hazard investigation of the portillo rock avalanche site central andes chile using an integrated field mapping and numerical modelling approach abstract this paper reports a detailed rock slope hazard investigation of the portillo rock avalanche site located in the rugged mountains of the andean cordillera of central chile the site is important as it lies along the international santiago mendoza highway corridor connecting chile and argentina and a major ski resort is located on its deposits a number of large lobate shaped diamicton deposits were mapped and dated by cosmogenic nuclides 36 cl with the results showing that they correspond to two significant prehistoric rockslide events an integrated field mapping and numerical modelling investigation was subsequently carried out to assess the threat posed to the area by further rocksliding activity distinct element modelling was used to back analyze the failure mechanism and identify the geological model that best reproduced the portillo rock avalanche failure surface results show that a stress controlled failure at the toe of the slope followed by sliding along volcaniclastic bedding was the likely failure mechanism a 3 d dynamic runout analysis was carried out to back analyze which combinations of rheologies material properties and rockslide sequencing were best able to reproduce the current distribution of rockslide deposits results indicate that two separate sliding events originating from different sources had occurred with each involving different combinations of frictional and voellmy rheologies depending on the level of entrainment that occurred along each travel path insights gained from the back analysis were then used to carry out a forward analysis to assess the potential for a recurring major rockslide under several different triggering scenarios results suggest that a low probability m 7 8 earthquake would be required to trigger another rockslide from the original source area the rock slope was otherwise found to be stable even following high precipitation events nevertheless runout simulations for the estimated large magnitude earthquake triggered rockslide volume showed that for both a highly frictional and non saturated path i e dry season and a snow covered path winter the leading edge of the flow would override part of the international santiago mendoza corridor with the debris coming to rest in a flat lying area in the upper part of the valley overall the results from this integrated hazard assessment suggest that the hazard level is low

controls on reservoir quality of lower cretaceous tight sandstones in the laiyang sag jiaolai basin eastern china integrated sedimentologic diagenetic and microfracturing data abstract the jiaolai basin fig 1 is an under explored rift basin that has produced minor oil from lower cretaceous lacustrine deltaic sandstones the reservoir quality is highly heterogeneous and is an important exploratory unknown in the basin this study investigates how reservoir porosity and permeability vary with diagenetic minerals and burial history particularly the effects of fracturing on the diagenesis and reservoir deliverability the laiyang sandstones are tight reservoirs with low porosity and permeability

complete dynamic modeling calibration for the thurwieser rock avalanche italian central alps abstract few rock avalanches have been witnessed and no exact real time description is available the 2 5 m m 3 punta thurwieser rock avalanche september 2004 italian central alps is a unique event for which many quantitative observations have been gathered this is the first case ever of a natural rock avalanche being recorded on video and for which an almost exact value of the total time duration from initial detachment to final deposition is available the landslide travelled over 2 9 km from its source partially in a glacial environment the initial failure and the time for the complete evacuation of the source area were studied and assessed by a series of photos the mean front velocities along the path have been estimated from the video the final geometry and the characteristics of the deposit have been obtained by gps measurements aerial photos field surveys and laboratory tests a quasi 3d continuum dynamic analysis of the landslide motion has been performed assuming both a voellmy and a frictional rheology in the model dan 3d for the first time the landslide front velocities have been used for back analyses and calibration of the rheological parameters together with the final shape and thickness of the deposit and its developing extension the dynamic flow resistance parameters initially calibrated with dan were adopted and validated in dan 3d showing good consistency they are consistent with the existing database for calibrated landslides of similar type and scale flow velocities on the path segment underlain by glacial deposits up to 55 65 m s 1 are more accurately predicted by adopting a frictional rheology up to 50 55 m s 1 with zero pore pressure and a 26 friction angle than by a voellmy rheology up to 40 45 m s 1 both observations and modelling show that glacial ice plays a substantial role in increasing the rock avalanche mobility

the response of black rapids glacier alaska to the denali earthquake rock avalanches 1 we describe the impact of three simultaneous earthquake triggered rock avalanches on the dynamics of black rapids glacier alaska by using spaceborne radar imagery and numerical modeling we determined the velocities of the glacier before and after landslide deposition in 2002 by using a combination of ers 1 ers 2 tandem radarsat 1 and alos palsar synthetic aperture radar data ice velocity above the debris covered area of the glacier increased up to 14 after the earthquake but then decreased 20 by 2005 within the area of the debris sheets mean glacier surface velocity increased 44 within 2 years of the landslides at the downglacier end of the lowest landslide where strong differential ablation produced a steep ice cliff velocities increased by 109 over the same period by 2007 ice velocity throughout the debris area had become more uniform consistent with a constant ice flux resulting from drastically reduced ablation at the base of the debris without further analysis we cannot prove that these changes resulted from the landslides because black rapids glacier displays large seasonal and interannual variations in velocity however a full stokes numerical ice flow model of a simplified glacier geometry produced a reversal of the velocity gradient from compressional to extensional flow after 5 years which supports our interpretation that the recent changes in the velocity field of the glacier are related to landslide induced mass balance changes

rock slope instabilities in sogn and fjordane county norway a detailed structural and geomorphological analysis rock slope failures form a frequent hazard to many populated mountain regions especially in western norway the topographical and meteorological characteristics increase the vulnerability for rock slope failures a major focus for studies in norway is to eciently nd and investigate possible future rock slope failures in order to prevent extensive humanitarian disasters the determination of the critical parameters involved in the development of rock slope failures is crucial in order to optimize hazard recognition in addition a better understanding of the spatial and temporal variability of prehistoric and historic rock slope failures as well as present day rock slope instabilities will optimize monitoring and further research on the susceptibility for future rock slope failures the primary aim of this study is to investigate the spatial and temporal distribution of rock slope instabilities within western norway it is further aimed to determine the controlling parameters on the development of rock slope instabilities within the study region the implemented approaches range from regional scale statistical analyses towards site specic numerical modelling while a focus is set on quantitative analyses within this thesis the main controlling parameters are dened for rockfalls and rock slope instabilities on a regional scale for the entire county of sogn fjordane western norway it is demonstrated that always a combination of several parameters is necessary to destabilize a mountain side rockfalls have the strongest spatial relation to the presence of bare rock as well as landslide deposits the degree of tectonic deformation and the geological lineament density large rock slope instabilities develop preferentially within relatively weak rock units such as phyllites or weathered mac gneisses and at convex slope breaks looking more into detail a strong structural control is conrmed by numerical modelling for the unstable rock slope at stampa susceptibility and hazard are assessed at dierent scales and with dierent measures quantitative rockfall susceptibility is mapped on a regional scale for the entire county of sogn fjordane based on the statistical analysis of a set of controlling factors in addition this statistical susceptibility model is combined with a physically based model restricting the susceptibility map to areas that are steep enough to represent a potential rockfall source this combination allows using road inventories with registered impact points instead of release areas for susceptibility modelling in contrast relative susceptibility and also hazard are assessed locally for single parts of the unstable rock slope at stampa based on morphology and past activity present day annual expectable frequencies for rock slope failures of certain volume classes are determined for the storfjord region in western norway based on magnitude frequency analyses furthermore a semi quantitative hazard estimation is obtained for each potential instability based on a qualitative susceptibility assessment of each instability in this region this phd thesis presents results of the rst attempts of quantitative statistical analyses of dierent inventories covering rock slope instabilities in norway it is shown that susceptibility and hazard can be assessed with dierent measures forming the basis for further decisions regarding risk assessment and mitigation

landslides and climate change in the italian dolomites since the late glacial abstract the paper deals with the relationship between the temporal occurrence of landslides and climatic changes in the italian dolomites since the late glacial after an introduction on the state of the art with particular reference to the alpine region the results of recent investigations in the two study sites are illustrated at cortina d ampezzo several landslides were dated mainly by the radiocarbon method the most ancient landslide event there involved large rock slides which affected the dolomitic slopes following the withdrawal of glaciers after the last glacial maximum lgm and also slides and flows mainly occurring in pelitic materials of the valley floors from 13 000 to 10 000 cal bp a later series of flows occurred between 5500 and 2500 cal bp in the upper badia valley alta badia the most ancient events go back to 10 000 and 9000 cal bp and correspond with earth flows that followed vast rotational slides affecting the bedrock up to a depth of about 50 m more recent earth flows involving more modest amounts of material took place between 6500 and 2300 cal bp by analysing the dates from the two study areas it was possible to correlate the recorded increase of landslide activity with the climatic changes occurring at the boundary between the late glacial and the holocene and between the atlantic and the subboreal and to compare the results with those derived from other european regions the types and causes of landslides taking place in these two periods were substantially different reflecting the different morphoclimatic conditions that existed in the two areas when these mass movements were triggered finally notwithstanding the importance of non climatic causes such as geological structural factors and possible human influences it is concluded that many of the dated landslides can be considered as indicators of climatic change

factors controlling prolific gas production from low permeability sandstone reservoirs implications for resource assessment prospect development and risk analysis low permeability reservoirs from the greater green river basin of southwest wyoming are not part of a continuous type gas accumulation or a basin center gas system in which productivity is dependent on the development of enigmatic sweet spots instead gas fields in this basin occur in low permeability poor quality reservoir rocks in conventional traps we examined all significant gas fields in the greater green river basin and conclude that they all occur in conventional structural stratigraphic or combination traps we illustrate this by examining several large gas fields in the greater green river basin and suggest that observations derived from the greater green river basin provide insight to low permeability gas charged sandstones in other basins we present evidence that the basin is neither regionally gas saturated nor is it near irreducible water saturation water production is both common and widespread low permeability reservoirs have unique petrophysical properties and failure to fully understand these attributes has led to a misunderstanding of fluid distributions in the subsurface an understanding of multiphase effective permeability to gas as a function of both varying water saturation and overburden stress is required to fully appreciate the controls on gas field distribution as well as the controls on individual well and reservoir performance low permeability gas systems such as those found in the greater green river basin do not require a paradigm shift in terms of hydrocarbon systems as some have advocated we conclude that low permeability gas systems similar to those found in the greater green river basin should be evaluated in a manner similar to and consistent with conventional hydrocarbon systems to date resource assessments in the greater green river basin have assumed a widespread continuous type resource distribution failure to recognize some of the fundamental elements of low permeability reservoirs has led to an underappreciation of the risks associated with exploration and development investment decisions in these settings and likely a significant overestimation of available resource levels

practical approaches to identifying sealed and open fractures for one essential ingredient of permeable fracture networks degree of fracture pore space preservation in large fractures i show how the characterization challenge presented by sparse fracture sampling can be overcome by measuring a surrogate the abundance of rock mass cement that precipitated after fractures ceased opening sampling limitations are overcome because the surrogate is readily measured in small rock samples including sidewall cores and cuttings permitting site specific diagnosis of the capacity of fractures to transmit fluid over a wider range of sample depths than conventional methods allow a diverse core database shows that this surrogate correctly predicts where large fractures are sealed information on timing of fracture opening relative to cement sequence can be obtained in two ways first evidence of fracture movement history and cement sequences in sparse large fractures can be extrapolated to areas having only cement data alternately evidence of fracture timing can be acquired from sealed micrometer scale fractures distribution of porosity reducing cement is commonly heterogeneous from bed to bed and location to location in siliciclastic and carbonate rocks however because patterns of sealed or open fractures cannot be delineated using fracture observations alone surrogates have practical value for production fairway mapping and other applications in which identifying open fractures is essential this study highlights the vital interplay among structural and diagenetic processes for fracture porosity preservation or destruction

high temperature deformation during continental margin subduction exhumation the ultrahigh pressure western gneiss region of norway abstract a new dataset for the high pressure to ultrahigh pressure western gneiss region allows the definition of distinct structural and petrological domains much of the study area is an e dipping homocline with e plunging lineations that exposes progressively deeper more strongly deformed more eclogite rich structural levels westward although eclogites crop out across the wgr scandian deformation is weak and earlier structures are well preserved in the southeastern half of the study area the scandian reworking increases westward culminating in strong scandian fabrics with only isolated pockets of older structures the dominant scandian deformation was coaxial e w stretching the sinistrally sheared more trondelag fault complex and nordfjord mylonitic shear zone bound these rocks to the north and south there was moderate top e amphibolite facies deformation associated with translation of the allochthons over the basement along its eastern edge and the nordfjord sogn detachment zone underwent strong lower amphibolite facies to greenschist facies top w shearing a northwestward increase in exhumation related melting is indicated by leucosomes with hornblende plagioclase and scandian sphene in the western 2 3 of the study area exhumation related amphibolite facies symplectite formation in quartzofeldspathic gneiss postdated most scandian deformation further deformation was restricted to slip along biotite rich foliation planes and minor local folding that the western gneiss region quartzofeldspathic gneiss exhibits a strong gradient in degree of deformation implies that continental crust in general need not undergo pervasive deformation during subduction

