isotopic and chemical compositions of bentonites as paleoenvironmental indicators of the cretaceous western interior seaway oxygen and hydrogen isotopic compositions of volcanic ashes extensively deposited in the cenomanian turonian greenhorn and campanian claggett seas of the cretaceous western interior basin are commonly at variance with the isotopic compositions of the seas themselves as inferred from well preserved fossils the 18o values of montmorillonite from bentonite beds in manitoba montana south dakota wyoming colorado kansas oklahoma and new mexico range from 13 to 28 and translate into values for the greenhorn and claggett seas of 14 to 4 at 10 25 c these values are significantly more variable than the 18o values of fossils which translate into values of 8 to 2 for the same seas the discrepancies are attributed to post formational alteration of the bentonites the d values of turonian and campanian bentonites are unusually low at 120 to 110 relative to those to be expected from the respective late greenhorn and claggett seas whereas some samples of the cenomanian x bentonite seem to be in oxygen and hydrogen isotopic equilibrium with the earlier greenhorn sea mg and ca contents of montmorillonite from the bentonites vary regularly with 18o values but not with d values and sem analyses show the presence of neoformed fibrous smectite in bentonites with the highest 18o and mg and ca contents the chemical and isotopic data indicate that the variations in mineralogy and alteration of the bentonites result from widely disparate depositional environments and alteration of smectites by interaction with basinal brines

finite element simulation of a slow moving natural slope in the upper austrian alps using a visco hypoplastic constitutive model abstract a large size creeping natural slope was simulated with the finite element fe method using a visco hypoplastic material model which describes the mechanical behaviour of cohesive soils allowing for viscous effects i e creep relaxation and rate dependence of stiffness first the required material parameters were determined by means of standard geotechnical laboratory tests using representative soil samples taken from the slope then a fe mesh of a slope section was constructed and boundary conditions were established the slope movements were simulated and compared with inclinometer measurements which were available for a period of 16 years the calculation results are in good agreement with the observed velocities a parameter study was carried out in order to assess the influence of slope angle initial void ratio material parameters as well as their spatial distribution

a linear regression framework for predicting subsurface geometries and displacement rates in deep seated slow moving landslides abstract a new numerical integration linear regression tool is used to investigate kinematic behavior in deep seated sliding surface deeper than 3 m mass movements the technique is developed in the context of real inclinometer records and numerical integration using nine inclinometer case histories from four well documented large landslides carrot river montebestia karya village and pietrapertosa axial metric subsurface geometric deformation rates are predicted and compared for four different case studies from the literature a reactivated composite extremely slow earth slide earthflow a reactivated composite extremely slow debris slide rock fall an active composite very slow earth slide earth flow and a reactivated complex slow earth slide earth spread sensitivity analysis based on sliding surface depth to length d l ratios show that the mobility of these slow moving masses is closely dependent on the mode of sliding the results also show that short term and long term dynamics of slow moving landslides can be captured by geometrical patterns because the parameter determined is a geometric property the technique used in the investigation can be applied in new landslide problems independent of local conditions and triggering mechanisms within the confines of the stipulated boundary conditions hence with this framework also unrelated landslide problems can be analyzed and compared as demonstrated herein additionally this approach is useful for two dimensional reconstructions of subsurface displacement and velocity profiles and thus may act as a precursor to detailed field investigation programs warning systems and mitigation projects at minimal costs

the valpola landslide abstract the large valpola landslide which occurred on july 28 1987 in valtellina central alps italy on the eastern slope of mt zandila is described and analyzed the slide which took place after a period of heavy rainfall involved a slope made up of 34 million cubic meters of fractured igneous rock the rock mass detached between the elevations of 2250 and 1700 m above s l and with the characteristics of a rock avalanche fell approximately 800 m devastating the bottom of the valley over a distance of 4 km and killing 27 people the mass movement was due to the reactivation of a paleoslide triggered by the rise of hydrostatic pressure in the fractured rock mass and by deep erosion along the bed of pola creek in order to mitigate the risks connected with slope instabilities comprehensive surveying and prediction methods are necessary monitoring since july 28 1987 has been very successfull in assisting prediction

major risk from rapid large volume landslides in europe eu project runout abstract project runout has investigated methods for reducing the risk from large volume landslides in europe especially those involving rapid rates of emplacement using field data from five test sites bad goisern and kofels in austria tessina and vajont in italy and the barranco de tirajana in gran canaria spain the studies have developed 1 techniques for applying geomorphological investigations and optical remote sensing to map landslides and their evolution 2 analytical numerical and cellular automata models for the emplacement of sturzstroms and debris flows 3 a brittle failure model for forecasting catastrophic slope failure 4 new strategies for integrating large area global positioning system gps arrays with local geodetic monitoring networks 5 methods for raising public awareness of landslide hazards and 6 geographic information system gis based databases for the test areas the results highlight the importance of multidisciplinary studies of landslide hazards combining subjects as diverse as geology and geomorphology remote sensing geodesy fluid dynamics and social profiling they have also identified key goals for an improved understanding of the physical processes that govern landslide collapse and runout as well as for designing strategies for raising public awareness of landslide hazards and for implementing appropriate land management policies for reducing landslide risk

