Hasil untuk "Geology"

M. Trifunac, A. G. Brady

M. Mckibben, W. Shanks, W. Ridley

Shucai Li, Bin Liu, Xinji Xu et al.

J. Zalasiewicz, C. Waters, C. Summerhayes et al.

David J. Lohman, M. Bruyn, T. J. Page et al.

Songnian Lu, Huaibin Li, Chuan-Lin Zhang et al.

Wilson Scarpelli

In Amapá, northern Brazil, there is potential for large and not yet identified economical deposits of kaolin and bauxite in the Cenozoic belt of sediments that cover the margins of the Eastern Guiana Shield next to the Atlantic Ocean and the Amazon River. During geological exploration of these mineral resources, it seems adequate to consider the geological characteristics of the kaolin deposit of Morro do Felipe, at the southwest of Amapá, and the deposits of bauxite replacing Cenozoic kaolin-rich sediments at the coast of Guyana and Suriname. While the Brazilian deposits of bauxite of the Trombetas and Jari rivers occur in topographically stable plateaus, the corresponding plateaus containing bauxite in Guyana and Suriname were lowered to below seawater, and covered by younger sediments. In the southeast of Amapá, sediments similar to some that in Guyana and Suriname are guide to bauxite deposits, as the white sands, appear widespread over a large area. A few but significant exposures of high-grade kaolin suggest high tonnages of the mineral. The presence of these layers of kaolin, the mother-rock of the bauxite of the belt, and the presence of actual paleoduricrust improve the possibility of existence of hidden deposits of bauxite.

Byung-Ju Sohn, Jihoon Ryu, Sang-Wook Yeh et al.

Abstract Understanding the relationship between tropical heavy rainfall and large-scale circulation provides valuable insights for improving the climate models. Here we use Gaussian Mixture Model to identify two distinct types of heavy rainfall over the tropical Pacific, “strong deep convection” and “moderately strong deep convection,” using satellite-borne precipitation radar measurements. They differ in two typical climatological deep convection-related rainfall modes between the western and eastern Pacific regions. The occurrence frequency of moderately strong deep convection is significantly different between the western and eastern Pacific, potentially linked to the Walker circulation. The enhanced Walker circulation appears to weaken the local Hadley circulation, thereby reducing strong deep convective activity in the eastern Pacific. This increases moderately heavy rainfall and decreases diabatic heating, which can affect global climate. We propose incorporating the close link between large-scale Walker circulation and mesoscale heavy convective rainfall into the current climate models.

Da Li, Chengsuo Li, Wei Gao et al.

To meet the demand for reliably evaluating the measurement accuracy of the gravity gradiometer under dynamic conditions, a method for dynamically assessing the accuracy of the gravity gradiometer in a laboratory setting was proposed. Firstly, a method for creating an environment of approximately uniform gravity gradient was introduced. It involved the symmetric distribution of rectangular mass bodies within a localized spatial range to generate an approximately uniform gravity gradient excitation, with an excitation magnitude reaching 62.4 E and non-uniformity better than 1.3 E. Secondly, an evaluation criterion was proposed based on the gravity gradiometer’s sensitivity to gravity gradient excitation produced by the movement of mass bodies under dynamic laboratory conditions, leading to the proposal of a method for evaluating the dynamic accuracy of the gravity gradiometer in the laboratory. Finally, a laboratory dynamic accuracy evaluation system for the gravity gradiometer was established using a gravity gradient excitation device and a six-degree-of-freedom motion simulation platform. Validation experiments were conducted in the laboratory using a self-developed gravity gradiometer. The experimental results indicate that this evaluation system is capable of assessing the dynamic measurement accuracy of the gravity gradiometer in the laboratory, meeting the evaluation requirements for domestically developed dynamic gravity gradiometers.

WANG Xiang, ZHANG Guicai, JIANG Ping et al.

