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Geosciences, Volume 10, Issue 3 (March 2020) – 29 articles

Cover Story (view full-size image): Egypt is the land of dunes. Investigations of satellite images and field measurements show that nearly all dune forms can be observed. Longitudinal dunes and barchans prevail. The study reviews the state of knowledge around distribution, sizes, dynamics, and ages of all six sand seas (large areas with more than 50% dune coverage) and ten dune fields in Egypt. Regarding the sparse chronological data to date, for a reasonable estimation of future sand mobility in the course of global climate change, further data are essential. Finally, further studies concerning sand mobility, local wind systems, and land use are needed. View this paper
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Article
Effects of Earthquakes on Flood Hazards: A Case Study From Christchurch, New Zealand
Geosciences 2020, 10(3), 114; https://doi.org/10.3390/geosciences10030114 - 23 Mar 2020
Cited by 4 | Viewed by 1708
Abstract
Earthquakes can influence flood hazards by altering the flux, volumes, and distributions of surface and/or subsurface waters and causing physical changes to natural and engineered environments (e.g., elevation, topographic relief, permeability) that affect surface and subsurface hydrologic regimes. This paper analyzes how earthquakes [...] Read more.
Earthquakes can influence flood hazards by altering the flux, volumes, and distributions of surface and/or subsurface waters and causing physical changes to natural and engineered environments (e.g., elevation, topographic relief, permeability) that affect surface and subsurface hydrologic regimes. This paper analyzes how earthquakes increased flood hazards in Christchurch, New Zealand, using empirical observations and seismological data. Between 4 September 2010 and 4 December 2017, this region hosted one moment magnitude (Mw) 7.1 earthquake, 3 earthquakes with Mw ≥ 6, and 31 earthquakes with local magnitude (ML) ≥ 5. Flooding related to liquefaction-induced groundwater pore-water fluid pressure perturbations and groundwater expulsion occurred in at least six earthquakes. Flooding related to shaking-induced ground deformations (e.g., subsidence) occurred in at least four earthquakes. Flooding related to tectonic deformations of the land surface (fault surface rupture and/or folding) occurred in at least two earthquakes. At least eight earthquakes caused damage to surface (e.g., buildings, bridges, roads) and subsurface (e.g., pipelines) infrastructure in areas of liquefaction and/or flooding. Severe liquefaction and associated groundwater-expulsion flooding in vulnerable sediments occurred at peak ground accelerations as low as 0.15 to 0.18 g (proportion of gravity). Expected return times of liquefaction-induced flooding in vulnerable sediments were estimated to be 100 to 500 years using the Christchurch seismic hazard curve, which is consistent with emerging evidence from paleo-liquefaction studies. Liquefaction-induced subsidence of 100 to 250 mm was estimated for 100-year peak ground acceleration return periods in parts of Christchurch. Full article
(This article belongs to the Special Issue Scientific Assessment of Recent Natural Hazard Events)
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Article
Estimation of Avalanche Development and Frontal Velocities Based on the Spectrogram of the Seismic Signals Generated at the Vallée de la Sionne Test Site
Geosciences 2020, 10(3), 113; https://doi.org/10.3390/geosciences10030113 - 21 Mar 2020
Cited by 3 | Viewed by 914
Abstract
The changes in the seismic signals generated by avalanches recorded at three sites along a path at the Vallée de la Sionne (VdlS) experimental site are presented. We discuss and correlate the differences in the duration, signal amplitudes, and frequency content of the [...] Read more.
The changes in the seismic signals generated by avalanches recorded at three sites along a path at the Vallée de la Sionne (VdlS) experimental site are presented. We discuss and correlate the differences in the duration, signal amplitudes, and frequency content of the sections (Signal ONset (ON), Signal Body (SBO), and Signal TAil and Signal ENd STA-SEN) of the spectrograms with the evolution of the powder, transitional and wet snow avalanches along a path. The development of the avalanche front was quantified using the exponential function in time F (t) = K’ exp (β t) fitted to the shape of the signal ONset (SON section of the spectrogram. The speed of the avalanche front is contained in β. To this end, a new method was developed. The three seismic components were converted into one seismic component (FS), when expressing the vector in polar coordinates. We linked the theoretical function of the shape of the FS-SON section of the spectrogram to the numerical coefficients of its shape after considering the spectrogram as an image. This allowed us to obtain the coefficients K’ and β. For this purpose, the Hough Transform (HT) was applied to the image. The values of the resulting coefficients K’ and β are included in different ranges in accordance with the three types of avalanche. Curves created with these coefficients enable us to estimate the development of the different avalanche types along the path. Our results show the feasibility of classifying the type of avalanche through these coefficients. Average speeds of the avalanches approaching the recording sites were estimated. The speed values of wet and transitional avalanches are consistent with those derived from GEODAR (GEOphysical Doppler radAR) measurements, when available. The absence of agreement in the speed values obtained from seismic signals and GEODAR measurements for powder snow avalanches indicates, for this type of avalanche, a different source of the measured signal. Hence, the use of the two measuring systems proves to be complementary. Full article
(This article belongs to the Special Issue Snow Avalanche Dynamics)
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Article
Investigation of Dimension Stone on the Island Brač—Geophysical Approach to Rock Mass Quality Assessment
Geosciences 2020, 10(3), 112; https://doi.org/10.3390/geosciences10030112 - 21 Mar 2020
Cited by 2 | Viewed by 1088
Abstract
A site located on the island of Brač is known in history for world-famous architectural stone and stone mining, dating all the way back to ancient Greek and Roman times. The most famous building constructed from the stone from Brač is the Diocletian [...] Read more.
