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Geosciences, Volume 14, Issue 7 (July 2024) – 6 articles

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26 pages, 35034 KiB

Open AccessArticle

Strain Analysis and Kinematics of Deformation of the Tectonic Nappe Pile in Olympos-Ossa Mountainous Area: Implication for the Exhumation History of the HP/LT Ampelakia Unit and the Olympos-Ossa Tectonic Window (Eastern Thessaly, Central Greece)

by Ioannis Vrontzos, Emmanouil Katrivanos, Ilias Lazos, Lambrini Papadopoulou and Adamantios Kilias

Geosciences 2024, 14(7), 179; https://doi.org/10.3390/geosciences14070179 - 28 Jun 2024

Viewed by 150

Abstract

This paper focuses on the structural and finite strain analysis of the Pelagonian nappe, the HP/LT Ampelakia unit, and the Olympos-Ossa unit in the Olympos-Ossa mountainous area in order to better understand the exhumation history of the Ampelakia unit and the underlain Olympos-Ossa unit. Two main stages of Tertiary deformation were revealed, related to nappe stacking and exhumation processes. During the Paleocene–Eocene crustal subduction, HP/LT metamorphism, compression, and nappe stacking were developed progressively. This D₁ stage was terminated with the final SW-ward emplacement of the Ampelakia and Pelagonian nappe on the Olympos-Ossa unit during the Eocene–Early Oligocene. The next stage of deformation, D₂, was developed during the Oligocene–Miocene following the orogenic nappes stacking. D₂ was considered an extensional event, related to metamorphic isothermal decompression, nappes tectonic denudation, crustal uplift, and final exhumation of the Ampelakia unit and the Olympos-Ossa unit as a tectonic window. The calculated finite strain ellipsoids indicate a main flattening type strain geometry and middle strain intensity, increasing along the nappe contacts. The quartz C-axes diagrams also reveal a flattening type of deformation and non-coaxial flow towards the southwest and northeast at the western and eastern flanks of Olympos-Ossa Mountain, respectively. The calculated W_k vorticity number ranges from 0.23 to 0.93. Full article

(This article belongs to the Special Issue Metamorphism and Tectonic Evolution of Metamorphic Belts)

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19 pages, 5611 KiB

Open AccessArticle

Mapping of Supra-Glacial Debris Cover in the Greater Caucasus: A Semi-Automated Multi-Sensor Approach

by Levan G. Tielidze, George Iacob and Iulian Horia Holobâcă

Geosciences 2024, 14(7), 178; https://doi.org/10.3390/geosciences14070178 - 27 Jun 2024

Viewed by 257

Abstract

Supra-glacial debris cover is important for the control of surface ice melt and glacier retreat in mountain regions. Despite the progress in techniques based on various satellite imagery, the mapping of debris-covered glacier boundaries over large regions remains a challenging task. Previous studies of the debris-covered glaciers in the Greater Caucasus have only focused on limited areas. In this study, using the Sentinel 1–2 imagery (2020), DebCovG-carto toolbox, and existing glacier inventory (2020), we produced the first detailed assessment of supra-glacial debris cover for individual glaciers in the entire Greater Caucasus. Our study shows that in 2020, 10.3 ± 5.6% of the glacier surface in this mountain region was covered by debris. A comparison of sub-regions such as the Elbrus Massif and other individual glaciers from the central Greater Caucasus shows an increasing trend of supra-glacial debris cover from 2014 to 2020. The total area of supra-glacial debris cover expanded from ~4.6% to ~5.8% for Elbrus and from ~9.5% to ~13.9% for the glaciers of the central Greater Caucasus during the same period. Supra-glacial debris cover also expanded upward on these glaciers between 2014 and 2020. A recent increase in rock-ice avalanche activity in combination with increased air temperature and decreased precipitation in the Greater Caucasus may be responsible for this upward migration and expanded area of supra-glacial debris cover. This study provides valuable insights into the spatial distribution, temporal evolution, and factors influencing supra-glacial debris cover in the Greater Caucasus. The findings contribute to our understanding of glacier dynamics and highlight the importance of continuous monitoring and assessment of supra-glacial debris cover in the context of climate change and glacier retreat. We recommend using the DebCovG-carto toolbox for regional assessment of supra-glacial debris coverage in other mountain regions as well. Full article

(This article belongs to the Section Cryosphere)

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36 pages, 83707 KiB

Open AccessArticle

Modern River-Sand Geochemical Mapping in the Manufahi Municipality and Its Surroundings, Timor-Leste: Implications for Provenance

by Vital Vilanova, Tomoyuki Ohtani, Satoru Kojima, Kazuma Yatabe, Nene Cristovão and Aniceta Araujo

Geosciences 2024, 14(7), 177; https://doi.org/10.3390/geosciences14070177 - 25 Jun 2024

Viewed by 364

Abstract

A geochemical mapping of regional modern river-sand is performed to clarify geological information in the study area of Timor-Leste. Several areas of Timor-Leste including the study area in particular have limited geological information due to limited accessibility and dense vegetation coverage, and deformed, weathered, and erosion-covered materials. A total of 53 modern river sand samples were collected and analyzed. Ten major elements were determined by using wavelength-dispersive X-ray fluorescence. Areas characterized by clastic sedimentary rocks are recognized clearly by elevated concentrations of SiO

