Loose Sediments Research Articles

Holocene Deposits of Saharan Rock Shelters: The Case of Takarkori and Other Sites from the Tadrart Acacus Mountains (Southwest Libya)

The excavation at Takarkori rock shelter is part of a long-term study of Holocene cultural dynamics in southwest Libya begun in the early 1990s. With a rich Holocene occupation, the area is one of the key spots for reconstruction of human occupation of the last 10,000 years. In this region, similar to the case in the rest of the Sahara, most of the data come from surface investigations at open-air sites, while excavated caves and rock shelters provide just a few. Although less exposed than open-air sites, Holocene archaeological deposits in Saharan caves and rock shelters are characterized by a fairly dynamic nature. Loose sediments, coupled with variability of human occupations and magnitude of natural agents, determine multiple alterations to the archaeological deposits in sheltered sites. In this paper, we present the nature and meaning of the archaeological deposits at Takarkori rock shelter, where a relatively large area has been recently excavated, showing a stratigraphic sequence extending from c. 9,000 to 4,200 BP, unevenly represented by several occupation pulses. In order to sharpen understanding of the development of human occupation at this site, specific procedures for the study and recording of the archaeological deposit have been developed, along with a program of extensive radiocarbon dating. Data from the Takarkori sequence ultimately will be integrated with available published stratigraphies from the Acacus Mountains, with the aim of reviewing the results from past excavations.

Sediment Transport and Bedrock Erosion by Wet Snow Avalanches in the Guggigraben, Matter Valley, Switzerland

Wet snow avalanches breaking through to the base of the snowpack or overriding snowfree surfaces can entrain basal material and act as important agents of sediment transport in steep alpine catchments. Here we present results from 4 years of measurements at the Guggigraben catchment (Matter Valley, Canton Valais), quantifying the volume of sediment transported by avalanches each winter season. Sediment load was estimated by measuring the debris content within representative areas and then extrapolating the cumulative volume. Results reveal a total transported sediment volume of 70 m3 in 2009, 23 m3 in 2010, 15 m3 in 2011, and 35 m3 in 2012, which correspond to catchment-wide erosion rates of approximately 0.05, 0.02, 0.01, and 0.03 mm/a, respectively. Sediment appears to be sourced predominantly from within the main channel or one its tributaries, originating first from rockfall or landslides. Avalanches thus play an important role at the Guggigraben in transporting loose sediment from temporary storage sites to the fan and main river system. Within the bedrock gully and in the avalanche source region above, signs of abrasive wear were evident on exposed bedrock surfaces. These included rounded and scoured bedrock, fresh boulder impacts, and scratch marks on the gully walls.

Mode misidentification in Rayleigh waves: Ellipticity as a cause and a cure

The surface wave method is a popular tool for geotechnical characterization because it supplies a cost-effective testing procedure capable of retrieving the shear wave velocity structure of the near-surface. Several acquisition and processing approaches have been developed to infer the Rayleigh wave dispersion curve which is then inverted. Typically, in active testing, single-component vertical receivers are used. In most cases, the inversion is carried out assuming that the experimental dispersion curve corresponds to a single mode, mostly the fundamental Rayleigh mode, unless clear evidence dictates the existence of a more complex response, e.g., in presence of low-velocity layers and inversely dispersive sites. A correct identification of the modes is essential to avoid serious errors. Here we consider the typical case of higher-mode misidentification known as “osculation” (“kissing”), where the energy peak shifts at low frequencies from the fundamental to the first higher mode. This jump occurs, with a continuous smooth transition, around a well-defined frequency where the two modes get very close to each other. Osculation happens generally in presence of strong velocity contrasts, typically with a fast bedrock underlying loose sediments. The practical limitations of the acquired active data affect the spectral and modal resolution, making it often impossible to identify the presence of two modes. In some cases, modes have a very close root and cannot be separated at the osculation point. In such cases, mode misidentification can create a large overestimation of the bedrock velocity and a large error on its depth. We examine the subsoil conditions that can generate this unwanted condition, and the common field acquisition procedures that can contribute to producing data having such deceptive Rayleigh dispersion characteristics. This mode misidentification depends strongly on the usual approach of measuring only the vertical component of ground motion, as the mode osculation is linked to the Rayleigh wave ellipticity polarization, and therefore we conclude that multicomponent data, using also horizontal receivers, can help discern the multimodal nature of surface waves. Finally, we introduce a priori detectors of subsoil conditions, based on passive microtremor measurements, that can act as warnings against the presence of mode osculation, and relate these detectors to the frequencies at which dispersion curves can be misidentified. Theoretical results are confirmed by real data acquisition tests.

