Rock Face Research Articles

The origin of sandstone boulder aprons along the escarpments of the Stołowe Mountains: are they all rockfall-derived? A new insight into an old problem using the CONEFALL 1.0 software

Abstract A characteristic feature of sandstone-capped escarpments in the Stołowe Mountains is the occurrence of extensive boulder mantles which extend from the rock face to the footslope over distances of 300–500 m. The hypothesis implying rockfall as the process of boulder release from the rock face and subsequent transport is tested by means of Conefall 1.0 software, designed to simulate run-out zones of rockfalls. The actual extent of boulder mantles is much larger than the simulated extent, which casts doubt on the applicability of rockfall scenario. Alternative hypotheses are briefly discussed and it is concluded that a similar morphological effect can be achieved by in situ caprock disintegration and sub-caprock slope lowering and retreat.

Allusions to Agriculturist Rituals in Hunter-Gatherer Rock Art? eMkhobeni Shelter, Northern uKhahlamba-Drakensberg, KwaZulu-Natal, South Africa

Unusual and uncommon motifs at eMkhobeni Shelter, in the foothills of the northern uKhahlamba-Drakensberg of KwaZulu-Natal, look like Bushman hunter-gatherer paintings. However, amidst the many images at this site are motifs that apparently allude to a historic cultural practice of Bantu-speaking agriculturists—the widely performed first-fruits festival, as well as to Nguni rain-making practices. These motifs include the slaughter of a bull with an axe, depictions of figures wearing items of Nguni clothing, figures driving black-painted cattle and a black sheep. The motifs are understood here as symbols of fertility, especially rain-making, that the eMkhobeni painters (argued to be Bushman hunter-gatherers living alongside agriculturists) incorporated into their repertoire. The creation on the rock face of signal moments from first-fruit ceremonies and the painting of black cattle and sheep may be understood as a way of strengthening Bushman hunter-gatherer control over fertility and rain-making. It is argued that the imagery validated the social and economic position of local Bushman hunter-gatherer groups and their ritual practitioners, especially in the eyes of their agriculturist neighbours.

Remote detection of fluid-related diagenetic mineralogical variations in the Wingate Sandstone at different spatial and spectral resolutions

Well-exposed eolian units of the Jurassic system on the Colorado Plateau including the Wingate Sandstone, show prominent color variations throughout southeastern Utah due to diagenetic changes that include precipitation and/or removal of iron oxide, clay, and carbonate cement. Spatially variable characteristic diagenetic changes suggest fluid-rock interactions through the sandstone. Distinctive spectral signatures of diagenetic minerals can be used to map diagenetic mineral variability and possibly fluid-flow pathways. The main objective of this work was to identify characteristic diagenetic minerals, and map their spatial variability from regional to outcrop scale in Wingate Sandstone exposures of Lisbon Valley, Utah. Laboratory reflectance spectroscopy analysis of the samples facilitated identification of diagnostic spectral characteristics of the common diagenetic minerals and their relative abundances between altered and unaltered Wingate Sandstone. Comparison of reflectance spectroscopy with satellite, airborne, and ground-based imaging spectroscopy data provided a method for mapping and evaluating spatial variations of diagenetic minerals. The Feature-oriented Principal Component Selection method was used on Advanced Spaceborne Thermal Emission and Reflection Radiometer data so as to map common mineral groups throughout the broader Wingate Sandstone exposure in the area. The Minimum Noise Fraction and Spectral Angle Mapper methods were applied on airborne HyMap and ground-based hyperspectral imaging data to identify and map mineralogical changes. The satellite and airborne data showed that out of 25.55km2 total exposure of Wingate Sandstone in Lisbon Valley, unaltered sandstone cover 12.55km2, and altered sandstone cover 8.90km2 in the northwest flank and 5.09km2 in the southern flank of the anticline. The ground-based hyperspectral data demonstrated the ability to identify and map mineral assemblages with two-dimensional lateral continuity on near-vertical rock faces. The results showed that 39.71% of the scanned outcrop is bleached and 20.60% is unbleached while 6.33% remain unclassified, and 33.36% is masked-out as vegetation. The bleached and unbleached areas are alternating throughout the vertical face of the outcrop. The relative hematite abundance observed in the unbleached areas are somewhat symmetrical. This indicates fairly similar reaction intensities along the upper and lower reaction fronts observed in the vertical section. The distribution geometry and relative abundances of diagenetic minerals not only suggest multiple paths of fluid-flow in Wingate Sandstone but also provides some insight about relative direction of past fluid-flow.

