Arabian Journal of Geosciences最新文献

Expansive soils, known for their susceptibility to early damage due to their swelling and shrinkage properties, pose a significant technical challenge in geotechnical engineering. This study explores the optimization of microbial-induced improvement of these soils, emphasizing the pivotal role of temperature, pH, and time on both microbial growth dynamics and the soil’s swell-shrink behavior. A series of microbial growth and expansive soil swell-shrink tests were conducted, employing response surface methodology (RSM) to develop regression models that delineate the optimal conditions for microbial solution concentration and the free swelling ratio. The findings indicate that temperature and curing time exert a more pronounced influence on these parameters than pH. Notably, microbial solution concentration exhibits a peak with increasing temperature, while the free swelling ratio inversely declines. The curing time’s effect is characterized by an initial peak in microbial solution concentration followed by a gradual decrease, with the free swelling ratio of the soil consistently diminishing. The optimization analysis pinpoints the optimal conditions at 32 °C, pH 6.5, and a curing duration of 48 h, where the reduction in both microbial solution concentration and free swelling ratio is maximized. Under these conditions, microorganisms are used for improvement, the microbial solution’s OD₆₀₀ value peaks at 1.996, significantly reducing the expansive soil’s free swelling ratio from 169 to 64.3%.

This comprehensive study focuses on the evaluation and comparison of seismic hazard parameters in the Northeast Indian region, covering longitude 87°–98°E and latitude 20°–30°N, which is characterized by high seismicity and complex tectonic structures. The study aims to estimate seismicity parameters such as the magnitude-frequency distribution and Gutenberg-Richter a and b-values using maximum likelihood method (MLM) through the Zmap and the statistical approach proposed by Kijko. The study area is divided into six seismogenic source zones, and zone-wise seismicity parameters are estimated using the declustered catalog considering whole earthquake data and data within the completeness period. The study estimated seismicity parameters using completed catalogs. The results showed that the a value ranged from 2.85 to 5.06, and the b value ranged from 0.76 to 0.92 when using Zmap. Meanwhile, when using the Kijko approach, the estimated a value ranged from 2.70 to 4.65, and the b value ranged from 0.64 to 0.85. The estimated seismicity parameters are used to estimate the return periods and probabilities of earthquakes with different magnitudes for each zones. From the probability curve, it is observed that the probability of earthquake occurrences decreases exponentially with magnitude. For all zones, a high probability of occurrence is observed for earthquake magnitude 6 both in 50 and 100 years. The return periods for different magnitudes estimated from the Zmap and Kijko methods are consistent with some variations among the six source zones. Zmap estimates were lower for smaller magnitudes and higher for larger magnitudes than the Kijko method. The difference factor varied depending on the source zone and magnitude. In general, Zmap estimates were lower by a factor of 1.0 to 1.34 for lower magnitudes and higher by a factor of 1.01 to 1.35 for higher magnitudes.

This paper presents a comprehensive lithofacies and microfacies analysis of the exposed Cenozoic (Late Paleocene to Early Eocene) Upper Jafnayn Formation in the Jafnayn area, Northern Oman. The study meticulously documents the color, lithology, grain composition, bed thickness, types, and nature of bed contacts and fossil content of the formation. Over 85 fresh rock samples from various lithofacies were collected for this analysis. The samples were treated with blue epoxy, thin-sectioned, and half-stained with potassium ferricyanide and alizarin red to aid in mineralogical identification. To accurately determine microfacies, quantify components, reconstruct origins, and build a depositional model for the Upper Jafnayn Formation, 300 points were counted per thin section using a point-counting method. This analysis identified five distinct facies and 16 microfacies, with ten containing quartz grains and six lacking quartz sand. The microfacies provide insights into the depositional environments of the Upper Jafnayn Formation: four represent backshoal conditions, seven indicate shoal environments, three correspond to foreshoal settings, and two exhibit characteristics overlapping between backshoal and foreshoal environments. The presence of Alveolinid foraminifera, red algae, and occasional coarse coral debris within the cleaner limestone sections further characterizes the formation. The diverse lithofacies and microfacies of the Upper Jafnayn Formation reveal a dynamic interplay between high-energy and low-energy depositional environments, influenced by sea level fluctuations. This comprehensive understanding of the formation’s depositional history is crucial for research teams aiming to identify potential hydrocarbon traps and reservoirs in the region.

Investigating the phenomenon of topographic amplification and the seismic response of the site is an important issue that has already attracted the attention of many researchers. The studies and researches conducted in the field of topographical effects and also the phenomenon of the amplification of earthquake waves in passing through surface layers have shown that topography has a great impact on the amount of damage caused by earthquakes. The local topographic characteristics amplify the strong movements of the ground during an earthquake and ultimately cause great damages. In this article, the effects of a site (take, for example, one of the most common topographical forms in nature, such as a semi-sinusoidal hill) on the seismic response of the earth’s surface subjected to vertically propagating shear vertical (SV) waves have been studied using FLAC 2D, a two-dimensional finite-difference program. In the numerical modeling, the elastic linear behavior has been used. In this regard, in order to investigate the effects of layering on the response of semi-sine hills, two-layered and three-layered hills with different layering characteristics and thicknesses are considered the basis of this article. In this research, the effect of soil characteristics, layering thickness, and the position of the loose layer has been investigated. From the obtained results, it can be concluded that the characteristics and thickness of the layering and the position of the loose layer have effects on the general trend of amplification on top of the hills and de-amplification near the toe of hills in response to horizontal motion for acceleration, velocity, and displacement components.