The volume sweep coefficient is essential for evaluating the development effect and formulating development adjustment plans for oil fields. This paper aims to study the variation law of volume sweep coefficient in different stages of water injection development. From the perspective of the injection pore volume multiple， a calculation model is built of displacement efficiency and injection pore volume multiple， and a calculation method of volume sweep coefficient is proposed based on oil-water relative flow theory and reservoir engineering principle. In addition， three test areas of Shengli Oilfield are taken as examples for calculation and analysis. The results show that the relationship between the displacement efficiency and the injection pore volume multiple satisfies an exponential equation， and the relationship curve between the two is upward convex. As the injection pore volume multiple increases， the displacement efficiency gradually increases from the minimum displacement efficiency and approaches the maximum displacement efficiency. The displacement efficiency calculation model is verified， and the average relative error between the predicted and measured values is only 1.90%. During the water flooding development， the relationship curve between the volume sweep coefficient and the injection pore volume multiple shows an evolution trend of fast rising， slow rising， and near platform. The calculation results can guide the effect evaluation of development adjustment measures. At present， the volume sweep coefficient of the three test areas is about 90%. There is a large amount of remaining oil in the swept area. It is urgent to study the description and start-up method of the main remaining oil in the swept area.

Sofiia Drozd, Nataliia Kussul

The Green Deal strategic plan for the development of renewable energy until 2030 is of particular importance in the context of the restoration of Ukraine’s post-war energy infrastructure. One of the key topics is the analysis of the possibilities of installing large solar power plants in Ukraine. In this article, a multi-criteria analysis of the suitability of the territory of Ukraine is carried out on the basis of climatic, topographic and land use criteria. To assess land suitability, criteria standardized using fuzzy logic with weights determined by experts through the method of pairwise comparisons were combined using a weighted sum model. Upon completing the study, a suitability map was generated, depicting zones with varying levels of suitability (ranging from 0 to 1) for solar power plant placement. It was found that more than 35.68% of the country has average values of the suitability index (0.65–0.7), and approximately 18.82% show high indicators (<0.7). Conditions are especially favorable in the south of Ukraine.

Tom Broeg, Michael Blaschek, Steffen Seitz et al.

Precise knowledge about the soil organic carbon (SOC) content in cropland soils is one requirement to design and execute effective climate and food policies. In digital soil mapping (DSM), machine learning algorithms are used to predict soil properties from covariates derived from traditional soil mapping, digital elevation models, land use, and Earth observation (EO). However, such DSM models are trained for a specific dataset and region and have so far only allowed limited general statements to be made that would enable the models to be transferred to different regions. In this study, we test the transferability of SOC models for cropland soils using five different covariate groups: multispectral soil reflectance composites (satellite), soil legacy data (soil), digital elevation model derivatives (terrain), climate parameters (climate), and combined models (combined). The transferability was analyzed using data from two federal states in southern Germany: Bavaria and Baden-Wuerttemberg. First, baseline models were trained for each state with combined models performing best in both cases (<i>R</i>² = 0.68/0.48). Next, the models were transferred and tested with soil samples from the other state whose data were not used during model calibration. Only satellite and combined models were transferable, but accuracy declined in both cases. In the final step, models were trained with samples from both states (mixed-data models) and applied to each state separately. This process significantly improved the accuracies of satellite, terrain, and combined models, while it showed no effect on climate models and decreased the models based on soil covariates. The experiment underlines the importance of EO for the transfer and extrapolation of DSM models.

Luc Achille Ziem A Bidias, Sahada Mouchili Nguegni, Dieudonné Charles Isidore Ilouga et al.

