Rock Units Research Articles

The 3.53 Ga St James Volcanogenic Massive Sulfide Deposit, Kaapvaal Craton: Links to Submarine Rhyolites, Not to Komatiites

Abstract The Nondweni greenstone belt is located in the southeastern region of the Kaapvaal craton in South Africa and contains significant volumes of 3.53 to 3.45 Ga mafic-ultramafic lava flows (komatiitic and tholeiitic basalts). Minor felsic volcanic rock units, such as massive rhyolites and deformed quartz-feldspar-mica schists (felsic schists), also occur and are demonstrably linked to small base metal sulfide orebodies, interpreted here as volcanogenic massive sulfide (VMS)-type mineralization (e.g., sphalerite, chalcopyrite, pyrrhotite, pyrite, galena, acanthite). Chemical abrasion-isotope dilution-thermal ionization mass spectrometry (CA-ID-TIMS) U-Pb zircon analysis yields a rhyolite eruption age of 3531.91 ± 0.46 Ma for the felsic volcanic rock unit that hosts VMS-type mineralization at the St James deposit, which renders this Zn-Cu-Pb-Ag mineralization among the oldest preserved of its kind, offering insights into ore-forming processes that took place on and below the Paleoarchean sea floor. Rare earth element geochemical modeling suggests that the felsic volcanic rocks formed by moderate degrees of partial melting of hydrothermally altered basalts similar in composition to those from the Nondweni greenstone belt. Regarding ore formation, we envisage a scenario where basaltic ocean floor, in close proximity to a back-arc spreading ridge, had been intensively altered and subjected to elevated temperatures, which facilitated localized melting at low pressures (<2 kbar), resulting in the production of rhyolitic magmas accompanied by hydrothermal sulfide deposition. This model is supported by evidence from multiple sulfur isotope data (δ34S and Δ33S), which demonstrates that the basaltic rocks contain unfractionated magmatic sulfur and the rhyolitic rocks contain sulfur sourced from altered oceanic basalts. In contrast, the rhyolite-associated VMS-type mineralization records even more complex sulfur interactions, including contributions from surficial mass independent fractionated sulfur isotopic components; that is, these base metal sulfide ores exhibit a negative sulfur mass-independent fractionation signature of –0.53‰ Δ33S.

LITHOFACIES AND GEOCHEMICAL ANALYSIS OF THE LATE PALEOZOIC TOBRA FORMATION, SALT RANGE, PAKISTAN: IMPLICATIONS FOR THE PROVENANCE AND PALEOENVIRONMENT RECONSTRUCTION

The late Paleozoic Tobra Formation is an exclusive rock unit of the Salt Range which marks the end of a long period of nondeposition within the Gondwana domain of the Indian Plate. In this study, the lithofacies, petrographic, and geochemical properties of the Tobra Formation are presented to get a comprehensive understanding of the depositional environment, provenance, and paleoclimatic conditions. Three outcrop sections of Western to Eastern Salt Range were selected. Field studies show that the Tobra Formation is composed of six lithofacies that are broadly classified into three facies associations representing alluvial-plain depositional settings characterized by the following distinct depositional elements: (a) alluvial-fan debris-flow deposits, (b) alluvial-fan stream-flow deposits, and (c) overbank-flow deposits. These depositional elements formed as a result of local glaciation in paleogeographically close proximity with a general trend from southwest to northeast and affected the region up to the Eastern Salt Range. Furthermore, the petrographic and geochemical data indicate that lithologic units of the Tobra Formation show a submature to mature nature with characteristic lithic arenite and feldspathic litharenite to the sublitharenite petrofacies. Moreover, in the paleogeographic reconstruction of the Indian Plate during the late Paleozoic, the Tobra Formation was deposited during active tectonics with recycled orogenic phases influenced by glacial to glaciofluvial conditions. The sources of these sediments were igneous rocks, metasediments, and sandstones, more probably derived from the basement-related shield rocks. The majority of glaciofluvial signatures evidence that the Salt Range, Pakistan, occupied the paleogeographic position a little away from the maximum glacial extent during the late Permian as compared with the time-equivalent glacial units, such as the Al-Khalata Formation of Oman and the Talchir Boulder Beds of India.

