Lithological Composition Research Articles

Geological characteristics and major factors controlling the high yield of tight oil in the Da’anzhai member of the western Gongshanmiao in the central Sichuan basin, China

The Da’anzhai Member limestone in the central Sichuan Basin holds significant importance as a tight oil-producing formation. Despite its crucial role, the intricate patterns of hydrocarbon enrichment and the elusive geological factors dictating high-yield production have impeded tight oil exploration and development in the Sichuan Basin. This study delves into the geological characteristics of tight oil and identifies key factors influencing high-yield production, utilizing comprehensive data derived from cores, thin sections, well logging, seismic studies, and production tests of the Da’anzhai Member in the western Gongshanmiao within the central Sichuan Basin. Our findings reveal that the primary productive strata for tight oil are the Da 1 (1st Submember of the Da’anzhai Member) and Da 3 (3rd Submember of the Da’anzhai Member) Submembers, characterized by high-energy and low-energy shell beach microfacies. The kerogen type is sapropelic, ranging from mature to highly mature, positioning it as a moderately good hydrocarbon source rock. The predominant lithology of the reservoir consists of coquina and argillaceous coquina, with secondary dissolved pores, fractures, and nano-scale micropores serving as the predominant reservoir spaces. The overall lithology represents a dense limestone reservoir of the pore-fracture type, featuring low porosity and permeability. Critical controlling factors for achieving high-yield production of tight oil encompass lithological composition, fracture development, tectonic position, and source-reservoir configuration. Notably, substantial coquina thickness, fracture development, and the strategic relationship between the lower reservoir and upper source rocks contribute significantly to unlocking high tight oil yields. Additionally, thin-layer coquina emerges as a potential area for realizing increased oil and gas production capacity during later stages of development. This comprehensive analysis sheds light on the intricate dynamics governing tight oil production in the Da’anzhai Member, offering valuable insights for advancing exploration and development strategies in the Sichuan Basin.

Plio-Pleistocene drainage reorganization in the middle Yellow River of China, revealed by provenance and paleocurrent analysis of fluvial sediments

Continental-scale drainage reorganization is generally understood to result from landform evolution forced by the coupling between tectonic activity and climate change, attracting worldwide attention. Planation surfaces and river terraces constitute the most direct geomorphological archives for integrating the history of river systems and for reconstructing processes of drainage reorganization based on provenance analysis of the fluvial sediments. The Middle Yellow River has incised into the Ordos Block, which was previously levelled by a planation surface, creating the Jinshaan Gorge and linking the Hetao Basin to the north and the Fenwei Basin to the south. Multiple lines of evidence, from terraces correlation, sedimentary characteristics, and fluvial provenance, suggest that the Middle Yellow River catchment was occupied by fluvio-lacustrine systems before drainage integration, accumulating a sedimentary sequence derived from surrounding Red Clay and bedrocks during the period between 8.3 and 3.7 Ma. The planation surface was uplifted subsequently, forcing reorganization of the fluvio-lacustrine systems. Their integration resulted in the formation of the Jinshaan Gorge prior to 1.2 Ma. Numerous terraces were created during incision by the Middle Yellow River from north to south along the gorge. Our data, obtained from zircon UPb dating and lithological composition of fluvial gravels, further points to a remarkable discrepancy in provenance between the fluvio-lacustrine systems overlying the planation surface and the terraces sequence formed by the integrated Middle Yellow River, confirming the drainage reorganization process constrained by the geomorphic records.

Hydromechanical simulation of a carbonate petroleum reservoir using pseudo-coupling

