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Geosciences, Volume 12, Issue 3 (March 2022) – 39 articles

Cover Story (view full-size image): A total of 325 seafloor mounds and 204 buried mounds were characterized on the upper continental slope of the northern Alboran Sea by means of an analysis of their morphosedimentary features and the contemporary and past benthic and demersal habitat-forming species. Transparent facies characterize the mounds, which root on at least six erosive surfaces, indicating different growth stages. Remains of colonial scleractinians, rhodoliths, and bivalves were detected, and their role as potential mound-forming species, possibly during the late Pleistocene, is discussed due to the occurrence on top of some mounds of abundant remains of rhodoliths and boreal guest fauna (e.g., Modiolus modiolus), which declined in the western Mediterranean after Termination 1a of the Last Glacial (Late Pleistocene). View this paper
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Article
Salinas and “Saltscape” as a Geological Heritage with a Strong Potential for Tourism and Geoeducation
Geosciences 2022, 12(3), 141; https://doi.org/10.3390/geosciences12030141 - 21 Mar 2022
Cited by 2 | Viewed by 859
Abstract
Salinas and saltscapes are relevant geoheritage sites with important implications on socioeconomic activities beyond the production of salt, particularly tourism and education. As cultural landscapes, they also have implications related to the identity of their communities. This work presents the study of the [...] Read more.
Salinas and saltscapes are relevant geoheritage sites with important implications on socioeconomic activities beyond the production of salt, particularly tourism and education. As cultural landscapes, they also have implications related to the identity of their communities. This work presents the study of the patrimonialization processes of four sites in Europe (Añana in Spain, Guérande in France, Læsø in Denmark, and Sečovlje in Slovenia). Lessons obtained from these processes may contribute to the recovery and valuation of similar saltscapes and other forms of geoheritage. The study is based on interviews with relevant stakeholders, a survey of the related grey and scientific literature, and a simplified SWOT analysis. Despite their differences in historical background and current management, all four sites share features that have contributed to the success of their patrimonialization processes, such as having a dedicated entity for this purpose or being protected in some way. They also share common threats that need to be addressed, such as the banalization of the heritage discourse. Other saltscapes and geoheritage sites in general may benefit from these common features, which should serve as an inspiration and not as a template. In the end, shifting from a little-known productive, (proto-)industrial activity toward a sustainable, multifunctional landscape in which geoeducation and tourism are paramount contributes to a more resilient and educated society. Full article
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Article
Console-Based Mapping of Mongolia Using GMT Cartographic Scripting Toolset for Processing TerraClimate Data
Geosciences 2022, 12(3), 140; https://doi.org/10.3390/geosciences12030140 - 21 Mar 2022
Cited by 3 | Viewed by 930
Abstract
This paper explores spatial variability of the ten climatic variables of Mongolia in 2019: average minimal and maximal temperatures, wind speed, soil moisture, downward surface shortwave radiation (DSRAD), snow water equivalent (SWE), vapor pressure deficit (VPD), vapor pressure anomaly (VAP), monthly precipitation and [...] Read more.
This paper explores spatial variability of the ten climatic variables of Mongolia in 2019: average minimal and maximal temperatures, wind speed, soil moisture, downward surface shortwave radiation (DSRAD), snow water equivalent (SWE), vapor pressure deficit (VPD), vapor pressure anomaly (VAP), monthly precipitation and Palmer Drought Severity Index (PDSI). The PDSI demonstrates the simplified soil water balance estimating relative soil moisture conditions in Mongolia. The research presents mapping of the climate datasets derived from TerraClimate open source repository of the meteorological and climate measurements in NetCDF format. The methodology presented the compiled observations of Mongolia visualised by GMT coding approach using Generic Mapping Tools (GMT) cartographic scripting toolset. The results present 10 new maps of climate data over Mongolia made using automated cartographic techniques of GMT. Spatial environmental and climate analysis were conducted which determine relative distribution of PDSI and temperature extremes, precipitation and soil moisture, wind speed and DSRAD. The DSRAD showed minimum at 40 Wm2, maximum at 113 Wm2 in the Gobi Desert region, SWE (up to 491 mm), VAP and VPD compared with landmass parameters represent powerful cartographic tools to address complex regional climate and environmental issues in Mongolia, a country with contrasting topography, extreme climate conditions and unique environmental setting. Full article
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Article
Geophysical and Geological Views of Potential Water Resources in the North-Eastern Adriatic Sea
Geosciences 2022, 12(3), 139; https://doi.org/10.3390/geosciences12030139 - 18 Mar 2022
Cited by 2 | Viewed by 698
Abstract
The increasing demand for freshwater requires the identification of additional and less-conventional water resources. Amongst these, offshore freshwater systems have been investigated in different parts of the world to provide new opportunities to face increasing water requests. Here we focus on the north-eastern [...] Read more.
The increasing demand for freshwater requires the identification of additional and less-conventional water resources. Amongst these, offshore freshwater systems have been investigated in different parts of the world to provide new opportunities to face increasing water requests. Here we focus on the north-eastern Adriatic Sea, where offshore aquifers could be present as a continuation of onshore ones. Geophysical data, in particular offshore seismic data, and onshore and offshore well data, are interpreted and integrated to characterise the hydrogeological setting via the interpretation of seismo-stratigraphic sequences. We focus our attention on two areas located in the proximity of the Tagliamento and Isonzo deltas. Well and seismic data indicate that the Quaternary sediments, that extend from onshore to offshore areas, are the most promising from an offshore freshwater resources point of view, while the several kilometres thick pre-Quaternary carbonate and terrigenous sequences likely host mainly salty waters. Full article
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Article
Methanogenesis from Mineral Carbonates, a Potential Indicator for Life on Mars
Geosciences 2022, 12(3), 138; https://doi.org/10.3390/geosciences12030138 - 16 Mar 2022
Viewed by 1064
Abstract
Priorities for the exploration of Mars involve the identification and observation of biosignatures that indicate the existence of life on the planet. The atmosphere and composition of the sediments on Mars suggest suitability for anaerobic chemolithotrophic metabolism. Carbonates are often considered as morphological [...] Read more.
