Sedimentary Rocks Research Articles

Capillary pinning in sedimentary rocks for CO2 storage: Mechanisms, terminology and State-of-the-Art

Capillary pinning in sedimentary rocks for CO2 storage: Mechanisms, terminology and State-of-the-Art

Experimental investigation on the failure mechanism of water-bearing sedimentary rocks under true-triaxial stress

Experimental investigation on the failure mechanism of water-bearing sedimentary rocks under true-triaxial stress

Automated thermo-hydro-mechanical simulations capturing glacial cycle effects on nuclear waste repositories in clay rock

To assess the present and future conditions of potential deep geological repository sites, understanding their evolution in the past is mandatory. Here, glaciation cycles strongly affected the long-term thermo-hydro-mechanical (THM) evolution of the geosystem. The AREHS project studied the effects of changing boundary conditions (BCs) on the long-term evolution of large-scale hydrogeological systems. The focus is on numerical modeling the far-field using the open-source multi-field finite element code OpenGeoSys with full THM coupling. The impact of the glacial THM loading is taken into account using complex time-dependent THM BCs. In the present study, a generic geological model for a clay host rock formation including predominantly sedimentary rock layers is applied. The elasto-plastic behavior of all the layers is described with the Modified Cam clay model. Thus, a range of relevant effects (dilatancy, contractancy, consolidation etc.) can be considered with few material parameters. Special emphasis is put on the specification of a suitable initial state: To this end, an initial simulation is carried out, where a reasonable plastic pre-consolidation is adjusted. Then, the thermodynamic state is transferred in full to the subsequent 2D simulation of two glacial cycles. As a main result, the glacial cycles lead to persistent deviations in the subsurface, e.g. long-term pressure anomalies. Large glacial over- and underpressure cells disturb the in-situ hydraulic gradients and alter the flow fields around the DGR. As the host rock horizons represent aquitard layers they prevent periglacial circulation flow. No dilatant deformation was observed in this study. Contractant plastic deformation in combination with the HM coupling plays an important role as it significantly increases pore pressure peaks during glacial transit.

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.

The timing and significance of mid-crustal shearing and exhumation of amphibolite-facies rocks along the Great Glen Fault Zone, Scotland

The Rosemarkie Inlier lies on the NW side of the Great Glen Fault Zone (GGFZ) and is composed of foliated and lineated Archean orthogneisses and Moine metasedimentary rocks. The mylonitic foliation strikes NE–SW (parallel to the GGFZ), dips steeply SE and contains a gently to moderately plunging mineral lineation. Microstructural and quartz c -axis fabric analyses indicate that oblique sinistral shearing occurred under amphibolite-facies conditions. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analyses on monazite rims in the gneisses yielded 206 Pb/ 238 U ages of 401.8 ± 4.8 Ma (including 2 σ uncertainty and a propagated additional 1% external uncertainty). Similar deformation and recrystallization temperatures indicated by quartz fabrics (610°C) and monazite–xenotime thermometry (616 ± 25°C), respectively, in the gneisses suggest that ductile sinistral shearing was ongoing at c . 402 Ma. The c . 402 Ma rim age is the youngest monazite age recorded in the Northern Highland Terrane (NHT) and indicates that sinistral shearing at mid-crustal levels was ongoing along the GGFZ in Lower Devonian (Emsian, 407–393 Ma) times when the thrust sheets of the NHT to the NW had already been exhumed. The Rosemarkie basement rocks are unconformably overlain by Middle Devonian (Eifelian, 393–387 Ma) sedimentary rocks, indicating time-averaged exhumation rates of c . 1.75 mm a −1 between 402 and c . 390 Ma, assuming a geothermal gradient of 30°C km −1 .

Ensemble Algorithms for Prediction of Ripping Production in Sedimentary Rocks

Ensemble Algorithms for Prediction of Ripping Production in Sedimentary Rocks

A New Approach for Calculating Texture Coefficients of Different Rocks With Image Segmentation and Image Processing Techniques.