database and online map service on unstable rock slopes in norway from data perpetuation to public information abstract the unstable rock slope database is developed and maintained by the geological survey of norway as part of the systematic mapping of unstable rock slopes in norway this mapping aims to detect catastrophic rock slope failures before they occur more than 250 unstable slopes with post glacial deformation are detected up to now the main aims of the unstable rock slope database are 1 to serve as a national archive for unstable rock slopes in norway 2 to serve for data collection and storage during field mapping 3 to provide decision makers with hazard zones and other necessary information on unstable rock slopes for land use planning and mitigation and 4 to inform the public through an online map service the database is organized hierarchically with a main point for each unstable rock slope to which several feature classes and tables are linked this main point feature class includes several general attributes of the unstable rock slopes such as site name general and geological descriptions executed works recommendations technical parameters volume lithology mechanism and others displacement rates possible consequences as well as hazard and risk classification feature classes and tables linked to the main feature class include different scenarios of an unstable rock slope field observation points sampling points for dating displacement measurement stations lineaments unstable areas run out areas areas affected by secondary effects along with tables for hazard and risk classification and url links to further documentation and references the database on unstable rock slopes in norway will be publicly consultable through an online map service factsheets with key information on unstable rock slopes can be automatically generated and downloaded for each site areas of possible rock avalanche run out and their secondary effects displayed in the online map service along with hazard and risk assessments will become important tools for land use planning the present database will further evolve in the coming years as the systematic mapping progresses and as available techniques and tools evolve

climate change and mass movements in the nw argentine andes abstract the chronology of multiple landslide deposits and related lake sediments in the eastern argentine cordillera suggests that major mass movements cluster in two time periods during the quaternary between 35 000 and 25 000 14 c yr bp and after 5000 14 c yr bp the older cluster may correspond to the minchin wet period 40 000 and 25 000 14 c yr bp identified in tropical and subtropical south america suggesting a causal relation between enhanced landslide activity and climate change the younger cluster predates the titicaca wet period that began at about 3900 14 c yr bp which also affected other regions in the andes and the amazon basin no landslide and associated lake sediments are documented during the tauca wet period between 16 000 and 8000 14 c yr bp however the two clusters correspond to periods where it assumed that the el nino southern oscillation enso and tropical atlantic sea surface temperature dipole tad were active the analysis of the present day precipitation patterns in nw argentina indicates significant spatial and temporal differences between the intra andean part of the study area and the andean foreland whereas the tad seems to consistently increase rainfall the intensity of precipitation during the el nino phase of the enso is reduced to only 25 of the mean annual average in the intra andean basins whereas the regions east of the andes receive more than 125 similar results but with an opposite sign characterize la nina events the comparison of this pattern with paleo precipitation data as inferred from varved lake sediments suggests that increased interannual climate variability and therefore increased fluctuations in rainfall and river discharge in narrow valleys may reduce landsliding thresholds

postglacial uplift neotectonics and seismicity in fennoscandia abstract fennoscandia has experienced major uplift in postglacial time which is assumed to reflect a glacial isostatic process connected to the melting of the last ice sheets extensive modelling of the isostatic movements show that the applied deglaciation and uplift model fit the observations well there are however areas with significant deviations between uplift measurements and regional model predictions the misfit between observations and the isostatic uplift modelling is interpreted here to reflect a tectonic component of the uplift the objective of the present investigation is to isolate this tectonic uplift component interestingly enough the areas found partly correspond to areas with pronounced seismic activity and the assumption that the postglacial rebound is responsible for much of the observed onshore seismicity is substantiated we conclude that there seems to be present day deformation along the shoreline of mid norway southern norway shoreline and mountain areas and along the swedish east coast with the centre northeast of the gulf of bothnia that cannot be explained by glacial isostasy not all of the deformations in these areas are necessarily co seismic the study suggests that such vertical deformations are small in magnitude and overprint the glacial rebound the deformations may be a consequence of the plio pleistocene erosional pattern which is of glacial origin

rock avalanches and the pace of late quaternary development of river valleys in the karakoram himalaya we discuss the implications of a set of terrestrial cosmogenic nuclide tcn ages on blocky cross valley deposits of large rock avalanches along upper indus streams the dated deposits are key to understanding late quaternary events that play a major role in landscape evolution in the karakoram himalaya the landslides occurred between 3 and 8 ka ago challenging existing chronologies of events along indus streams the tcn ages may support a mid holocene climatic role in preparing slopes for failure but the balance of evidence suggests that large earthquakes triggered the landslides each landslide dammed the indus or a major tributary and controlled base level and sedimentation for millennia they produced landforms long regarded as characteristic of the region including extensive lacustrine deposits flights of river terraces epigenetic gorges and sediment fans until the 1990s most of the landslides were interpreted as moraines related lacustrine and other sediments continue to be attributed to glacial damming and stream terraces to tectonic processes generally they were seen to originate tens of thousands to hundreds of thousands of years earlier than the new ages require instead we argue that they record interactions among different geomorphic processes in landslide fragmented valleys during the holocene rather than being geomorphic markers of tectonic and climatic events the landslides have buffered or redirected climatic and tectonic forcing in such an active orogen millennia long episodes of zero net bedrock incision at each site are surprising however rates of sedimentation above landslide barriers and erosion controlled by their breaching are close to today9s high measured rates for geomorphic activity we propose that landslide fragmented rivers may in fact characterize interglaciations and future patterns of upper indus landscape evolution at time scales of 10 3 to 10 4 years

friction and dynamics of rock avalanches travelling on glaciers rock avalanches travelling on glaciers often exhibit effective friction coefficient lower than those on a rocky terrain after briefly considering some data of rock avalanches on glaciers the physics of sliding of solid objects on icy surfaces is reviewed and a model is put forward for the mechanics of rock avalanche sliding on ice accounting for the formation of a natural lubricating layer it is suggested that at the beginning of the flow of a rock avalanche friction results from rocky blocks ploughing on ice as the erosion continues a gouge of ice particles results which clogs the interstices between blocks and may partially melt as a consequence of the production of frictional heat this conceptual model is numerically investigated for a slab travelling on ice the results show an increase in mobility as a function of slab thickness travelled length and the gravity field in agreement with case studies the results are useful to interpret the peculiar features of rock avalanches travelling on icy surfaces such as digitations out runner blocks and longitudinal furrows the lubrication theory for landslides on ice proposed here may provide a framework for understanding landslides on earth and for future modelling in addition it may help elucidate the presence of similar landslide deposits on the surface of mars

diagenetic history of tight sandstones and gas entrapment in the yulin gas field in the central area of the ordos basin china abstract the ordos basin is a large cratonic basin with an area of 250 000 km2 in central china upper paleozoic coals and shales serve as gas source rocks with peak generation and migration at the end of the early cretaceous recent exploration has verified the huge gas potential in the basin centered gas accumulation system bcgas however the mechanism for the gas accumulation is controversial with an integrated approach of thin section petrography ultra violet fluorescence microscopy fluid inclusion microthermometry raman microspectrometry scanning electron microscopy and x ray diffractometry we identified diagenetic trapping and evaluated the diagenetic history of sandstone reservoirs in the yulin gas field in the central area where structural stratigraphic and or sedimentary lithologic traps have not been found it was revealed that three phases of diagenesis and hydrocarbon charging occurred respectively in the late triassic late jurassic and at the end of the early cretaceous in the first two phases acidic water entered the reservoir and caused dissolution and cementation resulting in porosity increase however further subsidence and diagenesis including compaction and cementation markedly reduced the pore space at the end of the early cretaceous the bulk of the gas migrated into the tight reservoirs and the bcgas trap was formed in the updip portion of this system cementation continued to occur due to low gas saturation and has provided effective seals to retain gas for a longer period of time than water block in the bcgas the mechanism for the gas entrapment was changed from water block by capillary pressure in the bcgas to diagenetic sealing the diagenetic seals in the updip portion of the sand body were formed after gas charging which indicates that there is a large hydrocarbon exploration potential at the basin centered area

how porosity and permeability vary spatially with grain size sorting cement volume and mineral dissolution in fluvial triassic sandstones the value of geostatistics and local regression although it is well known that sandstone porosity and permeability are controlled by a range of parameters such as grain size and sorting amount type and location of diagenetic cements extent and type of compaction and the generation of intergranular and intragranular secondary porosity it is less constrained how these controlling parameters link up in rock volumes within and between beds and how they spatially interact to determine porosity and permeability to address these unknowns this study examined triassic fluvial sandstone outcrops from the uk using field logging probe permeametry of 200 points and sampling at 100 points on a gridded rock surface these field observations were supplemented by laser particle size analysis thin section point count analysis of primary and diagenetic mineralogy quantitative xrd mineral analysis and sem edax analysis of all 100 samples these data were analyzed using global regression variography kriging conditional simulation and geographically weighted regression to examine the spatial relationships between porosity and permeability and their potential controls the results of bivariate analysis global regression of the entire outcrop dataset indicate only a weak correlation between both permeability porosity and their diagenetic and depositional controls and provide very limited information on the role of primary textural structures such as grain size and sorting subdividing the dataset further by bedding unit revealed details of more local controls on porosity and permeability an alternative geostatistical approach combined with a local modeling technique geographically weighted regression gwr subsequently was used to examine the spatial variability of porosity and permeability and their controls the use of gwr does not require prior knowledge of divisions between bedding units but the results from gwr broadly concur with results of regression analysis by bedding unit and provide much greater clarity of how porosity and permeability and their controls vary laterally and vertically the close relationship between depositional lithofacies in each bed diagenesis permeability and porosity demonstrates that each influences the other and in turn how understanding of reservoir properties is enhanced by integration of paleoenvironmental reconstruction stratigraphy mineralogy and geostatistics

combining digital elevation model analysis and run out modeling to characterize hazard posed by a potentially unstable rock slope at turtle mountain alberta canada abstract turtle mountain in alberta canada has become an important field laboratory for testing different techniques related to the characterization and monitoring of large slope mass movements as the stability of large portions of the eastern face of the mountain is still questionable in order to better quantify the volumes potentially unstable and the most probable failure mechanisms and potential consequences structural analysis and runout modeling were preformed the structural features of the eastern face were investigated using a high resolution digital elevation model hrdem according to displacement datasets and structural observations potential failure mechanisms affecting different portions of the mountain have been assessed the volumes of the different potentially unstable blocks have been calculated using the sloping local base level slbl method based on the volume estimation two and three dimensional dynamic runout analyses have been performed calibration of this analysis is based on the experience from the adjacent frank slide and other similar rock avalanches the results will be used to improve the contingency plans within the hazard area

sandstone diagenesis and reservoir quality prediction models myths and reality models and concepts of sandstone diagenesis developed over the past two decades are currently employed with variable success to predict reservoir quality in hydrocarbon exploration not all of these are equally supported by quantitative data observations and rigorous hypothesis testing simple plots of sandstone porosity versus extrinsic parameters such as current subsurface depth or temperature are commonly extrapolated but rarely yield accurate predictions for lithified sandstones calibrated numerical models that simulate compaction and quartz cementation when linked to basin models have proven successful in predicting sandstone porosity and permeability where sufficient analog information regarding sandstone texture composition and quartz surface area is available analysis of global regional and local data sets indicates the following regarding contemporary diagenetic models used to predict reservoir quality 1 the effectiveness of grain coatings on quartz grains e g chlorite microquartz as an inhibitor of quartz cementation is supported by abundant empirical data and recent experimental results 2 vertical effective stress although a fundamental factor in compaction cannot be used alone as an accurate predictor of porosity for lithified sandstones 3 secondary porosity related to dissolution of framework grains and or cements is most commonly volumetrically minor 2 exceptions are rare and not easily predicted with current models 4 the hypothesis and widely held belief that hydrocarbon pore fluids suppress porosity loss due to quartz cementation is not supported by detailed data and does not represent a viable predictive model 5 heat flow perturbations associated with allochthonous salt bodies can result in suppressed thermal exposure thereby slowing the rate of quartz cementation in some subsalt sands