Priorities for the exploration of Mars involve the identification and observation of biosignatures that indicate the existence of life on the planet. The atmosphere and composition of the sediments on Mars suggest suitability for anaerobic chemolithotrophic metabolism. Carbonates are often considered as morphological biosignatures, such as stromatolites, but have not been considered as potential electron acceptors. Within the present study, hydrogenotrophic methanogen enrichments were generated from sediments that had received significant quantities of lime from industrial processes (lime kiln/steel production). These enrichments were then supplemented with calcium carbonate powder or marble chips as a sole source of carbon. These microcosms saw a release of inorganic carbon into the liquid phase, which was subsequently removed, resulting in the generation of methane, with 0.37 ± 0.09 mmoles of methane observed in the steel sediment enrichments supplemented with calcium carbonate powder. The steel sediment microcosms and lime sediments with carbonate powder enrichments were dominated by Methanobacterium sp., whilst the lime/marble enrichments were more diverse, containing varying proportions of Methanomassiliicoccus, Methanoculleus and Methanosarcina sp. In all microcosm experiments, acetic acid was detected in the liquid phase. Our results indicate that chemolithotrophic methanogenesis should be considered when determining biosignatures for life on Mars. Full article
(This article belongs to the Special Issue Current and Future Perspectives in Microbial Carbonate Precipitation)
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Unnatural Cycles: Anthropogenic Disruption to Health and Planetary Functions
Geosciences 2022, 12(3), 137; https://doi.org/10.3390/geosciences12030137 - 15 Mar 2022
Viewed by 740
Abstract
Natural cycles underpin the very stuff of life. In this commentary we consider unnatural cycles: that is, anthropogenic activities which have a circularity, but whose nature is to have a detrimental effect on human health, exacerbating existing problems. Natural cycles have feedback loops, [...] Read more.
Natural cycles underpin the very stuff of life. In this commentary we consider unnatural cycles: that is, anthropogenic activities which have a circularity, but whose nature is to have a detrimental effect on human health, exacerbating existing problems. Natural cycles have feedback loops, some of which have recently come to light, with an understanding that everything is connected in some way. In health, feedback loops are imperative in homeostatic mechanisms. However, in the unnatural cycle the feedback loops serve to reinforce (and in some cases amplify) negative problems. We offer a commentary on an unnatural cycle moving from air quality to lung function and back to air quality; we call this the lung disease unnatural cycle. We suggest where links occur, and where wider consideration of interactions between various disciplines can lead to breaking this unnatural (or vicious) cycle, changing it to a healthy cycle where individual health can be improved, along with better global scale outcomes. We suggest that many activities within this unnatural cycle occur within silos. However, the improved cycle incorporates joint activities at geological, health, and financial levels, to the mutual benefit of all, breaking the unnatural cycle and improving health, life, and financial costs. Full article
(This article belongs to the Special Issue Medical Geology in the Urban Environment)
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Article
Receiver Function Imaging of the Crustal Structure Beneath Northern Taiwan Using Dense Linear Arrays
Geosciences 2022, 12(3), 136; https://doi.org/10.3390/geosciences12030136 - 15 Mar 2022
Viewed by 704
Abstract
In order to realize the crustal structure in Taiwan, the receiver function method was used to analyze the teleseismic waveforms recorded by two orthogonal broadband linear arrays deployed in northern Taiwan in the east–west and south–north directions by the TAiwan Integrated GEodynamics Research [...] Read more.
In order to realize the crustal structure in Taiwan, the receiver function method was used to analyze the teleseismic waveforms recorded by two orthogonal broadband linear arrays deployed in northern Taiwan in the east–west and south–north directions by the TAiwan Integrated GEodynamics Research (TAIGER) project from 2007 to 2009. By incorporation with Common Conversion Point (CCP) stacking, the Moho discontinuities beneath northern Taiwan were imaged. Based on the CCP stack of receiver functions in the east–west direction array, a collision boundary between the Philippine Sea Plate and the Eurasian Plate appears at the east of Taiwan. The Moho depth of the Eurasian Plate in west Taiwan is flat and 30 km; the Moho depth of the Philippine Sea Plate below the Central Mountain Range is about 55 km; in the east, the Moho depth of the Ryukyu arc is about 40 km. The south–north profile shows a brittle–ductile transition zone at depths of 15–20 km beneath central Taiwan from south to north. Moreover, the Moho depth of the Eurasian Plate is about 20–25 km in northern Taiwan. The Moho depth appears to deepen from north to south. The deepest Moho is located at the junction of the two profile lines, the Philippine Sea Plate, and has a depth of 60 km. According to these Moho depths, the crustal structure is thin and flat in the west part of northern Taiwan which is similar to the thin-skin model. However, the lithosphere is deformed and forms the mountain root in the east part which is similar to the lithospheric collision model. Full article
(This article belongs to the Section Geophysics)
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Article
Extreme Sea Surges, Tsunamis and Pluvial Flooding Events during the Last ~1000 Years in the Semi-Arid Wetland, Coquimbo Chile
Geosciences 2022, 12(3), 135; https://doi.org/10.3390/geosciences12030135 - 14 Mar 2022
Viewed by 952
Abstract
The coast of Chile has been exposed to marine submersion events from storm surges, tsunamis and flooding due to heavy rains. We present evidence of these events using sedimentary records that cover the last 1000 years in the Pachingo wetland. Two sediment cores [...] Read more.
The coast of Chile has been exposed to marine submersion events from storm surges, tsunamis and flooding due to heavy rains. We present evidence of these events using sedimentary records that cover the last 1000 years in the Pachingo wetland. Two sediment cores were analyzed for granulometry, XRF, pollen, diatoms and TOC. Three extreme events produced by marine submersion and three by pluvial flooding during El Niño episodes were identified. Geochronology was determined using a conventional dating method using 14C, 210Pbxs and 137Cs). The older marine event (E1) was heavier, identified by a coarser grain size, high content of seashells, greater amount of gravel and the presence of two rip-up clasts, which seems to fit with the tsunami of 1420 Cal AD. The other two events (E3 and E5) may correspond to the 1922 (E3) tsunami and the 1984 (E5) storm waves, corroborated with a nearshore wave simulation model for this period (SWAM). On the other hand, the three flood events (E2, E4, E6) all occurred during episodes of El Niño in 1997 (E6), 1957 (E4) and 1600 (E6), represented by layers of fine-grain sands and wood charcoal remains. Full article
(This article belongs to the Section Natural Hazards)
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Article
Prototype Scale Evaluation of Non-Newtonian Algorithms in HEC-RAS: Mud and Debris Flow Case Studies of Santa Barbara and Brumadinho
Geosciences 2022, 12(3), 134; https://doi.org/10.3390/geosciences12030134 - 14 Mar 2022
Viewed by 1200
Abstract
The Santa Barbara post-wildfire debris flows and the Brumadinho tailing-dam failure were two of the most catastrophic flood events of the late 2010s. Both these events carried so much solid-phase material, that classic, clear-water, flood risk approaches cannot replicate them, or forecast other [...] Read more.