A site located on the island of Brač is known in history for world-famous architectural stone and stone mining, dating all the way back to ancient Greek and Roman times. The most famous building constructed from the stone from Brač is the Diocletian Cesar Palace in the town Split. Prospective new locations for quarries are still required because the demand for the stone from the island is still high. This paper presents a review of undertaken geophysical investigations, as well as engineering geologic site prospection, with the purpose of determining if the rock mass quality is suitable for the mining of massive blocks needed for an architectural purpose—dimension stones. Several surface noninvasive geophysical methods were applied on the site, comprising of two seismic methods, multichannel analysis of surface waves (MASW) and shallow refraction seismic (SRS) electrical methods of electrical resistivity tomography (ERT), as well as electromagnetic exploration with ground penetrating radar (GPR). Results of geophysical investigations were compared to the engineering geologic prospection results, as well to the visible rock mass structure and observed discontinuities on the neighboring existing open mine quarry. Rock mass was classified into three categories according to its suitability for dimension stone exploitation. Each category is defined by compressional and shear seismic velocities as well as electrical resistivity. It has been found that even small changes in moisture content within the large monolithic rock mass can influence measured values of electrical resistivity. In the investigated area, dimension stone quarrying is advisable if the rock mass has values of resistivity higher than 3000 Ωm, as well as compressional seismic velocities higher than 3000 m/s and shear wave velocities higher than 1500 m/s. Georadar was found to be a good tool for the visual determination of fissured systems, and was used to confirm findings from other geophysical methods. Full article
(This article belongs to the Special Issue Modern Surveying and Geophysical Methods for Soil and Rock)
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Article
A New Landslide Inventory for the Armenian Lesser Caucasus: Slope Failure Morphologies and Seismotectonic Influences on Large Landslides
Geosciences 2020, 10(3), 111; https://doi.org/10.3390/geosciences10030111 - 20 Mar 2020
Viewed by 1891
Abstract
Landslide hazard analyses in Armenia require consideration of the seismotectonic context of the Lesser Caucasus. As it is located near the center of the Arab-Eurasian collision, the Lesser Caucasus is characterized by its complex geology, dense fault network and mountainous relief; it is [...] Read more.
Landslide hazard analyses in Armenia require consideration of the seismotectonic context of the Lesser Caucasus. As it is located near the center of the Arab-Eurasian collision, the Lesser Caucasus is characterized by its complex geology, dense fault network and mountainous relief; it is marked by recent volcanic and seismic activity largely influencing slope stability at different scales. We therefore sought to identify all major landslides in the Armenian Lesser Caucasus and to understand the environmental factors contributing to regional landslide susceptibility. We performed spatial and size-frequency analyses using two landslide catalogues as inputs: “Georisk”, provided by the Georisk Scientific Research Company, and “Matossian”, herein. Our spatial analyses show that landslide susceptibility depends on many factors according to the area considered: near faults, a tectonic influence on slope stability is clearly observable, whereas high concentrations of landslides in northern mountain regions, marked by a wetter climate and far from known active faults, show that climatic factors also strongly contribute to slope-failure potential. The influence of volcanoes and volcanic deposits on the development of mass movements is unclear and requires further analysis. The aforementioned inventories do not include any records of volcanic flank collapses, although we expect at least one case in the eastern Lesser Caucasus. Full article
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Article
The Effect of Targeted Field Investigation on the Reliability of Earth-Retaining Structures in Passive State: A Random Field Approach
Geosciences 2020, 10(3), 110; https://doi.org/10.3390/geosciences10030110 - 20 Mar 2020
Cited by 2 | Viewed by 716
Abstract
In one of their recent works, the authors examined parametrically the effect of targeted field investigation on reducing statistical uncertainty in active state analysis of earth retaining structures based on 2165 different cases for each of the sliding and overturning modes of failure. [...] Read more.
In one of their recent works, the authors examined parametrically the effect of targeted field investigation on reducing statistical uncertainty in active state analysis of earth retaining structures based on 2165 different cases for each of the sliding and overturning modes of failure. This analysis indicates that the optimal sampling location is always adjacent to the wall, while a sampling domain length equal to the whole height of the wall is suggested to be considered. The present paper deals with the “symmetrical” problem of soil under the passive state of stresses. Working in a similar manner, 1879 passive state cases have been considered (also for each of the sliding and overturning modes of failure) in a Random Finite Element Method (RFEM) analysis framework, where soil properties are modeled as random fields while measurements are modeled by sampling from different points of the field domain. The “actual” resultant earth passive pressure force (or moment) exerted by the random soil on the retaining wall is compared against the respective “predicted” one calculated using the soil property values sampled from the random field. Failure is considered to have occurred when the derived “actual” force is smaller than the respective “predicted” force. This analysis clearly indicates that the passive state constitutes a different problem, where the optimal sampling distance from the wall is half the wall height. Regarding the depth of exploration, it was again found to be the entire wall height. In addition, the present analysis shows that, the benefit from a targeted field investigation is much greater than the benefit gained using statistical methods for obtaining cautious estimates for the various soil properties; the latter refers to the “characteristic value”, a concept commonly used in the Limit State analysis framework of Eurocode 7. Full article
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Article
Assessment of Geological, Hydrogeological and Geotechnical Characteristics of a Proposed Waste Disposal Site: A Case Study in Khon Kaen, Thailand
Geosciences 2020, 10(3), 109; https://doi.org/10.3390/geosciences10030109 - 18 Mar 2020
Cited by 3 | Viewed by 874
Abstract
Occasionally, a selected site suitable for landfill construction is severely protested against by locals. This issue can cause the proposed landfill to be relocated to an environmentally sensitive area. The proposed Khon Kaen waste disposal site has been planned as an integrated municipal [...] Read more.
Occasionally, a selected site suitable for landfill construction is severely protested against by locals. This issue can cause the proposed landfill to be relocated to an environmentally sensitive area. The proposed Khon Kaen waste disposal site has been planned as an integrated municipal solid waste management system, although the site is situated in an environmentally sensitive area. A site assessment can guarantee the suitability of waste disposal construction, with procedures that aim to assess the potential of geological and hydrogeological characteristics, geological barriers, geotechnical properties of material for landfill construction and groundwater conditions for future monitoring of such facilities. The study area is located on foothills where no geohazard or seismic impacts have been recorded. The geology is composed of sandstone, siltstone, and mudstone bedrocks mostly overlain by unconsolidated sediments. The natural geological barriers are clay and regolith. The clay layer lies locally and is rather thin, at around 2–3 m thickness. The study area is situated in an area that is highly vulnerable to groundwater pollution. The distinct weaknesses of this site along the foothill are a prominent transport path of shallow flows; high groundwater fluctuation, especially during the rainy season; that it is a recharge area with a high fracture zone; and the high permeability of colluvium. The material characteristics in the site make it suitable for use as landfill cover and liner. Following compaction, the coefficient of permeability ranges from 1.2 × 10−7 to 7.1 × 10−7 cm/s, which is acceptably impervious. Full article
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Article
Seismic Exploration of the Deep Structure and Seismogenic Faults in the Ligurian Sea by Joint Multi Channel and Ocean Bottom Seismic Acquisitions: Preliminary Results of the SEFASILS Cruise
Geosciences 2020, 10(3), 108; https://doi.org/10.3390/geosciences10030108 - 18 Mar 2020
Viewed by 968
Abstract
The north Ligurian margin is a complex geological area in many ways. It has witnessed several phases of highly contrasting deformation styles, at both crustal scale and that of shallower cover tectonics, simultaneously or in quick succession, and with significant spatial variability. This [...] Read more.