In the domain of petroleum reservoir management, numerical flow simulation stands as the primary tool for prediction and control. Traditionally, rock compressibility has been the key geomechanical parameter, often applied as a single, unchanging value across the entire reservoir model throughout the simulation. This study introduces a novel methodology that enhances reservoir simulation accuracy by incorporating rock mechanical behavior through a pseudo-coupling approach, without increasing computational costs. This approach empowers reservoir engineers to consider rock hydromechanical behavior in daily reservoir studies.The pseudo-coupling updates both porosity and permeability based on tables that correlate pore pressure to porosity and permeability multipliers, thereby replacing the conventional reliance on compressibility. It begins with reservoir-rock samples selection guided by lithological composition, followed by mechanical and hydromechanical laboratory tests, and numerical adjustments with ABAQUS stress analysis software. The resulting mechanical parameters serve for generating pseudo-coupling tables tailored to each facies.Validation experiments comparing pseudo-coupling simulations with conventional and fully coupled models reveal convergence in porosity and permeability variations with pore pressure between both coupled approaches. Extensive assessments further compare pseudo-coupling simulations against conventional reservoir simulations using a synthetic model based on a carbonate post-salt reservoir, denoted as Field B. The pseudo-coupling approach emerges as a more robust model capable of discerning preferential flow paths, all while maintaining computational efficiency. Moreover, these preferential flow paths were also predicted by the reservoir team responsible for the field development, but through a trial-and-error procedure to match production history, whilst the pseudo-coupling predicted it based on rock mechanical behavior.In this way, the proposed methodology enables an enhancement in the accuracy and efficiency of petroleum reservoir management by considering geomechanical effects, without incurring any additional computational costs when compared to conventional reservoir simulation.

Hydrogeochemistry of the shallow aquifer in the western Po Plain (Piedmont, Italy): spatial and temporal variability

ABSTRACT This paper describes the spatial and temporal variability of the hydrogeochemistry of shallow aquifer in the western Po Plains, located in Piedmont (northwestern Italy), using groundwater monitoring network data for the main chemical–physical parameters. Hydrochemical maps for the 2015–2020 period were created to identify the main natural and anthropogenic factors responsible for the remarkable spatial variability. Temporal variations in the 2000–2020 period were defined to show the existence of variabilities that were previously not investigated. The spatial and temporal elaborations show significant and various variabilities. The hydrochemical maps confirm the existence of several natural and anthropogenic factors, including the lithological compositions of aquifers, agricultural practices and pressure from urban centres. The temporal variations suggest different resilience capacities of the aquifers to the several impacting factors. The availability of this knowledge is crucial to create the basis for groundwater protection.

Electrical facies of the Asmari Formation in the Mansouri oilfield, an application of multi-resolution graph-based and artificial neural network clustering methods

Electrofacies analysis conducted the distribution effects throughout the reservoir despite the difficulty of characterizing stratigraphic relationships. Clustering methods quantitatively define the reservoir zone from non-reservoir considering electrofacies. Asmari Formation is the most significant reservoir of the Mansouri oilfield in SW Iran, generally composed of carbonate and sandstone layers. The stratigraphical study is determined by employing 250 core samples from one exploratory well in the studied field. Five zones with the best reservoir quality in zones 3 and 5 containing sandstone/shale are determined. Moreover, multi-resolution graph-based and artificial neural network clustering involving six logs are employed. Utilizing Geolog software, an optimal model with eight clusters with better rock separation is obtained. Eventually, five electrofacies with different lithological compositions and reservoir conditions are identified and based on lithofacies describing thin sections, sandstone, and shale in zones 3 and 5 show high reservoir quality. According to the depth related to these zones, most of the facies that exist in these depths include sandstone and dolomite facies, and this is affected by the two factors of the primary sedimentary texture and the effect of the diagenesis process on them. Results can compared to the clustering zone determination in other nearby sandstone reservoirs without cores.

Nd isotope systematics of Late Paleozoic granitoids from the Western Transbaikalia (Russia): Petrological consequences and plume model testing

Late Paleozoic granites of the Angara-Vitim batholith (AVB) occupy an area of 200,000 km2 in Western Transbaikalia (the eastern part of the Central Asian fold belt). Batholith granitoids form a sheet-like body with an average thickness of 7–10 km and a volume of about 1 million km3. The granitoid massifs that make up the batholith are composed of high-potassium calc-alkaline and subalkaline quartz monzonites, quartz syenites, amphibole-biotite granodiorites, and biotite granites of autochthonous and allochthonous facies. An extremely high heterogeneity of the batholith isotopic structure was established, which basically corresponds to the parameters of uneven-aged crustal metaterrigenous protoliths. There are significant variations in εNd(Т) and accordingly T(DM-2) in granitoids of different complexes. It is assumed that the isotopic heterogeneity of AVB was formed due to the melting of a limited protoliths number that are maximally contrasting in isotopic and lithological composition: the Paleoproterozoic continental crust with εNd(Т) ≈ -20 ÷ -22 and T(DM-2) = 2.9–2.5 Ga and Neoproterozoic mafic granulites of increased potassium alkalinity, enriched in the juvenile component (εNd(Т) ≈ -3.0; T(DM-2) = 1.2–1.3 Ga). The latter were the main magmas source of postbatholitic alkali granites. Melts from these contrasting protoliths were only in some cases complementary to the salic melts sources. The main mechanism that determined the isotopic composition of AVB granitoids was the mixing of isotopically contrasting magmas in different proportions. Mingling dikes, mafic inclusions in granitoids, and synplutonic mafic intrusions in the AVB indicate an additional mixing component. It was mafic magma from an enriched mantle reactivated in the Late Paleozoic under the mantle plume influence on the heated plastic crust of a young (Hercynian) orogen.