a detachment fold model for fault zones in the late archean abitibi greenstone belt abstract the abitibi belt is one of the largest and most extensively studied late archean greenstone belts the structural geology of the abitibi belt consists of one generation of upright to slightly overturned doubly plunging first order folds with half wavelengths of 20 60 km and e w striking steeply dipping fault zones that are parallel to the fold limbs two of the main fault zones are continuous for hundreds of kilometers previous tectonic models for the abitibi belt interpret the fault zones to have formed as extensional growth faults bounding a volcanic sedimentary basin which were reactivated as thrusts during subsequent crustal shortening other models propose that the fault zones represent tectonic sutures implying that the abitibi belt is a collage of exotic terranes however distinct geological terranes have not been geologically demonstrated we propose a new detachment fold model for the deformational history of the southern abitibi belt in ontario that explains the formation of the fault zones during the single well documented folding event that deformed the entire region the internal structure of the fault zones documented here with emphasis on the porcupine destor fault zone consists of isoclinally folded strongly schistose highly metamorphosed rock cross cut by numerous fault segments we interpret that the upper crust greenstones was folded above a proposed detachment in the lower part of the volcanic stratigraphy the fault zones would be in essence highly evolved detachment anticlines ultramafic metavolcanic rock that crops out within the fault zones would represent material from the detachment horizon that was emplaced in the cores of the detachment anticlines the numerous segments that make up the mapped fault zones would be linked faults that formed within the isoclinal detachment anticlines to accommodate folding of the rheologically complex greenstones the detachment fold model is compared to the results of analogue experiments designed to investigate crustal scale folding using viscous and frictional materials detachment folds are produced in the brittle upper crustal analogue on the limbs of folds formed in the ductile middle and lower crust analogues the experimentally produced structures scale to the structures in the study area and indicate the detachment fold model for the southern abitibi is mechanically viable

discriminant function analysis of late quaternary tephras from five volcanoes in new zealand using glass shard major element chemistry abstract the microprobe determined glass shard major element chemistry of tephras derived from five north island new zealand volcanoes mayor island okataina taupo tongariro and mount egmont and younger than ca 20 000 yr b p was subjected to discriminant function analysis four separate approaches were adopted to test the match of the tephras with their known sources 1 an analysis of raw microprobe data 2 an analysis of normalized data 3 an analysis of the data transformed by calculating the log 10 of oxide scores divided arbitrarily by the chlorine content and 4 a repeat of 3 with multivariate outlier scores as determined by principal components analysis deleted all yielded excellent classification functions efficiencies of 91 100 with the eruptives associated with each of the five volcanoes being chemically distinct from one another in each approach the first two canonical discriminant functions accounted for 90 of the variation between groups the removal of multivariate outliers from the data set had only minor effects on the performance of the discriminant function procedures separate discriminant function analysis of the relatively alike taupo and okataina eruptives gave a greater degree of multivariate separation the numerical classifications generated should enable unidentified tephras erupted since ca 20 000 yr b p from the five volcanoes to be provisionally matched with their sources

down slope variation in geotechnical parameters and pore fluid control on a large scale alpine landslide abstract a geotechnical investigation has been carried out on a large volume landslide in the stambach valley on the slopes above the town of bad goisern austria undrained loading has been considered as a means of triggering a large volume debris flow the initiation of this landslide has been linked with the collapse of rock pillars from the rock face of zwerchwand onto the head of the flow the concept of pore tensions resulting from stress relief has been used to account for the time delays of up to 10 months between the loading and the reactivation of the debris flow

the cretaceous polar and western interior seas paleoenvironmental history and paleoceanographic linkages abstract this study reviews the cretaceous histories of the polar and western interior seas as recorded in the canadian high arctic sverdrup basin beaufort mackenzie basin of northwest canada and western canadian foreland basin newly emerging stratigraphic paleoclimatic and paleoenvironmental interpretations from the polar realm allow for a fresh look at the response of this oceanic system to global climatic trends and sea level histories over 35 ma sverdrup basin localities on axel heiberg and ellef ringnes islands represent shelf to slope environments that contrasted with the shallow water and low gradient settings of the canadian western interior sea both marine systems connected throughout aptian to maastrichtian time responded to global transgressive regressive cycles resulting in dynamic paleogeographic changes the upper aptian to campanian succession of the polar sea shows at least two unconformable boundaries one at the albian cenomanian transition and another within the upper cenomanian the shallow basin setting and in particular the forebulge and backbulge settings of the western canadian foreland basin are characterized by multiple erosional surfaces throughout the cretaceous succession the upper albian disconformity is widely discernible close to the entrance of the western interior sea to the polar sea this suggests a short lived closure of the latest albian mowry sea that might have been responsible for the large loss of benthic foraminiferal species at this time several oceanic anoxic events are documented in these basins representing their response to global climate dynamics during the late cretaceous temperature maximum benthic foraminiferal communities were severely restricted by bottom water hypoxia in both basins a stratified water column might have been the result of increased freshwater runoff under warm humid conditions these conditions supported vegetation up into the polar latitudes that added abundant organic matter to marine shelf systems conversely the canadian western interior sea biotic communities were controlled by watermasses of two or maybe three different sources and physical properties including the polar tethyan and a possibly third source from the emerging labrador sea through the hudson seaway where the southern and northern watermasses mixed plankton might have been influenced by oceanic fronts forming mass kills through sinking of dense waters migration of calcareous phyto and zooplankton was controlled by a temperature and salinity gradient and did not invade northern regions siliceous plankton occurred and is more commonly found in the sverdrup basin but taphonomic loss through deep burial needs to be taken into account