The north Ligurian margin is a complex geological area in many ways. It has witnessed several phases of highly contrasting deformation styles, at both crustal scale and that of shallower cover tectonics, simultaneously or in quick succession, and with significant spatial variability. This complex interplay is mirrored in the resulting intricate structures that make it hard to identify active faults responsible for both, the significant seismicity observed, and the tectonic inversion undergone by the margin, identified at longer time scales on morphostructural grounds. We present here the first preliminary results of the leg 1 of SEFASILS cruise, conducted in 2018 offshore Monaco, in an effort to answer these questions by means of modern deep seismic acquisitions, using multichannel reflection and wide-angle sea-bottom records. Some first interpretations are provided and point towards an active basement deformation that focuses at the limits between main crustal domains. Full article
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Article
Mineralogical and Chemical Investigations of the Amguid Crater (Algeria): Is there Evidence on an Impact Origin?
Geosciences 2020, 10(3), 107; https://doi.org/10.3390/geosciences10030107 - 18 Mar 2020
Viewed by 1366
Abstract
Mineralogical and chemical investigations were carried out on intra-craterial bedrocks (Lower Devonian sandstone) and regolithic residual soil deposits present around the Amguid structure, to discuss the hypothesis of its formation through a relatively recent (about 0.1 Ma) impact event. Observations with an optical [...] Read more.
Mineralogical and chemical investigations were carried out on intra-craterial bedrocks (Lower Devonian sandstone) and regolithic residual soil deposits present around the Amguid structure, to discuss the hypothesis of its formation through a relatively recent (about 0.1 Ma) impact event. Observations with an optical microscope on intra-craterial rocks do not unequivocally confirm the presence of impact correlated microscopic planar deformation features (PDFs) in quartz crystals. Field observations, and optical and instrumental analysis (Raman spectroscopy) on rocks and soils (including different granulometric fractions) do not provide any incontrovertible pieces of evidence of high energy impact effects or products of impact (e.g., high pressure—temperature phases, partially or totally melted materials, etc.) either in target rocks or in soils. A series of selected main and trace elements (Al, Fe, Mg, Ni, Co and Cu) were analysed on rocks and soils to evaluate the presence in these materials of extraterrestrial sources. Comparative chemical data on rocks and soils suggest that these last are significantly enriched in Fe-poor Mg-rich materials, and in Co, Ni and Cu, in the order. A large number of EDAX-SEM analyses on separated soil magnetic particles indicate an abnormally high presence of Al-free Mg-rich sub-spherical or drop-like silicate particles, showing very similar bulk chemistries compatible with forsterite olivine. Some particles were found associated with a Ni-rich iron metal phase, and this association suggests a specific extraterrestrial origin for them. Electron microscope analysis made on a large number of soil magnetic particles indicates that 98% of them are terrestrial phases (almandine garnet, tourmaline and Fe-oxides, in abundance order), whereas, only a few grains are of questionable origin. One of the Mg-rich silicate particles was found to be a forsterite (Mg = 0.86) Mn-rich (MnO: 0.23%) Cr-free olivine, almost surely of extraterrestrial sources. Electron microprobe analysis of three soil particles allowed identification of uncommon Cr-rich (Cr2O3 about 8%) spinels, poorly compatible with an origin from terrestrial sources, and in particular from local source rocks. We propose a specific extraterrestrial origin for sub-spherical olivine particles characterised by quite similar magnesian character. Excluding any derivation of these particles from interplanetary dust, two other possible extraterrestrial sources should be considered for them, i.e., either normal micrometeorite fluxes or strongly un-equilibrated, or the Vigarano type Carbonaceous (CV) chondrite meteorite material. In this case, further studies will confirm an impact origin for Amguid, as such magnesian olivine components found in soils might represent the only remnants of a vaporised projectile of ordinary non-equilibrated meteoritic composition. Full article
(This article belongs to the Special Issue 2020: A 10 Years Journey-Advances in Geosciences)
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Article
Assessment of Burned Forest Area Severity and Postfire Regrowth in Chapada Diamantina National Park (Bahia, Brazil) Using dNBR and RdNBR Spectral Indices
Geosciences 2020, 10(3), 106; https://doi.org/10.3390/geosciences10030106 - 18 Mar 2020
Cited by 2 | Viewed by 1421
Abstract
Fire scar detection through orbital data can be done using specific techniques, such as the use of spectral indices like the normalized burn ratio (NBR), which are designed to help identify burnt areas as they have typical spectral responses. This paper aims to [...] Read more.
Fire scar detection through orbital data can be done using specific techniques, such as the use of spectral indices like the normalized burn ratio (NBR), which are designed to help identify burnt areas as they have typical spectral responses. This paper aims to characterize burn severity and regrowth in areas hit by three fires in the Chapada Diamantina National Park (Bahia, Brazil) and its surrounding area through the differenced normalized burn ratio (dNBR) and relative differenced normalized burn ratio (RdNBR) spectral indices. The data acquired were pretreated and prepared adequately to calculate the indices. We conclude that for the study area, considering the limitations of fieldwork, the multitemporal index dNBR and the relative index RdNBR are important tools for classifying burnt areas and can be used to assess the regrowth of vegetation. Full article
(This article belongs to the Special Issue Wildfires Hazards)
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Article
A Machine Learning-Based Approach for Wildfire Susceptibility Mapping. The Case Study of the Liguria Region in Italy
Geosciences 2020, 10(3), 105; https://doi.org/10.3390/geosciences10030105 - 18 Mar 2020
Cited by 15 | Viewed by 2130
Abstract
Wildfire susceptibility maps display the spatial probability of an area to burn in the future, based solely on the intrinsic local proprieties of a site. Current studies in this field often rely on statistical models, often improved by expert knowledge for data retrieving [...] Read more.