Boulder aprons indicate long-term gradual and non-catastrophic evolution of cliffed escarpments, Stołowe Mts, Poland

Caprock-crowned escarpments are characteristic geomorphic features of the sandstone tableland of the Stołowe Mountains (SW Poland). Their mid- and lower slopes truncate weaker sedimentary formations but are littered with sandstone boulders of various size, often more than 5m long, which form nearly continuous aprons. A model of escarpment retreat by rock fall has been widely accepted in literature but in the Stołowe Mountains it has never been tested against field evidence; in addition no rock fall events except one minor fall in 1921 have been recorded in historical times. In this paper we erected five hypotheses of how escarpments may have evolved through time to result in widespread boulder presence on the slopes. Mapping boulder extent and slope morphology, run-out distance simulations using Conefall software, and rock strength determinations using the Schmidt hammer carried out on boulders along eight representative slope profiles provide data about characteristics of the boulder covers. Systematic decrease in intact rock strength with an increasing distance from the sandstone cliffs suggests that the boulder aprons are diachronic and record long-term retreat of escarpments. There exists no conclusive evidence of widespread boulder downslope movement, although in a few localities shallow landslides have rafted boulders far away from the cliff lines. Modelling exercise shows that the actual extent of boulders is 2–3 times bigger than suggested by Conefall predictions. These findings, coupled with observations along the cliff lines themselves, lead us to propose a model of free face in situ disintegration as the most likely hypothesis to explain block detachment and release from rock faces. As cliff lines recede and the slope surface below is lowered, remnant boulders occupy a position increasingly further away from escarpment rims, but experience little actual movement. This model complements the existing models of tableland evolution which tend to emphasize catastrophic mass movement processes on cliffed escarpments.

Landward-advancing Quaternary eolianites of Bermuda

The landscape of Bermuda is dominated by Quaternary carbonate cemented dunes, or “eolianites”, which form the islands’ topography. Sections through the dunes are revealed in extensive natural and man-made rock faces, which expose the dune stratigraphy as well as the preserved morphology. An analysis of 3751 foreset measurements confirms the conclusion reached by earlier researchers that Bermuda’s dunes advanced sub-perpendicularly to the coast in a landward direction away from source beaches. Dune orientation, being multi-directional, is not consistent with northeast net sand transportation predicted by a drift potential analysis of modern wind data. The putative predisposition of Bermuda’s carbonate dunes to rapid cementation is supposed to have curtailed their landward advance such that younger dunes developed as static ridges at the seaward margin of their lithified predecessors. Geological mapping has revealed, however, that in many cases young dunes did advance inland onto interior terrain, overstepping older dune ridges. Molds of large trees, preserved within the dunes, and a sharp contact of steep slip-face dune foresets on palaeosols evoke the encroachment of landward-advancing precipitation ridges into a forested landscape. The internal structure of the dunes, featuring thick sets of slip-face foresets truncated by sub-horizontal planar bounding surfaces, uphold the ascendancy of sand transportation processes over those of sand retention and vertical accretion. Although meteoric cementation was responsible for the ultimate preservation of eolianite ridges which dominate Bermuda’s landscape, it took effect too slowly to influence the behaviour of the carbonate dunes at the time of their emplacement.

La Viña rock shelter (La Manzaneda, Oviedo, Asturias): Relation between stratigraphy and parietal engravings

Abstract La Vina rock shelter (La Manzaneda, Oviedo, Asturias) is the easternmost of the thirteen open sites with rock engravings spread along the Nalon river basin. La Vina is the largest settlement in that valley and contains the most extensive archaeological sequence, from the Middle Palaeolithic to the Holocene, as well as an important set of engravings, clustered along the rock face with diverse level of preservation. Fortea organized those carvings into two successive graphical horizons, Aurignacian and Gravettian–Solutrean. Recent topographical surveys (coordinates in the ETRS89) in the site have specified those proposals and have released new data about the spatial and chronological organization of the engravings.