Transformation of the Geological Environment under the Influence of Liquid Radioactive Waste (Russian Experience in Studying Historical Nuclear Disposal)

Due to various historical events, in the Russian Federation, in addition to the radioactive waste storage facilities used in world practice, there are various nuclear and radiation hazardous facilities that require special procedures for monitoring and decommissioning. One of these facilities is the disposal site for LRW on the territory of the JSC Siberian Chemical Plant, where specially prepared waste is injected into sand reservoirs lying at depths of 300–350 m between clayey strata. This study examines in detail the features of the lithological and mineral composition of reservoir sands and aquitards. The processes of environmental transformation in reservoir sands, which lead to changes in the composition and structure of rocks, were characterized. These processes manifest themselves in the form of the development of leaching zones and their “healing” with newly formed smectite, the destruction of terrigenous grains, including the development of cracks, and the growth of newly formed smectite in the pore space of reservoirs. The forms of occurrence and localization of authigenic smectite formed as a result of technogenic impact are described. It has been shown that, despite the obvious impact of highly reactive solutions accompanying liquid radioactive waste, the insulating properties of the geological environment are maintained and even improved to some extent.

Geological and hydrogeological structure of the Sheshma terrigenous complex of the Belsky uplift

Relevance. The importance of industrial and technical water supply to an oil field in the north-east of Perm region. The requirements to subsoil use and environment protection demand a sanitary restriction zone of the water supply source in the northern part of the field. The current study of a geological structure and groundwater conditions and circulation of Sheshma aquifer complex will assess its resources and elaborate on organization of water supply to the oil field. Aim. To study geological structure and groundwater conditions of Sheshma aquifer complex. Objects. Formations rocks and groundwater conditions of Sheshma terrigenous complex. Methods. Studying the archival records, conducting a hydro-geological survey of the territory, drilling groundwater exploration wells, conducting pilot-filtration works on groundwater exploration wells in the flooding and low-water period. Results. The authors have discovered Sheshma formation thickness, which ranges from 100–150 to 300 m, and lithological composition of rocks and groundwater conditions of Sheshma aquifer complex. It was established that groundwater is deposited as a system of separate isolated water-bearing interlayers and blocks within the Durinsky trough. The most water-bearing zones were identified. Two aquifers of fine-grained and coarse-grained sandstones were detected in low-permeability thickness of Sheshma formation. The aquifers are not hydraulically connected and are separated from each other by a 40 m thick layer of water-resistant mudstones. Groundwater is deposited as strata with Neumann's boundary conditions, orientated sublatitudinally, from west to east. The obtained data can be further used to solve the issues of water supply within the area under study and the rational use of these waters.

Reservoir-triggered seismicity: case study of the Dnister Hydro Power Complex (Ukraine)

