Similar Lithologies Research Articles

Geosites Exploration and Clustering Analysis of Geodiversity in UGGp Kebumen Geopark Based on the Similarity of Characteristics in a Geomorphosite

Abstract This research aims to explore and update geosite data in Kebumen Regency, which has been recognized as a UNESCO Global Geopark (UGGp), reflecting the importance of this area in terms of geological diversity. This study aims to explore and update geosite data in Geopark Kebumen, which is an integral part of the existing geodiversity area, as well as clustering based on similarities in geological processes, characteristics, lithology, and geomorphology. The methods used include field exploration and laboratory analysis. The data obtained was then analyzed using a clustering approach to understand the geosite linkages. As a result, UGGp Kebumen Geopark is divided into six geomorphosite clusters: Melange Geomorphosite Cluster, which reflects mixed materials resulting from subduction processes; Olistolith Geomorphosite Cluster, which consists of large avalanches due to tectonic activity; Volcanic Geomorphosite Cluster, with ancient volcanic rock formations; Marine Sediment Geomorphosite Cluster, from marine sediment deposits; Karst Geomorphosite Cluster, which is formed from the dissolution of carbonate rocks, and Coastal Geomorphosite Cluster, which illustrates the interaction between land and sea. The geosite clustering method and geomorphosite units provide a deeper understanding of Kebumen’s geodiversity. This clustering helps identify geosite potential more specifically and facilitates geopark management. With accurate mapping, sustainable development planning becomes more effective, supporting environmental preservation, as well as tourism and education-based economic development, in line with sustainability principles.

Geophysical downhole logging analysis within the shallow-depth ICDP STAR drilling project (central Italy)

Abstract. The International Continental Scientific Drilling Program (ICDP) STAR (A Strainmeter Array Along the Alto Tiberina Fault System) drilling project aims to study the seismic and aseismic fault slip behavior of the active low-angle Alto Tiberina normal fault (ATF) in the northern Apennines, central Italy, by drilling and instrumenting six shallow boreholes (maximum depth 160 m) with seismometers and strainmeters. During the STAR fieldwork, a geophysical downhole logging campaign was carried out to define the optimal target depth for instrument deployment and formation rock characterization. In particular, the main objectives of this study were to define in situ physical properties of the rocks and the tectonic discontinuity geometry along the boreholes. The downhole logging data provide new findings and knowledge, especially with regards to physical properties such as resistivity and gamma-ray and wave velocity. The collected parameters were compared to the results of literature data collected in similar lithologies, as well as with the results of logging performed in deeper wells drilled for commercial purposes. The physical properties of the Mesozoic–early Tertiary calcareous formations show low gamma-ray values and high compressional (Vp) and shear wave (Vs) velocities (up to 5.3 and 2.9 km s−1, respectively), whereas the overlying clay-rich Late Tertiary formations exhibit high gamma-ray and low resistivity values as well as relatively low Vp and Vs values (up to 3.5 and 2.0 km s−1, respectively). The results obtained from the analysis of the orientations of the tectonic structures, measured along the six boreholes, show good agreement with the orientations of the present-day extensional stress field, which is NE–SW-oriented. Our study allowed us to bridge the gap between the physical properties obtained from literature data and those obtained from the deep well measurements, representing a possible case history for future projects. These new outcomes represent an almost unexplored window of data and will contribute to the advancement of knowledge of the physical properties of the rocks at shallow depths, which are typically overlooked.

In-situ and experimental investigations of the failure characteristics of surrounding rock through granites with biotite interlayers in a tunnel

Significant differences in the failure characteristics of surrounding rocks caused by complex lithologies and geological conditions have been observed in deep tunnels. In this work, a failure involving rockburst and collapse observed in a deep tunnel excavated by a tunnel boring machine (TBM) was introduced. The in-situ failure characteristics of granite with biotite interlayers with different biotite contents and particle sizes were studied via field investigations and mineral composition analysis. The microseismic activity characteristics and fracture mechanisms at different failure zones were analyzed. The strength, failure, acoustic emission (AE) and brittleness characteristics of these types of granites were studied via true triaxial compression tests. The results showed that the biotite granite with biotite interlayers is prone to rockburst and that high-intensity rockburst may occur with less energy than in the intact biotite granite area. The rock fractures are mainly tensile failures, even in the biotite interlayer area. In contrast, the feldspar biotite schist surrounding rock is prone to collapse regardless of whether it contains biotite interlayers. The number of microseismic events during this collapse is relatively small, but the energy is relatively high compared with that of the rockburst at the biotite granite with biotite interlayers. The true triaxial strength and brittleness of the granite samples gradually decrease with increasing biotite content. The biotite granite exhibits very high AE activity, so it is prone to rockburst. The AE activity of medium-coarse grained monzogranite is relatively low; thus, both rockburst and collapse may occur. The strength, brittleness, and AE activity of feldspar biotite schist are very low, and its failure mode is mainly collapse. This study elucidates the typical failure modes and characteristics of different granites with biotite interlayers and can provide a basis and guidance for targeted failure warning and mitigation in tunnels with similar lithologies and geological conditions.