The Janda cavity at Fruška Gora, the first cave assemblage from the southeast Pannonian lowland (Vojvodina, Serbia)

The recently discovered Janda cavity yielded the first large mammal fossil assemblage of the Late Pleistocene age in the southeast Pannonian lowland (Vojvodina), outside the karst region of Serbia. The cavity is formed in the Badenian reef limestone on the northern hillside of the Fruška Gora mountain. The paper provides a paleontological description and taphonomic data on mammal remains collected from the loose sediments or scree. Herbivores are represented by Bison priscus (Bojanus, 1827), which is the most abundant species, followed by Megaloceros giganteus (Blumenbach, 1803) and Equus germanicus Nehring, 1884, with several remains of Mammuthus sp. and Coelodonta antiquitatis (Blumenbach, 1799). Carnivores are represented by Ursus spelaeus ingressus (Rabeder et al., 2004), Crocuta crocuta spelaea (Goldfuss, 1823), Panthera leo spelaea (Goldfuss, 1810), as well as Canis lupus Linnaeus, 1758. Wolf remains are characterized by their large size, almost reaching the size of hyenas, which is in contrast with the finds of rather small Pleistocene wolves from the caves in the mountainous part of Serbia. The faunal composition and the presence of mostly grazing forms among the herbivores indicate glacial conditions and an open landscape in the surroundings of the site during the formation of the Janda cavity infill. Taphonomic observations indicate the cave hyena as a dominant bone accumulating agent. In contrast to other cave hyena sites in Serbia, where mostly small and medium sized prey remains were accumulated, prey preference for large and extra large mammals is noted. It is supposed that this is the consequence of the differences between mountainous and lowland landscapes and environments, climatic conditions, different composition of animal and plant associations, and also in different modes of competitions between predators.

Bucket structure in carbonate accumulations of the Maldive, Chagos and Laccadive archipelagos

Peritidal platforms rimmed by reefs, and raised reefs rimming deep lagoons, are characteristic morphologies of the tropical carbonate factory; their geometry contrasts sharply with the seaward-sloping shelves of siliciclastic margins. The structure has been compared to a bucket—stiff reef rims holding a pile of loose sediment. Remote-sensing data from the Maldive, Chagos and Laccadive archipelagos of the Indian Ocean show that ring reefs with bucket structure are the dominant depositional pattern from patch reefs of tens of meters to archipelagos of hundreds of kilometers in diameter, that is, over more than 4 orders of magnitude in linear size. Over 2.5 orders of magnitude, the bucket structures qualify as statistical fractals, exhibiting self-similar patterns and size distributions following power laws. However, most regional or genetic subsets of the data follow lognormal distributions and small subsets of lagoon reefs exhibit exponential distributions. Seismic data and boreholes in the Maldives indicate that the bucket has been a dominant depositional motif since the Oligocene. Ecological and hydrodynamic studies on modern reefs suggest that the bucket structure is a form of biotic self-organization: the edge position in a reef is favored over the center position because bottom shear is higher and the diffusive boundary layer between reef and water thinner. Thus, the reef edge has easier access to nutrients and is less likely to be buried by sediment. The bucket structure reflects these conditions. Karst processes have accentuated the surface relief of the buckets, particularly in the late Quaternary.

