pore properties as indicators of breakdown mechanisms in experimentally weathered limestones the results are reported of four experimental weathering tests freeze thaw wetting and drying slake durability and salt weathering on five different types of limestone effective porosity mercury intrusion porosimetry and scanning electron microscopy were used to evaluate changes in pore properties while weight loss and fracture density were used to assess deterioration severity a primary aim was to observe modifications in porosity due to weathering and to draw inferences about the internal rock deterioration mechanisms taking place it is concluded that the five limestones not only show a wide range of resistance to weathering in general but considerable difference in resistance to particular weathering processes consequently when assessing durability it is essential to consider rock properties in the context of the weathering process to which the rock is subject the type of deterioration indicator used is also important in interpretation of durability a variety of pore modification mechanisms operate including changes in pore connectivity pore infilling and the introduction of additional void space there are indications that changes to the internal pore structure of rocks due to weathering may be a precursor to more substantial macrodeterioration copyright 2001 john wiley sons ltd

orbital scale glacio eustasy in the middle devonian detected using oxygen isotopes of conodont apatite implications for long term greenhouse icehouse climatic transitions abstract results from previous paleoclimate studies indicate gondwanan glaciation marking the onset of middle paleozoic icehouse climate conditions began by the latest devonian famennian more recently 18o trends from conodont apatite suggest cooling middle devonian subtropical seasurface temperatures 20 my prior to famennian glaciation and high latitude temperatures cool enough to permit the growth of continental glaciers which controlled longer term my scale glacio eustasy this study evaluates the details and patterns of middle devonian high frequency thirteen complete middle devonian givetian subtidal cycles 0 5 3 m thick in the little cedar formation of southeastern iowa are characterized by oxygenated offshore facies transgression poorly oxygenated offshore facies maximum flooding a return to oxygenated facies and are capped by bioturbated lower shoreface facies regression lowstand which lack evidence of subaerial exposure across shelf cyclostratigraphic facies relationships suggest relatively subdued water depth changes were responsible for cycle development measured 18o values from conodont apatite range from 15 9 to 18 4 and repeated systematic intracycle trends are dominated by lower isotopic values in offshore facies and higher isotopic values in cycle capping lower shoreface facies which is consistent with glacio eustasy driving the water depth changes the average 0 6 magnitude of intracycle isotopic shift 0 2 to 1 0 total range suggests 15 23 m glacio eustatic oscillations were responsible for observed water depth changes the higher range of intracycle isotopic magnitudes may be the result of increased subtropical evaporation rates during glacial stages which locally enriched surface seawater 18o values orbital scale

a tale of shales the relative roles of production decomposition and dilution in the accumulation of organic rich strata middle upper devonian appalachian basin abstract a new consensus on the processes responsible for organic carbon burial in ancient epeiric seas has emerged more firmly grounded in the uniformitarian framework of modern oceanography and biogeochemistry this consensus recognizes the interdependent roles of sedimentation primary production and microbial metabolism in favor of earlier end member models e g production vs preservation in this study one of the classic stratigraphic sequences upon which the preservation end member was based is re interpreted in light of this new consensus the study employs an extensive new sedimentological biogeochemical database from cores drilled in western new york the database spans over 500 m and 15 my of devonian deposition in the appalachian basin and provides a framework for comparative study of organic matter burial the major conclusions are 1 few organic rich units were deposited under pervasive anoxic sulfidic water columns 2 establishment and breakdown of seasonal thermoclines on annual or longer timescales were the predominant mode of stratification and 3 under such conditions remineralization of bio limiting nutrients may have played a key role in organic matter burial by creating a eutrophication pump this pump may have augmented an already rising nutrient inventory such that productivity levels exceeded the threshold required for development of suboxic to anoxic conditions in sediments and episodically in bottom waters a final conclusion asserts that the master variable for organic matter accumulation was relative sea level change which exerted influence on clastic dilution preservation and production processes sea level rise events led to sediment starvation and organic carbon concentration in distal basin sediments as well as to decreased effectiveness of seasonal mixing and thus longer build up intervals for remineralized nutrients episodic mixing of nutrient enriched bottom waters led to enhanced production ultimately increased clastic sediment delivery and water column mixing during relative sea level fall diluted surface sediment organic content such that respiratory demand could be met by increased oxygen supply thus terminating deposition of strata enriched in organic carbon

carbonate shale cycles in the middle devonian of new york an evaluation of models for the origin of limestones in terrigenous shelf sequences thin widespread carbonate beds in the predominantly siliciclastic hamilton group middle devonian of new york appear to represent biogenic accumulations of winnowed shallow normal to storm wave base shelf areas rather than products of transgression induced sediment starvation as frequently assumed in western new york these fossiliferous limestones form the centers of subsymmetrical marine cyclothems carbonates are overlain and underlain by calcareous gray to black laminated shales and they grade laterally into siltstones or sandstones that cap upward coarsening sequences in central new york thus the limestones appear to represent shallow water facies of regressive hemicycles instead of transgressive maxima as argued by earlier workers

inversion of controlled source audio frequency magnetotellurics data for a horizontally layered earth we present a technique for inverting controlled source audio frequency magnetotelluric csamt data to recover a 1 d conductivity structure the earth is modeled as a set of horizontal layers with constant conductivity and the data are apparent resistivities and phases computed from orthogonal electric and magnetic fields due to a finite dipole source the earth model has many layers compared to the number of data points and therefore the solution is nonunique among the possible solutions we seek a model with desired character by minimizing a particular model objective function traditionally csamt data are inverted either by using the far field data where magnetotelluric mt equations are valid or by correcting the near field data to an equivalent plane wave approximation here we invert both apparent resistivity and phase data from the near field transition zone and the far field regions in the full csamt inversion without any correction our inversion is compared with that obtained by inverting near field corrected data using an mt algorithm both synthetic and field data examples indicate that a full csamt inversion provides improved information about subsurface conductivity

water geochemistry controlled by carbonate dissolution a study of the river waters draining karst dominated terrain guizhou province china concentrations of major ions and sr and sr isotopic compositions of two major river systems wujiang river and yuanjiang river in karst dominated regions and during winter were measured the rivers and their tributaries have high total dissolved solid concentrations with tz ranging from 2 1 to 6 3 meq l which are significantly higher than that of the global river average calcium and hco3 followed by mg2 and so42 dominate the chemical composition of major ions in the river waters both na k and cl si account for 5 10 of the cations and anions respectively the waters of the wujiang river have high sr2 concentrations and lower 87sr 86sr ratios 0 7077 0 7110 while those of the qingshuijiang river one of two major tributaries of the yuanjiang river system show higher sr isotopic ratios 0 7090 0 7145 and low sr concentrations the lithology and geography of the river basins largely control the chemical and isotopic compositions of these rivers analyses of the stoichiometry of the river waters show that the water chemistry is controlled by carbonate dissolution by both carbonic and sulfuric acid especially of the wujiang river and suggest an origin of sulfate mainly from atmospheric input because of coal combustion and or oxidation of sulfide minerals in the catchments we identify three main weathering sources limestone dolomite and silicates chemical and sr isotopic composition of wujiang river waters are characterized mainly by limestone weathering while those of the qingshuijiang river waters mainly by dolomite and silicate weathering chemical weathering rates of carbonate and silicate are estimated and the results indicate that the chemical weathering rates of carbonate in the catchments are remarkably high significantly higher than most large rivers it is considered that presence of sulfuric acid in the rock weathering overuse of land and deterioration of vegetation are most likely the key factors responsible for the high weathering rates of carbonate in the catchments

symmetrical and upward shallowing cycles in the middle devonian of new york state and their implications for the punctuated aggradational cycle hypothesis the middle devonian eifelian and givetian hamilton group in western and central new york composed largely of fossil rich marine shelf and slope facies is subdivisible into repetitive facies sequences of varying thicknesses minor cycles include 1 to 3 m thick upward coarsening shale to siltstone hemicycles resembling sixth order punctuated aggradational cycles pacs in central new york probably correlative 0 5 1 0 m shale to argillaceous nodular limestone couplets occur in western areas major cycles in western new york include subsymmetrical 3 to 5 m thick packages with medial limestone beds analogous to upper limestones of pennsylvanian cyclothems the center of each cycle marks a regressive maximum and grades vertically above and below into black shale or dark gray mudstone corresponding in a facies sense to cyclothemic core shales in the midcontinent pennsylvanian these widespread units appear to be allocyclic in nature and approximate fifth order transgressive regressive cycles based upon average unit thickness relative to the encompassing well zoned hamilton sequence correlations show that most key regressive events marked by limestones in western new york are expressed by equivalent siltstone or fine sandstone units in central new york most cycles which are nearly symmetrical in western new york grade eastward into 5 to 20 m upward coarsening pac motif hemicycles these asymmetric cycles apparently reflect rapid sediment aggradation to limits imposed by wave energy in a region of abundant sediment supply further minor shallowing was accompanied by winnowing and bypass of fine grained sediments generating condensed capping deposits of coarser silt and sand reworked shells and commonly phosphatic nodules ensuing sea level rises were accompanied by initial sediment starvation followed by sedimentation in deeper water hence asymmetrical upward shallowing hemicycles pacs appear to grade offshore into thin but symmetrical cycles both pac and symmetrical motifs are local responses to the same probably allocyclic sea level fluctuations we suggest that the pac motif is partially facies controlled being largely restricted to shallow shelf settings with relatively high rates of sediment accumulation