Climate change is associated with heavy and excessive rainfalls in the tropics with anticipated fluvial and pluvial flooding. This study aimed to analyze the natural predispositions of river basins in Anambra State, Nigeria to flooding in this era of changing rainfall characteristics necessitated by climate change. This study used primary and secondary data sources. The primary data include field visits and observations, oral interviews, photographs, and measurements, whereas the secondary data include satellite images from the USGS (SRTM DEM), shapefile from Diva GIS, and other related literature. The morphometric parameters analyzed included the area of the sub-basin, perimeter of the sub-basin, stream order, stream length, stream numbers, and sub-basin length, the drainage density, drainage texture, form factor, shape factor, elongation ratio, relief ratio, relative ratio, ruggedness number, and bifurcation ratio. The findings revealed that the sub-basins are elongated in shape, with a dendritic stream pattern, whereas the other hydrogeomorphological characteristics revealed the flooding propensity and erosivity level downstream of their basins. The drainage density (D_d) of the sub-basins of Anambra state indicates that the basins are made up of porous subsurface material and, therefore, will not encourage flooding. The drainage texture (D_t) has a very coarse texture category and indicates the presence of fewer streams over basins, as it considers the total number of streams of all orders. The form factor (R_f) indicates that there is a very low possibility of sudden peak discharge in the basins during heavy rainfalls. The shape factor (S_f) indicates strongly elongated basins (i.e., S_f > 0.45) elongated basins indicate a long travel time for flow from the headwaters to the outlets. The sub-basins’ terrain are categorized as having slight, moderate, and sharp morphology with slight, moderate, and sharp roughness and unevenness; slight to moderate exposure to the risks of flood hazards; moderate soil erosion; and/or mass movement. This implies that the increase in flooding in the state might be attributed to increasing urbanization, dense settlement, and human intervention in river flow.

This work principally involves the petrophysical evaluation and the determination of hydrocarbon saturation of potential reservoirs in the Rio del Rey basin. Petrel 2017 software was used to interpret the obtained data well logs and seismic. Illustrator CS was used to find tune and arrange the maps and figures. From the studies, four reservoirs (S1A1, S1A2, S1A3 and RB) in total were successfully detected from two target wells: S-C1 and S-FB. Porosity, permeability and water saturation ranged between 17 to 22%, 149 to 193.5 mD and 60 to 100%, respectively. Good reservoirs were discovered based on the petrophysical studies at multiple zones, but only two were of interest to this work. The most prolific zones are those with less than 80% saturation of water and porosity of 17% and 22%. The remaining zones had the same porosity and permeability range but were not considered prolific zones due to high shale volume and more than 80% water saturation. Seismic interpretation revealed the presence of seven listric faults, two major faults (F9 and F19 trending in the NE-SW and E-W direction, respectively) and five minor faults (F7, and F2, and F6 which appear in the two wells). Faults F9, F2 and F6 trend in the same direction as the major faults: Eastern to Western. Four major horizons (S1A1, S1A2, S1A3, RB) were identified in well S-C1, and only one of these major horizons was identified in well S-FB (S1A3). All these horizons correspond to the five reservoir tops to be studied in the two target wells. Rollover anticlinal structures and fault closures between the listric faults were identified. All three types of environments of deposition of sediments were found in the reservoirs: progradational (sediment shift landward), aggradational (deposition far away from shore) and retrogradational (sediment shift seaward) sequences. Rollover anticline or four-way structural closure constitutes the main mechanism for trap formation. STOOIP of the reservoirs have been determined with S1A3 and RB zone being more prolific. The STOOIP of S1A3 is given by 11.2 MMbbls high case, 8.5 MMbbls base case and 7.4 MMbbls low case, while the STOOIP of RB is given by 8.6 MMbbls for the base case and 10.8 MMbbls for the high case.

