polybessurus like fossils as key contributors to permian triassic boundary microbialites in south china abstract massive occurrences of microbialites near the permian triassic boundary have been interpreted as being due to benthic microbial proliferation in unusual marine conditions after the end permian mass extinction here we present large populations of polybessurus like microfossils in the microbialites of the south china craton to reveal their morphological structures growth patterns and ecological implications these distinctive microfossils are composed of layered stalks and spherical endpoints the spheroids 20 40 m in diameter comprising external thin micritic walls and internal sparry parts are interpreted as coccoid cyanobacteria the stalks consist of multiple stacked cup micritic envelopes consisting of micron sized magnesian calcite dolomite grains and are catalogued as calcified remains of coccoid cyanobacterial extracellular polymeric substances eps early microbially mediated calcification of eps increased the preservation potential of microfossils the microfossils stand upright as coccoid unicells supported by the highly unidirectional secretion of eps revealing their benthic behaviours the successively secreted eps lift the cells away from the substrate expanding their ecological niches to gain more sunlight for photosynthesis in the barren marine floor the distinctive polybessurus like microfossils can be viewed both in laminae of stromatolites and in spotted digitate clots of thrombolites suggesting their critical roles in microbe dominated reefs in the aftermath of the end permian mass extinction the morphological features and growth patterns of the polybessurus like fossils resemble their proterozoic counterpart polybessurus bipartitus fairchild ex green et al 1987 the widespread polybessurus like fossils in the permian triassic boundary microbialites of the south china craton suggest pervasive retrogressive ecosystems on carbonate platforms after the largest extinction event during the earth s history

scale invariance of soil moisture variability and its implications for the frequency size distribution of landslides abstract power spectral analyses of soil moisture variability are carried out from scales of 100 m to 10 km on the microwave remotely sensed data from the washita experimental watershed during 1992 the power spectrum s k has an approximate power law dependence on wave number k with the exponent 1 8 this behavior is consistent with the behavior of a stochastic differential equation for soil moisture at a point and it has important consequences for the frequency size distribution of landslides we present the cumulative frequency size distributions of landslides induced by precipitation in japan and bolivia as well as landslides triggered by the 1994 northridge california earthquake large landslides in these regions despite being triggered by different mechanisms have a cumulative frequency size distribution with a power law dependence on area with an exponent ranging from 1 5 to 2 we use a soil moisture field with the above statistics in conjunction with a slope stability analysis to model the frequency size distribution of landslides in our model landslides occur when a threshold shear stress dependent on cohesion pore pressure internal friction and slope angle is exceeded this implies a threshold dependence on soil moisture and slope angle since cohesion pore pressure and internal friction are primarily dependent on soil moisture the cumulative frequency size distribution of domains of shear stress greater than a threshold value with soil moisture modeled as above and topography modeled as a brownian walk is a power law function of area with an exponent of 1 8 for large landslide areas this distribution is similar to that observed for landslides the effect of strong ground motion from earthquakes lowers the shear stress necessary for failure but does not change the frequency size distribution of failed areas this is consistent with observations this work suggests that remote sensing of soil moisture can be of great importance in monitoring landslide hazards and proposes a specific quantitative model for landslide hazard assessment

stromatolites near the permian triassic boundary in chongyang hubei province south china a geobiological window into palaeo oceanic fluctuations following the end permian extinction abstract stromatolites just after the end permian extinction are exceptionally well developed in the chongyang area of hubei province south china the stromatolites include endolithic coccoidal microbes and exhibit three growth forms columnar layered pseudo columnar and columnar each located in different stratigraphic horizons the columnar type is the most conspicuous and provides key information on the mode of their construction in this paper we describe the mega to microscopic features of these stromatolites together with interpretations of their construction the columnar type typically comprises alternations of lighter and darker laminae with intercalations of dense micritic laminae the lighter laminae are composed of fine to coarse calcite cement and fine dolomite whereas the darker laminae are composed of micrite and microspar endolithic coccoids are sporadic in these laminae in contrast the dense micritic laminae consist of micrite with abundant endolithic coccoids accentuating the laminae of stromatolites the columnar stromatolites were formed under deteriorating conditions after the end permian mass extinction as follows 1 the alternating development of lighter and darker laminae due to the colonization of different microbial communities in lower energy shallow to deep subtidal settings 2 carbonate precipitation within each microbial community through microbial metabolic activity and degradation of extracellular polymeric substances eps leading to the alternations of lighter and darker laminae 3 episodic interruption of the growth of the lighter and darker laminae by endolithic coccoidal activity and 4 high levels of endolithic activity accompanied by the precipitation of carbonate within boreholes to produce the dense micritic laminae in contrast the columnar layered and pseudo columnar types comprise alternations of lighter and darker laminae composed mainly of fine to coarse calcite cement fine dolomite micrite peloids and microspar with sporadic endolithic coccoids the dense micritic laminae are absent or rare in these stromatolites these types were essentially produced by the repetition of processes 1 and 2 documented in the columnar type the finely alternating laminae of these stromatolites are therefore the product of the repeated initiation and cessation of growth of relevant microbial communities in response to changing environmental conditions the stromatolites were formed immediately after the end permian extinction and persisted intermittently throughout the early triassic the chongyang stromatolites are undoubtedly some of the best developed stromatolites near the permian triassic boundary and retain a high resolution record of microbial successions and palaeo oceanic perturbations immediately following the end permian extinction

landslide hazard assessment in the three gorges area china using aster imagery wushan badong abstract the objectives of this study are to develop a methodology for regional scale assessment of landslide hazard using remotely sensed data and to produce a landslide hazard map of the wushan badong area in the three gorges china from advanced spaceborne thermal emission and reflection radiometer aster images the area is undergoing rapid urban development with slope instability causing a widespread natural hazard landslide related parameters were largely estimated through image processing and visual interpretation of aster multi spectral and topographic data we used field measurements to define the quantification for three parameters a slope angle in relation to lithology b distance to drainage network in relation to stream order and c distance to tectonic lineament in relation to lineament length we employed a multi parameter elimination and characterization model based on estimation of the geometric mean to remove areas where landslides are not expected to occur and classify the remaining areas into landslide hazard categories our results show increased landslide hazard in and around wushan and badong towns as well as other populated areas along the yangtze and its tributaries we used field data on landslide distribution to identify typical geomorphological settings for different landslide types and to provide ground control for the hazard assessment the results indicate good correlation between classified high hazard areas and field confirmed slope failures and show the usefulness of aster imagery for landslide hazard assessment at a regional scale

an evolution model of large consequent bedding rockslides with particular reference to the jiweishan rockslide in southwest china abstract strata consisting of massive dipping layers of hard rock interbedded with thin soft interlayers are common in southwest china and this structure is conducive to the formation of consequent bedding rockslides the huge jiweishan rockslide is an example that mobilized 5 6 million m 3 of massive lower permian limestone that was stratigraphically situated above a weak 30 cm thick layer of bituminous shale with a downslope dip of 21 field data and historical observations indicate that the rupture surface of this rockslide weakened gradually from the rear upper part to the front this evidence includes 1 a decrease in the thickness and areal extent of fracture parallel calcite veinlets along the thin rupture zone 2 the development of a wide vertical tension fracture at the upper boundary of the slide block about 50 years before the catastrophic failure 3 a succession of small collapses that migrated from the upper to the lower parts of the slide block in the decade before the massive failure this type of landslide is accordingly termed an advancing consequent bedding rockslide acb rockslide an equation was developed to simulate the mechanical behavior of the rupture surface as a function of position and time finally a computational model that incorporates this equation was used to simulate the evolutionary history using realistic mechanical parameters the simulation results show how the size of an upper driving block progressively enlarges at the expense of a lower locking block that restrains the slide mass until the locking block becomes so small and weak that failure occurs good agreement between the simulation results and field data support the proposed evolution model including the calculated size of the locking block prior to failure and the width of the upper tension fracture

a comparative study of landslide susceptibility mapping using weight of evidence logistic regression and support vector machine and evaluated by sbas insar monitoring zhouqu to wudu segment in bailong river basin china the determining of landslide prone areas in mountainous terrain is essential for land planning and hazard mitigation in this paper a comparative study using three statistical models including weight of evidence model woe logistic regression model lr and support vector machine method svm was undertaken in the zhouqu to wudu segment in the bailong river basin southern gansu china six conditionally independent environmental factors elevation slope aspect distance from fault lithology and settlement density were selected as the explanatory variables that may contribute to landslide occurrence based on principal component analysis pca and chi square test the relation between landslide distributions and these variables was analyzed using the three models and the results then used to calculate the landslide susceptibility ls the performance of the models was then evaluated using both the highly accurate deformation signals produced by using the small baseline subset interferometric synthetic aperture radar technique and receiver operating characteristic roc curve results show more deformation points in areas with high and very high ls levels and also more stable points in areas with low and very low ls levels for the svm model in addition the svm has larger area under the roc curve it indicates that the svm has better prediction accuracy and classified ability for the interpretability the woe derives the class of factors that most contributed to landsliding in the study area and the lr reveals that factors including elevation settlement density and distance from fault played major roles in landslide occurrence and distribution whereas the svm cannot provide relative weights for the variables the outperformed svm could be employed to determine potential landslide zones in the study area outcome of this research would provide preliminary basis for general land planning such as choosing new urban areas and infrastructure construction in the future as well as for landslide hazard mitigation in bailong river basin

review of stratigraphy structure and hydrocarbon potential of bass basin australia the intracratonic bass basin is the central basin of three that underlie bass strait in southeastern australia the basin was formed by extensional tectonics during the late jurassic to early cretaceous it contains up to 7 km 23 000 ft of nonmarine sediments of late jurassic to late eocene age and up to 3 5 km 11 500 ft of upper eocene to holocene marine sediments volcanics occur in places the sedimentary history of the basin is interpreted to have been dominated initially by cretaceous flood plain alluvial fan and lacustrine deposition then late cretaceous and early tertiary flood plain deposition and finally cenozoic shallow marine deposition seismic reflection studies show that significant structural and stratigraphic prospects for petroleum exploration occur at paleocene cretaceous and jurassic levels source rock studies combined with depositional models for the upper cretaceous to paleocene nonmarine fill suggest that suitable source and reservoir rocks occur at these levels present day maturation levels of organic matter in sediments of the basin suggest that mature levels for petroleum generation occur at 3 5 km 10 000 16 000 ft depth which generally corresponds to upper cretaceous to paleocene sediments an analysis of the maturation history of the basin suggests that the lower levels of the upper cretaceous sediments had peak petroleum generation potential ro 0 7 by about 40 ma whereas the upper levels of the paleocene sediments have attained this level of maturity only in the last 5 m y furthermore th relative lack of exploration success at shallower immature levels of the basin argues against well developed vertical migration paths and suggests that petroleum may have been trapped mainly at mature levels considerable unexplored petroleum potential exists in the bass basin the best potential for petroleum exploration appears to be at mature levels within the upper cretaceous to paleocene eastern view coal measures

autologistic modelling of susceptibility to landsliding in the central apennines italy in previous research a logistic regression of landslide occurrence on several explanatory variables was fitted and used to map landslide susceptibility for a small area in the central apennines italy here the spatial dependence or spatial correlation in the residuals from the fitted regression model was accounted for by inserting an autocovariate into the model the autocovariate was estimated by applying a gibbs sampler to the susceptibilities for neighbouring pixels as in any landslide susceptibility analysis accuracy was difficult to assess because of the requirement for data on future landslides however by comparing the ordinary logistic model to the autologistic model obtained on the same set of data it was possible to assess the influence of the autocovariate the autocovariate rendered the model simpler because several variables lost their significance and were therefore omitted from the model further areas of high landslide susceptibility estimated from the autologistic model were geographically clustered as one would expect and this may be advantageous in terms of i interpreting the model and ii displaying the results to non experts