Wildfire susceptibility maps display the spatial probability of an area to burn in the future, based solely on the intrinsic local proprieties of a site. Current studies in this field often rely on statistical models, often improved by expert knowledge for data retrieving and processing. In the last few years, machine learning algorithms have proven to be successful in this domain, thanks to their capability of learning from data through the modeling of hidden relationships. In the present study, authors introduce an approach based on random forests, allowing elaborating a wildfire susceptibility map for the Liguria region in Italy. This region is highly affected by wildfires due to the dense and heterogeneous vegetation, with more than 70% of its surface covered by forests, and due to the favorable climatic conditions. Susceptibility was assessed by considering the dataset of the mapped fire perimeters, spanning a 21-year period (1997–2017) and different geo-environmental predisposing factors (i.e., land cover, vegetation type, road network, altitude, and derivatives). One main objective was to compare different models in order to evaluate the effect of: (i) including or excluding the neighboring vegetation type as additional predisposing factors and (ii) using an increasing number of folds in the spatial-cross validation procedure. Susceptibility maps for the two fire seasons were finally elaborated and validated. Results highlighted the capacity of the proposed approach to identify areas that could be affected by wildfires in the near future, as well as its goodness in assessing the efficiency of fire-fighting activities. Full article
(This article belongs to the Special Issue 2020: A 10 Years Journey-Advances in Geosciences)
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Article
Variation of Ground Temperature along the Stratum Depth in Ice-rich Tundra of Hinggan Mountains Region, NE China
Geosciences 2020, 10(3), 104; https://doi.org/10.3390/geosciences10030104 - 15 Mar 2020
Viewed by 720
Abstract
A pile foundation in a permafrost region is in a negative-temperature environment, so concrete is affected by the negative temperature of the surrounding soil. It not only affects the formation of concrete strength but also leads to engineering quality accidents in serious cases. [...] Read more.
A pile foundation in a permafrost region is in a negative-temperature environment, so concrete is affected by the negative temperature of the surrounding soil. It not only affects the formation of concrete strength but also leads to engineering quality accidents in serious cases. With the support of the two permafrost bridge projects of the national highway from Beijing to Mohe in the Greater Khingan Mountains region, a systematic remote dynamic monitoring method for ground temperature in ice-rich tundra is proposed. Based on the actual measurement of temperature at different strata depths and the comprehensive consideration of surface temperature, terrestrial heat flux and other parameters, the ground temperature profile evolution in relation to depth in Greater Khingan was established. The theoretical ground temperature profile curve is similar to the measured profile. The results show that the variation trends of ground temperatures in relation to the strata depth at different monitoring sites is similar, and all show seasonal variation: From June to November, the ground temperature at different depths tends to be constant. From December to May, the ground temperature at any depth within the range of 0 to 5.5 m follows the curve of the cosine function. Below 5.5 m, the earth temperature no longer varies with depth. The research results can be used as reference for pile foundation construction in a negative-temperature environment in ice-rich tundra. Full article
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Editorial
The Evolutionary History of the Coleoptera
Geosciences 2020, 10(3), 103; https://doi.org/10.3390/geosciences10030103 - 12 Mar 2020
Cited by 2 | Viewed by 1150
Abstract
In this Editorial, different aspects of palaeocoleopterological studies and contributions of the issue “The Evolutionary History of the Coleoptera” are discussed. Full article
(This article belongs to the Special Issue The Evolutionary History of the Coleoptera)
Article
Hydraulic Conductivity and Pore Water Pressures in a Clayey Landslide: Experimental Data
Geosciences 2020, 10(3), 102; https://doi.org/10.3390/geosciences10030102 - 12 Mar 2020
Cited by 3 | Viewed by 1037
Abstract
To analyze the response to hydrological conditions of an instable slope in a structurally complex clay formation, the hydraulic conductivity of the subsoil was estimated and pore water pressures were monitored. Two types of field tests were carried out: falling head tests in [...] Read more.
To analyze the response to hydrological conditions of an instable slope in a structurally complex clay formation, the hydraulic conductivity of the subsoil was estimated and pore water pressures were monitored. Two types of field tests were carried out: falling head tests in the Casagrande piezometers and localized seepage measurements in test boreholes. The experimental data show that in a narrow band around the slip surface, the hydraulic conductivity is higher—more than two orders of magnitude—than that of the landslide body and of the stable formation. Furthermore, the data of a long-term monitoring by Casagrande piezometers and vibrating wire cells show that the response of pore water pressures to the site hydrological conditions along the shear band is far faster than in the landslide body and in the stable formation. The slip band seems largely connected to the atmosphere, and the water pressures in the band are correlated with the deep displacement rates of all the inclinometers crossing the active slip surface. Full article
(This article belongs to the Special Issue Innovative Strategies for Sustainable Mitigation of Landslide Risk)
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Review
Sand Seas and Dune Fields of Egypt
Geosciences 2020, 10(3), 101; https://doi.org/10.3390/geosciences10030101 - 10 Mar 2020
Cited by 2 | Viewed by 1850
Abstract
The article reviews the state of knowledge about distribution, sizes, dynamics, and ages of all sand seas (N = 6) and dune fields (N = 10) in Egypt (1,001,450 km2). However, chronological data (Optically Stimulated Luminescence, Thermoluminescence), used in the INQUA [...] Read more.
The article reviews the state of knowledge about distribution, sizes, dynamics, and ages of all sand seas (N = 6) and dune fields (N = 10) in Egypt (1,001,450 km2). However, chronological data (Optically Stimulated Luminescence, Thermoluminescence), used in the INQUA (International Union for Quaternary Research) dune database, only exists from three of the five sand seas located in the Western Desert of Egypt. The North Sinai Sand Sea and four of the ten dune fields are located near the Nile Valley, the delta or the coast and therefore changed drastically due to land reclamation during the last decades. Here, but also in the oases, their sands pose a risk for settlements and farmland. Our comprehensive investigations of satellite images and our field measurements show that nearly all terrestrial dune forms can be observed in Egypt. Longitudinal dunes and barchans are dominant. Sand seas cover about 23.8% (with an average sand coverage of 74.8%), dune fields about 4.4% (with an average sand coverage of 31.7%) of its territory. For the Great Sand Sea and the Farafra Sand Sea, situated in the central and northern part of the Western Desert, a Late Glacial transformation by strong westerlies was found, but not for the Selima Sand Sea, situated in the south of Egypt. Regarding the sparse chronological data up to now, for a reasonable estimation of future sand mobility in the course of global climate change, further data are essential. Finally, further studies concerning sand mobility, local wind systems, and land use are needed. Full article
(This article belongs to the Special Issue Aeolian Processes and Geomorphology)
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Review
Hydroacoustic Mapping of Geogenic Hard Substrates: Challenges and Review of German Approaches
Geosciences 2020, 10(3), 100; https://doi.org/10.3390/geosciences10030100 - 09 Mar 2020
Cited by 3 | Viewed by 1098
Abstract
Subtidal hard substrate habitats are unique habitats in the marine environment. They provide crucial ecosystem services that are socially relevant, such as water clearance or as nursery space for fishes. With increasing marine usage and changing environmental conditions, pressure on reefs is increasing. [...] Read more.
