the three dimensional morphology of arrays of echelon and sigmoidal mineral filled fractures data from north cornwall arrays of mineral filled echelon sigmoidal fractures in cobbles of sandstone from the crackington formation of north cornwall were examined by cutting serial sections in three dimensions each array consists of a set of blade like mineral filled fractures these blades project as a fringe from the single but composite fracture that forms through their linkage linkage takes place as the strips of rock bridges between blades fail through cross fracture cross fractures give rise to the steps that mark the margins of the composite fractures so formed bridges show little penetrative deformation arrays are not zones of high ductile strain displacement is a consequence of dilatation echelon fractures were formed and opened by intruding hydrothermal fluid

new insights into the 1963 vajont slide using 2d and 3d distinct element method analyses the 1963 vajont rock slide is studied using the distinct element method dem two dimensional 2d and three dimensional 3d dem models were constructed based on information published in the literature in this study a strength reduction approach was used to calculate the slide surface friction angles required for stability the influence of several parameters was investigated in 2d namely the reservoir water level the shear stiffness of the slide surface the rock mass strength the rock mass deformability and rock joint patterns of the parameters which have been investigated the most important parameter was found to be the reservoir water level the rock mass deformability which is neglected by other investigators is also found to be important from the 3d analyses the failure friction angle was found to be sensitive to the assumptions made on the eastern boundary and could affect the failure friction angle by approximately 3 the slope was found to exhibit signs of failure beginning from s

microstructural analysis and calcite piezometry on hydrothermal veins insights into the deformation history of the cocos plate at site u1414 iodp expedition 344 in this study we present microstructural data from hydrothermal veins in the sedimentary cover and the igneous basement recovered from hole u1414a integrated ocean drilling program iodp expedition 344 costa rica seismogenesis project to constrain deformation mechanism operating in the subducting cocos plate cathodoluminescence studies mechanical e twin piezometry and electron backscatter diffraction ebsd analyses of carbonate veins were used to give insights into the deformation conditions and to help to understand the tectonic deformation history of the cocos plate offshore costa rica analyses of microstructures in the sedimentary rocks and in the basalt of the igneous basement reveal brittle deformation as well as crystal plastic deformation of the host rock and the vein material cathodoluminescence images showed that in the basalt fluid flow and related precipitation occurred over several episodes the differential stresses obtained from two different piezometers using the same parameter twin density indicate various mean differential stresses of 49 11 and 69 30 mpa and ebsd mapping of calcite veins reveals low angle subgrain boundaries deformation temperatures are restricted to the range from 170 c to 220 c due to the characteristics of the existing twins and the lack of high temperature intracrystalline deformation mechanisms 220 c the obtained results suggest that deformation occurred over a period associated with changes of ambient temperatures occurrence of fluids and hydrofracturing induced differential stresses due to the bending of the plate at the trench and related seismic activity

late paleozoic glacial episodes in gondwanaland reflected in transgressive regressive depositional sequences in euramerica the late paleozoic glaciation of gondwanaland comprised two short episodes in the famennian i and visean ii confined to brazil and adjacent northwest africa and a long episode that started in the namurian iiia of eastern australia and bolivia argentina expanded to cover much of gondwanaland in the stephanian asselian iiib and collapsed in the early sakmarian iiic dropstones in eastern australia indicate that small ice centers lingered to the kazanian across the belt of low latitudes north of gondwanaland short ranging fossils in widespread shallow marine and paralic deposits indicate synchronous deposition of transgressive regressive sequences in different parts of euramerica these sequences correlate with glacial events in gondwanaland at three levels a four major regressions in euramerica in the famennian 1 visean 2 namurian 3 stephanian 4 and the tastubian transgression that preceded the sterlitamakian regression 5 also recorded in gondwanaland correlate with glacial episodes i ii and iiia iiib and iiic b the time interval of cyclothemic deposition in euramerica brigantian or latest visean to sterlitamakian correlates with that of glacial episode iii and c the dominant period of the euramerican cyclothems as estimated from the middle and late pennsylvanian deposits of the mid continent of north america and of the thickest known gondwanaland glacigenic sediment the earliest permian lyons group of western australia is 0 4 ma equivalent in turn to the long orbital eccentricity period of the quaternary ice age and the dominant period of fluctuation of the late miocene antarctic ice cap the three levels of correlations confirm wanless and shepard9s 1936 hypothesis that the late paleozoic cyclothems are controlled largely by sea level fluctuations related to the gondwanaland glaciation

giant bauxite deposits of south china multistage formation linked to late paleozoic ice age lpia eustatic fluctuations abstract the lower carboniferous jiujialu formation bauxite deposits at zunyi northern guizhou are distinguished by their great thickness to 110 m and cyclic alternation of bauxite ore and bauxitic claystone layers these features are typical of the kazakhstan subtype of karst bauxite deposits although the genesis of this type of deposit is poorly understood here we undertook a petrological mineralogical and geochemical study of the zunyi deposit in drillcore zk5600 to gain insights into its formation history the zunyi profile contains seven bauxite cycles as recorded by petrological mineralogical and geochemical features indicating a multistage formation history each cycle is composed of a lower bauxitic claystone layer and an upper bauxite ore layer the bauxite ore is characterized by high al2o3 high al mineral diaspore and low sio2 content positive ce anomalies high cia values 90 and strong depletion of major elements indicate that the bauxite ore formed through intense chemical weathering and leaching in a well drained soil environment the bauxitic claystone is characterized by relatively lower al2o3 and higher sio2 and clay mineral mostly illite content this lithology exhibits both negative and positive ce anomalies moderate cia values 70 80 and enrichment of some elements e g fe k indicating formation through moderate chemical weathering in a poorly drained soil environment secular variations in chemical weathering intensity and soil drainage conditions were linked to regional hydrologic changes during the early carboniferous the zunyi area was located in a karstified coastal upland setting and its hydrologic system was affected by glacio eustatic fluctuations high groundwater table elevations during eustatic highstands led to formation of bauxitic claystone layers whereas low groundwater table elevations during eustatic lowstands led to formation of bauxite ore layers

determination of residual strength parameters of jointed rock masses using the gsi system abstract the geological strength index gsi system proposed in 1995 is now widely used for the estimation of the rock mass strength and the rock mass deformation parameters the gsi system concentrates on the description of two factors rock structure and block surface conditions the guidelines given by the gsi system are for the estimation of the peak strength parameters of jointed rock masses there are no guidelines given by the gsi or by any other system for the estimation of the rock mass residual strength that yield consistent results in this paper a method is proposed to extend the gsi system for the estimation of a rock mass s residual strength it is proposed to adjust the peak gsi to the residual gsir value based on the two major controlling factors in the gsi system the residual block volume v b r and the residual joint condition factor j c r methods to estimate the residual block volume and joint condition factor are presented the proposed method for the estimation of rock mass s residual strength is validated using in situ block shear test data from three large scale cavern construction sites and data from a back analysis of rock slopes the estimated residual strengths calculated using the reduced residual gsir value are found to be in good agreement with field test or back analyzed data

curved vein fibres an alternative explanation abstract veins occurring at the edge of the dextral indian islands fault newfoundland are folded in response to a fault parallel ductile shear the veins which locally constitute a penetrative fabric element at outcrop scale are composed mainly of calcite and have a narrow rim of quartz and chlorite both the calcite and quartz are generally fibrous and lattice distortion in the calcite is not commensurate with the observed degree of fibre curvature this observation supports the popular view that curved fibres grow curved as they track the vein opening vector it is demonstrated however that the curvature in the material described here is due to deformation and that the lack of strong lattice distortion is due in part to polygonization and to recrystallization all observations are consistent with both the calcite and the quartz fibres having grown perpendicular to the vein walls the chlorite orientation is controlled by the orientation of mica grains in the country rock in some veins markers make it possible to define the net opening direction and in all examples it is demonstrated that the direction has not been tracked by the fibres since this conclusion may be more generally applicable caution should be exercised in interpreting kinematics on the basis of fibre geometry where vein density is high the veins and country rock screens separating them form a multilayer sequence that is folded into fairly harmonic folds the folds appear to have a cleavage transected relationship to the regional cleavage but the cleavage is shown to predate the folds

vein morphology host rock deformation and the origin of the fabrics of echelon mineral veins abstract a system of sigmoidal echelon veins from a sample of sandstone from the upper carboniferous culm sequence of southwest england is described veins are separated from one another by strips of sandstone and divided internally by thin seams with crack seal fabrics the latter extend as thin veins into the sandstone host rock without change of fabric seams appear to be merely parts of crack seal veins formed in a first phase of deposition in only minutely opened fractures this phase ended as rates of fracture opening greatly increased to allow for this widespread opening host rock between dilatating fractures sandstone strips and seams had to be deformed this deformation was limited however to rotation bending and fracture shear displacement was a function of dilatation not zone parallel ductile shear strain the textures of the quartz and carbonate aggregates filling the sigmoidal veins show that second phase crystallization took place into cavities opening more rapidly than growth was able to fill them growth for the greater part took place from fibres in seams and not off vein walls of the sandstone host rock coarsest aggregates fill the arcs of folds in seams where rates of vein opening might be expected to have been highest and the scope for competitive cavity growth greatest

geomorphometry and landform mapping what is a landform abstract starting from a concept of the land surface its definition and subdivision from digital elevation models dems is considered high resolution dems from active remote sensing form a new basis for geomorphological work which is moving on from consideration of whether data are accurate enough to how the surface of interest can be defined from an overabundance of data discussion of the operational definition and delimitation of specific landforms of varying degrees of difficulty from craters to mountains is followed by the applicability of fuzzy boundaries scaling usually allometric is shown to be compatible with the scale specificity of many landforms this is exemplified by glacial cirques and drumlins classification of a whole land surface is more difficult than extraction of specific landforms from it well dissected fluvial landscapes pose great challenges for areal analyses these are tackled by the delimitation of homogeneous elementary forms and or land elements in which slope position is considered the boundaries are mainly breaks in gradient or aspect but may also be in some type of curvature breaks in altitude are rare elementary forms or land elements are grouped together into functional regions landforms such as hill sheds it may often be useful to recognise fuzziness of membership or core and periphery of a surface object plains and etched or scoured surfaces defy most of these approaches and general geomorphometry remains the most widely applicable technique it has been applied mainly within arbitrary areas and to some extent to drainage basins but more experimentation with mountain ranges and other landforms or landform regions is needed geomorphological mapping is becoming more specialised and its legends are being simplified its incorporation into geographical information systems gis has required greater precision with definitions and the separation of thematic layers so that it is converging with specific geomorphometry and becoming more flexible and more applicable with a broader range of visualisation techniques

ring shear tests on soil from the vaiont landslide slip surface the paper presents results from ring shear tests carried out on two samples from the slip surface of the vaiont landslide in north italy the tests were carried out at slow and fast rates of shearing in order to determine values of the coefficient of friction appropriate to static and dynamic aspects of the landslide both samples showed a significant loss of strength negative rate effect up to 60 below the slow residual strength when sheared at rates of shearing greater than 100 mm min the observed loss of strength may explain the high acquired velocity of the landslide or alternatively some combination of this and other mechanisms may have taken place le papier presente les resultats d essais de cisaillement par anneau effectues sur deux echantilions preleves sur la surface de cisaillement du glissement de terrain vaiont dans le nord de l italie les essais ont ete menes avec des vitesses de cisaillement lentes et rapides de maniere a pouvoir determiner les valeurs des coefficients de frotteme