genesis of carbonate precipitate patterns and associated microfossils in mesoproterozoic formations of india and russia a comparative study abstract the jaradag fawn limestone formation 1 6 ga semri group vindhyan supergroup india contains abundant microfossils and precipitates in early diagenetic bedded and stromatolitic cherts the silicified carbonate precipitates and associated micritic event laminae were formed at or near the sediment water interface and presumably lithified very rapidly the precipitates deposited inorganically without active participation of cyanobacterial mats can be grouped into three morphological categories radial fibrous fans microlaminated stratiform laminae and poorly differentiated laminated stratiform laminae a diverse assemblage of cyanobacteria is preserved both within precipitates where preservation is excellent and in other synsedimentary textures precipitates and microfossil assemblages from four mesoproterozoic formations of siberia are described and compared with those from jaradag fawn limestone comparison of the indian and the siberian precipitates and associated microfossil assemblages reveals an almost identical pattern for contemporaneous mesoproterozoic carbonate precipitates and microbiotas in cherts the microbial assemblages almost exclusively composed of the remnants of cyanobacteria are dominated by entophysalidacean members and short trichomes and can be termed as typical mesoproterozoic microbiotas co occurrence of these microbiotas and precipitates is probably related to the depositional environment of the mesoproterozoic tidal flats with high carbonate saturation neoproterozoic depositional conditions changed drastically as did the composition of microbial communities

qualitative landslide susceptibility assessment by multicriteria analysis a case study from san antonio del sur guantanamo cuba geomorphological information can be combined with decision support tools to assess landslide hazard and risk a heuristic model was applied to a rural municipality in eastern cuba the study is based on a terrain mapping units tmu map generated at 1 50 000 scale by interpretation of aerial photos satellite images and field data information describing 603 terrain units was collected in a database landslide areas were mapped in detail to classify the different failure types and parts three major landslide regions are recognized in the study area coastal hills with rockfalls shallow debris flows and old rotational rockslides denudational slopes in limestone with very large deep seated rockslides related to tectonic activity and the sierra de caujeri scarp with large rockslides the caujeri scarp presents the highest hazard with recent landslides and various signs of active processes the different landforms and the causative factors for landslides were analyzed and used to develop the heuristic model the model is based on weights assigned by expert judgment and organized in a number of components such as slope angle internal relief slope shape geological formation active faults distance to drainage distance to springs geomorphological subunits and existing landslide zones from these variables a hierarchical heuristic model was applied in which three levels of weights were designed for classes variables and criteria the model combines all weights into a single hazard value for each pixel of the landslide hazard map the hazard map was then divided by two scales one with three classes for disaster managers and one with 10 detailed hazard classes for technical staff the range of weight values and the number of existing landslides is registered for each class the resulting increasing landslide density with higher hazard classes indicates that the output map is reliable the landslide hazard map was used in combination with existing information on buildings and infrastructure to prepare a qualitative risk map the complete lack of historical landslide information and geotechnical data precludes the development of quantitative deterministic or probabilistic models

composition and structure of microbialite ecosystems following the end permian mass extinction in south china after the end permian mass extinction microbialites were widespread in the shallow marine environments in south china diverse microbialites are characteristic of the early triassic carbonate sequences their stratigraphic range is rather short just across the permian triassic p tr boundary and defined by conodonts n meishanensis h changxingensis and h parvus zones thus the p tr microbialites grew immediately after the first episode of the end permian mass extinction coinciding with the beginning of the conodont n meishanensis zone and ceased their growth at the beginning of the conodont i staeschei zone which occurred just before the second episode of the end permian crisis at meishan they include three main types stromatolites thrombolites and dendrites in south china the presence of abundant microbial remains of coccoid type and renalcis like microbes strengthens the previous view that the p tr microbialites are biogenic both cyanobacteria and other microbes have participated to construct the microbial ecosystems the thrombolite communities are dominated by the renalcis like microbes and foraminifers and also contain ostracods microgastropods and microconchids the stromatolite communities are dominated by coccoidal microbes with minor constituents of other undetermined microbes metazoans are rare the dendrolite assemblage contains few identifiable microfossils most of microbialite communities have a high abundance low diversity community structure characteristic of marine communities after the end permian mass extinction some metazoans of either opportunists or disaster forms dwelled in this special ecosystem the microbialite builders formed the primary producer communities and constructed the lowest level ecosystem structure the lower level ecosystem proliferated due to the collapse of the higher level of ecosystem structure characterized by benthic shelly and predator communities in the end permian crisis

microbe mineral interactions early carbonate precipitation in a hypersaline lake eleuthera island bahamas microbialites benthic microbial carbonate deposits were discovered in a hypersaline alkaline lake on eleuthera island bahamas from the edge towards the centre of the lake four main zones of precipitation could be distinguished 1 millimetre sized clumps of mg calcite on a thin microbial mat 2 thicker and continuous carbonate crusts with columnar morphologies 3 isolated patches of carbonate crust separated by a dark non calcified gelatinous mat and 4 a dark microbial mat without precipitation in thin section the precipitate displayed a micropeloidal structure characterized by micritic micropeloids strong autofluorescence surrounded by microspar and spar cement no fluorescence observations using scanning electron microscopy sem equipped with a cryotransfer system indicate that micrite nucleation is initiated within a polymer biofilm that embeds microbial communities these extracellular polymeric substances eps are progressively replaced with high mg calcite discontinuous eps calcification generates a micropeloidal structure of the micrite possibly resulting from the presence of clusters of coccoid or remnants of filamentous bacteria at high magnification the microstructure of the initial precipitate consists of 200 500 nm spheres no precipitation is observed in or on the sheaths of cyanobacteria and only a negligible amount of precipitation is directly associated with the well organized and active filamentous cyanobacteria in deeper layers of the mat indicating that carbonate precipitation is not associated with co2 uptake during photosynthesis instead the precipitation occurs at the uppermost layer of the mat which is composed of eps empty filamentous bacteria and coccoids gloeocapsa spp two dimensional mapping of sulphate reduction shows high activity in close association with the carbonate precipitate at the top of the microbial mat in combination these findings suggest that net precipitation of calcium carbonate results from a temporal and spatial decoupling of the various microbial metabolic processes responsible for caco3 precipitation and dissolution theoretically partial degradation of eps by aerobic heterotrophs or uv fuels sulphate reducing activity which increases alkalinity in microdomains inducing caco3 precipitation this degradation could also be responsible for eps decarboxylation which eliminates ca 2 binding capacity of the eps and releases ca 2 ions that were originally bound by carboxyl groups at the end of these processes the eps biofilm is calcified and exhibits a micritic micropeloidal structure the eps free precipitate subsequently serves as a substrate for physico chemical precipitation of spar cement from the alkaline water of the lake the micropeloidal structure has an intimate mixture of

a comparison of information value and logistic regression models in landslide susceptibility mapping by using gis this study investigates the application of information value inv and logistic regression lr models for producing landslide susceptibility maps lsms of the zigui badong area near the three gorges reservoir in china this area is subject to anthropogenic influences because the reservoir s water level cyclically fluctuates between 145 and 175 m in addition the area suffers from extreme rainfall events due to the local climate and has experienced significant and widespread landslide events in recent years in this study a landslide inventory map was initially constructed using field surveys aerial photographs and a literature search of historical landslide records eight causative factors including lithology bedding structure slope aspect elevation profile curvature plane curvature and fractional vegetation cover were then considered in the generation of lsms by using the inv and lr models finally the prediction performances of these maps were assessed through receiver operating characteristics roc that utilized both success rate and prediction rate curves the validation results showed that the area under the roc curve for the inv model was 0 859 for the success rate curve and 0 865 for prediction rate curve these results indicate the inv model surpassed the lr model 0 742 for success rate curve and 0 740 for prediction rate curve overall the two models provided nearly similar results the results of this study show that landslide susceptibility mapping in the zigui badong area is viable with both approaches

microbial carbonates the geological record of the calcified bacterial algal mats and biofilms summary deposits produced by microbial growth and metabolism have been important components of carbonate sediments since the archaean geologically best known in seas and lakes microbial carbonates are also important at the present day in fluviatile spring cave and soil environments the principal organisms involved are bacteria particularly cyanobacteria small algae and fungi that participate in the growth of microbial biofilms and mats grain trapping is locally important but the key process is precipitation producing reefal accumulations of calcified microbes and enhancing mat accretion and preservation various metabolic processes such as photosynthetic uptake of co2 and or hco3 by cyanobacteria and ammonification denitrification and sulphate reduction by other bacteria can increase alkalinity and stimulate carbonate precipitation extracellular polymeric substances widely produced by microbes for attachment and protection are important in providing nucleation sites and facilitating sediment trapping microbial carbonate microfabrics are heterogeneous they commonly incorporate trapped particles and in situ algae and invertebrates and crystals form around bacterial cells but the main component is dense clotted or peloidal micrite resulting from calcification of bacterial cells sheaths and biofilm and from phytoplankton stimulated whiting nucleation interpretation of these texturally convergent and often inscrutable fabrics is a challenge conspicuous accumulations are large domes and columns with laminated stromatolite clotted thrombolite and other macrofabrics which may be either agglutinated or mainly composed of calcified or spar encrusted microbes stromatolite lamination appears to be primary but clotted thrombolite fabrics can be primary or secondary microbial precipitation also contributes to hot spring travertine cold spring mound calcrete cave crust and coated grain deposits as well as influencing carbonate cementation recrystallization and replacement microbial carbonate is biologically stimulated but also requires favourable saturation state in ambient water and thus relies uniquely on a combination of biotic and abiotic factors this overriding environmental control is seen at the present day by the localization of microbial carbonates in calcareous streams and springs and in shallow tropical seas and in the past by temporal variation in abundance of marine microbial carbonates patterns of cyanobacterial calcification and microbial dome formation through time appear to reflect fluctuations in seawater chemistry stromatolites appeared at 3450 ma and were generally diverse and abundant from 2800 to 1000 ma inception of a proterozoic decline variously identified at 2000 1000 and 675 ma has been attributed to eukaryote competition and or reduced lithification thrombolites and dendrolites mainly formed by calcified cyanobacteria became important early in the palaeozoic and reappeared in the late devonian microbial carbonates retained importance through much of the mesozoic became scarcer in marine environments in the cenozoic but locally re emerged as large agglutinated domes possibly reflecting increased algal involvement and thick micritic reef crusts in the late neogene famous modern examples at shark bay and lee stocking island are composite coarse agglutinated domes and columns with complex bacterial algal mats occurring in environments that are both stressed and current swept products of mat evolution ecological refugia sites of enhanced early lithification or all three

gis based support vector machine modeling of earthquake triggered landslide susceptibility in the jianjiang river watershed china abstract support vector machine svm modeling is based on statistical learning theory it involves a training phase with associated input and target output values in recent years the method has become increasingly popular the main purpose of this study is to evaluate the mapping power of svm modeling in earthquake triggered landslide susceptibility mapping for a section of the jianjiang river watershed using a geographic information system gis software the river was affected by the wenchuan earthquake of may 12 2008 visual interpretation of colored aerial photographs of 1 m resolution and extensive field surveys provided a detailed landslide inventory map containing 3147 landslides related to the 2008 wenchuan earthquake elevation slope angle slope aspect distance from seismogenic faults distance from drainages and lithology were used as the controlling parameters for modeling three groups of positive and negative training samples were used in concert with four different kernel functions positive training samples include the centroids of 500 large landslides those of all 3147 landslides and 5000 randomly selected points in landslide polygons negative training samples include 500 3147 and 5000 randomly selected points on slopes that remained stable during the wenchuan earthquake the four kernel functions are linear polynomial radial basis and sigmoid in total 12 cases of landslide susceptibility were mapped comparative analyses of landslide susceptibility probability and area relation curves show that both the polynomial and radial basis functions suitably classified the input data as either landslide positive or negative though the radial basis function was more successful the 12 generated landslide susceptibility maps were compared with known landslide centroid locations and landslide polygons to verify the success rate and predictive accuracy of each model the 12 results were further validated using area under curve analysis group 3 with 5000 randomly selected points on the landslide polygons and 5000 randomly selected points along stable slopes gave the best results with a success rate of 79 20 and predictive accuracy of 79 13 under the radial basis function of all the results the sigmoid kernel function was the least skillful when used in concert with the centroid data of all 3147 landslides as positive training samples and the negative training samples of 3147 randomly selected points in regions of stable slope success rate 54 95 predictive accuracy 61 85 this paper also provides suggestions and reference data for selecting appropriate training samples and kernel function types for earthquake triggered landslide susceptibility mapping using svm modeling predictive landslide susceptibility maps could be useful in hazard mitigation by helping planners understand the probability of landslides in different regions