Subtidal hard substrate habitats are unique habitats in the marine environment. They provide crucial ecosystem services that are socially relevant, such as water clearance or as nursery space for fishes. With increasing marine usage and changing environmental conditions, pressure on reefs is increasing. All relevant directives and conventions around Europe include sublittoral hard substrate habitats in any manner. However, detailed specifications and specific advices about acquisition or delineation of these habitats are internationally rare although the demand for single object detection for e.g., ensuring safe navigation or to understand ecosystem functioning is increasing. To figure out the needs for area wide hard substrate mapping supported by automatic detection routines this paper reviews existing delineation rules and definitions relevant for hard substrate mapping. We focus on progress reached in German approval process resulting in first hydroacoustic mapping advices. In detail, we summarize present knowledge of hard substrate occurrence in the German North Sea and Baltic Sea, describes the development of hard substrate investigations and state of the art mapping techniques as well as automated analysis routines. Full article
(This article belongs to the Special Issue Marine Habitat Mapping: Selected Papers from "GeoHab 2021")
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Article
Characteristics of Surface Deformation in Lanzhou with Sentinel-1A TOPS
Geosciences 2020, 10(3), 99; https://doi.org/10.3390/geosciences10030099 - 07 Mar 2020
Cited by 3 | Viewed by 1045
Abstract
While surface deformations and their impact on buildings have been observed in the city of Lanzhou, it is difficult to find studies of surface deformation and the influential factors in the recent decades. This study was designed to detect the spatial position of [...] Read more.
While surface deformations and their impact on buildings have been observed in the city of Lanzhou, it is difficult to find studies of surface deformation and the influential factors in the recent decades. This study was designed to detect the spatial position of these surface deformations and to understand the mechanism behind them. Sentinel-1A TOPS model image data acquired in descending orbits between March 2015 and May 2019 were processed by using Small Baseline Subsets Interferometry (SBAS)-Interferometric Synthetic Aperture Radar (InSAR) technology, and then compared with geology, tectonical aspects of the study area and land cover types in Lanzhou. The results reveal that the land surface deformation is uneven in this city, and seven surface deformation regions were detected in the following areas: the north freight yard, Jiuzhou, Country garden, Donggang, Yanjiaping, Zhongxinping and Liuquan town. The land surface deformation rate in Lanzhou ranges from −82.13 mm/year to 19.31 mm/year. Time-series land surface deformation analysis showed that deformation increased over time in major deformation regions. Surface deformation expansion was significant after June 2017and it continued to expand. The surface deformation of Lanzhou is affected by natural factors (geology and geological faults) and human activities (land cover types/land cover changes). Local geological conditions control the location of the surface deformation process. These findings provide compelling data and theoretical support for disaster prevention and reduction in Lanzhou. Full article
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Article
Evaluating Rockfall Risk: Some Critical Aspects
Geosciences 2020, 10(3), 98; https://doi.org/10.3390/geosciences10030098 - 03 Mar 2020
Cited by 22 | Viewed by 1468
Abstract
Rockfalls evolve rapidly and unpredictably in mountain environments and can cause considerable losses to human societies, structures, economical activities, and also natural and historical heritage. Rockfall risk analyses are complex and multi-scale processes involving several disciplines and techniques. This complexity is due to [...] Read more.
Rockfalls evolve rapidly and unpredictably in mountain environments and can cause considerable losses to human societies, structures, economical activities, and also natural and historical heritage. Rockfall risk analyses are complex and multi-scale processes involving several disciplines and techniques. This complexity is due to the main features of rockfall phenomena, which are extremely variable over space and time. Today, a considerable number of methods exists for protecting land, as well as assessing and managing the risk level. These methodologies are often very different from each other, depending on the data required, the purposes of the analysis, and the reference scale adopted, i.e., the analysis level of detail. Nevertheless, several questions still remain open with reference to each phase of the hazard and risk process. This paper is devoted to a general overview of existing risk estimation methodologies and a critical analysis of some open questions with the aim of highlighting possible further research topics. A typical risk assessment framework is exemplified by analyzing a real case study. Each step of the process is treated at both the detailed and the large scale in order to highlight the main characteristics of each level of detail. Full article
(This article belongs to the Special Issue Innovative Strategies for Sustainable Mitigation of Landslide Risk)
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Article
The Potential Use of Ground Conductivity Meters to Identify the Location of Seepages—Case Study of the Maniów Levee near Krakow, Poland
Geosciences 2020, 10(3), 97; https://doi.org/10.3390/geosciences10030097 - 03 Mar 2020
Viewed by 816
Abstract
This paper presents an assessment of the potential usefulness of the Ground Conductivity Meter (GCM) method to locate seepage pathways in the Maniow levee zone near Kraków, Poland. We have realized this aim through geological recognition of the study area, which requires the [...] Read more.