This study was conducted in Kouoptamo, located in the Noun Plain in Western Cameroon, with the main objective of inventorying and evaluating the geological heritage, and promoting the protection and geoconservation of geosites, and their use in geotourism development. Geosites in the region include dammed lakes (Petpenoun lakes), maars (Sanka Ndoumkain Maar, Tchoua Maar), scoria cones (Nkoambeng, Kechuentim, Ngouen volcanoes), a dome (Njigoumbé Dome) and a managed natural area (Petponoun Domain). Most geosites have a high scientific, aesthetic and educational value. The method used for the inventory and assessment of geosites in this work is according to Reynard, et al. (2016), which is more suitable for geological heritage on a regional scale. The scientific value in this method is composed of four criteria, namely rarity, representativeness, integrity and palaeogeographical interest. Each of these criteria is evaluated independently by a numerical score ranging from 0 (nil) to 1 (very high) in intervals of 0.25. The overall average scientific value of the Kouoptamo geosites is 0.77. Nkoambeng Volcano has the highest scientific value (0.88), followed by Tchoua Maar, Sanka Ndoumkain Maar, Njigoumbé Dome and Ngouen Volcano, all of which score 0.81, while Kechuentim Volcano and Petpenoun Domain score 0.75 and 0.69, respectively. The integrity of several of these geosites is preserved, mainly the Petpenoun lakes, the Tchoua Maar, and the Sanka Ndoumkain Maar. Geosites such as Sanka Ndoumkain Maar, Tchoua Maar, Njigoumbé Dome and the Nkoambeng, Kechuentim, and Ngouen volcanoes are representative of the regional geomorphology. Artisanal quarries (Nkoambeng Volcano) and industrial quarries (Njigoumbé Dome), as well as agro-pastoral activities, tend to degrade these geosites, which in general do not benefit from any legal protection. It is strongly recommended that geoconservation policies be adopted for these geosites, in order to preserve and develop these sites for their considerable geotourism potential while taking into account the current resource and land usage to find an optimum, sustainable strategy.

Ye Zhang, Jinqiao Chen, Yanlong Li

Objective Borehole Televiewer (BHTV) imaging serves as an effective tool for analyzing deep rock formations in geological engineering, offering crucial insights into surface discontinuity extensions and the distribution of buried discontinuities, especially within complex geological environments associated with hydraulic engineering projects. Recognizing the current issues of subjectivity and low efficiency, prevalent in the manual calculation of rock discontinuity morphological characteristics within rock masses, we propose an intelligent approach for segmenting geometric data from digital borehole images. Leveraging the segmentation outcomes, an image thinning technique is employed to facilitate precise quantitative analysis of borehole data. Methods In this research, we employ deep learning models to intelligently identify fractures within BHTV images, utilizing various network structures such as Unet, SegNet, and DeepLabV3. The recognition results are compared with traditional image processing methods, demonstrating the advantages of deep models in accurately segmenting complex geological images. Furthermore, we enhance the model's performance by incorporating an attention mechanism into the encoder-decoder process.Once precise segmentation of rock discontinuities is achieved, the fracture skeleton is extracted using the image thinning method, representing fractures as one-pixel-width curves. Ultimately, automated calculations is completed for dip strike, dip angle, and fracture thickness. Results This method is applied to segment and calculate borehole televiewer images in hydraulic engineering. Comparing the results of manual extraction and automatic extraction of fracture information, the error of dip strike and dip angle is less than 3°, and the fracture thickness error is less than 0.65 mm. Conclusion The results verify that the intelligent calculation method of fracture information proposed in this paper. The proposed method has wide application prospects in hydraulic engineering.

Constantin, Joël, Saint-Bezar, Bertrand

Increasing displacement along an isolated fault is generally associated with fault propagation within the host rock. This propagation is controlled by several factors, including host-rock lithology, tectonic context and the presence of preexisting structures. Consequently, fault propagation is rarely linear and continuous, instead often alternating between periods of propagation and arrest, or propagation locking. We present structural data collected in a field at the terminal tip of the Argence Fault, one of the regional normal faults in the northern part of the Aquitaine Basin. At the outcrop, the fault cuts a heterogeneously layered sequence of limestones, marls and clays. We observed a well-exposed tip of this fault, and analyzed the deformation patterns. This analysis provided insights into the processes involved in the formation of fault zones, the fault damage zone in particular, and the effects of contrasting mechanical properties on modes of fault growth.