landslide hazard assessment in the three gorges area of the yangtze river using aster imagery zigui badong this paper reports a regional assessment of landslide hazard in the three gorges area china based on terra 1 satellite advanced spaceborne thermal emission radiometer aster imagery data including a stereo image derived digital elevation model dem and multi spectral reflective and thermal imagery in combination with limited field investigation the three gorges dam and reservoir project has gained international attention not only for its great potential for hydro electrical power generation and flood control but also for its potentially harmful effects on the environment and socio economy the most significant and widespread natural hazard in the region is slope instability a simple multi variable elimination and characterisation model employing geometric mean and boolean decision rules has been applied to a multi criterion image dataset to categorise the area into a series of potential landslide hazard levels which are presented in map form the results presented here show high levels of hazard in and around all the main inhabited areas along the river limited fieldwork has been conducted to provide reliable ground control and the results of this paper show good correlation with this field evidence

the assessment of landslide susceptibility mapping using random forest and decision tree methods in the three gorges reservoir area china landslide susceptibility mapping is an indispensable prerequisite for landslide prevention and reduction at present research into landslide susceptibility mapping has begun to combine machine learning with remote sensing and geographic information system gis techniques the random forest model is a new integrated classification method but its application to landslide susceptibility mapping remains limited landslides represent a serious threat to the lives and property of people living in the zigui badong area in the three gorges region of china as well as to the operation of the three gorges reservoir however the geological structure of this region is complex involving steep mountains and deep valleys the purpose of the current study is to produce a landslide susceptibility map of the zigui badong area using a random forest model multisource data gis and remote sensing data in total 300 pre existing landslide locations were obtained from a landslide inventory map these landslides were identified using visual interpretation of high resolution remote sensing images topographic and geologic data and extensive field surveys the occurrence of landslides is closely related to a series of environmental parameters topographic geologic landsat 8 image raining data and seismic data were used as the primary data sources to extract the geo environmental factors influencing landslides thirty four layers of causative factors were prepared as predictor variables which can mainly be categorized as topographic geological hydrological land cover and environmental trigger parameters the random forest method is an ensemble classification technique that extends diversity among the classification trees by resampling the data with replacement and randomly changing the predictive variable sets during the different tree induction processes a random forest model was adopted to calculate the quantitative relationships between the landslide conditioning factors and the landslide inventory map and then generate a landslide susceptibility map the analytical results were compared with known landslide locations in terms of area under the receiver operating characteristic curve the random forest model has an area ratio of 86 10 in contrast to the random forest whole factors wf random forest 12 major factors 12f decision tree wf decision tree 12f the final result shows that random forest 12f has a higher prediction accuracy meanwhile the random forest models have higher prediction accuracy than the decision tree model subsequently the landslide susceptibility map was classified into five classes very low low moderate high and very high the results demonstrate that the random forest model achieved a reasonable accuracy in landslide susceptibility mapping the landslide hazard zone information will be useful for general development planning and landslide risk management

onset development and cessation of basal early triassic microbialites betm in the nanpanjiang pull apart basin south china block abstract new investigations in the nanpanjiang basin indicate that the onset of the iconic microbialites associated with the paleozoic mesozoic boundary was early triassic in age bathymetry water agitation oxygenation light penetration and clastic load are shown to have exerted a direct control on the growth of microbialites carbonate supersaturation is also required for the deposition of the microbialites bathymetric control is further corroborated by the inheritance of the topography of a latest permian pull apart basin into early triassic times with a distribution of basal early triassic microbialites betm restricted to uplifted blocks and the accumulation of carbonaceous black shales in adjacent troughs the geographically most extensive nanpanjiang betm bloomed on a large nw se trending uplifted block exceeding 12 000 km 2 luolou platform centered on northwestern guangxi post triassic displacements along the youjiang fault obscure the paleogeographic relation of betm exposed west of this fault triassic foraminifers occur in the basal most betm episode which is locally bracketed by high energy grainstones made of reworked permian foraminifers therefore the permian triassic boundary ptb is within the unconformity that separates the late permian heshan fm from the basal most betm where accommodation space was sufficient up to five event surfaces are associated with the unconformity microfacies analysis supports chemical dissolution but did not reveal evidence for subaerial erosion although intercalated grainstone made of permian foraminifers indicate reworking chemical dissolution and mechanical erosion both conceivably contributed to the genesis of the unconformity the upward shift from tabulated to domical microbial build ups is accompanied by accumulation of coquinoid lenses between domes which indicates deepening of the luolou platform betm the main drowning resulting from both regional tectonic subsidence and a global sea level rise led to the cessation of the betm that were buried under predominant fine siliciclastics any concomitant change in sea water chemistry appears unlikely

spatial prediction of landslides using a hybrid machine learning approach based on random subspace and classification and regression trees abstract a hybrid machine learning approach of random subspace rss and classification and regression trees cart is proposed to develop a model named rsscart for spatial prediction of landslides this model is a combination of the rss method which is known as an efficient ensemble technique and the cart which is a state of the art classifier the luc yen district of yen bai province a prominent landslide prone area of viet nam was selected for the model development performance of the rsscart model was evaluated through the receiver operating characteristic roc curve statistical analysis methods and the chi square test results were compared with other benchmark landslide models namely support vector machines svm single cart naive bayes trees nbt and logistic regression lr in the development of model ten important landslide affecting factors related with geomorphology geology and geo environment were considered namely slope angles elevation slope aspect curvature lithology distance to faults distance to rivers distance to roads and rainfall performance of the rsscart model auc 0 841 is the best compared with other popular landslide models namely svm 0 835 single cart 0 822 nbt 0 821 and lr 0 723 these results indicate that performance of the rsscart is a promising method for spatial landslide prediction

tectonic controls on rift basin morphology evolution of the northern malawi nyasa rift radiometric k ar and ar 40 ar 39 age determinations of volcanic and volcaniclastic rocks combined with structural gravity and seismic reflection data are used to constrain the age of sedimentary strata contained within the seismically and volcanically active northern malawi nyasa rift and to characterize changes in basin and flank morphologies with time faulting and volcanism within the tukuyu karonga basin began at approximately 8 6 ma when sediments were deposited in abroad initially asymmetric lake basin bounded on its northeastern side by a border fault system with minor topographic relief extensions primarily by a slip along the border fault and subsequent regional isostatic compensation led to the development of a 5 km deep basin bounded by broad uplifted flanks along the low relief basin margin opposite border fault younger stratigraphic sequences commonly onlap older wedge shaped sequences although their internal geometry is often progradational intrabasinal faulting flankuplift and basaltic and felsic volcanism from centers at the northern end of the basin became more important at about 2 5 ma when cross rift transfer faults developed to link the tukuyu karonga basin to the rukwa basin local uplift and volcanic construction at the northern end of the basin led to a southeastward shift in the basin s depocenter sequence boundaries are commonly erosional along this low relief hanging wall margin and conformable in the deep lake basin the geometry of stratigraphic sequences and the distribution of the erosion indicate that horizontal and vertical crustal movements both across and along the length of the rift basin led to changes in levels of the lake irrespective of paleoclimatic fluctuations

gis techniques and statistical models in evaluating landslide hazard geographical information systems gis and numerical cartography may greatly facilitate the development and use of statistical models for the assessment of regional landslide hazard from a small drainage basin located in central italy relevant geological and geomorphological factors were collected and processed by applying gis technology in particular modules were used which both generate high fidelity digital terrain models and automatically partition the terrain into main slope units the resulting information was then analysed by discriminant analysis which enabled landslide hazard and risk to be evaluated in each slope unit although not lacking drawbacks the method proved to be a feasible and cost effective approach to landslide susceptibility assessment and mapping

gis based logistic regression for landslide susceptibility mapping of the zhongxian segment in the three gorges area china abstract a detailed landslide susceptibility map was produced using a logistic regression method with datasets developed for a geographic information system gis known as one of the most landslide prone areas in china the zhongxian shizhu segment in the three gorges reservoir region of china was selected as a suitable case to evaluate the frequency and distribution of landslides the site covered an area of 260 9 km 2 with a landslide area of 5 3 km 2 four data domains were used in this study remote sensing products thematic maps geological maps and topographical maps all with 25 25 m 2 pixels or cells statistical relationships for landslide susceptibility were developed using landslide and landslide causative factor databases we extended the application of logistic regression approaches to use all continuous variables as they are and the landslide density is used to transform these nominal variables to numeric variable according to the map 2 8 of the study area was identified as an area with very high susceptibility whereas very low low medium and high susceptibility zones covered 18 2 36 2 26 7 and 16 1 of the area respectively the quality of susceptibility mapping was validated and the correct classification percentage and root mean square error rmse values for the validation data were 81 4 and 0 392 respectively

microbenthic distribution of proterozoic tidal flats environmental and taphonomic considerations silicified carbonates of the late mesoproterozoic to early neoproterozoic society cliffs formation baffin island contain distinctive microfabrics and microbenthic assemblages whose paleo environmental distribution within the formation parallels the distribution of these elements through proterozoic time in the society cliffs formation restricted carbonates including microdigitate stromatolites laminated tufa and tufted microbial mats consist predominantly of synsedimentary cements these facies and the cyanobacterial fossils they contain are common in paleoproterozoic successions but rare in neoproterozoic and younger rocks less restricted tidal flat facies in the formation are composed of laminated microbialites dominated by micritic carbonate lithified early yet demonstrably after compaction these strata contain cyanobacteria that are characteristic in neoproterozoic rocks within the formation the facies dependent distribution of microbial populations reflects both the style and timing of carbonate deposition because of the strong substrate specificity of benthic cyanobacteria a reasonable conclusion is that secular changes in microbenthic assemblages through proterozoic time reflect a decrease in the overall representation of rapidly lithified carbonate substrates in younger peritidal environments as well as concomitant changes in the taphonomic window of silicification through which early life is observed

landslide spatial susceptibility mapping by using gis and remote sensing techniques a case study in zigui county the three georges reservoir china landslides are one of the most destructive phenomena in nature and damage both property and lives every year in this paper a logistic regression model with datasets developed via a geographic information system and remotely sensed data was used to create a landslide spatial susceptibility map for the three gorges project reservoir region on the yangtze river in zigui county the five causative factors used in the logistic regression model were evaluated in different ways topographic slope and topographic aspect were derived from a topographical map at 1 50 000 scale bed rock slope relationship and lithology were obtained from a geological map at 1 50 000 scale and fractional vegetation cover fvc which represents the reduced frequency of landslides due to the vegetation canopy and ground cover and is also one of the most difficult parameters to estimate over broad geographic areas was generated using a back propagation neural network bpnn method based on cbers china brazil earth resources satellite data the results of which were compared with values measured in the field the obtained pearson correlation coefficient r was 0 899 then the fvc factor and the other four factors were used as the input to a logistic regression model by integrating the five factor maps in the geographical information system gis via pixel based computing the landslide spatial susceptibility map was obtained the study area was reclassified into four categories of landslide susceptibility severe moderate low and very low approximately 15 0 of the study area was identified as severe susceptibility and very low low and moderate susceptibility zones covered 21 8 41 7 and 21 5 of the area respectively these results have an accuracy of 78 90 thus by using a logistic regression model in a gis environment a spatial susceptibility map of landslides can be obtained and the regions in zigui county that are susceptible to landslides and need immediate protective and mitigation measures can be identified