The Santa Barbara post-wildfire debris flows and the Brumadinho tailing-dam failure were two of the most catastrophic flood events of the late 2010s. Both these events carried so much solid-phase material, that classic, clear-water, flood risk approaches cannot replicate them, or forecast other events like them. This case study applied the new non-Newtonian features in HEC-RAS 6.1 to these two events, testing the most widely used flood risk model on the two most common mud and debris flow hazards (post-wildfire floods and mine tailing dam failures). HEC-RAS reproduced the inundation boundaries and the event timing (where available) for both events. The ratio between the largest debris flow clasts and the channel size, parametric trade-offs, the “convex” alluvial plain topography, and the stochasticity introduced by urban infrastructure made the Santa Barbara modeling more difficult and less precise than Brumadinho. Despite these challenges, the results provide prototype scale validation and verification of these new tools in this widely applied flood risk model. Full article
(This article belongs to the Special Issue Recent Advances on Sediment Transport and River Morphodynamics)
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Article
Palaeoecological Implications of Lower-Middle Triassic Stromatolites and Microbe-Metazoan Build-Ups in the Germanic Basin: Insights into the Aftermath of the Permian–Triassic Crisis
Geosciences 2022, 12(3), 133; https://doi.org/10.3390/geosciences12030133 - 14 Mar 2022
Cited by 1 | Viewed by 838
Abstract
Following the end-Permian crisis, microbialites were ubiquitous worldwide. For instance, Triassic deposits in the Germanic Basin provide a rich record of stromatolites as well as of microbe-metazoan build-ups with nonspicular demosponges. Despite their palaeoecological significance, however, all of these microbialites have only rarely [...] Read more.
Following the end-Permian crisis, microbialites were ubiquitous worldwide. For instance, Triassic deposits in the Germanic Basin provide a rich record of stromatolites as well as of microbe-metazoan build-ups with nonspicular demosponges. Despite their palaeoecological significance, however, all of these microbialites have only rarely been studied. This study aims to fill this gap by examining and comparing microbialites from the Upper Buntsandstein (Olenekian, Lower Triassic) and the lower Middle Muschelkalk (Anisian, Middle Triassic) in Germany. By combining analytical petrography (optical microscopy, micro X-ray fluorescence, and Raman spectroscopy) and geochemistry (δ13Ccarb, δ18Ocarb), we show that all the studied microbialites formed in slightly evaporitic environments. Olenekian deposits in the Jena area and Anisian strata at Werbach contain stromatolites. Anisian successions at Hardheim, in contrast, host microbe-metazoan build-ups. Thus, the key difference is the absence or presence of nonspicular demosponges in microbialites. It is plausible that microbes and nonspicular demosponges had a mutualistic relationship, and it is tempting to speculate that the investigated microbial-metazoan build-ups reflect an ancient evolutionary and ecological association. The widespread occurrence of microbialites (e.g., stromatolites/microbe-metazoan build-ups) after the catastrophe may have resulted from suppressed ecological competition and the presence of vacant ecological niches. The distribution of stromatolites and/or microbe-metazoan build-ups might have been controlled by subtle differences in salinity and water depth, the latter influencing hydrodynamic processes and nutrient supply down to the microscale. To obtain a more complete picture of the distribution of such build-ups in the earth’s history, more fossil records need to be (re)investigated. For the time being, environmental and taphonomic studies of modern nonspicular demosponges are urgently required. Full article
(This article belongs to the Special Issue Advances in Carbonate Sedimentology)
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Article
Unsupervised Machine Learning, Multi-Attribute Analysis for Identifying Low Saturation Gas Reservoirs within the Deepwater Gulf of Mexico, and Offshore Australia
Geosciences 2022, 12(3), 132; https://doi.org/10.3390/geosciences12030132 - 14 Mar 2022
Viewed by 840
Abstract
An effective method of identifying and discriminating undersaturated gas accumulations remains unresolved, resulting in uncertainty in hydrocarbon exploration. To address this problem, an unsupervised machine learning multi-attribute analysis is performed on 3D post-stack seismic data over several blocks within the deepwater Gulf of [...] Read more.
An effective method of identifying and discriminating undersaturated gas accumulations remains unresolved, resulting in uncertainty in hydrocarbon exploration. To address this problem, an unsupervised machine learning multi-attribute analysis is performed on 3D post-stack seismic data over several blocks within the deepwater Gulf of Mexico and within the Carnarvon Basin, offshore Australia. Results reveal that low-saturation gas (LSG) reservoirs can be discriminated from high-saturation gas (HSG) reservoirs by using a combination of instantaneous attributes that are sensitive to small amplitude, frequency, and phase anomalies with self-organizing maps (SOMs). This methodology shows promise for de-risking prospects, even if it is not quantitative, particularly in frontier and exploration basins where wells may not exist or be very limited. However, this method only proved to be successful within the Gulf of Mexico and yielded limited results in the Carnarvon Basin. This difference is most likely due to the Carnarvon Basin having a different amplitude response resulting from a different burial history and fluid saturations when compared to the Gulf of Mexico. Therefore, this method is non-transferrable, and a different combination of attributes may be needed in other LSG-prone basins. Full article
(This article belongs to the Section Geophysics)
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Article
Fostering Geoethics in Flood Risk Reduction: Lessons Learned from the EU Project LIFE PRIMES
Geosciences 2022, 12(3), 131; https://doi.org/10.3390/geosciences12030131 - 11 Mar 2022
Viewed by 750
Abstract
Despite the concrete evidence of human responsibilities with the ongoing environmental crisis, tangible changes toward low disaster-risk development models are slow in coming and delayed in implementation. This paper discusses the principles of geoethics underpinning flood risk reduction by analyzing the results of [...] Read more.
Despite the concrete evidence of human responsibilities with the ongoing environmental crisis, tangible changes toward low disaster-risk development models are slow in coming and delayed in implementation. This paper discusses the principles of geoethics underpinning flood risk reduction by analyzing the results of the EU project LIFE PRIMES (Preventing flooding RIsks by Making resilient communitiES). Through the administration of a questionnaire, issues of flood literacy, effective communication and individual responsibility concerning flood hazard and exposure were investigated. Directly engaging local communities, the LIFE PRIMES project appears to have increased citizens attention toward environmental ethics, thus providing an encouraging perspective for appropriate human–environment interaction. Full article
(This article belongs to the Collection Ethics in Geosciences)
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Article
Data-Driven Geothermal Reservoir Modeling: Estimating Permeability Distributions by Machine Learning
Geosciences 2022, 12(3), 130; https://doi.org/10.3390/geosciences12030130 - 11 Mar 2022
Viewed by 795
Abstract
Numerical modeling for geothermal reservoir engineering is a crucial process to evaluate the performance of the reservoir and to develop strategies for the future development. The governing equations in the geothermal reservoir models consist of several constitutive parameters, and each parameter is given [...] Read more.