relationship between diagenesis and reservoir quality in sandstones of the garn formation haltenbanken mid norwegian continental shelf a quantitative model is proposed for the dependence of porosity and permeability on diagenesis in subarkosic arenites of the middle jurassic garn formation porosity variation is controlled by the combined effects of compaction and quartz cementation in general more porosity has been lost by compaction than by quartz cementation but compactional porosity loss appears to have occurred relatively early in the burial history before burial below 2 km below the sea floor thus progressive reduction of the total porosity with increasing burial below 2 km results mainly from quartz cementation permeability is a function of the abundance of intergranular macroporosity which is interpreted to be a measure of effective porosity at depths less than 3 5 km below the sea fl or intergranular macroporosity generally comprises more than 50 percent of the total porosity but at greater depth as total porosity decreases below about 16 percent the ratio of effective to ineffective porosity drops below one this depth corresponds to the onset of extensive illitization and grain dissolution which results in major reorganization of the pore system generation of secondary porosity by feldspar dissolution appears not to have been beneficial to reservoir quality in the garn formation but it is regarded as an intrinsic part of the overall process of porosity destruction with increasing diagenesis

analyses of past and present rock slope instabilities in a fjord valley implications for hazard estimations abstract for quantitative hazard assessment it is necessary to define the magnitude frequency distribution and a temporal model of the landslide frequency this is often complicated for large rock slope failures due to the lack of significant numbers of large rock slope failures in inventories of a given homogeneous region or sparse information about the timing an inventory of 108 rock slope failure deposits within the fjords of the storfjord region including a relative rockslide chronostratigraphy was available for this study the temporal distribution of rock slope failures is characterized by a rapid response with a high frequency of failures directly after deglaciation followed by a lower constant frequency since 9 000 years bp for the entire storfjord region the largest recorded volumes failed directly after deglaciation volumes larger than 5 10 6 m 3 have not been recorded within the last 9 000 years in addition 17 rockslide scars and on the other hand 17 potential rock slope instabilities have been mapped at the northeastern flank of tafjord which is a branch of the storfjord volume frequency relations have been developed for the three inventories from tafjord comprising i fjord deposits ii rockslide scars and iii potential instabilities they result in very similar distributions over the entire volume range all three inventories are underlying the same processes that lead to destabilisation and finally failure additionally the compilation of the three inventories is independent and based on different methodologies the similarity of the volume frequency distributions is thus verifying the different inventories hence the obtained volume frequency relation can be used to assess the rockslide hazard for the study area present day annual expectable frequencies for different volume classes have been assessed based on the obtained volume frequency relation of the fjord deposits for example the average annual frequency for rock slope failures of v 1 10 6 m 3 originating from the northeastern flank of tafjord is 1 1670 based on a lognormal distribution this regional hazard can be used to improve previously existing qualitative susceptibility rankings for potential unstable rock slopes within the tafjord region the resulting probabilities are very low however the uncertainties of all hazard estimates are very high

a model for the analysis of rapid landslide motion across three dimensional terrain a new numerical model for the dynamic analysis of rapid flow slides debris flows and avalanches has been developed the model is an extension of an earlier algorithm and is implemented using a nu

diagenesis provenance and reservoir quality of triassic tagi sandstones from ourhoud field berkine ghadames basin algeria the triassic tagi trias argilo greseux inferieur fluvial sandstones are the main oil reservoirs in the berkine basin algeria nonetheless their provenance and diagenesis and their impact on reservoir quality are virtually unknown samples from the ourhoud field representing the lower middle and upper tagi subunits were studied using a combination of petrographic mineralogical and geochemical techniques the lower tagi sandstones have an average framework composition of q98 3f0 6r1 1 and 95 of the quartz grains are monocrystalline by contrast the middle upper tagi sandstones have an average framework composition of q88 3f9 8r1 9 and 79 7 of the quartz grains are monocrystalline the lower tagi quartz arenites derived from paleozoic siliciclastic rocks whereas the middle upper tagi subarkoses originated mainly from metamorphic terrains this change in provenance is a potential criterion for correlation within the tagi also this change has contributed to the significantly different diagenetic paths followed by the lower tagi quartz arenites and the middle upper tagi subarkoses grain coating illitic clays are abundant in the lower tagi where they exert a critical control on reservoir quality these clays are interpreted as pedogenic and or infiltrated in origin and to have had in part smectitic precursors shallow burial fe dolomite cementation was favored in the downthrown block of the field bounding fault where it contributed to the poor reservoir quality magnesite siderite cements are multiphase the earliest generation is composed of fe rich magnesite that precipitated during shallow burial from hypersaline fluids with high mg ca ratios probably refluxed residual brines associated with the liassic evaporites later magnesite siderite generations precipitated during deeper burial from waters with progressively higher fe mg ratios authigenic vermicular kaolin largely consists of dickite that replaced previously formed kaolinite dickitization was followed by late stage illitization related to the dissolution of detrital and authigenic k feldspar quartz the most abundant cement was mainly sourced by the pressure or clay induced dissolution of detrital quartz and is a critical factor controlling the reservoir quality overall quartz cement is more abundant in the lower tagi than in the middle upper tagi and this increase correlates with a decrease in average porosity within the lower tagi quartz cement abundance is stratigraphically very variable which is in part related to facies controlled variations in grain coating clay resulting in major vertical variations in reservoir quality anhydrite and barite cements postdate quartz overgrowth the sulfate necessary for their formation was likely sourced by deep subsurface dissolution of late triassic liassic evaporites

the hattian bala rock avalanche and associated landslides triggered by the kashmir earthquake of 8 october 2005 the kashmir earthquake of the 8 october killed an estimated 87 350 people 25 500 through co seismic landslides the largest landslide associated with the earthquake was the 68 106 m3 hattian bala rock avalanche that destroyed a village and killed around 1000 people the deposit blocks the valley to a depth of 130 m impounding a lake that reached the dam crest in april 2007 an outburst flood now threatens a major settlement 3 km downstream a series of space images reveals landslide clusters in the rock avalanche source area prior to the earthquake the images also reveal a large slow moving landslide with its toe in the lake failure of this landslide may induce dam failure through overtopping and scour eighty five landslides in the hattian bala catchment predate the shaking of 8 october 2005 a further 73 are co seismic with the main shock and 21 postdate it in the period up to october 2006 landslide magnitude frequency distribution plots derived from satellite images allow an assessment of the contribution of seismically triggered events as compared to background rates of activity

sandstone reservoir quality prediction the state of the art joanna ajdukiewicz joined exxon production research company in 1980 she was reservoir quality assessment and prediction team lead there from 1991 to 1995 and at imperial oil research centre in calgary from 1995 to 1997 subsequently she has worked a variety of exploration company assignments in the north sea gulf of mexico and middle east her current interests are in predicting the distribution of early diagenetic controls on deep reservoir quality rob lander develops diagenetic models for geocosm llc he obtained his ph d in geology from the university of illinois in 1991 was a research geologist at exxon production research from 1991 to 1993 and worked for rogaland research and geologica as from 1993 to 2000 he is also a research fellow at the bureau of economic geology to guess is cheap to guess wrongly is expensive chinese proverb reservoir quality predictive models will be a useful element of risk analysis until remote sensing tools are invented that accurately measure effective porosity and permeability ahead of the bit this issue of the aapg bulletin highlights recent advances in a new generation of reservoir quality models that have successfully predicted porosity and permeability in diverse siliclastic reservoirs under many different burial conditions most previous attempts at predrill reservoir quality prediction have relied on empirical correlations or on first principle geochemical simulations that incorporate laboratory derived input parameters wood and byrnes 1994 the new reservoir quality models differ from previous approaches in that although incorporating theory inspired algorithms they include terms with values that are explicitly designed to be calibrated by and tested against data sets of high quality petrographic analyses that are linked to thermal and effective stress histories petrographic observations therefore provide essential constraints in these models on the types timing and rates of key geologic processes affecting sandstone pore systems this approach avoids the pitfalls inherent

from incipient slope instability through slope deformation to catastrophic failure different stages of failure development on the ivasnasen and vollan rock slopes western norway abstract the long term evolution of rock slope failures involves different stages from incipience of slope instability to catastrophic failure through a more or less long lasting slope deformation phase that also involves creeping or sliding topography lithology and structural inheritance are the main intrinsic factors that influence this evolution here we investigate the role of these intrinsic factors on the rock slope failure development of the ivasnasen and vollan rock slopes sunndal valley western norway using a multitechnique approach that includes geomorphologic and structural field mapping kinematic analysis terrestrial cosmogenic nuclide exposure dating topographic reconstruction and deformation quantification ivasnasen is a rock slope failure complex with several past rock slope failures and a present unstable rock slope located on a cataclinal nw facing slope and developed in augen gneiss vollan on the opposite valley side is a deep seated gravitational slope deformation dsgsd affecting the whole mountainside developed in quartzite in the upper part and micaschist in the lower part these different lithologies belong to different nappe complexes that were emplaced and folded into a series of syn and anticlines during the caledonian orogeny these folds lead to different lithologies being exposed in different structural orientations on the opposite valley flanks which in turn leads to different types and evolution of rock slope failures at ivasnasen the 45 55 nw dipping ductile foliation allowed for a fairly simple planar sliding mechanism for the 1 2 million m 3 post glacial rock slope failure failure occurred ca 3 3 ka ago after a short period of prefailure deformation for the present 2 2 million m 3 unstable rock slope at ivasnasen a steepening of the foliation at the toe impedes such a mechanism and up to 10 m of displacement has not lead to a catastrophic failure yet the vollan dsgsd is characterized by a steep major back scarp with its up to 130 m wide graben which opened along the subvertical foliation in the quartzite and a conspicuous array of counter scarps in the micaschist the morphologic features are explained by a flexural toppling mechanism in the micaschist which likely initiated in the lower slope section and propagated retrogressively until reaching the massive quartzite at the back scarp flexural toppling cannot solely explain the total along slope displacement of up to 200 m i e an elongation of 28 creep along a basal shear zone which may have developed in the hinge zone of the flexural toppling combined with shallow valley dipping joints likely accounts for the large elongation implications of this study for the hazard assessment of unstable rock slopes in norway include the relatively rapid development of instabilities in cataclinal slopes and the important insights on long term displacement rates gained from cosmogenic nuclide dating for a better understanding of the evolution of unstable rock slopes

tephrochronologic constraints on temporal distribution of large landslides in northwest argentina abstract two morphologic settings in the northwestern argentine prone to giant mountain front collapse deeply incised narrow valleys and steep range fronts bordering broad piedmonts were analyzed through detailed investigations of fossil landslides and related fluvio lacustrine sediments nine different rhyodactic tephra layers were defined by geochemical fingerprinting of glass morphology of pumice stratigraphic relationships and mineralogy the age of three tephra could be determined either directly by 40ar 39ar dating or relatively by 14c dating of associated sediments paranilla ash documentclass aastex usepackage amsbsy usepackage amsfonts usepackage amssymb usepackage bm usepackage mathrsfs usepackage pifont usepackage stmaryrd usepackage textcomp usepackage portland xspace usepackage amsmath amsxtra usepackage ot2 ot1 fontenc newcommand cyr renewcommand rmdefault wncyr renewcommand sfdefault wncyss renewcommand encodingdefault ot2 normalfont selectfont decl

subsurface fractures and their relationship to stress history in east texas basin sandstone abstract subsurface fractures were sampled with more than 400 m of core from the lower cretaceous travis peak formation a tabular sandstone and shale unit approximately 600 m thick that was deposited in the gradually subsiding gulf coast basin depth to the top of the formation in east texas now ranges between 1800 and 2900 m fractures in sandstone exhibit features that are due to intermittent fracturing and sealing crack seal which suggest that the fractures are the result of episodes of fluid pressure in excess of hydrostatic correlation of the vein mineral precipitation sequence with the diagenetic history and the results of previous 18 o studies of quartz cement indicates that fractures propagated at depths of between 900 and 1500 m during the migration of quartz precipitating fluids fracture permeability provides a mechanism for the passage of large fluid volumes recorded by the precipitation of extensive quartz cement in the formation fractures stopped propagating before maximum burial depth was achieved during approximately 1500 m of subsequent burial fractures either remained partly open or were sealed by postkinematic ankerite and clay minerals

