Fusulinoids from the Bashkirian–Moscovian transition beds of the Shahreza region in the Sanandaj–Sirjan Zone,Iran

International Journal of Earth Sciences - The presence of the Bashkirian–Moscovian (lower Pennsylvanian) sequence with mixed siliciclastics and fossil-rich carbonates has long been known from...     

Application of sequential Gaussian simulation to quantify the surface wave magnitude uncertainty within the faulted regions

Geostatistical simulations have been recently widely used in the geological and mining investigations. Variogram, the fundamental tools of geostatistics, can identify the spatial distribution of the regionalized variable within the area. One of the important issues of geostatistical simulation in seismotectonics is producing uncertainty maps, which could be applicable to predict earthquake parameters through the site locations especially for civil structures like bridges. It can help engineers to design the structure of interest better. Earthquake parameters as for example seismic fault and surface wave magnitude (Ms) have significant impact on the feasibility study of the civil structures. In this research, a method is presented to produce uncertainty maps for seismic fault and surface wave magnitude, Ms. For this aim, information related to surface wave magnitude and fault trace in Zagros region (SW of Iran) has been collected. Then, the relationships between them through the site location have been investigated and analyzed by conditional geostatistical simulation. In order to quantify the uncertainty of each parameter, the uncertainty formula after generating the E-type maps has been provided and discussed. Finally, in “Talgah Bridge” site, these uncertainty maps were produced to interpret the impact of the surface wave magnitude and fault trace in this specific civil structure.     

Dynamic mechanism of turbulent flow in meandering channels: considerations for deflection angle

To find turbulent flow structure inside meandering channels, three physical models of river meanders representing strongly curved bend, mild bend and elongated symmetrical meander loop were tested in this paper. Instantaneous velocity data in three dimensions were measured using Micro-ADV at different cross sections of these models. Depth averaged velocity vectors, streamwise velocity, secondary currents, turbulent and mean flow kinetic energy were investigated with respect to the sediment deposition pattern. In order to gain more regarding the force acting the sediment particles, three dimensional velocity fluctuations were analyzed in detailed inside the elongated symmetrical meander loop. Occurrence frequency, transition probability and angle of attack for different events were also computed for the points close to the bed. Of the present results, the importance of sweeps and ejections on sediment deposition can be detected. Further, distribution of bursting events is presented through the water column and compared the results with the previous works. Importantly, occurrence of fluctuating velocities in three dimensions at different locations inside the river meanders in addition to the effect of mean flow and turbulent components is responsible for sediment transport. Streamwise velocity distribution through the depth is also compared with some previous mathematical models. Researchers seeking the better control over the river morphology can apply this method without sacrificing much time and cost. This study is also included some insights to be pursued by future works.     

A new approach for the geological risk evaluation of coal resources through a geostatistical simulation

Estimations of mineral resources and ore reserves have been recently widely used by mining engineers and investors. The classification framework based on the prepared code by the Joint Ore Reserves Committee of The Australasian Institute of Mining and Metallurgy, Australian Institute of Geoscientists and Minerals Council of Australia (JORC code), which is one of the international standards for mineral resource and ore reserve reporting, provides a template system that conforms to international society requirements. Recent research has shown that an existing fault risk can affect the mineral resource and ore reserve estimation. According to this research, the faulted area that is involved in the effect on the estimated region is so extensive that it is not distinguishable. In this research, a new method called FGT (F for fault, G for grade and T for thickness) is introduced and presented for the estimation of mineral resources. The proposed method can provide an error map of a particular aspect of the combination of coal accumulation (G), fault risk (F) and thickness (T), and its output would categorise the mineral resources. This method was implemented in the Parvadeh Ш coal deposit, which is located in the eastern portion of Central Iran. The deposit contains five seams named B1, B2, C1, C2 and D; of these, C1 was selected as the most important seam in the exploratory grid analysis. Thus, C1 alone can reflect the properties of the Parvadeh Ш deposit. In this study, we compared the conventional method and the FGT method. This comparison indicated that the areas that should be rejected from the region in the FGT method are less and more distinguishable than those determined with the conventional method. Therefore, the inferred resources can be completely differentiated from the indicated and measured resources with a high resolution. The conventional method cannot distinguish between these three categories at this level of resolution. Therefore, the FGT approach has high precision in classifying the coal resource compared to the conventional method.     