microfacies and carbon isotope records of mississippian carbonates from the isolated bama platform of youjiang basin south china possible responses to climate driven upwelling changes in mississippian global paleogeography derived from the reconfiguration of the continents have been suggested to result in a change in oceanic circulation carbon cycling as well as in global cooling here integrated 13ccarb chemostratigraphy and foraminiferal biostratigraphy across the mississippian late tournaisian visean early serpukhovian mfz6 mfz16 foraminiferal biozones of the gongchuan section located in the isolated bama platform in the youjiang basin south china are presented the 13ccarb trend shows an abrupt decline during late visean asbian early brigantian mfz13 14 this decline is also observed in subequatorial western euramerica whereas coeval sections in subequatorial eastern euramerica show consistently elevated 13c values across the entire visean the 13c decline in western euramerica and the south china block eastern paleo tethys coincides with a global regression with a suggested glacioeustatic origin the onset of high frequency climate and sea level oscillations and the closure of the rheic seaway between euramerica and gondwana we propose a model explaining the divergence of 13c records resulting from the closure of the rheic seaway and development of upwelling zones in the western margin of euramerica and the eastern paleo tethys realm quantitative microfacies analysis across the mississippian succession in the gongchuan section shows facies independent disappearance of corals and increased proportion of cortoids and filter feeding organisms at the onset of the asbian 13c decline which may support an increase in nutrient level that can be expected as a result of upwelling

a laboratory simulation of fibrous veins some first observations abstract following work by stephen taber 80 years ago we describe vein like arrays of parallel fibrous crystals that grow evaporatively between pairs of brine soaked porous ceramic substrates crystals of solute grow antitaxially from fixed sites on the substrate forcing older parts of the crystals away from the growth site without benefit of any long range cracking parallel to the substrate the nutrients for growth are fed to the growth site advectively or diffusively through the substrate blocks themselves not along the plane of the vein we call such crystallization taber growth and suggest as taber did that it might be an important mechanism for non evaporative fibrous vein development in nature the taber growth model provides a ready explanation for the ability of fibers to track vein opening directions and tracking is indeed the rule in our samples though exceptions are also seen our results lend support to ideas already in the literature that fibrous veins are not necessarily products of a crack seal process and that fibrous veins are not necessarily syntectonic our observations also raise questions about criteria for recognition of syntaxial fibrous veins and underscore the importance of finding new criteria for recognition of the younging direction along fibers

cyclothem digital correlation and biostratigraphy across the global moscovian kasimovian gzhelian stage boundary interval middle upper pennsylvanian in north america and eastern europe the long standing difficulty of correlating pennsylvanian strata among provincial faunal regions is resolved by effecting digital correlation of major glacial eustatic cyclothems that represent high stands when certain species achieved more global distribution than usual in the late moscovian early gzhelian late desmoinesian early virgilian succession in the midcontinent united states several major cyclothems are correlated by both conodont species in common and cyclothem scale with cyclothems in russia moscow basin and ukraine donets basin and the remaining cyclothems fit into the framework by position and scale in this way the suggested event marker for the global kasimovian gzhelian stage boundary first appearance of idiognathodus simulator is supported while possible event markers for the moscovian kasimovian boundary await further evaluation

microstructural observations on natural syntectonic fibrous veins implications for the growth process abstract syntectonic antitaxial and ataxial fibrous veins were investigated using sem microprobe cathodoluminescence cl and optical microscopy in antitaxial calcite veins fibres and surrounding selvage grew simultaneously with similar growth rates of crystallographically differently oriented grains new material precipitated at the vein margin in antitaxial and bi mineralic ataxial microstructures bridges of country rock material formed during vein growth in an initial en echelon vein system in our antitaxial and bi mineralic ataxial samples the spacing of solid inclusions does not reflect individual crack seal openings

fault roughness at seismogenic depths from lidar and photogrammetric analysis fault surface roughness is a principal factor influencing earthquake mechanics and particularly rupture initiation propagation and arrest however little data currently exist on fault surfaces at seismogenic depths here we investigate the roughness of slip surfaces from the seismogenic strike slip gole larghe fault zone exhumed from ca 10 km depth the fault zone exploited pre existing joints and is hosted in granitoid rocks of the adamello batholith italian alps individual seismogenic slip surfaces generally show a first phase of cataclasite production and a second phase with beautifully preserved pseudotachylytes of variable thickness we determined the geometry of fault traces over almost five orders of magnitude using terrestrial laser scanning lidar ca 500 to 1 10 m is not anisotropic and less evolved than at smaller scales these observations are consistent with an evolution of roughness due to fault surface processes that takes place only at scales smaller or comparable to the observed net slip differences in roughness evolution between shallow and deeper faults the latter showing evidences of seismic activity are interpreted as the result of different weakening versus induration processes which also result in localization versus delocalization of deformation in the fault zone from a methodological point of view the technique used here is advantageous over direct measurements of exposed fault surfaces in that it preserves in cross section all of the structures which contribute to fault roughness and removes any subjectivity introduced by the need to distinguish roughness of original slip surfaces from roughness induced by secondary weathering processes moreover offsets can be measured by means of suitable markers and fault rocks are preserved hence their thickness composition and structural features can be characterised providing an integrated dataset which sheds new light on mechanisms of roughness evolution with slip and concomitant fault rock production

numerical modelling of slope damage in large slowly moving rockslides insights from the downie slide british columbia canada abstract the deformation of rock slopes is associated with the formation and accumulation of internal and external features such as tension cracks rock mass bulging and dilation rockfall etc that can be comprehensively referred to as slope damage in this paper we use a 3d distinct element numerical modelling approach to investigate the role of shear zone morphology and groundwater pressure on the displacement and slope damage accumulation at the downie slide a large extremely slowly moving rockslide in british columbia canada first we briefly review the external slope damage features that can be observed in an airborne laser scanner als dataset allowing four slope damage domains upper central northern and southern domain to be interpreted within the slide area based on the orientation and type of features using the same als dataset we construct a 3d model of the present day slope explicitly including the two shear zones along which displacements occur in order to investigate their role in the later stage of the landslide evolution we assign a strain softening constitutive model to the slide body in order to account for the decrease in material properties due to damage accumulation virtual inclinometers are also implemented in the model allowing for the comparison of simulated and observed displacement direction along the shear zones the progressive deformation and failure of the slope is then simulated both assuming dry and wet conditions in order to examine the role of pore water pressure and the morphology of the upper and lower shear zones on the magnitude orientation and distribution of displacements for each numerical model the simulated slope damage features are recorded by analyzing the zone volumetric strain and failure state and compared with the type and orientation of features observed in each of the interpreted slope damage domains thus allowing the numerical results to be better constrained and validated it is clearly demonstrated that the orientation and distribution of slope damage and displacements observed in both the surface als and the subsurface borehole inclinometer data can be well reproduced in the 3d numerical models numerical modelling results show that the principal factor controlling the spatial distribution of slope damage at the downie slide is the morphology of the lower shear zone whereas a negligible role is played by the upper shear zone morphology we also observe that models incorporating a groundwater table display larger displacements without significant effects on the orientation and distribution of simulated slope damage this paper demonstrates that an analysis of slope damage is very important for understanding the mechanisms underlying the behavior of large landslides and should be a fundamental step in the comprehensive characterization of any major slope failure

numerical analysis of initiation and progressive failure in natural rock slopes the 1991 randa rockslide the 1991 randa rockslide in the swiss alps involved several complex mechanisms relating to geological mechanical and hydrological processes for which no clear trigger can be asserted this paper investigates the concept of progressive failure and the numerical modelling of rock mass strength degradation in natural rock slopes using the randa rockslide as a working example results from continuum i e finite element modelling are presented to illustrate a hypothesis suggesting that initiation of a progressive rock mass degradation process ultimately leading to failure began following deglaciation of the valley below discontinuum distinct element modelling is then applied to investigate the underlying mechanisms contributing to the episodic nature of the rockslide finally the use of a hybrid method that combines both continuum and discontinuum techniques to model fracture propagation are discussed in the context of modelling progressive slide surface development linking initiation and degradation to eventual catastrophic failure

middle visean mississippian coral biostrome in central guizhou southwestern china and its palaeoclimatological implications abstract a middle visean mississippian coral biostrome is reported for the first time from the shangsi formation in yashui area central guizhou province southwestern china palaeogeographically located in eastern palaeotethys the biostrome which is about 500 m across and 2 5 3 9 m thick is laterally variable and composed of rugose and tabulate corals with low taxonomic diversity comprising 4 rugose and 1 tabulate coral species belonging to 5 genera three growth stages of the biostrome are distinguished based on different compositions of coral taxa average coral contents of the biostrome increase from 38 7 to 72 0 upward and the main builders are siphonodendron pentalaxoidea syringopora sp and kueichouphyllum sinense associated fossils include abundant brachiopods crinoids and common foraminifers together with rare calcareous algae bryozoans gastropods and ostracods relative sea level changes are interpreted to have controlled growth and demise of the biostrome which grew continuously during sea level rise and decreasing water energy as evident from the gradually increasing of micrite content and in situ coral colonies however the biostrome declined and died as the sea level fell and hydrodynamic energy strengthened indicated by an increase of bioclasts and sparry calcite cement indicating lack of micritic matrix due to higher energy overlying the biostrome this coral biostrome has similar biotic composition to middle to late visean coral biostromes in europe and north africa western palaeotethys the approximately coeval occurrence of coral biostromes in both eastern and western palaeotethys suggests that a relatively global warm episode existed during the visean stage

glaciation aridification and carbon sequestration in the permo carboniferous the isotopic record from low latitudes to evaluate the isotopic record of climate change and carbon sequestration in the late paleozoic we have compiled new and published oxygen and carbon isotopic measurements of more than 2000 brachiopod shells from carboniferous through middle permian 359 260 ma strata we focus on the isotopic records from the u s midcontinent and the russian platform because these two regions provide well preserved marine fossils spanning a broad time interval both regions show a 18o increase at the mid carboniferous boundary ca 318 ma that roughly correlates with geologic evidence for an expansion of gondwanan glaciers only the russian platform record shows a 18o maximum during the glacial maximum in the asselian in contrast to a previous study korte c jasper t kozur h w and veizer j 2005 18o and 13c of permian brachiopods a record of seawater evolution and continental glaciation palaeogeogr palaeoclimatol palaeoecol 224 333 351 our data show no oxygen isotope evidence for glacial retreat in the early permian but instead show increasing 18o values related to aridification dissimilarity in the 18o trends for the epicontinental seas of north american and the russian platform suggests that at least one region experienced periodic restriction that altered regional salinities and seawater 18o values these results highlight the need for complementary proxies to identify restricted circulation in epicontinental seas carbon isotopic compositions of carbonates exhibit substantial regional variation with low values in western north america intermediate values in the midcontinent and high values in the sverdrup basin russian platform and northern spain nevertheless both u s midcontinent and russian platform records show a late serpukhovian minimum a sharp increase across the mid carboniferous boundary and a minimum centered on the kasimovian the correlative increase in brachiopod 13c and 18o values at the mid carboniferous boundary is our best isotopic evidence for a link between the carbon burial and glaciation in the permo carboniferous