Numerical modeling for geothermal reservoir engineering is a crucial process to evaluate the performance of the reservoir and to develop strategies for the future development. The governing equations in the geothermal reservoir models consist of several constitutive parameters, and each parameter is given to a large number of simulation grids. Thus, the combinations of parameters we need to estimate are almost limitless. Although several inverse analysis algorithms have been developed, determining the constitutive parameters in the reservoir model is still a matter of trial-and-error estimation in actual practice, and is largely based on the experience of the analyst. There are several parameters which control the hydrothermal processes in the geothermal reservoir modeling. In this study, as an initial challenge, we focus on permeability, which is one of the most important parameters for the modeling. We propose a machine-learning-based method to estimate permeability distributions using measurable data. A large number of learning data were prepared by a geothermal reservoir simulator capable of calculating pressure and temperature distributions in the natural state with different permeability distributions. Several machine learning algorithms (i.e., linear regression, ridge regression, Lasso regression, support vector regression (SVR), multilayer perceptron (MLP), random forest, gradient boosting, and the k-nearest neighbor algorithm) were applied to learn the relationship between the permeability and the pressure and temperature distributions. By comparing the feature importance and the scores of estimations, random forest using pressure differences as feature variables provided the best estimation (the training score of 0.979 and the test score of 0.789). Since it was learned independently of the grids and locations, this model is expected to be generalized. It was also found that estimation is possible to some extent, even for different heat source conditions. This study is a successful demonstration of the first step in achieving the goal of new data-driven geothermal reservoir engineering, which will be developed and enhanced with the knowledge of information science. Full article
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Article
Revised Rainfall Threshold in the Indonesian Landslide Early Warning System
Geosciences 2022, 12(3), 129; https://doi.org/10.3390/geosciences12030129 - 11 Mar 2022
Viewed by 997
Abstract
Landslides are one of the most disastrous natural hazards that frequently occur in Indonesia. In 2017, Balai Sabo developed an Indonesia Landslide Early Warning System (ILEWS) by utilizing a single rainfall threshold for an entire nation, leading to inaccuracy in landslide predictions. The [...] Read more.
Landslides are one of the most disastrous natural hazards that frequently occur in Indonesia. In 2017, Balai Sabo developed an Indonesia Landslide Early Warning System (ILEWS) by utilizing a single rainfall threshold for an entire nation, leading to inaccuracy in landslide predictions. The study aimed to improve the accuracy of the system by updating the rainfall threshold. We analyzed 420 landslide events in Java with the 1-day and 3-day effective antecedent rainfall for each landslide event. Rainfall data were obtained from the Global Precipitation Measurement (GPM), which is also used in the ILEWS. We propose four methods to derive the thresholds: the first is the existing threshold applied in the Balai Sabo ILEWS, the second and third use the average and minimum values of rainfall that trigger landslides, respectively, and the fourth uses the minimum value of rainfall that induces major landslides. We used receiver operating characteristic (ROC) analysis to evaluate the predictability of the rainfall thresholds. The fourth method showed the best results compared with the others, and this method provided a good prediction of landslide events with a low error value. The chosen threshold was then applied in the Balai Sabo-ILEWS. Full article
(This article belongs to the Collection Early Career Scientists’ (ECS) Contributions to Geosciences)
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Article
Transtension at the Northern Termination of the Alfeo-Etna Fault System (Western Ionian Sea, Italy): Seismotectonic Implications and Relation with Mt. Etna Volcanism
Geosciences 2022, 12(3), 128; https://doi.org/10.3390/geosciences12030128 - 10 Mar 2022
Cited by 1 | Viewed by 1106
Abstract
Offshore data in the western Ionian Sea indicate that the NW–SE-trending dextral shear zone of the Alfeo-Etna Fault System turns to the N–S direction near the Ionian coastline, where the extensional Timpe Fault System is located. Morpho-structural data show that NW–SE-trending right-lateral strike-slip [...] Read more.
Offshore data in the western Ionian Sea indicate that the NW–SE-trending dextral shear zone of the Alfeo-Etna Fault System turns to the N–S direction near the Ionian coastline, where the extensional Timpe Fault System is located. Morpho-structural data show that NW–SE-trending right-lateral strike-slip faults connect the Timpe Fault System with the upper slope of the volcano, where the eruptive activity mainly occurs along the N–S to NE–SW-trending fissures. Fault systems are related to the ~E–W-trending extension and they are seismically active having given rise to shallow and low-moderate magnitude earthquakes in the last 150 years. As a whole, morpho-structural, geodetic and seismological data, seismic profiles and bathymetric maps suggest that similar geometric and kinematic features characterize the shear zone both on the eastern flank of the volcano and in the Ionian offshore. The Alfeo-Etna Fault System probably represents a major kinematic boundary in the western Ionian Sea associated with the Africa–Europe plate convergence since it accommodates, by right-lateral kinematics, the differential motion of adjacent western Ionian compartments. Along this major tectonic alignment, crustal structures such as releasing bends, pull-apart basins and extensional horsetails occur both offshore and on-land, where they probably represent the pathway for magma uprising from depth. Full article
(This article belongs to the Special Issue Geodynamics and Seismotectonics in the Mediterranean Region)
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Article
Preservation of the Geoheritage and Mining Heritage of Serifos Island, Greece: Geotourism Perspectives in a Potential New Global Unesco Geopark
Geosciences 2022, 12(3), 127; https://doi.org/10.3390/geosciences12030127 - 10 Mar 2022
Cited by 1 | Viewed by 825
Abstract
Serifos island is characterized by rich geodiversity, industrial and cultural heritage. The present paper focuses on the geological and mining heritage of Serifos, with the aim of integrating the island in the international environment of Geoparks, in the near future. In this geopark, [...] Read more.
Serifos island is characterized by rich geodiversity, industrial and cultural heritage. The present paper focuses on the geological and mining heritage of Serifos, with the aim of integrating the island in the international environment of Geoparks, in the near future. In this geopark, Serifos can highlight the rich geological heritage of the island combined with the rich industrial heritage as expressed by mining activities since prehistoric times and the mining facilities of iron and copper mines. During the present study, six geotrails have been developed to link these cultural and ecological sites with the geological heritage. Along the routes, the geodiversity is explained, including its relationship with the surrounding biodiversity, and the historical and cultural aspects of the region. In the proposed geocultural routes (geotrails), the dialectic relationship between Humans and Nature is determined by historical conditions and by the record of the process that transforms space into a landscape. The geological-mining heritage of Serifos will attract people from all over the world with different kind of interests and will make it known to alternative tourists. The results of this paper are intended to constitute a valuable tool for enhancing and raising awareness of the geological heritage of the island of Serifos. Full article
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Article
Formation of Gold Alloys during Crustal Differentiation of Convergent Zone Magmas: Constraints from an AU-Rich Websterite in the Stanovoy Suture Zone (Russian Far East)
Geosciences 2022, 12(3), 126; https://doi.org/10.3390/geosciences12030126 - 08 Mar 2022
Viewed by 710
Abstract
Gold is typically transported by mafic and evolved magmas into the upper crust to be deposited in shallow oxidized porphyry and epithermal environments. However, the magmatic behavior of gold is still poorly understood and warrants further attention. Additional insights into the magmatic evolution [...] Read more.