Review of Photogrammetry-Based Techniques for Characterization and Hazard Assessment of Rock Faces

Photogrammetry-based techniques offer a fast and inexpensive way to obtain data needed for geotechnical characterization and hazard assessment of steep rock faces. These techniques also mitigate fieldwork risks associated with conventional structural mapping methods. A camera can function as an accurate survey tool, in most cases as accurate as conventional laser-based survey equipment. Millions of 3D coordinates can be determined from only a few photographs. Mounting a camera on an Unmanned Aerial Vehicle (UAV) solves many of the challenges associated with measuring and mapping steep rock faces. Small low-cost UAVs offer operational flexibility and high quality images. With good photographs taken from appropriate locations, photogrammetry or structure from motion software can generate accurate point clouds, digital surface or terrain models, and orthophotos. With further analysis and interpretation, these can yield the geotechnical data needed to create realistic models in discrete element or finite element software to perform stability assessment.

Measuring Orientations of Hidden Sub-Vertical Discontinuities in Rock Cuts Integrating Ground Penetrating Radar and Terrestrial LIDAR

Vertical or sub-vertical discontinuities striking parallel to rock cuts are dangerous because toppling and spontaneous raveling failures can initiate from these surfaces, creating hazards below. At the same time these surfaces are often hidden, because they do not daylight into the cut on either side, and any trace of the discontinuity that might be seen at the top of the cut is obscured by overburden. These hidden discontinuities can often be detected by Ground Penetrating Radar (GPR). Used in conjunction with Terrestrial LIDAR (LIght Detection And Ranging), it is possible to accurately measure the orientation of these hidden discontinuities. The method presented in this paper establishes three control points on the surface of the rock cut. At each control point the global coordinates are measured using LIDAR. GPR soundings at each control point are used to measure the perpendicular horizontal distance (depth) to any discontinuities hidden behind the rock face by GPR. The true perpendicular distance is added to the GPR coordinates at each control point to form three new control points on the surface of each of the hidden discontinuities. Using the three point method the orientation of the hidden discontinuity is calculated.

Thermodynamic properties of zýkaite, a ferric sulfoarsenate

Zýkaite, nominally Fe4(AsO4)3(SO4)(OH)⋅15H2O, is a common ferric arsenate in damp, moist environments, especially in underground spaces where the humidity does not decline during the year and the temperature fluctuations are minimal. The natural sample used in this study had chemical composition Fe1.23(AsO4)0.93(PO4)0.07(SO4)0.31(OH)0.07⋅5.89H2O and typical poor crystallinity. The solubility product, derived from solubility experiments, is log Ksp=−25.77 for the reaction Fe1.23(AsO4)0.93(PO4)0.07(SO4)0.31(OH)0.07⋅5.89H2O+0.07 H+=1.23Fe3++0.93AsO43−+0.07PO43−+0.31SO42−+5.96H2O. Enthalpy of formation, determined by acid-solution calorimetry, is −2952.2±2.9kJmol−1. Gibbs free energy of formation, calculated from the log Ksp value, is −2485.1kJmol−1. The entropies of zýkaite, estimated for a solid and calculated from its enthalpy and Gibbs free energy of formation, are in a fair agreement and document the accuracy of the thermodynamic data. Variable-temperature powder X-ray diffraction showed that the structure of zýkaite gradually collapses and turns amorphous at ∼90°C. No crystalline phase formed upon heating to 200°C. Zýkaite is one of the least stable phases in the system Fe2O3–As2O5–SO3–H2O, restricted to environments with low pH and very high activities of As(V) and S(VI). Zýkaite and kaňkite (FeAsO4⋅3.5H2O) are often seen on the gently sloping rock faces or on the rock walls, whereas stalactites of hydrous ferric arsenate forms below them on the overhangs. Thermodynamic modeling with our data show that the transformation of zýkaite to other ferric arsenates and sulfoarsenates (scorodite, parascorodite, kaňkite, bukovskýite, hydrous ferric arsenates) is thermodynamically driven. Comparing and combining our thermodynamic data, modeling, variable-temperature X-ray diffraction, and field observations, it seems that zýkaite transforms readily to other phases in the system Fe2O3–As2O5–SO3–H2O via dissolution and precipitation; a solid-state transformation is unlikely.