Relating ten years of rock temperature monitoring to rockwall weathering processes in steep mountain valleys in western Norway

Most existing studies on rockwall frost regimes and frost weathering at rockwalls focus on permafrost-affected rockwalls. However, a high share of rockwall surface areas in Norway and in many other cold-climate environments is actually free of permafrost. It is therefore of interest how these permafrost-free rockwall systems will respond to future changes in air and rock temperatures. In this study, we report field measurements conducted at rockwalls beneath the current permafrost limit and investigate thermal regimes at rockwalls that include both rockwall areas with and without permafrost. We present a unique dataset of up to ten years of rockwall temperature measurements from ten temperatures sensors installed in two mountain valleys in western Norway. An analysis of the different rockwall thermal regimes with respect to rock weathering and associated rockfall supply for both, permafrost-affected and permafrost-free rockwalls is provided. The highest intensity of recent rockwall weathering including determined rockwall retreat rates and associated rockfall supply is detected for northeast-facing rockwalls followed by south-facing rockwalls in our study area. Frost cracking activity, probably in the form of segregation ice growth, seems to be an important factor particularly for the high weathering intensity on northeast-facing rockwalls whereas solar radiation-induced thermal stresses, which favour incremental subcritical crack growth, is assumed to play a relevant role in the moderate weathering intensity on south- and southwest-facing rockwalls. A mean annual and study area-wide rockwall retreat rate of 0.24 mm yr−1 is estimated for our ten-year investigation period (2010−2020) which is comparable to other published rates in similar lithologies and climates. As it can be assumed that seasonal frost regimes and permafrost will react differently to ongoing and future climate changes, more attention should be paid to analyse these two different thermal regimes with respect to possible varied implications for mechanical rockwall weathering and associated rockfall supply.

Research on elastic parameter inversion method based on seismic facies-controlled deep learning network

Deep learning has been widely applied in the field of geophysics, and existing research literature has demonstrated that intelligent geophysical inversion methods have high vertical resolution but low horizontal resolution. The reason lies in the fact that existing horizontal constraint methods mainly adopt convolutional models, without fully considering other prior information of seismic data. Within the same sedimentary unit, seismic response characteristics vary gradually due to similar lithology and geological characteristics. Therefore, the seismic facies information extracted from seismic data is integrated into deep learning network to enhance the horizontal prediction stability of the network. Firstly, according to the spatial and temporal characteristics of seismic data, a fusion network of three-dimensional convolutional neural network (3D-CNN), gated recurrent unit (GRU) and attention mechanism is established to improve the vertical resolution of inversion results. Then, seismic facies classification of the target layer is achieved by applying the K-means clustering method. Subsequently, to improve the horizontal resolution of the inversion results, seismic facies classification is transformed into temporal encoding data using the position coding theory in natural language processing, to form a seismic facies-controlled deep learning network. Finally, the deep learning network is trained and tested in the thin interlayer model and practical application adopting a semi-supervised learning method. The results indicate that incorporating seismic facies-controlled technology in the deep learning network can improve the horizontal resolution of the inversion results.