Archaeological sites of the Süttő Travertine Complex (Hungary) with stratigraphical and paleoecological implications from their faunas

The Süttő Travertine Complex in northern Hungary is known in the geological literature for more than a century as a series of paleontological sites. This site is one of the largest travertine occurrences of the Gerecse Hills. Loose Upper Pleistocene eolian sediments (mainly Riss-Würmian loess and Holocene topsoil) cover the eroded surface of the travertine. Beside vertebrate assemblages, two archaeological sites were described from this area. One (Süttő-Diósárok) was a Paleolithic fire pit situated in the road cut between Süttő and the quarries, while the other one was discovered in a fissure of the northern wall of Diósvölgy Quarry. The latter is part of the Süttő 1 vertebrate site.Vértes (1965) referred the artifacts from Süttő-Diósárok to the Moustérian (Tata Culture). This site is referred here to MIS 5c, based on the vertebrate and snail faunas representing warm and dry climate, and steppe-like vegetation, as well as the tool-bearing dark brown chernozem-like paleosol layer of the loess–paleosol sequence, with a luminescence age of 93.7 ± 21.1 ka.Artificially fractured bones were excavated from the small cavity of Süttő 1. Some of those remains display toolmarks. Unfortunately, these bones are currently missing from the collection. The latter artifacts most likely belong to a level which pre-dates the Tata Culture. Paleoecological inferences based on the mammalian and mollusc faunas indicated warm, humid climate and forest vegetation, therefore suggesting a stratigraphic correlation of Süttő 1 with the Eemian interglacial (MIS 5e).

Estimation of water retention parameters from nuclear magnetic resonance relaxation time distributions

[1] For characterizing water flow in the vadose zone, the water retention curve (WRC) of the soil must be known. Because conventional WRC measurements demand much time and effort in the laboratory, alternative methods with shortened measurement duration are desired. The WRC can be estimated, for instance, from the cumulative pore size distribution (PSD) of the investigated material. Geophysical applications of nuclear magnetic resonance (NMR) relaxometry have successfully been applied to recover PSDs of sandstones and limestones. It is therefore expected that the multiexponential analysis of the NMR signal from water-saturated loose sediments leads to a reliable estimation of the WRC. We propose an approach to estimate the WRC using the cumulative NMR relaxation time distribution and approximate it with the well-known van-Genuchten (VG) model. Thereby, the VG parameter n, which controls the curvature of the WRC, is of particular interest, because it is the essential parameter to predict the relative hydraulic conductivity. The NMR curves are calibrated with only two conventional WRC measurements, first, to determine the residual water content and, second, to define a fixed point that relates the relaxation time to a corresponding capillary pressure. We test our approach with natural and artificial soil samples and compare the NMR-based results to WRC measurements using a pressure plate apparatus and to WRC predictions from the software ROSETTA. We found that for sandy soils n can reliably be estimated with NMR, whereas for samples with clay and silt contents higher than 10% the estimation fails. This is the case when the hydraulic properties of the soil are mainly controlled by the pore constrictions. For such samples, the sensitivity of the NMR method for the pore bodies hampers a plausible WRC estimation.Citation: Costabel, S., and U. Yaramanci (2013), Estimation of water retention parameters from nuclear magnetic resonance relaxation time distributions, Water Resour. Res., 49, 2068-2079, doi:10.1002/wrcr.20207.

Fusion of multi‐resolution surface (terrestrial laser scanning) and subsurface geodata (ERT, SRT) for karst landform investigation and geomorphometric quantification

ABSTRACTA multi‐method research design based on terrestrial laser scanning, GIS, geophysical prospecting (electrical resistivity tomography, refraction seismics) and sedimentology is applied for the first time to investigate enclosed karst depressions in an integrated way. Fusing multi‐resolution surface and subsurface geodata provides profound insights into the formation, geometry and geomorphologic processes of dolines. The studied landforms, which are located in the Dikti Mountains of East Crete, are shown to be filled by loose sediments of thicknesses of up to 30 m that mainly consist of fine‐grained material overlying solid bedrock at depths below 35 to 45 m. By combining subsurface observations with geomorphometric calculations, local doline genesis can be traced back to initial collapse of fractured bedrock followed by subsequent infilling with colluvials. In order to define crucial methodological requirements and guidelines for data fusion, both the impact of different elevation models and the influence of data resolution are assessed. Surface volumes of depressions derived by the digital surface model are 7–21% higher than the results obtained from the terrain model due to vegetation. Similarly, estimates of infill volume calculated on the basis of geophysical outcomes and elevation data differ by up to 13%. Calculations of the landforms' current volumes (i.e. total surface and subsurface volume), however, are fairly insensitive to raster resolution. Hence, the distinct geomorphologic properties of landforms (e.g. shape, terrain roughness, slope inclination) substantially determine the geomorphometric analysis of both surface and subsurface data. As shown by the findings, data fusion to integrate digital terrain, geophysical and sedimentological datasets of varied resolutions benefits geomorphologic studies and helps provide a comprehensive image of landforms. Copyright © 2013 John Wiley & Sons, Ltd.