isotopic records of brachiopod shells from the russian platform evidence for the onset of mid carboniferous glaciation we performed isotopic analyses of carboniferous brachiopod shells from the russian platform to examine global and regional environmental change along the western and eastern margins of laurussia during the formation of pangea and specifically to examine the isotopic evidence for the onset of mid carboniferous glaciation shell preservation was evaluated from shell microstructure cathodoluminescence trace element content and isotopic comparison with matrix material most interior nonluminescent nl prismatic shell appears to be chemically well preserved as indicated by low to undetectable si al fe and mn contents with minor exception nl shell 13c and 18o values are higher than those of corresponding cements and matrix the 13c record for the russian platform clearly shows a 3 increase from 2 4 0 7 to 5 5 0 6 in the serpukhovian or early bashkirian this shift was first reported by popp et al popp b n anderson t f sandberg p a 1986 brachiopods as indicators of original isotopic compositions in some paleozoic limestones geol soc am bull 97 1262 1269 but had not been documented for a single region widespread occurrence of high 13c values in the late carboniferous support the interpretation of popp et al with regard to this shift as a record of increased burial of organic carbon north american sections show a mid carboniferous 13c shift of only 1 5 we hypothesize that the reduced 13c shift reflects enhanced upwelling on the epicontinental seas of north america after the closing of the seaway between laurussia and gondwana the 18o record for the russian platform shows a 1 8 increase in the mid carboniferous correlative with increased occurrence of glacial sediments and a drop in sea level as a first approximation ice volume calculations suggest that 0 7 of the mid carboniferous 18o shift is due to changes in seawater 18o and 1 1 is due to 5 c cooling concurrent positive 13c and 18o shifts provide evidence for a relationship between mid carboniferous glaciation and burial of organic carbon presumably through changes in atmospheric co2 levels

astronomical cycles in the serpukhovian moscovian carboniferous marine sequence south china and their implications for geochronology and icehouse dynamics abstract the late paleozoic ice age ca 335 260 ma lpia has long been considered as an analogy for the cenozoic ice age since the oligocene the impact of astronomical forcing on the lpia glaciation has been hampered due to the low resolution multi million year scale time framework in the present study high resolution cyclostratigraphy based on magnetic susceptibility ms covering the serpukhovian to late moscovian icehouse climate has been investigated in the luokun section of south china power spectral analysis of the ms series reveals 3 44 4 m 0 8 1 07 m 0 3 0 32 m and 0 17 0 19 m thick sedimentary cycles based on the available biostratigraphic constraints calibrating the 3 44 4 m cycles to the 405 kyr eccentricity cycles indicates short eccentricity 136 and 100 kyr short obliquity 34 kyr and precession 19 and 15 9 kyr orbital bands in addition to long eccentricity 405 kyr band we assigned the basal serpukhovian and moscovian stages in luokun with the numerical ages from geological time scale 2012 to construct two floating time scales ranging from 331 55 0 5 ma to 323 2 0 5 ma and from 315 34 0 35 ma to 310 17 0 35 ma respectively the modulation of main obliquity s4 s3 term has a main periodicity of 1200 kyr the modulation of 100 kyr eccentricity g4 g3 term shows a main periodicity of 2400 kyr with subordinate periodicities of 1620 and 1200 kyr for the serpukhovian and a main periodicity of 1600 kyr for the moscovian they may provide the geological evidence for a chaotic resonance associated with interactions between the orbits of mars and the earth in the carboniferous a duration of 7 68 0 15 myr was estimated for the serpukhovian stage eight higher accumulation rate events due to glacioeustatic drawdown were temporally constrained and show close correspondence to far field and near field reconstructions of the lpia glaciation glacioeustasy was paced with 405 kyr long eccentricity and 1 2 myr obliquity amplitude cycles during the serpukhovian and moscovian stages likely indicating the nature in the warmer icehouse world similar to that of the oligocene to pliocene

late palaeozoic environmental changes an introduction the idea of this volume arose from our proposal to the palaeoclimatic session held at the european geosciences union general assembly 2011 conference in vienna austria although the original scope was broader the included contributions focus on palaeoenvironmental changes during the late palaeozoic late palaeozoic history is especially important in that it records an increase of tectonics diastrophism frequent sea level fluctuations and climatic changes all finally leading to the most geocratic time of earth s history with the formation of the supercontinent pangaea this volume includes a number of articles that discuss the fossil record around the late palaeozoic ice age and its decline during the carboniferous with its unusual plant proliferation soon after when the hottest and driest period in earth s history in the permian caused the development of huge sand seas on the land finally a biotic event the largest mass extinction in earth history at the permian triassic transition ends the palaeozoic world this volume addresses two key issues the palaeoclimate and depositional cycles both of which have a strong impact on the record of palaeoenvironmental changes and the understanding of environmental perturbations the vigorous current debate on the future climate of the globe inevitably increases our interest in past climates from a geological perspective climatic perturbations occurred many times before humans were on the planet climate varies on several timescales depends on many high order factors including tectonic uplift and the orbital wandering of the earth and as a result it changes through time consequently palaeoclimatic reconstructions are growing in their importance as they enable us to use the past as a key to the future the earth s system experiences various cycles of very different origin scale frequency amplitude phase and basic level from a geological perspective the cyclicity appears unidirectional like brownian motion however in the past the complex interaction of these cycles has led to catastrophic changes in earth s systems such as those during the late palaeozoic when palaeoclimatic and geotectonic cycles coincided these cycles are also influencing our lives and will do so in our future so their impact needs to be understood the geological archives record both the climatic and cyclic phenomena on local to regional scales including in the late palaeozoic as documented in this volume understanding these records will improve our predictions about climate phenomena in the future they also show that the present climatic perturbations are insignificant from a geological point of view changes in the late palaeozoic earth system are illustrated in this volume by case studies of fossil records from north and south america east and south asia south africa and australia and as regional reviews section one the methods include palaeoenvironmental analysis including palaeobiological sedimentological stratigraphic sequence stratigraphy palaeomagnetic and geochemical methods they describe various environmental settings from palaeodeserts through marine associated giant salt pans to shallow to deep marine records the articles report new data from less known study areas provide up to date data ordering and expand our knowledge of the evolution of marine and terrestrial environments climatic changes and biotic events in late palaeozoic time this special publication is divided into five chapters the first comprising articles focused on the broad descriptive character of late carboniferous to early triassic palaeoclimatic changes and stratigraphy with the latest part of this period in europe i e zechstein subsequent articles include more detailed studies of the geological periods grouped into the latest devonian to early carboniferous section two late carboniferous to early permian section three middle to late permian section four and finally the permian triassic transition section five a brief synopsis of individual papers is given below wopfner 2012 reviews westphalian early triassic palaeoclimatic conditions between samfrau comprising the southern margins of south america and south africa extending via antarctica

coral reefs and growth dynamics of a low angle carboniferous platform records from tianlin southern china abstract metazoan reef building receded globally during the carboniferous after the late devonian extinction events shallow water bioconstructions were generally small and scarce and corals played a minor role in their construction however in southern china one large 50 m high and three small 6 16 m high coral reefs dating from the late visean serpukhovian have recently been discovered in two localities in guangxi to understand the occurrence of these coral reefs and to constrain the factors that controlled their growth three sections around langping guangxi were measured and selected samples were analysed using petrography biostratigraphy and chemostratigraphy the depositional environment of these exceptional mississippian reefs was interpreted as a low angle platform 1 2 5 recording oligotrophic conditions and normal salinity the three small reefs have grown around the fair weather wave base whereas the large coral reef has grown in a deeper environment between the fair weather and storm wave base during carboniferous the global temporal reef distribution can be partly ascribed to paleoclimate changes however in southern china the growth of extended mississippian coral reefs is restricted to a short time window the late visean serpukhovian which coincides with high amplitude and high frequency sea level fluctuations most likely related to glacial pulses recent studies revealed that several rugose coral species survived the mid carboniferous glaciation event thanks to the persistence of warm water ocean currents maintaining tropical conditions on the platform due to the scarcity of extended coral reefs elsewhere it cannot be excluded that tianlin provided an ecological refuge for corals related to oceanic currents another potential favorable factor could be the mid ramp depositional setting the deep water platform areas could potentially provide more stable conditions less affected by global stress events however the deep reef refugia hypothesis remains debatable as only very few studies have explored its validity at the community level even if the causes of the occurrence of an extended coral reef in southern china cannot be fully constrained the existence of this large coral framework in the late visean serpukhovian provides additional evidence that coral communities did build reefs after the late devonian extinction events

the use of syntectonic fibres to determine strain estimates and deformation paths an appraisal abstract fibrous pressure shadows developed adjacent to rigid brittle inclusions are familiar features in many tectonites belief that these structures reflect the deformation path as once adjacent grains move apart has led to the derivation of a variety of techniques to determine both incremental and finite strain estimates these methods which can be divided into rigid fibre models e g durney and ramsay and deformable fibre models e g ellis display potentially serious problems when applied to field examples recent studies of microstructures within veins and pressure shadows support the concept that syntectonic fibre complexes can reflect deformation paths and are therefore useful markers of incremental and finite strain the problems mentioned therefore stem directly from the application of the techniques worked examples using these techniques give a variety of strain values dependent upon the extent to which a particular technique allows for volume change or fibre deformation this is useful locally however if the results are to be meaningful on a regional scale then it is imperative that the same technique be applied in the analysis of all fibres regardless of the local deformation path in such studies the merits of a particular technique in determining a correct strain value come second to allowing the spatial distribution of strain to be determined semi quantitatively and thus allowing comparison of similarly derived results with one another

rapid onset of late paleozoic glaciation on gondwana evidence from upper mississippian strata of the midcontinent united states direct evidence of the late paleozoic glaciation of gondwana from glacial deposits suggests that geographically extensive continental glaciation began some time in the namurian late mississippian however the timing and characteristics of the onset of glaciation are poorly understood because of a lack of reliable paleontological control and reworking of initial glacial deposits by subsequent glacial advances indirect evidence of glaciation preserved in unconformity bounded low latitude ramp sequences in the illinois basin united states suggests that geographically extensive continental glaciation of gondwana actually began in the late visean an abrupt change from carbonate dominated sequences bounded by disconformities with little evidence of erosion to mixed carbonate siliciclastic sequences bounded by unconformities with deep incised valleys was likely produced by a three fold increase in the magnitude of eustatic sea level fluctuations the increase in the magnitude of sea level fluctuations was likely driven by an equally abrupt increase in ice volume and marks the onset of the geographically extensive late paleozoic glaciation of gondwana a possible explanation for the rapid onset of glaciation is the closing of the equatorial seaway between laurussia and gondwana closing of this seaway would have led to an abrupt change in oceanic and atmospheric circulation patterns that could have initiated major continental glaciation in the southern hemisphere