This paper presents an assessment of the potential usefulness of the Ground Conductivity Meter (GCM) method to locate seepage pathways in the Maniow levee zone near Kraków, Poland. We have realized this aim through geological recognition of the study area, which requires the implementation of GCM data inversion measured in the sounding version. The GCM measurements were performed along with the net of profiles using combined data from CMD Mini Explorer and CMD Explorer equipment. The methodology of the one-dimensional (1D) inversion of the GCM soundings located along profiles is presented in the article. The legitimacy of the inversion and the relationship of the results obtained in the form of conductivity sections along profiles with geology have been verified in detail. The inversion procedures were tested on the synthetic GCM soundings obtained from modeling processes, by using the electrical conductivity and thicknesses, known from the drilled formations and additionally based on DC-R sounding data. These soundings were performed at some selected reference points in the levee zone. We have used our software and IX1D Interpex software to calculate the forward modeling. Quantitative interpretation processed along the profiles has been proceeded by 1D inversion of GCM data at several referential points located close to boreholes and DC soundings. It was done to verify the correctness of the quantitative interpretation. The geoelectrical models, obtained in a section form, were correlated with the borehole lithology data, providing a reference geological structure in some places. As a result of the work mentioned above, the potential seepage zones were located on the conductivity sections. The thickness of the cohesive silty clay layer, lying near to the surface, in the seepage zones, was thin enough and less than a meter. When the water level in the Vistula river was high enough, water can flow in the noncohesive gravel layer occurring directly below the silty clays and lead to flooding on the landward side of the dams in the Maniow region. Full article
(This article belongs to the Section Geophysics)
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Comment
Comments on “On a Continuum Model for Avalanche Flow and Its Simplified Variants” by S. S. Grigorian and A. V. Ostroumov
Geosciences 2020, 10(3), 96; https://doi.org/10.3390/geosciences10030096 - 02 Mar 2020
Cited by 3 | Viewed by 882
Abstract
This note first summarizes the history of the manuscript “On a Continuum Model for Avalanche Flow and Its Simplified Variants” by Grigorian and Ostroumov—published in this Special Issue—since the early 1990s and explains the guiding principles in editing it for publication. The changes [...] Read more.
This note first summarizes the history of the manuscript “On a Continuum Model for Avalanche Flow and Its Simplified Variants” by Grigorian and Ostroumov—published in this Special Issue—since the early 1990s and explains the guiding principles in editing it for publication. The changes are then detailed and some explanatory notes given for the benefit of readers who are not familiar with the early Russian work on snow avalanche dynamics. Finally, the editor’s personal views as to why he still considers this paper of relevance for avalanche dynamics research today are presented in brief essays on key aspects of the paper, namely the role of simple and complex models in avalanche research and mitigation work, the status and possible applications of Grigorian’s stress-limited friction law, and non-monotonicity of the dynamics of the Grigorian–Ostroumov model in the friction coefficient. A comparison of the erosion model proposed by those authors with two other models suggests to enhance it with an additional equation for the balance of tangential momentum across the shock front. A preliminary analysis indicates that continuous scouring entrainment is possible only in a restricted parameter range and that there is a second erosion regime with delayed entrainment. Full article
(This article belongs to the Special Issue Snow Avalanche Dynamics)
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Article
Timing, Mechanics and Controls of the Evolution of the Southernmost Part of the Oman Mountains: The Salakh Arch
Geosciences 2020, 10(3), 95; https://doi.org/10.3390/geosciences10030095 - 01 Mar 2020
Cited by 1 | Viewed by 1097
Abstract
Regional surface and subsurface mapping of the front range of the Oman Mountains, Salakh Arch’s fold-and-thrust belt, is conducted to understand the timing and nature of its deformation and to analyze the main controls on its position, geometry and evolution. The results from [...] Read more.
Regional surface and subsurface mapping of the front range of the Oman Mountains, Salakh Arch’s fold-and-thrust belt, is conducted to understand the timing and nature of its deformation and to analyze the main controls on its position, geometry and evolution. The results from this study can be applied to other fold-and-thrust belts, as the area offers surface and subsurface datasets that allow good understanding of its evolution history. The deformation of the outcropping Middle Miocene to Pliocene deposits and the displacement of the Cenozoic seismic reflections imply that folding and thrusting was active during the Neogene and possibly ceased during the Early Quaternary. The palaeostress-tensor analyses from the kinematic fault data along with the fold-axes trends show that the regional transport direction was, overall, directed to the south. Lateral movements over oblique or lateral ramps, between the frontal ramps, have caused local deflections of the regional stress trajectories. The shortening values measured from restored seismic sections were utilized to restore the arch in map view. The restoration indicates that the arch initiated as a primary arc right from the start of deformation. As the shortening proceeded, clockwise and anticlockwise rotations occurred in some areas as a consequence of displacement gradients across adjacent areas along the arch. This rotation was most likely accommodated by angular shear strain, which results in arch-parallel extension or transtension. Various factors have controlled the position, geometry and segmentation of the fold segments in the Salakh Arch. The folds that developed in areas of thicker deformed sediments are wider and more uplifted and advanced to the foreland than the folds that develop in thin deformed sediments. Pre-existing faults were reactivated as lateral and frontal ramps during the arch’s evolution. They have contributed in the location and segmentation of the fold patches. On the other hand, the depth-to-detachment measurements and restoration results suggest that the folds detach along the Ediacaran-Early Cambrian Ara Salt. Overall, the deformation in the Salakh Arch could be described as an interaction between thin- and thick-skinned tectonics. Full article
(This article belongs to the Special Issue Tectonics of Oman—from the Precambrian to the Present)
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Article
Engineering Characterization of Subgrade Soils of Jimma Town, Ethiopia, for Roadway Design
Geosciences 2020, 10(3), 94; https://doi.org/10.3390/geosciences10030094 - 01 Mar 2020
Cited by 2 | Viewed by 1011
Abstract
Soils are naturally occurring materials that carry loads of civil engineering structures including roads and buildings. However, not all natural soils are suitable for such uses due to limited strength and instability under varying environmental conditions. A lack of adequate geotechnical investigations and [...] Read more.
Soils are naturally occurring materials that carry loads of civil engineering structures including roads and buildings. However, not all natural soils are suitable for such uses due to limited strength and instability under varying environmental conditions. A lack of adequate geotechnical investigations and soil characterization can result in the over-design of foundations, unexpected excavations to remove unsuitable soils, cost overruns, construction delays; and, contract disputes. In this research, an experimental plan was executed to determine the engineering properties of subgrade soil in Jimma Town in southwestern Ethiopia by using both disturbed and undisturbed soil samples. The plan included tests to determine the moisture content, specific gravity, grain-size analysis, Atterberg limits, compaction-density relationship, California Bearing Ratio (CBR), unconfined compression strength, and triaxial shear strength. X-ray diffraction (XRD) analysis was also conducted to determine the chemical composition of the soil. The soil characterization indicated that soft clay is the predominant subgrade soil type and that it has a very low load-bearing capacity, high plasticity, low strength and, high compressibility, which makes the soil unsuitable to serve as a highway subgrade without the help of soil improvement techniques. Full article
(This article belongs to the Section Geophysics)
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Article
Climate and the Development of Magma Chambers
Geosciences 2020, 10(3), 93; https://doi.org/10.3390/geosciences10030093 - 01 Mar 2020
Cited by 4 | Viewed by 1373
Abstract
Whether magma accumulating in the crust develops into a persistent, eruptible magma body or an incrementally emplaced pluton depends on the energy balance between heat delivered to the bottom in the form of magma and heat lost out the top. The rate of [...] Read more.