The texture coefficient (TC) is a critical parameter used to analyze the microstructural characteristics of rocks and predict their mechanical behavior. In recent years, various computational programs and software have been employed to estimate the TC values of rocks. However, existing methods remain insufficient and time-consuming for accurately determining rock TCs. In this study, thin-section images of 20 different igneous, metamorphic, and sedimentary rocks were acquired and segmented to calculate TC values using a novel approach. The computation process was implemented using Python-based software that integrates segmentation and image processing techniques to determine TC values. The thin-section images were segmented utilizing a deep learning-based image processing technique, and a Python-based algorithm was developed for TC calculations. The proposed method offers a unique approach to TC estimation in rocks, achieving a high segmentation accuracy (IoU = 0.97). Furthermore, with this method, the TC value of any given rock can be computed in approximately 1 min.

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.

Characterising Stiffness Properties of Bedding Parallel Fractures at High Normal Stresses for Sedimentary Rocks

Abstract The shear and normal stiffness of fractures are important parameters governing deformation behaviour of sedimentary rocks. However, shear stiffness is challenging to measure and is often inadequately applied in geotechnical design. Shear stiffness is frequently estimated without testing, instead based on assumptions and represented by a single value, despite the knowledge it should be represented as a function to capture variability. Most published stiffness data for sedimentary rocks are for joints at low normal stresses, with limited data for bedding parallel fractures at normal stresses above 1 MPa. This paper addresses this gap by presenting 55 shear stiffness results for bedding parallel fractures, tested under applied effective normal stresses ranging from 1 to 15 MPa. Results show a strong correlation between applied normal stress and shear stiffness, with shear stiffness increasing as normal stress increases. The results are then used to determine the suitability of current shear stiffness estimation methods. The findings highlight the need for significant improvement in current shear stiffness guidelines and emphasise the need for guidelines to better account for system influence with data processing protocols incorporating actual intact data and using displacement for determining the seating influence cut-off. Additionally, the common practice of using normal-to-shear stiffness ratios for estimates should be discontinued, as it is unsupported by data. Furthermore, predictions demonstrate the impact shear stiffness has on depth of fracture, supporting the necessity of representing stiffness as a function rather than a single value.

Potassium Isotope Ratios (δ41K) of Eighteen Chinese Rock Reference Materials

Potassium isotope ratios (δ41K) were determined for eighteen Chinese geological reference materials (RMs, GSR series) encompassing igneous, metamorphic and sedimentary rocks. K2O mass fractions (w) ranged between 0.15 and 7.5% in these RMs. Measurements were conducted using a collision cell MC‐ICP‐MS with sample‐standard bracketing technique. The intermediate precision of K isotopic determination, based on measurement results collected over 2.5 years, was 0.04‰ (2s, n = 69) for in‐house GSB K solution and 0.05‰ (2s, n = 63) for basaltic RM BCR‐2. The accuracy of our data was assessed by comparison with previously published data and/or utilising two or three different measurement procedures. The high‐precision δ41K values for these eighteen RMs span a wide range from ‐1.15‰ (GBW07122, GSR 15, amphibolite) to 0.28‰ (GBW07120, GSR 13, limestone), and data for six RM are presented for the first time, making them valuable references for quality assurance and inter‐laboratory comparisons.

New taxa of dinoflagellate cysts from the Upper Cretaceous to Paleocene strata of Bylot Island, eastern Nunavut, Canada

ABSTRACT The Upper Cretaceous to Paleocene strata of Bylot Island, eastern Nunavut, Canada, include marine and terrestrial sedimentary rocks with rich palynomorph assemblages that are valuable in determining the stratigraphy and palaeoenvironments of the region. The assemblages contain biostratigraphically important new taxa, including one new genus and 15 new species of dinoflagellate cysts. The genus is Deltiella; the species are Alterbidinium punctatum, Chlamydophorella ejuncida, Deltiella punctata, Elytrocysta vermiculata, Exochosphaeridium gracile, Gillinia dentata, Gillinia umbraculum, Hystrichosphaeridium procerum, Hystrichosphaeridium prolatum, Microdinium scutella, Microdinium sinuatus, Odontochitina camura, Odontochitina corpucorna, Odontochitina? pilata, and Spiniferella granulata. The restricted stratigraphic ranges of the species have enabled more precise dating of the Cretaceous to Paleocene strata in the eleven surface sections studied. Individual taxa may reflect specific palaeoclimatic settings: for example, Deltiella and some species of Odontochitina may indicate cooler climatic conditions.