gis based landslide susceptibility mapping using analytical hierarchy process and bivariate statistics in ardesen turkey comparisons of results and confirmations abstract the ardesen area is prone to landslides because of the climate conditions geologic and geomorphologic characteristics of the region as in previous years in 2001 due to heavy rainfall there were many landslides resulting in damage and human casualties there is still a great danger of further landslides in the region therefore it is vitally important to prepare a landslide susceptibility map of the region in this study the analytical hierarchy process ahp the statistical index wi and weighting factor wf methods were used to produce and later compare three susceptibility maps for this purpose thematic layers including landslide inventory lithology weathering slope aspect land cover distance to stream drainage density and distance to road were used in this study area 98 of landslides occurred in highly or completely weathered units lithology weathering land cover and slope data layers were found to be important factors in the study area to confirm the practicality of the three susceptibility maps were compared with a landslide activity map containing 16 active landslide zones the outcome was that the active landslide zones do not completely fit into the high and very high susceptibility classes but 81 3 of these landslide zones fall into the high and very high susceptibility zones of the ahp method while this is 62 5 in the case of wi method and 68 8 with the wf method in spite of the results obtained in this study the development of a susceptibility map is usually determined by the needs and available resources the results showed that the ahp method gave a more realistic picture of the actual distribution of landslide susceptibility than the wi and wf methods

an inventory driven rock glacier status model intact vs relict for south tyrol eastern italian alps ice presence in rock glaciers is a topic that is likely to gain importance in the future due to the expected decrease in water supply from glaciers and the increase of mass movements originating in periglacial areas this makes it important to have at ones disposal inventories with complete information on the state of rock glaciers this study presents a method to overcome incomplete information on the status of rock glaciers i e intact vs relict recorded in regional scale inventories the proposed data driven modelling framework can be used to estimate the likelihood that rock glaciers contain frozen material potential predictor variables related to topography environmental controls or the rock glacier appearance were derived from a digital terrain model dtm satellite data and gathered from existing data sets an initial exploratory data analysis supported the heuristic selection of predictor variables three classification algorithms namely logistic regression glm support vector machine svm and random forest rf were trained on the basis of the available information on the status of rock glaciers within the territory of south tyrol eastern italian alps the resulting classification rules led to assign a binary label intact or relict to 235 unclassified rock glaciers present in the inventory all models were validated quantitatively on spatially independent test samples spatial cross validation and achieved highly satisfactory performance scores hereby the less flexible statistically based classifier glm performed slightly better than the more flexible machine learning algorithms svm and rf spatial permutation based variable importance assessment revealed that elevation and vegetation cover based on ndvi were the most relevant predictors for more than 80 of the unclassified rock glaciers all of the three models agreed on the spatially predicted rock glacier status only for a minor portion 12 3 one model differed from the remaining two

pliocene burdur basin sw turkey tectonics seismicity and sedimentation the pliocene burdur formation of sw turkey was deposited in a ne sw trending half graben with a major basement fault along its se margin hangingwall sourced fans were confined proximally by basement topography distally they developed 9ideal9 fan geometries these fans became submerged by the lake that occupied the centre of the basin this transgression was caused by the migration with time of the hangingwall pivot away from the basin controlling fault footwall sourced fans exhibit three distinctly different geometries at the northern end of the basin a wide braidplain developed due to the rapid erosion of both penecontemporaneous volcaniclastic deposits to the east and the footwall crest of a newly formed fault within the basin along the footwall scarp in the central part of the basin a narrow bajada formed in the south a large alluvial fan had its source in the relay structure between two left stepping en echelon fault segments the small size of footwall sourced fans compared with those sourced on the hangingwall slope was due to rapid subsidence of the basin floor adjacent to the footwall scarp although this suggests high levels of seismicity the general paucity of wet sediment deformation within the burdur formation indicates that seismicity in the burdur region during the pliocene was more subdued than at present

evidence for high frequency cyclic fault activity from high resolution seismic reflection survey rukwa rift tanzania a high resolution seismic survey of the rukwa rift has imaged the upper 300 m of the pliocene holocene section the sediments are characterized by aggradational deposition in shallow lacustrine conditions that episodically dried out overall the reflection package expands northeastwards towards the lupa fault half graben bounding fault isopach maps for nine intervals 6 m to 65 m thick show four periods of marked expansion of the section towards the lupa fault interpreted to represent times of fault activity or infilling of fault created topography during the early stage of fault quiescence there are three periods of little or much reduced expansion interpreted to represent infilling of the accommodation space between the lake floor and the lake surface during periods of fault inactivity cyclicity of such high frequency has not been widely reported for faults which penetrate the crust the periods of activity show remarkably similar displacement patterns with no lateral migration of the main depocentre implying that seismic and aseismic slip has persistently clustered in the same parts of the fault identification of high frequency fault cyclicity has implications for sequence stratigraphy in tectonically active areas since there is a tendency to assume faults do not have cyclic effects on the scale of tens of thousands of years

late oligocene and miocene faulting and sedimentation and evolution of the southern rio grande rift new mexico usa abstract the distribution of nonmarine lithofacies paleocurrents and provenance data are used to define the evolution of late oligocene and miocene basins and complementary uplifts in the southern rio grande rift in the vicinity of hatch new mexico usa the late oligocene middle miocene hayner ranch formation which consists of a maximum of 1000 m of alluvial fan alluvial flat and lacustrine carbonate lithofacies was deposited in a narrow 12 km northwest trending northeast tilted half graben whose footwall was the caballo mountains block stratigraphic separation on the border faults of the caballo mountains block was approximately 1615 m an additional 854 m of stratigraphic separation along the caballo mountains border faults occurred during deposition of the middle late miocene rincon valley formation which is composed of up to 610 m of alluvial fan alluvial flat braided fluvial and gypsiferous playa lithofacies two new north trending fault blocks sierra de las uvas and dona ana mountains and complementary west northwest tilted half graben also developed during rincon valley time with approximately 549 m of stratigraphic separation along the border fault of the sierra de las uvas block in latest miocene and early pliocene time following deposition of the rincon valley formation movement continued along the border faults of the caballo mountains dona ana mountains and sierra de las uvas blocks and large parts of the hayner ranch and rincon valley basins were segmented into smaller fault blocks and basins by movement along new largely north trending faults analysis of the hayner ranch and rincon valley formations along with previous studies of the early oligocene bell top formation and late pliocene early pleistocene camp rice formation indicate that the traditional two stage model for development of the southern rio grande rift should be abandoned in favor of at least four episodes of block faulting beginning 35 ma ago with the exception of two northwest trending border faults of the caballo mountains block that may be reactivated along eocene compressional structures the majority of border faults and complementary basins throughout the history of the southern rio grande rift were north trending which challenges the conventional idea of a clockwise change in stress through time

landslide susceptibility assessment in lianhua county china a comparison between a random forest data mining technique and bivariate and multivariate statistical models abstract landslides are an important natural hazard that causes a great amount of damage around the world every year especially during the rainy season the lianhua area is located in the middle of china s southern mountainous area west of jiangxi province and is known to be an area prone to landslides the aim of this study was to evaluate and compare landslide susceptibility maps produced using the random forest rf data mining technique with those produced by bivariate evidential belief function and frequency ratio and multivariate logistic regression statistical models for lianhua county china first a landslide inventory map was prepared using aerial photograph interpretation satellite images and extensive field surveys in total 163 landslide events were recognized in the study area with 114 landslides 70 used for training and 49 landslides 30 used for validation next the landslide conditioning factors including the slope angle altitude slope aspect topographic wetness index twi slope length ls plan curvature profile curvature distance to rivers distance to faults distance to roads annual precipitation land use normalized difference vegetation index ndvi and lithology were derived from the spatial database finally the landslide susceptibility maps of lianhua county were generated in arcgis 10 1 based on the random forest rf evidential belief function ebf frequency ratio fr and logistic regression lr approaches and were validated using a receiver operating characteristic roc curve the roc plot assessment results showed that for landslide susceptibility maps produced using the ebf fr lr and rf models the area under the curve auc values were 0 8122 0 8134 0 7751 and 0 7172 respectively therefore we can conclude that all four models have an auc of more than 0 70 and can be used in landslide susceptibility mapping in the study area meanwhile the ebf and fr models had the best performance for lianhua county china thus the resultant susceptibility maps will be useful for land use planning and hazard mitigation aims

record of the end permian extinction and triassic biotic recovery in the chongzuo pingguo platform southern nanpanjiang basin guangxi south china abstract the chongzuo pingguo platform is a vast isolated platform 180 km across in the southern part of the nanpanjiang basin the end permian extinction is recorded in conformable sections in the northern part of the platform pingguo area upper permian skeletal packstone contains diverse open marine fossils including nankinella and sphaerulina it is overlain by a 4 6 m thick horizon of calcimicrobial framestone constructed by globular calcified microbial framework similar to renalcis the ptb event horizon is interpreted to occur at the top of the packstone coincident with the abrupt change to calcimicrobial framestone lacking permian macrofossils the transition from hindeodus latidentatus to h parvus occurs 1 m above the base of the calcimicrobial framestone marking the conformable biostratigraphic boundary during the early triassic the platform developed as a low relief bank rimmed with oolite shoals but was bordered by a high relief fault controlled escarpment along its southern margin platform interior facies of the majiaoling and beisi formations are 900 m thick and consist of thin bedded lime mudstone oolite and dolostone with restricted marine biota in four shallowing upward packages that define depositional sequences in the chongzuo area the platform was terminated at the end of the early triassic by burial with up to 1600 m of felsic pyroclastic volcanics and lava flows transgression and shallow marine carbonate sedimentation resumed early in the middle triassic followed by drowning in the bithynian as indicated by a shift to deep marine carbonate and clastic deposition in the pingguo area volcanic deposits are much thinner and only briefly interrupted carbonate accumulation here the platform interior drowned during a major back step early in the middle triassic anisian bithynian smaller pinnacle platforms of the guohua fm up to 1700 m thick continued to accumulate above the early triassic platform margin and were eventually drowned by the late pelsonian in the anisian the pinnacle platforms shifted to sharply defined reef rimmed margins with tubiphytes reefs the shift coincides with accelerated metazoan biotic recovery in the anisian however the reefs lack metazoan frameworks and are composed almost entirely of tubiphytes reinforced by large volumes of marine cement these observations indicate that controls beyond the recovery of framework building metazoans governed the re establishment platform margin reefs in the middle triassic

machine learning and fractal theory models for landslide susceptibility mapping case study from the jinsha river basin abstract the quality of non landslide negative samples may result in unreasonable prediction results for machine learning ml models the aim of this study is to improve the performance of ml models by perfecting the quality of non landslide samples in landslide susceptibility modelling so as to produce more reliable susceptibility maps the middle and lower reaches of jinsha river basin mlrjb were chosen as the study area and the elevation slope aspect curvature lithology distance to faults slope of slope slope of aspect precipitation land use and ndvi were considered as predisposing factors for landslide susceptibility mapping firstly three non landslide samples are randomly selected from the low slope area landslide free area and very low susceptibility area based on fractal theory ft model generation and then three sample scenarios are constructed with 4445 landslide positive samples next the performance of cross application of three sample scenarios in the support vector machines svm and naive bayes nb models are compared and evaluated based on the statistical indicators such as accuracy recall precision receiver operating characteristic roc curve and area under the roc curve auc the evaluation results show that the non landslide negative samples generated on the basis of ft model are more reasonable and that the hybrid method supported by ft and ml models exhibits the highest prediction efficiency around 94 overall accuracy produced by scenario ft followed by scenario ss 87 and scenario rs 65 finally with the validation of landslide and unstable slopes data the landslide susceptibility map produced by the hybrid method composed of ft model and the svm model is the ultimate output product for landslide prevention