Lithologic Relationship and Petrographic Features of Crystalline Rocks in Babanla Area, Egbe-Isanlu Schist Belt, Southwestern Nigeria

Crystalline rocks form a major part of the basement complex of Nigeria, and Babanla area in Egbe-Isanlu schist belt is not an exception. These rock units are investigated for lithological characteristics and petrographic features that may be related to geodynamic setting of the area. Systematic geological mapping reveals the area is underlain by banded gneiss, granite gneiss, quartzite (quartz schist), marble, talcose rock (talc schist), epidiorite, coarse-grained granite and pegmatite. Field investigation also reveals the gneissic units are low-lying and Babanla area sits on Precambrian pegmatite occurring as dykes, veins and discordant bodies within the host gneissic rocks. The structural framework of Babanla area is dominated by discontinuities including faults, joints and fractures with widespread deformations characterized by mesmerizing folds and veining. Petrographic analysis of the crystalline rocks indicates the units contain varying amounts of common rock-forming minerals which include quartz, orthoclase, plagioclase, muscovite, biotite, hornblende and subordinate opaque minerals. The percentage mineralogical composition as revealed in thin section based on visual estimation and point counting indicates the rocks are mineralogically similar to those in other areas of the basement complex. These lithologies, which are mainly metamorphic and igneous are common and have predictable mineralogy but are unique in their respective localities as contributing to the understanding of the geodynamic evolution of the basement complex of south western Nigeria.

U-Pb zircon geochronology and chronostratigraphy of the Eocene–Miocene John Day Formation of central and eastern Oregon

The John Day Formation of central and eastern Oregon, USA, contains a rich record of late Eocene to early Miocene faunal and floral evolution, climate and environmental change, and landscape evolution, and accordingly, it has been studied for over a century to better understand ancient terrestrial ecosystems of North America. Further progress in leveraging the John Day Formation rock archive to study these systems requires an updated chronostratigraphic framework with a foundation of modern high-precision radioisotope geochronology. We present a comprehensive dataset of U-Pb zircon dates measured by chemical abrasion−isotope dilution−thermal ionization mass spectrometry that yielded 23 new highly precise eruption and depositional ages for volcanic beds in the John Day Formation stratigraphy, in the environs of John Day Fossil Beds National Monument. The new ages significantly refine the overall timing of the John Day Formation and reveal new spatiotemporal correlations among strata of the Sheep Rock, Painted Hills, and Clarno Units. We integrated our dataset with composite stratigraphic information through Bayesian age modeling to establish probabilistic posterior age constraints for all formal and informal lithostratigraphic divisions of the eastern facies of the John Day Formation and durations of previously identified long-lived hiatuses. The results robustly link the John Day Formation stratigraphy to the geologic and paleomagnetic time scales and global proxy records, offering new opportunities for investigating terrestrial records of the Eocene−Miocene Earth system in the Pacific Northwest and testing diachroneity of faunal assemblages that define North American Land Mammal Ages.

Pletzachkogel (Austria): Landslides caused by “Hard on Soft” geomechanics

Abstract Pletzachkogel is a mountain North of the Tyrolean Inn valley in a prominent position above the village of Kramsach. Three major rock avalanches have occurred since the last glaciation and ongoing rockfall from the head scarp area presently affects local infrastructure. This study presents geological and geomechanical investigations of Pletzachkogel that were performed using conventional and uncrewed aerial vehicle (UAV) mapping techniques and focused on understanding the different landslide processes. The investigation indicates that the gravitational instability is related to a stratigraphic sequence of “Hard on Soft” rock units: Hauptdolomit and Plattenkalk beds (hard) – Kössen Formation (soft) – Oberrhätkalk and Lower Jurassic Breccia units (hard). “Hard on Soft” slope deformation has been described for similar stratigraphic conditions and involves the overlying hard rock mass breaking apart over a soft underlying unit. This leads to distinct geomorphological features like buttresses. In addition to the “Hard on Soft” stratigraphy, synsedimentary deformation during deposition, polyphase, heteroaxial, tectonic deformation during Alpine orogenesis, and glacial loading and unloading during the last ice age exacerbated landslide processes. This study describes the “Hard on Soft” geomechanics of Pletzachkogel and also demonstrates the value of UAV‐based structural mapping, particularly for acquiring and quantifying structural rock mass data in inaccessible areas.