longitudinal ridges in mass movement deposits prominent longitudinal features are often reported on the surfaces of mass movement deposits however the genesis and implications of these have not hitherto been considered and herein we present preliminary observations of their occurrence both in the field and in the laboratory elongated ridges are often oriented sub parallel to the flow direction and aligned radially from the source due to debris spreading they are particularly prominent in large 106m3 rock avalanches emplaced onto deformable substrates and are also found in the proximal reaches of volcanic debris avalanches flowbands which are longer and thinner expressions of longitudinal ridges are continuous along the entire flow length and are observed in rock avalanches emplaced onto glaciers in snow and some ice avalanches in pyroclastic flows and some block and ash flows in ejecta sheets in extraterrestrial landslides and in some volcanic debris avalanches other volcanic debris avalanches and the distal areas of rock avalanches often display hummocks that are aligned radially from the source we propose that these aligned hummocks are remnants of longitudinal ridges the formation of elongate ridges and their expressions as flowbands aligned hummocks or distal lobes and digits in qualitatively similar fashion in both laboratory and field environments suggests they represent an intrinsic tendency of granular flows in a wide range of situations

surface exposure dating of the flims landslide graubunden switzerland abstract sixteen boulder and bedrock surfaces related to the flims landslide volume 8 12 km3 were dated with 36cl and 10be exposure ages range from 4900 250 yr to 15 440 1480 yr including corrections made due to snow cover and karst erosion ages of 11 410 590 yr and 13 340 1090 yr were obtained on bedrock surfaces outside of the landslide zone these are minima for deglaciation of segnes valley and provide constraints on possible amounts of inherited nuclides based on seven boulder ages which range from 8200 260 to 9520 990 yr a mean of 8900 700 years is calculated for the flims landslide we exclude three outliers one significantly older and two significantly younger than the others and the ages from the cassons bedrock site from the mean calculation the latter is excluded as shielding due to snow and vegetation cover is difficult to constrain there the oldest boulder on the landslide yielded an age 15440 1480 yr more than 5000 years older than any other boulder age suggesting that it included the surface of the pre slide bedrock the exposure ages are consistent with a single failure event the erratics and patches of till lying on the landslide debris must have been carried piggy back on top of the landslide rather than having been deposited by the late pleistocene vorderrhein glacier the flims rockslide is about the same age as the kofels 9800 yr and kandertal 9600 yr rockslides all three occurred during the marked transition to warmer wetter conditions during the early holocene

a re examination of the mechanism and human impact of catastrophic mass flows originating on nevado huascaran cordillera blanca peru in 1962 and 1970 abstract the 1962 and 1970 huascaran mass movements originated as rock ice falls from the mountain s north peak transformed into higher volume high velocity mud rich debris flows by incorporation of snow from the surface of a glacier below huascaran and the substantial entrainment of morainic and colluvial material from slopes below the glacier terminus water for fluidization of the entrained material originated in the melting of incorporated snow and the liberation of soil moisture contained within the entrained materials eyewitness reports indicate very high mean velocities for the events 17 35 m s 1962 and 50 85 m s 1970 the runout distances and velocity profiles of both events were simulated using dan w both mass movements continued downstream in the rio santa as debris floods aluviones that in 1970 reached the pacific at a distance of 180 km in strong contrast to publications in the geosciences literature 1961 peru census data indicates that the death toll of the 1970 event is ca 6000 and that total life loss in the two events did not exceed 7000 people

diagnostic characteristics and paleodynamics of supraglacial rock avalanches innerdalen western norway abstract misinterpretation of rock avalanche deposits in mountain environments is not uncommon because of the complex interactions between rock avalanches and glaciers this paper for the first time presents a detailed description of suspicious rock boulder deposits which are remnants of a rock avalanche onto a late pleistocene glacier the boulder deposits cover around 1 1 km 2 and are distributed over an area of around 7 5 km 2 and a variety of landforms three closely nested distinct terminal moraines 0 45 km 2 and dislocated terminal moraines 0 34 km 2 entirely built up of large boulders lateral moraines that decrease in elevation over a short distance and connect to the terminal moraines small patches 0 02 km 2 of boulders that occur in islands on a peat dominated valley floor and large patches of boulder fields 0 25 km 2 in size hanging 350 m above the valley floor the latter are disconnected from any potential source area 10 be cosmogenic nuclide ages of the three terminal moraines give an indistinguishable late pleistocene age of 13 6 1 4 ka whereas the largest boulder field that is located on the opposite side of the valley from the failed mountain yields a 10 be age of 14 1 0 4 ka which is slightly older but indistinguishable from the moraine deposits within uncertainty margins all boulder deposits add up to a volume of 31 10 6 m 3 the interpretation of a single rock avalanche source for those landforms is further confirmed by numerical runout modeling using dan3d a failure of the entire volume from skarfjellet mountain would result in a runout pattern that is identical to that of the distributed boulder fields when considering that the valley was filled with a glacier around 350 m thick the rock avalanche would not reach the position of the terminal moraines however a glacial re advance could have transported the boulders to that position the late pleistocene rock avalanche was followed by a holocene rock avalanche with a volume of 23 10 6 m 3 and a typical lobate deposit damming the innerdalen valley and creating a lake 10 be ages indicate that this event occurred 7 97 0 94 ka ago structural measurements performed on high resolution lidar scans show a strongly jointed source rock with three joint sets with dip dip direction 81 034 86 331 and 77 354 and a foliation with 22 003 the kinematic of the failures can thus be a combination of small scale wedge failures and planar sliding on shallow dipping foliation our detailed description can enable a better identification and interpretation of similar deposits in other mountain areas

the pandemonium creek rock avalanche british columbia in 1959 a rock spur became detached from the headwall of a cirque near pandemonium creek in the southern coast mountains of british columbia approximately 5 000 000 cu m of blocky gneissic quartz diorite debris travelled 9 0 km along a highly irregular path descending a vertical distance of 2 km to the valley of south atnarko river the high mobility of the rock avalanche is manifested by superelevation in valley bends two run ups and two right angle changes in flow direction this mobility is due in part to 1 peculiarities in the path of the landslide lateral moraines for example funnelled and accelerated the debris and 2 travel over a glacier below the detachment zone although most of the debris came to rest on the upper part of a fan at the mouth of pandemonium creek one lobe traversed the fan and entered knot lakes where it generated displacement waves that destroyed trees along the shore run up and superelevation data indicate that the debris was moving between 81 and 100 m s as it entered the run up zone at pandemonium creek and 21 38 m s in pandemonium valley to the east these velocities were analysed by applying the dynamic model of h j korner rock mechanics 1976 8 225 256 to the path of the landslide the analysis suggests that the rock avalanche had two phases a very rapid initial phase from detachment to the beginning of the run up and following sudden energy losses at the run up a second phase involving much lower velocities the pandemonium creek landslide is similar in many respects to much larger highly mobile rock avalanches in other parts of the world for example huascaran peru and little tahoma peak washington u s a although much less common than rockfalls and debris flows rock avalanches are capable of far greater damage this is a consequence of their size and the fact that they travel great distances at high velocities the potential exists for other highly mobile landslides of the pandeminium creek type in the mountains of western canada highlighting the need for caution in the future development of this region

characteristics and origin of the major authigenic minerals and their impacts on reservoir quality in the permian wutonggou formation of fukang sag junggar basin western china abstract this research is focused on the characteristics and origin of major authigenic minerals and the influences on the reservoir quality of the permian wutonggou formation sandstones in the eastern slope of fukang sag junggar basin western china authigenic cements were observed and described from thin sections scanning electron microscopy fluorescence and cathodoluminescence the elemental concentrations of the authigenic minerals were measured by electron probe microanalysis additional characterizations were obtained from o and c stable isotope ratios and from the homogenization temperature of aqueous fluid inclusions the results show that the sandstones in the wutonggou formation are dominated by volcanic lithic fragments carbonates and laumontites are the major authigenic minerals in the study area authigenic quartz and kaolinite can also be observed two types of carbonate cements are identified the first type is calcite with yellow fluorescent hydrocarbon inclusions the carbon and oxygen isotopes in the calcites are highly c depleted and o depleted the homogenization temperatures of the aqueous fluid inclusions in the calcite cements are higher than the highest paleogeotemperatures during the burial history combined with the presence of authigenic fibrous illites and the illitization of kaolinites it is determined that the precipitation of the calcites is related to the upwelling of deep fluids and was impacted by the co 2 from the thermal decarboxylation of organic matters during the middle late jurassic the second type is ferroan calcite with blue fluorescent hydrocarbon inclusions and higher contents of fe mn cr and mg than in the calcites the ferroan calcites in the beisantai uplift are rich in 13 c 13 c v pdb values are 22 10 and 22 16 the precipitation of these ferroan calcites was impacted by the co 2 from crude oil biodegradation after the late jurassic two types of laumontites are identified the first type is partially dissolved and is characterized by a high ca na ratio and low fe contents the second type is hardly dissolved has hydrocarbon inclusions with yellow and blue fluorescence and is characterized by a low ca na ratio and high fe contents the first type of laumontite was precipitated prior to hydrocarbon charging and the second type was formed after hydrocarbon charging and meteoric water leaching the hydration of the volcanic debris provided the source materials for both types of laumontite the authigenic quartz and kaolinite were formed by the alteration of feldspars laumontites and volcanic materials the evolution of the reservoir properties was impacted by various degrees of cementation and dissolution as a result the reservoir quality in the beisantai uplift was better than in the shaqiu area

diagenesis and reservoir quality evolution of fluvial sandstones during progressive burial and uplift evidence from the upper jurassic boipeba member reconcavo basin northeastern brazil the reservoir quality of fluvial sandstones of the upper jurassic boipeba member reconcavo basin northeastern brazil is highly heterogeneous and controlled by eodiagenesis under semiarid climate mesodiagenesis during burial to a depth of 3500 m and telodiagenesis due to local uplift eodiagenesis resulted in mechanical compaction calcite cementation clay infiltration and limited grain dissolution whereas mesodiagenesis resulted in the precipitation of calcite cement and quartz over growths intergranular quartz grain dissolution chloritization and illitization of smectite and albitization of feldspars sandstones continuously buried at maximum burial depths of about 1600 m t 65 c since 125 ma display a relatively greater degree of mesogenetic modifications and on average poorer reservoir quality than sandstones that were buried deeper 2100 m t 75 c prior to uplift but only since 13 ma uplift which affected the sequence along the western border of the basin has resulted in telogenetic dissolution of framework silicates and formation of kaolinite relatively good reservoir quality in the deeply buried sandstones occurs when 1 the grains are coated with a thin layer of chloritized infiltrated smectite 2 there is little or no pseudomatrix and 3 there are widely scattered patches of eogenetic calcite cement that supported the framework of sandstones against compaction

potassium leached zones at the contacts of the garn formation mid norwegian continental shelf evidence for the role of shale in sandstone diagenesis abstract

granular flow experiments on the interaction with stationary runout path materials and comparison to rock avalanche events the central focus of this work is to study the processes acting well below the surface of a moving rock or debris avalanche during travel over stationary substrate material small scale physical models at a linear scale of 1 104 used coal as avalanche analogue material and different granular material simulating sedimentary substrates varying in frictional resistance thickness and relative basal boundary roughness as well as inerodible non deformable runout path conditions substrate materials with the least frictional resistance showed the greatest response to granular flow overriding becoming entirely mobilized beneath and ahead of the moving mass and producing the longest runout observed with a unique deposit profile shape with a smooth substrate basal contact failure occurred along this plane and avalanche and substrate became coupled during runout with a rough base however temporary force chains of grain contacts in the substrate prevailed longer imparted their resistance to motion shear into the granular flow and the flow rear section consequently halted earlier than when moving over substrates with a weak base reducing substrate thickness diminished the effect of basal contact roughness on granular flow runout and deposit length inerodible non deformable substrate conditions caused changes in granular flow behaviour from essentially en masse sliding on low friction surfaces to increasing granular agitation over rougher paths copyright 2012 john wiley sons ltd