controls on facies architecture of a large triassic carbonate platform the great bank of guizhou nanpanjiang basin south china abstract the great bank of guizhou gbg is an exceptionally well exposed isolated triassic platform in the nanpanjiang basin of south china the platform is exhumed with its depositional profile preserved and is dissected by a faulted syncline that exposes a complete and uncomplicated cross section providing a unique opportunity to evaluate mechanisms involved in its birth evolution and demise the gbg formed near the southern margin of the yangtze platform during a deepening event that expanded the nanpanjiang basin and drowned the region surrounding the gbg in the latest permian initial accumulation of the gbg began in the latest permian with small reef mounds and open marine skeletal packstones following the end permian extinction cyanobacterial boundstones grew over the bank top during the early triassic the gbg developed a low relief bank profile with mobile oolite shoals at the margin shallow subtidal and peritidal deposits in the interior and gentle slopes dominated by pelagics debris flow deposits and turbidites at the basin margin in the middle triassic anisian the gbg developed a progressively steepening profile rimmed with massive tubiphytes reefs the platform was flat topped with tidal flat deposits across the interior basin margin deposition was dominated by turbidites and debris flow deposits but eventually shifted to avalanche and rock fall deposits as the slopes steepened to the angle of repose in the middle triassic ladinian an erosional escarpment up to 1700 m high developed at the margin platform margin strata are bedded packstones similar to interior strata whereas breccias at the basin margin contain coral boundstone clasts suggesting erosion of reefs from the escarpment a restricted subtidal lagoon formed in the interior producing an atoll like morphology later a flat topped profile was restored as tidal flats spread across the interior in the beginning of the late triassic deepening contributed to termination of the gbg before siliciclastic turbidites and shales were deposited over the platform in contrast with the well known platforms of the dolomites of northern italy the gbg contains abundant muddy carbonates and a progressively steepening bank to reef rimmed and escarpment architecture the italian platforms contain little mud and have angle of repose pinnacle geometries the gbg s larger size increased mud production and protected it from extensive winnowing of mud which in turn resulted in off bank shedding of muddy sediments that were stable on relatively gentle basin margin slopes which progressively steepened and ultimately led to avalanche deposits and a high relief erosional escarpment in contrast the lesser mud content of the dolomites platforms forced avalanche and talus deposition to dominate throughout deposition of basin margins which in turn produced their angle of repose geometries

landslide hazard evaluation a review of current techniques and their application in a multi scale study central italy in recent years growing population and expansion of settlements and life lines over hazardous areas have largely increased the impact of natural disasters both in industrialized and developing countries third world countries have difficulty meeting the high costs of controlling natural hazards through major engineering works and rational land use planning industrialized societies are increasingly reluctant to invest money in structural measures that can reduce natural risks hence the new issue is to implement warning systems and land utilization regulations aimed at minimizing the loss of lives and property without investing in long term costly projects of ground stabilization government and research institutions worldwide have long attempted to assess landslide hazard and risks and to portray its spatial distribution in maps several different methods for assessing landslide hazard were proposed or implemented the reliability of these maps and the criteria behind these hazard evaluations are ill formalized or poorly documented geomorphological information remains largely descriptive and subjective it is hence somewhat unsuitable to engineers policy makers or developers when planning land resources and mitigating the effects of geological hazards in the umbria and marche regions of central italy attempts at testing the proficiency and limitations of multivariate statistical techniques and of different methodologies for dividing the territory into suitable areas for landslide hazard assessment have been completed or are in progress at various scales these experiments showed that despite the operational and conceptual limitations landslide hazard assessment may indeed constitute a suitable cost effective aid to land use planning within this framework engineering geomorphology may play a renewed role in assessing areas at high landslide hazard and helping mitigate the associated risk

model testing of the response of stabilizing piles in landslides with upper hard and lower weak bedrock abstract the behavior of stabilizing piles with different embedded lengths in bedrock with a hard upper layer and a weak lower layer is examined using physical model tests based on the geological model of the landslide with bedrock with a hard upper layer and a weak lower layer the pile landslide physical model is developed and includes the data collection system the pile landslide model and the loading system the real time deformation and moment of the stabilizing pile is obtained in the process of loading at the trailing edge of the landslide for different percentages of hard bedrock the test results indicate that the percentage of hard bedrock has a strong influence on the deformation and moment of the stabilizing pile embedded in bedrock with a hard upper layer and a weak lower layer a higher percentage of hard bedrock can result in a greater maximum bending moment of the stabilizing pile and a smaller displacement at the stabilizing pile head and vice versa the results also show that 40 of hard bedrock can be considered the critical condition in bedrock with a hard upper layer and a weak lower layer the percentage of hard bedrock has a limited influence on the deformation of the stabilizing pile when the percentage is greater than 40 moreover four tests with stabilizing piles with different embedded lengths are conducted to investigate the most suitable embedded length in the bedrock with a hard upper layer and a weak lower layer the results indicate that 28 5 cm is a reasonable embedded length for the stabilizing pile in the two layered bedrock with a hard rock percentage of 20

interaction of an antecedent fluvial system with early normal fault growth implications for syn rift stratigraphy western corinth rift greece continental overfilled conditions during rift initiation are conventionally explained as due to low creation of accommodation compared with sediment supply alternatively sediment supply can be relatively high from the onset of rifting due to an antecedent drainage system the alluvial lower group of the western plio pleistocene corinth rift is used to investigate the interac tion of fluvial sedimentation with early rifting this rift was obliquely super imposed on the hellenide mountain belt from which it inherited a significant palaeorelief detailed sedimentary logging and mapping of the well exposed syn rift succession document the facies distributions palaeocurrents and stratigraphic architecture magnetostratigraphy and bios tratigraphy are used to date and correlate the alluvial succession across and between fault blocks from 3 2 to 1 8 ma a transverse low sinuosity braided river system flowed north north east to east across east west striking active fault blocks 4 to 7 km in width deposits evolved downstream from coarse alluvial conglomerates to fine grained lacustrine deposits over 15 to 30 km the length scale of facies belts is much greater than and thus not directly controlled by the width of the fault blocks at its termination the distribu tive river system built small stacked deltas into a shallow lake margin the presence of a major antecedent drainage system is supported by i a single major sediment entry point ii persistence of a main channel belt axis iii downstream fining at the scale of the rift basin the zones of maximum sub sidence on individual faults are aligned with the persistent fluvial axis sug gesting that sediment supply influenced normal fault growth instead of low accommodation rate during the early rift phase this study proposes that facies progradation can be controlled by continuous and high sediment sup ply from antecedent rivers

was phanerozoic reef history controlled by the distribution of non enzymatically secreted reef carbonates microbial carbonate and biologically induced cement throughout most of the phanerozoic reef rigidity resulted as much or more from early lithification by microbial carbonates and biologically induced cements non enzymatic carbonates than from biological encrustation of or by large enzymatically secreted metazoan skeletons reef framework is divided into four categories 1 skeletal metazoan 2 non skeletal microbialite stromatolite and thrombolite 3 calcimicrobe and 4 biocementstone in which small or delicate organisms serve as scaffolds for rigid cement crusts the last three categories are dominated by non enzymatic carbonates skeletal framework and non skeletal microbialite framework were the most abundant framework types through the phanerozoic the composition and abundance of skeletal framework was controlled largely by mass extinction events but most reefs consisted of both microbialite and skeletal organisms in a mutually beneficial relationship microbialite framework was abundant throughout the palaeozoic and early mesozoic but declined after the jurassic calcimicrobe framework was important during the cambrian early ordovician and devonian and biocementstone framework was important from the late mississippian to the late triassic the phanerozoic history of reefs does not correlate well with the stratigraphic distribution of large skeletal reef builders or with a variety of physicochemical parameters including sea level history wilson cycle or global climate cycles because non enzymatic carbonates result from induction by non obligate calcifiers and not enzymatic precipitation by obligate calcifiers the distribution of these carbonates was controlled to a larger extent by temporal changes in physicochemical parameters affecting the saturation state of sea water with respect to carbonate minerals changes in pco ca mg ratios cation concentrations and temperature may have affected the abundance of non enzymatic carbonates and hence reefs independently from the effects of these same parameters and mass extinction events on skeletal reef biota the decline in abundance of reefal microbialite and absence of calcimicrobe and biocementstone reef framework after the jurassic may be a result of relatively low saturation states of sea water owing to increased removal and sequestration of finite marine carbonate resources by calcareous plankton since the jurassic reef history is difficult to correlate with temporal changes in specific global parameters because these parameters affect skeletal biota and biologically induced carbonate precipitation independently hence reef history was regulated not just by skeletal reef biota but by parameters governing non enzymatic carbonates

the fabrics and origins of peloids immediately after the end permian extinction guizhou province south china abstract peloids are major contributors to modern and ancient limestones although their origins are not yet comprehensively understood upper permian to lower triassic carbonate successions are well preserved at the bangeng area in guizhou province south china where microbialites thrombolites coccoidal microbes and peloids are preserved together these peloids are classified into three types peloid a b c that typically occur together along with coccoidal microbes and restricted bioclasts in a variety of microenvironments peloid a is most common and exhibits close relationship with coccoidal microbes peloid a1 has spherical grain and a size range typical for coccoidal microbes 10 60 m in diameter whereas peloid a2 is marked by larger spherical and subrounded grains with diffuse margins ranging from 70 to 200 m in diameter peloid a1 is in part produced by the complete micritic filling in coccoidal microbes by their metabolic activities whereas peloid a2 is related to the calcification of a colony of coccoidal microbes by their metabolic activities or simply to the aggregation of individual peloids and coccoidal microbes peloids of this type might also originate from other carbonate precipitation processes peloid b is derived merely by micrite filling in ostracodes and gastropods skeletons whereas peloid c is of micritized bioclast origin these peloidal origins do not explain those of all environments and ages peloids are polygenetic in origin irrespective of the presence of coccoidal microbes however it is emphasized that the peloids formed after the end permian extinction are dominated by microbes related ones those kinds of peloids might have occurred repeatedly and predominantly especially in severely deteriorated environments such as those after the end permian mass extinction

paleobiology of the mesoproterozoic neoproterozoic transition the sukhaya tunguska formation turukhansk uplift siberia silicified carbonates of the latest mesoproterozoic sukhaya tunguska formation northwestern siberia contain abundant and diverse permineralized microfossils peritidal environments are dominated by microbial mats built by filamentous cyanobacteria comparable to modern species of lyngbya and phormidium in subtidal to lower intertidal settings mat dwelling microbenthos and possible coastal microplankton are abundant in contrast densely woven mat populations with few associated taxa characterize more restricted parts of tidal flats the preservation of vertically oriented sheath bundles and primary fenestrae indicates that in these mats carbonate cementation was commonly penecontemporaneous with mat growth eoentophysalis mats are limited to restricted environments where microlaminated carbonate precipitates formed on or just beneath the sediment surface most microbenthic populations are cyanobacterial although eukaryotic microfossils may occur among the simple spheroidal cells interpreted as coastal plankton protists are more securely represented by large up to 320 micrometers in diameter but poorly preserved acritarchs in basinal facies the sukhaya tunguska assemblage contains 27 species in 18 genera by virtue of their stratigraphic longevity and their close and predictable association with specific paleoenvironmental conditions including substrates proterozoic cyanobacteria support a model of bacterial evolution in which populations adapt rapidly to novel environments and thereafter resist competitive replacement the resulting evolutionary pattern is one of accumulation and stasis rather than the turnover and replacement characteristic of phanerozoic plants and animals