debris flow triggering by impulsive loading mechanical modelling and case studies a mechanism is proposed by which debris flows can be triggered through impulsive loading momentum transferred from hillslope failures to steep stream bed materials may be sufficient to initiate a

exhaustion and steady state models for predicting landslide hazards in the canadian rocky mountains abstract the temporal distribution of landslides can be evaluated by steady state and exhaustion models the probability of landsliding remains constant through time in the steady state model but the probability decreases in the exhaustion model as more slopes fail rock sliding down bedding surfaces on overdip slopes exhausts hazardous sites to leave stable dipslope landforms in kananaskis country in the canadian rocky mountains the distribution of rock slides in this area can be better explained by the exhaustion model than by the steady state model

the structural evolution of the missanabie renabie gold district pre orogenic veins in an orogenic gold setting and their influence on the formation of hybrid deposits

geometry of upper cretaceous bentonite beds implications about volcanic source areas and paleowind patterns western interior united states four bentonite beds near the cenomanian turonian stage boundary ca 90 ma can be traced through much of the western interior of the united states isopach maps constructed for these bentonite beds indicate that volcanic source areas were positioned both northwest and southwest of the central u s western interior basin and also indicate both easterly and southeasterly paleowind directions volcanism of this age has not been reported previously in the southern source area

gold bearing fault zones related to late archean orogenic folding of upper and middle crust in the abitibi granite greenstone belt ontario abstract this work investigates the structures of the abitibi granite greenstone belt ontario with a focus on regional scale folds and on regional scale auriferous fault zones the folds and the fault zones resulted from late archean orogenesis the analysis is based on studies of surface geology and on modelling of the gravity field amphibolite grade orthogneiss was involved in the regional folding that also deformed the overlying greenstones folding resulted in uplift of the orthogneiss that preserves the metamorphic mineral assemblage ferropargasite garnet biotite andesine quartz geothermobarometric calculations indicate recrystallization of a metatonalite sample under peak paleopressures of 7 0 1 2 to 7 9 1 1 kb providing evidence that folding involved crust to depths of at least 18 25 km the regional bouger anomaly map reveals previously unrecognized first order folds interpretation of the bouger anomaly map also confirms that granitic batholiths are hosted by anticlines a wavelet based inversion method was used to determine the locations orientations and continuations at depth of the maxima of density contrasts the maximum density contrasts correspond to steeply dipping geological contacts on the limbs of the open to tight regional scale folds regional scale fault zones only have prominent gravity signatures where they correspond to sheared rocks on the limbs of folds modelled gravity profiles were used to produce profiles that visualize the shapes of batholiths and greenstone bodies within the present day upper crust the granitic batholiths have tabular shapes which are locally folded with preserved main body thicknesses of 1 3 km the greenstones form keels corresponding to synclines some of which reach 5 6 km depth the results of this study confirm that the principal deformational response of the abitibi granite greenstone belt to late archean collisional tectonics was large half wavelength 10 40 km folding of the upper and middle crust our results and interpretations also strongly suggest the regional scale fault zones which are loci for orogenic gold deposits are fold related structures they represent quasi continuous lineaments of shearing and faulting on the limbs of regional folds and locally in the cores of detachment anticlines as shown in a previous paper

k bentonites a review pyroclastic material in the form of altered volcanic ash or tephra has been reported and described from one or more stratigraphic units from the proterozoic to the tertiary this altered tephra variously called bentonite or k bentonite or tonstein depending on the degree of alteration and chemical composition is often linked to large explosive volcanic eruptions that have occurred repeatedly in the past k bentonite and bentonite layers are the key components of a larger group of altered tephras that are useful for stratigraphic correlation and for interpreting the geodynamic evolution of our planet bentonites generally form by diagenetic or hydrothermal alteration under the influence of fluids with high mg content and that leach alkali elements smectite composition is partly controlled by parent rock chemistry studies have shown that k bentonites often display variations in layer charge and mixed layer clay ratios and that these correlate with physical properties and diagenetic history the following is a review of known k bentonite and related occurrences of altered tephra throughout the timescale from precambrian to cenozoic