relationship between weathering mountain uplift and climate during the cenozoic as deduced from the global carbon strontium cycle model abstract a global carbon strontium coupled model over the cenozoic is presented the carbon cycle includes improvements on the uplift parameter in the himalayan and tibetan regions and the hydrothermal flux at back arc basins from the carbon cycle model of kashiwagi and shikazono kashiwagi h shikazono n 2003 climate change during the cenozoic inferred from global carbon cycle model including igneous and hydrothermal activities palaeogeography palaeoclimatology palaeoecology 199 167 185 the strontium cycle incorporates groundwater flux basalt weathering and himalayan weathering the model result indicates that the paleocene to the late eocene is characterized by decreasing strontium weathering and gradually increasing isotopic value 87sr 86sr which is a result of the decrease in radiogenic silicate weathering and less radiogenic carbonate weathering caused by decline of the atmospheric temperature since then the 87sr 86sr continuously increases towards the present the increase in the sr isotopic value from 40 ma to 35 ma is attributed to appearance of hydrothermal calcite in the himalayan region the increasing patterns of the 87sr 86sr from that time to the early miocene roughly correspond to the continental glaciations in high latitudes such as those at the eocene oligocene boundary in the middle miocene and at the oligocene miocene boundary radiogenic weathering accelerated by physical erosion due to glaciations and the subsequent deglaciations as suggested by previous studies might be related however there are time lags between the 87sr 86sr and 18o signals which might have resulted from long residence time of sr in the ocean reactivity of minerals under such low temperature and other climatic conditions is still unclear more supportive works to assure a favourable environment for sufficient weathering and to constrain the timings and amplitudes of the glacial events during these periods would be necessary the presented model shows the increase in the sr weathering flux since the late miocene which would have induced the elevation of seawater 87sr 86sr whereas the evolution of the glaciations partially might have contributed to that some disagreement between other studies and the model is confirmed the evaluation of the palaeo sealevel variation and carbonate compensation depth might produce the uncertainties in the estimate of weathering flux moreover the basaltic province through which several major rivers drain and discrimination of these rivers and the ganges brahmaputra indus might be important for the strontium cycle because these rivers are likely to be influenced by the radiogenic upstream area and non radiogenic downstream province whose 87sr 86sr would have changed considerably during the cenozoic despite these uncertainties it is clear that we can not attribute the increase in the seawater 87sr 86sr values during the cenozoic entirely to the influence of the himalayan uplift and the seawater 87sr 86sr variation does not serve as a proxy for silicate weathering rate and atmospheric co2 consumption rate of atmospheric co2

dynamic modelling of entrainment in rapid landslides entrainment of path material is an important feature of many rapid landslides the associated increases in volume and changes in flow character can significantly influence mobility a simple material entrainment algorithm based on the assumption of natural exponential growth with displacement has been incorporated into a new computer model designed to simulate rapid landslide motion across 3d terrain the user controls the growth rate and can also implement a change in rheology at the onset of entrainment a hypothetical example is used to demonstrate the influence of the mass and momentum transfer assumptions a back analysis of the 1999 nomash river landslide is included to show that the simple model is capable of simulating the bulk characteristics of a complex event involving substantial entrainment key words landslides debris flows rock avalanches entrainment erosion dynamic modelling

rock avalanches that travel onto glaciers and related developments karakoram himalaya inner asia abstract catastrophic rock slope failures in rugged terrain commonly generate rock avalanches when these occur in glacier basins the extent of landslide run out and its emplacement geometry are affected by movement over ice substantial modifications of glacier activity and sedimentation can follow ice activity leads to rapid modification transport and dispersal of landslide debris the nature of these interactions is described from observations over 20 years at bualtar glacier in the karakoram in august 1986 rock avalanches descended onto the ablation zone of the glacier their moisture content and patterns of deposition were affected by travel over ice glacier movement increased sharply at and below the rock avalanche deposits and within a few months the glacier surged a second surge occurred 2 years later major slope failures and debris flows were triggered beyond the ice margins and ponded melt water led to small outburst floods by 2005 the landslide material had been transported some 9 km about one third of this distance in the surges eventually it was fully reworked to become less readily distinguishable from other heavy supraglacial debris a large area of thickened ice persisted where the debris reduced ablation a positive impact on mass balance equivalent to a 20 increase in annual accumulation however it occurred as a moving segment of the ablation zone in 10 years it had in effect replaced the mass transferred in the surges data for the mid 1980s indicate the rock avalanches exceeded pre existing supraglacial debris by roughly five times and over a 30 year period will equal almost 500 years of normal supraglacial transport to the glacier margins other impacts of the episode suggest a doubling of this contribution to denudation similar developments were observed at three other glaciers where recent rock avalanches occurred and at twenty one prehistoric rock avalanches newly identified as having spread over glaciers it seems inadequate to treat such events only as singular extremes or the landslide and glacial processes separately here they are interpreted as contributing to disturbance regime landscapes whose history reflects episodic and regionally specific responses to strong interference among different earth surface processes they generate polygenetic deposits and landforms that are morphologically complex individual episodes involve decades to millennia their numbers and repetition can over ride or redirect geotectonic and climatic conditions it is suggested they are major but hitherto misread or neglected elements of landform evolution in the karakoram and perhaps in other high mountains

examples of multiple rock slope collapses from kofels otz valley austria and western norway abstract this paper describes the effects of large massive rock slope failures on subsequent slope stability three examples of large rock slope failures from the austrian alps and norway demonstrate that failure increases the probability of further collapses at kofels austria a holocene rock slope failure several km3 in size filled the otz valley the morphology of the deposits indicates that at least one subsequent failure occurred along the head scarp of the first failure most likely a slide of similar size debris of the second landslide slid over the older deposits forming the famous kofels frictionite at least three rock slope failures all of them in excess of 106 m3 occurred from the same mountainside within the last 6000 8000 years at tafjord in western norway the most recent of these failures in 1934 triggered a destructive tsunami five large failures with volumes 50 000m3 occurred at ramnefjell norway within 50 years two of them caused considerable damage and a large number of death due to the formation of destructive tsunamis two dimensional finite element models of rock slope stability before and after the kofels and tafjord landslides show that massive rock slope failures produce a irregular slopes parts of which are as steep or steeper than the slope before failure and which represent new zones of instability and b zones of weakness related to slow slope deformation and related cracking

the zymoetz river rock avalanche june 2002 british columbia canada abstract on june 8 2002 the pacific northern gas pipeline in the zymoetz river valley was severed by a large debris flow the event initiated as a rock avalanche in glen falls creek a tributary of the zymoetz river the rock avalanche involved 1 106 m3 of volcaniclastic bedrock and travelled through a complex flow path to finally deposit a large fan in the main zymoetz river approximately half of the debris volume was deposited in the cirque basin at the head of the valley with the rest deposited in the channel and the fan examination of the initiation zone showed a very persistent slightly curved joint set that forms the main sliding surface for the failed block with a dip of 45 and dip direction of 300 a geographic information system gis was used to examine the event and allowed for further interpretation of field data preliminary dynamic analysis indicates that the event reached velocities of up to 34 m s comparison of the zymoetz river rock avalanche zrra with other similar events from the literature indicates that it exhibited similar mobility and velocities as evidenced from the literature these long runout events can cause significant damage and have the potential to be a very high risk as forestry and recreation activities spread further into remote areas

diagenesis of a tight gas sand reservoir upper cretaceous mesaverde group piceance basin colorado abstract the upper cretaceous mesaverde group in the piceance basin western colorado contains thick sections of low porosity low permeability sandstones that are reservoirs for large accumulations of hydrocarbon gas the mesaverde sandstones are lithic arkoses and feldspathic litharenites containing quartz plagioclase variable k feldspar chert and volcanic rock fragments important diagenetic processes that have affected the sandstones include compaction dissolution of feldspar and or alteration to clay precipitation of carbonate and quartz cements precipitation of illite and alteration of detrital clays mixed layer illite smectite porosity is relatively constant a decrease in primary porosity downward is approximately balanced by an increase in secondary porosity with significant microporosity in authigenic and diagenetic clays k feldspar is almost completely absent below 5500 feet 1675 m fibrous illite is relatively abundant above this depth and variable in abundance below the k ar ages of the clays increase with depth from 40 m y at the top of the sampled section to 55 m y at the base indicating illitization of a precursor smectite at approximately the 100 c isotherm samples with abundant fibrous illite have relatively smaller age values mass balance calculations indicate that dissolution of k feldspar illitization of smectite and precipitation of fibrous illite were coupled these reactions suggest the transport of dissolved potassium upward hundreds of feet 100 300 m in the section possibly associated with water driven vertically by the migration of gas

porosity preserving chlorite cements in shallow marine volcaniclastic sandstones evidence from cretaceous sandstones of the sawan gas field pakistan sandstones that have high porosity and permeability at great burial depth and high temperatures are of economic importance because a significant amount of hydrocarbons have been discovered in such reservoirs the sawan gas field with an expected ultimate recovery of more than 1 tcf lies in the middle indus basin the reservoir rocks cretaceous volcaniclastic sandstones of the lower goru formation show very high porosities at a reservoir temperature of 175c and depths of 3000 to 3500 m 9842 to 11 483 ft the sandstones are mostly feldspathic litharenites strongly altered volcanic rock fragments are the most important lithic component the clay fraction consists of fe rich chlorite chamosite and illite diagenetic features such as compaction quartz overgrowths carbonate cements and feldspar dissolution are observed the most distinguishing feature is a double layer of authigenic chlorite lining the pores of the sandstones chlorite additionally occurs as a pore filling cement and as chloritized detrital components all having similar chemical composition the pore lining cement clearly developed in two stages an earlier poorly crystallized and a later better crystallized growth missing rims at grain contacts show that precipitation occurred after an initial stage of compaction but early relative to other diagenetic phases both chlorite rims grew by direct precipitation from pore waters using products derived from volcanic rock fragments in areas with no thin or discontinuous chlorite rims quartz cementation is common well developed chlorite rims inhibited quartz cementation preserved porosities of up to 20 and good permeabilities porosity preserving chlorite cementation in sawan is restricted to sediments of a shallow marine environment

determination of static and dynamic characteristics of microscopic pore throat structure in a tight oil bearing sandstone formation in this study an integrated and practical framework has been developed to quantify the static and dynamic characteristics of microscopic pore throat structure in a tight oil bearing sandstone formation experimentally thin sections were prepared out of core samples collected from a tight formation while corresponding analyses were respectively performed by using the scanning electron microscopy sem and x ray diffraction xrd techniques in addition to pore types and clay minerals the size fraction and distribution of grains were identified and classified pore and throat size distributions were then determined by using pressure controlled mercury injection pmi and rate controlled mercury injection rmi respectively to quantify the changes in microscopic pore throat structure after brine flow tests subsequently displacement experiments of waterflooding and surfactant flooding were performed to determine the upper and lower cutoff value of the movable throat radius rock grains primarily containing fine sand and silt are found to possess complex compositions while both intergranular pores and intragranular dissolution pores are dominant nano throats may have developed in a tight formation due to small radii of pores and throats compared to the pore size distribution throat radius is found to be reduced by 13 9 after brine flow tests while the cutoff value of movable throat can be decreased to 0 019 m from 0 033 m by using a surfactant

the thurwieser rock avalanche italian alps description and dynamic analysis a rock avalanche of about 3 106 m3 detached from the south east flank of the punta thurwieser ridge italian central alps on the 18th of september 2004 due to the characteristics of the moving material i e rock debris ice snow and the path of propagation e g presence of a glacier the mass was able to rapidly cover long distances about 3000 m among the possible causes of the event attention is mainly focused on permafrost degradation and changes in glacier extension due to global warming in the present work the dynamics of the event and the role played by characteristics of the propagation path are numerically investigated with the rash3d code based on a continuum mechanics approach results obtained with two rheological hypotheses frictional and voellmy are compared and discussed in particular it emerges that 1 the use of a voellmy rheology with a reduced friction angle on the glacier is necessary to reproduce the dynamics of the thurwieser event and 2 a lack in knowledge of geometrical and geomechanical information may lead to wrong interpretations of the event and inaccurate calibration of numerical models