Integrated Multiscale Pore Characterization of Carbonate Rocks in the Barra Velha Formation, Santos Basin, Brazil

Summary Carbonate rocks feature heterogeneous porous systems that span multiple scales, from pore level to the reservoir scale. The complexity and diversity of carbonate reservoirs demand a consistent approach to their characterization. The efficient integration of multiscale imaging data and petrophysical data is increasingly important to address the challenges associated with these complex carbonate reservoirs. A crucial step in overcoming these scale gaps in reservoir modeling and simulation involves enhancing the characterization of reservoir flow units and their associations with geological and petrophysical heterogeneities at varying scales. In this study, we focus on the classification of pore types using digital rock analysis and petrophysical evaluation of pre-salt lacustrine carbonates from the Barra Velha Formation (BVF) in the Santos Basin using computerized tomography (CT), core samples description, and petrography. Eight types of pores were identified at the core scale: interparticle, stratiform-vuggy, growth framework, vuggy, vuggy-fracture, fracture, interclast, and intraclast. The distribution and characteristics of these pore types were analyzed at different scales, including thin-sections and micro-CT, and nuclear magnetic resonance (NMR), which highlights the diversity in the porous system and the impact of different pore types on porosity and permeability. NMR analyses illustrated the pore size heterogeneity to provide distinction between tight and porous samples. Hydraulic rock units (HRUs) were defined based on flow zone indicator (FZI) using the probability plot approach. Seven HRUs were defined: HRU1 and HRU2 represent samples with the highest FZI and rock quality index (RQI) values, whereas HRU3 and HRU4 denote intermediate values. HRU5, HRU6, and HRU7 represent units with the lowest values. HRU1 and HRU2 were predominantly associated with vuggy, growth framework, and interparticle porosities, which are often enhanced by dissolution processes. Conversely, HRUs with reduced reservoir qualities (5, 6, and 7), characterized by the lowest permeability values, are more prevalent in intervals with higher silicification and silica and dolomite cementation, presenting a variety of pore types at a macroscale. The integration of multiscale imaging techniques and petrophysical data underscores the complexity of pore systems, providing crucial insights into their reservoir characteristics.

Geological and ground magnetic studies on the Ochre-Um Greifat hydrothermal deposits and their relationship to geological structures, Central Eastern Desert, Egypt

The current study offers an integrated approach for investigating the Ochre-Um Greifat hydrothermal deposits in the Central Eastern Desert of Egypt and its applicability to other regions with similar geology, conditions, and circumstances around the world. This work is characterized by combining detailed geological studies with ground magnetic data processing techniques to delineate hydrothermal zones associated with this specific deposit. This integrated approach presents a more robust and effective framework for deciphering potential mineralized zones, offering an outstanding advancement for exploration of Ochre-Um Greifat hydrothermal deposits and similar types. The outcropped rock units and structures in the study area were mapped through geological field investigations. The results revealed that the NNW-SSE normal fault and its branches, the WNW-ESE sinistral strike-slip fault, and its Riedel shears influence the area. The findings of chemical analyses indicate that Miocene clastic carbonate sedimentary rocks have anomalous lead (Pb) and copper (Cu) concentrations, as well as high iron (Fe) and zinc (Zn). These findings also include uranium (U), whose grades range from low to high. Ground magnetic data was applied to determine basement depth, geologic structures, and their relationship to mineralization deposits. The high magnetic anomalies in the study area could have contributed to the formation of ochre deposits. Ground magnetic data were inverted to 3-D models to construct a reliable geological model of the studied area. The resulting models highlighted the locations of significant high magnetic susceptibility zones (may be a magmatic source rich in iron) responsible for Ochre-Um Greifat hydrothermal deposits, as well as their lateral and vertical extensions. These zones are considered potential exploration areas.

Investigating the role of rock weathering and clay mineralogy in landslide occurrences within the exposed Tertiary Formations in Rangamati area