Micro–Nano 3D CT Scanning to Assess the Impact of Microparameters of Volcanic Reservoirs on Gas Migration

Volcanic rock reservoirs for oil and gas are known worldwide for their considerable heterogeneity. Micropores and fractures play vital roles in the storage and transportation of natural gas. Samples from volcanic reservoirs in Songliao Basin, CS1 and W21, belonging to the Changling fault depression and the Wangfu fault depression, respectively, have similar lithology. This study employs micro–nano CT scanning technology to systematically identify the key parameters and transport capacities of natural gas within volcanic reservoirs. Using Avizo 2020.1software, a 3D digital representation of rock core was reconstructed to model pore distribution, connectivity, pore–throat networks, and fractures. These models are then analyzed to evaluate pore/throat structures and fractures alongside microscopic parameters. The relationship between micropore–throat structure parameters and permeability was investigated by microscale gas flow simulations and Pearson correlation analyses. The results showed that the CS1 sample significantly exceeded the W21 sample in terms of pore connectivity and permeability, with connected pore volume, throat count, and specific surface area being more than double that of the W21 sample. Pore–throat parameters are decisive for natural gas storage and transport. Additionally, based on seepage simulation and the pore–throat model, the specific influence of pore–throat structure parameters on permeability in volcanic reservoirs was quantified. In areas with well–developed fractures, gas seepage pathways mainly follow fractures, significantly improving gas flow efficiency. In areas with fewer fractures, throat radius has the most significant impact on permeability, followed by pore radius and throat length.

Geochemical distribution of major and trace elements in hydromorphic soil profiles developed on recent alluvium

Geochemical composition and distribution of major elements study is vital in terms of investigating the major soil forming compounds and to know the fate of trace elements in soils. Particle size distribution (PSD), pH, organic carbon (OC), and major and trace elements of hydromorphic soils formed on recent alluvium in Obafemi-Owode Local Government Area of Ogun state, Nigeria were analysed using standard procedures. Three profiles pits were dug based on the mapping units identified, and samples were collected for laboratory analysis. Data were subjected descriptive statistics and Pearson’ correlation coefficients using IBM SPSS version 27. The PSD was dominated by sand content, followed by clay and silt, and soil pH in KCl was strongly acid (3.17–4.30) and pH in H2O was moderately acid (4.74–5.80), while OC contents were low to moderate (1.22–6.69 g/kg). The major elemental results showed higher concentration of SiO2 (>50 %) connotes presence quartz, feldspar, and clay minerals. Manganese, Cu, Ba, Zr, and Zn have higher concentrations among the trace elements. Major elements ratios (SiO2/Al2O3, K2O/Al2O3) showed moderate weathering stage, while trace elements ratios (Ni/Co and Cu/Zn) revealed deposition under humid conditions and anoxic environment. The statistical analysis revealed that most elements have skewness closed to zero except MgO and K2O. Correlation coefficients between the elements are positive and significant (p < 0.05 and p < 0.01) indicating that their presence can be accounted for by similar lithology, though some have negative relationship which could be as a result of anthropogenic activities. The study found that elements were potential tracers for the presence of human activities and environmental changes.

GEOLOGY OF ALAKNANDA BHGIRATHI AND YAMUNA VALLEY, GARHWAL HIMALAYA, PARTS OF CHAMOLI TEHRI UTTAKASHI &amp; PAURI DISTRICTS, UTTRAKHAND STATE, INDIA