climatic and hydrologic controls on upper paleozoic bauxite deposits in south china abstract the late paleozoic era was an interval of major tectonic and climatic changes including formation of the supercontinent pangea and the 60 myr long late paleozoic ice age lpia although bauxite formation declined globally from the carboniferous to the permian in conjunction with global cooling it was an interval of widespread bauxite formation in china in south china 1 the jiujialu formation bauxite deposits in central and northern guizhou zunyi area are of early middle visean age 2 the dazhuyaun formation bauxite deposits in northern guizhou wuchuan zheng an daozheng area to southern chongqing nanchuan area and southeastern guizhou fuquan kaili area are of late pennsylvanian early permian age and 3 the heshan formation bauxite deposits in western guangxi to yunnan are of middle late permian age in north china the benxi formation bauxite deposits are of late mississippian middle pennsylvanian age the contrasting trends in bauxite metallogenesis between china and the rest of the world imply different climatic patterns in the eastern tethys high annual humidity with seasonal dryness and pangea aridification this hypothesis is further supported by differences in the chemical index of alteration or cia 80 in the eastern tethys vs 50 in western pangea and in paleotemperatures mean annual temperature or mat 20 c in the eastern tethys vs 4 c in western pangea determined from permo carboniferous siliciclastic deposits permo carboniferous bauxite deposits in south china formed in coastal plain and coastal karstic depression environments in which the position of the groundwater table was related to sea level changes during the late paleozoic high frequency eustatic fluctuations caused by waxing and waning of gondwana icesheets controlled sedimentation in these coastal depositional systems leading to cyclic accumulation of coal and bauxite deposits and cycles of vadose and phreatic type bauxite formation the results of the present study show that during interglacial stages lateritization resulted from high pco2 high sea level and groundwater table elevations low precipitation and limited vegetation cover whereas during glacial stages bauxitization of these ferralitic weathering products was promoted by low pco2 low sea level and groundwater table elevations high precipitation and more extensive vegetation cover thus a unique combination of geographic climatic and eustatic factors accounted for widespread formation of bauxite in south china during the lpia

the prehistoric vajont rockslide an updated geological model abstract this study presents the detailed reconstruction of the entire structure of the prehistoric vajont rockslide about 270 300 million m 3 of rocks and debris for the first time describing the complex geometry and the characteristic superimposition of distinct rigid blocks on a very thick shear zone the prehistoric vajont rockslide was characterized by an enormous en masse motion of a rigid overlying rock mass 100 130 m thick that moved downslope sliding onto a very thick shear zone 40 50 m thick on average made up of a chaotic assemblage of blocks limestone angular gravel and high plasticity clays montmorillonitic clays coarse loose sediments still exposed on the 9 october 1963 detachment surface are always associated with large blocks made of strongly fractured rock masses fonzaso formation middle upper jurassic preserving the stratification the blocks of stratified and folded limestone sequences appear to be sheared off from the underlying bedrock and can be considered as displaced rock masses planed off by the motion of the overlying rigid rock mass rock mass shavings the prehistoric vajont rockslide was characterized by a multistage failure with a marked retrogressive evolution the first rupture pian del toc block rapidly destabilized the upper slope mobilizing a second rock mass block pian della pozza block that in turn determined the multiple rupture of the revealed shear zone material massalezza lobe even if the exact timing of the different phases is not known the entire multistaged failure process was very rapid at the end of the multistage retrogressive failure the slope morphology of the northern toe of mt toc was drastically changed and the large failed rock mass settled into the preexisting vajont valley assuming the unusual chair like geometry the vajont rockslide represents a very significant example on how a complex geological situation if not adequately analyzed and reconstructed can lead to dangerous misinterpretations or even to erroneous engineering geological and geotechnical models accurate fieldwork and modern technologies can be fundamental in solving such a very intriguing geological puzzle

development of crystal morphology during unitaxial growth in a progressively widening vein ii numerical simulations of the evolution of antitaxial fibrous veins the development of fibrous morphology and capability of fibres for tracking the opening trajectory were investigated using numerical simulations of a natural antitaxial fibrous vein starting from a non unique best case variation of fracture opening velocity grain size wall roughness growth anisotropy and crystal growth velocity shows that these parameters differ in importance for crystal morphology and tracking capability fibrous veins can be simulated using crack seal opening of the fracture grain boundaries track the opening trajectory if the wall roughness is high opening increments are small and crystals touch the wall before the next crack increment starts

global events of the late paleozoic early devonian to middle permian a review abstract the late paleozoic early devonian to middle permian was an interval of profound changes in earth surface systems reflected in dynamic interplay among the biosphere hydrosphere atmosphere and geosphere major events transpired including the colonization of landmasses by vascular plants the assembly of the supercontinent pangea two first order mass extinctions the frasnian famennian and devonian carboniferous boundary events and the most severe icehouse climate mode of the phanerozoic the late paleozoic ice age lpia the goals of the present review are 1 to summarize major global developments in climate oceanography and paleobiology during the late paleozoic 2 to examine the roles of land plant evolution global tectonics and large igneous province magmatism in driving these developments and 3 to serve as an introduction to the 23 contributions to this special issue of palaeogeography palaeoclimatology palaeoecology indicating how they advance our knowledge of various scientific issues related to these developments

forecasting giant catastrophic slope collapse lessons from vajont northern italy rapid giant landslides or sturzstroms are among the most powerful natural hazards on earth they have minimum volumes of similar to10 6 10 7 m 3 and normally preceded by prolonged intervals of accelerating creep are produced by catastrophic and deep seated slope collapse loads similar to1 10 mpa conventional analyses attribute rapid collapse to unusual mechanisms such as the vaporization of ground water during sliding here catastrophic collapse is related to self accelerating rock fracture common in crustal rocks at loads similar to1 10 mpa and readily catalysed by circulating fluids fracturing produces an abrupt drop in resisting stress measured stress drops in crustal rock account for minimum sturzstrom volumes and rapid collapse accelerations fracturing also provides a physical basis for quantitatively forecasting catastrophic slope failure c 2003 elsevier science b v all rights reserved

the possible role of brittle rock fracture in the 1963 vajont slide italy abstract we use a state of the art numerical simulation approach to investigate the vajont slope failure a large catastrophic landslide that resulted in the loss of 1910 lives this study represents the first three dimensional 3d brittle fracture simulation of the vajont slide that includes the effect of groundwater on the failure process a realistic representation of the vajont slope geometry failure surface and discontinuities in a 3d lattice spring code allowed us to study the kinematics of the landslide using a lattice spring block model approach the relations among the number of blocks slope damage and stability are investigated the influence of an elevated groundwater table on displacements and cracking within the model is evaluated the results show a good agreement with the reported microseismic events prior to the failure two new techniques damage intensity d 32 and the ellipsoid of damage are introduced and used to quantify brittle damage within the numerical simulations

carboniferous glaciation in gondwana evidence for grounded marine ice and continental glaciation in southwestern argentina abstract upper paleozoic sedimentary rocks in western argentina accumulated in retro arc foreland basins in the gondwana continental margin a glacial component in these rocks was recognized early in this century but reconstructions of the nature of the glaciation differ markedly the dominant proposal sustains that glaciation in this region was of alpine type with glaciers descending from mountain ranges both inland and along the edge of the continent and that the numerous intercalated diamictites were mostly deposited as subaquatic debris flows only indirectly connected with the presence of glacier ice a stratigraphic and sedimentologic study of middle carboniferous glacigenic deposits of the tepuel group in central western patagonia southwestern argentina shows that two major diamictite facies are present a massive diamictite the more abundant forms regionally extensive and thick

close range terrestrial digital photogrammetry and terrestrial laser scanning for discontinuity characterization on rock cuts this paper reviews the application of close range terrestrial digital photogrammetry and terrestrial laser scanning for discontinuity characterization on rock cuts terrestrial remote sensing techniques are being increasingly used as a complement to traditional scanline and window mapping methods they provide more comprehensive information on rock cuts allow surveying of inaccessible outcrops and increase user safety selected case studies are used to estimate the accuracy of several 3d model registration approaches and the most time effort and cost effective methods are highlighted it is shown that simple registration networks are able to provide adequate measurement of discontinuity orientation for engineering purposes the case studies presented also illustrate the effects of sampling bias and limitations related to discontinuity characterization using remote sensing techniques vertical orientation bias and occlusion can be of particular concern when persistent discontinuities dip at the same angle as the camera scanner line of sight major advantages of the techniques are presented illustrating how terrestrial remote sensing techniques provide rapid spatial measurements of discontinuity location orientation and curvature and are well suited to the quantification of persistence magnitudes greater than 3 m

cyclic fluid flow through a regionally extensive fracture network within the kodiak accretionary prism two types of periodic textures observed in veins from the kodiak accretionary prism attest to cyclic fluid flow through a regionally extensive fracture network buried at 8 12 km depth 1 crack seal microstructures with bands of mica inclusions and 2 collapse microstructures with jagged bands of residue embedded within euhedral crystals of quartz the difference in texture reflects the closure of cracks crack seal microstructures record the complete chemical sealing of the crack after each fracture event whereas the collapse features record longer fluid filled periods followed by more rapid draining of fractures collapse features consist of pressure solution selvages trapped within veins and in the wall rock adjacent to euhedral growth terminations the high concentrations of immobile elements in these selvages indicate that these fractures closed by collapse and penetration of quartz crystals into wall rock analysis of chemical composition on either side of four large euhedral growth veins and whole rock analysis of slates across the kodiak formation reveal local depletion of silica adjacent to veins but no evidence for long distance silica transport within the system both crack seal and collapse textures are observed in a regionally extensive vein system that displays a regular geometry with thin closely spaced 0 5 3 cm near vertical crack seal veins that connect vertically and laterally with thicker euhedral growth veins arranged in widely spaced 500 mm southeast dipping en echelon sets the mesoscopic distribution and textural variability of the vein network suggests that the development of the vein system involved early nucleation and growth of vertical hydrofractures as the fracture density increased arrays of fractures locally provided zones of weakness and southeast dipping brittle ductile shear zones nucleated these en echelon cracks remained open and provided small reservoirs of fluid textures show that en echelon fractures remain open but periodically grow by upward and downward propagation crack tips are then sealed with locally derived silica and fluid drains back into en echelon fracture arrays this local fluid movement is punctuated by less frequent events where the system links up over a greater distance fractured reservoirs become interconnected and the fluid within reservoirs is drained upward or laterally periodic inflation and deflation of en echelon arrays may reflect periodic slip on crosscutting faults and rupture of the seals that separate reservoirs

constraints on pennsylvanian glacioeustatic sea level changes using oxygen isotopes of conodont apatite conodonts from u s midcontinent cyclothems were studied for oxygen isotopes in order to constrain pennsylvanian glacioeustatic sea level fluctuations pennsylvanian deposits of the midcontinent united states are composed of cyclic alternations of thin transgressive limestones offshore gray to black phosphatic shales and thick regressive limestones a sequence that is underlain and overlain by nearshore to terrestrial shales with paleosols and coal beds glacioeustatic sea level fluctuations are considered the primary cause for the formation of these cyclothems oxygen isotope analyses of conodont apatite from the black 20 1 0 5 vienna standard mean ocean water vsmow and gray shale units 20 5 0 5 vsmow show lowest average 18 o values whereas conodont elements from the regressive 21 0 0 3 vsmow and transgressive limestone units 21 1 0 6 vsmow are enriched in 18 o the maximum change in 18 o of conodonts from the black shale and carbonate units from individual cyclothems is 1 7 the 1 7 c difference in 18 o compares relatively well to pleistocene interglacial glacial changes in 18 o of equatorial surface dwelling foraminifers and suggests that pennsylvanian glacioeustatic sea level changes may have been of comparable amplitude however since the pennsylvanian glacial maxima are represented by terrestrial sediments and are not documented in the conodont oxygen isotope record pennsylvanian glacioeustatic sea level changes were probably larger than the 120 m fluctuations recorded for the pleistocene glaciations

quantitative three dimensional description of a rough surface and parameter evolution with shearing note roches reference lmr article 2002 005view record in web of science record created on 2006 11 09 modified on 2016 08 08

