of drewer and hangenberg sandstones mainly from felsic recycled continental crust the elevated concentrations of pb and zn in the studied sections are a feature attributed to hydrothermal alteration related to the terminal devonian synsedimentary volcanism or post depositional variscan deformation

back to sender tectonic accretion and recycling of baltica derived devonian clastic sediments in the rheno hercynian variscides sedimentary petrography and zircon icp ms laser ablation ages from synorogenic clastic sediments in the rheno hercynian belt of germany rheinisches schiefergebirge harz reveal basal tectonic accretion followed by exhumation and recycling of baltica derived devonian shelf sediments the recycled sediment volume demands a substantial palinspastic addition to the passive northern margin of the rheno hercynian basin detrital zircon ages from the late carboniferous foreland basin and their possible source rocks in the south portuguese zone permit the same interpretation this suggests that synorogenic sedimentation in portugal is related like in germany to the closure of the devonian carboniferous rheno hercynian basin and not to the closure of the ordovician silurian rheic ocean

brachiopod faunas facies and biostratigraphy of the pridolian to lower eifelian succession in the rhenish massif rheinisches schiefergebirge germany

failure mechanisms in loess and the effects of moisture content changes on remoulded strength abstract investigations into the failure mechanisms of loess slopes in the loess region of north central china have shown that a majority of mass movements are associated with shallow slab slides predominantly moving under tension the effects of soil moisture content are of paramount importance when dry vertical slopes in loess may exceed 15 m in height but under conditions close to saturation the structural strength of loess rapidly decreases causing failure of the slopes mass failure of loess occurs as collapse due to hydroconsolidation and disintegration of the loess fabric as a result of liquefaction or fluidization and can be associated with progressive failure processes local destruction of the openwork fabric of the loess can lead to small plastic movements within the loess deposits this is as close as loess can come to creep

modelling the erosional susceptibility of landslide catchments in thick loess chinese variations on a theme by jan de ploey abstract in his 1990 paper catena 17 175 183 jan de ploey proposed a system whereby catchments are viewed as functional units in which geomorphic work results from the combined effects of water erosion and mass movements his measure of erosional susceptibility of catchments es introduced the gravitational potential in addition to the kinetic energy of the eroding agents this modelling of the erosional susceptibility of catchments in terms of energy was being used to explore time dependent variations of es when jan de ploey died also at this time he extended an invitation to the present authors to test and extend his model using our data base on the landslide dominated catchments in the thick loess country of north central china this paper presents a series of new equations expressing variations in es using a data base for over 200 landslides in the loess covered mountainous terrain relative relief up to 1500 m of the lanzhou region of eastern gansu province these equations express the loss of potential energy of the landslide mass in relation to the relative relief and the pressure energy input in the form of rainfall these indices of erosional susceptibility can be used to analyse the differences in response from one catchment to another and through time between the characteristics of vegetation cover including land use hydrology geomechanical behaviour and mechanisms of movement on slopes using certain assumptions on percentage area of catchments affected by mass movement and long term mean annual precipitation in the lanzhou region the es equation suggests an estimate for non clayey materials of about 10 4 m 2 s 2 which is a significantly higher susceptibility value than the mean worldwide value for non clayey materials obtained by de ploey

the cambrian to devonian odyssey of the brabant massif within avalonia a review with new zircon ages geochemistry sm nd isotopes stratigraphy and palaeogeography abstract this study provides an up to date and comprehensive review of the early palaeozoic evolution of the brabant massif belonging to the anglo brabant deformation belt situated at the southeastern side of avalonia microplate it is the only well known part of the northern passive margin of the rheic ocean the cambrian silurian sedimentary pile is 13 km thick with 9 km for the cambrian only the unraveling of this continuous registration reflects the successive rifting and drifting of avalonia from the gondwana mainland followed by soft collisional processes with baltica and finally the formation of laurussia based on recently established detailed stratigraphy sedimentology and basin development on u pb la icp ms analyses of igneous and detrital zircon grains along with geochemical data including sm nd isotopes a new geodynamic and palaeogeographic evolution is proposed brabant megasequence 1 lower cambrian to lowermost ordovician 9 km thick represents an embayment of the peri gondwanan rift from which the rheic ocean has evolved detrital zircon ages demonstrate that the brabant is a typical peri gondwanan terrane with a major pan african neoproterozoic age and a mixed west african and amazonian source palaeoproterozoic archaean and some mesoproterozoic age the transition towards the avalonia drifting is marked by an unconformity and a short volcanic episode the northward drift of avalonia towards baltica is recorded by the megasequence 2 middle to upper ordovician 1 3 km thick the source for mesoproterozoic zircons vanished as the result of the rheic ocean opening and the isolation from amazonian sources the transition to megasequence 3 is marked by a drastic change in palaeobathymetry and an important sub volcanic episode during a tectonic instability period 460 430 ma reflecting the avalonia baltica soft docking as also shown by the reappearance of mesoproterozoic detrital zircons typical of baltica unradiogenic nd isotope signature end 4 5 and tdm model ages 1 3 1 7 ga for brabant magmatic rocks indicate an old recycled component megasequence 3 uppermost ordovician to lowermost devonian 3 5 km thick includes the onset of a silurian foreland basin that reflects the tectonic inversion of the core of the massif brabantian orogeny in response to the baltica avalonia laurentia collision finally the comparison with the strikingly similar cambrian successions of the harlech dome wales avalonia and the meguma terrane nova scotia peri gondwana allows the construction of a new early cambrian palaeogeographic model for the whole avalonia microplate in which the meguma terrane is included