Fault detection in 3D by sequential Gaussian simulation of Rock Quality Designation (RQD)

Gazestan phosphate ore deposit (Central Iran) is an apatite deposit which is instrumental in selecting the method of excavation. The position of fault systems and the condition of rock quality also play a role in the method used for mineral resources and ore reserves estimation. Conversely, the Rock Quality Designation (RQD) is a parameter that provides a quantitative judgment of rock mass quality obtained from drill cores. This factor can be applied to detect the fractured zones which occur due to fault systems. Additionally, the faulted areas can be determined by surface geological map and a few by core drilling. Some of the faulted areas are not distinguishable in the surface and are covered by soils, especially within 3D modeling and visualization. In this study, an attempt has been made to establish a relationship between the RQD percentages which were geostatistically simulated and faulted areas through the region. In comparison, the results showed that low RQD domains (RQD <20 %) can be interpreted as fault zones; high RQD domains (RQD >50 %) correspond to less fractured areas, and the contact between high and low RQD domain is gradual. Therefore, this categorization of RQD domains can be incorporated to detect the faulted zones in 3D models for mine design. Based on the categorization, the uncertainty within the area was calculated to introduce two new core drilling points for the completion of this phase of exploratory grid from the fault structural viewpoint, in order to have a proper model of ore reserve to estimate. It was concluded that this procedure can be utilized for conceptual comprehension of fault trends in 3D modeling for the method selection of excavation and complete the estimation procedure phase.     

Time-dependent wormholes in an expanding universedominated by traceless matter

Time-dependent wormhole solutions are found which evolve in a cosmological background. Solutions are presented both for GR and Brans-Dicke field equations. Conditions are derived for the supporting matter to be non-exotic. The traceless energy-momentum tensor needed to support the geometry is in the form of an anisotropic fluid. Far from the wormhole, the equation of state rapidly approaches that of an isotropic perfect fluid with p = 1/3 ρ. For the BD wormholes we obtain ρ = 0everywhere, except for the π = const. limit, in which case the GR results are reproduced. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effect of different meander curvatures on spatial variation of coherent turbulent flow structure inside ingoing multi-bend river meanders

In this paper, the effect of different curvatures on the spatial variation of coherent flow structure inside two physical models with both strongly curved and mild multi-bend meanders is investigated. Three dimensional flow velocities at three sequential meanders were measured using an Acoustic Doppler Velocity meter (Micro-ADV). Three dimensions of flow velocity are classified into two major classes and eight different bursting events. The contribution probability and transition probability of each zone is calculated from experimental data. The results indicated that the effect of curvature in sequential bends was important particularly for strongly curved bends. The contribution probability of the events for strongly curved meanders with relative curvature (R_c/B) of 2.6 were found to be higher than for mild curved meanders with relative curvature (R_c/B) of 4.43. The minimum contribution probability was found in external inward interaction event. In addition, analysis of bursting events showed that the highest values of transition probabilities occurred in the stable organizations for both models. The influences of different curvatures on distributions of the Reynolds shear stress, the turbulent kinetic energy, the streamwise velocity and the vertical velocity were also shown to be in good agreement with eroded bed. The above results can be useful for finding meandering patterns inside rivers and also in river training works.     

Toward real-time three-dimensional mapping of surficial aquifers using a hybrid modeling approach

A hybrid modeling approach is proposed for near real-time three-dimensional (3D) mapping of surficial aquifers. First, airborne frequency-domain electromagnetic (FDEM) measurements are numerically inverted to obtain subsurface resistivities. Second, a machine-learning (ML) algorithm is trained using the FDEM measurements and inverted resistivity profiles, and borehole geophysical and hydrogeologic data. Third, the trained ML algorithm is used together with independent FDEM measurements to map the spatial distribution of the aquifer system. Efficacy of the hybrid approach is demonstrated for mapping a heterogeneous surficial aquifer and confining unit in northwestern Nebraska, USA. For this case, independent performance testing reveals that aquifer mapping is unbiased with a strong correlation (0.94) among numerically inverted and ML-estimated binary (clay-silt or sand-gravel) layer resistivities (5–20 ohm-m or 21–5,000 ohm-m), and an intermediate correlation (0.74) for heterogeneous (clay, silt, sand, gravel) layer resistivities (5–5,000 ohm-m). Reduced correlation for the heterogeneous model is attributed to over-estimating the under-sampled high-resistivity gravels (about 0.5 % of the training data), and when removed the correlation increases (0.87). Independent analysis of the numerically inverted and ML-estimated resistivities finds that the hybrid procedure preserves both univariate and spatial statistics for each layer. Following training, the algorithms can map 3D surficial aquifers as fast as leveled FDEM measurements are presented to the ML network.     

Cyclostratigraphy across a Mississippian carbonate ramp in the Esfahan–Sirjan Basin,Iran: implications for the amplitudes and frequencies of sea-level fluctuations along the southern margin of the Paleotethys

International Journal of Earth Sciences - The Tournaisian–Visean carbonate successions of the Esfahan–Sirjan Basin (ESB) from Sanandaj–Sirjan Zone, Iran, have been used to...