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

identifying crack initiation and propagation thresholds in brittle rock recent work at the underground research laboratory of atomic energy of canada limited in pinawa manitoba has shown that high compressive stresses near the tunnel face significantly contribute to

recent developments in surface and subsurface karst geomorphology an introduction abstract where dissolution processes of bedrock dominate peculiar morphologies develop and overrule all landforms controlled by other surface processes pure karst landscapes are present in many parts of the world but most of the time landscapes are shaped by a multitude of processes the comprehension of the dissolution processes that act both at the surface and underground has developed rapidly in the last half century although major achievements had already been reached at the end of the xixth century this special issue gives an overview of some of the most recent developments in surface and subsurface karst geomorphology and reviews where further studies should be fostered

coastline retreat via progressive failure of rocky coastal cliffs despite much research on the myriad processes that erode rocky coastal cliffs accurately predicting the nature location and timing of coastline retreat remains challenging and is confounded by the apparently episodic nature of cliff failure the dominant drivers of coastal erosion marine and subaerial forcing are anticipated to increase in the future so understanding their present and combined efficacy is fundamental to improving predictions of coastline retreat we captured change using repeat laser scanning across 2 7 104 m2 of near vertical rock cliffs on the uk north sea coast over 7 yr to determine the controls on the rates patterns and mechanisms of erosion for the first time we document that progressive upward propagation of failure dictates the mode and defines the rate at which marine erosion of the toe can accrue retreat of coastline above this is a failure mechanism not conventionally considered in cliff stability models propagation of instability and failure operates at these sites at 10 yr time scales and is moderated by local rock mass strength and the time dependence of rock fracture we suggest that once initiated failure propagation can operate ostensibly independently to external environmental forcing and so may not be tightly coupled to prevailing subaerial and oceanographic conditions our observations apply to coasts of both uniform and complex lithology where failure geometry is defined by rock mass strength and structure and not intact rock strength alone and where retreat occurs via any mode other than full cliff collapse

erosional processes in the hard rock coastal cliffs at staithes north yorkshire the processes of change on near vertical coastal cliffs have been quantified using terrestrial photogrammetry and laser scanning the approach allows discrete rockfall geometry to be measured and source located in three dimensions this paper presents the analysis of an inventory of over 100000 discrete rockfalls recorded from the liassic coast at staithes north yorkshire uk where a rock face area of over 16000 m 2 has been monitored over a 20 month period the data obtained on three dimensional scar geometry and source position give an insight into rockfall characteristics from a range of rock types cliff heights and geometries multiple failure mechanisms such as overhang collapse constant spalling fragmentation and large scale coherent rockfalls have been observed and related to rock type controlled processes on the rock face the spatially referenced rockfall scar data are used to assess the influence of environmental controls on variable rock mass properties such as rock type structure and cliff geometry analysis of rockfall magnitude frequency reveals notable similarities between coastal rockfalls and inventories from non coastal environments the resolution of the monitoring data allows quantification of rockfalls down to volumes of 1 25 x 10 4 m 3 to be consistently sampled and measured this complete magnitude frequency relationship suggests that rather than evolving exclusively through isolated sporadic losses coastal cliff geomorphology reflects interconnected processes in which each rockfall is part of a continuum of change to the rock face further detailed assessment of the rock face reveals the control of the pre failure morphology on subsequent failure patterns for example the quantity of rock protrusion from the cliff is positively correlated with subsequent failure volume the continuum of activity and the controls on failure identified within these data suggest that the episodic behaviour of coastal cliffs previously assumed may have been overstated by coarser resolution monitoring data the findings improve our understanding of the evolution of coastal cliffs and highlight areas for further research into both cliff processes and the character of rock slope failures in general

strength of jointed rock masses jointed rock masses comprise interlocking angular par ticles or blocks of hard brittle material separated by discontinuity surfaces which may or may not be coated with weaker materials the strength of such rock masses depends on the strength of the intact pieces and on their freedom of movement which in turn depends on the number orientation spacing and shear strength of the discontinuities a complete understanding of this problem presents formidable theoretical and experi mental problems and hence simplifying assumptions are required in order to provide a reasonable basis for estimating the strength of jointed rock masses for engineering design purposes this paper summarizes some of the basic information upon which such simplifying assumptions can be made a simple empirical failure criterion is presented and its application in engineering design is illustrated by means of a number of practical examples des masses jointives de rochers comprennent des particules angulaires enchevetrees ou des

weathering effects on the strength and deformational behaviour of crystalline rocks under uniaxial compression state uniaxial compression tests were performed on different categories of weathering of three lithological units malanjkhand granite nagpur basalt and delhi quartzite occurring in central and northern parts of india the deformational behaviour is studied in terms of variation in tangent modulus et50 and initial modulus ei due to weathering the power relationship between uniaxial compressive strength c and et50 shows strong correspondence for weathering sequence of common rock types this relationship has been established by regression analysis and significant correlation parameter coefficient of determination r2 0 87 for crystalline rocks it is shown that there is a systematic decrease in stiffness ratio that is ratio of tangent modulus and uniaxial compressive strength with increased weathering state comparison of et50 and ei values has shown that et50 decreases more gradually than ei and reduction is more drastic for ei values with an increased degree of weathering in all the three rock types the mode of failure has been found to be influenced by weathering extent in rocks a brief account is given of the intrinsic characteristics of fresh and weathered rocks and mineralogical changes produced by weathering investigated quantitatively correlation drawn between the petrographical and mechanical indices has shown that mechanical properties are apparently dependent on the intrinsic characteristics of weathered rocks

late paleozoic depositional sequences are synchronous and worldwide more than fifty transgressive regressive depositional sequences are present in carboniferous and permian shallow marine successions on stable cratonic shelves worldwide these were synchronous depositional events resulting from eustatic sea level changes that generally ranged from 100 to 200 m each transgressive regressive sequence is correlatable using current fossil knowledge they average about 2 m y and range from 1 2 to 4 m y in length the presence within these strata of numerous synchronous unconformities of considerable duration and worldwide extent suggests that the fossil record is very incomplete and that we are studying a punctuated fossil record and not a punctuated evolution based on a highly irregular mutation rate these late paleozoic transgressive regressive depositional sequences facilitate correlations because depositional histories of a rock succession can support interpretations of faunal assemblages and faunal similarities in evaluating age relationships

an undulatory discontinuity surface on a gently inclined muddy ramp possible evidence of secondary helical flow from the geological record an unusual somewhat cryptic undulatory discontinuity has been recognized near the basal contact of the wanakah shale member of the middle devonian ludlowville formation in western new york it is in part marked by undulating diagenetic limestone beds and concretionary horizons but can be traced continuously by subtle surfaces of fossil and pyritic lags this surface marks the top of parallel elongate mud ridges trending approximately n s perpendicular to the inferred e w depositional strike of the appalachian basin in western new york these ridges are observed in the field as irregularly spaced mud swells which have up to 1 5 m of relief and vary from 30 to 50 m or more in width the intervening broad flat channel floors are characterized by dense concentrations of diminutive brachiopods with gastropods and styliolinids which are gradually replaced by thin styliolinid horizons with abundant pyrite nodules and pyritized burrows over the tops of the swells traceable shelly horizons are observed to pinch out over the swells suggesting a period of relatively undisturbed sediment filling following the formation of the channellized surface the interval of nearly barren shale below this irregular surface however contains concretionary horizons and rare styliolinid pavements which are themselves irregular possibly indicating a changing topography for this surface through time previous taphonomic and palaeoecological studies of the lower wanakah shale member have disclosed a well defined regressive transgressive cycle with more subtle superimposed subcycles the undulatory surface described here occurs within the early regressive part of this cycle and appears to record an accentuated regressive kick of a lower order subcycle the formation of this surface is therefore interpreted to be a consequence of regressive submarine erosion and sediment bypass together with redeposition from suspension the development of the channels and parallel longitudinal mud ridges was probably controlled by helical flow cells within offshore directed bottom currents they may be the first recorded instance of sedimentary furrows described from the geological record taphonomic and biofacies data indicate relative depths below average storm wave base suggesting that sediment winnowing and redeposition occurred at depths only rarely affected by the direct impact of storm wave agitation

controlled source audiomagnetotellurics in geothermal exploration theoretical and field tests indicate that the controlled source audiomagnetotelluric csamt method provides an efficient means of delineating the shallow resistivity pattern above a hydrothermal system utilizing a transmitter overcomes the main limitation of conventional audiomagnetotellurics variable and unreliable natural source fields reliable csamt measurements can be made with a simple scalar receiver our calculations for a half space show that the plane wave assumption is valid when the transmitter is more than 3 skin depths away in the broadside configuration and more than 5 skin depths away in the collinear configuration three dimensional 3 d numerical modeling results for a bipole source 5 skin depths away compare well with those for a plane wave source showing that the method is valid a csamt survey at the roosevelt hot springs geothermal area in utah produced apparent resistivity contour maps at four frequencies 32 98 977 and 5208 hz these maps show the same features as those of a

the effects of aqueous chemical environments on crack and hydraulic fracture propagation and morphologies the role of surface active aqueous environments in chemomechanical weakening of geologic materials is examined in light of the results of hydraulic fracture tests in sandstone calorimetric studies and crack propagation tests in synthetic quartz in hydraulic fracture tests mploying crab orchard sandstone it was found that the effective hydraulic fracture pressure was reduced over that attained with distilled water when 5 10 4 m aqueous solutions of dodecyl trimethyl ammonium bromide dtab were used as the hydraulic fracture medium the degree of branching of the fractures was also increased in the presence of the dtab solution previously reported crack propagation stress values in quartz exposed to distilled water and various dtab solutions displayed the same trend when examined in this study the cracks propagated in the presence of dtab solutions also displayed a greater degree of branching than those propagated in the presence of distilled water or the ambient atmosphere these results and results from calorimetric measurements of the heats of adsorption and desorption from quartz of distilled water and dtab are synthesized in a model relating the weakening and morphological effects to a reduction in the surface free energy of quartz due to adsorption of species from the chemical environment onto the surfaces of the quartz and sandstone

sea level curve for pennsylvanian eustatic marine transgressive regressive depositional cycles along midcontinent outcrop belt north america at least 55 cycles of marine inundation and withdrawal are recognized in the mid desmoinesian to mid virgilian midcontinent outcrop sequence in north america they range from widespread major cycles classic cyclothems with deep water facies extending across the northern shelf through intermediate cycles persisting as marine horizons across the shelf to minor cycles developed on the lower shelf or as parts of major cycles biostratigraphic differentiation of the cycles should establish interbasinal correlation on a scale fine enough to allow evaluation of differential tectonics and sedimentation sequential groupings of cycles are more irregular than proposed megacyclothems or mesothems but they may be obscured by the distinctness of the major cyclothems estimates of cycle periods range from about 40 to 120 x 10 sup 3 yr for the minor cycles up to about 235 to 400 x 10 sup 3 yr for the major cyclothems the range for all cycles corresponds well to the range of periods of earth s orbital parameters that constitute the milankovitch insolation theory for the pleistocene ice ages and it further supports gondwanan glacial control for the pennsylvanian cycles even though the dominant period of the major pennsylvanian cyclothems is up to four times longer than the dominant 100 000 yr period inmore the pleistocene the shapes of both curves display rapid marine transgression rapid melting of ice caps and slow interrupted regression slow buildup of ice caps which suggest similar linkages between the climatic effects of the orbital parameters and ice cap formation and melting at the two different scales widely separated in time 28 references 3 figures less