TLOS ANTİK KENTİ YAKINLARINDAKİ TAVABAŞI MAĞARASI KAYA RESİMLERİ

Likya Bolgesi sahip oldugu tarihi ve dogal zenginlikleriyle Anadolu uygarliklari icerisinde onemli bir konuma sahiptir. Herodot Likya halkinin Girit 'ten goc ettigini belirtmistir. Homeros'un Ilyada Destani'nda Likya ordusunun Troya savaslarinda Sarpedon onderliginde Akhalara karsi kahramanca mucadelesi anlatir. Hem Hitit tabletleri hem de misir hiyerogliflerinden Likya ordusunun Kades Savasi'nda Hititlerin yaninda savastigi da bilinmektedir. Likya halkinin Demircag oncesinde bu topraklardaki varligi yakin zamana kadar arkeolojik buluntularla belgelenememistir. Dolayisiyla kendilerine ozgu bir dili ve sanati olan Likyalilarin tarihsel gecmisi hakkinda farkli gorusler ortaya atilmistir. Tlos Antik Kenti ve yakin cevresindeki Tavabasi - Girmeler magaralarinda yapilan arastirmalar Likya Bolgesi'ndeki yasamin Hititler zamanindan daha once basladigini gostermistir. Tlos kent merkezinde yurutulen kazi calismalari esnasinda Kalkolitik Donem ve Tunc Cagina ait yerlesim kalintilarina ulasilmistir. Girmeler Magarasi onunde tespit edilen hoyukteki en erken yerlesim katmani seramiksiz Neolitik Donem'e tarihlenmektedir. Tavabasi magaralari da benzer sekilde Neolitik Donem'den itibaren bolge insaninin sosyal yasam detaylarini iceren arkeolojik veriler sunmaktadir. Magaralarin dis yuzeylerinde bulunan farkli ikonografideki kaya resimleri prehistorik donemlere ait Tavabasi yerlesiminin onemli kanitlarindandir.

Finite Element Models of Disk Tools with Attachment Points on Triangular Prisms

The paper presents simulation of the stress-strain state of various designs of disk tool attachment points on triangular prisms of radial bits of the roadheaders working body when cutting of coal and rock face.

Stress State of Disk Tool Attachment Points on Tetrahedral Prisms between Axial Bits

The paper presents results of simulation of stress-strain state of disk tools attachment points on tetrahedral prisms of working bodies of multipurpose roadheaders while cutting of coal and rock faces.

Rock Surface Classification in a Mine Drift Using Multiscale Geometric Features

Scale-dependent statistical depictions of surface morphology offer the potential to parameterize complex geometrical scaling relationships with greater detail than traditional fractal measures. Using multiscale operators, it is possible to identify points belonging to rough discontinuous surfaces in noisy point clouds solely on the basis of their local geometry. Many strategies for point cloud feature classification have been developed since the proliferation of laser scanning systems. Most of the techniques which are applicable to natural scenes employ external data sources such as hyperspectral imagery, return pulse intensity, and waveform data. In this letter, multiscale geometric parameters are used to identify individual point observations corresponding to rock surfaces in point clouds acquired by terrestrial laser scanning in scenes with man-made clutter and scanning artifacts. Three multiscale operators, namely, the approximate shape and density of a defined neighborhood and the distance of its mean point from its geometric center, are fused into a single feature vector. The procedure is demonstrated using real point cloud data acquired in a mine drift, with the goal of identifying points belonging to the rock face obscured by an overlying wire support mesh. Using the extra-trees classifier, extraneous returns caused by the mesh were excluded from the point cloud with a 97% success rate, while 87% of the desired surface points were retained.

Determination of warm, sensitive permafrost areas in near‐vertical rockwalls and evaluation of distributed models by electrical resistivity tomography