Traces of paleoearthquakes in the Quaternary deposits of intermontane basins in central Gorny Altai

Study of the sections of Neopleistocene–Holocene deposits filling the basins in central Gorny Altai has revealed earthquake-induced soft-sediment deformation (seismites). They formed as a result of the brittle deformation of deposits and liquefaction of loose water-saturated sediments under vibration seismic impact. The paleoearthquakes resulting in such seismites had the minimum intensity I = 6 and magnitude M = 5–6. Hence, the study region underwent strong earthquakes in the Neopleistocene–Holocene.

Pitfalls, traps, and webs in ichnology: Traces and trace fossils of an understudied behavioral strategy

The trapping of prey, where predators use external resources to help capture prey, is a specialized type of feeding behavior that is identified in the trace fossil record only rarely. Trapping traces that have been reported in the literature include spider webs, ant-lion burrows, scorpion pits, cerianthid tube anemone burrows, echiuran worm burrows, polychaete worm (Paraonis) burrows, and deep-sea graphoglyptids burrows. There is uncertainty, however, if all of these examples actually represent traps. Paraonis burrows, for example, have been represented as trapping traces, but there is a question if they actually represent this kind of behavioral strategy. Previous references and new field work indicate that Paraonis likely employs a selective deposit feeding strategy. In the fossil record, most of the known trapping traces are represented by spider webs, which are preserved in amber, and graphoglyptid burrows. Trace fossils that could represent trapping strategies may exhibit some basic morphological attributes, including (1) a conical depression composed of loose sediment; (2) an open pit; (3) a physical snare composed of a sticky substance; and/or (4) adequate spacing between the burrows, pits, or snare material without much overlapping. The interpretation that at least some graphoglyptids (e.g., Spirorhaphe) represent trapping was based on a trapping model for Paraonis, but since Paraonis does not trap prey, the question arises whether graphoglyptids should be considered trapping at all. The variety of graphoglyptid morphologies supports the idea that graphoglyptids were not all doing the same thing. Previously, the ethological category of agrichnia has been applied to graphoglyptids and has been used to denote both trapping and farming behaviors, although the two behaviors display distinctly different feeding strategies. Some graphoglyptids may represent farming traces, while others may represent trapping traces, but it is unlikely that an individual burrow represented both behaviors. The new behavioral category ‘irretichnia’ is proposed here to encompass trapping trace fossils, due to its unique behavioral significance and also to separate trapping from farming.

Particle-Clustering Algorithms for the Prediction of Brownout Dust Clouds

Particle-clustering methods have been explored for application to the problem of predicting brownout conditions, which can occur when a rotorcraft operates over surfaces covered with loose sediment and stirs up large dust clouds that impede the pilot’s outward visibility. A significant issue in such simulations is the tracking of the very large number of particles needed to predict with acceptable fidelity the dual-phase flow properties and optical characteristics of the dust clouds. To this end, computationally efficient Lagrangian approaches were explored for the simulation of dilute carrier-particle suspensions at low Reynolds numbers of the relative particle motion. The algorithms examined were the Gaussian method, the k-means method, and Osiptsov’s method, which were all compared in terms of their accuracy versus computational cost against solutions obtained by directly solving for the individual particle motions. Specific results were computed for a prototypical flowfield that mimics the highly unsteady, two-phase vortical particle flow responsible for the development of brownout conditions. It is shown that although clustering algorithms can be problem dependent and have bounds of applicability, in some conditions they offer the potential to significantly reduce the computational costs of brownout dust cloud simulations while still retaining good accuracy.