influence of rock mass strength on the erosion rate of alpine cliffs collapse of cliff faces by rockfall is a primary mode of bedrock erosion in alpine environments and exerts a first order control on the morphologic development of these landscapes in this work we investigate the influence of rock mass strength on the retreat rate of alpine cliffs to quantify rockwall competence we employed the slope mass rating smr geomechanical strength index a metric that combines numerous factors contributing to the strength of a rock mass the magnitude of cliff retreat was calculated by estimating the volume of talus at the toe of each rockwall and projecting that material back on to the cliff face while accounting for the loss of production area as talus buries the base of the wall selecting sites within basins swept clean by advancing last glacial maximum lgm glaciers allowed us to estimate the time period over which talus accumulation occurred i e the production time dividing the magnitude of normal cliff retreat by the production time we calculated recession rates for each site our study area included a portion of the sierra nevada between yosemite national park and lake tahoe rockwall recession rates determined for 40 alpine cliffs in this region range from 0 02 to 1 22 mm year with an average value of 0 28 mm year we found good correlation between rockwall recession rate and smr which is best characterized by an exponential decrease in erosion rate with increasing rock mass strength analysis of the individual components of the smr reveals that joint orientation with respect to the cliff face is the most important parameter affecting the rockwall erosion rate the complete smr score however best synthesizes the lithologic variables that contribute to the strength and erodibility of these rock slopes our data reveal no strong independent correlations between rockwall retreat rate and topographic attributes such as elevation aspect or slope angle copyright 2009 john wiley sons ltd

numerical modelling of combined erosion and weathering of slopes in weak rock due to various decay processes associated with weathering the stability of artificial slopes in weak rocks may be affected well within their envisaged engineering lifetime conceptually the decay following the initial stress release after excavation can be described as a process seeking equilibrium between weathering and erosion the extent to which such an equilibrium is actually reached influences the outcome of the weathering erosion decay process as well as the effects that the decay has on the geotechnical properties of the exposed rock mass and thus ultimately the stability of slopes affected by erosion and weathering this paper combines two conceptual models for erosion and weathering and derives a numerical model which predicts the resulting slope development this can help to predict the development of a slope profile excavated in a weak rock in time and can be extended with the addition of strength parameters to the weathering profile to enable prediction of slope stability as a function of time copyright 2011 john wiley sons ltd

time dependent drift degradation due to the progressive failure of rock bridges along discontinuities an important element of time dependent drift degradation is the progressive failure of intact segments along discontinuities referred to as rock bridges a fracture mechanics model is developed to simulate the time dependent failure of rock bridges along discontinuities the time dependence of the rock bridge failure process is modeled utilizing subcritical crack growth the rock bridges give an effective cohesion to the discontinuities and this cohesion is time dependent due to the time dependent failure of the rock bridges the resulting first order differential equation for joint cohesion is implemented into the udec distinct element numerical code to model time dependent drift degradation the model and its implementation into udec are validated using several simple examples including a direct shear test and a rigid block on a slope two time dependent drift degradation examples are then shown one with and one without thermal loading these examples used similar geometry material parameters and in situ stresses as for the proposed underground drifts for the storage of nuclear waste at yucca mountain both with and without thermal loading a large zone develops around the excavation where the joint cohesion and tensile strength drop to zero due to the failure of rock bridges this in turn results in an excavation that is significantly less stable than if time dependence was not included the results demonstrate the importance of time dependence on the stability of underground excavations in hard rock

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

punctuated aggradational cycles implications for stratigraphic analysis application of the hypothesis of punctuated aggradational cycles pacs a model of episodic stratigraphic accumulation has yielded results fundamentally in conflict with those predicted and generated by gradualistic models the assumption that stratigraphic accumulation is controlled principally by rapid small scale base level fluctuations in the milankovitch band leads to the adoption of the pac a thin time stratigraphic unit as the fundamental unit of stratigraphic description and interpretation the thicker generally diachronous formation is inadequate for stratigraphic analysis because it is an artifact of stratigraphic gradualism correlation of stratigraphic sections is accomplished by matching patterns of facies change particularly the abrupt changes at the synchronous surfaces that mark pac boundaries this kind of physical event correlation is far more accurate than traditional biostratigraphic methods focus on synchronous pac boundaries separating environmentally disjunct facies reveals discontinuities that preclude application of walther s law across those surfaces when viewed from this episodic perspective the manlius formation of the helderberg group in new york state becomes a highly ordered set of time stratigraphic cycles rather than a disordered mosaic of facies representing short term autogenic processes in a single nearshore environment not only was manlius deposition episodic with no gradual upward deepening as is predicted by stratigraphic gradualism but also the manlius coeymans formational boundary is interpreted as a small scale unconformity rather than a paleoenvironmental boundary created by gradual transgression each of these interpretations is the direct result of assuming and applying a model of episodic stratigraphic accumulation

onshore migration of a deep water brachiopod fauna from the lower ordovician tonggao formation jiangnan slope southeastern guizhou province south chinathis article is one of a series of papers published in this special issue on the theme the dynamic reef and shelly communities of the paleozoic this special is in honour of our colleague and friend paul copper brachiopods from the lower tonggao formation floian late early ordovician of sandu southeastern guizhou province represent a deep water benthic shelly fauna from the jiangnan slope facies of the south china paleoplate the fauna contains 16 brachiopod taxa with orthides lingulates and pentamerides being the common groups concurrent graptolites confine the brachiopod fauna to the tetragraptus approximatus and the acrograptus filiformis biozones early floian the first appearance datum fad of several brachiopod genera such as paralenorthis protoskenidioides and nereidella in the sandu slope facies is one or two graptolitic biozones lower than their fad in shallower water facies on the yangtze platform later in the late floian these genera became major components of the sinorthis fauna that flourished over much of the yangtze platform suggesting a migration of the benthic shelly fauna from slope to platform facies during the floian radiation in south china compared to the platform fauna

a non destructive tool for detecting changes in the hardness of engineering materials application of the equotip durometer in the coastal zone non destructive tools capable of measuring the condition and geomechanical properties of construction materials through time are of considerable value in engineering here the ability of the equotip durometer proceq type d to detect changes in the hardness of concrete and rock exposed to marine conditions was tested results indicated a progressive loss of hardness for limestone while concrete hardness increased granite showed no significant change our results relate to alteration of the materials primarily via chemical and biological weathering the equotip is sensitive enough to detect subtle changes in the condition of construction materials over relatively short periods of time

development of progressive landslide failure in cohesive materials the development of progressive failure in slopes is a poorly understood process and relatively few advances in terms of the mechanics of the development of failure have been made since 1967 however advances in the understanding of the development of fractures in brittle materials provide new insights into landslide mechanics in addition the link between the deformation mechanism and movement type allows interpretation of displacement records to determine the mechanisms acting within a slope this paper utilizes these insights into deformation processes combined with reinflation stress path triaxial experiments to propose a new model for the development of a progressive first time failure within a slope this model is able to explain the development of failure when the factor of safety is greater than unity the existence of saito linearity a linear trend when the reciprocal of velocity prior to failure is plotted against time during tertiary creep and the development of failures during periods of apparently increasing normal effective stress

shallowing upward sequences in purbeckian peritidal carbonates lowermost cretaceous swiss and french jura mountains purbeckian carbonates in the swiss and french jura goldberg formation lower berriasian comprise shallow subtidal intertidal supratidal low energy high energy marine brackish freshwater and hypersaline facies these facies are arranged in small 0 2 1 5 m thick sequences which display a dominant shallowing upward component and which form the fundamental units of the highly structured purbeckian sedimentary record six types of small scale sequences can be recognized a intertidal to supratidal overprinting of shallow lagoonal facies b algal marsh sequence with frequent dolomitization c sabkha sequence often associated with collapse breccia d tidal flat sequence with desiccation features e lacustrine sequence f terrestrial overprinting of subtidal or intertidal facies episodic event deposits such as tempestites are superimposed thin transgressive beds which rework elements of the underlying facies are frequently found at the base of the sequences green marls and black pebbles are common at the top and indicate long subaerial exposure the sequences are often incomplete as subtidal facies may be absent or their upper part can be eroded lateral facies changes are common which is due to the very shallow and partly emergent purbeckian platform where various depositional environments were juxtaposed however many sequence boundaries are well developed and can be correlated over large parts of the study area the purbeckian shallowing upward sequences were generated by climatically controlled sea level changes autocyclic processes occurred locally but were overprinted by drops of sea level affecting the entire platform the small scale sequences are most probably related to the 20 000 year cycle of the precession of the equinoxes larger sequences with usually well developed emersion surfaces are attributed to the 100 000 and 400 000 year eccentricity cycles of the earth s orbit identification and correlation of sequence boundaries makes it possible to set up a framework of isochronous surfaces which often cut across facies boundaries and thus to interpret in detail the palaeogeographic sedimentological and diagenetic evolution of the purbeckian peritidal carbonate environments

the role of rock surface hardness and internal moisture in tafoni development in sandstone the development of cavernous weathering features such as tafoni remains poorly understood in particular the roles played by internal moisture and case hardening remain unclear in this study electric resistivity tomography ert has been used to map moisture distribution within inner walls of tafoni developed in sandstone and an equotip device used to measure rock surface hardness as a proxy measure of the degree of weathering and case hardening seven large tafoni in the golden gate highlands national park south africa varying in size and degree of development have been monitored a dynamic relationship between surface hardness degree of weathering and internal moisture regimes has been found we propose a new conceptual model which illustrates the complex interaction between case hardening and internal moisture and suggests a new direction for cavernous weathering research copyright 2011 john wiley sons ltd