BackgroundLandslides are a major and recurring hazard in the folded Tertiary sedimentary rock units of Southeastern Bangladesh. The mechanical strength and stability of these rocks are strongly influenced by their mineralogical composition and geochemical alteration, which can affect their susceptibility to weathering and collapse. However, the role of these factors in triggering landslides remains poorly understood.ObjectiveThis research addresses this gap by linking rock weathering intensity and clay mineral composition to landslide mechanisms in the outcropped Tertiary Formations in the Rangamati region.MethodsDetailed geological field work has been conducted on four major exposed Tertiary Formations: Dupi Tila Formation, Tipam Sandstone Formation, Boka Bil Formation, and Bhuban Formation. A comprehensive analysis of 30 landslides is carried out to evaluate the geological influence, with 22 samples (both fresh and weathered) examined using X-ray Diffraction (XRD), X-ray Fluorescence (XRF), and Scanning Electron Microscope (SEM) techniques to determine clay content and the extent of weathering. Shale percentages are estimated from outcrops as well as from wireline logs using empirical equations.ResultsThe Bhuban Formation exhibits the highest shale content, followed by the Boka bil, Dupi Tila, and Tipam Sandstone formations. Illite is identified as the dominant clay type and they are more prevalent in the older formations. Smectite is also present in varying proportions contributing significantly to landslide occurrences through its expansive properties. The Upper Marine Shale in Bokabil Formation contains the most smectite, followed by the Dupi Tila and Bhuban formations. The degree of weathering is evaluated through field observations and oxide analysis, with average Chemical Index of Alteration (CIA) values exceeding 75, indicating intense weathering in all formations, as clearly reflected in the outcrops. Four primary types of landslides: flow, fall, slide, and complex—are identified across all formations in varying proportions. Flow is predominant in formations dominated by single rock type, such as the Bhuban and Tipam Sandstone formations, while slides are more common in formations with alternating layers of sandstone and shale, such as the Boka bil and Dupi Tila formations.ConclusionThe findings highlight that higher shale volume, clay content, and CIA values significantly elevate the landslide susceptibility of geological formations, especially when these factors are compounded by primary triggers like intense rainfall and human-induced slope modifications.

Structure and mineralization potential of the southwestern part of Sokoto Basin in Nigeria

This study investigates the lithological boundaries, structural features, and mineralization potential in the southwestern part of the Sokoto Basin, Nigeria, using an integrated approach involving high-resolution aeromagnetic, radiometric, and Landsat 8 multispectral data. The aeromagnetic data were enhanced using tilt derivative, analytical signal, and first vertical derivative filters to delineate subsurface lithological units and structural trends. Depth-to-source estimations were carried out using Euler deconvolution and Source Parameter Imaging (SPI), while radiometric data were analyzed to map potassium concentrations indicative of hydrothermal alteration zones. Landsat 8 imagery supported lithological and structural mapping through band ratios and false-color composites. The results revealed three major magnetic zones, high (53.3–120.2 nT), intermediate (27.0–53.2 nT), and low (-50.8–22.3 nT) corresponding to different rock units. Depth models highlighted complex basement topography with favorable zones for subsurface mineralization. Structural interpretation identified faults and NE-SE trending fractures that control fluid flow. Potassium anomaly zones were associated with metamorphosed rocks such as amphibolites and quartz mica schists, indicating gold-related hydrothermal alteration aligned with major structural features. The integration of geophysical and remote sensing methods provides a more detailed and spatially extensive understanding of the subsurface geology compared to traditional field-based mapping, offering valuable insights for future mineral exploration and a refined geological interpretation of the Sokoto Basin.

Geochemical anomalies of Cu–Mo in the southeastern part of Jiroft, Kerman Province, Iran: evidence for a new porphyry copper district in the southern sector of the Urumieh–Dokhtar Magmatic Belt

The Urumieh–Dokhtar Magmatic Belt (UDMB) is a major metallogenic province in Iran, hosting several Cu ± Mo ± Au porphyry deposits. The southeastern part of Jiroft, Kerman Province, lies within this belt, where contrary to previous studies, recent field reconnaissance implies that volcanic rocks of the area are intruded by unexplored fertile Cu-bearing intrusive bodies. In this region, supergene alteration has also caused the impregnation of surficial stockworks with malachite and iron oxide/hydroxides, especially in the central parts, where fertile quartz diorite units are exposed. Mo mineralization is observed at a distance from the centre of the porphyry system. Rock units of the study area show clear alteration zones that can be easily differentiated. Potassic alteration, located mostly in the central parts, is covered by phyllic, argillic and propylitic alteration at shallower depths. In the present study, systematic sampling of rock units, including 309 lithogeochemical samples with 28 vein samples containing quartz + malachite, was carried out. Anomaly maps of Cu–Mo were analysed using classical statistics (median + nStev), multifractal concentration–number (C-N), concentration–area (C-A) and singularity index (SI) methods. Using the fractal C-A method, we obtained threshold limit values of 79.43 ppm for Cu and 15.85 ppm for Mo, which reflect the intensity of the anomaly and the presence of primary mineralization, supergene and enrichment phases. Weak anomalies and those that were hidden between the background with the enriched and depleted areas for Cu–Mo were determined using the SI method.