JU Ming-he, TAO Ze-jun, LI Xiao-feng et al.

Particle impact, a new drilling technology, has been applied in drilling and gas and oil exploitation. Also, it is considerably promising as an assisting rock-breaking method for the excavation of tunnels in extremely hard rocks. In this paper, an experimental study was conducted to investigate the effects of particle impact number, particle strength, and particle impact velocity on the damage and fragmentation characteristics of surface impact crater in extremely hard granite. The three-dimensional morphology, rock fragments, and mineral fragmentation properties in the impact crater were quantitatively analyzed. The results indicate that the maximum depth of the impact crater increases in a parabolic way, while both the volume and surficial area of the impact crater grow linearly with the impact number. Moreover, the impact crater volume first increases and then decreases with the particle impact velocity, with a critical velocity of nearly 82.5 m /s. In addition, the difference in mesoscopic fragmentation mechanism inside and outside the crater center causes the double-peak characteristics of average size of rock fragments. The volume, surficial area and maximum depth of the impact crater increase linearly with the kinetic energy of impacting particles in the double logarithmic coordinate system. The fractal dimension variations of internal crack distribution in main minerals around the impact crater under different impact velocities and numbers were obtained through image processing method. The experimental results manifest that the damage scale of rock crater is enlarged through improving particle velocity and impact number, while particle velocity exerts a more significant effect than impact number does.

K. V. Calvin, A. Snyder, X. Zhao et al.

<p>Future changes in land use and cover have important implications for agriculture, energy, water use, and climate. Estimates of future land use and land cover differ significantly across economic models as a result of differences in drivers, model structure, and model parameters; however, these models often rely on heuristics to determine model parameters. In this study, we demonstrate a more systematic and empirically based approach to estimating a few key parameters for an economic model of land use and land cover change, gcamland. Specifically, we generate a large set of model parameter perturbations for the selected parameters and run gcamland simulations with these parameter sets over the historical period in the United States to quantify land use and land cover, determine how well the model reproduces observations, and identify parameter combinations that best replicate observations, assuming other model parameters are fixed. We also test alternate methods for forming expectations about uncertain crop yields and prices, including adaptive, perfect, linear, and hybrid approaches. In particular, we estimate parameters for six parameters used in the formation of expectations and three of seven logit exponents for the USA only. We find that an adaptive expectation approach minimizes the error between simulated outputs and observations, with parameters that suggest that for most crops, landowners put a significant weight on previous information. Interestingly, for corn, where ethanol policies have led to a rapid growth in demand, the resulting parameters show that a larger weight is placed on more recent information. We examine the change in model parameters as the metric of model error changes, finding that the measure of model fitness affects the choice of parameter sets. Finally, we discuss how the methodology and results used in this study could be used for other regions or economic models to improve projections of future land use and land cover change.</p>

Erol Sarı, Mustafa Kumral, Mehmet Fatih Hüseyinoğlu et al.

The study area covers the northern coasts of Cyprus from the Güzelyurt Gulf to the Gazimağusa Gulf. This study was carried out in order to reveal the presence of the alien foraminifera, which are widely distributed in the Eastern Mediterranean particularly Amphistegina lobifera in the study area, and the effects of trace elements on faunal assemblages (foraminifera, ostracod and mollusc). The bottom sediment samples were taken from eighteen different points and depths, the faunal assemblages were examined, and the sediment distribution map of the studied area was made by ICP-MS analysis and geochemical evaluations. 30 genera and 48 species of foraminifera have been identified, of which 9 species belonging to 6 genera are the alien foraminifera. These are: Spiroloculina angulosa, S. antillarum, Hauerina diversa, Coscinospira hemprichii, Peneroplis pertusus, P. planatus, Amphisorus hemprichii, Sorites orbiculus and Amphistegina lobifera. Amphistegina lobifera was observed to be abnormally abundant in most of the samples. This foraminiferal assemblage of Red Sea origin constitutes a poor assemblage compared to the alien assemblages in Turkish Mediterranean coastal areas. It has been determined that the ostracod and mollusc genera and species found in the same samples belong to the typical Mediterranean and Aegean Sea community.

