Geosciences

14 pages, 2605 KiB

Open AccessArticle

New System for Measuring Cosmogenic Ne in Terrestrial and Extra-Terrestrial Rocks

by Domokos Györe, Luigia Di Nicola, David Currie and Finlay M. Stuart

Geosciences 2021, 11(8), 353; https://doi.org/10.3390/geosciences11080353 - 23 Aug 2021

Cited by 4 | Viewed by 3202

Cosmogenic Ne isotopes are used for constraining the timing and rate of cosmological and Earth surface processes. We combined an automated gas extraction (laser) and purification system with a Thermo Fisher ARGUS VI mass spectrometer for high through-put, high precision Ne isotope analysis. [...] Read more.

Cosmogenic Ne isotopes are used for constraining the timing and rate of cosmological and Earth surface processes. We combined an automated gas extraction (laser) and purification system with a Thermo Fisher ARGUS VI mass spectrometer for high through-put, high precision Ne isotope analysis. For extra-terrestrial material with high cosmogenic Ne concentrations, we used multi-collection on Faraday detectors. Multiple measurements (n = 26) of 1.67 × 10⁻⁸ cm³ air-derived ²⁰Ne yielded an uncertainty of 0.32%, and ²¹Ne/²⁰Ne = 0.17% and ²²Ne/²⁰Ne = 0.09%. We reproduced the isotope composition of cosmogenic Ne in the Bruderheim chondrite and Imilac pallasite in a sub-ten mg sample. For lower Ne amounts that are typical of terrestrial samples, an electron multiplier detector was used in peak jumping mode. Repeated analysis of 3.2 × 10⁻¹¹ cm³ STP ²⁰Ne from air reproduced ²¹Ne/²⁰Ne and ²²Ne/²⁰Ne with 1.1% and 0.58%, respectively, and ²⁰Ne intensity with 1.7% (n = 103) over a 4-month period. Multiple (n = 8) analysis of cosmogenic Ne in CREU-1 quartz yielded 3.25 ± 0.24 × 10⁸ atoms/g (2 s), which overlaps with the global mean value. The repeatability is comparable to the best data reported in the international experiments performed so far on samples that are 2–5× smaller. The ability to make precise Ne isotope determinations in terrestrial and extra-terrestrial samples that are significantly smaller than previously analysed suggests that the new system holds great promise for studies with limited material. Full article

(This article belongs to the Special Issue Cutting Edge Earth Sciences: Three Decades of Cosmogenic Nuclides)

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29 pages, 13439 KiB

Open AccessArticle

Geochemical Study on the Annual Variation of Oxygen Isotope and Chemical Composition of Groundwater in the Sho River Alluvium Fan, Toyama, Japan, as an Investigation of Selected Qualitative Aspects of Efficient Utilization of Groundwater Heat

by Kaname Iwatake and Akira Ueda

Geosciences 2021, 11(8), 352; https://doi.org/10.3390/geosciences11080352 - 23 Aug 2021

Cited by 1 | Viewed by 2538

Abstract

Seasonal variations of water temperature, electric conductivity, and oxygen isotope and chemical composition of shallow groundwaters and river waters were determined in the Sho River alluvial fan, western Toyama Prefecture, Japan, to examine groundwater heat utilization for indoor climate control. Samples were collected [...] Read more.

Seasonal variations of water temperature, electric conductivity, and oxygen isotope and chemical composition of shallow groundwaters and river waters were determined in the Sho River alluvial fan, western Toyama Prefecture, Japan, to examine groundwater heat utilization for indoor climate control. Samples were collected at 31 sites every 2 months for 1 year and at 11 representative sites monthly. In addition, the results of monthly precipitation amount and oxygen isotope composition of precipitation collected within the region during the same period were also taken into account. The sources of the shallow groundwaters are a mixture of river water and precipitation. The contribution of precipitation to groundwater is generally small along the Sho River but reaches as much as 80% along the Oyabe River and in the south and west of the alluvial fan. Though the origin of the groundwater differs regionally, water temperature is fixed at around 15 °C throughout the year in the northern part of the alluvial fan, and open-type ground source heat pump systems can be used for cooling and heating there, if adequate quantitative aquifer properties (exploitable groundwater amounts) are present. Full article

(This article belongs to the Special Issue Geochemical Characterization of Geothermal Systems: Multidisciplinary Approaches to Define Source Processes, Evolution and Environmental Issues)

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14 pages, 4745 KiB

Open AccessArticle

Observed Auroral Ovals Secular Variation Inferred from Auroral Boundary Data

by Bruno Zossi, Hagay Amit, Mariano Fagre and Ana G. Elias

Geosciences 2021, 11(8), 351; https://doi.org/10.3390/geosciences11080351 - 23 Aug 2021

Cited by 2 | Viewed by 2696

Abstract

We analyze the auroral boundary corrected geomagnetic latitude provided by the Auroral Boundary Index (ABI) database to estimate long-term changes of core origin in the area enclosed by this boundary during 1983–2016. We design a four-step filtering process to minimize the solar contribution [...] Read more.

We analyze the auroral boundary corrected geomagnetic latitude provided by the Auroral Boundary Index (ABI) database to estimate long-term changes of core origin in the area enclosed by this boundary during 1983–2016. We design a four-step filtering process to minimize the solar contribution to the auroral boundary temporal variation for the northern and southern hemispheres. This process includes filtering geomagnetic and solar activity effects, removal of high-frequency signal, and additional removal of a ~20–30-year dominant solar periodicity. Comparison of our results with the secular change of auroral plus polar cap areas obtained using a simple model of the magnetosphere and a geomagnetic core field model reveals a decent agreement, with area increase/decrease in the southern/northern hemisphere respectively for both observations and model. This encouraging agreement provides observational evidence for the surprising recent decrease of the auroral zone area. Full article

(This article belongs to the Special Issue Extreme Geomagnetic Events)

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22 pages, 6984 KiB

Open AccessArticle

Long-Term Changes, Inter-Annual, and Monthly Variability of Sea Level at the Coasts of the Spanish Mediterranean and the Gulf of Cádiz

by Manuel Vargas-Yáñez, Elena Tel, Francina Moya, Enrique Ballesteros and Mari Carmen García-Martínez

Geosciences 2021, 11(8), 350; https://doi.org/10.3390/geosciences11080350 - 20 Aug 2021

Cited by 3 | Viewed by 2098

Abstract

One of the effects of climate change is the rise of sea level, which poses an important threat to coastal areas. Therefore, the protection and management of coastal ecosystems as well as human infrastructures and constructions require an accurate knowledge of those changes [...] Read more.

One of the effects of climate change is the rise of sea level, which poses an important threat to coastal areas. Therefore, the protection and management of coastal ecosystems as well as human infrastructures and constructions require an accurate knowledge of those changes occurring at a local scale. In this study, long time series of sea level from tide gauges distributed along the southern (Atlantic) and eastern (Mediterranean) Spanish coasts were analyzed. Linear trends were calculated for two periods, from early 1940s to 2018 and from 1990 to 2018. Values for the former period ranged between 0.68 and 1.22 mm/year. These trends experienced a significant increase for the second period, when they ranged between 1.5 and 4.6 mm/year. Previous research analyzed the effect of atmospheric forcing in the Mediterranean Sea by means of 2D numerical models, and the steric contribution was directly evaluated by the integration of density along the water column. In this study, the effect of atmospheric forcing and the thermosteric and halosteric contributions on coastal sea level were empirically determined by means of statistical linear models that established which factors affected sea level at each location and what the numerical response of the observed sea level was to the contributing factors. Atmospheric pressure and the west–east component of the wind hada significant contribution to the sea level variability at most of the tide gauges. The thermosteric and halosteric components of sea level also contributed to the sea level variability at all the tide gauges, with the only exception of Alicante. Atmospheric forcing and the steric components of sea level experienced long-term trends. The combination of such trends, with the response of sea level to these factors, allowed us to estimate their contribution to the observed sea level trends. The part of these trends not explained by the atmospheric variables and the steric contributions was attributed to mass addition. Trends associated with mass addition ranged between 0.6 and 1.2 mm/year for the period 1948–2018 and between 1.0 and 4.5 mm/year for the period 1990–2018. Full article

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20 pages, 5664 KiB

Open AccessArticle

Analysis of Enhanced Geothermal System Development Scenarios for District Heating and Cooling of the Göttingen University Campus

by Dmitry Romanov and Bernd Leiss

Geosciences 2021, 11(8), 349; https://doi.org/10.3390/geosciences11080349 - 19 Aug 2021

Cited by 10 | Viewed by 3726

Abstract

The huge energy potential of Enhanced Geothermal Systems (EGS) makes them perspective sources of non-intermittent renewable energy for the future. This paper focuses on potential scenarios of EGS development in a locally and in regard to geothermal exploration, poorly known geological setting—the Variscan [...] Read more.