The Alaknanda is the trunk stream of Ganga system it drains the eastern part of the area of study .The rocks of Alaknanda valley and adjoining area consist of three units viz Central Cryastalline , Garhwal Group and Dudatoli Groups which from north to south are separated by thrust or fault. The Central Crystalline Group in this area consist of /comprises of northerly dipping sequence of Kyanite schist,Garnet mica schist quartzites and para amphibolites of Tugnath formation and it is intruded by granite at Ragsi,the main Central Thrust seprates it from Garhwal Group.The Dudatoli Groupis represented Pauri Phyllite and Kirsu Quartzite which forms the northern limb of Dudatoil syncline .The north Almora Thrust makes it boundary with Garhwal group. The later is divisiable in to Rudraprayga ,Lamri , Chamoli and Gawangarh and Patrali Formation which occurs in normal stratigraphic order. It is intruded by biotite granite by biotite graninte at Nainidevi and Mohankal , with tourmaline granite around Chirpatikhal and also by basic intrusive . The Rudraprayg , Lameri and Chamoli formations are equivalent to Uttarkashi Shyalnan and Nagnithhank Formation respectively in Bhagirathi valley. The Garhwal Group of has been subjected to three phases of tectonic deformation. The south east to southerly plunging folds such as Marithanasa and Pingapani synclines .Karanprayg anticline were developed during the second phase of movements. The Alaknada fault which cuts off set of the formation and earlier structures between Sunala is the strike slip fault in western part, appears to be the youngest elements. Geologically , the Bhagirathi valley and adjoining areas comprises of four distinct units namely from north to south the Central Crystalline Group , the Deoban Group the Simla Group,and Krol belt rock separating from one another by thrust or faults. The main Central Thrust passing through Sainj in northern part brings the northerly dipping crystalline rocks in sharp contact with under lying Deoban Group (Garhwal Group) sedimentries which comprises a lower Deoban Formation of Phyllite, slate meta basics, minor quartzite and lime stone, the middle Deoban formation of lime stone and upper Deoban formation of Quartzite and basics. The southern contact of Deoban Group is faulted one with comprising mainly siltstone, greywacks and slates dipping south .This fault called Sringar Nalupani fault of fundamental nature. In the southern and eastern part of the area this fault marks the contact between Deoban and Chandpur formation. In the western part south heading Ton Thrust separates the underlying Chanpur formation from the underlying Simla slates which shows abundant development of slump balls rod etc. indicating syndepositional disturbances in the basin of sedimentation while in Chanpur formation, is manly argillaceous, becoming arenaceous towards the top The Tons thrust passes through Laluli in Nagun Gad and is probably truncated by Tehri Nalupani fault at Chandpur in Bhagirathi valley. The full sequence of Krol rocks is exposed beautifully in Mussoorie syncline. The tectonic succession in Yamuna valley is Naogaon sheet comprising more metamorphosed rocks overly the Deoban group rocks separated from the latter by what is called the Naugaon thrust sheet which is folded in a North to Northwest plunging synform. The western limb of the folded thrust crosses Yamuna near the confluence with Kamola Gad and runs along the Kamola Gad. The rocks of the Naugaon sheet can be seen overlying the Deoban formation limestone along this section. The thrust hade towards east in this section. It follows a southerly trend till Tiyan when it takes an easterly swing, heading northward. It closes around Gair. The eastern limb of the synformal thrust sheet, heading westward crosses the Yamuna River at Kisna, Basic intrusive are seen along the thrust sheet near Kisna and around. The complexity of structural and tectonic set up in the area and lack of fossils make the task of correlation extremely difficult. However, on the basis of lithological similarities as well as structural disposition an attempt has been made to correlate the various litho units in the present area.

The El Gigante Metamorphic Complex: A missing block with a Grenville-age basement in the Western Sierras Pampeanas, Argentina

The southwestern paleo-margin of Gondwana is interpreted as an accretionary margin that was active from the late Neoproterozoic to the late Paleozoic. The basement of this paleo-margin is widely exposed in the central-western part of Argentina (Sierras Pampeanas area), where a protracted evolution from the Mesoproterozoic to the late Paleozoic is recorded. Part of this evolution is preserved in the El Gigante Metamorphic Complex (Sierra de El Gigante; Western Sierras Pampeanas), a small rotated block within the Valle Fértil Lineament fault zone that separates the Western and Eastern Sierras Pampeanas. The complex is composed of medium-grade meta-siliciclastic and meta-carbonate rocks and medium- to high-grade meta-igneous rocks, affected by tight to isoclinal folds and a pervasive east–west foliation resulting from the Famatinian orogeny (broadly late Cambrian to early Devonian). Later events include localized ductile shear zones. The isotopic and geochronological data from El Gigante Metamorphic Complex reveal at least three distinct lithological assemblages: (1) metamorphosed felsic igneous rocks of ca. 1.11 Ga, i.e., late Mesoproterozoic, (2) a Neoproterozoic metasedimentary succession composed of quartzites and mica-schists, (3) possibly mid- to late-Cambrian marble and graphite-schist. The Grenvillian assemblage (1) was part of a large reworked Paleoproterozoic continental block called MARA (acronym of Maz-Arequipa-Río Apa) and was the basement over which the Neoproterozoic and Cambrian sedimentary successions were deposited. Based on U-Pb zircon ages, lithological similarities and Sr-isotope data, the three lithological assemblages of the El Gigante Metamorphic Complex can be correlated with similar ones in the nearby geologically better-known Sierra de Pie de Palo. The Neoproterozoic and the Cambrian metasedimentary successions are respectively equivalent to the Difunta Correa Metasedimentary Sequence and the Nikizanga-Caucete Groups, which are recognized throughout the Sierras Pampeanas, east and west of the Valle Fértil Lineament.

