Arabian Journal of Geosciences最新文献

The Buah Formation, a key carbonate unit within the Huqf Supergroup of Oman, was deposited during the latest Ediacaran to early Cambrian (~ 541–530 Ma) and is well-exposed in the Jabal Akhdar (JA) and Huqf regions. These carbonates offer critical insights into early Cambrian diagenetic processes and serve as valuable records for geochemical and isotopic investigations. Samples from both regions were analyzed for carbon, oxygen, and strontium isotopes, along with elemental ratios using multiple mass spectrometry techniques. JA samples exhibit a broader and more variable range of δ¹³C and δ¹⁸O values compared to the more constrained values in Huqf, reflecting more extensive diagenetic overprinting. Positive δ¹³C–δ¹⁸O correlations in both regions indicate diagenetic alteration by meteoric and/or burial fluids. In the JA section, δ¹³C values as low as − 8‰ at lower stratigraphic levels likely result from the oxidation of Neoproterozoic organic carbon, releasing ¹²C-enriched DIC, a signature consistent with the Ediacaran Shuram excursion in the underlying Shuram Formation. Mn/Sr ratios distinguish diagenetic systems, with burial diagenesis and/or organic carbon oxidation dominating in JA, and meteoric diagenesis prevailing in Huqf. Strontium concentrations in Huqf samples range from 20 to 2600 ppm, with most exhibiting uniform ⁸⁷Sr/⁸⁶Sr ratios (~ 0.7088), outside typical marine dolomite values. A subset aligns with marine signatures, suggesting mixed Sr sources including terrigenous, hydrothermal, and weathering-derived inputs. Two δ¹³C-based sample populations (< 0.5‰ and ≥ 0.5‰) in Huqf highlight diagenetic variability with implications for reservoir quality, fluid migration, and source preservation in early Cambrian petroleum systems in Oman.

Engineering practices have shown that the accurate assessment of stratum hydraulic conductivity (SHC) is crucial for ensuring engineering safety. A method proposed by Elsworth and Lee (2005) based on on-the-fly piezocone sounding provides an effective approach to SHC evaluation, but previous studies overlooked SHC anisotropy. The literature review reveals that the anisotropy ratio (horizontal-to-vertical SHC) typically ranges between 1.1 and 2.7 for most sedimentary formations, reflecting moderate but consistent directional dependence in SHC. This study addresses this limitation by incorporating SHC anisotropy into the original assumptions and further explicitly considers the effect of OCR. To validate the efficacy of this modified method, two case histories are examined. The results indicate that the predicted SHCs obtained using the modified method are in closer agreement with measured values compared to previous methods. The influence of SHC anisotropy and OCR on predicted SHCs cannot be disregarded, and the modified assumptions demonstrate a stronger correlation with engineering outcomes.

Cut blasting is a critical technique in roadway excavation, where the layout of cut holes directly affects the quality of excavation blasting. Based on the engineering context of phosphate mining in Hubei Province, this study first analyzed the effects of blasting gases and stress waves according to rock blasting mechanics, derived the calculation formula for the fracture zone radius, and determined the optimal distance between cut holes and empty holes. Subsequently, based on the calculated optimal distance, two empty hole layouts were designed: a six-empty-hole pattern and an eight-empty-hole pattern. Using ANSYS/LS-DYNA software, the effectiveness of cut blasting under these different layouts was analyzed from the perspectives of surrounding rock damage, dynamic evolution of the stress field, and extent of the cut cavity, followed by validation through field experiments. The results indicate that the optimal hole spacing between cut holes and empty holes is 170 mm, and that at the same distance, empty holes arranged at 45° generate greater circumferential (hoop) stress compared to those arranged horizontally. Furthermore, when sufficient compensation space cannot be provided, it is advisable to appropriately reduce the hole spacing, thereby reducing the rock volume between cut holes and empty holes to allow adequate expansion space for the rock.

Documentation of historic structures is widely recognized as an initial and crucial step in safeguarding tangible cultural heritage. Capturing and preserving detailed information (geometry and any architectural ornamental features) of these structures can ensure long-term conservation and provide valuable resources for research, education, and future conservation efforts. Selecting appropriate methods and techniques for documentation to create a comprehensive 3D representation of the historic structure is always a subject of research, and it is a challenging issue, specifically if the site is in an area with security concerns. This research aims to evaluate the Digital Surface Model of the Minaret of Amedy, a heritage site that is nationally registered. The data collection process was planned and executed, involving an e-survey GNSS receiver for measuring ground control points and a total station (TS, Leica TS06) for measuring control points on the four sides of the Minaret. Two hundred three images were taken by UAV, DJI Phantom 4 pro manually flown, and 196 images using Nikon D5300. The data was processed using the Agisoft Metashape photogrammetry software to create the final 3D Surface model and orthophotos. The RMS errors gained from UAV orthophotos are presented relative to the TS. Sub-centimeter accuracy for horizontal and vertical positions was obtained at low flight altitudes. The 3D digital models’ accuracy of the Minaret was assessed using conventional survey measurements, resulting in a maximum standard deviation in the coordinates of ±2.4 cm. The relative accuracy in distance measurement ranged from 0.00% to 0.20% and 0.00% to 0.30% in the horizontal and vertical directions, respectively. In addition, the maximum inclination of the Minaret in the East and West direction is about 18 cm and 13 cm, respectively, which were observed. These results reveal that the finding is valuable for future intervention and further research.