The huge energy potential of Enhanced Geothermal Systems (EGS) makes them perspective sources of non-intermittent renewable energy for the future. This paper focuses on potential scenarios of EGS development in a locally and in regard to geothermal exploration, poorly known geological setting—the Variscan fold-and-thrust belt —for district heating and cooling of the Göttingen University campus. On average, the considered single EGS doublet might cover about 20% of the heat demand and 6% of the cooling demand of the campus. The levelized cost of heat (LCOH), net present value (NPV) and CO₂ abatement cost were evaluated with the help of a spreadsheet-based model. As a result, the majority of scenarios of the reference case are currently not profitable. Based on the analysis, EGS heat output should be at least 11 MW_th (with the brine flow rate being 40 l/s and wellhead temperature being 140 °C) for a potentially profitable project. These parameters can be a target for subsurface investigation, reservoir modeling and hydraulic stimulation at a later stage. However, sensitivity analysis presented some conditions that yield better results. Among the most influential parameters on the outcome are subsidies for research wells, proximity to the campus, temperature drawdown and drilling costs. If realized, the EGS project in Göttingen might save up to 18,100 t CO₂ (34%) annually. Full article

(This article belongs to the Special Issue Enhanced Geothermal Systems and other Deep Geothermal Applications throughout Europe: The MEET Project)

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20 pages, 2669 KiB

Open AccessArticle

Calculation of Potential Evapotranspiration and Calibration of the Hargreaves Equation Using Geostatistical Methods over the Last 10 Years in Central Italy

by Matteo Gentilucci, Margherita Bufalini, Marco Materazzi, Maurizio Barbieri, Domenico Aringoli, Piero Farabollini and Gilberto Pambianchi

Geosciences 2021, 11(8), 348; https://doi.org/10.3390/geosciences11080348 - 19 Aug 2021

Cited by 24 | Viewed by 4643

Abstract

Potential evapotranspiration (ET0) is an indicator of great interest for water budget analysis and the agricultural sector. Therefore, the purpose of this study was to make the calculation reliable even if only the temperature data were present. In this research, the ET0 was [...] Read more.

Potential evapotranspiration (ET0) is an indicator of great interest for water budget analysis and the agricultural sector. Therefore, the purpose of this study was to make the calculation reliable even if only the temperature data were present. In this research, the ET0 was initially calculated for a limited number of weather stations (12) using the Penman–Monteith method. In some cases, the simplified Penman–Monteith formula was adopted, while in others, as in the case of mountain weather stations, the complete formula was employed to consider the differences in vegetation, deduced from satellite surveys. Subsequently, the ET0 was calculated with the Hargreaves–Samani (HS) formula, calibrating the Hargreaves coefficient, through the spatialization of ET0, by the geostatistical method. The results showed a high reliability of the HS method in comparison with simplified PM (PM) method, and complete Penman–Monteith (cPM) method, with a minimum calibration of the empirical Hargreaves coefficient. In particular, a very good correlation between the results obtained in the mountain environment with the uncalibrated HS method and the cPM method was also observed in this area, while PM showed discordant and much higher results than ET0 compared with the other methods. It follows that this procedure allowed a more accurate estimate of potential evapotranspiration with a view to territory management, both in terms of water resources and the irrigation needs of the vegetation. Full article

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21 pages, 4588 KiB

Open AccessArticle

Speleothem Records of the Hydroclimate Variability throughout the Last Glacial Cycle from Manita peć Cave (Velebit Mountain, Croatia)

by Maša Surić, Petra Bajo, Robert Lončarić, Nina Lončar, Russell N. Drysdale, John C. Hellstrom and Quan Hua

Geosciences 2021, 11(8), 347; https://doi.org/10.3390/geosciences11080347 - 19 Aug 2021

Cited by 6 | Viewed by 3607

Abstract

We present stable carbon (δ¹³C) and oxygen (δ¹⁸O) isotope records from two partially coeval speleothems from Manita peć Cave, Croatia. The cave is located close to the Adriatic coast (3.7 km) at an elevation of 570 m a.s.l. The [...] Read more.

We present stable carbon (δ¹³C) and oxygen (δ¹⁸O) isotope records from two partially coeval speleothems from Manita peć Cave, Croatia. The cave is located close to the Adriatic coast (3.7 km) at an elevation of 570 m a.s.l. The site experienced competing Mediterranean and continental climate influences throughout the last glacial cycle and was situated close to the ice limit during the glacial phases. U-Th dating constrains the growth history from Marine Isotope Stage (MIS) 5 to MIS 3 and the transition from MIS 2 to MIS 1. ¹⁴C dating was used to estimate the age of the youngest part of one stalagmite found to be rich in detrital thorium and thus undatable by U-Th. On a millennial scale, δ¹⁸O variations partly mimic the Dansgaard–Oeschger interstadials recorded in Greenland ice cores (Greenland Interstadials, GI) from GI 22 to GI 13. We interpret our δ¹⁸O record as a proxy for variations in precipitation amount and/or moisture sources, and the δ¹³C record is interpreted as a proxy for changes in soil bioproductivity. The latter indicates a generally reduced vegetation cover towards MIS 3–MIS 4, with shifts of ~8‰ and approaching values close to those of the host rock. However, even during the coldest phases, when a periglacial setting and enhanced aridity sustained long-residence-time groundwater, carbonic-acid dissolution remains the driving force of the karstification processes. Speleothem morphology follows changes in environmental conditions and complements regional results of submerged speleothems findings. Specifically, narrow sections of light porous spelaean calcite precipitated during the glacial/stadial sea-level lowstands, while the warmer and wetter conditions were marked with compact calcite and hiatuses in submerged speleothems due to sea-level highstands. Presumably, the transformation of this littoral site to a continental one with somewhat higher amounts of orographic precipitation was a site-specific effect that masked regional environmental changes. Full article

(This article belongs to the Special Issue Changing Quaternary Environment in the Mediterranean)

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33 pages, 5311 KiB

Open AccessArticle

Advanced Determination of Heat Flow Density on an Example of a West Russian Oil Field

by Yury Popov, Mikhail Spasennykh, Anuar Shakirov, Evgeny Chekhonin, Raisa Romushkevich, Egor Savelev, Anastasia Gabova, Dzhulia Zagranovskaya, Rim Valiullin, Rashid Yuarullin, Inessa Golovanova and Raushaniya Sal’manova

Geosciences 2021, 11(8), 346; https://doi.org/10.3390/geosciences11080346 - 18 Aug 2021

Cited by 4 | Viewed by 2855

Abstract

Reliable geothermal data are required for basin and petroleum system modeling. The essential shortcomings of the methods and results of previous geothermal investigations lead to a necessity to reappraise the data on the thermal properties and heat flow. A new, advanced experimental basis [...] Read more.