The work considers the seismic activity around the Dnister Hydro Power Complex in the Dnister Reservoir area from 2012 to 2021. Maximum local magnitude of earthquakes for the studied period is ML=3.4. Hypocenters of earthquakes are at the depth of 1—3 km. They are located nearby to previously established faults and contacts of structures with a different lithological composition. Artificial water level regulation in the reservoir is related to the operation of the Dnister Hydro Power Plant and, according to our results, probably affects the occurrence of seismic events. Although the maximum water level changes only by 8.7 m, the region has increased natural seismicity and is located in the transition zone between 6th and 7th isoseims according to the seismic zoning map of Ukraine. Accumulated natural stresses can be triggered into earthquakes when there is a sudden change in water pressure. The seismicity of the region around the Dnister Reservoir was investigated for 10 years, taking into account the water level data in the reservoir, as well as comparing the location of earthquakes with the State Geological Map of the Crystalline Foundation. The profile of the State Geological Map of the Crystalline Foundation with the projected earthquakes hypocenters allowed to indicate that a significant number of earthquakes are located between different lithological structures. In order to assess the interrelationship between seismicity and water level changes in the reservoir, 111 periods of lowering or filling of the reservoir were selected. Parameters of seismic activity within the periods were calculated and analysed. Correlation between the sum of logarithms of energy with water volume changes and pressure changes in the Dnister Reservoir was established. Considering linear dependence it is possible to predict potential intensity of local seismicity caused by water level changes in the Dnister Reservoir.

Employing Statistical Algorithms and Clustering Techniques to Assess Lithological Facies for Identifying Optimal Reservoir Rocks: A Case Study of the Mansouri Oilfields, SW Iran

The crucial parameters influencing drilling operations, reservoir production behavior, and well completion are lithology and reservoir rock. This study identified optimal reservoir rocks and facies in 280 core samples from a drilled well in the Asmari reservoir of the Mansouri field in SW Iran to determine the number of hydraulic flow units. Reservoir samples were prepared, and their porosity and permeability were determined by measuring devices. The flow zone index (FZI) was calculated for each sample using MATLAB software; then, a histogram analysis was performed on the logarithmic data of the FZI, and the number of hydraulic flow units was determined based on the obtained normal distributions. Electrical facies were determined based on artificial neural network (ANN) and multi-resolution graph-based clustering (MRGC) approaches. Five electrical facies with dissimilar reservoir conditions and lithological compositions were ultimately specified. Based on described lithofacies, shale and sandstone in zones three and five demonstrated elevated reservoir quality. This study aimed to determine the Asmari reservoir’s porous medium’s flowing fluid according to the C-mean fuzzy logic method. Furthermore, the third and fourth flow units in the Asmari Formation have the best flow units with high reservoir quality and permeability due to determining the siliceous–clastic facies of the rock units and log data. Outcomes could be corresponded to the flow unit determination in further nearby wellbores without cores.

Preliminary Assessment of Geohazards’ Impacts on Geodiversity in the Kratovska Reka Catchment (North Macedonia)

This comprehensive study investigates the intricate interplay between geodiversity, geohazards, and anthropogenic influences within the Kratovska Reka catchment—an area distinguished by its remarkable geosites. Kratovska Reka, spanning a length of 17.3 km, serves as the left tributary to Kriva Reka. The watershed of Kratovska Reka, covering an area of 68.5 km2, is situated on the northwestern inclines of the Osogovo Mts in North Macedonia. Despite harboring exceptional geodiversity, the area lacks protective measures for its myriad geosites. Evaluating susceptibility to geohazards, including excessive erosion, landslides, and flash floods, this research identifies heightened risk zones, particularly in the valley of Kratovska Reka and its tributaries. A multi-hazard model reveals that 56.07% of the basin is vulnerable to geohazards. The study correlates lithological composition, relief features, and morphometric characteristics with geohazards, emphasizing the significance of paleovolcanic relief in resisting excessive erosion. Human-induced factors, notably deforestation and inappropriate land use, amplify geohazards. This research underscores the urgent need for geosite protection and sustainable land management to mitigate geohazards’ impacts. Additionally, it explores the correlation between land use practices and geodiversity, emphasizing the importance of responsible land management in safeguarding the geological and geomorphological values of the researched area.