geochemical relationships in cretaceous bentonites as inferred from linear discriminant analysis abstract bentonites serve as an important stratigraphic tool for facies correlation due to their instantaneous deposition and preservation across multiple depositional environments correlating one bed to another can be a complex issue limited by the 3 dimensional availability of outcrops and core this process is reliant on the assumption that the geochemical signatures of ash beds do not vary enough to statistically alter the correlation coefficients that tie one ash fall to another this assumption may be faulty however and the problem compounds as bentonite bed thickness increases because the chemical composition varies through an eruption due to stratification of the magma chamber and through physical transport linear discriminant analysis lda can significantly aid with this issue allowing for the utilization of a multivariate dataset to statistically separate chemically similar groups here we present a statistical approach to assessing the primary discriminatory variables on a suite of 87 cretaceous bentonites deposited in the bighorn basin wyoming usa that span five geologic stages and seven formations from the cloverly formation 110 ma to the meeteetse formation 70 ma and includes nine named ash beds using lda bentonites were sorted into groups based on geologic stage formation and unique beds using key elemental concentrations and radiogenic isotopes e g 87sr 86sr tio2 sc na and th additionally distinct similarities in the discrimination pattern between formations reveal two periods of magmatism the development of the idaho batholith and the migration and development of the boulder batholith and surrounding related plutons with well preserved temporally constrained ash lda can correlate ancient tephra deposits while also shedding light on the cyclical nature of geochemical trends in a migrating subduction zone

analysis of the wallowa baker terrane boundary implications for tectonic accretion in the blue mountains province northeastern oregon the baker terrane exposed in the blue mountains province of northeastern oregon is a long lived ancient late paleozoic early mesozoic accretionary complex with an associated forearc this composite terrane lies between the partially coeval wallowa and olds ferry island arc terranes the northern margin of the baker terrane is a broad zone 25 km wide of fault bounded imbricated slabs and slices of meta igneous and metasedimentary rocks faulted into chert argillite melange of the elkhorn ridge argillite metaplutonic rocks within tectonic units in this zone crystallized between 231 and 226 ma and have low initial 87 sr 86 sr ratios 0 7033 0 7034 and positive initial e nd values 7 7 to 8 5 in contrast siliceous argillites from the chert argillite melange have initial 87 sr 86 sr values ranging from 0 7073 to 0 7094 and initial e nd values between 4 7 and 7 8 we interpret this broad imbricate fault zone as a fundamental tectonic boundary that separates the distal wallowa island arc terrane from the baker accretionary complex terrane we propose that this terrane boundary is an example of a broad zone of imbrication made up of slabs and slices of arc crust tectonically mixed within an accretionary complex providing an on land ancient analogue to the actualistic arc arc collisional zone developed along the margins of the molucca sea of the central equatorial indo pacific region

the slope movements within the mondores graben drome france the interaction between geology hydrology and typology the mondores graben in the south eastern french alps is an uncommon structural feature which originates in a complex polyphasic tectonic evolution in contrast with its immediate surroundings with hardly any huge landslides the mondores graben is characterised by various types of landslides a huge sagging caused part of the limestone cliff to subside some 50 m within 50 years two recent mud flows that occurred were considered a potential threat to some inhabited places downstream the hydrologic aspects of the boulc mondores landslide resemble the geology infiltration and karst input in the rock sliding zone and exfiltration in the marls resulting in slumps and mud flows the mass movement interactions could be explained by a structural geology analysis with geodetic monitoring using different techniques it is also shown that hydrochemistry as well as geophysical surveys are of importance in unravelling the hydrologic systems and the geological subsurface structures the present paper aims at explaining the geological control of the different slides in view of estimating their potential danger understanding the geological structure and its evolution therefore is a necessary prerequisite

rheology of some continental lower crustal rocks abstract to gain insight into the rheology of selected feldspar bearing rocks from the continental lower crust clc three granulites from exposed lower crustal terrains and a microgabbro have been deformed to ca 10 strain at confining pressures of 0 8 1 0 gpa temperatures of 600 900 c and constant strain rates of 10 4 10 7 s 1 the most extensive work was done on the mafic pikwitonei and felsic adirondack granulites the pikwitonei mg hornblende plag an70 2 px has only a limited t range of apparent steady state behavior and strain softens at t 800 c at 10 5 10 6s 1 apparently associated with developing shear zones this strain softening is pressure insensitive from pc 0 8 1 0 gpa at t 850 c 10 6s 1 even though the dominant strain accommodation mechanisms change from semibrittle cataclastic to crystal plastic including dynamic recrystallization with increasing pressure plagioclase appears to bear more of the creep strain than amphibole at most experimental conditions except in those runs where both plagioclase and amphibole recrystallization occurs kapuskasing plag cpx gt granulite deformed at 800 c and at 850 c 10 6 s 1 has deformed in the steady state at stress levels only slightly greater than the pikwitonei the stillwater microgabbro and adirondack granulite are appreciably weaker and the latter exhibits homogeneous semibrittle steady state behavior over the entire range of conditions investigated for the adirondack 2 felds 2 px gt qtz granulite quartz 21 appears to control the creep rate at these low strains and steady state mechanical data fit well a creep power law with a 8 10 3 mpa ns 1 qc 243 kj mol and n 3 1 extrapolation of this flow law and of preliminary power law creep relations for the pikwitonei and microgabbro to a range of physical conditions assumed to encompass those at the continental moho supports geological and geophysical inferences that a mechanical discontinuity occurs at this transition zone with the lower crust generally being the weaker material in addition the stain softening exhibited by the pikwitonei may bear directly on the development of detachment zones at mid to lower crustal depths during prograde metamorphism