Reliable geothermal data are required for basin and petroleum system modeling. The essential shortcomings of the methods and results of previous geothermal investigations lead to a necessity to reappraise the data on the thermal properties and heat flow. A new, advanced experimental basis was used to provide reliable data on vertical variations in the thermal properties of formation and heat flow for the area surrounding a prospecting borehole drilled through an unconventional hydrocarbon reservoir of the Domanik Formation in the Orenburg region (Russia). Temperature logging was conducted 12.5 months after well drilling. The thermal properties of the rocks were measured with continuous thermal core profiling on all 1699 recovered core samples. Within non-cored intervals, the thermal conductivity of the rocks was determined from well-logging data. The influence of core aging, multiscale heterogeneity and anisotropy, in situ pressure and temperature on the thermal properties of rock was accounted for. The terrestrial heat flow was determined to be 72.6 ± 2.2 mW·m⁻²—~114% larger than the published average data for the studied area. The experiment presents the first experience of supporting basin modeling in unconventional plays with advanced experimental geothermal investigations. Full article

(This article belongs to the Special Issue Petrophysics and Geochemistry of Unconventional Reservoirs)

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16 pages, 2882 KiB

Open AccessArticle

Geomorphological and Statistical Assessment of Tilt-Block Tectonics in the Garhwal Synform: Implications for the Active Tectonics, Garhwal Lesser Himalaya, India

by Ashish Rawat, Sayandeep Banerjee and Yaspal Sundriyal

Geosciences 2021, 11(8), 345; https://doi.org/10.3390/geosciences11080345 - 18 Aug 2021

Cited by 4 | Viewed by 3218

Abstract

Active tectonics is manifested in geomorphological features such as drainage basins and drainage patterns. Geomorphic parameters asymmetry factor (AF) and transverse topography symmetry factor (T) is calculated for 94 third order basins of the Garhwal synform to decipher the tilt-block tectonics based on [...] Read more.

Active tectonics is manifested in geomorphological features such as drainage basins and drainage patterns. Geomorphic parameters asymmetry factor (AF) and transverse topography symmetry factor (T) is calculated for 94 third order basins of the Garhwal synform to decipher the tilt-block tectonics based on remote sensing and geographical information system (GIS) techniques. The quantitative analysis of the AF suggests that all the 94 basins are asymmetric and gentle to steeply tilted, indicating active tectonics and early and late stage of development, respectively. The mean vector magnitude (θ_v) of T suggests the migration of the basin stream towards the south in most basins (60%), suggesting a unidirectional tilting of the tectonic block. The χ² test for statistical significance indicates that the θ_v is significant for southern and northern limb basins. The χ² test affirms that the third order basin position on either side of the main channel of the river basin influences the tilt direction. The regional tectonics suggests migration of the Lansdowne klippe towards the south, as the majority of third order basins show southward tilt. The study provides a quick appraisal of tilting in the tectonic blocks of active margins, such as in the Himalayas. Full article

(This article belongs to the Special Issue Morphogenic Faulting: Current Practices and Future Challenges)

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13 pages, 1879 KiB

Open AccessReview

The Neglected Involvement of Organic Matter in Forming Large and Rich Hydrothermal Orogenic Gold Deposits

by Damien Gaboury

Geosciences 2021, 11(8), 344; https://doi.org/10.3390/geosciences11080344 - 17 Aug 2021

Cited by 9 | Viewed by 3677

Abstract

Orogenic gold deposits have provided most of gold to humanity. These deposits were formed by fluids carrying dissolved gold at temperatures of 200–500 °C and at crustal depths of 4–12 km. The model involves gold mobilization as HS⁻ complexes in aqueous solution [...] Read more.

Orogenic gold deposits have provided most of gold to humanity. These deposits were formed by fluids carrying dissolved gold at temperatures of 200–500 °C and at crustal depths of 4–12 km. The model involves gold mobilization as HS⁻ complexes in aqueous solution buffered by CO₂, with gold precipitation following changes in pH, redox activity (fO₂), or H₂S activity. In this contribution, the involvement of carbonaceous organic matter is addressed by considering the formation of large and/or rich orogenic gold deposits in three stages: the source of gold, its solubilization, and its precipitation. First, gold accumulates in nodular pyrite within carbonaceous-rich sedimentary rocks formed by bacterial reduction of sulfates in seawater in black shales. Second, gold can be transported as hydrocarbon-metal complexes and colloidal gold nanoparticles for which the hydrocarbons can be generated from the thermal maturation of gold-bearing black shales or from abiotic origin. The capacity of hydrocarbons for solubilizing gold is greater than those of aqueous fluids. Third, gold can be precipitated efficiently with graphite derived from fluids containing hydrocarbons or by reducing organic-rich rocks. Black shales are thus a key component in the formation of large and rich orogenic gold deposits from the standpoints of source, transport, and precipitation. Unusual CO₂-rich, H₂O-poor fluids are documented for some of the largest and richest orogenic gold deposits, regardless of their age. These fluids are interpreted to result from chemical reactions involving hydrocarbon degradation, hence supporting the fundamental role of organic matter in forming exceptional orogenic gold deposits. Full article

(This article belongs to the Section Geochemistry)

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25 pages, 4669 KiB

Open AccessArticle

Nonlinear Dynamic Analysis of a Masonry Arch Bridge Accounting for Damage Evolution

by Daniela Addessi, Cristina Gatta, Mariacarla Nocera and Domenico Liberatore

Geosciences 2021, 11(8), 343; https://doi.org/10.3390/geosciences11080343 - 16 Aug 2021

Cited by 15 | Viewed by 2731

Abstract

This study investigates the nonlinear dynamic response of the masonry bridge ‘Ponte delle Torri’ in Spoleto, aiming at assessing the seismic performance of the structure and evaluating the occurring damaging mechanisms. A 3D Finite Element (FE) macromechanical procedure implemented in the FE program [...] Read more.

This study investigates the nonlinear dynamic response of the masonry bridge ‘Ponte delle Torri’ in Spoleto, aiming at assessing the seismic performance of the structure and evaluating the occurring damaging mechanisms. A 3D Finite Element (FE) macromechanical procedure implemented in the FE program FEAP is adopted to model the bridge. To reproduce the typical nonlinear microcracking process evolving in masonry material when subjected to external loads, an isotropic damage model is used. This is based on a scalar damage variable introduced in the stress-strain constitutive law and equally degrading all the components of the elastic constitutive operator. A nonlocal integral definition of the damage associated variable, that is the equivalent strain measure governing its evolution, is adopted to overcome the mesh dependency problems of the FE solution typically occurring in the presence of strain softening behavior. Based on the results of a recent study by some of the authors, a single equivalent pier is analyzed, whose geometry and boundary conditions are selected so that its response can provide useful information on the out-of-plane dynamic behavior of the overall bridge. To perform the seismic assessment, a set of recorded accelerograms is properly selected to simulate the seismic history of the Spoleto site. The nonlinear dynamic response of the structure is evaluated and monitored in terms of top displacement time history, evolution of the global damage index, and distribution of the damage variable. First, a set of analyses is performed by imposing the selected ground motions one by one on the initial undamaged configuration for the structure with the aim of emphasizing the damaging effects on its dynamic response. Then, the accelerograms are arranged in sequence to reproduce the seismic history of the site and analyze the influence of accumulated damage on the dynamic amplification of the response. A critical comparison of the bridge response to the sequence of accelerograms and the single records is made, and the interaction between the damaged structure dynamic response and the signal characteristic is highlighted, as well. Full article

(This article belongs to the Special Issue Seismic Vulnerability and Strengthening of Unreinforced Masonry Buildings)

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22 pages, 7098 KiB

Open AccessArticle

Application of Rock Weathering and Colonization by Biota for the Relative Dating of Moraines from the Arid Part of the Russian Altai Mountains

by Dmitrii A. Ganyushkin, Sofia N. Lessovaia, Dmitrii Y. Vlasov, Gennady P. Kopitsa, László Almásy, Kirill V. Chistyakov, Elena G. Panova, Ekaterina Derkach and Anastasiya Alekseeva

Geosciences 2021, 11(8), 342; https://doi.org/10.3390/geosciences11080342 - 14 Aug 2021

Cited by 2 | Viewed by 2552

Abstract

For the Altai Mountains’ region, especially the arid southeastern part of the Russian Altai, the data on glacier fluctuations in the Pleistocene and Holocene are still inconsistent. The study area was the Kargy River’s valley (2288–2387 m a.s.l.), a location that is not [...] Read more.