Gold is typically transported by mafic and evolved magmas into the upper crust to be deposited in shallow oxidized porphyry and epithermal environments. However, the magmatic behavior of gold is still poorly understood and warrants further attention. Additional insights into the magmatic evolution of gold and other noble metals can be provided by investigations of primitive convergent zone magmas and products of their differentiation that contain primary-textured Au-alloys. One of the best examples of such Au-rich ultramafic cumulates is the Triassic (232–233 Ma) Ildeus intrusion, which was emplaced within the Mesozoic Stanovoy subduction zone in the Russian Far East. Some websterites from the Ildeus intrusion, representing cumulates crystallized from a primitive convergent zone magma, are enriched in Au (up to 596 ppm) and contain abundant Cu-Ag-Au micro-particles. Most of these Au-alloy micro-particles display compositions similar to those previously found in explosive pyroclastic rocks in the Lesser Khingan iron district, mantle wedge peridotites in Kamchatka and Cretaceous adakites in the Stanovoy suture zone. Textural and compositional characteristics suggest that Cu-Ag-Au alloys precipitated from a primitive calc-alkaline melt during its crustal differentiation in a Mesozoic paleo-subduction zone. Some large Cu-Ag-Au grains display an internal honeycomb-like structure with alternating Cu-rich and Cu-poor zones. Heating experiments under atmospheric conditions recorded a substantial loss of Cu from primary magmatic Cu-Ag-Au alloys, which appears to be a process characteristic of oxidized hydrothermal ore systems. We suggest that the later-stage hydrothermal alteration of differentiated igneous conduits containing magmatic gold alloys results in the formation of Cu-free gold mineralization comparable to the upper crustal porphyry and epithermal environments. Full article
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Article
Palaeo-Shoreline Configuration of the Adventure Plateau (Sicilian Channel) at the Last Glacial Maximum
Geosciences 2022, 12(3), 125; https://doi.org/10.3390/geosciences12030125 - 08 Mar 2022
Viewed by 746
Abstract
The Adventure Plateau, located in the NW sector of the Sicilian Channel, experienced several episodes of exposure/erosion and subsequent drowning, with the most recent occurring after the Last Glacial Maximum (LGM). Unlike other parts of the Sicilian Channel, the Adventure Plateau is relatively [...] Read more.
The Adventure Plateau, located in the NW sector of the Sicilian Channel, experienced several episodes of exposure/erosion and subsequent drowning, with the most recent occurring after the Last Glacial Maximum (LGM). Unlike other parts of the Sicilian Channel, the Adventure Plateau is relatively tectonically stable and is therefore best suitable for reconstructing its coastal configuration before the post-LGM marine transgression. Here, we use high-resolution seismic data to identify and map the palaeo-coastline at the LGM on the basis of the internal architecture of the prograding wedges (i.e., the location of the subaqueous clinoform rollover point) and the erosional markers such as the subaerial unconformities and the wave ravinement surfaces. These data, which show an extreme variability in the palaeo-morphology of the coastal margins of the Adventure Plateau, have been complemented with vintage seismic profiles in order to entirely cover its perimeter. The mapped LGM coastline has then been compared to predictions from glacial isostatic adjustment (GIA) modeling, which considers the horizontal migration of the shorelines in response to sea level rise and to Earth’s rotational and deformational effects associated with deglaciation. The two shorelines (i.e., the coastline derived from the marine data interpretation and the one derived from the GIA model) are in good agreement at 21 kyears BP, although some discrepancies occur in the southern part of the plateau, where the seabed slope is extremely gentle, which makes the clinoform rollover points and the buried erosional unconformities difficult to detect. After 20 kyears BP, an acceleration in the rate of the sea level rise occurred. The results of this study indicate the importance of comparing experimental data with model predictions in order to refine and calibrate boundary parameters and to gain a better picture of the evolution of sea level rise over various time scales. Full article
(This article belongs to the Section Climate)
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Article
Commentary and Review of Modern Environmental Problems Linked to Historic Flow Capacity in Arid Groundwater Basins
Geosciences 2022, 12(3), 124; https://doi.org/10.3390/geosciences12030124 - 07 Mar 2022
Viewed by 868
Abstract
Environmental problems may develop in groundwater basins when water levels change due to long-term wetter or drier climate or land development. A term related to water-level elevation is flow capacity, which develops in aquifers when the water table is at or very close [...] Read more.
Environmental problems may develop in groundwater basins when water levels change due to long-term wetter or drier climate or land development. A term related to water-level elevation is flow capacity, which develops in aquifers when the water table is at or very close to land surface. Non-capacity develops in systems where the water table is too deep for capillary water to reach the land surface. Flow capacity is the maximum amount of water that an aquifer can transmit. Sufficient moisture is not available for flow capacity to be established in most aquifers in arid zones and these aquifers are at non-capacity, but many aquifers in today’s deserts were at flow capacity when paleoclimates were cooler and moister during the late Pleistocene. Climate change and anthropogenic activities can cause aquifers to move toward flow capacity but in the last 15,000 years, almost always toward non-capacity. This paper reviews environmental and geotechnical problems associated with the transition of groundwater basins from flow capacity to non-capacity, and vice versa. Five relevant topics are discussed and evaluated: (1) The effects of flow capacity and non-capacity on groundwater basins targeted for waste repositories; (2) The salt contamination of groundwater where flow capacity was present in the Late Pleistocene and is no longer present; (3) Trace element enrichment in salt crusts in playa sediments and environmental risks to groundwater when the flow systems transition from flow capacity to non-capacity; (4) The development and retention of environmental tracers in arid groundwater flow systems at flow capacity that cannot be explained under conditions of non-capacity; and (5) The relationship of flow capacity to fossil hydraulic gradients and non-equilibrium conditions where there is little groundwater extraction. A case example is provided with each of these topics to demonstrate relevance and to provide an understanding of topics as they relate to land management. Full article
(This article belongs to the Special Issue Groundwater in Arid and Semiarid Areas II)
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Article
Numerical Assessment of the Loading Factors Affecting Liquefaction-Induced Failure
Geosciences 2022, 12(3), 123; https://doi.org/10.3390/geosciences12030123 - 07 Mar 2022
Viewed by 803
Abstract
This paper presents parametric studies that assess the role of loading factors (i.e., number of cycles, frequency, and amplitude) on liquefaction-induced failure by performing numerical simulations. Most of the existing literature considers the effects of the soil properties on the development of excess [...] Read more.