effects of chemical weathering and sorting on the petrogenesis of siliciclastic sediments with implications for provenance studies the bulk chemical compositions mineralogy and mineral proportions of sands and muds of the mallacoota basin in southeastern australia reflect the composition of weathering profiles mantling source rocks rather than bedrock muds contain abundant clay minerals that are virtually absent from the source rocks but abundant in the weathering profiles sands are strongly enriched in quartz relative to source rocks even in the headwaters of the fluvial system demonstrating that feldspar destruction occurs by in situ chemical weathering within profiles and before detritus enters the fluvial system k feldspar is proportionally more abundant in fluvial sands than in source rocks because plagioclase is more rapidly destroyed than either quartz or k feldspar in weathering profiles subsequent erosion and sorting produce sands enriched in quartz with high k feldspar plagioclase ratios relative to source rocks the composition of plagioclase incorporated into the fluvial sands is also controlled by chemical weat

accretion of a rifted passive margin the late paleozoic rhenohercynian fold and thrust belt middle european variscides in the western rhenish massif the rhenohercynian fold and thrust belt of the middle european varsicides exposes a telescoped complete devonian to early carboniferous passive margin this permits the analysis of geometry and kinematic processes of passive margin accretion to an erogenic wedge during variscan collision 330 300 ma the sedimentary cover of the passive margin was shortened by some 50 or 180 km crustal scale balancing and restoration reveals a wide symmetric rift with a central graben a marginal plateau separated this failed lower devonian rift from an emsian middle devonian oceanic basin in the south remnants of which are preserved in the southernmost imbricates and the giessen harz nappes the seismically well imaged aachen midi detachment faille du midi acted as the basal decollement of this thin to thick skinned orogenic wedge it shows a ramp and flat geometry from the blind tip down to middle crustal levels owing to its position below the base of the basin fill the thick synrift sequence and structure controlled structural evolution during contraction by localizing thrust branch lines and by inversion of rift structures synthetic to the subduction direction with formation of basement footwall shortcuts moreover the three dimensional detachment geometry shows large scale oblique ramp flat features which control the architecture of the belt and the distribution of metamorphic grade rocks and fabrics from the detachment show that the latter was located at the transition into the ductile field at the fossil 300 400 c isotherm in the restored section the detachment trajectory displays a saucershaped geometry rising to the surface at the rear and at the front this suggests that the basal detachment propagated into the passive margin by ductile failure during lithospheric flexure under the load of an advancing upper plate the regional pattern of synkinematic metamorphic grade shows varying modes of margin accretion basal underplating into the orogenic wedge by the shelf slope and marginal plateau with formation of duplex stacks and elongate thrust sheets and frontal accretion of the remaining thicker failed rift in the north into the propagating wedge with formation of several imbricate fans cyclical changes in accretion history and or critical taper are suggested by spaced domains of out of sequence thickening these are also related to internal domainal kinematic partitioning of the wedge controlled by oblique collision

prediction of some weathering trends of plutonic and volcanic rocks based on thermodynamic and kinetic considerations abstract the exposed crust consists mainly of plagioclase 35 quartz 20 k feldspar 11 volcanic glass 12 biotite 8 and muscovite 5 quartz is a resistate thus feldspars and glass represent approximately 75 percent of the labile minerals the weathering characteristics of these constituents are summarized in the context of thermodynamic mass balance and kinetic considerations experimentally determined release rate constants were used to predict the proportions of ca na and k released by feldspars of plutonic rocks granites to gabbros to weathering solutions the chemical weathering trends of the weathered residues calculated from the kinetic data conform closely to the initial trends observed in some recent weathering profiles demonstrating the accuracy of the predictions since the weathering of feldspars is controlled by processes that should not change through geological time the relative release rates of ca na and k from the feldspars of granitic rocks can be calculated for future and past episodes of continental weathering experimentally determined release rate constants are not available for a wide range of volcanic glass compositions but the limited data indicate that compositional trends are predictable in weathering profiles developed on volcanic rocks the kinetic data available for rhyolitic glasses accurately predict the initial weathering trends observed in a recent rhyolite weathering profile

reply to comment by m f pereira j b silva and c gama on baltic provenance of top famennian siliciclastic material of the northern rhenish massif rhenohercynian zone of the variscan orogen by koltonik et al international journal of earth sciences 2018 107 2645 2669

the rugen caledonides northeast germany borehole evidence from the isle of rugen and geophysical data from the adjacent baltic sea suggest a caledonian deformation front that caused nne directed thrusting on the east european platform it is thought to mark a caledonian suture zone which was reactivated in syn to post variscan events to form the romio mon fault zone

