Magnetic stratigraphy observed in ferromanganese crust

Summary. A sample of ferromanganese crust deposit (SCHW-1D) was cut into two sets of 1 mm slices for palaeomagnetic study. Alternating field and thermal demagnetization, and isothermal remanent magnetization analyses were performed on each thin slice. The results reveal the presence of a stable magnetism and both normal and reversed polarity intervals in the specimens. The observed polarity intervals cannot be confidently correlated with the geomagnetic polarity time-scale of the last 10 Myr due to the polarity overlap inherent in the sampling technique. But the results confirm the slow accretion rate of ferromanganese deposit determined by ¹⁰Be method and suggest potential use of ferromanganese deposits in palaeomagnetic and tectonic studies.     

Geometrical spreading factor of head waves in cased and open boreholes

Factors (coefficients) of geometrical spreading of compressional and shear head waves are calculated for an impulse multipole source of elastic oscillations in boreholes. It is shown that the length of the logging tool (i.e., the distance between the source and the nearest receiver) used for sonic measurements and the velocities of elastic waves in the medium both contribute to the factor of geometrical spreading. For a high-velocity formation (the shear wave velocity in the rock is higher than the compressional wave velocity in the fluid that fills the borehole) and a sufficiently long sonic tool with a monopole source, the coefficient of geometrical spreading is approximated by asymptotic formula 1/Z [Roever et al., 1974; Krauklis and Krauklis, 1976], where Z is the length of the tool; i.e., the amplitude of the compressional head wave decreases proportionally to the distance between the source and the receiver. In acoustically soft formations, this approximation is inapplicable even for long tools with length Z > 4 m. Waveforms in cased boreholes have a significant frequency dispersion even in case of good-quality cementing, and the factor of geometrical spreading there depends considerably on the length of the tool and the elastic properties of the rocks.     

Estimation of contaminant transport parameters for a tropical sand in a sand tank model

This research describes the goals, design and implementation of a quasi natural gradient, laboratory scale, sand tank (aquifer) model experiment. The model was used to study the transport of an inorganic tracer (Chloride) in groundwater, within a tropical aquifer (porous medium) material. Three-dimensional sand tank (1.8 m × 0.3 m × 0.8 m) experiments were conducted to investigate contaminant transport and natural attenuation within the sand tank. In all, 360 samples were collected during 24 sampling sessions, for the three days of the tracer experiments in the Sand Tank. The Owena sand is a poorly graded sand with 88.1 % sand and 11.9 % gravel. Geotechnical properties including; coefficient of uniformity C_u = 2.53, coefficient of gradation C_z = 0.181, hydraulic conductivity K = 5.76 × 10^?4 m/s, bulk density p = 1.9 Mg/m³, effective porosity n_e = 0.215 and median grain diameter D₅₀ = 0.55 mm, were determined. Other relevant hydraulic and solute transport parameters, such as dispersion coefficients and dispersivities were also established for the tropical soil.     

Rapid optical variability of the gamma-ray burst grb 080319b and its central engine

The results of observations of the optical emission that accompanied the gamma-ray burst GRB 080319B are reported. Observations were made using the TORTORA fast wide-field camera mounted on the REM robotic telescope in Chile. The behavior of the light curve before, during, and after the gamma-ray burst is described. The light curve consists of four, possibly periodic, 5–7 s long peaks 8–9 s apart. The behavior of the burst in the gamma and optical energy ranges are compared and the results of the theoretical interpretation of this comparison are reported.     

New CCRMP Reference Uranium ore BL-5 And Sulphide Concentrates CCU-I, CPB-1 and CZN-1

Under the Canadian Certified Reference Mate-vials Project (CCRMP), four new ore reference materials, one uranium ore BL-5 and three sulphide concentrates (CCV-1, CPB-1 and CZN-1) have been recently issued. The preparation, characterization and certification of these samples are briefly presented.     

Effects of hillslope geometry on surface and subsurface flows

Dividing a catchment to subcatchment or hillslope scales allows for better scrutiny of the changes in spatial distribution of rainfall, soil attributes and plant cover across the catchment. An instantaneous unit hydrograph model is suggested for simulating runoff hydrographs for complex hillslopes. This model is able to estimate surface and subsurface flows of the catchment based on the Dunne-Black mechanism. For this purpose, a saturation model is used to separate the saturated and unsaturated zones in complex hillslopes. The profile curvatures (concave, straight and convex) and plan shapes (convergent, parallel and divergent) of complex hillslopes are considered, in order to compute the travel time of surface and subsurface flows. The model was used for prediction of the direct runoff hydrograph and subsurface flow hydrograph of Walnut Gulch No. 125 catchment in Arizona (USA). Based on results, the geometry of hillslopes can change the peak of the direct runoff hydrograph up to two-fold, either higher or lower. The divergent hillslopes show higher peaks in comparison with the parallel and convergent hillslopes. The highest and lowest peak flows correspond to divergent-concave and convergent-straight hillslopes, respectively.     

Morphostratigraphy and fan morphology of doon valley

In the present study analysis of Landsat MSS, TM and SPOT imagery and digital analysis of IRS LISS-1 data of Doon Valley was carried out. Various geomorphic features were identified and classified, morphostratigraphy of the area has been established. Main geomorphic units of the area are Mussoorie Hill Range (Denudational), Siwalik Hills (Structural), Remnant Hills (Residual). Siwalik Piedmont. Doon Piedmont, River Terraces and Flood Plain. Three large fan lobes are identified on Doon Piedmont deposits, viz., Western fan lobe, Central fan lobe and Eastern fan lobe. Average slope of these three fan lobes are 2°21′, 2°3′, and 1°24′ for the western, central and eastern fan lobes respectively. Western and central fan lobes have been affected by neotectonic activity which is reflected in transverse profiles.