For the Altai Mountains’ region, especially the arid southeastern part of the Russian Altai, the data on glacier fluctuations in the Pleistocene and Holocene are still inconsistent. The study area was the Kargy River’s valley (2288–2387 m a.s.l.), a location that is not currently affected by glaciation and the glacial history of which is poorly studied. Field observations and geomorphological mapping were used to reveal the configuration of Pleistocene moraines. The relative dating method was applied to define the degree of weathering as an indicator of age. Three moraine groups of different ages (presumably MIS 6, MIS 4, and MIS 2) were identified based on a detailed investigation of their morphological features and the use of relative dating approaches. The latter were primarily based on weathering patterns. Data on the rock mineralogy, porosity, and specificity of biological colonization as an agent of weathering were obtained for the moraine debris. The studied moraines were composed of fine-grained schist, in which the specific surface area and fractality (self-similarity) were more developed in the older moraine. The growth of biota (crustose lichen and micromycetes) colonizing the rock surface led to rock disintegration and the accumulation of autochthonous fragments on the rock surface. Despite the fact that the initial stage(s) of moraine weathering affected by biota was fixed, the correlation trends of biota activity and moraine ages were not determined. Full article

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16 pages, 123105 KiB

Open AccessArticle

Tectonic Influence on Speleogenesis of Sea Caves on Biševo Island (UNESCO Global Geopark Vis Archipelago, Adriatic Sea, Croatia)

by Ivan Mišur, Marko Budić, Tomislav Kurečić and Tvrtko Korbar

Geosciences 2021, 11(8), 341; https://doi.org/10.3390/geosciences11080341 - 13 Aug 2021

Viewed by 3222

Abstract

A geological and speleological investigation was conducted in the famous Blue Cave (Modra špilja) and the Monk Seal Cave (Medvidina špilja) on Biševo Island (Croatia) to promote the island’s geoheritage through the new Visitor Centre. The island is mainly composed of Cretaceous to [...] Read more.

A geological and speleological investigation was conducted in the famous Blue Cave (Modra špilja) and the Monk Seal Cave (Medvidina špilja) on Biševo Island (Croatia) to promote the island’s geoheritage through the new Visitor Centre. The island is mainly composed of Cretaceous to Paleogene neritic carbonates, which form the bedrock, whereas parts of the island are covered with thin Quaternary sediments. The caves are of small dimensions and a simple layout, composed of the main channel and few shorter side channels, all positioned in the tidal zone. Thus, the caves are semi-submerged sea caves located along the coastline. The Blue Cave and the Monk Seal Cave developed within the bedrock limestones and dolostones, respectively, within a zone of left-lateral NNE–SSW striking strike-slip faults that belong to the Biševo fault system. Conjugated discontinuities within the carbonate bedrock indicate a specific strike-slip tectonic regime. Additionally, the host rocks were probably also deformed and fractured during the rise of salt diapirs that characterise this part of the Adriatic foreland. Tectonic and bedding discontinuities form the fragments of the host rock, that combined with the impacts of the strong southern waves, significantly influenced the genesis of the caves. Full article

(This article belongs to the Special Issue From Geoheritage to Geotourism—New Advances and Emerging Challenges)

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14 pages, 4076 KiB

Open AccessConcept Paper

The Morphology of Prometheus, Literary Geography and the Geoethical Project

by Charles Travis

Geosciences 2021, 11(8), 340; https://doi.org/10.3390/geosciences11080340 - 13 Aug 2021

Viewed by 3791

Abstract

This paper explores mappings, musings and ‘thought experiments’ in literary geography to consider how they may contribute to geoethical pedagogy and research. Representations of Prometheus from the fourteenth century onwards have traveled along three broad symbological roads: first, as the creator, and bringer [...] Read more.

This paper explores mappings, musings and ‘thought experiments’ in literary geography to consider how they may contribute to geoethical pedagogy and research. Representations of Prometheus from the fourteenth century onwards have traveled along three broad symbological roads: first, as the creator, and bringer of fire; second as a bound figure in chains, and thirdly, unbound. However, it was the harnessing of fire by our species a millennium prior that gave rise to the myth of Prometheus and set into motion the geophysical process of combustion which “facilitated the transformation of much of the terrestrial surface […] and in the process pushed the parameters of the earth system into a new geological epoch.” As the geophysicist Professor Michael Mann observes, global warming and loss of biodiversity constitutes an ethical problem. The remediation of the Prometheus myth in Mary Shelley’s Frankenstein; or the modern Prometheus (1818), Jonathan Fetter-Vorm’s Trinity: A Graphic History of the First Atomic Bomb (2012) and William Golding’s novel Lord of the Flies (1954) provides the means to explore the geographical, historical and cultural contingencies of geoethical dilemmas contributing to the framing of the Anthropocene and Gaia heuristics. This paper argues for the necessity of scholars in the arts, humanities and geosciences to share and exchange idiographic and nomothetic perspectives in order to forge a geoethical dialectic that fuses poetic and positivistic methods into transcendent ontologies and epistemologies to address the existential questions of global warming and loss of biodiversity as we enter the age of the Anthropocene. Full article

(This article belongs to the Collection Ethics in Geosciences)

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28 pages, 9151 KiB

Open AccessArticle

Cosmogenic and Geological Evidence for the Occurrence of a Ma-Long Feedback between Uplift and Denudation, Chur Region, Swiss Alps

by Ewerton da Silva Guimarães, Romain Delunel, Fritz Schlunegger, Naki Akçar, Laura Stutenbecker and Marcus Christl

Geosciences 2021, 11(8), 339; https://doi.org/10.3390/geosciences11080339 - 12 Aug 2021

Cited by 2 | Viewed by 2852

Abstract

We used concentrations of in situ cosmogenic ¹⁰Be from riverine sediment to quantify the basin-averaged denudation rates and sediment fluxes in the Plessur Basin, Eastern Swiss Alps, which is a tributary stream to the Alpine Rhine, one of the largest streams in [...] Read more.