structural control and types of movements of rock mass in anisotropic rocks case studies in the polish flysch carpathians abstract types of gravitational movements in the flysch carpathians are related to tectonic and lithologic anisotropy of rock massifs this article presents the main types of mass movements in the highly anisotropic flysch massifs lateral spreading and rock flow topple translational rotational and compound sliding and complex type of mass movements which are illustrated by chosen forms described using structural analysis joints faults and other structural planes orientation topple is the typical mass movement for double ridges and top trenches e g gaworzyna in the beskid s decki mts translational landslides with flat structural sliding surfaces typical for shallow forms can develop along bedding planes e g duszatyn western bieszczady mts as well as along joints opuszna gorce mts and fault planes rzeki gorce mts currently used classification of the structural landslides is applied only to translational landslides shearing zones of deep seated landslides are composed of structural sections of joints faults bedding planes and shearing elements consequently most of the carpathian landslides have developed as compound type with non circular sliding zones representing complex movements combined with various types of displacement rotation translation and or topple purely rotational movements with circular failure typical for isotropic material have developed in the flysch where thick bedded hard sandstones are underlain by plastic shales e g mt kostrza in the beskid wyspowy mts the influence of anisotropy of these rocks on sliding surface is significantly reduced and plastic type rocks stimulate rock flow development which is usually later transformed into complex landslides with predominant rotational movement e g rotational landslide with topple and flow elements on mt muronka in the beskid l ski mts compound landsliding on mt lubon wielki beskid wyspowy mts represents an antithetic rotational slide with topple and rotational type movements

the mechanics of deep seated landslides results are presented of a sequence of laboratory tests undertaken to elucidate the behaviour of deep seated landslides in deep seated failures deformation has been reported at depths of up to 250 m in the movement zone owing to the weight of the overburden and the surrounding stress environment conventional soil mechanics cannot be used to explain effectively associations between the landslip activity and the deformation mechanisms operating within the moving mass a series of experiments has been undertaken on london clay using a high pressure servohydraulically controlled triaxial deformation system to replicate the stresses acting at the base of a large deep seated landslide a number of tests were undertaken the most significant focusing on the transition between ductile and brittle behaviour although sediments usually behave in a brittle manner at low effective stresses common to many geomorphological studies and in a ductile manner at high effective stresses the results presented here identify for the first time in mudrocks a transitional phase of behaviour in which creep like movement will manifest itself at the base of a deep seated landslide as the growth of microcracks the microcracks may eventually coalesce to form a shear surface a consequence of which is likely to be sudden failure the results thus have important implications in the understanding of movement mechanisms in large deep seated failures rates of displacement and how they may change through time 1997 by john wiley sons ltd

fallout and distribution of volcanic ash over argentina following the may 2008 explosive eruption of chaiten chile 1 the major explosive eruption of chaiten volcano chile in may 2008 provided a rare opportunity to track the long range dispersal and deposition of fine volcanic ash the eruption followed 10 000 years of quiescence was the largest explosive eruption globally since hudson chile in 1991 and was the first explosive rhyolitic eruption since novarupta alaska in 1912 field examination of distal ashfall indicates that 1 6 1011 kg of ash dense rock equivalent volume of 0 07 km3 was deposited over 2 105 km2 of argentina during the first week of eruption the minimum eruption magnitude estimated from the mass of the tephra deposit is 4 2 several discrete ashfall units are identifiable from their distribution and grain size characteristics with more energetic phases showing a bimodal size distribution and evidence of cloud aggregation processes ash chemistry was uniform throughout the early stages of eruption and is consistent with magma storage prior to eruption at depths of 3 6 km deposition of ash over a continental region allowed the tracking of eruption development and demonstrates the potential complexity of tephra dispersal from a single eruption which in this case comprised several phases over a week long period of intense activity

modelling stability and surging in accumulation slides abstract an idealized model for certain classes of debris flows and avalanches is developed slopes characterized by a steep feeder segment which loads a flatter accumulation segment will be focused on such slopes have been observed to exhibit episodic surging motions the simplified model allows considerable insight into the behavior of such slides an approximate stability criterion is derived explaining the surging motions it is shown that in general one cannot predict the onset of surging due to the inability to precisely characterize the interaction between the feeder and accumulation slopes other results include an approximate analysis for the mean acceleration which may occur during surging

critical evaluation of six tectonic setting discrimination diagrams using geochemical data of neogene sediments from known tectonic settings abstract an attempt is made to evaluate 6 tectonic setting discrimination diagrams 1 discriminant function and 5 bivariate diagrams frequently used by many researchers for this purpose an extensive database was established for major element geochemistry derived from miocene to recent sand and sandstone medium to fine grained samples collected from a variety of tectonic settings including 1 passive margin pm setting 2 active continental margin acm setting and 3 oceanic island arc oia setting our results suggest that the discrimination fields proposed to infer tectonic settings for six commonly used discrimination diagrams do not work properly for the analyzed miocene to recent sediments the success for these diagrams varies from 0 to about 62 we therefore recommend that these diagrams be used with prudence