analysis of multi phase coupled seepage and stability in anisotropic slopes under rainfall condition the seepage deformation and stability in unsaturated soil slopes under rainfall infiltration are important issues in geotechnical engineering based on multi field coupling theory a finite element code comsol is employed to solve the coupled partial differential equations for soil slopes under rainfall infiltration the coefficient of permeability is a variable in the three phase coupled model the water seepage air migration deformation and stability in a soil slope due to precipitation are studied the effect of the wetting front caused by the migration of pore air and the deformation of soil are explored and the impact of soil anisotropy is analysed the results indicate that the effect of anisotropy on the pore water pressure is related to the depth and position of the unsaturated soil slope the factor of safety of the partially saturated slope is relatively high when the lateral coefficient of permeability of the slope is greater than the coefficient of permeability in the vertical direction the factor of safety is a function of the degree of anisotropy

collapsibility and deformation characteristics of deep seated loess in china abstract lin z g and wang s j 1988 collapsibility and deformation characteristics of deep seated loess in china eng geol 25 271 282 as part of a comprehensive research program laboratory tests were conducted on samples of deep seated loess from different locations of the loessial regions of northern china including shaanxi gansu shanxi and honan provinces the information thus acquired on some aspects of the engineering properties of the samples such as the unit collapse pressure relationships the initial collapse pressure versus the preconsolidation pressure and deformation pressure characteristics is interesting and may prove useful to geotechnical engineers who work on projects on water poor plateaux or high river terraces in loessial regions throughout the world

anoxia and fluctuating climate recorded from the devonian carboniferous black shales tethys himalaya india a multi proxy approach due to inaccessibility and tough conditions high altitude low oxygen region very less information is available about the indian tethys himalayan sequences particularly geochemical data are scarce an attempt is made in the present study to evaluate the sediment geochemistry and paleo redox conditions of devonian carboniferous black shales from the spiti region tethys himalaya using multi proxy approach besides black shales this paper also provides the first in depth study of the geochemistry of phosphatic nodules hosted by the black shales that will allow primary and secondary processes to be understood geochemical investigations particularly redox sensitive trace element ratios for e g v v ni 0 5 ni co 4 3 7 2 v cr 2 and positive ce anomalies suggest deposition of these black shales under sub oxic to anoxic marine conditions thus recording an ocean anoxic event in the region these ocean anoxic events of devonian carboniferous spiti black shales which possess distinctive geochemical signatures can very well be correlated with global events such as hangenberg events and the lower alum shale event the span of the chemical index of alteration cia values 54 78 variation of 4si parameter 82 3 and c values 0 1 0 6 recorded in the black shales strongly indicate varying degrees of weathering conditions in the source area which in turn reflect fluctuating climatic conditions prevailing during the deposition of these sediments in devonian carboniferous period in the spiti region the distinct geochemical characteristics such as y sr and rare earth element ree enrichments particularly middle ree enrichments with a hat shaped pattern with high p2o5 contents up to 14 wt distinguish the nodules from the host rocks black shales sem scanning electron microscope results supplemented by xrd x ray diffraction studies of the nodules show the dominance of calcium silica and phosphatic phases the diversity of clay minerals significant variations in mineralogical composition and lack of any continuous vertical trend in the nodules suggest a relatively low impact on the primary environmental signal by burial diagenesis

controlling factors of loess landslides in western china based on detailed field data from recent geo hazards surveys in the loess plateau region of western china this study analyzes the key factors that control loess landslides the evolution phase of river valleys the geological structure of slopes and the geometry of slopes are all found to play a role in determining the occurrence distribution and other characteristics of loess landslides groundwater and vegetation also contribute to their formation a combination of human engineering activities and precipitation events are the principal triggering factors for the instability of loess slopes

comment on baltic provenance of top famennian siliciclastic material of the northern rhenish massif rhenohercynian zone of the variscan orogen by koltonik et al international journal of earth sciences 2018 107 2645 2669 koltonik et al int j earth sci 107 2645 2669 2018 evidence that the late devonian siliciclastic rocks from the rheno hercynian zone in germany derived from baltica and scandinavian caledonides this finding together with what is known about the provenance of the pulo do lobo and south portuguese zones in portugal and spain reinforces the probability that late devonian basins may have been sourced from distinct terranes placed along the variscan suture our comment intends to underline changes in the provenance of the late devonian basins along the active margin of laurussia and also to improve the correlation model for the variscan tectonic units from sw iberia and germany

heavy rainfall triggered loess mudstone landslide and subsequent debris flow in tianshui china abstract continuous and heavy precipitation triggered a large loess landslide at the southern dagou village of mapaoquan town tianshui city gansu province of china on july 21 2013 the landslide debris rapidly turned into a debris flow that was deposited in the ravine mouth with the volume of 1 9 105 m3 detailed field mapping three dimensional laser scanning aerial photograph interpretation and laboratory tests were carried out to study the formation and moving characteristics of the landslide and subsequent debris flow the results showed that 1 the peak flow velocity and peak discharge of the debris flow were estimated to be approximately 7 2 m s and 730 m3 s respectively the velocity had a tendency to first increase and then decrease from the head to entrance in the dagou gully 2 the analysis of rainfall conditions showed that the effective antecedent rainfall within 7 days and hourly rainfall intensity which triggered the slide debris flows was 239 mm and 20 mm h respectively compared with the critical rainfall in this area the effective antecedent rainfall was found to be more significant in triggering this event 3 the mean and effective particle sizes were approximately 0 73 1 3 mm and 0 036 0 087 mm respectively and had the same distribution along the gully as the velocity which confirmed the process of the variation in the flow velocity 4 the scale amplification was very obvious in the formation and moving process of the slide debris flows