Krzysztof Hryniewicz, Kazutaka Amano, Robert G. Jenkins et al.

We present a systematic study of thyasirid bivalves from Cretaceous to Oligocene seep carbonates worldwide. Eleven species of thyasirid bivalves are identified belonging to three genera: Conchocele, Maorithyas, and Thyasira. Two species are new: Maorithyas humptulipsensis sp. nov. from middle Eocene seep carbonates in the Humptulips Formation, Washington State, USA, and Conchocele kiritachiensis sp. nov. from the late Eocene seep deposit at Kiritachi, Hokkaido, Japan. Two new combinations are provided: Conchocele townsendi (White, 1890) from Maastrichtian strata of the James Ross Basin, Antarctica, and Maorithyas folgeri (Wagner and Schilling, 1923) from Oligocene rocks from California, USA. Three species are left in open nomenclature. We show that thyasirids have Mesozoic origins and appear at seeps before appearing in “normal” marine environments. These data are interpreted as a record of seep origination of thyasirids, and their subsequent dispersal to non-seep environments. We discuss the age of origination of thyasirids in the context of the origin of the modern deep sea fauna and conclude that thyasirids could have deep sea origins. This hypothesis is supported by the observed lack of influence of the Cretaceous and Paleogene Oceanic Anoxic Events on the main evolutionary lineages of the thyasirids, as seen in several other members of the deep sea fauna.

E. C. O'Donnell, J. L. Wadham, G. P. Lis et al.

Determining the concentration and composition of dissolved organic carbon (DOC) in glacial ecosystems is important for assessments of in situ microbial activity and contributions to wider biogeochemical cycles. Nonetheless, there is limited knowledge of the abundance and character of DOC in basal ice and the subglacial environment and a lack of quantitative data on low-molecular-weight (LMW) DOC components, which are believed to be highly bioavailable to microorganisms. We investigated the abundance and composition of DOC in basal ice via a molecular-level DOC analysis. Spectrofluorometry and a novel ion chromatographic method, which has been little utilized in glacial science for LMW-DOC determinations, were employed to identify and quantify the major LMW fractions (free amino acids, carbohydrates, and carboxylic acids) in basal ice from four glaciers, each with a different type of overridden material (i.e. the pre-entrainment sedimentary type such as lacustrine material or palaeosols). Basal ice from Joyce Glacier (Antarctica) was unique in that 98 % of the LMW-DOC was derived from the extremely diverse free amino acid (FAA) pool, comprising 14 FAAs. LMW-DOC concentrations in basal ice were dependent on the bioavailability of the overridden organic carbon (OC), which in turn was influenced by the type of overridden material. Mean LMW-DOC concentrations in basal ice from Russell Glacier (Greenland), Finsterwalderbreen (Svalbard), and Engabreen (Norway) were low (0–417 nM C), attributed to the relatively refractory nature of the OC in the overridden palaeosols and bedrock. In contrast, mean LMW-DOC concentrations were an order of magnitude higher (4430 nM C) in basal ice from Joyce Glacier, a reflection of the high bioavailability of the overridden lacustrine material (&gt; 17 % of the sediment OC comprised extractable carbohydrates, a proxy for bioavailable OC). We find that the overridden material may act as a direct (via abiotic leaching) and indirect (via microbial cycling) source of DOC to the subglacial environment and provides a range of LMW-DOC compounds that may stimulate microbial activity in wet subglacial sediments.