This paper presents parametric studies that assess the role of loading factors (i.e., number of cycles, frequency, and amplitude) on liquefaction-induced failure by performing numerical simulations. Most of the existing literature considers the effects of the soil properties on the development of excess pore pressure with few research endeavours focusing on the effects of the input motion itself. Numerical simulations are performed herein, via the advanced software platform OpenSees, to generate several finite element models that consider non-linear development of pore pressure inside the soil. Several sinusoidal inputs were considered to study the effects of the various loading factors and compare the responses. The main findings arise from evaluating the effects of several input motion parameters (number of cycles, frequency, and amplitude) on soil liquefaction through numerical simulations. This research study, based on state-of-the-art knowledge, may be applied to assess future seismic events and to update or propose new code provisions for soil liquefaction. Full article
(This article belongs to the Special Issue Assessment of Earthquake-Induced Soil Liquefaction Hazard)
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Article
Damage to Churches after the 2016 Central Italy Seismic Sequence
Geosciences 2022, 12(3), 122; https://doi.org/10.3390/geosciences12030122 - 04 Mar 2022
Viewed by 791
Abstract
The present study focuses on seismic damage to 36 masonry churches observed after the 2016 Central Italy earthquake. In the sample, recurrent architectural and structural features were identified and accurately described. In order to classify the churches in the sample based on their [...] Read more.
The present study focuses on seismic damage to 36 masonry churches observed after the 2016 Central Italy earthquake. In the sample, recurrent architectural and structural features were identified and accurately described. In order to classify the churches in the sample based on their safety level, their seismic vulnerability was assessed by adopting the simplified procedure proposed in the current Italian standards for cultural heritage. The observed damage, directly detected by the authors during the post-earthquake surveys, is presented and carefully described, highlighting the evolution of the damage. An analysis of the damage suffered by the inspected churches highlighted the most frequent causal mechanisms and the most vulnerable macroelements. Particular attention was devoted to computation of a damage index based on the observed damage as well as on the macroelements present in the surveyed churches. Moreover, a judgment of usability, i.e., whether a church could be occupied after a seismic event, was made using the official survey form and related to both the seismic intensity experienced and the observed damage index. An analysis of the collected data enabled consideration of the usability judgment with respect to the damage index values, computed according to the Italian standards. Full article
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Article
Electrical Properties and Anisotropy of Schists and Fault Rocks from New Zealand’s Southern Alps under Confining Pressure
Geosciences 2022, 12(3), 121; https://doi.org/10.3390/geosciences12030121 - 04 Mar 2022
Viewed by 919
Abstract
Magnetotelluric models spanning the Pacific–Australian Plate boundary in New Zealand’s South Island indicate a localized zone of low electrical resistivity that is spatially coincident with the ductile mid-crustal part of the Alpine Fault Zone (AFZ). We explored the source of this anomaly by [...] Read more.
Magnetotelluric models spanning the Pacific–Australian Plate boundary in New Zealand’s South Island indicate a localized zone of low electrical resistivity that is spatially coincident with the ductile mid-crustal part of the Alpine Fault Zone (AFZ). We explored the source of this anomaly by measuring the electrical properties of samples collected from surface outcrops approaching the AFZ that have accommodated a gradient of systematic strain and deformation conditions. We investigated the effects of tectonite fabric, fluid saturated pore/fracture networks and surface conductivity on the bulk electrical response and the anisotropy of resistivity measured under increasing confining pressures up to 200 MPa. We find that porosity and resistivity increase while porosity and the change in anisotropy of resistivity with confining pressure (δ (ρ)/δ (peff)) decreases approaching the AFZ, indicating the electrical response is controlled by pore fluid conductivity and modified during progressive metamorphism. Conversely, Alpine mylonites exhibit relatively low resistivities at low porosities, and lower δ (ρ)/δ (peff) than the schists. These findings indicate a transition in both the porosity distribution and electrical charge transport processes in rocks that have experienced progressive grain size reduction and mixing of phases during development of mylonitic fabrics due to creep shear strain within the AFZ. Full article
(This article belongs to the Special Issue Microstructural Analyses of Fault Rocks)
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Review
Nearshore Pelagic Influence at the SW Margin of the Paratethys Sea—Examples from the Miocene of Croatia
Geosciences 2022, 12(3), 120; https://doi.org/10.3390/geosciences12030120 - 04 Mar 2022
Viewed by 947
Abstract
(1) The ancient Paratethys Sea was a spacious inland salt-water basin, extending from the Alps, over Central Europe, to Central Asia. The southwestern part of its central area, the Croatian part of the Pannonian Basin System (CPBS), is generally known for shallow-water deposition [...] Read more.
(1) The ancient Paratethys Sea was a spacious inland salt-water basin, extending from the Alps, over Central Europe, to Central Asia. The southwestern part of its central area, the Croatian part of the Pannonian Basin System (CPBS), is generally known for shallow-water deposition and biota. The main purpose of this paper is to emphasize the significance of its less widespread deeper-water deposits in environmental and applied geology. (2) The authors consulted the previously published data, combined with their own results, obtained from the paleontological and sedimentological research, seismic stratigraphy and well-log analyses. (3) During our research in the CPBS, we noticed the connection between the tectonic structures and deep marine canyons and depressions within the Paratethyan shallows. Such structures can be recognized on well-logs and seismic or surface outcrops. They are situated along the faults, and deposits are characterized by the domination of pelagic over the benthic biota, sometimes with visible selective dissolution of aragonite/calcite tests. (4) Studied sedimentary sequences from these structures proved to be a precious source of data on the transgressive-regressive cycles, ancient migrations, modes of deposition and hydrocarbon formation during the Miocene Epoch in the CPBS. Full article
(This article belongs to the Section Sedimentology, Stratigraphy and Palaeontology)
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Article
87Sr/86Sr Ratios and Atmospheric Noble Gases in Theistareykir Geothermal Fluids: A Record of Glacial Water
Geosciences 2022, 12(3), 119; https://doi.org/10.3390/geosciences12030119 - 04 Mar 2022
Viewed by 799
Abstract
The determination of the current and past recharge sources, as well as the reconstruction of the timing of the recharge in geothermal reservoirs, is required in order to correctly assess the resource potential of these systems. Theistareykir is a newly developed geothermal field [...] Read more.