high initial sr isotopic ratios and evidence for magma mixing in the pioneer batholith of southwest montana the northeast part of the composite pioneer batholith of southwest montana consists of late cretaceous calc alkaline plutons that vary in composition as a function of age changing from minor hornblende biotite quartz diorite at about 76 m y to a small pluton of hornblende biotite tonalite at about 74 m y to abundant biotite hornblende granodiorite and biotite granite at about 72 m y to some biotite granodiorite and 2 mica granite at 67 to 65 m y initial 87 sr 86 sr ratios sirs for the plutons range from 0 7112 to 0 7160 magmas having a sir near 0 7112 appear in most episodes of emplacement whereas those having higher values are restricted to individual episodes two granodiorite plutons of 72 m y age show a mutual gradational contact across which the sir varies over a distance of 7 km from 0 711 to 0 714 the variation is ascribed to mixing between contemporaneous but isotopically distinct granodiorite magmas the high sirs of the batholith are interpreted as reflecting partial melting

kinematics and geological constraints of the slow moving pisciotta rock slide southern italy abstract the pisciotta landslide is a slow moving deep seated rock slide in the campania region of southern italy which has damaged a provincial road several times in the last decades and currently poses a hazard to the national railway that intersects the toe of the landslide the landslide involves an oligocene turbidite series which is composed of intercalated calcarenites marls and mudrocks the principal objectives of this study were to investigate the morphological evolution of the unstable slope quantitatively analyse ground deformations and construct an engineering geological model that is consistent with the spatial features of the landslide the long term evolution of the unstable slope was assessed through the examination of available aerial photos from 1943 to 2006 kinematic analyses of the ground deformations were conducted based on observed progressive displacement of the road as evident from the topographic maps and orthophotos 1955 2006 and the bi weekly displacement survey of 50 targets distributed across the landslide area september 2006 march 2009 the engineering geological model of the landslide was reconstructed from the stratigraphic data obtained from the study of borehole data and monitoring of inclinometers as well as from geological structural and geophysical surveys the analysis of the aerial photographs revealed an early stage of deformation in 1943 which has been gradually widening since then in addition to the main scarp and the landslide flanks other significant landslide structures such as the longitudinal and transverse cracks as well as the positive or negative morphologies were monitored and mapped in the subsequent years these studies indicated a progressive erosion of the upper part of the slope and a bulging of the foot long term kinematic analysis based on the progressive displacements of the road allowed the measurement of the ground deformations from 1955 to 2009 which revealed a cumulative horizontal displacement of up to 53 m and an average velocity of 0 98 m year 1 which has increased in the recent decades in addition the recent monitoring of the ground deformations demonstrated a continuous activity with an approximately constant rate of displacement and a composite kinematic history of the landslide body through differential displacements and associated velocities the engineering geological model of the landslide was found to be controlled by specific stratigraphic and structural constraints the landslide involves a stratigraphic interval of the saraceno formation nord calabrese tectonic unit with a largely marly argillaceous composition whose structural setting displays complex folding at the mesoscale and faulting with an approximately monocline attitude of bedding and a downslope dip direction at the macroscale the left flank of the landslide rests on a normal fault

temporal behavior of deep seated gravitational slope deformations a review abstract deep seated gravitational slope deformations dsgsds are slow moving hillslope scale mass movements featuring characteristic landforms such as double crested ridges and upslope facing scarps that occur in diverse landscapes throughout the world although these deformations have been studied since the 1960s significant insights to the rates of dsgsds have only been gained within the last two decades owing to progress in geochronology remote sensing and instrumental monitoring absolute age and monitoring data indicate that dsgsd movements are observable over long term 102 years and short term future research directions include constraining the lifespan of dsgsds with absolute age dating and precise high resolution monitoring of spatio temporal displacement across dsgsd bodies it is of great importance to include absolute time scales in the numerical models of dsgsds furthermore combining remote sensing techniques such as synthetic aperture radar interferometry with high resolution lidar scanning and near surface geophysics offers a promising toolkit for collecting very detailed and accurate data on the short term deformation rates of dsgsds

dynamic earth system and ecological controls of rainfall initiated landslides abstract rainfall initiated landslides continue to inflict damages and loss of life throughout the world processes and mechanisms revealed from hydrological geomorphic geotechnical pedological geological hydrochemical and biological investigations have advanced our understanding of these effects on slope stability however the interactions amongst these processes and attributes as they affect the initiation and propagation of landslides are not as well understood too often landslide studies are conducted from only one or at most two of these perspectives moreover while precipitation and hydrology are recognized as dynamic influences the earth system and ecological effects are often assumed to be static we assess the interplay of these processes related to landslides triggered by positive pore water accretion and loss of soil suction each of these conditions arguably requires a different view on the processes that cause slope failure and predictive approaches this review starts from the perspective of dynamic adapting earth and ecological systems and discusses how these attributes relate to landslide initiation mode location and timing specifically the role that large and small scale preferential flow plays in both contributing to and mitigating instability is elucidated including effects of bedrock exfiltration we also examine how and under what conditions these pathways manifest in different soils lithology and landforms the multiple effects of rhizosphere processes on slope stability are discussed including root reinforcement evaporation from canopies and litter layers transpiration and the role of root structure affecting preferential flow paths rainfall initiated landslides involve highly dynamic hydrologic earth surface and ecological processes that persist over a range of spatial and temporal scales however guidance for overcoming these challenges has been elusive a conceptual framework is presented to shed light on these dynamic and interactive processes that should lend insights into why and when certain slopes fail during storms while other seemingly similar slopes do not fail such advances will benefit landslide hazard assessments and disaster responsiveness protocols