AbstractAlpine rockwalls with warm permafrost (near 0°C) are the most active rockfall detachment zones in the Mont Blanc massif (MBM, French Alps) with more than 380 recent events. Near‐vertical rockwall permafrost is spatially controlled by variations in rock fractures, snow cover, and microtopography. A reliable method to validate the distribution of permafrost in critical and unstable areas does not yet exist. We present seven electrical resistivity tomography (ERT) surveys measured on five near‐vertical rockwalls in the MBM from 2012 and 2013 that have been calibrated with measurements on a granite sample in the laboratory. ERT shows consistent measurements of remaining sensitive permafrost relating to inferred temperatures from 0 to −1.5°C. ERT results demonstrate evidence of topographic controls on permafrost distribution and resistivity gradients that appear to reflect crest width. ERT results are compared to two permafrost index maps that use topoclimatic factors and combine effects of thin snow and fractures, where index model spatial resolution is crucial for the validation with ERT. In cryospheric environments, index maps seem to overestimate permafrost conditions in glacial environments. As a consequence, the sensitive areas of permafrost may slightly deviate from the results from distributed models that are only constrained by topoclimatic factors and interpreted with consideration of local fracture and snow conditions. This study demonstrates (i) that the sensitive and hazardous areas of permafrost in near‐vertical rock faces can be assessed and monitored by the means of temperature‐calibrated ERT and (ii) that ERT can be used for distributed model validation.

Stream invertebrate productivity linked to forest subsidies: 37 stream-years of reference and experimental data.

Riparian habitats provide detrital subsidies of varying quantities and qualities to recipient ecosystems. We used long-term data from three reference streams (covering 24 stream-years) and 13-year whole-stream organic matter manipulations to investigate the influence of terrestrial detrital quantity and quality on benthic invertebrate community structure, abundance, biomass, and secondary production in rockface (RF) and mixed substrates (MS) of forested headwater streams. Using a mesh canopy covering the entire treatment stream, we examined effects of litter ex'clusion, small- and large-wood removal, and addition of artificial wood (PVC) and leaves of varying quality on organic matter standing crops and invertebrate community structure and function. We assessed differences in functional feeding group distribution between substrate types as influenced by organic matter manipulations and long-term patterns of predator and prey production in manipulated vs. reference years. Particulate organic matter standing crops in MS of the treatment stream declined drastically with each successive year of litter exclusion, approaching zero after three years. Monthly invertebrate biomass and annual secondary production was positively related to benthic organic matter in the MS habitats. Rockface habitats exhibited fewer changes than MS habitats across all organic matter manipulations. With leaf addition, the patterns of functional group distribution among MS and RF habitats returned to patterns seen in reference streams. Secondary production per unit organic matter standing crop was greatest for the leaf addition period, followed by the reference streams, and significantly less for the litter exclusion and wood removal periods. These data indicate that the limited organic matter remaining in the stream following litter exclusion and wood removal was more refractory than that in the reference streams, whereas the added leaf material was more labile and readily converted into invertebrate production. Predator production and total production were tightly coupled in reference and treatment streams, indicating strong relationships between predators and their prey. Results from the artificial wood addition demonstrate that physical structure alone will not restore invertebrate productivity without detrital resources from the riparian forest. Our long-term studies conducted over three decades at the ecosystem scale unequivocally show the necessity of maintaining and restoring aquatic-terrestrial linkages in forested headwater streams.

Karst porosity estimations from archive cave surveys - Studies in the Buda Thermal Karst System (Hungary)

The Buda Thermal Karst System is located under the densely populated hills of Budapest. One of its caves (Pál-völgy Cave System) is the longest cave of Hungary with 30.1 km. The research was done in this area as a methodological study to estimate karst porosity parameters of aquifers or hydrocarbon reservoirs. In this study two modeling methods are demonstrated. The volumetric modeling method was primarily aimed to determine the macro-scale (>0.5 m) conduit porosity (referred as macroporosity) of the study area as percentage of the incorporating limestone and marl. This method is based on archive survey data (maps and records). Through this method, morphometric parameters and the approximate sizes of the unexplored cave parts were also calculated. The porosity modeling was aimed at the estimation of the meso-scale (0.02–0.5 m) and macro-scale conduit porosity. It is based on rock face measurements near the Pál-völgy Cave System and image analysis. The matching macroporosity estimations of the two methods suggest that the map-based volumetric modeling method can be a useful tool for karstologists and modeling experts to extract as much information as possible from existing cave maps, even if the records of the original survey were lost or scanty. With the matrix porosity data published earlier from this area, and the conduit porosity calculated from the models, hydrological models of the area can be completed.