The determination of the current and past recharge sources, as well as the reconstruction of the timing of the recharge in geothermal reservoirs, is required in order to correctly assess the resource potential of these systems. Theistareykir is a newly developed geothermal field close to the well-known exploited fields of Krafla and Námafjall in NE Iceland. In this study, the 87Sr/86Sr ratios measured in deep geothermal fluids are presented and, together with the Cl and noble gas signatures, are used to place constraints on the fluid sources. The Cl/Sr and 87Sr/86Sr ratios show a peculiar and unique composition among Icelandic geothermal fluids. The 87Sr/86Sr ratios range from 0.70355 to 0.70671, suggesting the presence of a significant seawater component—possibly marine aerosols added to rain or snowfall—as well as an additional source of Sr leached from local basalts. Moreover, a correlation between the atmospheric noble gas (ANGs) elemental ratios Ne/Ar, Kr/Ar and Xe/Ar, and the 87Sr/86Sr ratios is observed. The latter results from the mixing of meteoric water with Sr leached from local basalts, meteoric water containing unrelated Sr from seawater, and recharge water with ANGs derived from trapped air bubbles in snow. We suggest that the combined ANGs and Sr seawater signatures are representative of a glacial water source derived from the melting of compacting snow. Full article
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Article
Petrogenesis of Lava from Christmas Island, Northeast Indian Ocean: Implications for the Nature of Recycled Components in Non-Plume Intraplate Settings
Geosciences 2022, 12(3), 118; https://doi.org/10.3390/geosciences12030118 - 03 Mar 2022
Viewed by 840
Abstract
Lava samples from the Christmas Island Seamount Province (CHRISP) record an extreme range in enriched mantle (EM) type Sr-Nd-Pb-Hf isotope signatures. Here we report osmium isotope data obtained on four samples from the youngest, Pliocene petit-spot phase (Upper Volcanic Series, UVS; ~4.4 Ma), [...] Read more.
Lava samples from the Christmas Island Seamount Province (CHRISP) record an extreme range in enriched mantle (EM) type Sr-Nd-Pb-Hf isotope signatures. Here we report osmium isotope data obtained on four samples from the youngest, Pliocene petit-spot phase (Upper Volcanic Series, UVS; ~4.4 Ma), and four samples from the earlier, Eocene (Lower Volcanic Series, LVS; ~40 Ma) shield building phase of Christmas Island. Osmium concentrations are low (5–82 ppt) with initial Os isotopic values (187Os/188Osi) ranging from (0.1230–0.1679). Along with additional new geochemical data (major and trace elements, Sr-Nd-Pb isotopes, olivine δ18O values), we demonstrate the following: (1) The UVS is consistent with melting of shallow Indian mid-ocean ridge basalt (MORB) mantle enriched with both lower continental crust (LCC) and subcontinental lithospheric mantle (SCLM) components; and (2) The LVS is consistent with recycling of SCLM components related to Gondwana break-up. The SCLM component has FOZO or HIMU like characteristics. One of the LVS samples has less radiogenic Os (γOs –3.4) and provides evidence for the presence of ancient SCLM in the source. The geochemistry of the Christmas Island lava series supports the idea that continental breakup causes shallow recycling of lithospheric and lower crustal components into the ambient MORB mantle. Full article
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Article
Down under and under Cover—The Tectonic and Thermal History of the Cooper and Central Eromanga Basins (Central Eastern Australia)
Geosciences 2022, 12(3), 117; https://doi.org/10.3390/geosciences12030117 - 02 Mar 2022
Viewed by 1151
Abstract
The Cooper subregion within the central Eromanga Basin is the Swiss army knife among Australia’s sedimentary basins. In addition to important oil and gas resources, it hosts abundant coal bed methane, important groundwater resources, features suitable conditions for enhanced geothermal systems, and is [...] Read more.
The Cooper subregion within the central Eromanga Basin is the Swiss army knife among Australia’s sedimentary basins. In addition to important oil and gas resources, it hosts abundant coal bed methane, important groundwater resources, features suitable conditions for enhanced geothermal systems, and is a potential site for carbon capture and storage. However, after seven decades of exploration, various uncertainties remain concerning its tectonic and thermal evolution. In this study, the public-domain 3D model of the Cooper and Eromanga stacked sedimentary basins was modified by integrating the latest structural and stratigraphic data, then used to perform numerical basin modelling and subsidence history analysis for a better comprehension of their complex geologic history. Calibrated 1D/3D numerical models provide the grounds for heat flow, temperature, thermal maturity, and sediment thickness maps. According to calibrated vitrinite reflectance profiles, a major hydrothermal/magmatic event at about 100 Ma with associated basal heat flow up to 150 mW/m2 caused source rock maturation and petroleum generation and probably overprinted most of the previous hydrothermal events in the study area. This event correlates with sedimentation rates up to 200 m/Ma and was apparently accompanied by extensive crustal shear. Structural style and depocentre migration analysis suggest that the Carboniferous–Triassic Cooper Basin initially has been a lazy-s shaped triplex pull-apart basin controlled by the Cooper Basin Master Fault before being inverted into a piggy-back basin and then blanketed by the Jurassic–Cretaceous Eromanga Basin. The interpreted Central Eromanga Shear Zone governed the tectonic evolution from the Triassic until today. It repeatedly induced NNW-SSE directed deformation along the western edge of the Thomson Orogen and is characterized by present-day seismicity and distinct neotectonic features. We hypothesize that throughout the basin evolution, alternating tectonic stress caused frequent thermal weakening of the crust and facilitated the establishment of the Cooper Hot Spot, which recently increased again its activity below the Nappamerri Trough. Full article
(This article belongs to the Special Issue Temperature in Sedimentary Basins II)
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Communication
Evaluation of InfraRed Thermography Supported by UAV and Field Surveys for Rock Mass Characterization in Complex Settings
Geosciences 2022, 12(3), 116; https://doi.org/10.3390/geosciences12030116 - 02 Mar 2022
Cited by 1 | Viewed by 772
Abstract
The InfraRed Thermography (IRT) technique is gaining increasing popularity in the geosciences. Although several studies on the use of this technique for rock mass characterization were reported in the literature, its applicability is challenging in complex environments, characterized by poor accessibility, lithological heterogeneity, [...] Read more.
The InfraRed Thermography (IRT) technique is gaining increasing popularity in the geosciences. Although several studies on the use of this technique for rock mass characterization were reported in the literature, its applicability is challenging in complex environments, characterized by poor accessibility, lithological heterogeneity, karst features and disturbances, such as vegetation and human activities. This paper reports the results of specific tests carried out to explore the application of IRT methods, supported by UAV surveys, for rock mass characterization in complex conditions. In detail, a 24-h monitoring was performed on an appropriate case study to assess which type of information can be collected and what issues can be expected. The results of the thermograms were compared with data reported in the literature and discussed. A novel method to detect correlations between the temperature profiles at the air-rock interfaces and the rock mass properties is presented. The main advantages, limitations and suggestions in order to take full advantage of the IRT technique in complex conditions are reported in the final section. Full article
(This article belongs to the Section Geomechanics)
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Article
Simulating Thermal Interaction of Gas Production Wells with Relict Gas Hydrate-Bearing Permafrost
Geosciences 2022, 12(3), 115; https://doi.org/10.3390/geosciences12030115 - 02 Mar 2022
Cited by 1 | Viewed by 2081
Abstract
The thermal interaction of a gas production well with ice-rich permafrost that bears relict gas hydrates is simulated in Ansys Fluent using the enthalpy formulation of the Stefan problem. The model admits phase changes of pore ice and hydrate (ice melting and gas [...] Read more.