ELEMENTAL COMPOSITION OF BOTTOM SEDIMENTS AND PERMAFROST DEPOSITS FROM THE BUOR-KHAYA BAY (LAPTEV SEA)

The paper summarizes data on the lithological and elemental composition of bottom sediments and permafrost from boreholes 1D-14, 3D-14 and 1D-15 drilled in Buor-Khaya Bay in 2014-2015. Based on the results of determining the percentage content of SiO2, Al2O3, Fe2O3, TiO2, MgO, Na2O, K2O, CaO, MnO, P2O5, Cl, Cr, S, Ni, Cu, Zn, Rb, Sr, Ba, Y, Zr, organic carbon in sediments, lithochemical modules values were calculated and comparative analysis of the lithological and geochemical composition was performed. Principal differences between near-continental (1D-14 and 3D-14) and relatively distant from land (1D-15) strata were established, which is explained by spatial and temporal variability in sedimentary fluxes and weathering crust activity in the studied area of the Laptev Sea. The results of the study allowed to conclude that the basis of the petrofund of the studied deposits are most likely sedimentary rocks of the Kharaulakh ridge of the Verkhoyansk mountain system (sandstones, siltstones and mudstones). The contribution of igneous and metamorphic rocks to the sedimentary supply in the strata uncovered by drilling was insignificant.

QUANTIFICATION OF DIAGENETIC TRANSFORMATIONS IN EOCENE-PLEISTOCENE SEDIMENTS OF THE VøRING PLATEAU (NORWEGIAN SEA) RELATED TO THEIR ENVIRONMENTS

In this article, a univariate regression analysis of Fe, Mn, Mn/Fe and Corg distributions and marine sediment densities by depth in sections of studied boreholes drilled on the Vøring Plateau was used to investigate the intensity of diagenetic transformations. As a result, quantitative parameters of diagenesis processes in Eocene-Pleistocene sediments were obtained. In addition, the degree of intensity of diagenesis processes for the main lithological sediment types of the Vøring Plateau was studied on the basis of single-factor analysis of variance data. As a result, it was found that in addition to hiatuses, the effects of bottom currents and turbidites, the degree of diagenetic transformation in Eocene-Pleistocene sediments depended on the following main factors: sediment accumulation conditions; lithological composition; the amount of organic carbon included in the Eocene-Pleistocene sediments of the Vøring Plateau.

Lithological mapping of charnockites using spectral mixture analysis

Charnockite, an orthopyroxene-bearing granitic rock, is the most dominant rock type of the Southern Granulite Terrain (SGT) of India. This study utilises remote sensing data to map the charnockite lithology in the Kodaikanal region within the SGT. Although remote sensing-based lithological mapping dominantly uses VNIR (Visible-Near Infrared) datasets, in this study, PRISMA (hyperspectral) datasets in the VNIR region and ASTER (multispectral) datasets in the TIR (Thermal Infrared) region were utilised in deriving the mineralogical composition and spectral characteristics of charnockites. In addition, image-derived endmember spectra from PRISMA and ASTER were validated using the laboratory-acquired spectra of charnockites. Linear mixing models (LMM) and the Hapke model were applied to quantitatively study the fractional abundance of charnockite rocks in the Kodaikanal region. Three least square methods, i.e., Fully Constrained Least Squares (FCLS), Non-Negative Least Squares (NNLS), and Unconstrained Least Squares (UCLS), were used to derive the fractional abundance of endmembers. Laboratory-derived charnockite spectra in the VNIR region exhibit spectral features characteristics of pyroxenes and hydrated minerals. In the TIR region, charnockite spectra exhibit characteristic vibrational absorption features of quartz and feldspar known as reststrahlen bands. Image analysis indicates that charnockite rocks exhibit spectral characteristics resembling the mafic rock type in the VNIR region and the felsic rock type in the TIR region. Therefore, the combined analysis of VNIR and TIR datasets allows the accurate delineation of charnockite lithology. However, vegetation in the study area introduces strong nonlinear spectral mixing effects, making it challenging to map the lithological units accurately. This study addresses this challenge using spectral mixture analysis to map charnockites in the Kodaikanal region. The fractional abundance study provides valuable insights into the lithological composition, demonstrating the effectiveness of spectral mixture analysis in mapping charnockites in the Kodaikanal region. Overall, the study demonstrates that the spectral mixture analysis significantly enhances the accuracy of lithology mapping, contributing to a more comprehensive understanding of the study area.