Geologic Map of the Skull Ridge Quadrangle, Sheridan County, Wyoming USA

This project involved the construction of a detailed geologic map of the Skull Ridge, Wyoming 7.5-Minute Quadrangle (Scale 1:24,000) and supported the broader efforts of the Wyoming State Geological Survey to complete 1:24,000 scale geologic maps of the state. The quadrangle includes parts of the Bighorn National Forest and the Amsden Creek Wildlife Habitat Management Area, which are popular recreation sites for thousands of people each year. This research advances the scientific understanding of the geology of the Bighorn Mountains and the Archean geology of the Wyoming Province. Traditional geologic mapping techniques and FieldMove Clino were used in concert with petrography, geochemistry and isotopic age determinations. Our goal was to further subdivide the various phases of the 2.8–3.0 Ga Archean rocks based on their rock types, age, and structural features. The northern part of the Bighorn Mountains is composed of the Bighorn batholith, a composite complex of intrusive bodies that were emplaced between 2.96–2.87 Ga. Our mapping of the Skull Ridge Quadrangle has revealed the presence of three different Archean quartzofeldspathic units, eight sets of amphibolite and diabase dikes, and a Phanerozoic sedimentary section including the Cambrian Flathead Sandstone through the Pennsylvanian Amsden Formation deformed by two possible blind faults and forming an anticline along the northern section of the mapping area. The Archean rock units’ range in age from ca. 2.91–2.86 Ga, which correlates with other basement rocks reported in the Bighorn batholith. All the Archean rocks have subtle but apparent planar fabric elements, which are variable in orientation and are interpreted to represent magmatic flow during emplacement.

Analisa Kondisi Geologi berdasarkan pemetaan permukaan Daerah Kebagoran Kabupaten Kebumen Jawa Tengah

Analysis of Geological Setting based on surface mapping of Kebagoran Area, Kebumen Regency, Central Java: Kebumen is an area of subduction that originally served as an ocean floor, which later emerged due to the collision of two tectonic plates around 117 to 60 million years ago, specifically the Eurasian continental plate and the Indian oceanic plate Asikin.S. (1992). The Kebagoran area in Pejagoan Subdistrict, Kebumen Regency, Central Java Province, is an area consisting of hills and plains that extend in a generally west-east direction, and is within the South Serayu Mountains Zone. Research on geological conditions to determine several aspects, namely including geomorphology, stratigraphy, and geological structure, locally. The research method used is by conducting surface mapping, laboratory and studio analysis stages. surface mapping by taking direct measurements in the field, laboratory analysis using thin incisions of rocks and micropaleontology, studio analysis by analyzing data and making maps. The geology of the study area has two types of geomorphological units based on morphogenesis, namely homocline hills geomorphology unit and alluvial deposits geomorphology unit. Based on lithostratigraphy, the rock units are divided into five different units based on age, from the oldest to the youngest. The geological structure in this area consists of faults with horizontal type.

Design optimisation of Jwaneng mine cut 9 waste dumps

This study includes a detailed review of the Jwaneng Diamond Mine waste dumps using a recent comprehensive rock waste, stockpiles and tailings stability assessment method called Waste Dump Stability Rating and Hazard Classification System (WSRHC), a finite element method-based program called RS2 and a limit equilibrium program called SLIDE both from Rocscience Inc. They prove to be more hazardous as the dumps are growing in size and are getting affected by major mine developments like Cut 9 pushback which is advancing to the place where most of the old waste dumps are located. The stability status of these Jwaneng Diamond Mine waste dumps has not been studied at large convincingly. As with the open pit, monitoring of the current waste dumps should be an integral part of Jwaneng mine operations. Visual inspections are recommended to be done around the dumps and on-top to check for failed material and newly formed tension cracks. Intense tracking/monitoring of displacements/failures within the dumps, is a must practice specially a day after significant blasting in the Cut 9 walls and about 3 days after heavy rainfalls of the magnitude like the one of Cyclone Dineo. For such visual inspection, several recommendations are proposed. These are installation of different Radar systems such as Time Domain Reflectometers (TDR) and inclinometers, to detect movements of deep-seated slip surfaces, installation of Piezometers to monitor water table levels and seasonal ground moisture variations, installation of interferometric Synthetic Aperture Radars and comparison of weekly Digital Terrain Models (DTM), installation of Frequent field tests to obtain bearing capacities of the foundation material in the Jwaneng mine dumps, monitoring of saturated unit weights for the individual rock units (and sand), designing a systematic drainage or relief plan and construction of complete hydrogeological model considering regional water flow patterns of the study area.