non linear growth kinematics of opening mode fractures abstract fracture aperture is commonly assumed to be a linear function of fracture length stress and elastic material properties under constant stress fracture opening displacement may change without concurrent length or height growth if the material effectively weakens after initial linear elastic fracture growth by changes in elastic properties or by non elastic deformation processes to investigate the kinematics of fracture opening and its dependence on length and height growth we reconstructed the opening history of three opening mode fractures that are bridged by crack seal quartz cement similar crack seal cement bridges had been interpreted to form by repeated incremental fracture opening and subsequent precipitation of quartz cement using scanning electron microscope cathodoluminescence imaging we determined the thickness and number of crack seal cement layers as a function of position along fracture length and height observed trends in crack seal cement layer thickness and number of fracture opening increments are consistent with non linear fracture growth kinematics consisting of an initial stage of fast fracture propagation relative to aperture growth followed by a stage of slow propagation and pronounced aperture growth consistent with earlier fluid inclusion observations indicating fracture opening and propagation occurring over 40 50 m y we interpret the second stage of pronounced aperture growth and slow propagation to result from fracture opening strain accommodated by solution precipitation creep and concurrent slow possibly subcritical fracture propagation

surface texture analysis of a high resolution dtm interpreting an alpine basin abstract this study focuses on a geomorphometric analysis of a small headwater basin of the dolomites eastern italian alps the analysis of the fine scale surface morphology was performed on a high resolution digital elevation model cell size 2 m derived from an airborne lidar survey the topography was synthesized by a set of spatial statistical indexes representing a signature of the local surface morphology and the relationships between the geomorphometric indexes and morphological features were evaluated the studied basin was then segmented by means of a fuzzy k means classification algorithm into different spatial subdomains characterized by specific local geomorphic signatures this method allows us to objectively choose the optimal combination of the number of classes and degree of fuzziness characterizing the studied basin accordingly the analysis can be adopted to the characteristics of the studied area improving the interpretation of surface morphology and offering a valuable tool for comparative analysis between different geomorphological contexts the results of the classification were compared with the actual surface morphology based on high resolution orthophotos aerial photos and field surveys

δ18o and δ13c of permian brachiopods a record of seawater evolution and continental glaciation abstract two hundred sixty four 18 o and 13 c values of permian articulate brachiopod shells were analyzed and 81 of these values were characterized as well preserved and biostratigraphically well defined these were then utilized for construction of baseline oxygen and carbon isotope curves for the permian interval in addition 21 13 c whole rock values are reported for the wordian and capitanian the early permian asselian to artinskian times are characterized by 2 5 decrease in oxygen isotope values from 0 7 to 3 3 v pdb this is attributed to a 4 7 c increase in temperature in the southern urals concomitant with the retreat of the permo carboniferous ice sheets and return of the 18 o depleted melt water into the oceans the late permian samples from iran jolfa at kuh e ali bashi and china meishan yield 18 o values and presumably temperatures similar to those that followed the termination of the large scale glaciation in the lower permian in between the upper kungurian to capitanian samples from the delaware basin guadalupe mountains are enriched in 18 o at 1 5 to 3 we have no definitive explanation for these data but tentatively suggest that the anomaly can potentially be a result of evaporative enrichment of seawater in 18 o due to intracratonic arid setting of the basin the 18 o enriched nature of the zechstein samples 1 2 to 2 5 on the other hand is in all probability a reflection of the high evaporation rates in the zechstein sea the permian interval is characterized by a relatively constant 13 c at about 4 the exceptions are again the brachiopods from the delaware basin guadalupe mountains which show 1 6 increase in the guadalupian to values of up to 5 9 in the wordian a tentative explanation as in the case of oxygen is based on the proposition that the semi enclosed delaware basin was likely stratified with sequestration of the 13 c depleted carbon to the deeper water layers and a complementary 13 c enrichment in the upper oxygenated layer the coeval open ocean water dic may have been similar to that of the remainder of the permian interval at 4 as indicated by whole rock carbonate samples from oman sicily and iran in the latest permian the trend mimics the well known 13 c drop at the permian triassic boundary

ecological ranking of phanerozoic biodiversity crises the serpukhovian early carboniferous crisis had a greater ecological impact than the end ordovician we propose a new ecological ranking of the major phanerozoic biodiversity crises in which the serpukhovian biodiversity crisis is ranked fifth in ecological impact lesser than the late devonian but greater than the end ordovician and the end ordovician mass extinction is ranked sixth it is interesting that both the end ordovician mass extinction and the serpukhovian biodiversity crisis were triggered by glaciations other than that common trigger the two events were very different glaciation in the ordovician triggered an enormous jump in the extinction rate of marine organisms and was taxonomically very severe yet the ecological impact of those extinctions was minimal glaciation in the serpukhovian triggered a precipitous drop in the speciation rate but only moderate diversity losses yet the ecological impact of those diversity losses and ecosystem restructuring was an ecological level of magnitude larger than that seen in the end ordovician mass extinction

antitaxial crack seal vein microstructures and their relationship to displacement paths abstract the microstructures developed in an example of a syntectonic crack seal vein indicate that antitaxial fibres do not necessarily track the incremental opening history during crack seal vein growth this observation serves as a caution against the uncritical use of fibrous microstructures to make inferences about displacement histories during fibre formation it is demonstrated that crack seal processes can lead to the development of both irregular and laminated vein microstructures as well as fibrous microstructures the types of microstructures which develop in crack seal veins and the extent to which they reflect the opening paths of veins depend on a range of factors the most important of these include the nucleation and growth kinetics of phases precipitated from fluids in opening fractures and the location of sites of material accretion during successive crack seal increments

neotectonics of the vajont dam site abstract the disastrous vajont landslide ne italy of 9 october 1963 is generally thought to have occurred on an existing failure surface reassessment of the morphological and structural evidence suggests that movement was on a normal fault plane which had juxtaposed cretaceous limestone and highly fractured rock debris thus rendering the dam site unusually susceptible to massive sliding the proposed fault is consistent in strike with the regional lineament pattern although movement was triggered by the combined effects of heavy rainfall and changes in reservoir level there is circumstantial evidence that seismicity played a contributory part in mobilising the slide by increasing pore pressure at the base of the slide as well as by any associated shaking

sedimentology and palaeoecology of lonestone bearing mixed clastic rocks and cold water carbonates of the lower permian basal beds at fossil cliffs maria island tasmania australia insight into the initial decline of the late palaeozoic ice age

permian 87sr 86sr chemostratigraphy from carbonate sequences in south china abstract a continuous strontium isotope profile with high resolution sampling is desirable to calibrate multiple global events realize temporal correlation among different continents and understand tectonic history of the permian period in this paper we analyzed 90 micritic limestone samples from south china and 7 samples from iran with the aim to gain new 87sr 86sr data and obtain a curve of sr isotopes for the permian the concentrations of mg fe mn and sr are used to discriminate possible diagenesis of the samples a comparison of those 87sr 86sr values between south china and southern urals confirms that sr isotope proxy has the potential to be used for time calibration and correlation in regions where biostratigraphic or radiometric markers are not available the 87sr 86sr curve obtained in this study shows a trend comparable with the locally weighted scatterplot smoothing lowess regression curve from the previous studies a continuous decline trend from the latest carboniferous to late guadalupian was shown and the lowest 87sr 86sr values in the late capitanian was constrained within the interval from the conodont jinogondolella shannoni j altudaensis to j xuanhanensis zones it is followed by an increasing trend to more radiogenic values in the lopingian with a minor fluctuation in the early wuchiapingian we consider that mid ocean ridge spreading and increasing continental weathering during the transition from convergence to the breakup of pangea as the dominant factors driving the changes of the seawater sr isotope ratios

rheology of the plate interface dissolution precipitation creep in high pressure metamorphic rocks abstract subduction zone models invoke deformation to be concentrated along the plate interface in a region of particularly low temperature geophysical observations do not provide constraints on temperature stress and deformation patterns with desired resolution in contrast the record of high pressure metamorphic rocks exhumed from subduction zones provides details on p t history deformation mechanisms and stress state albeit not readily correlated with the former dynamic situation on larger scale here we review available information on dissolution precipitation creep dpc in high pressure metamorphic rocks which if representative for subduction zones in general can pose constraints on conditions rheology and flow patterns along the plate interface the key observations and conclusions are that 1 deformation is typically highly inhomogeneous and localized into shear zones 2 stresses are generally too low to drive crystal plastic deformation 3 microfabrics suggest dissolution precipitation creep to be the predominant deformation mechanism 4 an aqueous fluid at quasi lithostatic pressure is available throughout allowing for tensile fracturing and crack healing or sealing 5 low stress combined with high strain rates required for localized deformation at typical subduction rates implies low viscosity and 6 contribution of shear heating to the thermal budget of subduction zones should be moderate the dominant deformation mechanism dpc is reviewed in some detail including experimental and theoretical approaches various examples of dpc in high pressure metamorphic rocks are illustrated emphasizing the role of interphase boundaries as sites of dissolution rheology governed by dpc is proposed to control interplate coupling and development of a subduction channel with return flow being a likely candidate for rapid exhumation of high pressure metamorphic rocks

depressed rates of origination and extinction during the late paleozoic ice age a new state for the global marine ecosystem rates of origination and extinction for marine animal genera dropped to low levels in latest mississippian time immediately after massive glaciers formed in the southern hemisphere and a second order mass extinction occurred evolutionary turnover and diversity remained low for 50 m y shifting markedly upward precisely when extensive glaciation ended in early permian time all diverse taxa with good fossil records experienced low rates of origination and extinction during this major ice age such sluggish rates would be predicted for faunas of shallow seas on or adjacent to a heavily glaciated supercontinent such as pangea where cool and highly seasonal thermal regimes should dictate that species have broad ecological niches widespread geographic distributions and large and relatively stable populations

crystallization pressure versus crack seal as the mechanism for banded veins banded fibrous veins are often pointed to as evidence for episodic crack opening driven by oscillations in fluid pressure or bulk strain advances in understanding the geochemistry of precipitation data on veins and experiments suggest that pressure due to growing crystals may be an alternate explanation for many observations on these types of veins we propose that some veins originate at sites of precipitation and then propagate due to the pressure exerted by the crystal growth as materials precipitate the vein walls are pushed apart the resulting veins have shapes typical for mode i cracks except that mechanically crystallization pressure replaces the role of internal fluid pressure in their propagation a nonzero remote differential stress serves to align veins mechanical and geochemical considerations suggest that this process will be most important in fine grained rocks such as greenschist grade pelites where diffusion from sites of dissolution rather than advection is the dominant mass transport process veins may owe their orientation to tectonism but their initiation and growth are due to processes that supersaturate the pore fluid veins formed by this mechanism involve cracking to the extent that precipitation forces an original flaw to extend during precipitation cyclic quartz mica bands may indicate geochemical self organization at the vein wall driven by pressure solution enhanced supersaturation in the pore fluid and nonlinear precipitation kinetics at the vein wall

multiscale analysis of topographic surface roughness in the midland valley scotland surface roughness is an important geomorphological variable which has been used in the earth and planetary sciences to infer material properties current past processes and the time elapsed since formation no single definition exists however within the context of geomorphometry we use surface roughness as an expression of the variability of a topographic surface at a given scale where the scale of analysis is determined by the size of the landforms or geomorphic features of interest six techniques for the calculation of surface roughness were selected for an assessment of the parameter s behavior at different spatial scales and data set resolutions area ratio operated independently of scale providing consistent results across spatial resolutions vector dispersion produced results with increasing roughness and homogenization of terrain at coarser resolutions and larger window sizes standard deviation of residual topography highlighted local features and did not detect regional relief standard deviation of elevation correctly identified breaks of slope and was good at detecting regional relief standard deviation of slope sdslope also correctly identified smooth sloping areas and breaks of slope providing the best results for geomorphological analysis standard deviation of profile curvature identified the breaks of slope although not as strongly as sdslope and it is sensitive to noise and spurious data in general sdslope offered good performance at a variety of scales while the simplicity of calculation is perhaps its single greatest benefit