Calcareous nannoplankton response to middle-late Eocene climate and sea-level changes in the SW Neo-Tethys

We investigate the response of calcareous nannoplankton to the middle-late Eocene transition in the SW Neo-Tethys and compare our data to published results from X-ray diffraction (XRD) analysis, element content from X-ray fluorescence (XRF) and the abundance of microfossils in the coarse fractions of the sediment. The nannofossil assemblage is mainly composed of Reticulofenestra spp. (avg. 44%), Sphenolithus spp. (avg. 20%), Discoaster spp. (avg. 18%) and Pontosphaera spp. (avg. 10%). The Relative abundance of Zygrhablithus bijugatus and the Chiasmolithus ratio are used with the visual assessment to evaluate the preservation. The Sphenolithus-Reticulofenestra turnover occurred before the MECO at the Lutetian-Bartonian boundary. Besides the significant influence of an evolutionary gradient caused by the disappearance of numerous species of Sphenoliths, Discoasterids, and Coccolithaceae, and the first appearance of multiple species of reticulofenestrids, paleoenvironmental conditions imposed a significant impact on the calcareous nannofossil assemblages. The abundance of ostracods and the planktic/benthic foraminifera ratio depict relative sea-level changes. The microfossil assemblages and the lithological composition of the sediments track paleoclimatic and paleoenvironmental changes across the Lutetian to Priabonian. Dry conditions marked the middle Lutetian, followed by increased variability in hydrolyzing conditions during the late Lutetian and early Bartonian. An eutrophic and restricted ecosystem with high fine-grained material input is suggested for the Priabonian.

Grain-size, coarse fraction lithology and clay mineral compositions of surface sediments from Ross Sea, Antarctica: implications for their provenance and delivery mode

Knowledge on spatial distribution, provenance and delivery mode of surface sediment aids in interpretation of nearby sediment records for paleoenvironmental reconstruction. Such knowledge, however, remains largely unknown for the modern Ross Sea, Antarctica: a key region for understanding the dynamical behavior of Antarctic Ice Sheet over geological past. In this study, we address this gap by analyzing the grain-size distribution, coarse fraction (>250 μm) lithology, and clay mineralogy of a set of surface sediment samples covering the whole Ross Sea continental shelf. Our data reveals that the sediments were mostly delivered by icebergs and bottom currents. Iceberg delivery was significantly controlled by factors such as water depth, proximity to the iceberg sources, and invasion of the Modified Circumpolar Deep Water. Bottom current activity was stronger in the Western Ross Sea (WRS) than in the Eastern Ross Sea (ERS), controlled by the formation and transport of Dense Shelf Water. Three major sorts of coarse fraction were identified, including the quartz-rich Iceberg Rafted Detritus (IRD) originating from West Antarctic glaciers and primarily distributed in the ERS, the mafic rocks-rich IRD from the Ferrar Group as well as the McMurdo Volcanic Group and mainly found in the WRS, and deformed silt traced back to the grounding zone of the David Glacier-Dragalski Ice Tongue system. The distribution of clay minerals is dominated by a distinct binary mixing pattern. Smectite and kaolinite are mainly present in the ERS, derived from beneath the West Antarctic Ice Sheet. Higher illite and chlorite contents were found offshore of the Southern Victoria Land, derived from the East Antarctic craton. Overall, these results demonstrate that the glaciers draining into Ross Sea from both the East and West Antarctic Ice Sheets are highly dynamical in the context of modern climate conditions, with implications for potential contribution to future sea level rise.

Rockburst hazard assessment and prevention and control strategies in the Ruihai gold mine

Ruihai gold mine is a super large underwater gold mine with an initial mining depth of more than 1,400 m. Deep mining may face rockburst disaster. In order to scientifically control the potential rockburst risk, ensure the safety of underground personnel and equipment, and realize the safe and efficient mining of the mine, it is necessary to evaluate the rockburst risk of the mine and formulate appropriate rockburst risk warning and mitigation strategies. XRD mineral composition analysis and conventional rock mechanical tests were carried out on the parent rock granite samples. The results show that there are differences in the lithologic composition and rock mechanics parameters of the three colors of granite, which are preliminarily determined as three kinds of granite; The rockburst tendency of three kinds of granites is evaluated by using three classical rockburst criteria, and the discrimination results of the three rockburst criteria are not completely consistent or even contradictory. The application limitations rockburst risk assessment based on index criteria are discussed and analyzed in detail. It is proposed to apply microseismic monitoring technology to warn and manage the rockburst risk of Ruihai gold mine in development and mining stages, and put forward microseismic monitoring layout schemes and targeted rockburst prevention and control measures in different stages. The research results can provide reference for similar projects.