The Weighted Values of the Factor's Classes Based on Different Approaches for Potential Zones of the Groundwater Mapping Using Remote Sensing Data and GIS Technique in the Taiz Region, Yemen

Remote sensing and geographical information system (GIS) have become one of the leading tools in the field of groundwater, which help in assessing, monitoring, and mapping groundwater resources, especially in semi-arid areas. The objective of this paper is to assess and to map groundwater potential zone in Taiz Governorate by the overlaying technique of the geospatial factors. The available twelve factors were prepared in this work from different data sources using several processes. The soil and landuse factors were prepared from Landsat-7 with the colour enhancement technique and supervised classification. The lineament, automatic drainage, slope, elevation steepness (topography) and aspect were derived from DEM, rock units, geological faults, and contact created from previous geological map. Geophysical subsurface faults were also prepared from previous magnetic faults. The rainfall data was generated from the previous annual rainfall reading. All these maps were prepared and classified to be suitable for weighted values and GIS overlying model. The manual, scaling, and matrix weighted values were assigned to the factor (raster) maps to produce three groundwater potential zone maps. These maps were classified into five classes as very low, low moderate, high, and very high potential zones. Three groundwater potential maps produced in this work were compared together and evaluated using matching technique with previous prospecting groundwater map. The percentages of the matching were 58.56 % for the potential map of the matrix analysis, 27.95 % for the potential map of the scaling equation, and 13.49 % for the potential map of the manual weighted values. This evaluation shows that the potential map of matrix weighted values scored the highest of matching, and it is the best potential map compared with the other two maps. The new finding in this work was more than six new places in the best groundwater potential map of the area noted as new groundwater potential areas. The locations of these areas were NE corner, S-SW, W, NW corner, N, and some places in the central parts of the studied area. Hence, the resultant map may contribute to optimize the choice of location of future drilling, and to increase the chances to take water from new wells which will satisfy the increasing water demand of local population. Moreover, the groundwater potential zone map was assessed for the first time using these techniques in the area, and all maps of the factors created in this research are new maps that may represent the new database of the area.

Carbon Sequestration in Indiana—a Brief Overview

The practice of capturing and storing carbon dioxide, or “carbon sequestration,” has gained significant interest due to growing domestic energy and manufacturing needs and the resulting emissions. Carbon dioxide emissions can be decreased in numerous ways, including capturing emissions from industrial facilities or directly from the atmosphere and either utilizing or permanently storing them. These practices are termed “carbon capture and storage” or “carbon capture utilization and storage.” This article provides an overview of geologic carbon sequestration, including its history, regulatory oversight, U.S. Environmental Protection Agency Class VI permitting, and the potential risks associated with the practice. Rock units found in Indiana and why they are being explored as potential reservoirs for geologic sequestration projects are also discussed. More information on frequently used scientific terms and a list of acronyms used throughout the paper are provided in Appendix I.

Waterjet Cutting Sandstone Ability Test and Process Parameter Optimization Research