the effectiveness of hillshade maps and expert knowledge in mapping old deep seated landslides large deep seated landslides with a shear surface deeper than 3 m and a mean affected area of 4 2 ha are common features in the flemish ardennes none of these deep seated landslides are dated but they are assumed to be rather old 100 years because most of these landslides are located under forest aerial photo interpretation commonly used for the creation of landslide inventories is not a suitable tool to map the landslides in the flemish ardennes therefore an intensive 100 day field survey was carried out by two geomorphologists in a 430 km 2 study area this resulted in a landslide inventory map indicating the location of 135 large deep seated landslides but field surveys are time consuming and thus very expensive therefore a cheaper and faster mapping technique was tested a hillshade map was constructed for the study area in a gis idris132 from a 5 m resolution digital elevation model dem seven experts were given 1 h to indicate all the hillslope sections which they suspected to be possible landslides on a copy of the aforementioned map scale 1 100 000 in total this exercise took only 1 day i e 7 person hours large differences in the number of presumed landslides and the extent of the hillslopes thought to be affected by landslides were reported among the seven experts the polygon and pixel efficiency were introduced to estimate the quality of the landslide maps based on hillshade maps and expert knowledge compared to the field survey based landslide inventory the quality of the landslide inventories based on the hillshade maps and expert knowledge was relatively low experts familiar with the study area obtained somewhat better results than experts who visited the study area only once a combination of the seven expert maps did not result in a good inventory map because too many unaffected hillslopes were incorrectly indicated as affected by landslides the results obtained in this study are comparable to an investigation carried out by wills c j mccrink t p 2002 comparing landslide inventories the map depends on the method environmental and engineering geoscience 8 279 293 although the tested method can never replace a detailed field survey taking into account the proposed improvements it can be used for the creation of a regional inventory map of old landslides in a densely forested area where light detection and ranging lidar data are unavailable c 2004 elsevier b v all rights reserved

oxygen isotope thermometry of quartz calcite veins unraveling the thermal tectonic history of the subgreenschist facies morcles nappe swiss alps combined structural analysis and oxygen isotope thermometry of syntectonic quartz calcite fibrous veins can be used to correlate the thermal history of deformed rocks with specific structural and tectonic events results are presented for the morcles nappe in the western helvetic alps switzerland where mineral parageneses illite crystallinity and fluid inclusion chemistry record an apparent peak metamorphic temperature gradient that increased across the morcles nappe from anchizonal conditions in the foreland to epizonal conditions in its hinterland root zone twenty seven quartz calcite veins were analyzed in this study in order to determine the temperatures of veining during formation and deformation of the nappe peak metamorphic temperatures ranged from 260 to 290 c in the shallower foreland localities and to 330 to 350 c in the deeper more hinterland localities at the end of s1 foliation formation related to large scale folding temperatures gradually decreased throughout the nappe during subsequent development of the s2 foliation and s3 crenulation cleavage uplift and erosion of the overlying nappe pile resulted in slow cooling of the morcles nappe during the waning stages of the alpine orogeny the dominant foliation forming deformation of the morcles nappe occurred at elevated temperatures over the course of 10 to 15 ma combined structure oxygen isotope analyses of quartz calcite veins yield better temperature and temporal constraints on the thermal histories of subgreenschist vein bearing tectonites than do other geothermometers

genesis of natural hydraulic fractures as an indicator of basin inversion abstract satin spar fibrous gypsum veins which occur in evaporite basins worldwide provide significant insights into host rock deformation and fluid flow although the genetic mechanism remains obscure satin spar veins in the red marls of the triassic mercia mudstone of the bristol channel basin were characterized in the context of regional and local setting the vein network in the keuper marl lower mercia exhibits a lack of systematic cross cutting between three distinct vein sets two sets of veins are observed in the overlying tea green marl with one set clearly crossing the other the gypsum veins commonly contain a blocky median zone of multiple thin bands of host rock inclusions and alabastrine gypsum crystals exhibiting crack seal patterns fibrous zones on either side of the median zone consist of pure parallel aligned gypsum fibres that are oblique to vein walls indicating a hybrid shear extensional mode of vein widening veins developed within reverse reactivated faults contain fibre lineations in the median zones and also on vein surfaces suggesting a minimum of two phases of fault slip the veins are interpreted to have formed as a result of overpressure in the low permeability mudstones by tectonic compression during basin inversion giving rise to the median zone growth of gypsum fibres commenced when the initial fractures were completely sealed the timing of vein formation is suggested to be miocene based on cross cutting relationships with folds formed during the latest phase of basin inversion because the fractures initiated in response to fluid overpressures they provide a useful analog to subsurface hydraulic fracture systems in low permeability rocks subjected to tectonic compression the fibrous widening of the veins post dates their initiation and led to continued propagation and increased connectivity

structural analysis of turtle mountain alberta using digital elevation model toward a progressive failure abstract in 1903 the eastern slope of turtle mountain alberta was affected by a 30 m m 3 rockslide named frank slide that resulted in more than 70 casualties assuming that the main discontinuity sets including bedding control part of the slope morphology the structural features of turtle mountain were investigated using a digital elevation model dem using new landscape analysis techniques we have identified three main joint and fault sets these results are in agreement with those sets identified through field observations landscape analysis techniques using a dem confirm and refine the most recent geology model of the frank slide the rockslide was initiated along bedding and a fault at the base of the slope and propagated up slope by a regressive process following a surface composed of pre existing discontinuities the dem analysis also permits the identification of important geological structures along the 1903 slide scar based on the so called sloping local base level slbl an estimation was made of the present unstable volumes in the main scar delimited by the cracks and around the south area of the scar south peak the slbl is a method permitting a geometric interpretation of the failure surface based on a dem finally we propose a failure mechanism permitting the progressive failure of the rock mass that considers gentle dipping wedges 30 the prisms or wedges defined by two discontinuity sets permit the creation of a failure surface by progressive failure such structures are more commonly observed in recent rockslides this method is efficient and is recommended as a preliminary analysis prior to field investigation

internal structure and deformation of an unstable crystalline rock mass above randa switzerland part i internal structure from integrated geological and geophysical investigations 6m 3 of material occurred in fractured gneissic rock whose principal foliation faults and fracture zones dip into the slope above the scarp of the second rockslide the mountain continues to move at rates of up to 2 cm year in an attempt to understand failure mechanisms in fractured crystalline rock masses we have carried out a comprehensive multidisciplinary study that included detailed geological mapping borehole logging and imaging and surface and borehole geophysical surveys an integrated interpretation of the resultant data has revealed the presence of three prominent fault and fracture zone sets that define the internal structure of the rock mass some faults and fracture zones could be traced up to 85 m into the subsurface using borehole radar reflection methods the dips of the faults and fracture zones estimated from surface mapping matched those from radar reflection and borehole televiewer surveys no evidence was found for significant faults or persistent weakness planes that paralleled the 1991 rockslide failure surfaces instead the new observations were consistent with dominant failure mechanisms that involve the progressive development of major shear and brittle fracturezones and the eventual destruction of intact rock bridges immediately prior to catastrophic collapse this integrated study provides the first reliable model of the 3 d fault structure associated with and contributing to a large rock slope instability in a brittle crystalline rock mass

the pyeongan supergroup upper paleozoic lower triassic in the okcheon belt korea a review of stratigraphy and detrital zircon provenance and its implications for the tectonic setting of the eastern sino korean block abstract the tectonic setting of the okcheon belt in the korean peninsula has long been regarded as one of the important topics in discussing east asian tectonics the controversial tectonic setting of the okcheon belt before the triassic collision between north and south china limits proper understanding of the late paleozoic tectonics of east asia focusing on the upper paleozoic to lower triassic pyeongan supergroup coeval sedimentary records in different parts of the okcheon belt are reviewed this study has a clear advantage over previous assessments that build upon comparison between meta sedimentary units of unknown age in the region the pyeongan supergroup sediments show high similarity in both stratigraphy and detrital zircon u pb ages throughout the okcheon belt they are distinct from their age equivalents in south china while sharing characteristics with those in north korea and north china critical criteria include marine influence and enrichment of organic materials at each time period and relative proportion of mesoproterozoic silurian components in detrital zircon age population the combined results agree with the view that the entire okcheon belt was a single tectonic unit at least by the late carboniferous the results of this study favor the idea of the sino korean block encompassing the whole korean peninsula and cast doubts on the tectonic models that attribute the southern part of the korean peninsula to the south china block a retroarc foreland basin setting of the okcheon belt with detritus mainly provided from a subduction related orogen in the continent sided japan is inferred from the provenance characteristics of the detrital zircons

gravity induced rock mass damage related to large en masse rockslides evidence from vajont abstract the vajont landslide is a well known reservoir induced slope failure that occurred on 9 october 1963 and was characterized by an en masse sliding motion that triggered various large waves determining catastrophic consequences for the nearby territory and adjacent villages during the vajont dam construction and especially after the disaster some researchers identified widespread field evidence of heavy rock mass damage involving the presumed prehistoric rockslide and or the 1963 failed mass this paper describes evidence of heavy gravitational damage including i folding ii fracturing iii faulting and iv intact rock disintegration the gravity induced rock mass damage grmd characterizes the remnants of the basal shear zone still resting on the large detachment surface and the 1963 failed rock mass the comprehensive geological study of the 1963 vajont landslide based on the recently performed geomechanical survey 2006 present and on the critical analysis of the past photographic documentation 1959 1964 allows us to recognize that most grmd evidence is related to the prehistoric multistage mt toc rockslide the 1963 catastrophic en masse remobilization induced an increase to the prehistoric damage reworking preexisting structures and creating additional gravity driven features folds fractures faults and rock fragmentation the gravity induced damage was formed during the slope instability phases that preceded the collapse static or quasi static grmd and also as a consequence of the sliding motion and of the devastating impact between the failed blocks dynamic grmd gravitational damage originated various types of small drag folds such as flexures concentric folds chevron and kink box folds all having a radius of 1 5 m large buckle folds radius of 10 50 m are related to the dynamic damage and were formed during the en masse motion as a consequence of deceleration and impact processes that involved the sliding mass prior to failure unstable rock slopes can be affected by diffuse newly formed gravity driven joints that are absent in the surrounding area and within the underlying bedrock as the vajont case history demonstrates joint sets j9 and j10 these fractures caused by critical tensile and shear stresses represent an important mechanical clue to recognizing on a geological basis the instability condition of a rock slope under investigation owing to its complex geological evolution the vajont landslide is an outstanding example to help learn about cumulative grmd effects that can accumulate over time when an ancient rockslide is further remobilized by a sudden en masse sliding motion