Mapping and characterization of rock discontinuities in a tunnel using 3D terrestrial laser scanning

This paper attempts to evaluate various methods of geometrical discontinuity characterization using point clouds that are generated with three-dimensional terrestrial laser scanning (3DTLS) in a tunnel. The use of 3DTLS to support discontinuity mapping in tunnels enables the acquisition of a large amount of data without limitations in terms of the tunnel position (wall or roof). Thus, the discontinuity orientation, trace length and frequency were statistically analyzed in different regions of the tunnel to determine the most representative data. Different methods of estimating the mean trace length were compared while considering the variations in the rock face orientation in the tunnel, and the unbiased standard deviation of the trace length was evaluated. The frequencies of discontinuity sets were obtained using scanlines, and aspects of window sampling for density (areal frequency) estimates in tunnels are discussed. The mean trace lengths obtained using rectangular sampling windows (considering the relative frequency of the traces) are more suitable for estimates of different rock face orientations, particularly when the orientation of the discontinuity set varies significantly. In this case, measurements of samples from the tunnel roof presented higher values for both frequency and mean trace length estimates, which demonstrates the importance of data acquisition and evaluation in this region.

Geostructure of Coroglio tuff cliff, Naples (Italy) derived from terrestrial laser scanner data

We present a long-range terrestrial laser scanner application for the geostructural mapping of Coroglio cliff, a tuff rock face exposed along the coastal zone of Campi Flegrei, Napoli. The procedure includes several phases (geomorphological analysis, structural field survey, laser scanner data acquisition and data processing, 3-D model development and analysis, geostructural classification of discontinuity orientation data and 2-D vertical cartographic production). Field data were processed with specific software dedicated to geostructural and geometric analysis. Spatial data were managed with a geographical information system and have been used for the construction of 2-D and 3-D geometric models of the rock cliff surface and geostructural interpretation. The main product of this study is a vertical geostructural map of the Coroglio cliff at 1:500 scale that illustrates the spatial distribution and orientation of the major families of structural discontinuities detected along the exposed surface of the cliff. The cartographic product includes base information useful to identify the main rock failure mechanisms along the cliff and represents a first step for the zonation of areas susceptible to block failures and the planning of monitoring activities.

Geological mapping and fold modeling using Terrestrial Laser Scanning point clouds: application to the Dents-du-Midi limestone massif (Switzerland)

Geological mapping in vertical rock faces is extremely challenging because of access difficulties and limited possibilities of recognition, localization and measurement of features at large distance with traditional tools. Moreover, vertical areas can be of primary interest since they often display good quality outcrops and relevant geological information. This study focuses on the detailed remote identification of rock types and fold structures using intensity values acquired by Terrestrial Laser Scanning. A correction of the intensity is proposed proportional to the square of the range and to the cosine of the incidence angle. Furthermore, two methods of remote lithological mapping in 3D have been developed using a manual and a semi-automatic approach. Both delivered good results that are consistent with the spatial distribution of rock-types and allowed us to generate an accurate 3D lithological map of Dents-du-Midi massif (Valais, Swiss Alps). The bedding orientation near the hinge of a Km scale fold was measured on LiDAR data in order to define the fold axis. Then, the result was used to build a model of the hinge in 3D.

Geological layers detection and characterisation using high resolution 3D point clouds: example of a box-fold in the Swiss Jura Mountains

The detection and characterisation of geological layers, as well as the precise quantification of their geometrical properties, is of primary interest in several domains of geology. Nevertheless, geological data gathering is commonly limited by access issues during fieldwork investigations. Here we present complementary and alternative tools aimed at allowing the investigation of areas with limited accessibility, such as vertical rock faces. We used 3D point clouds acquired from Terrestrial Laser Scanning and terrestrial photogrammetry to: 1) identify and model (reconstruct) the geometry of the geological layers and 2) semi-automatically segment the different lithologies according to their intensity signature. Our results show that the presented procedures are fast, reliable and efficient compared to traditional fieldwork. In particular, the geometrical analysis led to a very detailed characterisation of the bedding planes, which couldn't be targeted with sufficient precision based on fieldwork alone. The lithological mapping procedure, which was obtained through a semi-automatic segmentation process of a single intensity channel, is highly capable since nearly all the layers were correctly attributed to their corresponding lithology. The performance of the segmentation script was closely related to our prior fieldwork investigation, yielding validation of our semi-automatic point cloud segmentation.