a depositional model for storm and tide influenced prograding siliciclastic shorelines from the middle devonian of the central appalachian foreland basin usa a stratigraphic motif observed in many foreland basins is the development of basinward tapering siliciclastic wedges characterized by various scales of depositional cycles the middle devonian givetian mahantango formation in the central appalachian foreland basin is such an example it consists of both small and large scale thickening and coarsening upward cycles the small scale cycles are typically less than 10 m thick whereas larger scale cycles are generally a few tens of metres thick and commonly contain several of the smaller scale cycles outcrop based facies analyses indicate that the depositional cyclicity resulted from episodic progradation of a regionally straight tide dominated shoreline onto a storm dominated shallow marine shelf the depositional model for this ancient shallow marine system consists of a vertical facies succession in which storm dominated offshore marine mudstone and fine sandstone pass gradationally upward into storm dominated nearshore marine shelf and shoreface sandstone overlain by in proximal sections tide dominated shoreline sandstone pebbly sandstone and mudstone transgressively reworked lag deposits cap most of the thickening and coarsening upward packets in this model coarse grained rocks rather than implying basinward shifts of facies are a consanguineous part of the stacked shoaling cycles lateral facies relationships show that the dominance of storm vs tide generated sedimentary features is simply a function of palaeogeographical position within the basin proximal sections contain tidally influenced sedimentary features whereas more distal sections only display evidence for storm influenced deposition these results suggest caution when inferring palaeoceanographic conditions from sedimentological datasets that do not contain preserved examples of palaeoshorelines

a comparison of em induction and gpr methods in areas of karst abstract electromagnetic em induction and ground penetrating radar gpr methods have been used extensively in areas of karst to detect and delineate major structural and solution features and to improve site assessments these methods do not work equally well in all soils and the amount of practical information derived from surveys has varied the choice of the most appropriate method often depends on the electrical properties of the soils this study characterized the use of gpr and em at two contrasting sites in florida and pennsylvania the florida site is underlain by relatively thick layers of electrically resistive sands overlying loamy marine sediments and limestone bedrock gpr was effectively used to determine the thickness of surface layers and the locations of buried solution features multiple contrasting soil horizons and layers weakened relationships and created non unique interpretations for em the pennsylvania site is was underlain by clayey residuum and limestone bedrock the clayey residuum is opaque to gpr and observation depths are severely restricted em induction effectively characterized the depths to bedrock within the pennsylvania site the integrated use of both methods supported by commensurate ground truth verifications helped to increase confidence in interpretations

controls on rock weathering rates by reaction induced hierarchical fracturing abstract weathering of rocks takes place through complex processes involving an intimate coupling between mechanical disintegration of the rocks and interactions between the exposed rock surface the hydrosphere and the biosphere it is still poorly understood how this coupling affects weathering rates and patterns produced by weathering here we show that the observed spheroidal weathering patterns in basaltic intrusions dolerites in the karoo basin in south africa are created through volume expanding reactions which set up stresses that not only lead to spalling of spheroidal layers of rock but also drive a large scale hierarchical fracturing process by which the dolerite is continuously undergoing domain division the fracture processes generates new reactive surface area in a self accelerating manner thus providing a first order control on the total weathering rate

air circulation in deep fractures and the temperature field of an alpine rock slope the subsurface temperature field of a rock slope is a key variable influencing both bedrock fracturing and slope stability however significant unknowns remain relating to the effect of air and water fracture flow which can rapidly transmit temperature changes to appreciable depths in this work we analyze a unique set of temperature measurements from an alpine rock slope at 2400 m a s l in southern switzerland the monitored area encompasses part of an active slope instability above the village of randa vs and is traversed by a network of open cracks some of which have been traced to 80 m depth we first describe distributed temperature measurements and borehole profiles highlighting deep steady temperatures and different transient effects and then use these data to approximate the conductive temperature field at the site in a second step we analyze the impact of air and water circulation in deep open fractures on the subsurface thermal field on multiple visits to the study site in winter we consistently noted the presence of warm air vents in the snowpack following the trace of deep tension cracks measurements showed that venting air changed temperature gradually from 3 to 2 c between december and may which is similar to the rock temperature at around 50 m depth comparison with ambient air temperature suggests that winter conditions favor buoyancy driven convective air flow in these fractures which acts to cool the deep subsurface as the rock gives up heat to incoming air the potential impact of this process on the local thermal field is revealed by a disturbed temperature profile in one borehole and transient signals observed at depths well below the thermal active layer seasonal water infiltration during snowmelt appears to have little impact on the temperature field in the monitored area copyright 2011 john wiley sons ltd

complex weathering in drylands implications of stress history for rock debris breakdown and sediment release abstract weathering studies have often sought to explain features in terms of a prevailing set of environmental conditions however it is clear that in most present day hot desert regions the surface rock debris has been exposed to a range of weathering environments and processes these different weathering conditions can arise in two ways either from the effects of long term climate change acting on debris that remains relatively static within the landscape or through the spatial relocation of debris from high to low altitude consequently each fragment of rock may contain a unique weathering related legacy of damage and alteration a legacy that may greatly influence its response to present day weathering activity experiments are described in which blocks of limestone sandstone granite and basalt are given stress histories by subjecting them to varying numbers of heating and freezing cycles as a form of pre treatment these imposed stress histories act as proxies for a weathering history some blocks were used in a laboratory salt weathering simulation study while others underwent a 2 year field exposure trial at high mid and low altitude sites in death valley california weight loss and ultrasonic pulse velocity measurements suggest that blocks with stress histories deteriorate more rapidly than unstressed samples of the same rock type exposed to the same environmental conditions laboratory data also indicate that the result of imposing a known weathering history on samples by pre stressing them is an increase in the amount of fine sediment released during salt weathering over a given period of time in comparison to unstressed samples

taphonomy and depositional dynamics of devonian shell rich mudstones abstract fossil preservation e g articulation of multi element skeletons provides important insights into depositional dynamics detailed taphonomic analysis of marine mudstones and associated shell beds from the middle devonian of western new york indicates that these beds record primarily episodic sediment deposition of short duration we propose a storm winnowing mud blanketing model to explain the variety of shell and mudstone beds observed and to explain apparent onshore offshore gradients of shell bed characteristics shell beds themselves appear to have accumulated during relatively long spans of time ranging up to perhaps thousands of years most are internally complex and exhibit evidence for multiple events of burial and exhumation by winnowing shell accumulation facilitated colonization of the seafloor by hard substrate encrusting organisms these contributed to increasingly complex communities that were ultimately destroyed and permanently blanketed by thick mud layers the sparsely fossiliferous mudstones which compose up to 85 of the hamilton stratigraphic section mainly record very abrupt inputs of sediment in some instances taphonomy of enclosed fossils indicates deposition of layers up to several centimeters thick prior to compaction within hours to a few days in turn some sequences of shell and mudstone beds were deposited within the life span of single colonial organisms and thus also record only relatively short spans of time overall this reinforces our conclusions that most time in mudstone sequences must be represented by discontinuities at sharp surfaces or thin condensed beds that bound more or less continuous bundles of shell and mudstone beds again these often subtle discontinuities can be recognized on the basis of taphonomic criteria many complex shell beds as well as simple shell beds can be traced along depositional strike for tens of kilometers condensed shell beds only a few centimeters thick can commonly be correlated for 100 to 200 km along and across depositional strike the correlatable nature of shell beds apparently reflects the temporal contrast between these beds and enclosing muds on a regional scale shell beds represent integrated accumulations that were deposited over spans of tens to thousands of years conversely the mud layers that blanketed and terminated shell bed accumulations may represent very rapid depositional events spanning hours to days which are locally isochronous thus the study of taphonomy of shell beds reveals a good deal of detail about their depositional history these studies imply that the stratigraphic record is even more episodic and discotinuous than commonly recognized episodic deposition implies that while the stratigraphic record of epeiric seas may be adequate for examining details of community succession and paleontology it probably can not generally be used for microevolutionary studies other than examination of patterns of stasis

results of a controlled source audiofrequency magnetotelluric survey at the puhimau thermal area kilauea volcano hawaii the puhimau thermal area in the volcanoes national park hawaii has attracted interest because it represents an area with anomalously high heat flow and the heat source may be a shallow magma body at puhimau a variety of geophysical data including heat flow measurements have been acquired the self potential data suggest that the heat source is a result of a magma intrusion which plunges steeply northward the heat flow data can be explained in terms of a shallow relatively thick magma intrusion with a solidification rate sufficient to supply the surficial heat flow for the period of time since the appearance of the thermal area in 1936 in february of 1984 we performed a controlled source audiofrequency magnetotelluric csamt electromagnetic geophysical survey at the puhimau thermal area to investigate the electrical nature of the thermal anomaly and estimate the depth to any hot water and or remaining molten magma the csamt survey consisted of several lines of stations where two orthogonal prima

linking weathering and rock slope instability non linear perspectives weathering is linked complexly to the erosion and evolution of rock slopes weathering influences both the strength of rock slopes and the stresses that act upon them while weathering has often been portrayed in an over simplified way by those studying rock slope instability in reality it consists of multiple processes acting over different spatial and temporal scales with many complex inter linkages through a demonstration of the sources of non linearities in rock slope weathering systems and their implications for rock slope instability this paper proposes five key linkages worthy of further study copyright 2012 john wiley sons ltd

the application of high resolution 3d seismic acquisition techniques for carbonate reservoir characterization in china this paper describes major challenges to seismic acquisition in china s tarim basin figure 1 and how high resolution 3d seismic surveys can improve reservoir imaging in this area