Carbon Isotope and Sterane Records of Biological Diversity in the Fortunian Stage of the Early Cambrian Tarim Basin, Northwest China

Carbon isotope of the kerogen (δ13Corg), steranes/hopanes (S/H), and C28/C29 sterane ratios in the source rocks from the SARK section at the Early Cambrian Yurtus Formation in the Fortunian Stage in the Tarim Basin of Northwest China reveal a positive excursion that is associated with biological diversity. The enrichment of vanadium/(vanadium + nickel) (V/(V + Ni)) ratios (0.64~0.99, averaging 0.87) for the Yurtus Formation of the Fortunian Stage provide evidence for predominant anoxic bottom water conditions. A sharply decreased V/(V + Ni) ratio in the middle Yurtus Formation suggests enhanced oxygen content of the water column in this interval. However, the total organic carbon (TOC) values in the sedimentary rocks show a marked increase in the middle Yurtus Formation, which is due to the enhanced productivity suggested by a positive δ13Corg increase of ~2.0‰ and enhanced S/H and C28/C29 sterane ratios. We suggest that the enhanced oxygen content may have contributed to the biological diversity during the Fortunian Stage in the Tarim Basin. The δ13Corg excursion first reported here associated with biological diversity can be correlated with that in South China and possibly elsewhere in this interval.

Mechanisms of global climate change during the five major mass extinctions

Since the emergence of diverse animal phyla around 500 million years ago, five major mass extinction events have occurred, each coinciding with abnormal climate changes. We analyzed sedimentary organic molecules from the first and least understood extinction event at the end of the Ordovician period. We divided all five major extinctions into two phases each, totaling ten events, and examined the relationship between climate shifts and the “coronene index”—an indicator of heating temperatures in sedimentary rocks caused by volcanic activity or meteorite impacts. As a result, we found that four of the five extinctions began with global cooling and ended with warming, while one started with an unknown anomaly and also ended with warming. During the initial extinction phases, two events showed low-temperature heating, two high-temperature, and one moderate-temperature. All subsequent warming phases showed moderate-temperature heating. These findings suggest that large-scale volcanic eruptions and meteorite impacts heated sulfides, sulfates, and hydrocarbons at varying temperatures, releasing SO2 or soot into the stratosphere, blocking sunlight, and triggering global cooling and extinction. This was followed by moderate heating of hydrocarbons and carbonates, increasing CO2 emissions and driving long-term global warming, leading to secondary extinction events.

Identifying the Key Control Factors of Deep Marine Shale Gas Reservoirs: A Case Study on Lower Cambrian Fine-Grained Sedimentary Rocks in Cen Gong, Guizhou, China