The Northbrae rhyolite of Berkeley (California, USA) constrains motion of the proto-Hayward Fault

ABSTRACT Right-lateral transform motion associated with the Pacific-North American plate boundary in the modern-day San Francisco Bay Area occurs across a series of sub-parallel fault zones. Much of this motion is accommodated east of the San Andreas Fault by the faults of the East Bay fault system. A major tool for reconstructing the spatial and temporal history of fault motion is the correlation of offset Neogene volcanic rocks. These Neogene volcanics within the California Coast Ranges formed in association with the slab gap that grew as the Mendocino Triple Junction migrated northward. Some of the volcanic centres have been variably offset by subsequent strike-slip faulting. A felsic volcanic unit exposed in Berkeley, CA, known as the Northbrae rhyolite has variably been interpreted to be one of these Neogene volcanic units or to be a Mesozoic volcanic unit associated with the Coast Range ophiolite. A new U-Pb zircon date of 11.10 ± 0.09 Ma confirms the Neogene volcanic interpretation. This date is indistinguishable from previously published Ar/Ar dates from the Burdell Mountain volcanics of the North Bay region as well as a new U-Pb zircon date of 11.07 ± 0.10 Ma. In addition to the indistinguishable ages, similarities in bulk lithology, zircon crystallization/dissolution textures, and zircon trace element geochemistry are consistent with these rhyolites being associated with the same volcanic centre. This correlation implies that 40 ± 5 km of right-lateral offset occurred to the west of the modern-day position of the Hayward-Rodgers Creek fault zone. This offset represents ∼ 20% of the total offset along the East Bay fault system. A proto-Hayward Fault with a different geometry than that of the present-day played a significant role in the evolution of the fault system. This result highlights the dynamic spatiotemporal variability of strike-slip faults along transform margins.

Limited Evidence of Late Quaternary Tectonic Surface Deformation in the Eastern Tennessee Seismic Zone, United States

ABSTRACT The ∼300-km-long eastern Tennessee seismic zone, United States, is the secondmost seismically active region east of the Rocky Mountains. Seismicity generally occurs below the Paleozoic fold-and-thrust belt within the Mesoproterozoic basement, at depths of 5–26 km, and earthquake magnitudes during the instrumental record have been moment magnitude (Mw) ≤4.8. Evidence of surface deformation may not exist or be difficult to detect because of the vegetated and soil-mantled landscape, landslides, locally steep topography, anthropogenic landscape modification, or long, irregular recurrence intervals between surface-rupturing earthquakes. Despite the deep seismicity, analog models indicate that accumulation of strike-slip or oblique-slip displacement at depth could be expected to propagate upward through the Paleozoic section, producing a detectable surficial signal of distributed faulting. To identify potential surface deformation, we interrogated the landscape at different spatial scales. We evaluated morphotectonic and channel metrics, such as channel sinuosity and catchment-scale hypsometry. In addition, we mapped possible fault-related topographic features on 1-m lidar data. Finally, we integrated our observations with available bedrock and Quaternary surficial mapping and subsurface geophysical data. At a regional scale, most morphotectonic and channel metrics have a strong lithologic control. Within smaller regions of similar lithology, we observe changes in landscape metrics like channel sinuosity and catchment-scale hypsometry that spatially correlate with new lineaments identified in this study and previously mapped east–west Cenozoic faults. These faults have apparent left-lateral offsets, are optimally oriented to slip in the current stress field, and match kinematics from the recent focal mechanisms, but do not clearly preserve evidence of late Pleistocene or Holocene tectonic surface deformation. Most newly mapped lineaments might be explained by either tectonic or nontectonic origins, such as fluvial or karst processes. We also reevaluated a previously described paleoseismic site and interpret that the exposure does not record evidence of late Pleistocene faulting but instead is explained by fluvial stratigraphy.

Potential controls on magmatic Ni-Cu sulfide mineralization in orogenic belts: Constraints from mineral compositions of the Huangshandong and Erhongwa intrusions in eastern Tianshan, NW China