_{2}

, Al

_{2}

_{3}

, and K

_{2}

O. Meanwhile, areas covered by carbonate sedimentary rocks are detected by significant concentrations of CaO and MnO. The occurrences of the altered clastic and carbonate sedimentary rocks of the Wailuli and Aitutu Formations due to metamorphic, silicification and other alteration processes were responsible for the elevated concentrations and positive correlation between SiO

_{2}

, CaO, K

_{2}

O, and MnO, and CaO, TiO

_{2}

, and MnO in the midstream and near the downstream areas of the Clerec and Sahe River catchments. The positive correlation observed between TiO

_{2}

, CaO and MnO may be ascribed to the presence of carbonate components associated with secondary Ti-bearing minerals, which are potentially formed through hydrothermal alteration processes. Full article

(This article belongs to the Section Geochemistry)

11 pages, 978 KiB

Open AccessArticle

Determining the Cohesive Length of Rock Materials by Roughness Analysis

by Saeed Aligholi, Manoj Khandelwal and Ali Reza Torabi

Geosciences 2024, 14(7), 176; https://doi.org/10.3390/geosciences14070176 - 25 Jun 2024

Viewed by 384

Abstract

In this research, the cohesive length of various rock types is measured using quantitative fractography alongside a recently developed multifractal analysis. This length is then utilized to gauge material cohesive stress through the theory of critical distances. Furthermore, the fracture process zone length of different rings sourced from identical rocks is assessed as a function of ring dimensions and experimental measurements of fracture toughness, in accordance with the energy criterion of the finite fracture mechanics theory. Subsequently, employing the stress criterion within coupled finite fracture mechanics, the failure stress corresponding to the fracture process zone is determined for various rings. Ultimately, through interpolation, the critical stress corresponding to the cohesive length, quantified via quantitative fractography, is approximated. Remarkably, the cohesive stress values derived from both methodologies exhibit perfect alignment, indicating the successful determination of cohesive length for the analyzed rock materials. The study also delves into the significant implications of these findings, including the quantification of intrinsic tensile strength in quasi-brittle materials and the understanding of tensile strength variations under diverse stress concentrations and loading conditions. Full article

24 pages, 7884 KiB

Open AccessArticle

Sustainable Geotourism in the Chiusella Valley (NW Italian Alps): A Tool for Enhancing Alpine Geoheritage in the Context of Climate Change

by Arianna Negri, Elena Storta, Rasool Bux Khoso, Agnese Maria Colizzi, Fiorella Acquaotta, Mauro Palomba and Marco Giardino

Geosciences 2024, 14(7), 175; https://doi.org/10.3390/geosciences14070175 - 24 Jun 2024

Viewed by 208

Abstract

The Chiusella Valley (NW Italian Alps) is a key area for both the history of the alpine orogeny and its environmental context. It presents major structural features (including the Traversella neoalpine intrusion and a section of the Insubric line) and evidence of past climate changes in the region. Even if the Chiusella Valley was previously renowned for mining activities and most recently considered an alpine rural area with minor tourist attractions, its important geoheritage could offer alternatives to traditional mountain activities, which are facing adversity from increasing temperatures. This paper emphasises the role of geotourism in both enhancing sustainable development and raising awareness of climate change. For this purpose, the geodiversity of the Chiusella Valley has been analysed and several geosites have been identified. The research methodology includes field surveys, analysis of an existing educational activities and scientific literature, and assessment of geosites by quantitative analysis of five groups of indicators, including scientific, cultural, and educational values. The geosite selection within the Chiusella Valley reveals memories of past and present climate changes but also supports the development of targeted geotourism activities in the area. Additionally, a specific location has been identified for hosting indoor activities showcasing climate change action. These valuable contributions to sustainable geotourism provide opportunities for exploring the Alps in the vicinity of the Po Plain urban areas, while minimizing the environmental impact and facilitating educational activities on geodiversity and geoheritage. Full article

(This article belongs to the Special Issue Geoheritage as A Tool to Increase Awareness about Past and Present Climate Change)

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24 pages, 10672 KiB

Open AccessArticle

Mechanics of Rainfall-Induced Landslides after a Prolonged Dry Period Based on Laboratory Tests and Numerical Models Incorporating Soil-Water Characteristic Curves

by Kishan Bhadiyadra and Dominic E. L. Ong

Geosciences 2024, 14(7), 174; https://doi.org/10.3390/geosciences14070174 - 24 Jun 2024

Viewed by 275

Abstract

In India, particularly within its Northeastern territories, landslides triggered by rainfall following dry periods are a major concern, consistently causing extensive damage to both life and infrastructure. This study focuses on mitigating their impact through preemptive measures, with an emphasis on analyzing slope stability to determine critical intervention points. The investigation includes experimental tests on soil samples to assess key parameters, such as soil matric suction and unconfined compressive strength, alongside an analysis of slope failures during the 2017 monsoon in Mizoram’s Lunglei district. Employing Soil-Water Characteristic Curves (SWCC) derived from ASTM D5298-10 standards and a microwave drying technique for preparing soil samples, the research evaluates the condition of the slopes before and after monsoonal rains. This study utilizes a blend of numerical modeling and empirical laboratory investigations to explore the factors contributing to slope instability. The findings underscore the necessity of advanced landslide warning systems, suggesting that a deeper understanding of rainfall-induced slope failures could significantly enhance disaster preparedness and reduce potential damages. Full article

(This article belongs to the Section Geomechanics)

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