are microseismic ground displacements a significant geomorphic agent this paper considers the role that microseismic ground displacements may play in fracturing rock via cyclic loading and subcritical crack growth using a coastal rock cliff as a case study we firstly undertake a literature review to define the spatial locations that may be prone to microseismic damage it is suggested that microseismic weakening of rock can only occur in damage accumulation zones of limited spatial extent stress concentrations resulting from cliff height slope angle and surface morphology may nucleate and propagate a sufficiently dense population of microcracks that can then be exploited by microseismic cyclic loading we subsequently examine a 32 day microseismic dataset obtained from a coastal cliff top location at staithes uk the dataset demonstrates that microseismic ground displacements display low peak amplitudes that are punctuated by periods of greater displacement during storm conditions microseismic displacements generally display limited preferential directivity though we observe rarely occurring sustained ground motions with a cliff normal component during storm events high magnitude displacements and infrequently experienced ground motion directions may be more damaging than the more frequently occurring reduced magnitude displacements characteristic of periods of relative quiescence as high magnitude low frequency events exceed and then increase the damage threshold these extremes may also render intervening reduced magnitude microseismic displacements ineffective in terms of damage accumulation as a result of crack tip blunting and the generation of residual compressive stresses that close microcracks we contend that damage resulting from microseismic ground motion may be episodic rather than being continuous and in quasi proportional and cumulative response to environmental forcing a conceptual model is proposed that describes when and where microseismic ground motions can operate effectively we hypothesise that there are significant spatial and temporal limitations on effective microseismic damage accumulation such that the net efficacy of microseismic ground motions in preparing rock for fracture and hence in enhancing erosion may be considerably lower than previously suggested in locations where high magnitude displacements punctuate standard displacement conditions determining and measuring the exact effects of microseismic ground displacement on damage accumulation and as a trigger to macro scale fracture in the field is not currently possible though our model remains consistent with field observations and conceptual models of controls on rockfall activity

bedrock fracturing threshold hillslopes and limits to the magnitude of bedrock landslides abstract bedrock fracturing and rock strength are widely believed to influence landscape morphology and erosional resistance yet understanding of the quantitative relationship between rock mass strength and landscape evolution remains limited here we present a new application of seismic refraction surveys that uses variations in seismic velocity to interpret differences in bedrock fracture density with depth we use a comparative study of fiordland and the western southern alps of new zealand to examine how differences in rock type and bedrock fracturing influence landscape morphology and landslide response to rock uplift in both regions slopes appear invariant with differential rock uplift rates and slope distributions reveal modal hillslope angles of 32 the majority of landslides initiate on slopes steeper than the modal hillslope angle however landslide magnitude frequency distributions reveal order of magnitude differences between the regions with fiordland experiencing considerably smaller and less frequent landsliding events landslide driven denudation rates of 9 mm yr in the western southern alps and between 0 1 and 0 3 mm yr in fiordland approximate estimates of long term rock uplift rates for each region the invariance of hillslope angles near normal slope distributions predominance of landslide initiation on slopes steeper than modal values and the apparent balance between rates of uplift and landslide driven erosion suggest that hillslopes in both regions are at threshold angles their similar modal slopes further suggest that both ranges are characterized by equivalent rock mass strength despite striking differences in lithology additionally our seismic analysis reveals nearly identical surface p wave velocities the unexpected equivalence of both modal slopes and surface velocities between these lithologically distinct ranges is attributed to contrasting degrees of surface fracturing that have differentially affected the intact rock properties such that they now yield equivalent surface velocities and hillslope scale strengths given that surface fractures help regulate threshold angles by modulating hillslope strength we propose that shallow seismic velocities may provide a quantitative proxy for rock mass strength we define two contrasting fracture and landsliding environments in fiordland dense geomorphic fracturing that is focused within the shallow subsurface appears to limit the depth and magnitude of most bedrock landslides conversely in the western southern alps tectonic forces produce pervasive fracturing with depth that results in larger and deeper landslides our data suggest that bedrock fracturing at the earth s surface modulates threshold hillslope angles whereas the depth of bedrock fracturing influences the magnitude and frequency of landslide response to tectonic rock uplift

sandstone landforms shaped by negative feedback between stress and erosion the formation and preservation of sandstone landforms such as pillars and arches is enigmatic experiments and numerical modelling show that load bearing material weathers more slowly and thus the internal stress field can shape and stabilize sandstone landforms

correlation of carboniferous strata using a hierarchy of transgressive regressive units carboniferous strata can be described interpreted and correlated using six scales of allocyclic transgressive regressive t r units these t r units are inferred to be the net result of deposition during cycles of sea level change all pennsylvanian and lower permian strata constitute one second order t r unit or synthem the pennsylvanian system contains third fourth fifth and sixth order t r units that can be correlated across both marine and nonmarine facies in the appalachian basin this permits differentiation of allocyclic t r units from autocyclic t r units or fluvial autocyclic units the hierarchical approach is also useful for predicting the location of marine horizons coals claystones and various types of stratigraphic breaks a hierarchical scheme of allocyclic t r units could be combined with biostratigraphic radiometric and magnetostratigraphic data to form a practical chronostratigraphic framework for the carboniferous

patterns of precursory rockfall prior to slope failure in this paper we examine data generated using high resolution three dimensional laser scanning monitoring of coastal rock cliffs these data are used to identify spatial and temporal patterns in rockfall activity behavior prior to slope failure analysis of the data suggests that given sufficient measurement precision precursory behavior here manifest as the rate of rockfall activity prior to failure can be detected measured and monitored environmental conditions appear to have a diminishing influence on the occurrence of increasingly large slope failures the monitoring data implies a time dependent sequence in the occurrence of smaller rockfalls in the period leading to the largest failures recorded this behavior is attributed to the mechanisms of strain accumulation in the rock mass resulting from brittle failure of the slope the implication is that combining these data with models of failure mechanisms may allow failure time to be forecast from wide area monitoring of precursory behavior these findings have implications for the management of potentially unstable slopes the understanding of slope failure mechanisms and the generation of a new type of slope failure warning systems

architecture and formation of transgressive regressive cycles in marginal marine strata of the john henry member straight cliffs formation upper cretaceous of southern utah usa marginal marine deposits of the john henry member upper cretaceous straight cliffs formation were deposited within a moderately high accommodation and high sediment supply setting that facilitated preservation of both transgressive and regressive marginal marine deposits complete transgressive regressive cycles comprising barrier island lagoonal transgressive deposits interfingered with regressive shoreface facies are distinguished based on their internal facies architecture and bounding surfaces two main types of boundaries occur between the transgressive and regressive portions of each cycle i surfaces that record the maximum regression and onset of transgression bounding surface a and ii surfaces that place deeper facies on top of shallower facies bounding surface b the base of a transgressive facies bounding surface a is defined by a process change from wave dominated to tide dominated facies or a coaly shelly interval indicating a shift from a regressive to a transgressive regime the surface recording such a process change can be erosional or non erosive and conformable a shift to deeper facies occurs at the base of regressive shoreface deposits along both flooding surfaces and wave ravinement surfaces bounding surface b these two main bounding surfaces and their subtypes generate three distinct transgressive regressive cycle architectures i tabular shoaling upward marine parasequences that are bounded by flooding surfaces ii transgressive and regressive unit wedges that thin basinward and landward respectively and iii tabular transgressive lagoonal shales with intervening regressive coaly intervals the preservation of transgressive facies under moderately high accommodation and sediment supply conditions greatly affects stratigraphic architecture of transgressive regressive cycles acknowledging variation in transgressive regressive cycles and recognizing transgressive successions that correlate to flooding surfaces basinward are both critical to achieving an accurate sequence stratigraphic interpretation of high frequency cycles

controls on the geotechnical response of sedimentary rocks to weathering weathering reduces the strength of rocks and so is a key control on the stability of rock slopes recent research suggests that the geotechnical response of rocks to weathering varies with ambient stress conditions resulting from overburden loading and or stress concentrations driven by near surface topography in addition the stress history experienced by the rock can influence the degree to which current weathering processes cause rock breakdown to address the combined effect of these potential controls we conducted a set of weathering experiments on two sedimentary lithologies in laboratory and field conditions we firstly defined the baseline geotechnical behaviour of each lithology characterising surface hardness and stress strain behaviour in unconfined compression weathering significantly reduced intact rock strength but this was not evident in measurements of surface hardness the ambient compressive stress applied to samples throughout the experiments did not cause any observable differences in the geotechnical behaviour of the samples we created a stress history effect in sub sets of samples by generating a population of microcracks that could be exploited by weathering processes we also geometrically modified groups of samples to cause near surface stress concentrations that may allow greater weathering efficacy however even these pronounced sample modifications resulted in insignificant changes in geotechnical behaviour when compared to unmodified samples the observed reduction in rock strength changed the nature of failure of the samples which developed post peak strength and underwent multiple stages of brittle failure although weakened these samples could sustain greater stress and strain following exceedance of peak strength on this basis the multi stage failure style exhibited by weaker weathered rock may permit smaller magnitude higher frequency events to trigger fracture through intact rock bridges as well as influencing the characteristics of pre failure deformation these findings are consistent with patterns of behaviour observed in field monitoring results

audiomagnetotelluric characterization of range front faults snake range nevada two controlled source audio magnetotelluric csamt profiles were collected on the eastern flank of the snake range in eastern nevada across geologically complex terrain to investigate the suspected presence of faults along the range front the location of the range bounding faults is not easily determined on geologic grounds because of the presence of extensive young sedimentary cover and overall geologic complexity characterization of the presence location and structural style of the range front faults is critical to assessment of connectivity of groundwater aquifers near the mountain front and in adjacent alluvial basins a total of 48 csamt soundings were recorded along two lines that were chosen to maximize subsurface geologic information two generations of faults were interpreted based on the csamt data an older low angle fault that is cut by a younger more steeply dipping fault lack of deep boreholes in the region required that the subsurface interpretation rely on analogy from surface outcrops within and adjacent to the study area the success of the csamt method as applied in this study hinged on near ideal collection conditions the relatively high contrast in electrical resistivity provided by the rock types involved and well developed geologic conceptual models of the region

mapping chromite deposits with audio magnetotellurics in the luobusa ophiolite of southern tibet the exploration of podiform chromites in the indus yarlong zangbo suture zone of southern tibet has proved difficult in recent decades because most known deposits pinch out and then reappear in the same direction a number of ground based geophysical approaches including gravity magnetic and controlled source audio frequency magnetotelluric methods have been applied to explore for these chromite deposits but have mostly failed to delineate prospective areas we present a successful podiform chromite exploration case history that is based on audio magnetotellurics amt more than 8 000 amt stations were utilized in this study within a 10 km2 area of the ophiolite belt line separations were 80 m or 40 m and station separation was 20 m we implemented bostick conversion and non linear conjugate gradient inversions were implemented for data interpretation while two dimensional 2d resistivity sections and three dimensional 3d resistivity imaging were used to elucidate the inner structure and distribu