evolution stages of large deep seated landslides at the front of a subalpine meridional chain maritime alps france abstract studying long term evolution of gravitational slope evolution is a key to understanding deep seated landslide processes this paper deals with three large deep seated landslides dsls at a front of a subalpine meridional chain on the la marbriere slope near the town of grasse alpes maritimes france the geological framework controlling the stability and morphology of the dsls is associated with thick and tamped triassic layers of mudstone with gypsum overlain by highly faulted jurassic limestone gravitational deformation affects the entire slope involving a movement of about 1 1 10 8 m 3 of rock material it creates large disturbances in landscape morphology such as scarps counter slope scarps trenches and other typical gravitational morpho structures geomorphological mapping coupled with deep electrical resistivity tomography ert reveals a strong correlation between these morpho structures and inherited brittle tectonic features this observation relies on spatial and geometrical relations on the surface and at the depth of more than 150 m checked by ert between the most persistent fault and the gravitational morpho structures the specific distribution of the morpho structures on the basis of their morphological typologies and variations in the stage of evolution of three dsls provides an interpretation of their kinematics during the last 400 ka it appears that soft substratums combined with inherited persistent anisotropies are key factors in the development of the dsls indeed outflow of mudstone due to the lithostatic pressure imposed by individual limestone compartments has led to general slope subsidence then a progressive toppling of a rock mass may have led to the catastrophic rock collapse along bedding planes the evolution of the dsls can be divided into three distinct stages represented by three zones a young collapse stage zone 1 a pre collapse stage zone 2 and an old mature stage 400 ka zone 3 as the dsls occur on the same slope and in the same geological context this area offers interesting perspectives for understanding factors controlling the long term gravitational evolution of slopes

the origin of tonsteins an overview and links with seatearths fireclays and fragmental clay rocks abstract tonsteins are volcanic ash falls in coal bearing sequences that have altered to kaolinite only in the last twenty years or so has the volcanic origin become firmly established the evidence for the volcanic origin encompasses bed form including lateral extent structures textures volcanogenic mineralogy and geochemistry the lines of evidence are reviewed from a historical perspective tonsteins came to prominence over a hundred years ago because of their stratigraphic value tonsteins continue to be of value in coalfield exploration but their stratigraphic value has been enhanced in recent years with the ability to determine radiometric ages with a high level of accuracy the geochemistry not only provides good evidence for the volcanic origin but also enables tectomagmatic deductions to be made for areas external to the coal basin in addition some tonsteins are the indicators for the discovering of rare metal ore deposits nb rees and ga there is also the potential to use the geochemistry to identify specific tonsteins essentially a chemostratigraphic approach tonsteins are seen as one class of bentonites others include k bentonites metatonsteins and possibly illitic bentonites tonsteins have been linked to seatearths fireclays and fragmental clay rocks although all such rocks contain kaolinite the origins differ the seatearths contain rootlets and were subjected to pedogenic activity alteration of the silicate minerals is limited under conditions of a high water table and in the presence of organic matter reducing conditions prevailed leading to gleization on the other hand the fireclays show extensive alteration to kaolinite there is a link with the major marine bands and this has implications in terms of sequence stratigraphy the fragmental clayrocks have also been linked to soil forming processes but in this case possibly the reworked soil was the product of an open system containing free alumina minerals that reacted with silica in solution during diagenesis

slope tectonics a short introduction geomorphology structuralgeologyandengineeringgeology allow description of the main character istics of a slope in distinct ways that can be com bined to provide a complementary view of theoperative slope processes the subjects presentedin this special publication include slope mor phology and evolution mechanical behaviour ofthe material modes of failure and collapse in u ence of lithology and structural features and therole played by controlling factors this slope tec tonics volume comprises a series of very differentcontributions that attempt to underline a multidisci plinary approach thatshould form the framework ofslope instability studies slope tectonics is adopted in this volume tomeandeformationthatisinducedorfullycontrolledbytheslopemorphologyandthatgeneratesfeaturesthatcanbecomparedtotectonicfeatures thestress eld in a slope is the result of gravity topographyand the geological setting created by an ensembleof geodynamic processes active tectonics alsocalled neotectonics generates a stress eld thatcancontrolslopeprocesses astrongfeedbackexist ingbetween geological history tectonics lithology geomorphological evolution and topography as a consequence a list of factors and theirrela tive in uence can be presented 1 fabric induced by a local stress eld within aslope discontinuities and local faults with cata clastic bands of variable thickness folds fig 1 associated predominantlywith brittle structures complex failure paths stepped or multi surface localfailures rockbridgefailuresorexten sional failures graben like or pseudo graben like subsidence due to weak or soluble mate rials causing complex sliding topplingphenomena 2 reactivation of pre existing faults disconti nuities joints foliations or rock anisotropies surfaces characterized by residual or lowerthan peak strength formation of composite failure surfaces 3 regional tectonic movements inducing newslope morphologies uplift major fault movement pull apart zones folding the boundary between classical tectonics andslope deformations especially at a large scale hasalways been indistinct as emphasized by antoine 1988 schultz ela 2001 in his paper antoinediscussed mechanisms like diverticulation def ined by lugeon 1943 and badoux 1963 wherepart of pre alpine nappes were reversed in geo metry by huge landslides inverting the stratigraphy antoine 1988 a remarkable geometrical analogyexists between basin extensional tectonics wer nicke 1981 and certain landslide spreading inclays voight 1973 varnes 1978 hutchinson1988 this is despite the fact that wernicke shypothesis demonstrated that basin and rangeregions were not produced by huge landslides butby low angle faulting induced by geodynamic pro cesses regional extension has produced changesin topography and as a consequence signi cantgravity induced deformations therefore we suggest that the term slope tec tonics is justi ed and must be recognized as animportant component in slope deformation slopeinstability implies movements driven by gravitythat can produce irreversible deformations in thepast slopes were viewed as privileged erosionzones de la noe de margerie 1888 strahler1950 whereas few erosion processes were attribu ted to landslides young 1972 since the work ofsimonett 1967 and hovius et al 1997 the link