The thermal interaction of a gas production well with ice-rich permafrost that bears relict gas hydrates is simulated in Ansys Fluent using the enthalpy formulation of the Stefan problem. The model admits phase changes of pore ice and hydrate (ice melting and gas hydrate dissociation) upon permafrost thawing. The solution is derived from the energy conservation within the modeling domain by solving a quasilinear thermal conductivity equation. The calculations are determined for a well completion with three casing strings and the heat insulation of a gas lifting pipe down to a depth of 55 m. The thermal parameters of permafrost are selected according to laboratory and field measurements from the Bovanenkovo gas-condensate field in the Yamal Peninsula. The modeling results refer to the Bovanenkovo field area and include the size of the thawing zone around wells, with regard to free methane release as a result of gas hydrate dissociation in degrading permafrost. The radius of thawing around a gas well with noninsulated lifting pipes operating for 30 years may reach 10 m or more, while in the case of insulated lifting pipes, no thawing is expected. As predicted by the modeling for the Bovanenkovo field, methane emission upon the dissociation of gas hydrates caused by permafrost thawing around producing gas wells may reach 400,000–500,000 m3 over 30 years. Full article
(This article belongs to the Special Issue Permafrost and Gas Hydrate Response to Ground Temperature Rising)
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Article
Zircon from Altered Monzonite Rocks Provides Insights into Magmatic and Mineralizing Processes at the Douay Au Project, Abitibi Greenstone Belt
Geosciences 2022, 12(3), 114; https://doi.org/10.3390/geosciences12030114 - 02 Mar 2022
Viewed by 821
Abstract
Zircon provides essential information on the age and oxidation state of magmatic systems and can be used to characterize magmatic-hydrothermal Au mineralizing systems. Using the Douay intrusion-related gold system (IRGS) as a type example of Neoarchean syenite-associated mineralization (Abitibi greenstone belt), we demonstrate [...] Read more.
Zircon provides essential information on the age and oxidation state of magmatic systems and can be used to characterize magmatic-hydrothermal Au mineralizing systems. Using the Douay intrusion-related gold system (IRGS) as a type example of Neoarchean syenite-associated mineralization (Abitibi greenstone belt), we demonstrate that zircon from altered quartz-monzonite rocks can also be used to infer the age of a magmatic-hydrothermal event. Here, zircon chemistry is used to identify the following sequence of events at the Douay exploration project: (1) the crystallization of zircon at ~2690 Ma in evolved residual melts with distinct U-contents (quartz-monzonite magma); (2) the extensive radiation damage for the U-rich grains over a period of ~10–15 My; and (3) the alteration of zircon grains at ~2676 Ma by interaction with magmatic-hydrothermal mineralizing fluids derived from syenite and carbonatite intrusive phases. This study also distinguishes extensively altered zircon grains from pristine to least-altered zircon formed in distinct magmatic environments using a Th/U vs. U discrimination diagram. Full article
(This article belongs to the Section Geochemistry)
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Article
An Early-Warning System to Validate the Soil Profile during TBM Tunnelling
Geosciences 2022, 12(3), 113; https://doi.org/10.3390/geosciences12030113 - 02 Mar 2022
Cited by 1 | Viewed by 946
Abstract
Identification of soil condition at the working face of a tunnel boring machine (TBM) is a key factor for the efficiency and safety of TBM tunneling. The paper presents the first application of the Horizontal-to-Vertical Spectral Ratio (HVSR) method on microtremors induced by [...] Read more.
Identification of soil condition at the working face of a tunnel boring machine (TBM) is a key factor for the efficiency and safety of TBM tunneling. The paper presents the first application of the Horizontal-to-Vertical Spectral Ratio (HVSR) method on microtremors induced by a TBM during tunnelling. The innovative application is based on the development of an easy-to-use and economical early-warning system, which aims to confirm, or otherwise, the soil profile established in the design phase of tunnels by comparing the soil natural frequencies obtained from the soil profile carried out during the design phase and the soil natural frequencies coming from the HVSR analysis of the microtremors induced by the TBM during tunnelling. Just one or two geophones are necessary to use the proposed procedure. It can be applied to an area up to about 20 m ahead of the TBM excavation front and constitutes a powerful early warning system. Due to the great heterogeneity of the subsoil, dual-mode TBMs are often used, frequently changing from Open-Face (OF) mode for rock formations to Earth Pressure Balance (EPB) mode for cohesive and incoherent soil. Any “additional” information on the soil, which will be dug in the next days or hours is extremely useful for subsoil with great heterogeneity. The new procedure offers a reasonable time interval in which to modify the excavation method. This, in turn, can avoid damage to the TBM and existing structures and infrastructures. It allows us also to have a valuable geotechnical database for future works on the infrastructural networks. The proposed procedure has been successfully applied during the construction of the new underground lines in Catania (Italy). Full article
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Article
SEM3D: A 3D High-Fidelity Numerical Earthquake Simulator for Broadband (0–10 Hz) Seismic Response Prediction at a Regional Scale
Geosciences 2022, 12(3), 112; https://doi.org/10.3390/geosciences12030112 - 02 Mar 2022
Viewed by 1167
Abstract
In this paper, we present SEM3D: a 3D high-fidelity numerical earthquake simulator that is tailored to predict the seismic wave field of complex earthquake scenarios from the fault to the epicenter site. SEM3D solves the wave-propagation problem by means of the spectral element [...] Read more.
In this paper, we present SEM3D: a 3D high-fidelity numerical earthquake simulator that is tailored to predict the seismic wave field of complex earthquake scenarios from the fault to the epicenter site. SEM3D solves the wave-propagation problem by means of the spectral element method (SEM). The presented demonstrative test case was a blind MW6.0 earthquake scenario at the European experimental site located in the sedimentary basin of Argostoli on the island of Kefalonia (Western Greece). A well-constrained geological model, obtained via geophysical inversion studies, and seismological model, given the large database of seismic traces recorded by the newly installed ARGONET network, of the site were considered. The domain of interest covered a region of 44 km × 44 km × 63 km, with the smallest grid size of 130 m × 130 m × 35 m. This allowed us to simulate the ground shaking in its entirety, from the seismic source to the epicenter site within a 0–10 Hz frequency band. Owing to the pseudo-spectral nature of the numerical method and given the high polynomial order (i.e., degree nine), the model featured 1.35·1010 DOFs (degrees of freedom). The variability of the synthetic wave field generated within the basin is assessed herein, exploring different random realizations of the mean velocity structure and heterogeneous rupture path. Full article
(This article belongs to the Special Issue Engineering Analysis of Near-Source Strong Ground Motion)
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