36cl terrestrial cosmogenic nuclide dating suggests late pleistocene to early holocene mass movements on the south face of aconcagua mountain and in the las cuevas horcones valleys central andes argentina

substrate deformation associated with the jocotitlan edifice collapse and debris avalanche deposit central mexico abstract an impressive debris avalanche deposit is preserved at jocotitlan volcano in central mexico the northern flank of this edifice collapsed 9690 years b p resulting in a 80 km 2 covering clast supported deposit that lacks substantial matrix fine weak or hydrothermally altered materials the deposit can be subdivided into three morphologically distinct areas which are each accompanied by specific and often unique deformation features in the underlying and adjacent volcaniclastic and lacustrine sediments from these features a complex history of pre and syn avalanche events was reconstructed beginning with edifice spreading on the weak substrate material prior to and in preparation of part of the flank collapse event the north eastern flank in particular was strongly coupled with the deforming substrate material as is still evident in its extensional profile and the unique mode of failure during the catastrophic event resulting in the deposition of what resembles non volcanic blockslide deposits rather than the typical hummocky volcanic debris avalanche morphology this latter type of failure occurred at the north western flank of jocotitlan volcano where few signs of substrate interactions are preserved in a deposit dominated by large conical hummocks in addition to substrate response interaction with pre avalanche topography in the eastern deposit area facilitated the emplacement of a lobe roughly perpendicular to the flank failure direction at apparent high emplacement velocity and with longitudinal ridges as its most striking surface expression

catastrophic rock slope failures and late quaternary developments in the nanga parbat haramosh massif upper indus basin northern pakistan abstract the nanga parbat haramosh massif has some of the greatest relief on earth and highest measured rates of uplift denudation and river incision in bedrock many studies have sought to understand how its morphology relates to geotectonic evolution and glaciations however few catastrophic rock slope failures had been recognised and many of their impacts had been attributed to other processes recently more than 150 of these landslides have been found within a 100 km radius of nanga parbat 8125 m new discoveries are reported east north and west of nanga parbat along the indus streams most generated long run out rock avalanches that dammed the indus or its tributaries some impounding large lakes they initiated episodes of intermontane sedimentation followed by trenching and removal of sediment valley floor features record a complex interplay of impoundment and sedimentation episodes superimposition of streams in pre landslide valley floors and exhumation of buried features these findings depart from existing reconstructions of quaternary events a number of the rock avalanche deposits were previously misinterpreted as tills or moraine and their associated lacustrine deposits attributed to glacial lakes features up to 1000 m above the indus formerly seen as tectonically raised terraces are depositional features emplaced by landslides or erosion terraces recording the trenching of valley fill in landslide interrupted river reaches unquestionably tectonics and glaciation have been important but decisive and misread formative events of the holocene involve a post glacial landslide fragmented fluvial system the latter has kept valley developments in a chronic state of disequilibrium with respect to climatic and geotectonic controls accepted glacial chronologies are put in doubt particularly the extent and timing of the last major glaciation the pace and role processes in the holocene have been seriously underestimated

pore characteristic responses to categories of depositional microfacies of delta lacustrine tight reservoirs in the upper triassic yanchang formation ordos basin nw china abstract primary depositional variations interact with diagenetic modifications to exert strong control on pore networks in tight hydrocarbon reservoirs however the linkage between pore characteristics and depositional microfacies remains enigmatic which restricts the prediction of high quality reservoir distributions the continental tight reservoirs of the yanchang formation in the ordos basin are targeted to clarify and estimate the sensitivity of pore characteristics to depositional microfacies a multi methodical approach utilizing petrographic assessments logging evaluations digital imaging analyses and high pressure mercury intrusion experiments enables us to reveal the high microheterogeneity of pore types pore size distribution and pore fractal features the results identified the microfacies including distributary channels dcs mouth bars mbs interdistributary bays ibs sheet sands sss turbidite fans tfs shallow lacustrine mudstones slms and semi deep lacustrine mudstones sdlms from the chang 8 to chang 6 members dominated by residual intergranular pores and microfractures the main storage spaces of the dc and mb microfacies are within mesopores which provide 62 92 and 81 of the total pore volume respectively however the micropores that are mainly composed of clay intercrystalline pores and feldspar dissolved pores provide 55 70 52 62 and 53 80 of the total pore volume for the ib slm and sdlm microfacies respectively in addition the pore fractal dimension results indicate that the mesoporous structure of the argillaceous microfacies ib slm and sdlm is more heterogeneous than that of the arenaceous microfacies dc mb and tf therefore the dominant reservoir spaces of the different depositional microfacies are distributed over diverse pore radius ranges and the varying degrees of mesoporous development are a crucial factor affecting the reservoir capacity moreover the fractal dimensions have a significant negative correlation with pore volume in the meso micropore range characterized by lower pore sorting coefficients broader skewness and more abundant rigid siliceous grains the arenaceous microfacies with lower fractal dimensions and higher pore volume have better reservoir capacity than argillaceous microfacies that are rich in ductile minerals microscopic observations show that the muddier reservoirs of interdistributary bays and lacustrine mudstones are more susceptible to pore filling chlorite and illite which can deteriorate the reservoir quality these results indicate that the controlling effect of depositional microfacies on pore characteristics is fundamentally caused by differences in mineralogical composition and depositional texture and these results could provide new insights into the mechanisms of microfacies controls on reservoir quality

entrainment of debris in rock avalanches an analysis of a long run out mechanism many rock avalanches entrain and liquefy saturated soil from their paths evidence for this includes mud displaced from the margins of rock avalanche deposits substrate material smeared along the base of deposits extrusion of liquefied soil upward through the deposits and increases of volume a hypothesis first suggested in 1881 and since reinforced by several authors suggests that entrainment of substrate material increases mobility although the process has been discussed in the literature for more than 100 years few detailed and quantitative descriptions exist the main purpose of this paper is to describe two recent cases from british columbia canada where rockslides entrained substrate on a very large scale influencing the character of the events estimated volume balance curves based on detailed field mapping are provided for both cases dynamic analyses are carried out using a numerical model and using the same set of rheological parameters the mechanism of material entrainment and displacement is discussed the data suggest that rapid rock failures entraining very large quantities of saturated substrate material represent a special type of landslide transitional between rock avalanche and debris avalanche many rock avalanches can thus be seen as end members of a continuum of phenomena involving rock failure followed by interaction with saturated substrate

diagenesis in porosity evolution of opening mode fractures middle triassic to lower jurassic la boca formation ne mexico abstract opening mode fractures joints in middle triassic to lower jurassic la boca formation sandstones northeastern mexico have patterns of fracture porosity mineral fill structures and size distributions not previously described from outcrop patterns match those found in cores from many basins we used aperture measurements along lines of observation scanlines fracture trace maps petrography high resolution scanning electron microscope sem based cathodoluminescence and fluid inclusions to characterize fracture populations open fractures are lined by quartz that precipitated while fractures were opening whereas sealed fractures additionally contain calcite deposited after fractures ceased opening large fractures and arrays of contemporaneous microfractures have consistent power law aperture size scaling over approximately three orders of magnitude our results imply that open fractures and fracture sizes depend on diagenetic state the interplay of fracture mechanics and diagenetic history is a determinant on effective porosity within fractures and thus open fracture persistence connectivity and fluid flow

aggregate properties of fracture populations abstract empirical studies indicate that the individual attributes of both faults and extension fractures follow power law scaling aggregate properties of fracture populations are important in a variety of problems and can be specified in terms of the scaling parameters of individual fracture attributes development of an expression for an aggregate property requires consideration of a number of independent factors including the topologic dimension of the aggregate property the topologic dimension of sampling and the possibility of scaling changes for fractures that span some mechanically significant layer the riemann zeta function provides an alternative to integration for the analytical and numerical solution of aggregate problems previous work regarding aggregate properties of fracture populations has focused on the strain due to faulting new expressions are developed here for other aggregate properties of interest fracture surface area fracture porosity fracture permeability and shear wave anisotropy a general characteristic of these aggregate properties is that for most values of scaling exponents the aggregate properties are dependent on the size of the sampling domain this implies that the aggregate properties are scale dependent additionally it appears that fracture surface area is concentrated in the smallest fractures of many populations fracture porosity is concentrated in the largest fractures of most populations but not as strongly as fracture permeability which probably derives almost entirely from the largest fractures in populations

how clay grain coats inhibit quartz cement and preserve porosity in deeply buried sandstones observations and experiments observations and hydrothermal experiments were used to derive new information about how clay grain coats inhibit quartz cement and preserve porosity in deeply buried sandstones samples of deeply buried porous sandstones with different types of clay coats were split in two coats removed from one of each pair of splits and grain surfaces inspected with scanning electron microscopy quartz grains in a fluvial deltaic sandstone buried to 115c had no visible authigenic quartz on grain surfaces cleaned of diagenetic chlorite coats though well developed overgrowths occurred on nearby naturally uncoated grains however in similar sandstones buried to 164c quartz grain surfaces exposed by chlorite coat removal were covered with small 5 m mainly anhedral syntaxial quartz overgrowths similar overgrowths were observed under various detrital and diagenetic clay coats in porous eolian sandstones buried to temperatures up to 215c we conclude that clay coats may retard quartz nucleation at moderate temperatures but at high temperatures many coats permit quartz nucleation and preserve porosity by limiting cement growth to investigate cement growth limitation mechanisms samples with coats removed were subjected to quartz cementing conditions in a hydrothermal reactor during experiments the naturally occurring small overgrowths on clay cleaned grains coalesced and grew suggesting that clay particles in coats inhibit cement growth by forming barriers to early overgrowth coalescence although the fraction of grain surface coverage is the primary control on cement inhibition by coats cement growth interference textures vary with coat type providing a mechanism by which coat composition may be a secondary control on inhibitory effectiveness in deeply buried sandstones quartz cement can fill significant microporosity within diagenetic chlorite coats potentially affecting mechanical and petrophysical rock properties

baroclinic volume transport in the southern ocean abstract a new map of the baroclinic volume transport to 3000 m has been produced for the southern ocean making use of all available historic hydrographic data in the area the map complements the geopotential height anomaly map of gordon et al 1978 the construction of the transport map was facilitated by the strong vertical coherence of the flow found for the whole ocean area

fractures in sandstone reservoirs with ultra low permeability a case study of the upper triassic yanchang formation in the ordos basin china the upper triassic yanchang formation in the ordos basin central china is a typical sandstone reservoir with an ultra low permeability high angle tectonic fractures and diagenetic fractures such as near horizontal bedding fractures intragranular fractures and grain boundary fractures are abundant fractures are major pathways and enhance fluid flow in sandstone reservoirs with ultra low permeability because of their weak lateral continuity and their small apertures under lithostatic pressure bedding fractures make a relatively small contribution to the overall permeability of reservoirs as they are both of small size and low permeability intragranular fractures and grain boundary fractures mainly improve the connectivity of reservoirs by connecting the matrix pores high angle tectonic fractures control the fluid movement in the ultra low permeability reservoirs under the effect of different successive tectonic stress fields four assemblages of high angle tectonic fractures developed in the sandstone reservoirs under the present day stress differently oriented fractures have different connectivities apertures and permeabilities the northeast southwest fractures parallel to the maximum principal stress have a good connectivity large apertures and a high permeability forming the dominant flow paths knowledge of these paths can be used for optimizing well placement because of their sensitivity to pressure fractures in different directions will show varying apertures as the formation pressure decreases therefore the permeability of the fractures of different orientations and its impact on reservoirs vary at different developmental stages

cosmogenic cl 36 dating of postglacial landsliding at the storr isle of skye scotland major postglacial rock slope failures are a common feature of the scottish highlands and other mountainous areas that were deglaciated at the end of the pleistocene but evaluation of the causes and triggers of failure has been hindered by a lack of reliable dating evidence we report the result of a pilot study designed to establish the absolute age of a large postglacial rotational rockslide at the storr on the isle of skye scotland using 36cl surface exposure dating exposure ages of 6 3 0 7 cal ka bp and 6 6 0 8 cal ka bp were obtained for rock samples from two separate landslide blocks giving an overall age estimate of 6 5 0 5 cal ka bp for rock slope failure at this site this date is consistent with ams radiocarbon dating of windblown sand derived from the failure scarp and with previous inferences based on relative dating evidence concerning an early holocene age for most rock slope failures in the scottish highlands the long time lag 7 ka between deglaciation and failure sugge

neotectonics and catastrophic failure of mountain fronts in the southern intra andean puna plateau argentina new cosmogenic nuclide exposure ages of rock avalanche deposits in front of sierra laguna blanca in the arid argentine puna plateau demonstrate the effects of westward propagation of reverse faulting and the influence of active faulting on slope oversteepening and subsequent gravitational collapse the 21 ne exposure ages of 8 superposed landslides with volumes 0 3 km 3 are between ca 150 and 430 ka and indicate an average recurrence interval of large gravitational mountain front failures of 27 5 k y for the ultimate 7 landslides landsliding did not occur after 150 ka along this sector of the sierra laguna blanca the termination of landsliding activity correlates with reverse fault propagation into the piedmont area of the sierra laguna blanca the exposure age of ca 130 ka of a tectonically uplifted terrace postdates initiation of fault activity in the piedmont region and the fault scarp height of 120 m indicates important continued uplift in the piedmont no further offsets occurred at the mountain front due to this lack of tectonic activity at the mountain front no further collapse has occurred indicating that in this environment catastrophic mountain front failure is mainly controlled by tectonically driven slope oversteepening