residual strength of clays in landslides folded strata and the laboratory the post peak drop in drained shear strength of an overconsolidated clay may be considered as taking place in two stages first at relatively small displacements the strength decreases to the fully softened or critical state value owing to an increase in water content dilatancy second after much larger displacements the strength falls to the residual value owing to reorientation of platy clay minerals parallel to the direction of shearing if the clay fraction is less than about 25 the second stage scarcely comes into operation the clay behaves much like a sand or silt with angles of residual shearing resistance typically greater than 20 degrees conversely when the clay fraction is about 50 residual strength is controlled almost entirely by sliding friction of the clay minerals and further increase in clay fraction has little effect the angles of residual shearing resistance of the three most commonly occurring clay minerals are approximately 15 degrees for kaolinite 10 degrees for illite or clay mica and 5 degrees for montmorillonite when the clay fraction lies between 25 and 50 there is a transitional type of behaviour residual strength being dependent on the percentage of clay particles as well as on their nature the post peak drop in strength of a normally consolidated clay is due only to particle reorientation measurements of strength on natural shear surfaces agree within practical limits of variation with values derived from back analysis of reactivated landslides this field residual strength can be recovered by multiple reversal shear box tests on cut plane samples but in high clay fraction materials it is typically somewhat higher than the strength measured in ring shear tests residual strength is little affected by variation in the slow rates of displacement encountered in reactivated landslides and in the usual laboratory tests but at rates faster than about 100 mm min qualitative changes take place in the pattern of behaviour a substantial gain in strength is followed with increasing displacement by a fall to a minimum value in clays and low clay fraction silts this minimum is not less than the slow or static residual but in clayey silts with clay fractions around 15 25 according to tests currently in progress the minimum can be as low as one half of the static value author trrl

large rock slope failures in the highlands of scotland characterisation causes and spatial distribution abstract a comprehensive database of larger rock slope failures rsfs has been compiled and characterised for a whole mountain range possibly for the first time apart from iceland most rsfs in the scottish highlands occurred soon after deglaciation a threshold size of 0 25 km 2 focuses on rsfs which contribute significantly to gross erosion in the glacial paraglacial cycle and on the spatial concentration of this poorly recognised process database verification indicates that at least 90 of the total extant population in the highlands is covered standard mass movement typologies are broadly applicable but require some refinement to characterise rsfs in a passive margin glaciated mountain range comprised mainly of ancient metasediments most larger rsfs here are complex and difficult to categorise a continuum from cataclasmic failures including rock avalanches through arrested translational slides to almost in situ slope deformations is identified the prevailing modes of large rsf are arrested short travel translational sliding and gravitational sagging cataclasmic failure is rare and sub cataclasmic outcomes are more evident a significant class of deformations exhibits compressional rather than extensional features and may be responding to localised glacio isostatic rebound stresses the large rsf population is widely but very unevenly distributed across the main mountain areas 65 are in seven main clusters with the rest non randomly scattered previous glaciological lithological and seismotectonic explanations are insufficient to explain this spatial pattern and overlook the basic engineering geology prerequisites for failure massifs of similar relief and lithology can display intense or sparse rsf incidence geomorphological appraisal suggests an association with recently active glacial breaches of main and secondary watersheds with rsf being scarce or absent in valleys inherited from tertiary uplift and in mountain groups away from the main watersheds valleys which adapted early to ice discharge are seen as stress hardened with their slopes unlikely to reach critical thresholds for failure after subsequent reoccupations by ice concentrated erosion in the last glaciations is most likely to be found close to where breaches are actively forming or enlarging such erosion in the slope foot and valley floor may have daylighted failure planes or generated rebound stresses augmenting those from other endemic sources sufficiently to provoke widespread paraglacial rsf slope stress models for deglaciated valleys and comparative studies in other glaciated mountain ranges are required to test this concept and may assist in geohazard assessments