global time scale and regional stratigraphic reference scales of central and west europe east europe tethys south china and north america as used in the devonian carboniferous permian correlation chart 2003 dcp 2003 the boundaries of the devonian carboniferous and permian stages of the global stratigraphic reference scale abbreviated to global stratigraphic scale gss are described in relation to the biostratigraphic and or lithostratigraphic units of the regional stratigraphic reference scales abbreviated to regional stratigraphic scales rss of central and west europe east europe tethys south china eastern tethys and north america in their type regions the boundaries of gss units rarely coincide with those of homonymous rss units moreover the definitions of some rss units have changed several times over the last decades and subsequent misunderstanding of the stratigraphical significance of these changes has often introduced errors into proposed global correlation charts the stratigraphic framework proposed in our global devonian carboniferous permian correlation chart 2003 dcp 2003 devonian carboniferous permian correlation chart 2003 menning m schneider j w alekseev a s amon e o becker g von bitter p h boardman d r bogoslovskaya m braun a brocke r chernykh v chuvashov b i clayton g dusar m davydov v i dybova jachowicz s forke h c gibling m gilmour e h goretzki j grunt t a hance l heckel p h izokh n g jansen u jin y g jones p kading k ch kerp h kiersnowski h klets a klug ch korn d kossovaya o kotlyar g v kozur h w laveine j p martens th nemyrovska t l nigmadganov a l paech h j peryt t m rohn r roscher m rubidge b schiappa t a schindler e skompski s ueno k utting j vdovenko m v villa e voigt s wahlman g p wardlaw b r warrington g weddige k werneburg r weyer d wilde v winkler prins c f work d m 2004 abschlusskolloquium dfg schwerpunktprogramm 1054 evolution des systems erde wahrend des jungeren palaozoikums im spiegel der sedimentgeochemie abstracts univ erlangen germany 2004 p 43 herein abbreviated to dcp 2003 and cited as dcp 2003 in references is an attempt to reduce these errors the dcp 2003 is the stratigraphic base for project 1054 of the deutsche forschungsgemeinschaft dfg the evolution of the late palaeozoic in the light of sedimentary geochemistry this composite time scale has been carefully balanced as far as data allows to remove unnecessary artificial compression and expansion of time intervals biozonations and depositional events the ages selected in dcp 2003 are markedly different to those in the geologic time scale 1989 gts 1989 harland w b armstrong r l cox a v craig l e smith a g smith d g 1990 a geologic time scale 1989 cambridge univ press cambridge harland w b armstrong r l cox a v craig l e smith a g smith d g 1990 a geologic time scale 1989 cambridge univ press cambridge pp 1 263 and in gradstein and ogg gradstein f m ogg j 1996 a phanerozoic time scale episodes 19 1 2 3 4 insert whereas they are closer to those of the geologic time scale 2004 gts 2004 gradstein f m ogg j g smith a g 2004 a geologic time scale 2004 cambridge univ press cambridge pp 1 589 mostly the ages are rounded to the nearest 0 5 ma in order to avoid estimates of questionable accuracy whereas ages of 0 1 ma in the gts 2004 and their error bars of 0 4 ma to 2 8 ma for the devonian to permian stage boundaries suggest an improved accuracy in contrast in the dcp 2003 questionable ages and positions of stratigraphic boundaries are marked by arrows c 2006 elsevier b v all rights reserved

why did the 1756 tjellefonna rockslide occur a back analysis of the largest historic rockslide in norway abstract on 22 february 1756 the largest historically recorded rockslide in norway took place at tjelle in the langfjord western norway the rockslide created three displacement waves of up to 50 m in height that caused 32 casualties and destroyed most houses and boats along the shores of the langfjord the trigger and contributing factors leading to the tjellefonna rockslide are largely unknown and even seismic triggering has previously been suggested this study provides a thorough back analysis of the tjellefonna rockslide using detailed geomorphological engineering geological and tectonic field mapping in combination with topographic reconstructions bathymetry analysis volume estimations and numerical slope stability analysis the back scarp and eastern flank of the tjellefonna scar form several tens of meter high rock walls while the basal failure surface and other parts of the scar are covered by rock avalanche debris that extend from the back scarp down to the bottom of the langfjord the rockslide occurred in granodioritic gneisses with variably developed metamorphic foliation that is folded and strike parallel to the fjord two prominent fault zones are present in close proximity to the tjellefonna scar one is steeply se dipping tjelle fault while the other one is sub horizontal to shallow se dipping ritlehamran fault both fault zones are linked to the more trondelag fault complex with one of its branches forming the langfjord lineament and probably also the faults at tjellefonna additionally there are four persistent joint sets that together with the metamorphic foliation and the tjelle fault define the back scarp of the rockslide and give a fracturing of the rock mass corresponding to a geological strength index gsi of 45 55 the gsi decreases significantly to 10 20 in the fault zones which form distinct weakness zones in the rock slope volume estimates based on a reconstruction of the ante rockslide topography range from 9 3 to 10 4 million m 3 which is lower than previous volume estimates 12 15 million m 3 large portions of the failed rock mass remained on land and only approximately 3 9 million m 3 entered the fjord the observed discontinuities in the rock mass at tjellefonna do not allow for a simple kinematic failure mechanism due to the lack of moderately se dipping structures the basal failure surface was most likely not composed of a single structure but of a complex interplay of fault zones metamorphic foliation joints and broken rock bridges numerical slope stability modelling highlights that weak fault zones are essential for the development of the failure surface over a long time this progressive failure was likely aided by low to medium magnitude earthquakes that are frequent in the region numerical slope stability modelling and historical accounts suggest however that heavy long lasting rainfall was the triggering factor for the 1756 tjellefonna rockslide rather than an earthquake

early carboniferous onset of gondwanian glaciation and neo tethyan rifting in south tibet at least four diamictite bearing intervals of early carboniferous age containing faceted pebbles trapezoidal cobbles and boulders up to 1000 m3 in volume have been recognized and traced for over 200 km along the tethys himalayan zone of south tibet from east of everest to west of shishapangma these largely glacio marine sediments intercalated within the rakyang formation which overlies lower tournaisian limestones and underlies lower bashkirian black shales were deposited during the visean to serpukhovian shore ice thus began to form in this region of northern gondwana several tens of million years earlier than previously thought this glacial event occurred at middle southern latitudes and was triggered by basin inversion and tectonic uplift in the first stages of neo tethyan rifting as documented by the close association of diamictites with olistoliths and olistostromes in lower carboniferous units after a transgressive interglacial episode in the bashkirian a much more widespread glaciation occurred in the latest carboniferous and was shortly followed by continental break up and opening of neo tethys in the late early permian

carboniferous permian carbon isotope stratigraphy of successions from china yangtze platform usa kansas and russia moscow basin and urals abstract the pennsylvanian and early permian were times of extreme sea level changes of 100 to perhaps up to 200 m for example glacio eustatic sea level changes are well documented from the us midcontinent moscow basin and yangtze platform where more than 100 stacked subtidal to supratidal sequences have been described in contrast carbonates developed in the ural mountains and south guizhou of the yangtze platform were deposited in ramp and slope settings 13c values of whole rock samples from the us midcontinent and moscow basin were intensively affected by diagenesis only well preserved brachiopod shells maintained their original carbon isotope ratios in contrast limestones deposited in the deeper water slope environments were not affected by meteoric diagenesis and are interpreted to have mainly retained their carbon isotope ratios mean 13c values of slope carbonates of the yangtze platform increase from about 3 during the visean and serpukhovian to 5 at the carboniferous permian boundary and decrease to values around 2 in the early kungurian this positive 13c excursion coincides with low 13c values in the yangtze platform successions which were reset by meteoric diagenesis the highest 13c values recorded in the slope succession coincide with the inferred maximum glaciation that caused pronounced sea level lowstands short lived but significant negative 13c excursions in the chinese slope succession are interpreted to reflect changes in ocean circulation due to sea level rises which caused enhanced production and or preservation of organic matter which influenced the subsequent early diagenetic cementation

the 1963 vajont landslide a numerical investigation on the sliding surface heterogeneity the 1963 vajont landslide is a key case in landslide literature because it was catastrophic and because a lot of accurate data were collected before and after its occurrence in this paper the main focus is on the possible heterogeneity of the sliding surface involved by the landslide motion which is reflected by a heterogeneous distribution of the dynamic basal friction coefficient assuming a given zonation of the sliding surface our strategy was to apply a 2d lagrangian model to compute the landslide motion and to find the values of for each zone leading to the best agreement between the computed and the observed final deposit following some hints from the literature we have explored heterogeneous configurations composed of up to four different zones including also the homogeneous case by means of a 2d numerical model ubo block2 that handles the landslide as a mesh of blocks and runs quickly enough to allow the computation of tens of thousands of simulations in a reasonable computing time it is found that the four zone zonation produces the best fit or the least misfit which is a strong hint that the gliding surface involved different geotechnical units

a global review of the late mississippian carboniferous gigantoproductus brachiopoda faunas and their paleogeographical paleoecological and paleoclimatic implications abstract the gigantic gigantoproductus bearing brachiopod fauna is one of the most distinct marine benthic faunas in the late mississippian early carboniferous in terms of its huge size extremely thick shell and delicate costation a global review of 145 different occurrences throughout the world reveals a total of 57 gigantoproductus species recorded our investigation into their spatial and temporal distributions indicates that gigantoproductus was originated from the moscow basin in the middle visean and then in the late visean migrated southwestward to western europe and north africa and eastward to north china south china and japan the genus reaches its acme stage in species diversity and abundance in the late visean then gradually declined in the early serpukhovian and finally disappeared in the late serpukhovian gigantoproductus and its related genera were distributed mainly in the circum paleotethys region in the tropical and subtropical zones and favored a relatively shallow shelf environment with high energy and warm water condition with little thermal tolerance the absence of the gigantoproductus and its related genera in america suggests the east west rheic seaway was closed before the gigantoproductus fauna appeared in the middle visean the waxes and wanes of the gigantoproductus faunas temporally coincided with the paleoclimatic shift from greenhouse to icehouse stage in the late visean and early serpukhovian and the final extinction of these gigantic brachiopods in the late serpukhovian implies tropical cooling towards the late serpukhovian by the expansion of the lpia glaciers

characterising spectral spatial and morphometric properties of landslides for semi automatic detection using object oriented methods recognition and classification of landslides is a critical requirement in pre and post disaster hazard analysis this has been primarily done through field mapping or manual image interpretation however image interpretation can also be done semi automatically by creating a routine in object based classification using the spectral spatial and morphometric properties of landslides and by incorporating expert knowledge this is a difficult task since a fresh landslide has spectral properties that are nearly identical to those of other natural objects such as river sand and rocky outcrops and they also do not have unique shapes this paper investigates the use of a combination of spectral shape and contextual information to detect landslides the algorithm is tested with a 5 8 m multispectral data from resourcesat 1 and a 10 m digital terrain model generated from 2 5 m cartosat 1 imagery for an area in the rugged himalayas in india it uses objects derived from the segmentation of a multispectral image as classifying units for object oriented analysis spectral information together with shape and morphometric characteristics was used initially to separate landslides from false positives objects recognised as landslides were subsequently classified based on material type and movement as debris slides debris flows and rock slides using adjacency and morphometric criteria they were further classified for their failure mechanism using terrain curvature the procedure was developed for a training catchment and then applied without further modification on an independent catchment a total of five landslide types were detected by this method with 76 4 recognition and 69 1 classification accuracies this method detects landslides relatively quickly and hence has the potential to aid risk analysis disaster management and decision making processes in the aftermath of an earthquake or an extreme rainfall event