neogene clay and its relation to landslides in the southwestern loess plateau china loess occurs widely in northwestern china covering neogene clay and other sedimentary units that overlie the bedrock the neogene clays of the baoji region of shaanxi province north china including the eolian hipparion and paleo sanmen lake fluvial deposits are typical clays of the southern chinese loess plateau these clays are also sensitive key strata controlling the development of large scale landslides along the slope of the loess tableland surrounding the guanzhong basin to investigate the neogene clay types and landslides in the region soil samples were tested and the macro and micro structures of the clay strata were analyzed comprehensive analysis methods including the pipette method and fine x ray diffraction were applied to quantitatively analyze the sample composition and determine the clay mineral types the neogene clays are mainly composed of illite and montmorillonite mixed layer minerals on the williams discrimination diagram of swelling potential both types of clay are medium to strongly expansive soil two case studies illustrate that rainfall reduces the shear strength of the neogene clay and raises the groundwater level rainfall has gradually destroyed the structure of the neogene clay transforming it to sliding belt soil the sliding belt lies mainly within the neogene clay layers significantly affecting the occurrence and characteristics of landslides in baoji the rise in groundwater level and weakening of the shear strength of the neogene clay are important factors in the occurrence of landslides the long term strength is a key factor affecting the development of loess landslides along the loess tableland in baoji

gravity erosion on the steep loess slope behavior trigger and sensitivity abstract gravity erosion is a dominant geomorphic process on the widespread steep loess slopes yet it is not well understood due to the complexity of failure occurrence and behavior this study conducted a series of experiments in the laboratory to test the stability of different slope geometries and rainfalls and then performed a sensitivity analysis to quantitatively explore the triggering mechanisms of mass failure on the steep loess slope a topography meter designed by the authors was used to quantitatively measure the process of gravity erosion and the increase rate analysis method presented by the authors was also used to analyze the sensitivity of gravity erosion the following three types of gravity erosion were observed landslide avalanche and mudslide in an event of rainfall various types of gravity erosion might emerge in the same period and mass failures with the same mode and similar size often adjacently appeared sometimes a group of mass failures might happen on a large slowly slipping block then the increase rate analysis method was used to evaluate variations in the gravity erosion with respect to changes in other causal parameters of rainfall duration intensity and slope height gradient climate driven factors and topography triggers had prominent influences on gravity erosion whether for the total amount or the peak amount in an experiment the largest sensitivity parameter on both landslides and mudslides was that of rainfall duration in comparison topography was relatively less influential for the total amount in an experiment the sensitivity parameters of rainfall duration on the landslide and mudslide were 24 9 and 19 5 respectively while the sensitivity parameter of rainfall intensity on the avalanche was 2 2 for the peak amount in an experiment the sensitivity parameter of rainfall duration on the landslide and mudslide were 5 5 and 15 6 respectively meanwhile the sensitivity parameter of slope gradient on the avalanche was 4 6 the experimental results obtained here provide an insight into the pre failure mechanisms and processes of steep loess slopes

shear strength characteristics of a residual soil shallow landslides in natural residual soils slopes are common all over the world the slip surfaces associated with these landslides are often situated above the groundwater table therefore it i

detrital composition of ordovician sandstones from the rugen boreholes implications for the evolution of the tornquist ocean the lower palaeozoic sequences of the rugen boreholes are composed of pelitic clastic sediments which range in age from the cambro ordovician boundary to the late ordovician provenance studies have been carried out on cambro ordovician sandstones from the loissin borehole and on middle upper ordovician greywackes of the rugen 5 borehole

hydraulic fracturing controlled dynamics of microseismic clouds 1 several dynamic processes related to propagation of hydraulic fracture modify the stress state in rocks and therefore they are relevant for triggering of microseismicity for instance these are the creation of a new fracture volume fracturing fluid loss and its infiltration into reservoir rocks as well as diffusion of the injection pressure into the pore space of surrounding rocks and inside the fracture using real data we show that some of these processes can be seen from features of spatio temporal distributions of the induced microseismicity especially the initial stage of fracture volume opening as well as the back front of the induced seismicity starting to propagate after termination of the fluid injection can be well identified and used for reservoir engineering

