Is the outcrop topology of dolerite dikes of the Precambrian Singhbhum Craton fractal?

In the Precambrian Singhbhum Craton of eastern India, newer dolerite dikes occur profusely with varying outcrop lengths. We have analysed the nature of their length-size and orientation distributions in relation to the theory of fractals. Two orientational sets of dikes (NW-SE and NE-SW) are present. Both the sets show strongly non-power-law size distributions, as reflected in non-linear variations in logarithmic space. We analyzed thousands of data, revealing that polynomial functions with a degree of 3 to 4 are the best representatives of the non-linear variations. Orientation analysis shows that the degree of dispersions from the mean trend tends to decrease with increasing dike length. The length-size distributions were studied by simulating fractures in physical models. Experimental fractures also show a non-power-law distribution, which grossly conforms to those of the dolerite dikes. This type of complex size distributions results from the combined effects of nucleation, propagation and coalescence of fractures

Numerical estimation of the initial hinge-line irregularity required for the development of sheath folds: a pure shear model

Non-cylindrical sheath folds often develop by the accentuation of inherent geometrical irregularities along the hinge line during progressive deformation. This paper presents an analysis of the growth of such non-cylindrical folds in pure shear as a function of a non-dimensional initial irregularity factor ζo (ζo = -log10 [Ao/Wo], where Ao and Wo are the amplitude and the wavelength of a sinuous hinge line, respectively). Curvature accentuation of the hinge line produces sheath-like non-cylindrical folds in passive layers only when ζo ≤ 1. Folds with ζo > 1 remain weakly or moderately non-cylindrical even after a large finite strain (λ = 36). An increasing flattening strain (1 > k value > 0) component in the deformation reduces the degree of non-cylindricity. We extend the analysis into layered systems with viscosity contrasts (i.e. viscosity ratio, R), considering a strain-partitioning factor λf (the strain ratio between the fold hinge and bulk medium). Using finite element methods, it is shown that λf can be small even for low values of R (4-8). Consequently, strong non-cylindricity does not grow in higher-viscosity layers for ζo = 1. We ran experiments using three-dimensional finite element models to investigate the additional effects of mechanical bending on curvature accentuation of the hinge line. These experiments also show little accentuation of hinge curvature irrespective of R, when ζo > 1. However, for ζo ≤ 1, hinge-line curvature accentuates moderately when R < 8. It follows from our analysis that strongly non-cylindrical folds cannot develop unless the magnitude of initial hinge-line irregularity is sufficiently large (i.e. ζo «1). We also discuss the implications of the numerical results for pure shear models in the analysis of sheath folds in shear zones

A Geospatial approach to determine Lake Depth and Configuration of Reingkhyongkine (Pukur Para) Lake, Rangamati Hill District, Bangladesh with Multi-Temporal Satellite data

Reingkhyongkine (Pukur Para) Lake is the largest hilly natural lake under Belaichhari Upazila in the Hill district of Rangamati, Bangladesh. Due to remoteness and rugged terrain this lake is never being investigated and not documented in the literature. This research is done following standard method and state-of-art-technology. As natural resource management foster sustainable development the present research is of immense importance. Global Positioning System (GPS) is used for water depth point positioning along with sounding techniques was used for water depth measurement. The highest and lowest depths are observed 145 m and 0.50 m respectively. The worldwide available Landsat 8 OLI/TIRS imagery of 13 May 2015 was considered as the base imagery to know the lake area at present context compare with other different years. The Lake depth and 3D configuration maps are developed based on field depth and derived contour data. In addition to this, surface elevation profile in different direction of lake and bathymetric mapping based on longitudinal and horizontal transect bottom topographic profile, lake surface area and water volume are also calculated to understand the real scenario of this largest lake. All these studies are integrated with local as well as the regional geological structures. The study using geo-integrated technology on Reingkhyongkine lake reveals that the changes of lake area which is 35.02 hectare (May 2015 Landsat 8 OLI Imagery), 40.65 hectare and 34.91 hectare (2010 and 1989 Landsat TM imagery) respectively which indicate an decreasing-increasing-decreasing trend scenario and changing at the rate of 0.11 percent per year and this changing phenomenon is related with the active tectonism of the area as the study area has suffered extensive thrusting, faulting and folding. Besides this the surface elevation of lake is not similar and it varies from 353 meter to 409 meters. Results shows that changes in the configuration and reduction of water volume of Reingkhyongkine Lake establish fragile conditions which indicate of its future drying status and needs continuous monitoring of water depth by considering environmental factors which are involved for the lake changes and finally researcher seeks urgent attention to international scientific community for protection and conservation of this hilly natural lake