This current research analyzed the spatio-temporal trends and variability of monsoon season and month-wise rainfall for 26 tehsils in the upper Godavari basin (UGB) of Maharashtra, India. An attempt has been evaluated on rainfall data (1998–2023) obtained from the Department of Agriculture, Maharashtra. To assess the basic trends of the rainfall data statistical techniques, i.e., mean monthly and monsoonal rainfall, standard deviation (SD), and non-parametric method such as Mann–Kendall (MK) trend test, furthermore, simple linear regression (SLR) equation has been applied. Rainfall variability has been examined using the coefficient of variation (CV), and analyzed data has been incorporated into the GIS environment to prepare various maps. The MK analysis revealed an insignificant decreasing trend, especially in June, which suggests a declining trend in rainfall quantity. In contrast, an insignificant increasing trend has been noticed in September which interprets that maximum rainfall occurred in this month in the UGB. In the monsoon season, most of the places denoted no trend, while Dindori (Z = 2.51) and Akole (Z = 1.76) tehsils show significant increasing trends but a drastic decline in the Igatpuri tehsil (Z = − 2.65) The rainfall has been seen to increase towards the west due to the block posed by the Western Ghat to the east-flowing monsoon wind. This study also revealed the monsoon rainfall varied between 93% (Ahmednagar tehsil) and 25% (Aurangabad tehsil) and monsoon month-wise maximum variability (154%) at Ahmednagar in September and minimum (29%) at Igatpuri in July. The approach adopted in this paper identified the micro-level rainfall distribution, trend, and variability which will be greatly advantageous for sustainable water resource management.

The study area represents a western urban extension of the overpopulated Nile Delta toward the west. The exploration and evaluation of groundwater in the West Nile Delta has great importance because of the need to establish new industrial and agricultural areas while preserving the agricultural lands of the Nile Delta. This study includes the direct current (DC) resistivity method for exploring water-bearing layers and the hydrogeochemical assessment of groundwater for drinking, irrigation, and other uses. The DC resistivity results reflected four geoelectrical layers, with one water-bearing layer selected. The hydrogeochemical evaluation was carried out by the analysis of physicochemical parameters and major ion concentrations. The water quality index (WQI) results showed that the groundwater was divided into 53.3% excellent, 33.3% good, 6.6% poor, 6.6% very poor, and 0% unsuitable for drinking. The electrical conductivity, total dissolved solids, soluble sodium percentage, sodium absorption ratio, residual sodium carbonate, magnesium absorption ratio, and chloride content were used to estimate the groundwater quality for irrigation. While TDS, total hardness, and corrosivity ratio were used to evaluate groundwater for domestic uses, the findings of the WQI study recommend that the excellent and good water wells can be utilized for drinking, while the remainder of the wells can’t be used without filtering with adequate membranes.

An investigation on medium to coarse-grained quartz grains (QG) recovered from a ~ 100-m drilled core section of the Sundarbans Forest site in the southwestern Bangladesh was carried out to infer the source and depositional environment. Thirty-six microtextures were identified from 200 QG using a scanning electron microscopy (SEM). The QG surface features are categorized into mechanical (number of features n = 25), chemical (n = 5), and combined mechanical and chemical (n = 6), which provide invaluable insights on the transport mechanism, provenance, and depositional environment. Microtextures of mechanical origin include parallel striations, straight steps, crescentic percussion marks, conchoidal fractures, arcuate steps, fresh polished surfaces, V-shaped marks, broken edges, abrasion fatigue, and bulbous and meandering edges, which are more common in QG and ascribed to high-energy eolian and fluvial transports. The abundant chemical features such as crystalline overgrowth, silica globules, scaling, silica pellicle, and silica flower are omnipresent on QG surfaces, demonstrating a subaqueous diagenetic environment. Fracture plates/planes, high relief, elongated depressions, adhering particles, chatter marks, and oriented etch pits are common in the QG, suggesting a subaqueous nearshore marine environment. There is a high abundance of quartz (Si), feldspar (Na and K), titanite (Ti), and zircon (Zr) in the core sediments, indicating their derivation from felsic source rocks.

Self-regenerating fallows are areas left to regenerate naturally after agricultural use and are typically characterized by diverse plant species and minimal human intervention. To measure the efficiency of this natural fallow system, we evaluated soil organic carbon (SOC) and nutrient concentrations vis-à-vis the fallow duration. The study site was located in the Onigbedu community, Ogun State, Nigeria, with large commercial limestone deposits. Mining and agriculture are the main land use types. The study was oriented on 100 hectares of land previously cultivated at different times and left to fallow. The fallow duration ranged between less than 3 years and more than 20 years. At the end of this study, it was observed that the soils are within a large group of calcareous soils. SOC ranged from 15 to 26 mg/g, available phosphorus from 3.0 to 6.0 mg/kg, total nitrogen from 0.5–2.0 mg/g, effective cation exchange capacity (ECEC) from 2.0–24.0 cmol₍₊₎/kg, calcium from 2.0–20 cmol₍₊₎/kg, Mg from 1.0–2.0 cmol₍₊₎/kg, 0.1–0.4 cmol₍₊₎/kg, manganese from 19 to 80 mg/kg, and zinc from 1.5–2.0 mg/kg in increasing order of fallow duration. Soil nutrients and SOC improved consistently with increasing fallow periods. While fallow duration influenced soil nutrient build-up, other management practices and environmental factors also play significant roles. Farmers can enhance soil fertility and nutrient levels by optimizing fallow durations and using efficient soil management practices, leading to sustainable agriculture and improved crop yields.