provenance signatures for the miocene volcaniclastic succession of the tufiti di tusa formation southern apennines italy the tufiti di tusa formation a siliciclastic turbidite system of lower miocene age in southern italy is mainly composed of volcaniclastic and quartzolithic sandstones interbedded with mudrocks sandstones are subdivided into four distinctive petrofacies evolving from quartzolithic to volcaniclastic lithofeldspathic and feldspatholithic reflecting detrital evolution from growing orogen quartzolithic petrofacies to active volcanism volcaniclastic petrofacies the mineralogical composition of the associated mudrocks is predominantly characterized by phyllosilicates mainly illite smectite mixed layers i s r1 associated with minor amounts of i s r0 in the lower part of the succession and i s r3 in its upper part together with illite detrital micas and chlorite and minor amounts of chlorite smectite mixed layers and kaolinite in addition to quartz calcite and feldspars the most abundant phyllosilicates are i s mixed layers 10 a minerals illite and micas and chlorite while kaolinite and chlorite smectite mixed layers are present as a few per cent or in trace amounts x ray diffraction patterns show the occurrence of the ordered i s r1 mixed layers in most samples but at the top of the succession some samples are characterized by i s r3 mixed layers whilst in the lower part of the succession i s r1 is associated with a lower amount of i s r0 these features suggest that the tufiti di tusa formation experienced a medium diagenetic grade and the occurrence of i s r3 could be explained by k availability in samples in the upper part of the succession the lithic fragments in sandstones are metasedimentary rocks of palaeozoic age and andesite to dacite volcanic rocks of early miocene age the associated mudrocks also contain trace element ratios cr v y ni la sc th sc th co th cr cr th and eu eu consistent with a provenance containing intermediate to silicic sources with scarce or absent basic rocks the chemical index of alteration 63 2 to 71 6 suggests a moderate degree of weathering in the source furthermore the k cs ratios of sediments confirm likely moderate rather than intense weathering the index of compositional variability icv values from 1 2 to 2 5 are high enough to suggest the mudrocks are first cycle sediments with little recycling the al ti zr diagram and the th sc v zr sc plot indicate poor sorting and rapid deposition of the sediments detrital and sedimentary evolution of the tufiti di tusa formation provides constraints in terms of relations between a growing orogenic system and active volcanism in the central mediterranean to contribute to geodynamic and palaeogeographic reconstructions of the earliest collision in the southern apennines region

laboratory study on soil behavior in loess slope subjected to infiltration abstract in recent years heifangtai plateau in gansu province china has received significant attention as a loess region in which landslides frequently occur this study aims to examine the soil behavior and failure mechanism s of loess slopes subjected to water infiltration high quality samples were retrieved behind the failure plane of a landslide in heifangtai three sets of stress path tests were conducted to mimic the process of loess slope failures these tests include undrained compression on anisotropically consolidated saturated samples drained shear by decreasing mean effective stress at constant axial load on saturated samples and wetting by decreasing matric suction at constant axial load on unsaturated samples loess behavior was evaluated in terms of shear strength deformation upon shearing critical state state parameter and soil water characteristic curve three major observations were drawn from the test results first the anisotropically consolidated saturated loess exhibits a noticeable strain softening behavior upon undrained compression the peak shear strength is mobilized at less than 1 axial strain the ultimate shear strength is only 20 30 of the peak value second when subjected to shear by decreasing mean effective stress at constant axial load the saturated loess exhibits sudden failure when the confining stress is low at higher stresses the soil exhibits progressive failure third unsaturated loess deforms progressively when subjected to a reduction in matric suction i e wetting at constant axial load the failure mechanisms of the loess slopes are discussed based on the experimental findings

early paleozoic rifting and bimodal volcanism in the ossa morena zone of south west spain lower paleozoic volcanic members have been investigated by geological petrographical and geochemical means in a traverse across the ossa morena zone omz in south west spain

problems in predicting the mobility of slow moving landslides abstract this paper discusses problems in predicting the mobility of slow moving landslides three case studies are presented here where research has been carried out by the utrecht university the la valette landslide complex in the french alps the la mure landslide in the french pre alps near grenoble and the hau landslide in switzerland to predict field velocities of these slow moving landslides the viscosity parameters of the material of these landslides were determined by strain controlled tests in a ring shear apparatus based on bishop s design at utrecht university the viscosity parameters from the laboratory proved to be 10 to 1000 times lower than viscosities obtained from back analyses on the observed velocities in the field this discrepancy may be explained by the development of negative pore pressures when the plastic material slides over a rigid wavy slip surface and or by convergent flow effects the associated gain in strength results in a higher apparent viscosity a more detailed analysis is made for the movements of the la valette landslide observed velocities at the la valette landslide are difficult to describe by one parameter set as the response to a change in groundwater level is not the same during a rise or fall in the piezometric level this deviation may be explained by rapid changes in total stresses and consequently changes in pore pressure under partly undrained conditions the emerging hysteresis with local and temporal variations in pore pressure makes it difficult to predict in detail the moving pattern of landslides

baltica and gondwana derived sediments in the mid german crystalline rise central europe implications for the closure of the rheic ocean abstract combined u pb and lu hf isotope analysis of detrital zircons reveals that the mid german crystalline rise mgcr contains palaeozoic sediments of distinct provenance in close proximity zircons from a metapelite of the brotterode group were derived from a gondwanan source whereas zircons from the rogis quartzite of the ruhla group point to provenance from baltica brotterode zircons mostly yield ages of 500 720 ma and 2 0 2 1 ga and show an age gap between 1 0 and 1 7 ga which is characteristic of gondwana peri gondwanan detrital zircon populations combined u pb and hf isotope data suggest intense crustal recycling at 2 6 2 9 ga 1 8 2 1 ga and 570 720 ma as well as formation of juvenile crust during the latter two periods in contrast zircons of the rogis quartzite mostly yield ages between 0 9 and 1 8 ga which are typical of southwestern baltica minor age populations at 435 466 and 550 660 ma indicate that the quartzite is younger than late ordovician early silurian and that the baltica derived sediment is contaminated by minor peri gondwanan perhaps avalonia derived detritus minor age populations at 2 0 2 56 2 67 and 2 86 ga additionally point to a svecofennian and or karelian source u pb and hf isotope data imply that the baltica derived zircons were produced mainly through melting of juvenile palaeo to mesoproterozoic crust the data presented here indicate that the mgcr hosts the rheic suture between gondwana and balonia and that this suture zone was closed in a complex sequence of stages from the late silurian onwards