Based on preliminary seismic and drilling studies suggesting substantial thickness of the Dengying Formation in the Taiyang-Changning area along the southern margin of the Sichuan Basin's Northern Yunnan and Guizhou Depression as a platform margin, the risk exploration well TT1 was implemented to investigate sedimentary reservoir characteristics and exploration potential of the Dengying platform margin. Integrated analysis of astrochronological cycles, core tests, and log interpretations from the TT1 well enabled comprehensive 3D seismic interpretation of the Dengying Formation in the Taiyang area. Results demonstrate that Milankovitch cycles are extractable from calcium-element logging data of the TT1 well's Dengying Formation, with sedimentation controlled by a 35-kyr obliquity cycle at rates ranging from 6.24 to 13.17 cm/ka (mean: 9.81 cm/ka). Comparative analysis with the Yang-1 well at the same platform margin reveals well-developed reservoirs in the Yang-1 well's Dengying Formation, whereas the TT1 well exhibits overall poor reservoir development—only thin reservoirs occurring at the tops of the Deng-4 and Deng-2 Members—showing no correlation between reservoir presence and sedimentation rates, indicating dominant control by dissolution during the late Tongwan Movement. Integrated regional geological and seismic interpretation indicates that although the Changning-Taiyang platform margin features considerable stratigraphic thickness, the strong reservoir heterogeneity necessitates re-evaluation of reservoir formation and hydrocarbon accumulation mechanisms in the Dengying Formation..

Considering the interaction between the lining and soil, the analytic solutions to the stress function for the soil and lining deformation caused by the excavation are put forward for the shallow and deep tunnels. The applicability of the algorithm for the shallow and deep tunnels is verified by field monitoring data. Furthermore, through the parameter analysis, a comparison study on the variation of the soil and lining response caused by the excavation for the shallow and deep tunnels is conducted. It is observed that for the soil settlement trough with the value of zero, it is a “groove type” for the shallow tunnel, while “horizontal line” for the deep tunnel. The soil horizontal displacement is “butterfly type” for both shallow and deep tunnels. The lining tangential displacement for the shallow tunnel is an “oblique 8-type” with a smaller bottom, while that for the deep tunnel is a normal “oblique 8-type”.

Strata of the Campanian to mid-Maastrichtian Lokoja Formation exposed on road cuts in the Benin Flank, Anambra Basin, Nigeria, were subjected to facies analysis, visual textural analysis, sieve analysis, and pebble morphometry. The aim was to decipher the nature, transport mechanisms, and paleodepositional environment. Four distinct lithofacies—L1, L2, L3, and L4—were identified. Observed data show L1 and L2 as normally graded, poorly sorted trough cross-bedded, and planar cross-bedded matrix-supported gravels, respectively, which were categorized as gravel bars and bedforms lithofacies association representing braided streamflow paleodepositional processes. Similarly, L3 is described as poorly-moderately sorted normally graded planar cross-bedded sand, while L4 shows intercalations of thin beds of mud and sand. L3 and L4 were thereafter characterized as laminated sheet sand and mud lithofacies association depicting sheetflood paleodepositional processes. The braided streamflow and sheetflood paleodepositional processes are hypothesized to depict a middle-outer alluvial fan gross depositional environment. This inference is supported by binary discriminant plots of parameters from statistical analysis of granulometry data from 12 representative samples and pebble morphometry data obtained from 111 gravels from L1 and L2. Furthermore, paleocurrent data, textural analysis, and mineralogy of framework depict textural immaturity and low compositional maturity, which indicate first-cycle sedimentation, sourced from the Precambrian rocks of the Igarra Schist Belt, north of the study area. This contribution reinforces the multiple sediment provenance hypothesis of the Anambra Basin, comprising Precambrian basement and pre-Santonian rocks.

Situated in the Eastern Dharwar Craton, the Nalgonda granitoid suites consist of Tonalite Trondhjemite Granodiorite (TTG), biotite and two-mica granites, sanukitoids and hybrid granites. The petrography, whole-rock geochemistry and the Sm–Nd isotope geochemistry of the studied granitoids were done. The rocks are mainly made up of quartz, K-feldspar, plagioclase and biotite ± apatite. The biotite and two-mica granites are exclusively peraluminous in nature with S-type affinity, while the sanukitoids and the hybrid granites display both the I- and S-type characters with the metaluminous and peraluminous nature. The studied granitoids present negative anomalies in Nb–Ta, Pb and Ti suggesting the arc environment and the possible involvement of the subducted crust component to their formation. The isotope geochemistry results indicate heterogeneous source characteristics for the studied granitoids. The biotite and two-mica granites are from typical felsic crustal source, while the sanukitoids and the hybrid granites are from mixed older mafic crustal source with mantle component. The hybrid granites are formed due to interactions between the biotite and two-mica granites, the sanukitoids and the TTG. The geochemical and isotope systematics support a two-stage emplacement model for the Nalgonda granitoids as in the entire Eastern Dharwar Craton. The first stage is long process forming the TTG basement, and the second stage is short process generating the other three variants. This implies that, the subduction-collision tectonic setting is the principal tectonic model that permitted the emplacement of the Nalgonda granitoids.

This work documents a new, small footprint-like fossil from the Jilh Formation in Saudi Arabia. It also presents a preliminary account of fossilized tree trunks, roots, and leaf impressions within a sandstone layer from the Triassic (Norian) of Saudi Arabia. This provides a brief view into the recovery of woody trees after the Permian–Triassic extinction event and the vegetation of Gondwana. The fossils reported from the studied sites could help fill gaps in our understanding of paleogeography, the recovery of life, and floral biozonation during the Late Triassic period in the Mesozoic era.