We used concentrations of in situ cosmogenic ¹⁰Be from riverine sediment to quantify the basin-averaged denudation rates and sediment fluxes in the Plessur Basin, Eastern Swiss Alps, which is a tributary stream to the Alpine Rhine, one of the largest streams in Europe. We complement the cosmogenic dataset with the results of morphometric analyses, geomorphic mapping, and sediment fingerprinting techniques. The results reveal that the Plessur Basin is still adjusting to the landscape perturbation caused by the glacial carving during the Last Glacial Maximum c. 20,000 years ago. This adjustment has been most efficient in the downstream part where the bedrock comprises high erodibility North Penninic flysch and Bündnerschist, whereas glacial landforms are still prominently preserved in the upstream region, comprising low erodibility South Penninic and Austroalpine bedrock. This geomorphic observation is supported by the ¹⁰Be based denudation rate and sediment provenance analysis, which indicate a much faster sediment production in the flysch and schist lithologies. Interestingly, the reach of fast denudation has experienced the highest exhumation and rock uplift rates. This suggests that lithologic and glacial conditioning have substantially contributed to the local uplift and denudation as some of the driving forces of a positive feedback system. Full article

(This article belongs to the Special Issue Cutting Edge Earth Sciences: Three Decades of Cosmogenic Nuclides)

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26 pages, 13283 KiB

Open AccessArticle

Tectonic and Stratigraphic Evolution Based on Seismic Sequence Stratigraphy: Central Rift Section of the Campos Basin, Offshore Brazil

by Renata dos Santos Alvarenga, Juliano Kuchle, David Iacopini, Karin Goldberg, Claiton Marlon dos Santos Scherer, George Pantopoulos and Patrycia Leipnitz Ene

Geosciences 2021, 11(8), 338; https://doi.org/10.3390/geosciences11080338 - 12 Aug 2021

Cited by 6 | Viewed by 4787

Abstract

The rift section of the Brazilian basins represent the sedimentary record associated with the first stages of Gondwana break-up in the Early Cretaceous phase (Berriasian to Aptian). The rift succession of the Campos Basin constitutes one of the main petroleum systems of Brazil’s [...] Read more.

The rift section of the Brazilian basins represent the sedimentary record associated with the first stages of Gondwana break-up in the Early Cretaceous phase (Berriasian to Aptian). The rift succession of the Campos Basin constitutes one of the main petroleum systems of Brazil’s marginal basins. This interval contains the main source rock and important reservoirs in the Lagoa Feia Group deposits. The Lagoa Feia Group is characterized by siliciclastic, carbonate and evaporite sediments deposited during the rift and post-rift phases. Despite the economic relevance, little is known in stratigraphic terms regarding this rift interval. To date, most studies of the Lagoa Feia Group have adopted a lithostratigraphic approach, while this study proposes a tectonostratigraphic framework for the deep-rift succession of the Campos Basin (Lagoa Feia Group), using the fundamentals of seismic sequence stratigraphy. This work also aims to establish a methodological and practical procedure for the stratigraphic analysis of rift basins, using seismic data and seismofacies, and focusing on tectonicstratigraphic analysis. The dataset comprised 2D seismic lines, core and lithological logs from exploration wells. Three seismic facies were identified based on reflector patterns and lithologic data from well cores, providing an improved subdivision of the pre-, syn- and post-rift stages. The syn-rift stage was further subdivided based on the geometric patterns of the reflectors. Tectonics was the main controlling factor in the sedimentary succession, and the pattern and geometry of the seismic reflectors of the syn-rift interval in the Campos Basin allowed the identification of three tectonic systems tracts: (i) a Rift Initiation Systems Tract; (ii) a High Tectonic Activity Systems Tract and (iii) a Low Tectonic Activity Systems Tract. Full article

(This article belongs to the Special Issue Linking Tectonic Setting to Sedimentological and Stratigraphic Variability)

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17 pages, 4730 KiB

Open AccessCase Report

A Geotechnical Investigation of 2017 Chattogram Landslides

by Md. Azijul Islam, Mohammad Shariful Islam and Abhijeet Acharjee Jeet

Geosciences 2021, 11(8), 337; https://doi.org/10.3390/geosciences11080337 - 11 Aug 2021

Cited by 4 | Viewed by 5879

Abstract

In this study, an attempt is made to uncover and discuss the geo-environmental characteristics, triggers, and consequences of a landslide disaster in the Chattogram Hill Tracts (CHT) region of Bangladesh. The hilly areas are composed of Tertiary and Quaternary sediments which have been [...] Read more.

In this study, an attempt is made to uncover and discuss the geo-environmental characteristics, triggers, and consequences of a landslide disaster in the Chattogram Hill Tracts (CHT) region of Bangladesh. The hilly areas are composed of Tertiary and Quaternary sediments which have been folded, faulted, uplifted and, then deeply dissected by rivers and other water bodies. This paper presents a case study on the geotechnical investigation and numerical modeling of the landslides of 13 June 2017. A field visit and soil sample collection, followed by laboratory testing were conducted at the landslide-afflicted areas. The study revealed that the soil type was an important factor behind landslides, while high precipitation, hill cutting, deforestation, and unplanned human settlements act as contributing factors behind the landslide disaster. Extensive analysis of the geotechnical facts has been carried out, and an attempt is made to pinpoint the cause. A finite element modeling was conducted using PLAXIS 2D to investigate the failure mechanism. The numerical modeling results have suggested that most of the hill slopes were susceptible to failure after heavy rainfall. A conclusion is drawn that the landslides were triggered by incessant rainfall infiltrating into the subsoil, which led to a notable increase in its degree of saturation and a simultaneous reduction in suction and shear strength of the soil. Full article

(This article belongs to the Special Issue Slope Stability Analyses and Remedial Measure of Failed Slopes)

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26 pages, 10149 KiB

Open AccessArticle

Pretraining Convolutional Neural Networks for Mudstone Petrographic Thin-Section Image Classification

by Rafael Pires de Lima and David Duarte

Geosciences 2021, 11(8), 336; https://doi.org/10.3390/geosciences11080336 - 11 Aug 2021

Cited by 15 | Viewed by 3300

Abstract

Convolutional neural networks (CNN) are currently the most widely used tool for the classification of images, especially if such images have large within- and small between- group variance. Thus, one of the main factors driving the development of CNN models is the creation [...] Read more.

Convolutional neural networks (CNN) are currently the most widely used tool for the classification of images, especially if such images have large within- and small between- group variance. Thus, one of the main factors driving the development of CNN models is the creation of large, labelled computer vision datasets, some containing millions of images. Thanks to transfer learning, a technique that modifies a model trained on a primary task to execute a secondary task, the adaptation of CNN models trained on such large datasets has rapidly gained popularity in many fields of science, geosciences included. However, the trade-off between two main components of the transfer learning methodology for geoscience images is still unclear: the difference between the datasets used in the primary and secondary tasks; and the amount of available data for the primary task itself. We evaluate the performance of CNN models pretrained with different types of image datasets—specifically, dermatology, histology, and raw food—that are fine-tuned to the task of petrographic thin-section image classification. Results show that CNN models pretrained on ImageNet achieve higher accuracy due to the larger number of samples, as well as a larger variability in the samples in ImageNet compared to the other datasets evaluated. Full article

(This article belongs to the Special Issue Advances and Applications in Computational Geosciences)

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38 pages, 95091 KiB

Open AccessArticle

Trace Element Geochemistry of Chalcopyrites and Pyrites from Golpu and Nambonga North Porphyry Cu-Au Deposits, Wafi-Golpu Mineral District, Papua New Guinea

by Moira Lunge and Joseph O. Espi

Geosciences 2021, 11(8), 335; https://doi.org/10.3390/geosciences11080335 - 9 Aug 2021

Viewed by 3358

Abstract

Studying elemental geochemistry of hypogene sulphides can discriminate the hydrothermal fluids responsible for ore formation. To determine whether Golpu porphyry Cu-Au deposits are related to the Nambonga North porphyry system which is located 2.5 km apart in the Wafi-Golpu Mineral District, Papua New [...] Read more.