palaeogeography and tectonic structure of allochthonous units in the german part of the rheno hercynian belt central european variscides new information on palaeogeography orogenic evolution tectonic structure and boundaries of allochthonous units in the rheno hercynian belt is based on provenance analyses of clastic sediments and field studies 40k 40ar dating of detrital muscovites proved to be a particularly useful method because cadomian caledonian and early variscan provenances of detrital material can be distinguished cadomian muscovite cooling ages are restricted to allochthonous units whereas caledonian ages dominate within par autochthonous and shortly displaced allochthonous units the largest and uppermost preserved nappe the giesen harz nappe is derived from an oceanic flysch basin which was not reached by caledonian detritus the other allochthonous units form a duplex like structure sandwiched between the giesen harz nappe and par autochthonous units at its base the thick and heterogeneous roof and floor thrusts of this structure were previously often misinterpreted as olistostromes the northern margin of allochthonous units is the steeply dipping horre gommern zone it consists of three sub units derived from deep water areas between the shelf at the southern margin of the old red sandstone continent and an oceanic basin to the south the southeastern part of the duplex structure harzgerode zone shows close affinities to armorican terranes

detrital spinels from alpinotype source rocks in middle devonian sediments of the rhenish massif middle devonian sandy siltstones of the gummersbach area rhenish massif show increased cr contents up to 675 ppm the chromium is mainly associated with detrital cr al spinels the spinels are characterized by a wide spectrum of chemical composition in more than 50 of 134 analyzed spinel grains the cr2o3 content exceeds 50 wt the a12o3 content which is negatively correlated to cr2o3 reaches 40 wt the mgo contents are with few exceptions lower than the feo contents both elements are negatively correlated the fe2o3 contents which were calculated from a quarter of the grains rarely exceed 5 wt besides cr al fe mg tio2 contents were determined the chemical composition of the detrital spinels indicates provenance from peridotites of an ophiolite suite provenance analysis shows that the source area of the middle devonian clastic sediments was situated in the north

new detrital zircon age data reveal the location of the rheic suture in the mid german crystalline zone spessart and odenwald crystalline complexes new detrital zircon age data of metasedimentary rocks from the spessart and odenwald basement mid german crystalline zone variscides revealed results which are not compatible with current tectonic models the previously proposed existence of a tectonic window which includes lower plate rhenohercynian rocks within the upper plate saxothuringian zone in the spessart and odenwald basement does not agree with the results of this study this leads to a new course of the rheic suture and therefore a non coherence of the two major fault zones in these complexes the southern spessart crystalline complex accommodates the rheic suture which is most likely explained by a southward displacement of a whole segment of the mid german crystalline zone this displacement might extend over the ruhla crystalline complex a hitherto unknown age spectrum of a unit in the bollsteiner odenwald was found which might indicate a sliver of unidentified material in the variscan collision zone an unknown magmatic age of 350 ma is reported for igneous intrusions in the saxothuringian zone and can be used as an additional indicator to distinguish between laurussia and gondwana related rocks

provenance of late palaeozoic metasediments of the patagonian proto pacific margin southernmost chile and argentina in this provenance study of late palaeozoic metasediments of the eastern andean metamorphic complex eamc along the south patagonian proto pacific margin of gondwana the palaeogeological setting of the continental margin in devonian carboniferous and permian times is reconstructed the study is based on detrital heavy mineral contents chemical compositions of tourmaline grains and whole rock element and nd sr isotopic compositions element and isotopic compositions reveal that devonian carboniferous metaturbidites deposited before the development of a late carboniferous permian magmatic arc along the margin were mainly fed from felsic recycled old continental rocks the last recycling phase involved erosion of metasediments that were exposed in patagonia feeder systems to the basin cut either through epidote rich or garnet rich metasediments in permian time eamc metaturbidites were deposited next to the evolving magmatic arc and were derived from felsic crustal rocks two provenance domains are recognised the metasediments of the northern one are chemically similar to those of the devonian carboniferous metasediments this domain was fed from the metasedimentary host rocks of the magmatic arc the southern domain probably was fed from the arc proper as indicated mainly by the dominance of metaplutonic lithic fragments abundant detrital biotite and the major element composition of the metasediments