subaqueous rock avalanche deposits exposed by post glacial isostatic rebound innfjorddalen western norway abstract this paper presents a detailed description of deposits and landforms of multiple rock avalanches in western norway one of which fell onto water saturated sediments in innfjorddalen below the former water level deposits of the latter are now exposed on the valley floor due to post glacial isostatic rebound at least three rock avalanches from the same source at grafonnfjellet mountain have occurred during late glacial and post glacial time and their deposits are distributed over an area of 1 44 km 2 in the valley these rock avalanches have volumes of 15 1 10 6 m 3 5 4 10 6 m 3 and 0 3 10 6 m 3 and yielded cosmogenic radionuclide 10 be ages of 14 3 1 4 ka 8 79 0 94 ka and 1 028 0 380 ka respectively the youngest event dates within uncertainty limits to a historic rock avalanche in the year 1611 12 ce the rock avalanches formed a stratified succession of deposits the rock avalanche deposits 1 38 m 2 have lobate forms have frontal rims and parallel ridges extend across the valley floor and up the opposite slope and form dams on the valley floor isolated hills comprised of rock boulders 0 61 km 2 interpreted to be toma hills are disconnected from the main rock avalanche deposits by a 520 m wide zone of deformed valley fill sediments trenches and a ground penetrating radar survey of these deposits indicate large scale deformation or liquefaction numerical runout modeling of the rock avalanches with the code dan3d supports the interpretation of their landforms and sources and highlights their runout behavior

modelling rock avalanche propagation onto glaciers abstract ice rock avalanches which occur in glacial environments are controlled by the presence of snow and ice in the moving material and by possible propagation onto icy basal surfaces all these factors contribute to enhancing the flow mobility mixing with ice and snow hampers block collisions and favours dense flow behaviour ice melting reduces granular friction by saturation of the basal material and fluidization effects propagating onto glaciers offers a smooth surface with low shear resistance this work is a review of the best documented ice rock avalanches and focuses on evaluating their mobility for hazard analysis purposes by providing a set of calibrated cases the rock avalanches have volumes ranging from 5 10 6 m 3 to 25 10 6 m 3 we replicate these events by using sph and fem numerical methods assuming frictional and voellmy basal rheologies the voellmy rheology best performs at replicating the landslide propagation among the back analyzed cases the frictional coefficient ranges in the interval 0 03 0 1 the turbulent coefficient within 1000 m s 2 2000 m s 2 the bulk basal friction angle ranges within 2 75 and 14 with values inversely related to event volumes forward selection of the basal friction angle based on event volume allows the replication of the mount cook ice rock avalanche predicting a maximum runout which is less than 4 larger than observed in the perspective of forward modelling large uncertainty is related to the reconstruction of the post event topographies particularly for the sliding surface mixing with ice and snow reduces basal friction proportionally to ice and snow content pure ice has a basal friction which is reduced by about 75 than basal friction of pure rock melting of ice during rock avalanche propagation has been evaluated for the sherman event the frictional heat generated at the glacier surface results in the melting of 86 2 5 9 kg m 2 which could have contributed to a minimum 20 35 10 reduction of the material friction angle through the sole pore pressure generation within a 40 and 20 cm thick shear layer respectively the largest uncertainty is related to the area of contact between rock and ice

numerical modelling of entrainment deposition in rock and debris avalanches abstract rock and debris avalanches as well as debris flows are characterized by peculiar behaviour influenced by geometry of the initial failure surface topography involved materials involved and water content during their motion rock avalanches can entrain large volumes of sediments both in a dry and in a saturated state entrained dry material has generally the consequence to reduce the total landslide runout whereas entrainment of almost saturated material can have more complex consequences we use a finite element code to simulate the motion of a moving landslide mass on materials with different properties and along very sharp topographies erosion and deposition can be modelled as well as interaction with obstacles of different characteristics we present two examples of the modelling problems and capabilities we simulated the runout of a rock avalanche on a ground formed by alluvial material under dry and saturated conditions this material can be entrained and plowed by the impacting and running rock avalanche material sensitivity of the erosion and transport mechanisms has been analysed by performing different analyses the simulated case study is the 6 10 5 m 3 arvel rock avalanche 1922 switzerland for which a reliable set of pre and post failure observations is available final geometry mass redistribution velocities and runup are used to validate the model capabilities and study the effects of different material properties

a method to detect natural fracture strike in sandstones in siliciclastic hydrocarbon reservoir rocks economic gas and oil production may depend on the attributes of natural fractures and with the advent of horizontal drilling fractures are increasingly exploration and development targets yet reliable information on such key fracture attributes as orientation strike is sparse because few fractures intersect vertical well bores this paper describes how fracture strike can be documented on a bed by bed basis even in well bores where few or no visible fractures are directly sampled quartz lined opening mode microfractures lengths of microns to millimeters in quartz cemented sandstones commonly are not visible using standard petrographic methods but systematic mapping of these microfractures is possible using photomultiplier based electron beam induced luminescence scanned cathodoluminescence imaging as shown by observations primarily from three natural gas plays and one oil play in the united states microfracture strike is a good guide to the strike of large fractures macrofractures that formed concurrently because microfractures are widespread and small specimens can be used to get accurate fracture strike data this approach can be applied to samples obtained from wireline conveyed rotary drilled sidewall coring devices as well as to samples from full diameter core

application of back scattered electron microscopy to the quantification of clay mineral microporosity in sandstones abstract computer assisted image analysis of back scattered electron bse micrographs of petrographic sections is useful for the quantification of clay mineral microporosity in sandstones authigenic clay minerals from north sea clastic reservoirs generally have higher microporosities than detrital clay minerals diagenetic kaolinite has microporosities varying from 25 to 50 diagenetic chlorite has a generally uniform grain coating texture and microporosities of about 50 dispersed diagenetic illitic clays are difficult to characterize using this method because their delicate morphology is susceptible to damage during sample preparation despite this limitation the analytical data indicate a minimum microporosity of 63 for dispersed illitic clays analytical data for clay rich detrital lasts have much lower microporosity values of about 10 interpretation of images from detrital clasts is complicated by the effects of sample preparation

microtextures in mudrocks as revealed by backscattered electron imaging abstract this report is one of the first attempts to examine polished mudrock sections with backscattered scanning electron microscopy bse in order to image characterize and understand their microtextures as well as to help reconstruct sedimentary and diagenetic environments over 180 polished thin sections of mudrocks from precambrian to early middle tertiary age were examined in this study using bse seven common microtextures have been identified in the samples examined with bse microlaminations fossil forms pyrite clay minerals and micas chemical and physical alteration glauconization and porosity microlaminations have been examined at the single grain level foraminifera in the gulf coast tertiary reflect a sequence of preservation relations from shallow depths to a few thousand meters fecal pellets in a black mudrock from spitsbergen of upper jurassic age contain what appear to be well preserved fossil vertebrates replaced by pyrite the chemical and physical variations within micas and clay minerals seem to be the result of selective alteration along cracks and defects in the minerals and these have been imaged mineral growth and dissolution at the submicron level can be imaged particularly in the clay minerals quartz and feldspar glauconite growth conditions geochemical complexities of carbonate formation and the size shape and orientation of micron sized pore spaces in shales have been obtained thus the microtextural analysis of mudrocks not only is possible but can be accomplished in great detail with existing techniques

microfracturing in the upper triassic sichuan basin tight gas sandstones tectonic overpressure and diagenetic origins the western sichuan basin located at the front of the longmen mountain in the western sichuan province of china is a foreland basin formed in the late triassic the upper triassic xujiahe formation in the basin is an ultralow permeability and low porosity tight gas sandstone reservoir microfractures such as intragranular microfractures grain edge microfractures and transgranular microfractures are abundant in the tight sandstones microfractures improve storage and permeability and impact distribution of natural gas microfractures reflect tectonic overpressure and diagenetic origins using quartz and calcite fluid inclusions and burial history tectonic microfractures were determined to be formed at the end of the triassic the end of the cretaceous and the end of the neogene early pleistocene microfractures related to overpressure being tension microfractures are commonly filled with bitumen and were formed at the middle to late cretaceous when the maximum pressure coefficients were 1 6 to 2 1 in the middle to late neogene the pressure coefficient was reduced to less than 1 3 because of fault activity and tectonic uplift in the southwestern sichuan basin and these tension microfractures closed and were filled with calcite the transition of stress state from compression to tension by overpressure is the reason that tension microfractures were formed in the compression setting diagenetic fractures were formed at the end of the late triassic to jurassic under intense compaction grain crushing crackle fractures in quartz and cleavage fractures in feldspar formed intragranular microfractures some transgranular microfractures caused by diagenesis are along the bedding plane and parallel to the directional mineral grains

catastrophic landslides glacier behaviour and moraine formation a view from an active plate margin the influence of large bedrock landslides rock avalanches on the behaviour of glaciers is incompletely recognised here we present an example from an active tectonic margin in south island new zealand where large earthquakes leave a significant imprint on glacial records we demonstrate that terminal moraines on the western side of the southern alps record both ordinary i e climate driven and landslide initiated glacial advances following consideration of the processes involved in rock avalanche initiated moraine construction we suggest ways of determining the nature of the advance that built the terminal moraine the implications of these observations are important in breaking the conventional linkage of individual terminal moraines with climate forcing

the impact of diagenesis on the heterogeneity of sandstone reservoirs a review of the role of depositional facies and sequence stratigraphy diagenesis exerts a strong control on the quality and heterogeneity of most clastic reservoirs variations in the distribution of diagenetic alterations usually accentuate the variations in depositional porosity and permeability linking the types and distribution of diagenetic processes to the depositional facies and sequence stratigraphic framework of clastic successions provides a powerful tool to predict the distribution of diagenetic alterations controlling quality and heterogeneity the heterogeneity patterns of sandstone reservoirs which determine the volumes flow rates and recovery of hydrocarbons are controlled by geometry and internal structures of sand bodies grain size sorting degree of bioturbation provenance and by the types volumes and distribution of diagenetic alterations variations in the pathways of diagenetic evolution are linked to 1 depositional facies hence pore water chemistry depositional porosity and permeability types and amounts of intrabasinal grains and extent of bioturbation 2 detrital sand composition 3 rate of deposition controlling residence time of sediments at specific near surface geochemical conditions and 4 burial thermal history of the basin the amounts and types of intrabasinal grains are also controlled by changes in the relative sea level and therefore can be predicted in the context of sequence stratigraphy particularly in paralic and shallow marine environments changes in the relative sea level exert significant control on the types and extent of near surface shallow burial diagenetic alterations which in turn influence the pathways of burial diagenetic and reservoir quality evolution of clastic reservoirs carbonate cementation is more extensive in transgressive systems tract tst sandstones particularly below parasequence boundaries transgressive surface and maximum flooding surface because of the abundance of carbonate bioclasts and organic matter bioturbation and prolonged residence time of the sediments at and immediately below the sea floor caused by low sedimentation rates which also enhance the formation of glaucony eogenetic grain coating berthierine odinite and smectite formed mostly in tst and early highstand systems tract deltaic and estuarine sandstones are transformed into ferrous chlorite during mesodiagenesis helping preserve reservoir quality through the inhibition of quartz cementation the infiltration of grain coating smectitic clays is more extensive in braided than in meandering fluvial sandstones forming flow barriers in braided amalgamated reservoirs and may either help preserve porosity during burial because of quartz overgrowth inhibition or reduce it by enhancing intergranular pressure dissolution diagenetic modifications along sequence boundaries are characterized by considerable dissolution and kaolinization of feldspars micas and mud intraclasts under wet and warm climates whereas a semiarid climate may lead to the formation of calcrete dolocrete cemented layers turbidite sandstones are typically cemented by carbonate along the contacts with interbedded mudrocks or carbonate mudstones and marls as well as along layers of concentration of carbonate bioclasts and intraclasts commonly hybrid carbonate turbidite arenites are pervasively cemented proximal massive turbidites normally show only scattered spherical or ovoid carbonate concretions improved geologic models based on the connections among diagenesis depositional facies and sequence stratigraphic surfaces and intervals may not only contribute to optimized production through the design of appropriate simulation models for improved or enhanced oil recovery strategies as well as for co2 geologic sequestration but also support more effective hydrocarbon exploration through reservoir quality prediction