Population ecology of the tonguefish Symphurus thermophilus (Pisces; Pleuronectiformes; Cynoglossidae) at sulphur-rich hydrothermal vents on volcanoes of the northern Mariana Arc

Flatfish are a major component of the hydrothermal vent community on three seamounts of the northern Mariana Volcanic Arc in the northwest Pacific. Nikko, Kasuga-2 and Daikoku seamounts host vent fields between 375 and 480m depth where high temperature vents release molten sulphur. The small cynoglossid tonguefish, Symphurus thermophilus Munroe and Hashimoto, is ubiquitous in all vent habitats observed on these seamounts: among extensive fields of tubeworms and mussels and on solid sulphur surfaces on Nikko; on sulphur-rich sediments and barnacle-covered boulders on Kasuga-2; and on recent sulphur flows and on broad areas of loose and semi-consolidated sediments on Daikoku. We recorded repeated forays by individuals onto flows of molten sulphur as these surfaces cooled. Based on observations using ROVs, the mean density is 90fish/m2 with maximum counts over 200fish/m2 on Daikoku sediments. Compared to collected tonguefish from Daikoku and Kasuga-2, those from Nikko have significantly greater lengths and, on average, six times the mass. Otolith data indicate upper ages of 13 years with Nikko tonguefish growing significantly faster. Diets of tonguefish on the three seamounts reflect the different habitats and prey availability; in Daikoku specimens, small crustaceans and polychaetes are most common while on Nikko, gut contents are predominantly larger shrimp. We made the unusual observation of stunned midwater fish falling to the seafloor near the vents where S. thermophilus immediately attacked them. This tonguefish has a wide diet range and foraging behaviour that likely influence the differing growth rates and sizes of fish inhabiting the different vent sites. Limited genetic data suggest that larval exchange probably occurs among sites where the common habitat factor is high levels of elemental sulphur forming hard and partly unconsolidated substrata. Here, in the northern range of the Mariana Trench Marine National Monument, S. thermophilus, despite having an unusually broad habitat association, may be restricted in its overall range to this region of isolated volcanoes with active hydrothermalism.

Response of bottom sediment stability after carp removal in a small lake

This study combined several features of acoustic and electromagnetic (EM) waves-based devices including sub-bottom profiler (SBP), side-scan sonar (SSS) and ground penetrating radar (GPR), and in situ sediment data to study responses of bottom sediments after carp removal in Lake Wingra. In 2007, i.e., before carp removal, macrophytes only grew to a water depth of 2 m. Meanwhile, GPR data showed no visible sublayer in vegetated regions, while SBP data revealed a loose and fluffy sediment layer in unvegetated re- gions, easily affected by wave or current motions. The field data showed that suspended sediment concentra- tions (SSC) were much greater in unvegetated regions than those in vegetated regions during a one-day wind event, and the resuspended sediments could remain suspended in the water column for two days. In 2009, i.e., after more than half (51%) of carp were removed, the fluffy sediment layer recognized by SBP became thinner or even disappeared, and both SBP and SSS results showed that submerged macrophytes started growing in deeper water. In situ sediment data presented that bulk sediment density and critical shear stress became greater, and bottom sediments consolidated and were harder to be resuspended. Secchi depth collected be- tween 2008 and 2010 was greater than that in the previous 10 years, indicated clearer water state. In short, the fluffy sediment layer because of carp activities may be the main source for suspended sediments to deteriorate water quality. Removal of carp is crucial for stabilizing bottom sediment and improving water clarity in this small lake.

Subsurface characterization using seismic refraction and surface wave methods: a case of Lagos State University, Ojo, Lagos State

This study contains the finding of geophysical investigations conducted at the proposed science complex site at Lagos State University, Ojo, Lagos, Nigeria. Surface wave and seismic refraction tests are non-invasive seismic techniques and have been used to determine the shear wave velocity profile of soil deposits. The methods provide a simplified characterization of subsurface in two-dimensional (2D) (distance and depth) profiles. Seismic records obtained were processed/analyzed by Seis-Imager software to obtain one-dimensional shear wave velocity (Vs) distribution. Multiple Vs obtained were integrated and used to construct two-dimensional Vs map. The measured P- and S-wave velocities were also used to estimate Poisson’s ratio, rigidity modulus, and N-values. The study had shown that the area investigated composed mainly of loose sediments (clay formation) to the depth of 12 m with P-wave velocity ranging between 125 and 205 m/s and corresponding S-wave velocity between 60 and 100 m/s. The results presented in this study will be vital information for the engineers in construction of the proposed science complex.