Whether magma accumulating in the crust develops into a persistent, eruptible magma body or an incrementally emplaced pluton depends on the energy balance between heat delivered to the bottom in the form of magma and heat lost out the top. The rate of heat loss to the surface depends critically on whether heat transfer is by conduction or convection. Convection is far more efficient at carrying heat than conduction, but requires both abundant water and sufficient permeability. Thus, all else being equal, both long-term aridity and self-sealing of fractures should promote development of persistent magma bodies and explosive silicic volcanism. This physical link between climate and magmatism may explain why many of the world’s great silicic ignimbrite provinces developed in arid environments, and why extension seems to suppress silicic caldera systems. Full article
(This article belongs to the Special Issue Exploring and Modeling the Magma-Hydrothermal Regime)
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Article
Morphometric Characteristics, Shapes and Provenance of Holocene Pebbles from the Sava River Gravels (Zagreb, Croatia)
Geosciences 2020, 10(3), 92; https://doi.org/10.3390/geosciences10030092 - 29 Feb 2020
Cited by 2 | Viewed by 1052
Abstract
Morphometric analysis of Holocene pebbles from Sava River gravel in NW Croatia revealed shape distributions as observed along a 30 km long watercourse. Limestones, dolomites, and sandstones were identified as the major (>4%) and effusive magmatics in this alluvial aquifer system in Zagreb, [...] Read more.
Morphometric analysis of Holocene pebbles from Sava River gravel in NW Croatia revealed shape distributions as observed along a 30 km long watercourse. Limestones, dolomites, and sandstones were identified as the major (>4%) and effusive magmatics in this alluvial aquifer system in Zagreb, with cherts and tuffs as minor pebble lithologies (up to 4%). Their distributions mainly indicate distant Alpine provenance for carbonate pebbles (limestone and dolomite) and local input for sandstones and minor lithotypes, laterally from the Samoborska Gora and Medvednica mountain. Carbonates are predominantly disc- and sphere-shaped, implying distant sources. Scattered distributions of pebble shapes (sphere, disc, blade, and rod) for sandstones and minor lithotypes possibly indicate multiple sources, some of them probably local. The tentatively interpreted “original sedimentary environments” for the main pebble lithotypes (calculated from their flatness ratios) possibly indicate that they are predominantly lake beach pebbles, followed by moraine and riverbed pebbles. However, these results should be strongly questioned. Full article
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Review
Rock Features and Alteration of Stone Materials Used for the Built Environment: A Review of Recent Publications on Ageing Tests
Geosciences 2020, 10(3), 91; https://doi.org/10.3390/geosciences10030091 - 28 Feb 2020
Cited by 5 | Viewed by 924
Abstract
This work presents a review of recent publications, with publication date between 2017 and 2019, with information on the relation between rock characteristics and the effects of diverse agents associated with alteration of stone materials in the built environment. It considers information obtained [...] Read more.
This work presents a review of recent publications, with publication date between 2017 and 2019, with information on the relation between rock characteristics and the effects of diverse agents associated with alteration of stone materials in the built environment. It considers information obtained from ageing tests performed under laboratory conditions and by exposure to outdoor agents. Several lithological groups were considered, with sedimentary carbonate rocks being the most frequently studied lithotypes and silicate metamorphic rocks being the group with scarcer information. In terms of ageing tests, salt weathering was the most frequent one while there was a noticeable lesser amount of information from tests with biological colonization. The collected data showed the influence of diverse features, from specific minerals to whole-rock properties and the presence of heterogeneities. These information are discussed in the context of formulating a general framework for stone decay. Full article
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Article
Seismic and Rainfall Induced Displacements of an Existing Landslide: Findings from the Continuous Monitoring
Geosciences 2020, 10(3), 90; https://doi.org/10.3390/geosciences10030090 - 27 Feb 2020
Cited by 1 | Viewed by 829
Abstract
“La Sorbella” is a deep-seated existing landslide in a Miocene clayey formation located in central Italy. Given the interaction with a national road, this landslide has been monitored for a long time with inclinometers and hydraulic piezometers. Recently, the monitoring system was implemented [...] Read more.
“La Sorbella” is a deep-seated existing landslide in a Miocene clayey formation located in central Italy. Given the interaction with a national road, this landslide has been monitored for a long time with inclinometers and hydraulic piezometers. Recently, the monitoring system was implemented by adding pressure transducers in the Casagrande cells and by equipping the old inclinometers with in-place probes, to allow a remote reading of the instruments and data recording. This system allowed to identify that the very small average rate of movement observed over one year (1.0–1.5 cm/year) is the sum of small single sliding processes, strictly linked to the sequence of rainfall events. Moreover, data recorded by in-place inclinometer probes detected the response of the landslide to the seismic sequence of 2016 occurring in central Italy. Such in situ measurements during earthquakes, indeed rarely available in the scientific literature, allowed an assessment of the critical acceleration of the sliding mass by means of a back-analysis. The possibility to distinguish the difference between seismic and rainfall induced displacements of the slope underlines the potential of continuous monitoring in the diagnosis of landslide mechanisms. Full article
(This article belongs to the Special Issue Innovative Strategies for Sustainable Mitigation of Landslide Risk)
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Article
Mapping Spatio-Temporal Soil Erosion Patterns in the Candelaro River Basin, Italy, Using the G2 Model with Sentinel2 Imagery
Geosciences 2020, 10(3), 89; https://doi.org/10.3390/geosciences10030089 - 27 Feb 2020
Cited by 8 | Viewed by 1169
Abstract
This study aims at mapping soil erosion caused by water in the Candelaro river basin, Apulia region, Italy, using the G2 erosion model. The G2 model can provide erosion maps and statistical figures at month-time intervals, by applying non data-demanding alternatives for the [...] Read more.