sponge microbial build ups from the lowermost triassic chanakhchi section in southern armenia microfacies and stable carbon isotopes abstract the end permian mass extinction was the most severe biotic crisis in earth s history in its direct aftermath microbial communities colonized some of the space left vacant after the severe decline of skeletal metazoans the permian triassic boundary microbialites were peculiarly abundant on low latitude shallow marine carbonate shelves of central tethyan continents armenia features particularly well preserved and diverse basal triassic sponge microbial build ups btsmbs which were not studied in detail to date here the chanakhchi section in southern armenia is described petrographically and by means of stable isotope analyses the armenian btsmbs formed in a distally open marine setting on a pelagic carbonate ramp in the course of two phases of microbial growth during the induan lower triassic the btsmbs are represented by predominantly thrombolitic but also dendrolitic and digitate stromatolite biostromes and mounds that vary in height between 5 cm to 12 m the digitate stromatolites are associated with calcium carbonate crystal fans ccfs microfacies analyses revealed that the btsmbs exhibit a number of different growth forms and internal fabrics the formation of ccfs was apparently not devoid of biological influence and took place above the sediment surface the abundance of sponges in the btsmbs reveals that ecologically complex metazoan microbial reefs have been present already early after the end permian mass extinction however the formation of biostromes and mounds did not depend on sponges or other metazoans btsmbs that formed during the second microbial growth phase revealed similar 13c values like the surrounding sediment in contrast the 13cmicrobialite and 13csediment values from the btsmbs and ccfs of the first growth phase show a difference of up to 2 3 suggesting a significant influence of photoautotrophy during microbially induced carbonate precipitation

neoproterozoic reef microstructures from the little dal group northwestern canada basinal facies in the neoproterozoic little dal group contain large reefs up to 300 m in height and 8 km in diameter in contrast to the stromatolitic composition typical of earlier proterozoic buildups little dal reefs consist mainly of three different calcareous microfossils a tubule thread microfossil analogous to the calcimicrobe girvanella in paleozoic reefs formed laminar reticulate structures like those in ordovician bioherms a clotted to saccate microfossil comparable morphologically to paleozoic renalcis constructed botryoidal to encrusting masses an enigmatic component of multicellular appearance that has attributes of an early calcified metaphyte exhibits the encrusting sheetlike habit characteristic of middle to late paleozoic algae these reefs represent an intermediate stage between proterozoic stromatolitic buildups and paleozoic metazoan calcimicrobial reefs and biogenic mounds

middle miocene to pleistocene sedimentary record of rift evolution in the southern albert rift uganda this study presents an almost complete middle miocene to pleistocene sequence of synrift sediments in the western branch of the east african rift the studied succession is exposed in several patches on an eastward tilted block between the northern tip of the rwenzori block and the eastern shoulder of the albert rift in this position it reaches a maximum thickness of 600 m of which 350 m have been logged systematically by analysing lithofacies and sediment architecture stratigraphic subdivision of the succession relies on published biostratigraphic data of endemic mollusc associations and their correlation across east africa the synrift sediments encountered are siliciclastics ranging from clay to coarse gravel with gypsum and ferrugineous interlayers or impregnations lithofacies and architectural analysis indicate alluvial plain delta plain nearshore delta front or lacustrine depositional environments based on the vertical stacking pattern prograding and retrograding trends of the depositional environments and climatic indicators e g conservation of feldspar gypsum and or iron hydroxide precipitation four evolutionary phases can be distinguished i a first phase between ca 14 5 and 10 0 ma is characterised by bedload dominated fluvial environment with massive sandy to gravelly bedforms feldspar rich sands rare iron impregnations and relatively low accommodation space this phase is interpreted as pre and early synrift sedimentation under a semiarid climate ii from ca 10 0 to 4 5 ma predominantly fine grained siliciclastics were deposited in a distal fluvial plain to lacustrine setting characterised by limited accommodation space fluctuation of thin beds dominance of clay and frequent iron impregnations point to a more humid climate with seasonality and weak tectonic activity iii during the third phase between 4 5 and 2 0 ma delta plain and nearshore deposits with frequent ferrugineous impregnations and rich mollusc associations occurred indicating a humid period with lake level highstands and accelerated subsidence iv during the final sedimentary interval between 2 0 and 1 5 ma gravel units reoccurred with less iron but more carbonate and gypsum impregnations and arkosic sandstones this phase recorded a general aridisation trend most probably caused by the upcoming rain barrier of the rwenzori mountains together with accelerated rift flank uplift and strong subsidence of the rift floor the results of this study are of particular importance for delineating key controls on sedimentation in the albert rift

landslide susceptibility mapping based on support vector machine a case study on natural slopes of hong kong china abstract the support vector machine svm is an increasingly popular learning procedure based on statistical learning theory and involves a training phase in which the model is trained by a training dataset of associated input and target output values the trained model is then used to evaluate a separate set of testing data there are two main ideas underlying the svm for discriminant type problems the first is an optimum linear separating hyperplane that separates the data patterns the second is the use of kernel functions to convert the original non linear data patterns into the format that is linearly separable in a high dimensional feature space in this paper an overview of the svm both one class and two class svm methods is first presented followed by its use in landslide susceptibility mapping a study area was selected from the natural terrain of hong kong and slope angle slope aspect elevation profile curvature of slope lithology vegetation cover and topographic wetness index twi were used as environmental parameters which influence the occurrence of landslides one class and two class svm models were trained and then used to map landslide susceptibility respectively the resulting susceptibility maps obtained by the methods were compared to that obtained by the logistic regression lr method it is concluded that two class svm possesses better prediction efficiency than logistic regression and one class svm however one class svm which only requires failed cases has an advantage over the other two methods as only failed case information is usually available in landslide susceptibility mapping

mass rock creep and landsliding on the huangtupo slope in the reservoir area of the three gorges project yangtze river china the huangtupo slope is one of the most noted large scale slopes with geologic hazards that cause problems related to the residential safety of immigrants in the reservoir area of the three gorges project yangtze river china the gravitational process blended with tectonic deformation large scale covering of loose debris and long term surficial mass movement complicates the huangtupo slope and gives rise to a lack of consensus on the slope nature and stability characterization of the structural geometry of the slope deformation and reconstruction of its development history are believed to be pivotal in understanding what has happened and what will happen to the slope based on a thorough field investigation combined with an electrical resistivity survey a three stage model involving mass rock creep primary landsliding partial reactivation is proposed the first stage follows the incision of the yangtze river along the axes of the guandukou syncline when huangtupo experienced long term gravitational deformation referred to as mass rock creep mass rock creep in the huangtupo slope can be classified as two basic processes toppling and deep seated creep toppling mainly occurs on the exterior part of the slope and is characterized by inclination sliding and segmentation of brittle deformation of cleavage rocks deep seated creep occurs predominantly in the interior part of the slope and brittle ductile flow folding accompanying low angle shearing is its representative deformation a primary large scale landslide occurred in the second stage as a subsequence of previous mass rock creep the landslide was ca 4 107 m3 in volume with elevations of 640 m a s l at the head and of 80 m a s l at the foot significant evidence for the landslide is the variation of attitudes of structural foliation and lineation among outcrops in the slope the last stage began subsequent to the original sliding surficial and partial reactivation on the huangtupo landslide plays a leading role in this stage two sliding events in this area in 1995 were ascribed to the partial reactivation mainly due to rainfall water level fluctuation of the yangtze river as well as human activity it was suggested that analogous failures in 1995 would continue on the huangtupo landslide and become even more frequent under the combined effect of human activity and reservoir filling

the formation of microbial metazoan bioherms and biostromes following the latest permian mass extinction abstract after the latest permian mass extinction event microbial mats filled the ecological niche previously occupied by metazoan reefs resulting in widespread microbialites this study focuses on the lipid biomarker molecular fossil and invertebrate fossil records from neotethyan platform margin sections to understand microbial metazoan bioherm formation here we find that early griesbachian thrombolitic and stromatolitic microbialites from curuk dag turkey and kuh e surmeh iran contain abundant lipid biomarkers representing input from cyanobacteria anoxygenic phototrophic bacteria sulfate reducing bacteria and halophilic archaea the biomarker inventory suggests that the microbialites were constructed by cyanobacteria dominated microbial mats biomarkers of halophilic archaea are interpreted to reflect input from the water column suggesting that the neotethys experienced at least episodically hypersaline conditions we also demonstrate that bacteria possible keratose sponges up to 50 of the carbonate is represented by the possible sponges and microconchids lived synergistically to form microbial metazoan bioherms in the immediate aftermath of the extinction along the western margin of the neotethys abundant fossils of oxygen dependent invertebrates i e microconchids bivalves gastropods brachiopods and ostracods and foraminifers were also found within these bioherms the presence of invertebrates in conjunction with abundant molecular fossils of cyanobacteria indicates an oxygenated water column even though the presence of the biomarker isorenieratane in microbialites may considered as evidence for euxinic conditions in the water column its absence in the background sediments rather points to a source organism belonging to the mat community the new finding of bioherms built in part by metazoans suggests that reef ecosystems underwent a major turnover across the extinction event and shortens the metazoan reef gap to just the uppermost changhsingian during the early triassic therefore reefal ecosystems were able to recover in oxygenated settings since the earliest griesbachian albeit in an impoverished state

a permian triassic boundary microbialite deposit from the eastern yangtze platform jiangxi province south china geobiologic features ecosystem composition and redox conditions abstract a permian triassic p tr boundary microbialite ptb microbialite deposit occurs near xiushui on the southern margin of the eastern yangtze platform south china this 2 m thick microbialite overlies uppermost permian bioclastic limestone with a 5 cm thick oolite like grainstone layer at the contact this ptb microbialite consists of lower thrombolite 1 5 m thick and an upper dendrolite 0 5 m thick the thrombolite interval is characterized by a clotted texture of reddish sparitic patches embedded in a gray micritic matrix whereas the dendrolite texture consists of brownish sparitic patches embedded within a yellow micritic matrix abundant calcified microbes occur in both the thrombolite and the dendrolite including 1 columnar and clustered fabrics which are especially rich in the thrombolite assigned as products of gakhumella or related microorganisms and 2 microspheroids 40 60 m in diameter with different interior structures these calcimicrobes are considered to have played an important role in constructing the xiushui ptb microbialite the demise of the microbialite was likely due to a sea level fall during the early griesbachian lowermost triassic which resulted in a lowering of the wave base thereby destroying the microbialite frameworks and facilitating the deposition of winnowed skeletal grainstone metazoan community structures within the microbialite changed sharply across the end permian extinction horizon which is placed at a sharp negative shift in 13 c carb quantitative analyses show that the xiushui microbialite community is similar to that of chongyang and cili microbialites this is probably because all of these microbialites grew along the margins of the lower yangtze region during the p tr transition however unlike other ptb microbialites the xiushui ecosystem contains fairly abundant metazoans which are dominated by ostracods with minor occurrences of foraminifers microgastropods and microconchids both the ostracod assemblage and the pyrite framboid analyses indicate an upper dysoxic zone to a well oxygenated condition for the xiushui microbialite this implies that some ptb microbialite ecosystems developed in conditions that were not always harsh instead some were hospitable for some metazoans to survive immediately after the end permian crisis considering that the redox conditions indicated by ptb microbialites are quite variable we infer that oxygen levels probably were not the crucial factor affecting the growth of the ptb microbialites

the application of gis based logistic regression for landslide susceptibility mapping in the kakuda yahiko mountains central japan as a first step forward in regional hazard management multivariate statistical analysis in the form of logistic regression was used to produce a landslide susceptibility map in the kakuda yahiko mountains of central japan there are different methods to prepare landslide susceptibility maps the use of logistic regression in this study stemmed not only from the fact that this approach relaxes the strict assumptions required by other multivariate statistical methods but also to demonstrate that it can be combined with bivariate statistical analyses bsa to simplify the interpretation of the model obtained at the end in susceptibility mapping the use of logistic regression is to find the best fitting function to describe the relationship between the presence or absence of landslides dependent variable and a set of independent parameters such as slope angle and lithology here an inventory map of 87 landslides was used to produce a dependent variable which takes a value of 0 for the absence and 1 for the presence of slope failures lithology bed rock slope relationship lineaments slope gradient aspect elevation and road network were taken as independent parameters the effect of each parameter on landslide occurrence was assessed from the corresponding coefficient that appears in the logistic regression function the interpretations of the coefficients showed that road network plays a major role in determining landslide occurrence and distribution among the geomorphological parameters aspect and slope gradient have a more significant contribution than elevation although field observations showed that the latter is a good estimator of the approximate location of slope cuts using a predicted map of probability the study area was classified into five categories of landslide susceptibility extremely low very low low medium and high the medium and high susceptibility zones make up 8 87 of the total study area and involve mid altitude slopes in the eastern part of kakuda mountain and the central and southern parts of yahiko mountain