Studying elemental geochemistry of hypogene sulphides can discriminate the hydrothermal fluids responsible for ore formation. To determine whether Golpu porphyry Cu-Au deposits are related to the Nambonga North porphyry system which is located 2.5 km apart in the Wafi-Golpu Mineral District, Papua New Guinea, we compare the trace element compositions of drill core chalcopyrites and pyrites analysed using Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICPMS). The results for the Golpu chalcopyrites revealed high concentrations of Au, As, Se, Mo, Sb, Te and Bi and lower concentrations of Ag and Zn compared to those from Nambonga. Pd and Pt were below the detection limit in chalcopyrites for both deposits. The results for the Golpu pyrites indicated high concentrations of Pt, Au, Se, Mo, Sb, and Te and lower concentrations of Cu, Zn, As, Ag, Pb, Pd and Bi compared to those from Nambonga North. Au concentrations in the pyrites from both the porphyry deposits were higher compared to chalcopyrites, which mean that pyrite is the Au-bearing sulphide responsible for the higher Au content. In contrast, Cu values in pyrites from Nambonga North are higher than those from Golpu. Overall, it is envisaged that the ore fluids were exsolved at different times during the evolution of both porphyry deposits, although these porphyry centres may be related in space and time. Full article

(This article belongs to the Special Issue The Geoscience of the Pacific Islands Region: Theory and Practice)

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2 pages, 147 KiB

Open AccessEditorial

Editorial of Special Issue “Natural and Artificial Unsaturated Soil Slopes”

by Roberto Vassallo, Luca Comegna and Roberto Valentino

Geosciences 2021, 11(8), 334; https://doi.org/10.3390/geosciences11080334 - 7 Aug 2021

Viewed by 1651

Abstract

Natural and artificial slopes are frequently constituted, at least in part, by soils in unsaturated conditions [...] Full article

(This article belongs to the Special Issue Natural and Artificial Unsaturated Soil Slopes)

28 pages, 70660 KiB

Open AccessArticle

Modeling Shallow Landslide Susceptibility and Assessment of the Relative Importance of Predisposing Factors, through a GIS-Based Statistical Analysis

by Massimo Conforti and Fabio Ietto

Geosciences 2021, 11(8), 333; https://doi.org/10.3390/geosciences11080333 - 6 Aug 2021

Cited by 27 | Viewed by 3877

Abstract

Shallow landslides are destructive hazards and play an important role in landscape processes. The purpose of this paper is to evaluate the shallow landslide susceptibility and to investigate which predisposing factors control the spatial distribution of the collected instability phenomena. The GIS-based logistic [...] Read more.

Shallow landslides are destructive hazards and play an important role in landscape processes. The purpose of this paper is to evaluate the shallow landslide susceptibility and to investigate which predisposing factors control the spatial distribution of the collected instability phenomena. The GIS-based logistic regression model and jackknife test were respectively employed to achieve the scopes. The studied area falls in the Mesima basin, located in the southern Calabria (Italy). The research was based mainly on geomorphological study using both interpretation of Google Earth images and field surveys. Thus, 1511 shallow landslides were mapped and 18 predisposing factors (lithology, distance to faults, fault density, land use, soil texture, soil bulk density, soil erodibility, distance to streams, drainage density, elevation, slope gradient, slope aspect, local relief, plan curvature, profile curvature, TPI, TWI, and SPI) were recognized as influencing the shallow landslide susceptibility. The 70% of the collected shallow landslides were randomly divided into a training data set to build susceptibility model and the remaining 30% were used to validate the newly built model. The logistic regression model calculated the landslide probability of each pixel in the study area and produced the susceptibility map. Four classification methods were tested and compared between them, so the most reliable classification system was employed to the shallow landslide susceptibility map construction. In the susceptibility map, five classes were recognized as following: very low, low, moderate, high, and very high susceptibility. About 26.1% of the study area falls in high and very high susceptible classes and most of the landslides mapped (82.4%) occur in these classes. The accuracy of the predictive model was evaluated by using the ROC (receiver operating characteristics) curve approach, which showed an area under the curve (AUC) of 0.93, proving the excellent forecasting ability of the susceptibility model. The predisposing factors importance evaluation, using the jackknife test, revealed that slope gradient, TWI, soil texture and lithology were the most important factors; whereas, SPI, fault density and profile curvature have a least importance. According to these results, we conclude that the shallow landslide susceptibility map can be use as valuable tool both for land-use planning and for management and mitigation of the shallow landslide risk in the study area. Full article

(This article belongs to the Section Natural Hazards)

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20 pages, 40942 KiB

Open AccessArticle

The Study of Uranium Accumulation in Marine Bottom Sediments: Effect of Redox Conditions at the Time of Sedimentation

by Nadezhda Khaustova, Yulia Tikhomirova, Svetlana Korost, Elena Poludetkina, Andrey Voropaev, Mikhail Mironenko and Mikhail Spasennykh

Geosciences 2021, 11(8), 332; https://doi.org/10.3390/geosciences11080332 - 6 Aug 2021

Cited by 8 | Viewed by 2828

Abstract

To evaluate the effect of redox conditions at the sedimentation stage on uranium content and U/TOC ratio in marine source rocks, we analyzed the accumulation of uranium in modern marine bottom sediments formed in different redox conditions. The behavior of uranium from bottom [...] Read more.

To evaluate the effect of redox conditions at the sedimentation stage on uranium content and U/TOC ratio in marine source rocks, we analyzed the accumulation of uranium in modern marine bottom sediments formed in different redox conditions. The behavior of uranium from bottom sediments formed in oxidizing and sub-oxidizing settings has been studied on the sediments of the Upper Pleistocene–Holocene age accumulated in the coastal area of the White Sea (Kandalaksha Gulf). We studied the content of uranium, Eh, pH, TOC, C, H, N, and S element and isotope compositions and other parameters in two sampled columns of bottom sediments at a depth of 0–2.5 m. The composition of sediments was typical for the shelf zone where marine genesis mixes with the continental run-off. The upper layer of sediments (0–50 cm) were characterized by oxidizing conditions (Eh ~ 400 mV); with the increase in depth, redox conditions changed from oxidizing to reducing (−0 ÷ −200 mV). The uranium concentration in the upper layer was 1–1.5 ppm, U/TOC ratio varied in the range of 0.8–1.1 ppmU/%TOC. The uranium content and U/TOC ratio increased up to the values of 2.6 ppm and 1.4 ppmU/%TOC at a depth of 0.5–2.5 m, respectively, but the general content of uranium in the studied environment was close to the values characterizing continental run-off. The results obtained for the White Sea sediments were compared with the sediment of the Black Sea, formed in the anoxic conditions of hydrogen sulfide contamination. In these conditions, the uranium content varied from 10 to 20 ppm. The obtained data were interpreted using thermodynamic modeling of the uranium forms in the seawater at different pH and Eh. This study demonstrated that the change of redox conditions from oxidizing to reducing leads to increased uranium content due to a decrease in uranium’s solubility in water. These results show that oxidation–reduction potential could be one of the most important factors controlling uranium content in black shales formed in the marine environment. Full article

(This article belongs to the Special Issue Radioisotopes Studies in the Geosciences)

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20 pages, 36396 KiB

Open AccessArticle

Slope Failure in a Period of Increased Landslide Activity: Sennwald Rock Avalanche, Switzerland

by Selçuk Aksay, Susan Ivy-Ochs, Kristina Hippe, Lorenz Grämiger and Christof Vockenhuber

Geosciences 2021, 11(8), 331; https://doi.org/10.3390/geosciences11080331 - 5 Aug 2021

Cited by 2 | Viewed by 3963

Abstract

The Säntis nappe is a complex fold-and-thrust structure in eastern Switzerland, consisting of numerous tectonic discontinuities and a range of hillslopes prone to landsliding and large slope failures that modify the topography irreversibly. A slope failure, namely the Sennwald rock avalanche, occurred in [...] Read more.