This study identifies the following three key factors controlling shale gas reservoirs in the lower Cambrian Niutitang Formation, northern Guizhou, China: sedimentary features, diagenetic modification, and stable tectonic conditions. This research addresses gaps in previous studies by investigating how tectonic and diagenetic conditions contribute to the unique characteristics of shale gas enrichment in tectonically complex areas with high thermal maturity (Ro > 2.5%). Sedimentary conditions revealed a positive correlation between total organic carbon (TOC) content and gas adsorption capacity, with higher TOC enhancing adsorption. Experimental data indicate that the TOC content (2.33%–9.07%) significantly correlates with methane adsorption capacity (Langmuir volume VL = 1.87–8.78 cm3/g at 30 °C and 10 MPa), as evidenced by the linear relationship between TOC and VL in shale samples. Clay mineral content exhibited a dual role as moderate levels (15%–25%) improved adsorption, while excessive amounts (>30%) reduced efficiency due to pore occlusion. Diagenesis, including compaction, cementation, and thermal evolution of organic matter, significantly reshaped reservoir porosity. Quantitative analysis of core samples demonstrates that compaction caused a porosity reduction of 18%–25% in samples with burial depths exceeding 1500 m, thereby influencing gas retention capacity. The reservoir has entered the anchizone (average vitrinite reflectance Ro = 2.54%), characterized by advanced organic matter maturation and widespread organic porosity development. Tectonic activity was critical for gas retention; intense tectonic activity led to shallower burial depths and gas loss, whereas structurally stable areas favored preservation. This study emphasizes the significance of tectonic conditions and their role in maintaining gas reservoirs in the anchizone, reconciling discrepancies in gas storage mechanisms observed in basins with similar TOC and thermal maturity. In summary, deep marine shale gas enrichment relies on the synergistic effects of high-quality sedimentary foundations (TOC > 4%, quartz > 30%), diagenetic evolution optimizing pore structures, and stable tectonic conditions ensuring gas retention. These findings provide new insights into the exploration of shale gas in complex tectonic regions and offer a framework for improving prediction models in shale gas enrichment by integrating micro-scale organic–inorganic interactions with macro-scale tectonic controls.

Thermochronological constraints for reconstructing the tectonic history of the northern Central Cordillera (Serranía de San Lucas), Colombia

The Northern Andes are characterized by episodes of exhumation at around 80, 60–50, 40, 25 and 15–0 Ma in the Central and Eastern Cordilleras, Santander Massif, Sierra Nevada de Santa Marta and Merída Andes. Here we present a preliminary set of low-temperature thermochronological data from the Serranía de San Lucas in the northern Central Cordillera, which demonstrate that the timing of exhumation of this region is different from that of the surrounding massifs such as the Antioquia batholith, the Santander Massif or the Sierra Nevada de Santa Marta. The thermochronological data show that the volcanic rocks of the Early Jurassic Noreán Formation exposed in the Serranía de San Lucas to the west of the Middle Magdalena River basin and the northern Santander Massif were buried beneath 6–7 km of Upper Jurassic to Upper Cretaceous/Paleocene sedimentary rocks, then slow erosional exhumation resumed at about 80–60 Ma as reflected by slow cooling rates of 2–4°C/myr. No evidence is found for exhumation at 25 Ma as it has been previously detected in the Antioquia batholith or the Santander Massif. The Serranía de San Lucas tectonic evolution is seen in connection with Mid-Late Jurassic to Early Cretaceous extension and Late Cretaceous compression and accretion of oceanic blocks to the western margin of the South American plate, and flat slab subduction of the Caribbean plate during the Eocene–Oligocene.

A story of lithospheric plates

A story of lithospheric plates Whether plate tectonics began 850 million years ago or earlier is uncertain. FINGER-PT hypothesises that preservation bias obscures evidence of earlier modern-like tectonics. To test this, the project analyses detrital minerals in sedimentary rocks, employing experimental petrology, elastic barometry, and geochemistry to uncover when tectonic processes as we know them began.

The Identification of Exposed Beachrocks on South China Sea Islands Based on UAV Images

Beachrocks are common coastal sedimentary rocks in tropical and subtropical seas. They are widely spread especially in islands and coastal areas. These rocks are important for island geological evolution research. Research on beachrocks aids in protecting island ecosystems and enhances islands’ ability to prevent and mitigate damage from natural disasters. This study uses unmanned aerial vehicle (UAV) images and the U-Net model based on deep learning to identify beachrocks. To enhance identification accuracy, the efficient channel attention (ECA) mechanism was integrated, leading to improvements of 0.49% in overall accuracy, 1.41% in precision, 0.97% in recall, 1.10% in F1-score, and 2.09% in intersection over union (IoU) compared to the baseline U-Net model. The final results demonstrate that the model effectively identified beachrocks, achieving 97.47% accuracy, 93.27% precision, 94.73% recall, 93.95% F1-score, and 88.65% IoU. This study offers a valuable tool for island geological evolution research and supports the development of large-scale island conservation efforts.