Electrical resistivity tomography investigation of coseismic liquefaction and fracturing at San Carlo, Ferrara Province, Italy

<p>Massive surface fracturing and sand ejection took place during the main shock of the May 20, 2012, earthquake (Ml = 5.9) in the Emilia-Romagna region, northern Italy. These phenomena were induced by the liquefaction of water-saturated sand layers, and they damaged several buildings, as well as many roads and sidewalks. They were clustered between the villages of Sant'Agostino and Vigarano Mainarda, located along a paleo-reach of the Reno River [Papathanassiou et al. 2012, this volume]. The subsurface surrounding two major (several decameters long) ground ruptures was investigated using electrical resistivity tomographies (ERT), as resistivity is strongly affected by the chemico-physical conditions of loose sediments. Italian regulations require the Municipalities within seismically active areas to develop maps of the potential liquefaction risk. Not all of the territories that are under this kind of risk have been investigated to date. A strong effort to improve this knowledge is therefore needed. Noninvasive geophysical methods can help to fill this gap, as high-resolution techniques are available with good result-to-cost ratios. Among the available methodologies, the most suitable are the methods based on electrical resistivity and permittivity, as they are highly sensitive to the presence of underground water. The ERT method has been carried out successfully across active faults, providing crucial paleoseismological information [Caputo et al. 2003, 2007]. […]</p>

Case study of a giant debris flow in the Wenjia Gully, Sichuan Province, China

The debris flow, which was triggered in the Wenjia Gully on August 13, 2010, is an extreme example of mass movement events, which occurred after the Wenchuan earthquake of May 12, 2008. This Earthquake triggered in the Wenjia Gully the second largest co-seismic landslide, which can be classified as a rockslide-debris avalanche. A lot of loose sediments was deposited in the basin. In the main so called Deposition Area II of this landslide, with a volume of 30 × 106 m3, flash floods can easily trigger debris flows because of the steep bottom slope and the relative small grain sizes of the sediments. The largest debris flow of August 13, 2010 destroyed the most downstream dam in the catchment during a heavy rain storm. The debris flow with a peak discharge of 1,530 m3/s and a total volume of 3.1 × 106 m3 caused the death of 7 persons, 5 persons were missing, 39 persons were injured and 479 houses buried. After three rainy seasons, only 16 % of the landslide-debris deposition was taken away by 5 large-scale debris flow events. Since the threshold for rainfall triggered debris flows in the Wenjia Gully and other catchments drastically decreased after the Wenchuan Earthquake, new catastrophic events are expected in the future during the rainy season.

Field observations and modeling of wave attenuation over colonized beachrocks

Beachrocks are common coastal formations, constructed through the lithification of beach sediments by carbonate cements. The objectives of the present contribution were to (a) assess the impacts of beachrock benthic communities on nearshore wave dynamics; (b) present a numerical model, developed to simulate wave propagation over shallow nearshore waters characterized by both loose sediment beds and colonized/non-colonized beachrocks; and (c) discuss the structure and dynamics of beachrock macro-benthic communities in an E. Mediterranean micro-tidal beach (Vatera, Lesbos Island, NE Aegean Sea), as well as their interactions with the wave forcing. Field measurements of wave height and flow velocity were processed to assess shoaling wave energy dissipation due to bottom friction from the colonized beachrock outcrops. The equivalent Nikuradse hydraulic roughness of the beachrock surface, estimated through spectral wave attenuation calculations, was found to be around kN=0.13m. The corresponding wave friction factors were incorporated into a wave propagation model to obtain estimates of the wave-induced bed shear stress τw acting on the beachrock benthic communities. Information about the structure and characteristics of the latter was obtained through the collection and analysis of samples from 15 stations along a beach transect, during two months of the year (April and September) and the results showed that benthic communities at the beachrock habitat were very similar to the ones typically found at NE Mediterranean hard substrates. Wave-induced bed shear stress τw values were able to explain cross-shore variations in population density and biomass, both decreasing significantly above water depths of about h=1.8–2m. The latter values corresponded, for the studied conditions, to shear stresses of about τw=2.2Nt/m2. The present findings clearly show that nearshore wave patterns not only control to a certain extent the spatial structure of the beachrock habitats, but can be also influenced by them. Thus, hydrodynamics and beachrocks habitats constitute a complex system which remains very little understood and demands for further investigation.