In China, 90% of the outburst accidents are directly related to the hard roof overburden. To enhance the top-pressure relief effect of the pre-determined directional fractures by water jet cutting, this study selected relatively hard fine-grained sandstone in the underground coal mine as the test material. Through single-factor experiments and orthogonal experiments, the influence laws of water jet process parameters (jet pressure, horizontal movement speed, cutting target distance, abrasive concentration, and cutting angle) on the rock-cutting ability were systematically analyzed. The SPH-FEM coupling method was adopted to simulate the rock-breaking process of water jet-cutting fractures. The results of single-factor experiments showed that jet pressure was positively correlated with the rock-cutting characteristic index, while lateral displacement speed was negatively correlated with it. The cutting depth showed a trend of increasing first and then decreasing with the increase of cutting target distance and abrasive concentration. The optimal target distance was 10 mm, and the optimal abrasive concentration was 12%. The cutting angle showed two depth peaks at 80° and 100°, indicating that adjusting the angle could significantly improve the cutting efficiency. The results of the four-factor five-level orthogonal experiments showed that in the case of a fixed abrasive concentration, the primary and secondary factors affecting the cutting depth were jet pressure, horizontal movement speed, cutting angle, and cutting target distance. The optimal parameter combination for water jet cutting fine-grained sandstone was jet pressure 60 MPa, horizontal movement speed 100 mm·min-1, cutting target distance 20 mm, and cutting angle 85°. Based on the experimental results, a cutting-depth prediction model for fine-grained sandstone was constructed. The numerical simulation indicated that the abrasive water jet impact induced shear failure of the rock unit under the compression stress dominance, and the stress field showed a dynamic evolution characteristic of gradient attenuation from the impact center to the edge, forming an incremental damage area centered on compression failure. The prediction model and simulation results provided a theoretical basis for the optimization of water jet cutting technology, and the research results have important practical reference value for the top roof top-pressure relief engineering in coal mines.

Biostratigraphy, Paleoenvironments, and Paleobiogeography of the Middle–Upper Eocene Ostracods from Northwestern and Northeastern Banks of the Nile Valley, Egypt

The middle and upper Eocene sedimentary successions exposed along the northwestern and northeastern portions of the Nile Valley, Egypt, have been thoroughly examined for their ostracod assemblages. This study enhances the understanding of biostratigraphic zonations and evaluates the paleobiogeographic distribution and paleoenvironmental conditions that prevailed during the deposition of this sedimentary record. Lithostratigraphically, the studied successions are subdivided into four stratigraphic units, arranged in ascending order as follows: the Qarara, the El Fashn, the Gehannam, and the Beni Suef formations. A total of 125 rock samples were selected and well analyzed, resulting in the identification of sixty-five ostracod species and subspecies belonging to thirty-three genera, fifteen families, and three superfamilies. The stratigraphic distribution of the recorded ostracod taxa contributed to the construction of four local biozones, spanning the interval from the upper Lutetian to lower Priabonian: Schizocythere fadlensis Zone (upper Lutetian–lower Bartonian), Loxoconcha pseudopunctatella Zone, Dygmocythere ismaili Zone (Bartonian), and Asymmetricythere hiltermanni Zone (Bartonian–Priabonian). These biozones are well described, discussed, and correlated with those previously documented in different areas of Egypt and neighboring countries. The statistical analysis, supported by ternary plot diagrams, indicates that the depositional environments of the studied rock units fluctuated between shallow inner neritic and deeper outer neritic marine environments. The identified taxa display a wide geographic distribution and show a significant similarity with those identified in the southern, northern, and eastern Tethyan provinces, suggesting a direct marine connection during the Eocene.

Geology and Structural Evolution of the Region between the Upper Kelkit Basin and Munzur Mountains

The purpose of this study is to analyse the structural evolution of the region where the Eastern Pontides and the Eastern Taurides are closest to each other. The main tectonic units in the area, from north to south, are the Kelkit Paraautochthonous Unit, Çimendağ Nappe, Erzincan Nappe and Munzurdağ Limestone Unit. The pre-Jurassic basement of the tectonic units consists of heterogeneous rock units in different areas. Since the relationships between these units cannot be established in the study area, it is not possible to create a model for the pre-Jurassic period with the evidence from this locality. Therefore, the tectonics, tectono-stratigraphic and structural evolution of the study region were evaluated only for the Jurassic-Quaternary interval. The Jurassic-Early Cretaceous Kelkit Paraautochthonous Unit and Çimendağ Nappe represent the genesis of rifting and then deposition of platform-type carbonates in the Eastern Pontides. The Jurassic-Early Cretaceous Munzurdağ Limestone Unit represents the northernmost part of the Eastern Taurides and also has features of platform-type carbonates. During this period, a mid-oceanic ridge and ensimatic arc were active together along the North Anatolian Ophiolitic Belt. Therefore, it is possible to suggest a model representing passive continental margins to the north and south, with the mid-oceanic ridge in the north and the ensimatic arc in the south along the intervening oceanic environment in the Jurassic-Early Cretaceous periods. In the Late Cretaceous-Palaeocene, all evidence shows that the extensional regime completely converted to a compressional regime. In this time interval, an ensialic arc-forearc occurred along the Eastern Pontides and an ensimatic arc with subduction complex occurred along the North Anatolian Ophiolitic Belt. In the south, pelagic carbonates were deposited along the Munzur Mountains. It seems inevitable that the existence of two different north-dipping subduction zones should be accepted in this time interval. The Eocene and Oligo-Miocene units overlie older structural units with a polygenic conglomerate and angular unconformity. These units underwent intense deformation and the entire study area first became a shallow marine and then a terrestrial environment. Eocene volcanism indicates a post-collisional phase in the Eastern Pontides. The Pliocene-Quaternary rocks, reflecting continental deposits, unconformably overlie the older units, with an approximately horizontal layered structure. Considering this unconformity and the intense deformation before the Pliocene, it is possible that the North Anatolian Fault (NAF) developed during the Pliocene and had dextral movement with at least 25 km offset. In this context, the annual slip value for the fault may be 4.7 cm/year.