early triassic calcimicrobial mounds and biostromes of the nanpanjiang basin south china stanley s model 1988 proposed that a permiantype reef fauna survived the early triassic reefless period in yet undiscovered refuges in the ancestral pacific ocean and then reappeared as the builders of middle triassic reefs flugel 1994 in contrast suggested that the middle triassic reefbuilding fauna are not holdovers from the permian but bear only a superficial resemblance to permian fossils recent publications reflect a consensus that the early triassic lacked reefs and reef mounds although some authors acknowledged the possibility that reef like structures may have existed in poorly explored areas such as south china and russia senowbari daryan et al 1993 flugel 1994 it is shown herein that calcimicrobial framework mounds and biostromes existed in the early triassic in the nanpanjiang basin of south china organic framework in this paper refers to a three dimensional biologically constructed network of calcified fossils that forms a rigid mass and supports an interconnected network of internal cavities that were open during accumulation although the calcimicrobial frameworks discussed herein are much smaller than frameworks of modern metazoan reefs the term framestone is more appropriate for these fabrics than other reef rock terms such as bindstone or bafflestone embry and klovan 1971 these calcimicrobial mounds and biostromes are important as the first organic framestones documented from the early triassic

a comparative study of support vector machine and logistic model tree classifiers for shallow landslide susceptibility modeling the main aim of this study was to evaluate and compare the results of two data mining algorithms including support vector machine svm and logistic model tree lmt for shallow landslide modelling in kamyaran county where located in kurdistan province iran a total of 60 landslide locations were identified using different sources and randomly divided into a ratio of 70 30 for landslide modeling and validation process after that 21 conditioning factors with a raster resolution of 20 m based on the information gain ratio igr technique were selected performance of the models was evaluated using area under the receiver operating characteristic curve auroc and also several statistical based indexes results depicted that only eight factors including distance to river river density stream power index spi rainfall valley depth topographic wetness index twi solar radiation and plan curvature were known more effective for landslide modeling using training data set the results also revealed that the svm model auroc 0 882 outperformed and outclassed the lmt model auroc 0 737 therefore analysis and comparison of the results showed that the svm model by rbf function performed well for landslide spatial prediction in the study area eventually the findings of this study can be useful for land use planning reducing the risk of landslide and decision making in areas prone to landslide

the end permian regression in south china and its implication on mass extinction abstract records of more than 20 permian triassic boundary ptb sections from south china show that widespread end permian regression took place in whole south china timing of the low ebb of this regression was pinpointed to the clarkina meishanensis and hindeodus changxingensis zones biostratigraphic and paleogeographic studies at conodont zonation level reveal that the yangtze carbonate platform and isolated small carbonate platforms in the hunan guizhou guangxi hgg basin experienced sedimentary hiatus during these two zones which lasted about 50 100 kya meanwhile the basinal areas namely the northern marginal basin of yangtze platform and the hunan guizhou guangxi basin have continuous conodont zonation with silicious and ashbed deposits the basinal areas show two negative 13c shifts during the ptb interval from clarkina yini zone to isarcicella isarcica zone while on the platforms there is usually only one negative shift because the early shift at c meishanensis zone was lost during hiatus the end permian regression and successive rapid transgression taking place at the ptb casted important effects to the pattern and process of the ptb mass extinction the depositional hiatus hitherto underestimated will necessitate reassessment of some interpretations on the causes and results of that extinction

a preliminary study on the location of the stabilizing piles for colluvial landslides with interbedding hard and soft bedrocks abstract the paper presents a study on the location determination of stabilizing piles in colluvial landslides with the interbedding of hard and soft bedrocks a double arc model is proposed to describe the shape of sliding surface of colluvial landslides and the corresponding slope surface can be divided into three types namely the concave type straight line type and convex type respectively the driving force of colluvial landslides and interbedding characteristics of hard and soft bedrocks are two important factors affecting the determination of optimal location for stabilizing piles the results indicate that the stabilizing effect of the piles mainly depends upon the hard bedrock the effect of the location of hard layer bedrock on the pile deformation is represented by the location coefficient it is found that the optimal location of stabilizing pile locates where both top and bottom hard layers are present and the location with a top soft layer is unfavorable particularly when the hard layer has a large location coefficient the case study of yanguan landslide illustrates that the location of stabilizing pile is determined with the proposed method is effective with a considerable decrease in both the displacement and internal force of the stabilizing piles

a comparative study of sequential minimal optimization based support vector machines vote feature intervals and logistic regression in landslide susceptibility assessment using gis landslide susceptibility assessment using gis has been done for part of uttarakhand region of himalaya india with the objective of comparing the predictive capability of three different machine learning methods namely sequential minimal optimization based support vector machines smosvm vote feature intervals vfi and logistic regression lr for spatial prediction of landslide occurrence out of these three methods the smosvm and vfi are state of the art methods for binary classification problems but have not been applied for landslide prediction whereas the lr is known as a popular method for landslide susceptibility assessment in the study a total of 430 historical landslide polygons and 11 landslide affecting factors such as slope angle slope aspect elevation curvature lithology soil land cover distance to roads distance to rivers distance to lineaments and rainfall were selected for landslide analysis for validation and comparison statistical index based methods and the receiver operating characteristic curve have been used analysis results show that all these models have good performance for landslide spatial prediction but the smosvm model has the highest predictive capability followed by the vfi model and the lr model respectively thus smosvm is a better model for landslide prediction and can be used for landslide susceptibility mapping of landslide prone areas

the evolution of microbialite forms during the early triassic transgression a case study in chongyang of hubei province south china abstract the widespread development of microbialites in shallow areas of the tethys ocean at the start of the early triassic reflects the deterioration of marine ecosystems in the aftermath of the extinction that marked the demise of the majority of palaeozoic marine faunas here we present a study of the evolving microbialite forms and associated biotic assemblages of this pioneering microbialite interval from exposures at chongyang hubei province china this research provides a perspective on the effects of eustatic transgression on marine ecosystems as water depths increased at the beginning of mesozoic through the study of the changing forms microfacies and distribution of microbialites microbialite forms evolved from stratiform stromatolites to a sequence of tabular thrombolites with an intercalated layer of columnar stromatolites followed by domical thrombolites that were overlain in turn by oolites the stratiform stromatolites contain poorly preserved remains of calcified cyanobacteria but microfossils with chambered structure can also be seen metazoan fossils increased from the base of the overlying tabular thrombolite reflecting increasing biodiversity with deepening of seawater the occurrence of columnar stromatolites within the tabular thrombolite may indicate a temporary sea level shallowing foraminiferans and other metazoans are absent within the columnar stromatolites but spherical cyanobacterial remains are extremely abundant well preserved calcified cyanobacteria may reflect an absence of metazoan predation and or carbonate supersaturation of seawater as water deepened domical thrombolites developed and the more complex seafloor relief created varied niches between and within the domes that harboured more ecologically diverse communities during the process of transgression within the microbialite interval carbon isotopes exhibit a negative relationship with biodiversity implying that upwelling of anoxic deep ocean water if associated with the negative excursion of carbon isotope values did not inhibit the diversification of benthic organisms at least on shallow carbonate platforms in the period immediately after the end permian mass extinction

estimating the quality of landslide susceptibility models we present a landslide susceptibility model for the collazzone area central italy and we propose a framework for evaluating the model reliability and prediction skill the landslide susceptibility model was obtained through discriminant analysis of 46 thematic environmental variables and using the presence of shallow landslides obtained from a multi temporal inventory map as the dependent variable for statistical analysis by comparing the number of correctly and incorrectly classified mapping units it is established that the model classifies 77 0 of 894 mapping units correctly model fitting performance is investigated by comparing the proportion of the study area in each probability class with the corresponding proportion of landslide area we then prepare an ensemble of 350 landslide susceptibility models using the same landslide and thematic information but different numbers of mapping units this ensemble is exploited to investigate the model reliability including the role of the thematic variables used to construct the model and the model sensitivity to changes in the input data by studying the variation of the model s susceptibility estimate the error associated with the susceptibility assessment for each mapping unit is determined this result is shown on a map that complements the landslide susceptibility map prediction skill of the susceptibility model is then estimated by comparing the forecast with two recent event inventory maps the susceptibility model is found capable of predicting the newly triggered landslides a general framework for testing a susceptibility model is proposed including a scheme for ranking the quality of the susceptibility assessment

artificial neural networks and cluster analysis in landslide susceptibility zonation a landslide susceptibility analysis is performed by means of artificial neural network ann and cluster analysis ca this kind of analysis is aimed at using anns to model the complex non linear relationships between mass movements and conditioning factors for susceptibility zonation in order to identify unstable areas the proposed method adopts ca to improve the selection of training validation and test records from data managed within a geographic information system gis in particular we introduce a domain specific distance measure in cluster formation clustering is used in data pre processing to select non landslide records and is performed on the whole dataset excluding the test set landslides susceptibility analysis is carried out by means of anns on the so generated data and compared with the common strategy to select random non landslide samples from pixels without landslides the proposed method has been applied in the brembilla municipality a landslide prone area in the southern alps italy the results show significant differences between the two sampling methods the classification of the test set previously separated and excluded from the training data is always better when the non landslide patterns are obtained using the proposed cluster sampling the case study validates that by means of a domain specific distance measure in cluster formation it is possible to introduce expert knowledge into the black box modelling method implemented by anns to improve the predictive capability and the robustness of the models obtained

the influence of preexisting structure on the evolution of the cenozoic malawi rift east african rift system this paper analyzes the importance of preexisting structure for the evolution of the cenozoic malawi rift which constitutes the southernmost part of the western branch of the east african rift system kinematic analyses demonstrate that the regional extension direction rotated clockwise from ene to se during rifting cenozoic rift faults of dip oblique and strike slip character rejuvenated crustal structures whenever those were properly oriented with respect to the extension directions depending on these boundary conditions the rift attempts to find the easiest pathway in order to develop in a mechanically modest way proterozoic basement structures represent the basic anisotropy which already influenced pre cenozoic rifts and also the cenozoic malawi rift amongst these basement structures pan african retrograde to cataclastic strike slip shear zones have the strongest influence on later rift structures rift related transfer faults appear as differently striking passive structures and their orientation seems to be controlled by a variety of steep basement structures retrograde shear zones foliation planes and fracture arrays

combining landslide susceptibility maps obtained from frequency ratio logistic regression and artificial neural network models using aster images and gis landslide related factors were extracted from advanced spaceborne thermal emission and reflection radiometer aster images and integrated techniques were developed applied and verified for the analysis of landslide susceptibility in boun korea using a geographic information system gis digital elevation model dem lineament normalized difference vegetation index ndvi and land cover factors were extracted from the aster images for analysis slope aspect and curvature were calculated from a dem topographic database using the constructed spatial database the relationships between the detected landslide locations and six related factors were identified and quantified using frequency ratio fr logistic regression lr and artificial neural network ann models these relationships were used as factor ratings in an overlay analysis to create landslide susceptibility indices and maps three landslide susceptibility maps were then combined and applied as new input factors in the fr lr and ann models to make improved susceptibility maps all of the susceptibility maps were verified by comparison with known landslide locations not used for training the models the combined landslide susceptibility maps created using three landslide related input factors showed improved accuracy 87 00 in fr 88 21 in lr and 86 51 in ann models compared to the individual landslide susceptibility maps 84 34 in fr 85 40 in lr and 74 29 in ann models generated using the six factors from the aster images