mapping deeply buried karst cavities using controlled source audio magnetotellurics a case history of a tunnel investigation in southwest china abstractkarst cavity mapping is attracting great interest from engineering geologists because of its relation to the dangerous geohazards faced during engineering construction ground based geophysical methods still face challenges in karst mapping and concealed karst cavities potentially pose threats to tunnel construction in southwest china given the significant contrast in electrical resistivity between karst cavities and their host rocks geoelectrical methods are widely used for mapping these cavities we have developed a successful case history of mapping karst cavities on a planned railway route using controlled source audio magnetotellurics csamt scalar csamt with frequencies ranging from 0 5 to 8192 hz was used for field data acquisition a full frequency domain apparent resistivity correction method was used for near field corrections electromagnetic array profiling emap filtering was used for topographic and static shift corrections and the bostick conversion was used for data interp

progressive failure of sheeted rock slopes the 2009 2010 rhombus wall rock falls in yosemite valley california usa progressive rock fall failures in natural rock slopes are common in many environments but often elude detailed quantitative documentation and analysis here we present high resolution photography video and laser scanning data that document spatial and temporal patterns of a 15 month long sequence of at least 14 rock falls from the rhombus wall a sheeted granitic cliff in yosemite valley california the rock fall sequence began on 26 august 2009 with a small failure at the tip of an overhanging rock slab several hours later a series of five rock falls totaling 736 m3 progressed upward along a sheeting joint behind the overhanging slab over the next 3 weeks audible cracking occurred on the rhombus wall suggesting crack propagation while visual monitoring revealed opening of a sheeting joint adjacent to the previous failure surface on 14 september 2009 a 110 m3 slab detached along this sheeting joint additional rock falls between 30 august and 20 november 2010 totaling 187 m3 radiated outward from the initial failure area along cliff sub parallel sheeting joints we suggest that these progressive failures might have been related to stress redistributions accompanying propagation of sheeting joints behind the cliff face mechanical analyses indicate that tensile stresses should occur perpendicular to the cliff face and open sheeting joints and that sheeting joints should propagate parallel to a cliff face from areas of stress concentrations the analyses also account for how sheeting joints can propagate to lengths many times greater than their depths behind cliff faces we posit that as a region of failure spreads across a cliff face stress concentrations along its margin will spread with it promoting further crack propagation and rock falls published in 2012 this article is a us government work and is in the public domain in the usa

influence of daily surface temperature fluctuations on rock slope stability case study of the rochers de valabres slope france the present paper describes a rockfall that has affected the rochers de valabres slope france s southern alps region and discusses one possible mechanism for the occurrence of this rockfall along with the potential for future ones in the absence of an obvious explanatory trigger factor we set out to examine whether natural daily surface temperature changes could have played a role in this event in particular it is suspected that these slight yet repeated perturbations may be a preparatory factor for rockfalls with a day to day cumulative effect a numerical model strengthens this hypothesis by showing that thermally induced deformations can be sufficient to cause the gradual downward creep of a rock block located in an awkward position to investigate this notion more thoroughly a currently vulnerable part of the rochers de valabres slope has been instrumented with a high precision geodetic monitoring system total station it is believed that this device is able to capture thermally induced movements if specific precautions are taken the instrumented rock volume is used as a test site in the aim of better understanding the consequences of surface temperature changes on slope stability measured data with a precision level never before achieved on rock slopes are compared herein with numerical modelling results the initial conclusions of the long term study we are conducting indicate that surface temperature changes play an important while not easily quantifiable role in preparing rockfalls

carbonate platform lagoon and delta high frequency cycles from the carnian of lombardy southern alps italy abstract the early and middle carnian succession of the bergamasc alps southern alps italy was deposited in three different environments a deltaic depositional system passing seaward to a lagoon or bay and then to a carbonate platform the corresponding lithofacies sandstones and siltstones shales and limestones are organized in high frequency cycles fining upward trends are typical of the subaerial delta plain cycles and shallowing upward trends are widespread in the lagoon and platform cycles the genesis of the lagoonal and carbonate platform cycles is possibly accounted for by sea level changes mainly controlled by small scale eustatic oscillations sea level changes are interpreted as exerting a major control also in the development of the deltaic cycles

crinoid biofacies in upper carboniferous cyclothems midcontinent north america faunal tracking and the role of regional processes in biofacies recurrence abstract coordinated stasis is a pattern of long term multispecies evolutionary and ecological stability bounded by rapid turnover events one class of models proposed to explain the paleoecological pattern of biofacies stability typified by ecological locking states that biotas within habitats become integrated into ecological units that through population and community level processes rebound and persist through short term disturbances this high frequency community resilience allows the units to persist through geologic time tracking their preferred habitats during transgressions and regressions because species are tightly woven into the fabric of the ecosystem there is little opportunity for speciation this also buffers them against extinction this ecological locking by ecosystem homeostatic processes produces long intervals of regionally stable biofacies in the fossil record in these models the primary structuring mechanisms are at the local community level controlled by species autecology species interactions and local disturbance regime an opposing class of models states that species are fundamentally independent and that species interactions are not strong nor spatio temporally persistent enough to forge communities into integrated units with long term persistence community recurrence would be expected as long as the various habitat types recur in time and space species autecologies remain stable the pool of available species remains intact and the recruitment of species into local habitats is not interrupted the focus of these models is dominantly at the regional level controlled by biogeographic history and dispersal among as well as within communities the results of this study of crinoids from the upper carboniferous lansing group of midcontinent north america show that they are distributed among five recurrent paleocommunity types or biofacies which are generally arrayed along an onshore offshore gradient two of these biofacies are restricted to the offshore dysaerobic horizons of the most extensive cyclothem in the group the other three biofacies recur consistently among the cycles however this repeated pattern includes a regionally distributed offshore biofacies unique to late transgressive deposits that is not found in analogous regressive deposits while the distribution of the two shoreward biofacies is consistent with faunal tracking the recurrence of a biofacies unique to late transgressive horizons is not consistent with an integrated paleocommunity that tracks shifting habitats through transgression and regression these results favor the alternative models namely that biofacies develop in place via dispersal from a persistent species pool in response to prevailing environmental conditions the recurrence of apparently ephemeral biofacies through time underscores the importance of regional processes in controlling local paleocommunity composition the establishment of refuges or source populations during environmental bottlenecks i e lowstands is critical to maintaining the regional species pool through time for continued recruitment into local sink paleocommunities during more amenable times i e highstands metapopulation dynamics among habitats are equally important in maintaining species within a region through time conflicting observations of stochastic individualistic and deterministic integrated behaviors of the same ecological systems probably result from differences in the scales of analyses and therefore the processes being studied

rockfall activity from an alpine cliff during thawing periods abstract rockfall activity during thawing periods was investigated by collecting rockfall debris fallen on the snow covered talus slope in a cirque in the japanese alps near surface rock temperature was also monitored on the cirque wall maximum rockfall activity occurs on average about 10 days after the meltout of the cirque wall the intensive activity is rarely associated with precipitation events or diurnal frost cycles on the rockface a thermal conduction model suggests that rockfalls at this site occur most frequently when the seasonal thawing front penetrates to a depth of about 1 m in the bedrock while the freeze thaw penetration controls the maximum dimensions of detachable rock mass joint spacing on the rockface affects the size distribution of rockfall debris boulder falls resulting from seasonal frost weathering are considered to be the most important process responsible for the contemporary modification of the cirque wall the rockfall volume during a thawing period is usually 1 3 m3 which is equivalent to the rate of cirque wall retreat of the order of 0 01 mm year 1 however big boulder falls that occur once per decade can increase the retreat rate significantly

sequence stratigraphy and a revised sea level curve for the middle devonian of eastern north america abstract the well exposed middle devonian rocks of the appalachian foreland basin onondaga formation hamilton group tully formation and the genesee group of new york state preserve one of the most detailed records of high order sea level oscillation cycles for this time period in the world detailed examination of coeval units in distal areas of the appalachian basin as well as portions of the michigan and illinois basins has revealed that the pattern of high order sea level oscillations documented in the new york pennsylvania section can be positively identified in all areas of eastern north america where coeval units are preserved the persistence of the pattern of high order sea level cycles across such a wide geographic area suggests that these cycles are allocyclic in nature with primary control on deposition being eustatic sea level oscillation as opposed to autocylic controls such as sediment supply which would be more local in their manifestation there is strong evidence from studies of cyclicity and spectral analysis that these cycles are also related to milankovitch orbital variations with the short and long term eccentricity cycles 100 kyr and 405 kyr being the dominant oscillations in many settings relative sea level oscillations of tens of meters are likely and raise considerable issues about the driving mechanism given that the middle devonian appears to record a greenhouse phase of phanerozoic history these new correlations lend strong support to a revised high resolution sea level oscillation curve for the middle devonian for the eastern portion of north america recognized third order sequences are eif 1 lower onondaga formation eif 2 upper onondaga and union springs formations eif giv oatka creek formation giv 1 skaneateles giv 2 ludlowville giv 3 lower moscow giv 4 upper moscow lower tully and giv 5 middle tully geneseo formations thus in contrast with the widely cited eustatic curve of johnson et al 1985 which recognizes just one major transgressive regressive t r cycle in the early mid givetian if prior to the major late givetian taghanic unconformity iia upper tully geneseo shale we recognize four t r cycles if restricted ig ih and ii we surmise that third order sequences record eustatic sea level fluctuations of tens of meters with periodicities of 0 8 2 myr while their medial scale fourth order subdivisions record lesser variations primarily of 405 kyr duration long term eccentricity this high resolution record of sea level change provides strong evidence for high order eustatic cycles with probable milankovitch periodicities despite the fact that no direct evidence for middle devonian glacial sediments has been found to date