influence of runout path material on emplacement of the round top rock avalanche new zealand factors influencing the distance a disintegrating rock mass travels as it spreads across the landscape after detaching from a slope include the volume and mechanical properties of the material local topography and the materials encountered in the runout path here we investigate the influence of runout path material on the mobility and final morphology of the round top rock avalanche deposit new zealand this rock avalanche of mylonitic schist ran out over a planar surface of saturated fluvial gravel longitudinal ridges aligned radial to source grade into smaller aligned hummocks and digitate lobes in the distal reach soils and river gravels in the runout path are found bulldozed at elongate ridge termini where they formed local obstacles halting avalanche motion at these locations thus aiding development of prominent elongate ridges on the deposit further travel over the disrupted substrate led to avalanche substrate mixing at the base of the debris mass field observations combined with subsurface geophysical investigations and laboratory analogue models illustrate the processes of substrate deformation features at the round top rock avalanche copyright 2009 john wiley sons ltd

diagenetic history and reservoir quality of tight sandstones a case study from shiqianfeng sandstones in upper permian of dongpu depression bohai bay basin eastern china abstract the upper permian shiqianfeng sandstones located in the dongpu depression bohai bay basin china are fluvio lacustrine deposits and have high content of pore filling volcanic dust average 7 93 vol this study focuses on diagenetic processes and reservoir quality of the tight sandstones based on different lithofacies an integrated approach such as core observation x ray diffraction scanning electron microscopy cathode luminescence stable isotope analysis of carbon and oxygen compositions electron microprobe analysis and fluid inclusion analysis were utilized the tight sandstones consist of subarkose and lithic subarkose and have undergone significant diagenetic events including compaction quartz cementation carbonate cementation mainly calcite and ferrocalcite and formation of authigenic clay minerals i e chlorite rims kaolinite and mixed layer illite smectite the volcanic dust altered with increase of burial depth resulting in the production of abundant silicic materials and depletion of metallic ions i e fe 2 mg 2 ca 2 and mn 2 this process formed subhedral micro quartz pore filling authigenic quartz smectite and chlorite rims during the early diagenetic stage early phase carbonate cements calcite ferrocalcite occurred in several samples they were also influenced by volcanic dust alteration resulting in intrusive of fe 2 and high contents of mn 2 average 12 5 mol further alteration of volcanic dust at the mesogenetic stage can result in cementation of kaolinite and euhedral micro quartz quartz overgrowth developed because of smectite to illite reactions and the alteration of volcanic dust late phase carbonate cements dolomite and ankerite are rare the present low porosity average 6 17 vol and permeability average 0 198 md of the shiqianfeng sandstones mainly resulted from intense compaction diverse cementation and pore filling of volcanic dust as strong hydrodynamic conditions of pore water modification of reservoir quality in the conglomeratic sandstone and gritstone lithofacies mainly distribute in braided channel occurred by alteration of volcanic dust thick braided channel at the high structural position should be the focal point for the future exploration

catastrophic landslides and their effects on the upper indus streams karakoram himalaya northern pakistan abstract the paper examines the nature and geomorphic influences of deposits from rock avalanches that obstruct rivers most of the 115 rockslide rock avalanche events identified in the karakoram himalaya straddled one or more stream valleys at least 73 of these landslides formerly dammed the indus or its tributaries upstream of the barriers remnants exist of once very extensive lacustrine deposits the stability and long term survival of dams from large rock avalanches is addressed and the reasons for the gradual or phased rather than catastrophic and sudden breaching case histories emphasise the erosional and depositional forms associated with the barriers they are reconstructed in terms of the emplacement and properties of the deposits from rock avalanches and the response of the river to interruption by them these barriers have exerted a substantial control over stream response and development for most of the holocene at least today they are associated with distinctive features of channel form and thalweg river terrace systems intermontane sediment sinks and sources and local erosional forms in bedrock more broadly the landslide barriers have created a naturally fragmented river system deposition and erosion in the lower few tens or hundreds of meters of the upper indus stream valleys have been dominated by epicycles of aggradation trenching and downcutting that mainly reflect the scale timing and history of each barrier the landforms involved are only indirectly related to the late glacial and paraglacial conditions that have hitherto been regarded as the main explanation

alluvial deposits liquefied by the flims rock slide abstract the origin of the bonaduz gravel switzerland in the vicinity of the large holocene flims rock slide deposits has been discussed for a century the internal structure shows many features that imply transport as an over sized mud debris stream this flow of gravel sand and fines must have been triggered by the mobilisation of the valley alluvium by the impact of the rock slide the mobilised mud with a volume of several 100 million m 3 must have had enormous transport capacities as large units of loose material were transported over kilometres without breaking apart accordingly the shear forces in the flow must have been negligible similar features have been found at several other sites in the alps all in the vicinity of large rock slides our interpretation of these sediments as catastrophic mass movement deposits suggests that such events could happen again also in other parts of the world

transferability of a calibrated numerical model of rock avalanche run out application to 20 rock avalanches on the nuussuaq peninsula west greenland long run out rock avalanches are one of the most hazardous geomorphic processes and risk assessments of the potential threat they pose are often reliant on numerical modelling of their potential run out distance the development of such models requires a thorough understanding of past flow behaviour inferred from deposits emplaced by previous events despite this few records exist of multiple rock avalanches that occurred in conditions sufficiently consistent to develop a set of more generalised and hence transferrable rules we conduct field and imagery based mapping and use numerical modelling to investigate the emplacement of 20 adjacent rock avalanches on the southern flanks of the nuussuaq peninsula west greenland the rock avalanches run out towards the vaigat strait and are sourced from a range of coastal mountains of relatively uniform geology we calibrate a three dimensional continuum dynamic flow code volcflow with data from a modern well constrained event that occurred at paatuut ad 2000 the best fit model assumes a constant retarding stress with a collisional stress coefficient simulating run out to within 0 3 of that observed this calibration was then used to model the emplacement of deposits from five other neighbouring rock avalanches before simulating the general characteristics of a further 14 rock avalanche deposits on simplified topography our findings illustrate that a single calibration of volcflow can account for the observed deposit morphology of a uniquely large collection of rock avalanche deposits emplaced by a series of events spanning a large volume range although the prevailing approach of tuning models to a specific case may be useful for detailed back analysis of that event we show that more generally applied models even using a single pair of rheological parameters can be used to model potential rock avalanches of varied volumes in a region and therefore to assess the risks that they pose

diagenetic alteration and its control on reservoir quality of tight sandstones in lacustrine deep water gravity ﬂow deposits a case study of the yanchang formation southern ordos basin china abstract the tight oil sandstone reservoir of the upper triassic yanchang formation is one of the main targets for hydrocarbon exploration in the ordos basin china sandstones of the upper triassic yanchang formation within lacustrine deep water gravity ow deposits are characterized by ultralow porosity ultralow permeability and complex diagenetic alterations and sedimentary lithofacies however the diagenetic alterations and their controls on the reservoir quality of the chang 6 tight sandstones remain poorly understood this study integrated a variety of techniques such as casting thin section analysis scanning electron microscopy sem back scattered electron imagery bse x ray diffraction xrd cathodoluminescence cl microscopy and fluid inclusion to investigate the lithofacies diagenetic history and diagenetic intensity and also evaluate their controls on reservoir quality the research results indicated that the chang 6 sandstones exhibit variable intensity of diagenetic alterations among the various lithofacies which leads to variable reservoir quality mechanical compaction was the most important factor reducing primary porosity sandstones of the ss lithofacies siltstone to very fine grained sandstones with graded bedding or ripple laminations showed the highest loss of primary porosity carbonate cements were commonly present in sandstones of the sc fine grained and cross bedded sandstones and sm fine grained and massive sandstones lithofacies near the sandstone mudstone bounding surface sandstones with more authigenic illite rims were able to resist compaction to some extent and were favorable to the preservation of porosity however abundant pore filling illite aggregates commonly bridged pore throats causing a significant reduction in reservoir quality feldspar dissolution porosity leads to a slight enhancement in reservoir quality intergranular pores and feldspar dissolution pores are most abundant in the sandstones away from the sandstone mudstone bounding surface of the sc lithofacies resulting in the best reservoir quality which is followed by sandstones of the sm lithofacies ultimately four evolution patterns of diagenetic alterations that formed best moderate or poor reservoir quality were summarized by linking diagenetic alterations to lithofacies the research results are conducive to the evaluation of reservoir quality and to understanding the genetic mechanisms of tight sandstones so they should facilitate hydrocarbon exploration and production in similar lacustrine deep water gravity ow reservoirs

depositional and diagenetic controls on the reservoir quality of lower cretaceous pendencia sandstones potiguar rift basin brazil the quality of the reservoirs of the lower cretaceous pendencia formation of the potiguar basin northeastern brazil is directly controlled by depositional facies related carbonate cementation and compaction the study of the interplay of these processes in the reservoirs offers an opportunity to unravel the diagenetic patterns of clastic sequences in interior rifts and in particular the role of carbonate cementation in poorly understood continental systems the pendencia formation is a thick sequence of fan deltaic fluvial deltaic turbiditic and lacustrine sandstones conglomerates and shales deposited during the rift stage of the basin the sandstones are predominantly arkoses average q49f40l11 with subordinate plutonic and volcaniclastic feldspathic litharenites compaction and cementation had similar importance in the destruction of porosity with a dominance of cementation in the turbidites and of compaction in the fluvial deposits carbonate cementation in pendencia reservoirs increases progressively with depth and is facies controlled eodiagenetic nonferroan calcite i d18opdb 10 7 to 4 0 d13cpdb 17 5 to 8 5 mesodiagenetic rhombohedral ferroan dolomite ankerite d18opdb 9 3 to 3 9 d13cpdb 1 7 to 1 1 and ferroan calcite ii d18opdb 17 2 to 6 8 d13cpdb 13 6 to 2 3 were precipitated at three distinct temperature intervals calculated from the d18o values 21 to 58 c 70 to 79 c and 85 to 150 c respectively according to the d13c values dissolved carbonate for calcite i was derived from oxidation and methanogenic fermentation of organic matter and from methane oxidation ferroan mesogenetic cements were derived from thermal decarboxylation of organic matter the shales were a major source of dissolved begin page 1720 carbonate as indicated by the isotopic similarity between their calcite d13cpdb 0 2 to 1 8 87sr 86sr 0 719 and most cements in the sandstones and by the peripheral cementation along the contacts of interbedded sandstones as a result of this cementation pattern thin turbiditic and deltaic sandstone beds are pervasively cemented the best reservoir quality potential is encountered in the partially cemented fluvial sandstones at moderate depths deltaic and turbiditic sandstones are more pervasively cemented by carbonate derived from the interbedded shales alluvial fan conglomerates and sandstones were flushed by telogenetic meteoric waters close to the borders of the basin and to the proximity to the postrift unconformity however porosity enhancement was very limited due to the precipitation of kaolinite and the intense compaction related to the compositionally immature detrital framework

coastal cliffs rock slope failures and late quaternary transgressions of the black sea along southern crimea abstract rock slope failures represent a significant hazard along global coastlines but their chronology remains poorly documented here we focus on the geomorphology and chronology of giant rockslides affecting the crimean mountains along the black sea coast geomorphic evidence suggests that high 100 m limestone cliffs flanking the southern slopes of the crimean mountains are scarps of rockslides nested within larger deep seated gravitational slope deformations dsgsds such pervasive slope failures originated due to lateral spreading of intensively faulted late jurassic carbonate blocks moving atop weak plastic late triassic flysch and tuff layers by introducing a dating strategy relying on the combination of the uranium thorium dating u th of exposed calcareous speleothems covering the landslide scarps with the 36cl exposure dating of rock walls we are able to approximate the time interval between the origin of incipient crevices and the final collapse of limestone blocks that exposed the cliff faces for the three representative large scale rockslides between the towns of foros and yalta the initiation of the dsgsds as evidenced by the widening of crevices and the onset of speleothem accumulation was 300 ka bp but the recent cliff morphology along the coast is the result of late pleistocene holocene failures spanning 20 0 5 ka bp the exposures of rockslide scarps occurred mostly at 20 15 8 5 4 and 2 0 5 ka which substantially coincide with the last major black sea transgressions and or more humid holocene intervals our study suggests that before ultimate fast and or catastrophic slope failures the relaxation of rock massifs correlative with karstification cracks opening and incipient sliding lasted on the order of 104 105 years rapid late glacial holocene transgressions of the black sea likely represented the last impulse for the collapse of limestone blocks and the origin of giant rockslides simultaneously affecting the majority of the sw coast of the crimean peninsula