The Säntis nappe is a complex fold-and-thrust structure in eastern Switzerland, consisting of numerous tectonic discontinuities and a range of hillslopes prone to landsliding and large slope failures that modify the topography irreversibly. A slope failure, namely the Sennwald rock avalanche, occurred in the southeast wall of this fold-and-thrust structure due to the rock failure of Lower Cretaceous Helvetic limestones along the Rhine River valley. In this research, this palaeolandslide is examined in a multidisciplinary approach for the first time with detection and mapping of avalanche deposits, dynamic run-out modelling and cosmogenic nuclide dating. During the rock failure, the avalanche deposits were transported down the hillslope in a spreading-deck fashion, roughly preserving the original stratigraphic sequence. The distribution of landslide deposits and surface exposure age of the rock failure support the hypothesis that the landslide was a single catastrophic event. The ³⁶Cl surface exposure age of avalanche deposits indicates an age of 4.3 ± 0.5 ka. This time coincides with a notably wet climate period, noted as a conditioning factor for landslides across the Alps in the mid-Holocene. The contemporaneity of our event at its location in the Eastern Alps provide additional support for the contention of increased regional seismic activity in mid-Holocene. Full article

(This article belongs to the Special Issue Cutting Edge Earth Sciences: Three Decades of Cosmogenic Nuclides)

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22 pages, 46515 KiB

Open AccessArticle

Storm Driven Migration of the Napatree Barrier, Rhode Island, USA

by Bryan A. Oakley

Geosciences 2021, 11(8), 330; https://doi.org/10.3390/geosciences11080330 - 5 Aug 2021

Cited by 3 | Viewed by 3770

Abstract

Napatree Point, an isolated barrier in southern Rhode Island, provides a case study of barrier spit migration via storm driven overwash and washover fan migration. Documented shoreline changes using historical surveys and vertical aerial photographs show that the barrier had little in the [...] Read more.

Napatree Point, an isolated barrier in southern Rhode Island, provides a case study of barrier spit migration via storm driven overwash and washover fan migration. Documented shoreline changes using historical surveys and vertical aerial photographs show that the barrier had little in the way of net change in position between 1883 and 1939, including the impact of the 1938 hurricane. The barrier retreated rapidly between 1945 and 1975, driven by both tropical and extra-tropical storms. The shoreline position has been largely static since 1975. The removal of the foredune during the 1938 hurricane facilitated landward shoreline migration in subsequent lower intensity storms. Dune recovery following the 1962 Ash Wednesday storm has been allowed due to limited overwash and barrier migration over the last several decades. Shoreline change rates during the period from 1945–1975 were more than double the rate of shoreline change between 1939 and 2014 and triple the rate between 1883 and 2014, exceeding the positional uncertainty of these shoreline pairs. The long-term shoreline change rates used to calculate coastal setbacks in Rhode Island likely underestimate the potential for rapid shoreline retreat over shorter time periods, particularly in a cluster of storm activity. While sea-level rise has increased since 1975, the barrier has not migrated, highlighting the importance of storms in barrier migration. Full article

(This article belongs to the Special Issue Shoreline Dynamics and Beach Erosion)

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22 pages, 7792 KiB

Open AccessArticle

Evolution of a Late Miocene Deep-Water Depositional System in the Southern Taranaki Basin, New Zealand

by Clayton Silver and Heather Bedle

Geosciences 2021, 11(8), 329; https://doi.org/10.3390/geosciences11080329 - 3 Aug 2021

Cited by 5 | Viewed by 3008

Abstract

A long-standing problem in the understanding of deep-water turbidite reservoirs relates to how the three-dimensional evolution of deep-water channel systems evolve in response to channel filling on spatiotemporal scales, and how depositional environments affect channel architecture. The 3-D structure and temporal evolution of [...] Read more.

A long-standing problem in the understanding of deep-water turbidite reservoirs relates to how the three-dimensional evolution of deep-water channel systems evolve in response to channel filling on spatiotemporal scales, and how depositional environments affect channel architecture. The 3-D structure and temporal evolution of late Miocene deep-water channel complexes in the southern Taranaki Basin, New Zealand is investigated, and the geometry, distribution, and stacking patterns of the channel complexes are analyzed. Two recently acquired 3-D seismic datasets, the Pipeline-3D (proximal) and Hector-3D (distal) are analyzed. These surveys provide detailed imaging of late Miocene deep-water channel systems, allowing for the assessment of the intricate geometry and seismic geomorphology of the systems. Seismic attributes resolve the channel bodies and the associated architectural elements. Spectral decomposition, amplitude curvature, and coherence attributes reveal NW-trending straight to low-sinuosity channels and less prominent NE-trending high-sinuosity feeder channels. Stratal slices across the seismic datasets better characterize the architectural elements. The mapped turbidite systems transition from low-sinuosity to meandering high-sinuosity patterns, likely caused by a change in the shelf-slope gradient due to localized structural relief. Stacking facies patterns within the channel systems reveal the temporal variation from a depositional environment characterized by sediment bypass to vertically aggrading channel systems. Full article

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22 pages, 48003 KiB

Open AccessArticle

The March 2021 Damasi Earthquake Sequence, Central Greece: Reactivation Evidence across the Westward Propagating Tyrnavos Graben

by Ioannis K. Koukouvelas, Konstantinos G. Nikolakopoulos, Aggeliki Kyriou, Riccardo Caputo, Alexandros Belesis, Vasiliki Zygouri, Sotirios Verroios, Dionysios Apostolopoulos and Ioannis Tsentzos

Geosciences 2021, 11(8), 328; https://doi.org/10.3390/geosciences11080328 - 2 Aug 2021

Cited by 24 | Viewed by 4162

Abstract

On 3 March 2021, a strong shallow earthquake affected northern Thessaly, Greece, with an epicenter close to Damasi village causing significant destruction of many stone houses. In this contribution, we provide fieldwork observations, satellite radar interferometry, mapping of the active faults exposed in [...] Read more.

On 3 March 2021, a strong shallow earthquake affected northern Thessaly, Greece, with an epicenter close to Damasi village causing significant destruction of many stone houses. In this contribution, we provide fieldwork observations, satellite radar interferometry, mapping of the active faults exposed in the epicentral area, liquefactions and coseismic surface ruptures, and preliminary geomorphological analyses of the epicentral area. The geomorphological analysis is based on air photographs, digital surface models analysis, Real-Time Kinematik (RTK) measurements with Global Navigation Satellite System (GNSS) receivers, and data from UAV flight campaigns. Although the seismotectonic setting of the area is complex and there is an apparent mismatch between field and interferometric data, the results of our investigations suggest that at least three fault segments were reactivated by the major shocks of the March seismic sequence. These tectonic structureslikely represent the westward propagation of the Tyrnavos Graben, where newly formed and inherited low-angle faults interplay in a complex manner. Full article

(This article belongs to the Special Issue Morphogenic Faulting: Current Practices and Future Challenges)

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30 pages, 6958 KiB

Open AccessReview

Multiple Sulfur Isotope Geochemistry during the Permian-Triassic Transition

by Masafumi Saitoh

Geosciences 2021, 11(8), 327; https://doi.org/10.3390/geosciences11080327 - 1 Aug 2021

Cited by 3 | Viewed by 3257

Abstract

The end-Permian mass extinction was the largest biodiversity crisis in the Phanerozoic. Based on characteristic negative ∆³³S signals of sedimentary pyrite, previous multiple sulfur isotope studies suggested shoaling of anoxic/sulfidic deep-waters onto a shelf, leading to the shallow-marine extinction. However, the [...] Read more.