giant landslides topography and erosion abstract distributions of slope angles in tectonically active mountain belts point to the development of threshold conditions where hillslopes attain a critical inclination or height at which they fail readily because of limitations in material strength it has been proposed that hillslopes adjust to rapid uplift and bedrock incision through an increase in the rate of relief limiting landsliding rather than gradual slope steepening here we test this concept by investigating the relationship between mean local relief h which we take to be a proxy of long term erosion rates e and the occurrence of over 300 of the largest v 10 8 m 3 terrestrial landslides on earth we find that nearly two thirds of these giant landslides have occurred in the steepest 5 of the earth s land surface where relief is close to its proposed upper strength limit they are primarily located in deeply incised valleys along fault bounded fringes of active mountain belts and in volcanic arcs this distribution coincides with areas of high long term erosion rates 4 mm yr 1 confirming that giant landslides contribute to rapid denudation of mountains most of the eroded volume is concentrated in the smallest but steepest parts of mountain belts and volcanic arcs first order estimates of minimum erosion rates accomplished by the largest landslides are 0 01 mm yr 1 these rates are between 1 and 10 of the late pleistocene to holocene mean erosion rates in a given area importantly the landslide erosion rates show a nonlinear increase with mean local relief suggesting that the contribution of giant landslides in total and per event increases significantly with increasing overall erosion rates however giant landslides also occur in areas of lower than average relief h 300 700 m irrespective of whether threshold hillslopes have developed or not factors contributing to these failures include soft rocks extensive low angle discontinuities high rates of fluvial bedrock incision and tectonically driven deformation and slope loading

long period magnetotelluric measurements near the central california coast a land locked view of the conductivity structure under the pacific ocean summary telluric data from hollister california were combined with magnetic data from the fresno california magnetic observatory to determine the mt response at long periods the shifted eigenstate analysis of latorraca et al 1986 was used to determine the maximum apparent resistivities and corresponding eih phases for periods from 1 to 30 h the apparent resistivity and phase at hollister are greatly influenced by the ocean with the mantle branch beginning at a period of about 12 h in typical continental areas the mantle branch usually begins at periods of 10s or less a maximum likelihood inversion algorithm was used to invert the observed data and to determine the sensitivity of the model parameters the data required a resistivity thickness product of approximately 1 x lo9 q m2 1 x lo6 q m km for the oceanic lower crust and upper mantle the oceanic mantle shows a rather small gradient of conductivity from approximately 200 to 640 km in depth and a rapid conductivity increase below 640km the sensitivity analysis shows the data are most sensitive to the oceanic parameters except for the electric field amplitudes which are also sensitive to the resistivities under the observation site

episodic accumulation and the origin of formation boundaries in the helderberg group of new york state at any single locality in the helderberg group of new york state most formation and member boundaries coincide with boundaries of punctuated aggradational cycles in each case of coincidence the boundary is a discontinuity that was produced by a rapid rise of relative base level rather than a facies contact representing gradual migration of contiguous paleoenvironments apparently diachronous formation boundaries in the sequence are not single continuous surfaces instead each diachronous boundary is actually a stratigraphic series of isochronous surfaces that are separate punctuated aggradational cycles pac boundaries produced by distinct geologically instantaneous base level rises these conclusions about the origin of formation boundaries suggest that the concept of the formation as a fundamental unit of stratigraphic description and interpretation may need revision if the stratigraphic record accumulated episodically on a small scale

microclimate and weathering in the central namib desert namibia data on rock surface microclimates at four sites kleinberg vogelfederberg gobabeb and ganab along a transect across the central namib desert over a 3 year period have been collected alongside some shorter term data sets rock surface temperature rst air temperature wind relative humidity and surface wetness data are presented here weathering of exposure blocks of local marble and granite has also been monitored over the 3 year period with change observed visually and with scanning electron microscopy complex temporal patterns of rock temperature fluctuations are observed over the 3 years although the four sites show very similar overall trends suggesting spatial homogeneity in the rock surface temperature regime relative humidity and surface wetness data show clear differences between the four sites related to the frequency of fogs granite blocks show no visible changes after 2 years of weathering whereas marble blocks especially those at ganab show sem evidence of structural weakening after 1 year

subglacial extensional fracture development and implications for alpine valley evolution 1 bedrock stresses induced through exhumation and tectonic processes play a key role in the topographic evolution of alpine valleys using a finite difference model combining the effects of tectonics erosion and long term bedrock strength we assess the development of near surface in situ stresses and predict bedrock behavior in response to glacial erosion in an alpine valley the matter valley southern switzerland initial stresses are derived from the regional tectonic history which is characterized by ongoing transtensional or extensional strain throughout exhumation of the brittle crust we find that bedrock stresses beneath glacial ice in an initial v shaped topography are sufficient to induce localized extensional fracturing in a zone extending laterally 600 m from the valley axis the limit of this zone is reflected in the landscape today by a valley shoulder separating linear upper mountain slopes from the deep u shaped inner valley we propose that this extensional fracture development enhanced glacial quarrying between the valley shoulder and axis and identify a positive feedback where enhanced quarrying promoted valley incision which in turn increased in situ stress concentrations near the valley floor assisting erosion and further driving rapid u shaped valley development during interglacial periods these stresses were relieved through brittle strain or topographic modification and without significant erosion to reach more highly stressed bedrock subsequent glaciation caused a reduction in differential stress and suppressed extensional fracturing a combination of stress relief during interglacial periods and increased ice accumulation rates in highly incised valleys will reduce the likelihood of repeat enhanced erosion events

the effects of weathering on the strength and chemistry of columbia river basalts and their implications for mars exploration rover rock abrasion tool rat results abstract basalt physical properties such as compressive strength and density are directly linked to their chemistry and constitution as weathering progresses basalts gradually become weaker and transition from intact rock to saprolite and ultimately to soil here we quantify the degree of weathering experienced by the adirondack class basalts at the mars exploration rover spirit site by performing comparative analyses on the strength and chemistry of a series of progressively weathered columbia river basalt crb from western idaho and eastern washington crb samples were subjected to compressive strength tests rock abrasion tool grinds neutron activation analysis and inductively coupled plasma optical emission spectroscopy analyses of terrestrial basalts indicate linked strength chemical changes as expected weathering sufficient to induce the loss of more than 50 of some cations including 50 of mgo and mno as well as 38 of fe 2 o 3 and 34 of cao was observed to weaken these samples by as much as 50 of their original strength in comparison with the terrestrial samples adirondack class basalts are most similar to the weakest basalt samples measured in terms of compressive strength yet they do not exhibit a commensurate amount of chemical alteration since fluvial and lacustrine activity in gusev crater appears to have been limited after the emplacement of flood basalt lavas the observed weakness is likely attributable to thin film weathering on exposed displaced rocks in the gusev plains in addition to some likely shock effects the results indicate that adirondack class basalts may possess a several mm thick weak outer rind encasing an interior that is more pristine than otherwise indicated and also suggest that long rock residence times may be the norm

statistical testing of community patterns uppermost hamilton group middle devonian new york state usa abstract we present an extensive and rigorously controlled quantitative paleoecological study within an interval of inferred coordinated stasis this middle devonian hamilton group study completes a 20 yr project by providing data within the unresolved upper hamilton group section together with other rigorously controlled studies these data sets have the potential to address the larger question of coordinated stasis in the fossil record we collected data from the windom member moscow formation uppermost hamilton group to test different statistical approaches to define paleocommunities we evaluate various techniques including non parametric multidimensional scaling and agglomerative hierarchical clustering to decipher community patterns additionally we advocate regular use of cluster significance testing along with anosim i e analysis of similarities when examining ecological data together these techniques test the significance of sample groups more rigorously than conventional testing e g discriminant analysis or analysis of variance anova our results indicate that communities within this upper hamilton group interval exhibit variable taxonomic membership within a relatively stable ecological structure

sequences cycles and basin dynamics in the silurian of the appalachian foreland basin abstract field stratigraphic analysis of the early and medial silurian strata of ontario new york and pennsylvania permits recognition of six major sequences reflecting 3rd order cycles in the niagaran llandoverian ludlovian of new york and adjacent regions these sequences correspond approximately to the medina lower clinton middle clinton upper clinton two sequences and lockport groups each is bounded by widespread unconformities produced by the interplay of eustatic sea level drop and local tectonic uplift in general erosional sequence boundaries and transgressive surfaces are merged with no record of the lowstand wedge each sequence is subdivisible into two to five sub sequences that are marked by sharp though generally non erosional basal discontinuities investigation of the clinton and lockport groups corroborates earlier suggestions that carbonate and siliciclassic tongues extended basinward from opposite margins synchronously in response to sea level drops analysis of the thickness and basinward extent of the progradational tongues reveals the existence of multi scale sedimentary cycles sequences and component sub sequences are correlative basinwide and are synchronous within the resolution of bio and event stratigraphy major drops in relative sea level are represented by the sequence bounding discontinutiies these surfaces are overlain by siliciclastic wedges near terrigenous source areas or winnowed carbonate pack and grainstones on the tectonically passive margin overlying highstand deposits typically shales calcareous mudstones and limestones are separated from lowstand or transgressive deposits by thin condensed intervals commonly marked by phosphatic or glauconitic material and or surfaces of maximum sediment starvation the relative highstand deposits of sequences and sub sequences are developed in relatively deep water facies and are at most slightly progradational hence most sequences and sub sequences are sharply bounded roughly upward deepening to slightly shallowing successions of strata in turn sub sequences are further divisible into widespread minor parasequences and parasequence sets probably corresponding to 6th and 5th order cycles respectively the smaller scale units 0 2 5 mthick commonly display an upward shallowing motif the nested relationship of these cycles supports the hierarchical model of transgressive regressive allocycles proposed by busch and rollins 1984 niagaran cycles discussed herein are equivalent to third fourth and fifth order cycles and are traceable circumbasinally depocenters of successive sequences and sub sequences display a pattern of eastward westward eastward basin axis migration through the silurian during early llandoverian the taconic queenston deltaic complex began to subside and the basin axis depocenter and eastern shoreline shifted eastward approximately 200 km over a 6 million year period as the basin axis migrated eastward the western basin ramp forebulge was repeatedly upwarded and eroded resulting in the generation of regionally angular unconformities at the bases of sequences ii iv and vi the pattern of unconformity greatest to the west suggests rise of the algonquin arch concomitant with eastward basin axis migration during the late llandoverian to early wenlockian the algonquin arch subsided slightly concurrently with a reversal in direction of basin axis migration during deposition of upper clinton and lockport vernon strata sequences v vi the basin axis shifted approximately 300 km back to the west eastward migration of the basin axis corresponds with a time of tectonic quiescence and probable thrust load relaxation the abrupt reversal of migration in the late llandoverian may be a signal of renewed thrusting in the hinterland at the onset of the salinic disturbance