Faults in Quaternary cover as a relfection of basement tectonics: Kolguev island, barents sea

The paper is concerned with the results of the detailed study of dislocations in the Pliocene-Quaternary loose sediments exposed as cliffs extending for ∼30 km along the rectilinear shore of Kolguev Island. According to seismic data, this lineament is related to the Coastal Fault in the lower part of the sedimentary cover. A system of faults longitudinal, diagonal, and transverse relative to the shoreline is established from observations at the cliffs. Their arrangement in plan view corresponds to the geometry of the right-lateral shear zone, the axis of which almost coincides with the shoreline. This has allowed us to identify the faults as secondary disturbances in the region of dynamic effect of the Coastal Fault in the basement. The kinematics of the secondary faults and their dip azimuth are consistent with echeloned geometry in plan view. The low-angle dip of the reverse-strike-slip faults observed at the outcrops is caused by their near-surface flattening toward the subsided block. The shallow-seated dislocations are related to ductile lateral shear in the vertical plane. The lower layers of the sedimentary cover mimic the horizontal movements in the basement more closely than the upper layers. The data obtained indicate high neotectonic activity of the Barents Sea shelf and specify the geodynamic setting of the region in the Pliocene and Quaternary.

Operational performance of inlet barrier filters for rotorcraft

AbstractThis contribution addresses the subject of engine inlet barrier filters (IBF) for rotorcraft. The purpose of an IBF is to mitigate the risk of particle ingestion by the engine, a situation that can cause irrevocable damage to key components. The risk is significantly elevated during a brownout landing, in which the rotor wake of a descending helicopter interacts with loose ground sediment, causing the generation of a dust cloud. In such a condition, an IBF successfully removes particles from the engine-bound air at the expense of a pressure drop, which grows temporally. The increase in pressure drop is caused by but not limited to an increase in incident velocity and a decrease of mean particle size; however the rate may be slowed by operating the filter at a tangential angle to the flow. The current work presents findings of a parametric study into the factors affecting particle accumulation and the consequential loss of inlet total pressure.

Mineralogical and geochemical studies of glacial sediments from Schirmacher Oasis, East Antarctica

Schirmacher Oasis, East Antarctica hosts loose unconsolidated sediments that consist dominantly of sand-silt admixtures with minor clay. These sediments were collected from different glacial environments such as polar ice sheets, inland lakes, exposed bedrock, and coastal shelf areas. Two sediment fractions (coarse 0.25–0.125 mm and fine 0.125–0.063 mm) were separated and chemically analyzed. Mineralogically, the mixture is composed dominantly of quartz and feldspar, and a large variety of heavy minerals: zircon, tourmaline, rutile, garnet, hornblende, hypersthene, enstatite, kyanite, sillimanite, andalusite, zoisite, lawsonite, chlorite, spinel, topaz, and opaques. The clay minerals i.e., chlorite, illite, smectite, kaolinite, and vermiculite constitute a small fraction. There is a mineralogical control over the observed geochemical patterns and anomalies of these sediments. The rare earth element and incompatible trace element spidergrams show relative enrichment in the coarse fraction as against fine fraction, indicating enrichment of the carrier minerals of these elements (mostly heavy minerals) in the coarse fraction. The overall geochemistry of the sediments classifies them as greywacke as per Lindsey, Fe-sand to arenite as per Herron, and sodic sandstones as per Blatt et al. These sediments show quartzose sedimentary provenance, but influence of other unknown sources is also discernible. Transporting agencies for the sediments are commonly meltwater channels and wind. However, transport under influence of gravity, glacier action and sea waves are also envisaged. The sediments have undergone low degrees of chemical weathering ranging between incipient and moderate types.