The end-Permian mass extinction was the largest biodiversity crisis in the Phanerozoic. Based on characteristic negative ∆³³S signals of sedimentary pyrite, previous multiple sulfur isotope studies suggested shoaling of anoxic/sulfidic deep-waters onto a shelf, leading to the shallow-marine extinction. However, the validity of this shoaling model has been controversial. I compiled previously-reported multiple sulfur isotope records during the Permian-Triassic transition interval, and examined a stratigraphic relationship between the extinction horizon, redox oscillation in the depositional settings, and the multiple sulfur isotope record in each studied section. The compilation shows that the negative ∆³³S signals do not correspond clearly to the extinction horizon or to the benthic anoxia/euxinia in the studied sections. The compilation also documents that the multiple sulfur isotope records during the Permian-Triassic transition are substantially variable, and that the negative ∆³³S signals were observed in various types of sediments including shallow-marine carbonates, carbonates/siltstones of relatively deep-water facies, and abyssal deep-sea cherts. Those observations allow me to infer that the negative ∆³³S signal is not a robust indicator of shoaling. Rather, this isotopic signal may reflect substantial sulfur isotope heterogeneity in the sediments controlled by local factors. Full article

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17 pages, 5141 KiB

Open AccessArticle

Holocene Sea-Level Changes in Southern Brazil Based on High-Resolution Radar Stratigraphy

by Eduardo Guimarães Barboza, Sergio Rebello Dillenburg, Matias do Nascimento Ritter, Rodolfo José Angulo, Anderson Biancini da Silva, Maria Luiza Correaa da Camara Rosa, Felipe Caron and Maria Cristina de Souza

Geosciences 2021, 11(8), 326; https://doi.org/10.3390/geosciences11080326 - 31 Jul 2021

Cited by 32 | Viewed by 3237

Abstract

This paper focuses on high-resolution coastal stratigraphy data, which were revealed by the Ground Penetrating Radar (GPR) system. Surveys performed with GPR on the surface of prograded barriers reveal patterns of reflections that allow the interpretation of the geometry and stratigraphy of coastal [...] Read more.

This paper focuses on high-resolution coastal stratigraphy data, which were revealed by the Ground Penetrating Radar (GPR) system. Surveys performed with GPR on the surface of prograded barriers reveal patterns of reflections that allow the interpretation of the geometry and stratigraphy of coastal deposits in a continuous mode. At the Curumim prograded barrier in southern Brazil (29°30′ S–49°53′ W), a two-dimensional transverse GPR survey revealed, with high precision, a serial of contacts between aeolian deposits of relict foredunes and relict beach deposits that have a strong correlation with sea level. In a 4 km GPR profile, a total of 24 of these contacts were identified. The high accurate spatial positioning of the contacts combined with Optical Stimulated Luminescence dating resulted in the first confident sea-level curve that tells the history of sea-level changes during the last 7 ka on the southernmost sector of the Brazilian coast. The curve shows that sea-level was still rising before 6 ka BP, with a maximum level of 1.9 m reached close to 5 ka BP; after that, sea-level started to falling slowly until around 4 ka BP when fall accelerated. Full article

(This article belongs to the Special Issue Quaternary Stratigraphy of Alluvial and Coastal Plains: Recent Advances and Potential Applications)

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33 pages, 9676 KiB

Open AccessArticle

Fluid-Rock Interactions in a Paleo-Geothermal Reservoir (Noble Hills Granite, California, USA). Part 1: Granite Pervasive Alteration Processes away from Fracture Zones

by Johanne Klee, Sébastien Potel, Béatrice A. Ledésert, Ronan L. Hébert, Arezki Chabani, Pascal Barrier and Ghislain Trullenque

Geosciences 2021, 11(8), 325; https://doi.org/10.3390/geosciences11080325 - 31 Jul 2021

Cited by 11 | Viewed by 3616

Abstract

Only few data from geothermal exploited reservoirs are available due to the restricted accessibility by drilling, which limits the understanding of the entire reservoir. Thus, analogue investigations are needed and were performed in the framework of the H2020 MEET project. The Noble Hills [...] Read more.

Only few data from geothermal exploited reservoirs are available due to the restricted accessibility by drilling, which limits the understanding of the entire reservoir. Thus, analogue investigations are needed and were performed in the framework of the H2020 MEET project. The Noble Hills range, located along the southern branch of the Death Valley pull-apart (CA, USA), has been selected as a possible granitic paleo-reservoir. The aim is to characterize the pervasive alteration processes affecting this granite, away from the influence of the faults, in terms of mineralogical, petrophysical and chemical changes. Various methods were used as petrographic, geochemical and petrophysical analyses. Mineral changes, clay mineralogy, bulk rock chemical composition, calcite content and porosity were determined on different granite samples, collected in the Noble Hills granite, far from the faults and in the Owlshead Mountains, north of the Noble Hills, considered as its protolith. In order to complete the granite characterization, the metamorphic grade has been studied through the Noble Hills granite body. This complete characterization has allowed distinguishing the occurrence of three stages of alteration: (1) a pervasive propylitic alteration characterized by calcite-corrensite-epidote-K-white mica assemblage, (2) a more local one, only present in the Noble Hills granite, producing illite, kaolinite, illite/smectite, calcite and oxides, characteristic of the argillic alteration, which overprints the propylitic alteration and (3) weathering evidenced by the presence of montmorillonite in the Owlshead Mountains, which is considered as negligible in both granites. Alteration was also outlined by the correlation of the loss on ignition, representing the hydration rate, to porosity, calcite content and chemical composition. Moreover, the Kübler Index calculated from illite crystals allowed to identify a NW-SE temperature gradient in the Noble Hills. Full article

(This article belongs to the Special Issue Enhanced Geothermal Systems and other Deep Geothermal Applications throughout Europe: The MEET Project)

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24 pages, 15719 KiB

Open AccessArticle

Cloud Masks Derived from the Mars Daily Global Maps and an Application to the Tropical Cloud Belt on Mars

by Huiqun Wang and Gonzalo González Abad

Geosciences 2021, 11(8), 324; https://doi.org/10.3390/geosciences11080324 - 31 Jul 2021

Cited by 6 | Viewed by 2614

Abstract

An image processing technique is used to derive cloud masks from the color Mars Daily Global Maps (MDGMs) that are composed from the Mars Reconnaissance Orbiter (MRO) Mars Color Imager (MARCI) wide-angle image swaths. The blue channel of each MDGM is used to [...] Read more.

An image processing technique is used to derive cloud masks from the color Mars Daily Global Maps (MDGMs) that are composed from the Mars Reconnaissance Orbiter (MRO) Mars Color Imager (MARCI) wide-angle image swaths. The blue channel of each MDGM is used to select cloud candidates and the blue-to-red ratio map is compared with a reference ratio map to filter out false positives. Quality control is performed manually. The derived cloud masks cover 1 Mars year from the summer of Mars year (MY) 28 to the summer of MY 29. The product has a 0.1° longitude by 0.1° latitude resolution and is available each day. This makes it possible to characterize the evolution of the tropical cloud belt from several new perspectives. The tropical cloud belt steadily builds up during northern spring and early summer, peaks near the early- to mid-summer transitional period, and rapidly declines afterward. From the perspective of cloud occurrence frequency and time mean, the cloud belt appears meandrous and zonally discontinuous, with minima in the Amazonis Planitia and Arabia Terra longitudinal sectors. A pronounced cloud branch diverges from the main cloud belt and extends from the Valles Marineris towards the Noachis and Hellas region. The cloud belt exhibits noticeable oscillatory behavior whereby cloud brightening alternates between the western and eastern hemispheres near the equator with a periodicity between 20 and 30 sols. The cloud belt oscillation occurred each Mars year around L_s = 140°, except for the Mars years when intense dust storms made disruptions. The phenomenon appears to be associated with an eastward propagating equatorial Kelvin wave with zonal wavenumber 1. This wave has a much longer wave period than the diurnal and semidiurnal Kelvin waves discussed in most of the previous studies and may be an important factor for the intra-seasonal variability of the tropical cloud belt. The convolution of clouds’ local time variation with MRO’s orbit shift pattern results in a seemingly highly regular 5-day traveling wave in Hovmöller diagrams of cloud masks. Full article

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