Permeability scaling relationships of volcanic tuff from core to field scale measurements

A recent chemical explosive test in P-Tunnel at the Nevada National Security Site, Nevada, USA, was conducted to better understand how signals propagate from explosions in the subsurface. A primary signal of interest is the migration of gases that can be used to differentiate chemical from nuclear explosions. Gas migration is highly dependent on the rock permeability which is notoriously difficult to determine experimentally in the field due to a potentially large dependence on the scale over which measurements are made. Here, we present pre-explosion permeability estimates to characterize the geologic units surrounding the recent test. Permeability measurements were made at three scales of increasing size: core samples (≈2 cm), borehole packer system tests (≈1 m), and a pre-shot cavity pressurization test (> 10 m) across ten tuff units. Permeability estimates based on core measurements showed little difference from borehole packer tests. However, permeability in most rock units calibrated from cavity pressurization tests resulted in higher permeability estimates by up to two orders of magnitude. Here, we demonstrate that the scale of the measurement significantly impacts the characterization efforts of hydraulic properties in volcanic tuff, and that local-scale measurements (< 10 m scale) do not incorporate enough heterogeneity to accurately predict field-scale flow and mass transport.

Integrating conventional and remote sensing with DC resistivity datasets to map groundwater potential areas using the analytical hierarchy process method, North Wadi Diit, Egypt

This study investigates the groundwater potential (GWP) in Wadi Diit, an arid region with promising resource development prospects, by integrating topographic, hydrogeological, and mineralogical parameters. To analyze the study area, a combination of conventional methods, remote sensing data from Sentinel-2, ASTER-GDEM, and ASTER-L1B, as well as DC resistivity datasets was utilized. The study region comprises Precambrian, Tertiary, and Quaternary surface rock units, supporting lithosol and Yermosol soil types. Barren lands dominate the landscape, while the southern portion experiences higher rainfall. Nine thematic layers (quartz index, carbonate index, slope, rainfall, drainage density, topographic wetness index, lineament density, land cover, and mafic index) were classified and weighted using GIS-based analytical hierarchy process, achieving a model accuracy of 0.0959. The GWP zones were categorized into very low (4.53%), low (17.33%), moderate (27.05%), high (27.79%), and very high (23.3%) categories, predominantly falling within moderate to very high classifications. Validation through hydrogeological data from 11 wells and a receiver operating characteristic curve analysis (area under curve = 0.8) confirmed the model’s reliability. DC resistivity measurements were conducted at nine vertical electrical sounding (VES) sites using a Schlumberger array (AB/2 = 500 m) along two profiles. The data were analyzed using various inversion techniques, including unconstrained 1D-VES, laterally constrained inversion (LCI-VES), spatially constrained inversion (SCI-VES), and 2D-VES inversions. A 0.3 constraint factor was applied to assess the accuracy of the model parameters, as their STDF derived from SCI-VES data were determined to be well-resolved. The SCI-VES and 2D-VES inversion results identified four distinct geological layers; unconsolidated surface deposits, gravelly-sand sediments of fresh-brackish Quaternary aquifer (30–384 Ω m and 3.7–15.9 m depth), saturated clayey-sand deposits, and saline Fractured Basement aquifer (10–137 Ω m and 33–90.4 m depth). The region exhibits a complex geological structure, characterized by an uplifted Fractured Basement aquifer trending southeast and southwest as indicated by 2D-VES models. The north-central region emerges as the most favorable location for substantial GWPZ, making it strategically ideal for the installation of additional water wells.