thickness trends and sequence stratigraphy of the middle devonian marcellus formation appalachian basin implications for acadian foreland basin evolution analysis of more than 900 wireline logs indicates that the middle devonian marcellus formation encompasses two third order transgressive regressive t r sequences mss1 and mss2 in ascending order compositional elements of the marcellus formation crucial to the successful development of this emerging shale gas play including quartz clay carbonate pyrite and organic carbon vary predictably within the proposed sequence stratigraphic framework thickness trends of marcellus t r sequences and lithostratigraphic units reflect the interplay of acadian thrust load induced subsidence short term base level fluctuations and recurrent basement structures rapid thickening of both t r sequences especially mss2 toward the northeastern region of the basin preserves a record of greater accommodation space and proximity to clastic sources early in the acadian orogeny however local variations in t r sequence thickness in the western more distal area of the basin may reflect the reactivation of inherited eocambrian basement structures including the rome trough and northwest striking cross structural discontinuities induced by acadian plate convergence episodes of block displacement locally warped the basin into northeast southwest trending regions of starved sedimentation and or erosion adjacent to depocenters in which regressive systems tract deposits were ponded block movement appears to have initiated in late early devonian time resulting first in thinning and local erosion of the oriskany sandstone in northwest pennsylvania this study in addition to providing the basis for a predictive sequence stratigraphic model that can be used to further marcellus exploration tells of a foreland basin more tectonically complex than accounted for by simple flexural models

methods for measuring rock surface weathering and erosion a critical review studies of rates processes and modes of rock surface and near surface deterioration and also hardening are central to rock weathering and building stone research conservation and management there is a need to measure and monitor weathering at the rock atmosphere interface to facilitate understanding of climatic environmental and lithological controls on the evolution and development of surface weathering features this paper reviews long established and recently developed field and laboratory methods used by geomorphologists to monitor and measure the impact of weathering and erosion on physical and mechanical properties of exposed rock surfaces and their immediate subsurface key advances are highlighted their application to multi scalar understanding and modelling of rock surface weathering in different contexts is discussed and potential future advances to provide new insights into rock weathering durability and materials conservation are identified in highlighting key advantages and disadvantages of a wide range of methods to the broader earth science community the paper aims to contribute to further innovative thinking across disciplines to develop new methods for measuring and monitoring rock weathering

the use of the schmidt hammer and equotip for rock hardness assessment in geomorphology and heritage science a comparative analysis rapid field based measurements of rock hardness are of use in investigating many geomorphological and heritage science problems several different methods are now available for taking such measurements but little work has been done to assess their comparability and strengths and weaknesses we review here the capabilities of two types of schmidt hammer classic n type and silver schmidt bl type alongside two types of equotip standard type d and piccolo for investigating rock hardness in relation to rock weathering on various types of sandstone and limestone as well as basalt and dolerite whilst the two schmidt hammers and the two equotips show comparable results when tested at 15 individual sites interesting differences are found between the equotip and schmidt hammer values which may reveal information about the nature of weathering on different surfaces operator variance is shown to be an issue in particular for the equotip devices which also exhibit higher variability in measurements and necessitate larger sample sizes carborundum pre treatment also has varying effects on the data collected depending on the nature of the surface studied the equotip devices are shown to be particularly useful on smaller blocks and in situations where edge effects may affect schmidt hammer readings we conclude that whilst each device contributes to geomorphological research they do not necessarily produce comparable information indeed using schmidt hammer and equotip in combination and looking at any differences in results may provide invaluable insights into the structure of the near surface zones and the nature of weathering processes copyright 2010 john wiley sons ltd

punctuated aggradational cycles a general hypothesis of episodic stratigraphic accumulation according to the hypothesis of punctuated aggradational cycles presented here the stratigraphic record consists of small scale 1 5 m thick shallowing upward cycles pacs separated by surfaces marked by abrupt change to deeper facies this motif pervasive in time and environment is produced by relatively long periods tens of thousands of years of base level stability punctuated by geologically instantaneous relative base level rises of at least basin wide extent as basin wide lithologic time stratigraphic units pacs are fundamental to all aspects of stratigraphic analysis including correlation paleoenvironmental interpretation and paleogeographic reconstruction of several possible allogenic mechanisms for a pervasively cyclic stratigraphic record glacial eustasy driven by orbital perturbations is preferred the pac hypothesis is presented as a comprehensive model to be tested and modified by examination of the stratigraphic record from an episodic perspective

defining the nature and location of a late devonian early mississippian pycnocline in eastern kentucky the pycnocline the intermediate layer in a tripartite density stratified water column is an important element in recent explanations of the origin of anaerobic sediments dysaerobic sediments deposited where the pycnocline intersects the bottom are distinct from overlying aerobic and underlying anaerobic sediments and were used to define the position of the paleopycnocline on a late devonian early mississippian sea bottom in eastern kentucky surface and subsurface mapping of the bedford berea sequence and equivalent parts of the new albany and chattanooga shales reveals approximately coeval aerobic dysaerobic and anaerobic facies that permitted mapping of the paleopycnocline apparently the first time the actual sea bottom position of a paleopycnocline has been defined the bedford berea devonian mississippian sequence is situated between the black ohio shale devonian below and the black sunbury shale mississippian above the black shales reflect deposition in a deepening transgressive sea where anaerobic conditions were easily established and maintained the intervening bedford berea sequence however represents deposition in aerobic and dysaerobic environments during a shallowing regressive episode as deltas prograded to the south and west in eastern kentucky the gray sandstones siltstones and shales of the bedford berea sequence have been interpreted as pinching out between the black shales above and below in east central kentucky each of the above units however has a distinctive signature on gamma ray logs comparison of gamma ray logs and radioactivity profiles with corresponding cores drillers9 logs and exposures indicates that black shale equivalents are present beyond the point where the gray bedford shale pinches out this also is supported by limited biostratigraphic data this transition from gray bedford shales to black shale equivalents marks the approximate position of the ancient pycnocline and has been mapped in the subsurface and on the outcrop in eastern kentucky the ancient pycnocline closely parallels the bedford berea delta front suggesting major control by the delta the continued influx of oxygen rich sediment laden waters from the delta apparently prevented the northward and eastward migration of the pycnocline up the delta front the introduced oxygen and sediment however were effective only in breaking up the pycnocline over a distance of 25 to 40 km from the active delta fronts stratigraphic paleontologic and geographic constraints indicate that the paleopycnocline was not horizontal but sloped northeastward from shallower waters near the cincinnati arch to deeper waters off the delta fronts

mudrock sequence stratigraphy a multi proxy sedimentological paleobiological and geochemical approach devonian appalachian basin abstract delineation of stratigraphic sequences and their component systems tracts in mudrock dominated facies is generally difficult due to the relatively homogenous fine grained nature of the strata in this study we apply a multi proxy analytical approach to a thick devonian mudrock dominated succession through detailed analysis of sedimentologic paleobiologic and geochemical data through 600 m of mudrock rich facies varied combinations of proxies prove to be most useful in delineating sequence development in anoxic dysoxic and oxic dominated mudrock settings and in mixed mudrock carbonate and mixed mudrock sandstone successions these interpretations are tested against an established sequence stratigraphic framework for 11 middle to upper devonian mid eifelian to lower famennian sequences in the appalachian basin the sequences presented here further detail and refine global devonian t r cycles id to iie of the well known johnson sandberg and klapper sea level curve the usefulness of proxies in delineating depositional sequences and systems tracts varies dependent on depositional paleoceanographic paleoecologic and early diagenetic conditions those proxies that show a range of variations in specific settings such as grain size degree of bioturbation and concentrations of toc and elements elemental ratios e g caco3 al ti mg sc si mo ni v si al and ti al may help delineate depositional dynamics related to redox conditions condensation dilution and clastic biologic and or authigenic sediment sources in fine grained anoxic dominated facies interpreted to represent basinal settings sequences and systems tracts are best delineated by anoxic related proxies toc and mo in intermediate dysoxic dominated settings toc mo bioturbation and al remain effective indicators of sequence development in relatively oxygenated mudrock rich and carbonate poor sequences bioturbation may function as the most effective proxy for recognizing systems tracts for mixed fine grained siliciclastic carbonate successions concentration and type of caco3 e g benthic macroskeletal pelagic styliolinid dacryoconarid and micritic calcisilt are useful in identifying position within cycles in more proximal carbonate poor successions fine and coarse grained fractions become increasingly differentiated these can be distinguished by relatively high si al ratios si al ca 5 elemental ratios indicative of coarser clastic input e g si al zr al and ti al are applicable to identifying position with a sequence but they may also be affected by input from eolian volcanogenic or biogenic sources in addition fluxes of siliciclastic carbonate and toc sediment types may dilute the concentration of the others multiple lines of evidence should be examined in interpreting relative depth and position within a sequence

environmental and physiological influences on isotopic and elemental compositions of brachiopod shell calcite implications for the isotopic evolution of paleozoic oceans abstract brachiopods from the demissa bed middle devonian hamilton group biologically regulated the incorporation of mg sr and na into their shell calcite significant taxonomic differences in the elemental contents of three species athyris spiriferoides mediospirifer audacula and mucrospirifer mucronatus may be related to differences in calcification processes in contrast no significant difference or vital effects were observed between the isotopic values of mediospirifer audacula and athyris spiriferoides from erie 18o 0 03 p 0 949 13c 0 76 p 0 083 and genessee counties 18o 0 39 p 0 471 13c 0 06 p 0 854 this suggests that these brachiopods did not exert a biological control over their isotopic compositions and that their shell calcites reflect ambient physicochemical conditions isotopic compositions in unaltered shell calcites of brachiopods from genessee county which was close to the basin depocentre are heavy for carbon 13c x 5 01 pdb and oxygen 18o x 2 85 pdb compared to the species sampled at the basin s edge erie county 13c x 2 79 pdb 18o x 3 83 pdb there is a significant separation in isotopic values between the deeper and shallower water brachiopods of the basin 18o 0 98 p 0 0005 13c 2 22 p 0 0005 the 18o variation suggests a temperature salinity change with water depth whereas the change in 13c composition probably records an enrichment depletion of organic matter with water depth this observation has significant implications for paleozoic ocean isotopic evolution studies because many global changes in marine 18o and 13c are based on isotopic shifts of similar magnitude