This study aims at mapping soil erosion caused by water in the Candelaro river basin, Apulia region, Italy, using the G2 erosion model. The G2 model can provide erosion maps and statistical figures at month-time intervals, by applying non data-demanding alternatives for the estimation of all the erosion factors. In the current research, G2 is taking a step further with the introduction of Sentinel2 satellite images for mapping vegetation retention factor on a fine scale; Sentinel2 is a ready-to-use, image product of high quality, freely available by the European Space Agency. Although only three recent cloud-free Sentinel2 images covering Candelaro were found in the archive, new solutions were elaborated to overcome time-gaps. The study in Candelaro resulted in a mean annual erosion rate of 0.87 t ha−1 y−1, while the autumn months were indicated to be the most erosive ones, with average erosion rates reaching a maximum of 0.12 t ha−1 in September. The mixed agricultural-natural patterns revealed to be the riskiest surfaces for most months of the year, while arable land was the most extensive erosive land cover category. The erosion maps will allow competent authorities to support relevant mitigation measures. Furthermore, the study in Candelaro can play the role of a pilot study for the whole Apulia region, where erosion studies are rather limited. Full article
(This article belongs to the Special Issue Soil Degradation: Salinization, Compaction, and Erosion)
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Article
Demise of the Planktic Foraminifer Genus Morozovella during the Early Eocene Climatic Optimum: New Records from ODP Site 1258 (Demerara Rise, Western Equatorial Atlantic) and Site 1263 (Walvis Ridge, South Atlantic)
Geosciences 2020, 10(3), 88; https://doi.org/10.3390/geosciences10030088 - 27 Feb 2020
Cited by 5 | Viewed by 982
Abstract
Here we present relative abundances of planktic foraminifera that span the Early Eocene Climatic Optimum (EECO) at Ocean Drilling Program (ODP) Site 1258 in the western equatorial Atlantic. The EECO (~53.3−49.1 Ma) represents peak Cenozoic warmth, probably related to high atmospheric CO2 [...] Read more.
Here we present relative abundances of planktic foraminifera that span the Early Eocene Climatic Optimum (EECO) at Ocean Drilling Program (ODP) Site 1258 in the western equatorial Atlantic. The EECO (~53.3−49.1 Ma) represents peak Cenozoic warmth, probably related to high atmospheric CO2, and when planktic foraminifera, a dominant component of marine sediment, exhibit a major biotic response. Consistent with previous work, the relative abundance of the genus Morozovella, which dominated early Paleogene tropical-subtropical assemblages, markedly and permanently declined from a mean percentage of ~32% to less than ~7% at the beginning of the EECO. The distinct decrease in Morozovella abundance occurred at Site 1258 within ~20 kyr before a negative excursion in δ13C records known as the J event and which defines the beginning of EECO. Moreover, all morozovellid species except M. aragonensis dropped in abundance permanently at Site 1258, and this is related to a reduction in test-size. Comparing our data with that from other locations, the remarkable switch in planktonic foraminifera assemblages appears to have begun first with unfavourable environmental conditions near the Equator and then extended to higher latitudes. Several potential stressors may explain observations, including some combination of algal photosymbiont inhibition (bleaching), a sustained increase in temperature, or an extended decrease in pH. Full article
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Article
Preliminary Evidence for the Role Played by South Westerly Wind Strength on the Marine Diatom Content of an Antarctic Peninsula Ice Core (1980–2010)
Geosciences 2020, 10(3), 87; https://doi.org/10.3390/geosciences10030087 - 26 Feb 2020
Cited by 1 | Viewed by 1150
Abstract
Winds in the Southern Ocean drive exchanges of heat and carbon dioxide between the ocean and atmosphere. Wind dynamics also explain the dominant patterns of both basal and surface melting of glaciers and ice shelves in the Amundsen and Bellingshausen Seas. Long records [...] Read more.
Winds in the Southern Ocean drive exchanges of heat and carbon dioxide between the ocean and atmosphere. Wind dynamics also explain the dominant patterns of both basal and surface melting of glaciers and ice shelves in the Amundsen and Bellingshausen Seas. Long records of past wind strength and atmospheric circulation are needed to assess the significance of these recent changes. Here we present evidence for a novel proxy of past south westerly wind (SWW) strength over the Amundsen and Bellingshausen Seas, based on diatoms preserved in an Antarctic Peninsula ice core. Ecological affinities of the identified diatom taxa indicate an almost exclusively marine assemblage, dominated by open ocean taxa from the Northern Antarctic Zone (NAZ). Back-trajectory analysis shows the routes of air masses reaching the ice core site and reveals that many trajectories involve contact with surface waters in the NAZ of the Amundsen and Bellingshausen Seas. Correlation analyses between ice core diatom abundance and various wind vectors yield positive and robust coefficients for the 1980–2010 period, with average annual SWW speeds exhibiting the strongest match. Collectively, the data presented here provide new evidence that diatoms preserved in an Antarctic Peninsula ice core offer genuine potential as a new proxy for SWW strength. Full article
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Article
n-Alkane Distribution—A Paleovegetation Change Indicator during the Period from Late Glacial to Late Holocene on Russian Plain (Bryansk Region)
Geosciences 2020, 10(3), 86; https://doi.org/10.3390/geosciences10030086 - 26 Feb 2020
Cited by 2 | Viewed by 782
Abstract
Loess-paleosol series are well preserved in the south part of the Russian Plain. However, these sequences have a low number of studies on their organic matter, such as researches of isotope composition, n-alkane and other biomarkers. Thus, the purpose of the study [...] Read more.
Loess-paleosol series are well preserved in the south part of the Russian Plain. However, these sequences have a low number of studies on their organic matter, such as researches of isotope composition, n-alkane and other biomarkers. Thus, the purpose of the study was to reconstruct vegetation conditions from the Late Glacial to Late Holocene. We used the leaf wax-derived n-alkanes to detect vegetation evolution of the Bryansk Region. The stable carbon isotope composition of organic matter and pedogenic carbonates was carried out for the same aim. Three paleosols (of Lasko, Bølling-Allerød warmings and Holocene second humus horizons) and modern soils of different relief positions were investigated. n-Alkane distribution, as well as isotope composition indicates changes from grassy to woody vegetation during this period. The use of biomarkers such as n-alkanes helps to more clearly interpret isotopic data. Full article
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