structural and geomorphological features of landslides in the bhutan himalaya derived from terrestrial laser scanning abstract this study presents data on landslides affecting the main west east transport corridor in the himalaya of eastern bhutan close to the main central thrust the study focuses on the extraction of structural and geometrical information from terrestrial laser scanning tls data utilising a case study landslide the namling landslide analyses of the tls data allow extraction of slide geometry discontinuity orientations and identification of the mode of failure the tls results are compared to a traditional engineering geological survey and prove to yield considerable added value and should form the basis of new approaches to geomorphological studies and site assessment macro scale geomorphological reconnaissance findings are outlined and interpreted within a conceptual model of the evolution of landslide features here termed hierarchical landsliding it is concluded that the nam ling landslide is indicative of deeper seated deformation and is not purely a function of road construction

kinematics of crystal growth in syntectonic fibrous veins abstract detailed observations of a set of fibrous antitaxial calcite veins in a slate reveal that some of the calcite fibres do not connect material markers on both sides of the vein and can therefore not have tracked the full opening trajectory during vein growth this calls for a better understanding of the mechanisms of fibre formation and reliable criteria to test the tracking hypothesis based on surface roughness characteristics of the vein wall we develop a simple model for shape growth of crystals in a crack seal environment which can account for both tracking and non tracking behaviours and propose a set of tracking criteria for antitaxial veins finally we discuss ways by which the model can be tested against natural examples

surface roughness characterization of open and closed rock joints in deep cores using x ray computed tomography this research was supported by a grant from the project of the korea institute of energy technology evaluation and planning ketep funded by the ministry of trade industry energy of the korean government no 20123010110010 this work was also carried out in the framework of the european union s horizon 2020 research and innovation programme destress no 691728 and funded by the international r d programme no n0002098 of korea institute for advancement of technology kiat

a morphologic characterisation of the 1963 vajont slide italy using long range terrestrial photogrammetry abstract the 1963 vajont slide in northeast italy is an important engineering and geological event although the landslide has been extensively studied new insights can be derived by applying modern techniques such as remote sensing and numerical modelling this paper presents the first digital terrestrial photogrammetric analyses of the failure scar landslide deposits and the area surrounding the failure with a focus on the scar we processed photogrammetric models to produce discontinuity stereonets residual maps and profiles and slope and aspect maps all of which provide information on the failure scar morphology our analyses enabled the creation of a preliminary semi quantitative morphologic classification of the vajont failure scar based on the large scale tectonic folds and step paths that define it the analyses and morphologic classification have implications for the kinematics dynamics and mechanism of the slide metre and decametre scale features affected the initiation direction and displacement rate of sliding the most complexly folded and stepped areas occur close to the intersection of orthogonal synclinal features related to the dinaric and neoalpine deformation events our analyses also highlight for the first time the evolution of the vajont failure scar from 1963 to the present

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

geostatistical analysis of glacier roughness data in most glaciological and hydrological models surface roughness of snow and ice is an important parameter however roughness is generally used only as an estimated parameter for lack of available observations in this paper we present a method to collect and analyze ice surface roughness data using a specially designed instrument for survey and geostatistical methods for analysis the glacier roughness sensor grs built at the university of trier records variations in microtopography at 0 2 m 0 1 m resolution when pulled across an ice surface global positioning system data are used for location after several processing steps the data are analyzed using geostatistical methods the mathematical tool used to achieve a morphological characterization of ice surface types is the variogram grs data variograms and surface roughness analysis are ideal matches for morphological characterization because none of them requires or provides absolute elevation values morphology is described not by absolute elevation values but by the change of elevation in space which is the derivative of elevation surface roughness values the variogram is calculated from incremental values parameters extracted from variograms of grs data serve to distinguish lake surfaces wind structures ridge and vauey systems melting structures and blue ice areas examples are from jakobshavn isbrae drainage basin west greenland

stratigraphic imprint of the late palaeozoic ice age in eastern australia a record of alternating glacial and nonglacial climate regime stratigraphic and sedimentological data from new south wales and queensland eastern australia indicate that the late palaeozoic ice age comprised at least eight discrete glacial intervals each 1 8 ma in duration here termed glaciations separated by nonglacial intervals of comparable duration these events spanned an interval from mid carboniferous c 327 ma to the early late permian c 260 ma and illustrate a pattern of increasing climatic austerity and increasingly widespread glacial ice from initial onset until an acme in the late early permian followed by an opposite trend towards the final demise of glaciation in the late permian the alternating glacial nonglacial motif suggests that the late palaeozoic ice age was considerably more dynamic than previously thought these patterns are remarkably consistent with recent interpretations of palaeofloral change eustatic sea level fluctuations and co 2 climate glaciation relationships for this interval of time the detailed record of alternating glacial and nonglacial climate mode disclosed herein may facilitate more closely resolved evaluations of stratigraphic records elsewhere notably in far field ice distal northern hemisphere successions

ice volume and paleoclimate history of the late paleozoic ice age from conodont apatite oxygen isotopes from naqing guizhou china abstract a high resolution and continuous conodont apatite oxygen isotope record spanning the late visean to middle permian is reported from south china which is interpreted with respect to the ice volume and or tropical seawater temperature history of the late paleozoic ice age lpia the presented 18o record shows significant fluctuations in 18o from the late visean to middle permian with highest values observed in the bashkirian early pennsylvanian the 18o maximum coincides with a major eustatic sea level fall recorded in low latitude successions and postdates the significant increases in 87sr 86sr and 13ccarb measured on well preserved brachiopod calcite which can be interpreted as reflecting intensified weathering as consequence of the closure of rheic ocean as well as enhanced carbon burial both processes may have contributed to lower greenhouse gas levels and cooled down the earth s surface triggering the maximum glaciation the high bashkirian 18o values are interpreted to represent the glacial maximum of the lpia a coeval change in faunal composition and a decreasing diversity in climate sensitive marine invertebrates can be ascribed to icehouse cooling and or loss of habitat despite inconsistencies with earlier interpretations that the early permian represented the glacial maximum of the lpia as inferred from gondwanan glacial sediments records the suggested bashkirian glacial maximum agrees well with ice extent estimates based on the regional tectonic history in gondwana which suggests that the bashkirian glaciation occurred during gondwana interior uplift promoting maximum ice cover of the entire lpia however maximum glaciation is only poorly represented in the depositional record because large parts of the glacial deposits were possibly removed by erosion as outlined by a major regional unconformity

the magnitude of late paleozoic glacioeustatic fluctuations a synthesis a comprehensive literature review shows that the magnitude of eustatic fluctuations varied throughout the carboniferous and permian and that at least eight distinct phases can be recognized facies juxtapositions in carbonate successions and erosional relief in clastic successions indicate that glacioeustatic fluctuations of 20 25 m and occasionally as much as 60 m took place throughout the early mississippian tournaisian a widely recognized glacial period middle mississippian mid chadian through holkerian shallow marine carbonate and clastic successions indicate that eustatic fluctuations were 10 25 m a decrease that matches well with the paucity of coeval glacial deposits late visean asbian through mid brigantian glacioeustatic fluctuations of 10 50 m record the initial phases of ice accumulation in advance of the widespread mid carboniferous glacial event the latest mississippian earliest pennsylvanian mid brigantian through langsettian was a time of widespread glaciation and strata of this age commonly exhibit evidence of glacioeustatic fluctuations of as much as 40 100 m although middle pennsylvanian duckmantian through asturian glacial deposits are present in eastern australia paleovalley depths suggest that coeval glacioeustatic fluctuations were less than 40 m glacioeustatic fluctuations of as much as 100 120 m have been widely reported from late pennsylvanian earliest permian stephanian through mid sakmarian successions in north america an increase that corresponds to the growth of large ice sheets across much of gondwana and the accumulation of ice in the northern hemisphere incision and facies juxtaposition in early middle permian mid sakmarian through kungurian successions in eastern australia indicate that glacioeustatic fluctuations of 30 70 m occurred during the waning stages of major glaciation erosional relief in paleoequatorial carbonates and the presence of coeval glacial deposits in australia suggests that eustatic fluctuations of 10 60 m occurred during the final stages of glaciation in the middle to late permian roadian through capitanian but the modest size of most of these fluctuations makes it difficult to isolate the glacioeustatic signature this review demonstrates that far field cyclic successions record changing glacial conditions in gondwana that the magnitude of glacioeustatic fluctuations was directly related to the volume of glacial ice that carboniferous permian glacioeustasy was more variable than previously recognized and that generalizations from short temporal intervals are probably not representative of the late paleozoic ice age as a whole although any attempt to quantify the magnitude of ancient eustatic changes is based on caveats and assumptions this review incorporates the results of over 100 published papers on the topic in an attempt to minimize the errors inherent in any one study

microstructural evolution and grain boundary structure during static recrystallization in synthetic polycrystals of sodium chloride containing saturated brine the effects of brine on recrystallization in halite are well known however properties of brine such as morphology connectivity diffusivity and the resulting influences on deformation mechanisms are still a matter of debate this paper presents a microstructural study of dense statically recrystallizing synthetic polycrystalline halite containing small amounts of brine we used powders of two different grain size classes 10 m and 200 355 m the aggregates were compacted to brine filled porosities less than about 2 and annealed at room temperature without an external stress field

insights from analogue modelling into the deformation mechanism of the vaiont landslide abstract the vaiont landslide southern alps italy represents one of the most catastrophic landslides in the world recorded in the modern history the landslide occurred on 9th october 1963 involved about 3 10 8 m 3 of rock that collapsed in an artificial lake more than 1900 people died as a consequence of the tsunami produced by the sudden fall of the mass in the water despite the importance of this event many aspects of the vaiont rockslide still remain unexplained particularly its fast emplacement in order to obtain a better understanding of the vaiont disaster this paper focuses on the results of analogue models designed to get insights into the internal and surficial deformation patterns that characterized the sliding rock mass plan view reconstructions of surface model displacement reveal that the rock mass is subdivided into compartments with different relative movements and differential rotations believed to have played a significant role in causing the fast collapse the deformation of the analogue models compared with geological cross sections and in situ data suggests that sliding of the rock mass was accomplished by the development of some new or the reactivation of pre existing fractures into the rock mass

crack seal fibre growth mechanisms and their significance in the development of oriented layer silicate microstructures abstract an analysis of crack seal fibre growth mechanisms has shown two important implications of the crack seal process for the interpretation of microstructures in low grade metamorphic rocks 1 1 the ability of fibre growth to track the incremental separation history of crack walls depends on details of the nucleation and growth mechanisms 2 2 fibrous crystals may develop cristallographic preferred orientations in certain crack seal situations the microstructures of layer silicates and associated phases developed in several examples of syntectonic intragranular microfracture sites and veins indicates that layer silicate 001 and grain shape preferred orientation can develop during crack seal deformation by oriented growth mechanisms during successive crack seal increments preferred orientation may develop in response to an interaction between anisotropic growth kinetics and the displacement history resulting in preferential rejoining by syntaxial overgrowth of pulled apart grains having fast growth directions parallel to the incremental displacement direction across a microcrack preferred orientation may also be developed and enhanced in crack seal growth sites by overgrowth of previously oriented layer silicates in the microcrack walls in this case the crystallographic preferred orientation need not be simply related to the displacement history during crack seal fibre growth since crack seal processes may operate on all scales down to the minimum size of a microfracture in a deforming rock such mechanisms of layer silicate preferred orientation development are expected to be very significant in developing and enhancing foliation during deformation involving microfracture and solution transfer processes