geomorphic evolution of the yangtze gorges and the time of their formation abstract the three gorges of the yangtze link its upper rocky valley to downstream alluvial sections a series of stepped landforms exist in the three gorges area the sichuan basin upstream and the jianghan basin downstream these landforms are characterized by two planation surfaces one erosional surface and up to seven terraces the higher planation surface named the exi surface 1800 2000 m a s l and the lower planation surface 1200 1500 m were probably formed in the tertiary prior to 3 4 3 6 ma b p no correlation seems to exist between the drainage networks of earlier period with the present yangtze system it is suggested that the erosional surface found in the study area at 800 1200 m in elevation above sea level was formed in late pliocene of early pleistocene during this period following the last planation event the ancestral yangtze might have begun to adjust its drainage network the seven terraces well developed along the eastern sichuan basin and the three gorges date from early to late pleistocene 1 16 0 01 ma b p the chronostratigraphic evidence and diagnostic sediments are generally comparable in time and space from the sichuan basin through the three gorges to the jianghan basin therefore the present study proposes that the three gorges were cut not later than the initiation of the earliest terrace the fluvial landforms in the yangtze gorges are characterized also by valley in valley cross sections i e an older u shaped valley cut by a younger v shaped valley a tectonic rise accompanied by a rapid downcutting of the river channels predominated in the region

the added value of a regional landslide susceptibility assessment the western branch of the east african rift abstract predicting landslide occurrence is of key importance for understanding the geomorphological development of mountain environments as well as to assess the potential risk posed by landsliding to human societies in such environments global landslide susceptibility models use a generic model formulation to predict landslide susceptibility anywhere on the planet from openly available data regional models on the contrary use local information on landslide occurrence to constrain model parameters and may also benefit from better spatial information with respect to controlling factors this study aims to investigate the added value of the construction of regional landslide susceptibility models versus global and continental models in the western branch of the east african rift a data scarce landslide prone tropical environment first a comprehensive landslide database containing 6446 instances was compiled for the study area using google earth imagery second three regional data driven landslide susceptibility models were developed third the efforts to construct these regional models were quantified by analysing how their quality is impacted by 1 the use of more accurate regional peak ground acceleration and geology data and 2 an increasing inventory size fourth regional and global continental models were compared in terms of predictive power and geomorphological plausibility we observe that global continental landslide susceptibility models are capable of identifying landslide prone areas but lack prediction power and geomorphological plausibility when compared to our regional models importantly this difference in quality is not driven by the use of more accurate and detailed geology and peak ground acceleration data but rather by the use of a detailed regional landslide inventory to calibrate the models we also show that the model quality only increases marginally beyond a certain inventory size we conclude that the regional landslide susceptibility assessment does provide an added value compared to existing global models in terms of geomorphological plausibility and model performance whereby the largest gain is to be found in the construction of a regional landslide inventory rather than the investment in more detailed covariates or the application of more complex modelling techniques the latter suggests that the role of controlling variables depends to some extent on the regional context making adequate susceptibility predictions proves difficult when local conditions are not accounted for by means of a regional inventory

exploring discrepancies between quantitative validation results and the geomorphic plausibility of statistical landslide susceptibility maps abstract empirical models are frequently applied to produce landslide susceptibility maps for large areas subsequent quantitative validation results are routinely used as the primary criteria to infer the validity and applicability of the final maps or to select one of several models this study hypothesizes that such direct deductions can be misleading the main objective was to explore discrepancies between the predictive performance of a landslide susceptibility model and the geomorphic plausibility of subsequent landslide susceptibility maps while a particular emphasis was placed on the influence of incomplete landslide inventories on modelling and validation results the study was conducted within the flysch zone of lower austria 1 354 km 2 which is known to be highly susceptible to landslides of the slide type movement sixteen susceptibility models were generated by applying two statistical classifiers logistic regression and generalized additive model and two machine learning techniques random forest and support vector machine separately for two landslide inventories of differing completeness and two predictor sets the results were validated quantitatively by estimating the area under the receiver operating characteristic curve auroc with single holdout and spatial cross validation technique the heuristic evaluation of the geomorphic plausibility of the final results was supported by findings of an exploratory data analysis an estimation of odds ratios and an evaluation of the spatial structure of the final maps the results showed that maps generated by different inventories classifiers and predictors appeared differently while holdout validation revealed similar high predictive performances spatial cross validation proved useful to expose spatially varying inconsistencies of the modelling results while additionally providing evidence for slightly overfitted machine learning based models however the highest predictive performances were obtained for maps that explicitly expressed geomorphically implausible relationships indicating that the predictive performance of a model might be misleading in the case a predictor systematically relates to a spatially consistent bias of the inventory furthermore we observed that random forest based maps displayed spatial artifacts the most plausible susceptibility map of the study area showed smooth prediction surfaces while the underlying model revealed a high predictive capability and was generated with an accurate landslide inventory and predictors that did not directly describe a bias however none of the presented models was found to be completely unbiased this study showed that high predictive performances cannot be equated with a high plausibility and applicability of subsequent landslide susceptibility maps we suggest that greater emphasis should be placed on identifying confounding factors and biases in landslide inventories a joint discussion between modelers and decision makers of the spatial pattern of the final susceptibility maps in the field might increase their acceptance and applicability

statistical analysis of landslide susceptibility at yongin korea the aim of this study is to evaluate the susceptibility of landslides at yongin korea using a geographic information system gis landslide locations were identified in the yongin area from interpretation of aerial photographs field surveys and maps of the topography soil type timber cover and geology these data were collected and constructed into a spatial database using gis the factors that influence landslide occurrence such as slope aspect and curvature of topography were calculated from the topographic database texture material drainage and effective soil thickness were extracted from the soil database and type age diameter and density of timber were extracted from the forest database lithology was extracted from the geological database and land use was classified from the landsat tm satellite image landslide susceptibility was analyzed using the landslide occurrence factors by probability and logistic regression methods the results of the analysis were verified using the landslide location data the validation results showed satisfactory agreement between the susceptibility map and the existing data on landslide location the gis was used to analyze the vast amount of data efficiently and statistical programs were used to maintain specificity and accuracy the results can be used to reduce associated hazards and to plan land use and construction

the link between biomineralization and fossilization of bacteria insights from field and experimental studies abstract fossil biominerals and fossils of microorganisms in ancient rocks contain important biogeochemical signals decoding this record may reveal crucial information about the evolution of life on earth and terrestrial paleoenvironments however the identification of traces of life especially in very old rocks is extremely challenging because the morphological and chemical signatures of biominerals and microfossils are subtle of microscopic size and inevitably altered with aging in this review we stress on the fact that biomineralization is often the first step of fossilization and produces particular chemical structural and morphological features that can be preserved in fossil biominerals or microfossils with a special focus on fe biomineralization the taphonomic processes affecting biominerals and microfossils and altering their morphology and or chemical composition over time are then discussed in light of experimental fossilization simulations and field sample analyses we suggest that taxonomic biases observed in the fossil record may be related to differential abilities of species to trigger biomineralization this calls for studies of the effective biomineralizing activity and fossilization potential of each species present in highly diverse natural microbial communities finally recent analytical developments leave little doubt that very substantial progress in the study of biomineralization processes and ancient biostructures will be achieved in the near future

geohazards in the three gorges reservoir area china lessons learned from decades of research abstract the impoundment of the 660 km long reservoir behind the huge three gorges dam the world s largest hydropower station increased regional seismicity and reactivated severe geohazards before the reservoir filling was initiated in 2003 the region had approximately two earthquakes per year with magnitudes between 3 0 and 4 9 after the full impoundment in 2008 approximately 14 earthquakes per year occurred with magnitudes between 3 0 and 5 4 in addition hundreds of landslides were reactivated and are now in a state of intermittent creep many landslides exhibit step like annual pattern of displacement in response to quasi regular variations in seasonal rainfall and reservoir level additional problems include rock avalanches impulse waves and debris flows the seriousness of these events motivated numerous studies that resulted in 1 better insight into the behavior and evolution mechanism of geohazards in the three gorges reservoir area tgra 2 implementation of monitoring and early warning systems of geohazards and 3 design and construction of preventive countermeasures including lattice anchors stabilizing piles rock bolts drainage canals and tunnels and huge revetments this paper reviews the hydro geologic setting of tgra geohazards examines their occurrence and evolution in the past few decades offers insight learned from extensive research on tgra geohazards and suggests topics for future research to address the remaining challenges

zonation of the landslide hazards in the forereservoir region of the three gorges project on the yangtze river on the basis of the investigation and statistic analysis of the landslide hazards in the forereservoir region of the three gorges project on the yangtze river the major factors that are found to have affected the slope stabilities are outlined and a zonation of landslide hazards of the region is made using an integrated information model it is divided into destructive disastrous slightly disastrous likely disastrous and essentially non disastrous areas the first two cover an area of less than 5 of the total region and are at a distance of more than 20 km from the three gorges dam and so a landslide over there will impose no direct impact to the tgp but may effect to some degree the navigation of the yangtze river and nearby highway transportation reservoir slopes and building of cities and towns

landslide susceptibility mapping based on rough set theory and support vector machines a case of the three gorges area china abstract this paper aims to develop a novel hybrid model for assessing landslide susceptibility at the regional scale using multisource data to produce a landslide susceptibility map of the zigui badong area near the three gorges reservoir china this area is subject to anthropogenic influences because the reservoir s water level fluctuates cyclically between 145 and 175 m in addition the area suffers from extreme rainfall events due to the local climate the area has experienced significant and widespread landslide events in recent years in our study a novel hybrid model is proposed to produce landslide susceptibility maps using geographical information systems gis and remote sensing the hybrid model is based on rough set rs theory and a support vector machine svm rs theory is employed as an attribute reduction tool to identify the significant environmental parameters of a landslide and an svm is used to predict landslide susceptibility four data domains were considered in this research geological geomorphological hydrology and land cover the original group of 20 environmental parameters and 202 landslides were used as the inputs to produce a landslide susceptibility map according to the map 19 7 of the study area was identified as medium and high susceptibility zones encompassing 89 5 of the historical landslides the results indicate high levels of landslide hazard in and around the main inhabited areas such as badong county and other towns as well as in rural residential areas and transportation areas along the yangtze river and its tributaries the predicted map indicates a good correlation between the classified high hazard areas and slope failures confirmed in the field furthermore the quality of the proposed model was comprehensively evaluated including the degree of model fit the robustness of the model the uncertainty associated with the probabilistic estimate and the model prediction skill the proposed model was also compared with the general svm which demonstrated that the hybrid model has superior prediction skill and higher reliability and confirmed the usefulness of the proposed model for landslide susceptibility mapping at a regional scale

controls of sedimentation in the malawi rift valley central africa abstract the malawi rift is the southermost classic rift valley trough in the cenozoic african rift valley system much of its floor is flooded by lake malawi which is approximately 570 km long 60 km across and up to 500 m deep this rift basin is a potentially useful analogue of many economically important ancient sedimentary troughs rift valley structures are extremely important in controlling both the distribution of sediments in the basin as a whole and also details of sedimentation on a local scale on the basin wide scale an important association between the type of rift boundary structure and amount of rift floor subsidence is recognised this association appears to apply to several section of the african rift system pre rift topography is major control on the position of major rivers and their deltas or turbidite fans along the basin margin the area of pre rift drainage network captured in the course of rift movements is a significant factor in the hydrologic budget of the basin climate is however the dominant control on the hydrologic budget and at present the basin is flooded to overflow level prevailing winds are important in beach ridge and back beach aeolian dune development climatic conditions produce thermal stratification of the lake with an oxic epilimnion down to 250 m depth overlying an anoxic hypolimnion the oxic bottom waters in the shallower parts of the lake appear to promote iron precipitation in the sediments