Factors influencing landslide occurrence in low-relief formerly glaciated landscapes: landslide inventory and susceptibility analysis in Minnesota, USA

Abstract In landscapes recently impacted by continental glaciation, landslides may occur where topographic relief has been generated by the drainage of glacial lakes and ensuing post-glacial fluvial network development into unconsolidated glacially derived sediments and exhumed bedrock. To investigate linkages among environmental variables, post-glacial landscape development, and landslides, we created a landslide inventory of nearly 10,000 landslides in five regions of the formerly glaciated low-relief state of Minnesota, United States. Multivariate logistic regression indicates the importance of slope angle, lithology, and the development of stream valleys to landslide distribution. Areas underlain by fine-grained glaciolacustrine and nearshore deposits that are incised by streams are particularly prone to shallow (< 1–2 m depth) landslides. Landslides also occur in a wide range of glacial and fluvial deposits, and as rockfall in layered Paleozoic sedimentary rocks in central and southern Minnesota and Precambrian igneous and sedimentary rocks in northeastern Minnesota. Although no more than 1–2% of the studied regions are susceptible to landslides, they can pose risk to life and safety, damage infrastructure, and impact water quality. The combination of recently generated low-relief steep slopes, extensive unconsolidated sediments, and layered sedimentary bedrock make this formerly glaciated landscape more susceptible to landslides than current national-scale models indicate.

Mineralogical and Geochemical Compositions of Sedimentary Rocks in the Gosau Group (Late Cretaceous), Grünbach–Neue Welt Area, Austria

Sedimentary rocks of the Gosau Group in the Grünbach–Neue Welt area (Eastern Alps, Austria) were analyzed to determine their mineralogical and geochemical compositions. This study includes the following: (1) the identification of major minerals using X-ray diffraction (XRD), (2) the analysis of major, minor, and trace elements via X-ray fluorescence spectroscopy (XRF) and inductively coupled plasma mass spectrometry (ICP-MS), and (3) the quantification of total organic carbon (TOC), total nitrogen (TN), and total sulfur (TS) using an Elementar Unicube analyzer. Samples were collected from four artificial trenches and one outcrop in Maiersdorf, spanning the Grünbach and Piesting formations deposited during a terrestrial-to-marine transition in the upper Santonian to Campanian (Late Cretaceous). The dominant minerals—quartz, muscovite, illite, and calcite—exhibit relative abundances corresponding with variations in major oxide concentrations. Minor elements show variability but generally follow consistent trends. Trace and rare earth elements display greater variability but similar patterns, with a broader distribution in the Grünbach Formation. Elevated TOC, TN, and TS values are observed near the formation boundary and in the Piesting formation. These results offer the mineralogical and geochemical characterization of the strata, and lay a foundation for further investigations into the paleoenvironmental and basin evolution of the Gosau Group in the region, providing a comparative framework for Gosau basins across the Eastern Alps.

Empirical relationship between the Geological Strength Index (GSI) and rock mass quality (Q-system) in granite and sedimentary rocks

This paper presents the relationship between Rock Mass Quality (Q-system) and the Geological Strength Index (GSI) parameters. Equations are suggested based on field data and calculations of the empirical results of granitic rock masses (Hungary) and siltstones, sandstones and quartzite formations (Australia). Measured and calculated GSI values vs Q values are given for granitic rocks, showing a higher correlation than that of the sedimentary rocks of Australia. The different behaviors of rock masses explain the higher correlation between GSI vs Q and GSI chart vs GSI calculated for igneous rock bodies. Despite the differences in stress fields and the highly tectonised structural geological setting of the granitic rock mass, the isotropic nature of granitic rocks vs. anisotropy of sedimentary rock bodies is reflected in the correlation coefficients.