Numerous Permian mafic-ultramafic intrusions are situated in the eastern Tianshan Orogen at the southern margin of the Central Asian Orogenic Belt. These intrusions demonstrate a diverse range of magmatic Ni-Cu sulfide mineralization. Notably, the Huangshandong intrusion hosts a large Ni-Cu sulfide deposit, whereas the Erhongwa intrusion lacks any economically significant sulfide mineralization. Both intrusions exhibit similar lithologies and mainly consist of lherzolite, gabbro, gabbronorite and diorite.To elucidate the controlling factors influencing the disparity in mineralization between two intrusions, analyses were conducted on the compositions of olivine, spinel, pyroxene and amphibole. Olivine grains from the Erhongwa lherzolite have lower Ni (361–943 ppm) contents than those from Huangshandong layered lherzolite (Ni 684–864 ppm) and Huangshandong massive lherzolite (Ni 1218 to 1878 ppm). This discrepancy may be attributed to early sulfide separation occurring at greater depths. Modeling results indicated that for the Huangshandong mantle source, 1 % slab-derived melts and 2 % slab-derived fluids were incorporated; conversely, for the Erhongwa mantle source, approximately 2.5 % slab-derived melts and 0.5 % slab-derived fluids were added.Parental magmas of the Erhongwa intrusion exhibit higher oxygen fugacity and water contents than those of the Huangshandong intrusion. Specifically, the magma of the Erhongwa intrusion undergoes magma evolution within a shallow magma chamber, whereas the magma of the Huangshandong intrusion gains sulfide saturation within a deep magma chamber. This research suggests that factors including mantle source features, suitable timing for sulfide separation, and depth of magma chamber are essential for Ni-Cu sulfide mineralization in mafic-ultramafic intrusions in convergent margin setting.

On the rocks: Biogeography and floristic identity of rocky ecosystems in eastern South America

AbstractThe geodiversity of rocky ecosystems includes diverse plant communities with specific names, but their continental‐scale floristic identity and the knowledge on the role of macroclimate remain patchy. Here, we assessed the identity of plant communities in eastern Brazil across multiple types of rocky landscapes and evaluated the relative importance of climatic variables in constraining floristic differentiation. We provided lists of diagnostic species and an assessment of the conservation status of the identified floristic groups. We compiled a data set of 151 sites (4498 species) from rocky ecosystems, including campos rupestres, campos de altitude, granitic‐gneiss lowland inselbergs, and limestone outcrops. We used unsupervised clustering analysis followed by ANOSIM to assess floristic groups among sites. We performed a random forest variable selection to test whether the identified floristic groups occupy distinct climatic spaces. Six groups (lithobiomes) segregated floristically according to lithology and climate. Alongside campos de altitude and limestone outcrops, inselbergs were divided according to the biome in which they occur (Atlantic Forest or Caatinga), and campos rupestres were largely segregated according to their lithological matrix (ironstone or quartzitic). Plant communities of Caatinga inselbergs were more similar to limestone outcrops, while Atlantic Forest inselbergs communities resembled campos de altitude. The composition of plant communities on outcrops seems to be largely constrained by lithology, but climatic factors are also meaningful for sites with similar lithology. The current network of protected areas does not cover these unique ecosystems and their floristic heterogeneity, with Caatinga inselbergs and limestone outcrops being the least protected.

Can palaeosols reveal palaeoenvironmental variability of fluvial systems? An example from the upper portion of the Bauru Group (Upper Cretaceous, SE Brazil)

Palaeosols are common in sedimentary successions of continental origin, and notably they comprise the majority of the thickness of some accumulated successions of fluvial origin. Yet, detailed investigation of palaeosols and evaluation of their palaeoenvironmental significance are not routinely undertaken in detail in many sedimentological studies. A careful analysis of palaeosols may, however, reveal that sedimentary units, which appear similar if based solely on the facies analysis, indeed show strongly distinct palaeoenvironmental and depositional characteristics.This is the case of the upper portion of the Bauru Group, a 100–190 m-thick Maastrichtian red sandstone unit of fluvial origin, present over an area of c. 180,000 km2 in south-eastern Brazil. In this study, the palaeosols of this unit, which constitute 25–92 % of the succession by thickness, are used to decipher palaeoenvironmental climate conditions, sediment source areas, and relationships between pedogenic and depositional processes. Through the combined study of macroscopic, micromorphological, and geochemical aspects of the palaeosols and of facies analysis of the deposits, the upper portion of the Bauru Group succession is separated into three sectors: north-western, north-eastern, and south-eastern. Although these three areas are all characterised by similar lithology types and lithofacies, indicative of deposition in alluvial systems, the palaeosol analysis highlights that they were each characterised by different climate, different clastic source areas and different dynamics and interaction of the pedogenic and sedimentary processes. This research reveals the critical significance of the palaeosols for discriminating otherwise apparently similar depositional units.