careon ophiolite nw spain suprasubduction zone setting for the youngest rheic ocean floor the careon ophiolite galicia nw iberian massif shows lithological and geochemical features suggestive of an origin in a suprasubduction zone setting as with other devonian ophiolites in the european variscan belt it was generated within a contracting rheic ocean this setting and the general absence of large silurian devonian volcanic arcs on both of the rheic ocean margins strongly suggest that this ocean was closed by intraoceanic subduction directed to the north this subduction removed the older normal n mid oceanic ridge basalt morb oceanic lithosphere and gave rise to a limited volume of new suprasubduction zone oceanic lithosphere the careon ophiolite is a key element in understanding the evolution of the rheic ocean which was the main oceanic domain that closed during the paleozoic convergence of gondwana and laurussia preceding the assembly of pangea

characteristics of late quaternary activity along the southern border fault zone of weihe graben basin abstract the weihe graben basin located in the centre of shaanxi china is a tectonic depression on the southern border of ordos massif a subtectonic unit in the sino korean paraplatform in the light of new information exhibited from geological mapping on the scale of 1 50 000 the active history and the feature of the southern border fault zone of weihe graben basin have been researched the fault zone may be subdivided into two segments the piedmont fault of huashan mt in the east sector and the northern border fault of qinling mts in the west sector the research shows that new activity of the piedmont fault of huashan mt is obvious since the late quaternary a great number of relics of earthquake deformation such as the newest fault scarps bedrock fractures loess crevices landslides and mountain creep are distributed along this fault and its two flanks this fault is most likely the causative fault zone of the huaxian great earthquake in 1556 m 8 the analysis of two palaeoseismic profiles shows the earthquake recurrence interval is 2000 2500 years for the huashan mt piedmont fault whereas 2000 4000 years for the northern border fault of qinling mts

occurrence of landsliding on slopes where flowsliding had previously occurred an investigation in a loess platform north west china abstract loess slides in south jingyang platform shaanxi province usually occur on slopes where loess flowslides had previously occurred numerical modeling shows that flowslide occurrence causes conditions that increase shear stress and water content in the subsequent slopes both of these factors move the soil stress states towards its theoretical failure line under these conditions only small increases in water content can cause soil collapse this leads to the backscarps of former flowslides being much more prone to landsliding wetting test results show that the loess can collapse suddenly as the water content gradually increases therefore the wetting process induced by continued irrigation may result in the subsequent slides during constant water content tests of the loess material soil shear strength increases with the development of specimen deformation therefore slide mobilization which may be a relatively slow process is dependent on whether the wetting conditions exist finally a slope evolution model for loess platforms is proposed in this study

protolith ages and timing of deformation in the eastern marginal part of the sveconorwegian orogen southwestern sweden abstract u pb zircon and titanite ages from variably metamorphosed igneous rocks in the eastern marginal part of the sveconorwegian orogen eastern segment north of lake vanern sweden suggest that these rocks belong to the younger c 1 71 1 65 ga igneous suite of the c 1 85 1 65 ga transscandinavian igneous belt tib two porphyritic meta granites and one isotropic monzonite yield u pb zircon ages of 1661 27 1674 7 and 1674 7 ma respectively these ages support earlier interpretations that the eastern segment north of lake vanern contains tectonically reworked tib rocks and that there is no major lithological discontinuity either across the sveconorwegian frontal deformation zone or within the eastern segment igneous brown coloured titanites from five samples yield similar u pb ages as the zircons in contrast colourless and oblate shaped titanites from the western penetratively deformed parts of the eastern segment give concordant ages of 976 4 and 956 6 ma further to the east similar titanite from both a penetratively deformed meta granite and a ductile shear zone within a porphyritic quartz monzonite are strongly discordant close to late sveconorwegian lower intercept ages this type of titanite is interpreted to be syntectonic and formed during the upper greenschist east to amphibolite west facies fabric forming event in the eastern segment since the brown igneous titanites and the zircons share a common igneous origin and the single type of metamorphic titanites are either concordant or strongly discordant towards late sveconorwegian intercept ages it is inferred that no major tectonothermal event occurred between the time of tib emplacement and the late sveconorwegian tectonothermal reworking pre sveconorwegian palaeo to mesoproterozoic deformational and metamorphic events gothian which have been inferred west of and further south within the eastern segment appear to be absent in the northern part of this crustal unit

irrigation induced loess flow failure in heifangtai platform north west china because the construction of dams and hydro electric power stations of liujiaxia and yanguoxia across the yellow river in west gansu province north west china inhabitants in the reservoir areas were resettled in heifangtai loess platform irrigation thus started in 1968 perched water table was significantly raised and resulted in many loess flow failures in the past 30 years this type of landslide was often featured by long runout distance high speed and recurrence laboratory tests along icu and csd stress paths were performed it is shown that the loess has a strong strain softening behavior and instability can occur in drained condition before undrained liquefaction the failure mechanism of loess flow can be interpreted as the following process with increasing perched water table collapse in loess was first triggered in drained condition and led to undrained loading to adjacent soil in the lower saturated part of the loess platform under gravity loading applied by upper dry loess undrained flow failure mobilized eventually