CHONK 1.0: landscape evolution framework: cellular automata meets graph theory

Abstract. Landscape evolution models (LEMs) are prime tools for simulating the evolution of source-to-sink systems through ranges of spatial and temporal scales. A plethora of various empirical laws have been successfully applied to describe the different parts of these systems: fluvial erosion, sediment transport and deposition, hillslope diffusion, or hydrology. Numerical frameworks exist to facilitate the combination of different subsets of laws, mostly by superposing grids of fluxes calculated independently. However, the exercise becomes increasingly challenging when the different laws are inter-connected: for example when a lake breaks the upstream–downstream continuum in the amount of sediment and water it receives and transmits; or when erosional efficiency depends on the lithological composition of the sediment flux. In this contribution, we present a method mixing the advantages of cellular automata and graph theory to address such cases. We demonstrate how the former ensure interoperability of the different fluxes (e.g. water, fluvial sediments, hillslope sediments) independently of the process law implemented in the model, while the latter offers a wide range of tools to process numerical landscapes, including landscapes with closed basins. We provide three scenarios largely benefiting from our method: (i) one where lake systems are primary controls on landscape evolution, (ii) one where sediment provenance is closely monitored through the stratigraphy and (iii) one where heterogeneous provenance influences fluvial incision dynamically. We finally outline the way forward to make this method more generic and flexible.

Morphometric variations of two patellid limpets between artificial breakwaters and natural reefs

Artificial shorelines often differ from natural reefs in shape, composition, and habitat complexity. They promote higher accumulation of pollutants and increased physiological stress, which lead to changes in species distributions and ecosystem functioning. This can promote trophic shifts and reduced genetic diversity of gastropod populations inhabiting artificial shorelines and might promote morphological changes, which may influence behaviour, vulnerability to predation, feeding efficiency, sex ratios, reproductive development, and overall fitness. This study explores inter- and intraspecific shell morphometric variations in Patella rustica and P. caerulea between breakwaters (ripraps) and natural reefs in three sites of Ceuta (North Africa, Spain), including a physicochemical assessment of the studied locations: shore orientation, inclination and wave exposure, and substratum nature, heterogeneity and roughness. Limpets on artificial substrata had a slightly smaller extra-visceral cavity and flattened shell profile, which suggests that the desiccation and temperature stress driven by the lithological composition and roughness of the studied substrata might have influenced the registered shell shape variation. However, the high morphometric variation registered for both species across sites and substrata suggests that limpets' morphology might be responding to a complex interaction of environmental and ecological factors rather than solely rock type. The findings of this study highlight the complex interplay between rock type and local environmental conditions in shaping patellid limpets’ shell morphology and provide insights into the adaptive mechanisms that drive shell shape variation in limpet populations in the face of coastal sprawl and anthropogenic global change.

РАСПРЕДЕЛЕНИЕ И ГЕНЕЗИС УГЛЕВОДОРОДНЫХ ГАЗОВ ДОННЫХ ОТЛОЖЕНИЙ ЛАПТЕВО-СИБИРОМОРСКОЙ ЗОНЫ ВОСТОЧНО-АРКТИЧЕСКОГО ШЕЛЬФА

Gases from bottom sediments of the Laptev–Siberian Sea zone contain methane (up to 8.3047 cm3/kg) and its homologues (down to and including pentane) totaling 0.0259 cm3/kg. The established values of the carbon isotope composition of methane (δ13С), the molecular weight of the hydrocarbon fraction, the weight concentrations of С1–С5 hydrocarbons and their ratios, the «wetness» and «transformation» coefficients of the hydrocarbons fraction, indicate the presence of various syngenetic and epigenetic gases in bottom sediments. Potential gas sources are modern sediments, peat, coal, gas and gas hydrate? deposits, solid bitumen, igneous rocks, and inferred oil and gas accumulations. It has been established that the distribution of hydrocarbon gases in sediments vertically and horizontally depends on the influence of a complex of geological factors – fold and fault tectonics, magmatism and seismic activity in the region, coal, oil and gas potential and bituminosity, organic saturation and lithological composition, hydrogeological, geocryological, and other conditions for accumulation of gases or their degassing.