Portable XRF applied to regional bedrock mapping in Quebec, Canada

Whole-rock geochemistry yields better geological maps of the bedrock, since it allows, for example, visually similar lithologies to be distinguished. However, conventional laboratory geochemistry is not available in the field during a mapping campaign. Portable X-ray fluorescence (pXRF) analyzers can produce fit-for-purpose data rapidly, and constitute a useful complement to conventional geochemistry in a bedrock mapping project. The pXRF data can be employed (i) while still in the field, to orient the mapping campaign; (ii) to prepare a preliminary geological map back in the office; and (iii) to interpolate between conventional whole-rock analyses on the final map. The latter application requires a matrix-matched secondary calibration of the pXRF data to improve its accuracy. Attention must also be given to precision issues, as well as potential instrument drift and analytical interferences.This paper summarizes recent efforts to systematically integrate quantitative pXRF data in government mapping projects within the Province of Quebec (Canada). We first demonstrate how an Olympus Vanta series M pXRF analyzer was commissioned and calibrated. We then show how the pXRF data was systematically acquired and utilized during a 1:50,000 to 1:20,000 mapping campaign in a Precambrian greenstone belt setting (Abitibi Subprovince). Before the mapping began in 2021, volcanic rocks in the study area were supposed to consist of only two mafic tholeiitic formations, called Obatogamau and Bruneau. Integrating pXRF into this project meant that while still in the field and immediately afterwards during preparation of the preliminary map: (1) a marker horizon representing the top of the Obatogamau Formation was chemically identified and then traced laterally; (2) the felsic Waconichi Formation was recognized despite the high metamorphic grade and also traced laterally just above the marker horizon; (3) the Bruneau Formation was shown to be much more continuous than previously known and to have Mg-tholeiites at its base, like in the type locality; (4) the Blondeau Formation was shown to occur above the Bruneau Formation. Within the volumetrically dominant Obatogamau Formation, Fe-tholeiites were also distinguished from visually similar Mg-tholeiites, which allowed these subunits to be traced while still in the field, leading to a more detailed map. Later, after the conventional laboratory chemistry had been received, the final geological map was prepared, but it was very similar to the preliminary map, confirming the satisfactory performance of the pXRF method for this application. However, we do note some issues and limitations even with the latest generation of analyzers.

Thermal and Structural History of Impact Ejecta Deposits, Ries Impact Structure, Germany

AbstractThe Ries impact structure (Germany) contains well‐preserved ejecta deposits consisting of melt‐free lithic breccia (Bunte Breccia) overlain by suevite. To test their emplacement conditions, we investigated the magnetic properties and microstructures of 26 polymict breccia clasts and a stratigraphic profile from the clasts into the suevite at the Aumühle quarry. Remanent magnetization directions of the Bunte Breccia clasts fall into two groups: those whose directions mostly lie parallel to the reversed field during impact carried mostly by magnetite, and those whose directions vary widely among each clast carried by titanohematite. Basement clasts containing titanohematite acquired a chemical remanent magnetization (CRM) during the ejection process and then rotated during turbulent deposition. Clasts of sedimentary rocks grew magnetite after turbulent deposition, with CRM directions lying parallel to the paleofield. Suevite holds a thermal remanent magnetization carried by magnetite, except for ∼12 cm from the contact with the Bunte Breccia, where hematite concentrations increase due to hydrothermal alteration. These observations lead us to propose a three‐stage model of (a) turbulent deposition of the melt‐free breccia with clast rotation &lt;580°C, (b) deposition of the overlying suevite, which acted as a semi‐permeable barrier that confined hot (&lt;300°C) oxidizing fluids to the permeable breccia zone, and (c) prolonged hydrothermal activity producing further alteration which ended before the next geomagnetic reversal. Basement outcrops have significantly different magnetic properties than the Bunte Breccia basement clasts with similar lithology. Two basement blocks situated near the inner ring may have been thermally overprinted up to 550°C.

Shear strength and modulus of mine waste rock – Large scale laboratory testing results

This paper presents the sampling and laboratory testing results of mine waste rock consisting of limestone, siltstone, and intrusive materials collected from the Ok Tedi open pit mine in Papua New Guinea. The laboratory tests included specific gravity measurements, index testing, large-scale direct shear tests using a 720 mm square direct shear apparatus, large-scale consolidation tests using a 550 mm diameter consolidation apparatus, and shear wave velocity tests conducted on compressed waste rock samples. The obtained strength values, as well as small and larger strain modulus values, were subsequently compared with existing literature data from the literature. These findings can serve as a valuable reference for mine waste materials with similar lithology, particle size distribution, and stress condition, particularly in the context of static and seismic slope stability designs.