analysis of the causes of large scale loess landslides in baoji china landslide hazards are common in western china understanding the mechanism of landslides in loess covered regions is particularly important for landslide risk assessment a detailed landslide survey including large scale slide drilling and geophysical exploration was carried out at the edge of the loess plateau on the north side of the wei river in china we reconstructed the geomorphological evolution model of the wei river and analyzed slope structures and lithology engineering geologic conditions and active fault properties in the landslide regions were investigated the results showed that paleogeomorphology of the north slope of the river gradually lowered from south to north ancient landforms showed a gradual transition to the south sanmen lake basin from the piedmont alluvial plain during the pliocene to early pleistocene the lake basin in the southern part of the study area gradually retreated and the wei river formed in the early pleistocene the main river flow shifted northward because of neotectonic movement and periodic climate changes until the holocene and then gradually moved southward to produce the current landforms the active wei river fault at the edge of the loess plateau acted as a route of water infiltration weakening the structural planes erosion and rise of the groundwater table caused old occurrence during the late pleistocene and ancient occurrence before the late pleistocene landslides to form on the edge of the plateau along active fractures and interfaces of pliocene sand gravel and clay these were multiple deep seated rotational slides and or multiple perched translational landslides slope stability analysis indicated that the complex landslides that occurred in the loess areas in recent years were closely related to the distribution of water and pliocene clay

undrained shear behavior of loess saturated with different concentrations of sodium chloride solution abstract a series of ring shear tests was conducted on saturated loess to investigate the effects of nacl concentration in pore water and desalinization on the shear behavior under undrained conditions the loess samples were taken from the ground surface of a frequently active landslide in china were saturated by de aired distilled water with different concentrations of nacl and then were sheared undrained after that the samples were retrieved remolded re set into the shear box and re saturated by passing through de aired distilled water such that the samples were desalinized and then were sheared undrained again through comparing the undrained shear behavior the effects of nacl in the pore water and desalinization on the undrained shear behavior of loess were examined the results showed that the variation of nacl concentration in pore water can strongly affect the shear behavior of saturated loess both the peak shear strength and steady state strength increased with increase of nacl concentration until a certain value after which they decreased with further increase of nacl concentration meanwhile the peak shear strength and steady state strength of the desalinized samples recovered to those of the original sample hence the effects of salinization are reversible these findings may be of practical importance to better understand the repeated occurrence of some irrigation induced loess landslides in china

laboratory characterization of rainfall induced loess slope failure loess slopes are widely distributed throughout the northwestern region of china and are prone to slope failure in response to heavy rainfall we undertook three groups of flume experiments in the laboratory to study loess slope dynamics under artificial rainfall conditions additionally a laser scanner was used to observe loess landslide deformation characteristics and failure development a numerical analysis of unsaturated seepage in loess slopes because of rainfall infiltration was performed moisture content pore water pressure and slope deformation were monitored to quantify the relationship between rainfall infiltration and loess slope stability movement of the wetting front near the slope surface was triggered by rainfall and related to rainfall intensity and duration which is consistent with the numerical solution rainfall infiltration increased pore water pressure producing gravity driven landslides we observed that landslide development began with local failure in the toe slope that gradually retreated toward the crown forming a multi sliding displacement and eventually resulting in total slope failure

provenance of upper devonian clastic meta sediments of the bollstein odenwald mid german crystalline zone variscides detrital zircons separated from paragneisses of the northern bollstein odenwald mid german crystalline zone variscides yielded cambrian to upper devonian u pb ages the age of the youngest detrital zircon population 371 3 ma and the lower carboniferous metamorphic overprint indicate an upper devonian depositional age of the paragneiss protolith the age spectra of detrital zircons suggest the latter to be derived from 1 ordovician igneous rocks of the saxothuringian zone 2 a late cadomian magmatic arc tepla barrandian unit and 3 a silurian devonian magmatic arc cadomian igneous activity is also documented by cambrian zircon cores in lower to middle devonian detrital zircons meso and paleoproterozoic detrital zircons which are typical for the old red continent and the rhenohercynian zone are entirely lacking the restricted palaeozoic detrital zircon age spectrum is attributed to a silurian devonian intra arc or trench setting both the lack of mesoproterozoic detrital zircons and the striking similarity of the u pb ages of the detrital zircon obtained from the bollstein odenwald with u pb ages from crystalline rocks of the saxothuringian basement rules out that the bollstein odenwald is forming a tectonic window rhenohercynian lower plate inside the mid german crystalline zone saxothuringian upper plate

pore pressure generation and fluidization in a loess landslide triggered by the 1920 haiyuan earthquake china a case study abstract during the 1920 haiyuan earthquake numerous catastrophic landslides were triggered in the loess area in northwest china we investigated in detail a large example of these landslides referred to as dangjiacha landslide in this paper this landslide originated from a slope of about 20 and the displaced soil mass traveled about 3200 m damming a valley we performed a field survey and found that standing water existed in the landslide area and the loess had high porosity we infer that it was the liquefaction of the water saturated loess layer rather than the suspension of silt in the pore air in the loess that caused the great mobility of this landslide to test this inference we performed undrained triaxial compression and ring shear tests on loess samples to examine the shear behavior of loess saturated by either air or water the test results showed that the water saturated loess soil was highly susceptible to flow liquefaction failure fast shear tests on naturally air dried loess samples revealed that the generated pore air pressure was small under the undrained condition and no significant reduction in the shear resistance was observed implying that air entrapped in the loess was unlikely to be the main contributor to the high mobility of this large scale landslide