Two‐phase flow behavior in CO2 geological storage considering spatial parameter heterogeneity

AbstractSaline aquifer rocks exhibit significant spatial randomness due to geological sedimentation processes. To address the issue of the heterogeneity of rock formations in numerical simulations, it is common practice to homogenize rock layers with similar lithologies. However, the acceptability of the errors generated during homogenized computations is a major concern and should be investigated. Therefore, to study the influence of heterogeneity at the storage site on the CO2 migration behavior, the Monte Carlo simulation–random finite element method (MCS‐RFEM) was combined with a CO2 two‐phase flow model to compare the effects of the coefficient of variation (Cv) and correlation length (λx) of random reservoir permeability fields on the migration distance and extent of CO2 storage under the same mean conditions. The results showed that higher Cv and λx values significantly reduced the CO2 migration distance while increasing the spread extent. Compared to the homogeneous model, at a λx value of 100 m, the CO2 migration distance decreased by 5.05%, while the profile sweep area increased by 6.20%. Concurrently, with increasing Cv, the area with a CO2 volume fraction higher than 0.75 decreased by 20.22%, while an increase in λx resulted in a 42.35% increase in the area with a CO2 volume fraction higher than 0.75. Therefore, reservoirs with high Cv and low λx values are more suitable for safely storing CO2. © 2023 Society of Chemical Industry and John Wiley &amp; Sons, Ltd.

Grain-size variability in debris flows of different runout lengths, Wenchuan, China

Debris-flow grain-size distributions (GSDs) control runout length and mobility. Wide, bimodal GSDs and those containing a higher proportion of silt and clay have been shown experimentally to increase runout length. However, the relationship between grain size and mobility has not been well established in field conditions. Here, we compared the grain-size characteristics of two debris flows with considerably different runout lengths (1.5 km vs. 8 km) to understand the role of grain size in governing runout. The two debris flows were triggered in the same rainfall event from coseismic landslide debris generated in the 2008 Wenchuan earthquake in catchments with similar lithology and topography. We compared the deposited GSDs and their spatial patterns using our rare, three-dimensional GSD datasets. Surprisingly, the proportions of each size fraction deposited by the two flows were statistically indistinguishable. The spatial pattern of grain size differed between the two flows, with evidence of inverse grading only preserved in the smaller deposit. From these observations, we can infer that the GSDs of both flows were determined by the coseismic landslide source material, and that there was little difference in the GSDs of material entrained as the flows bulked. The contrasting spatial distributions of grains indicated that different internal processes were dominant within the two flows. These findings demonstrate that where GSDs are dominated by coarse grains and are governed by similar source conditions, grain size plays a lesser role relative to sediment supply and hydrology in controlling the runout length of large catastrophic post-earthquake debris flows.

Geochemistry of Hindoli Group Metasediments, SE Aravalli Craton, NW India: Implications on Provenance Characteristics and Tectonic Setting

Abstract The NE-SW trending Jahazpur Belt in NW India has been considered correlative with the Aravalli Fold Belt, based on lithological similarities and greenschist facies metamorphic assemblages. The 2.54 Ga ‘Jahazpur Granite’ constitutes the basement for the overlying Hindoli and Jahazpur Group sediments in this belt. These meta sedimentary sequences presently occur as a greenschist facies ensemble of phyllite, marble, greywacke, and meta-conglomerate. In this study, the trace and Rare Earth Elements geochemistry of the Paleoproterozoic Hindoli Group metapelites and metagreywackes was evaluated for source characterization and tectonic setting. The transition metals and Th, La abundances, and Th/Sc, Zr/Sc and La/Sc ratios (1.19 and 1.5, 21.31 and 17.35 and 4.02 and 2.97, for metapelites and metagreywackes, respectively) of Hindoli Group suggest a felsic source for them and some degree of sediment maturity. Both Hindoli metapelites and metagreywackes are enriched in LREE and display significant negative Eu anomalies, further substantiating a predominant felsic component in the source region. The provenance modeling calculations indicate that the detritus was mainly sourced from Mangalwar Complex, along with some inputs from Jahazpur Granite, Bundelkhand TTG and Hindoli volcanics. Geochemical characteristics also discriminate a continental collision associated with an Active Continental Margin tectonic setting for the deposition of Hindoli sediments.