AbstractBasic volcanic rocks within the Zildat ophiolitic mélange of Indus suture zone in eastern Ladakh are medium to fine grained with partially preserved primary texture and mineralogy. These rocks are predominantly alkaline basalt with high Nb/Y and enriched incompatible trace element characteristics, similar to those of the oceanic island basalt (OIB). The minor sub-alkaline basaltic rocks resemble N-type mid ocean ridge basalt (N-MORB) but with much lower abundances of incompatible trace element including REE. The alkaline rocks probably generated through variable, but low degrees of partial melting of enriched mantle source and evolved through high pressure olivine and clinopyroxene fractionation. Low pressure plagioclase and Fe- Ti oxide do not appear to be major fractionating phases. Limited data on the sub-alkaline rocks suggest that their parental melts were derived from mantle sources some what similar to that of N- MORB. Significant role of added cumulates of olivine, clinopyroxene and Fe- Ti oxides is also indicated in their genesis. Ophiolitic mélanges all along the Indus suture zone appear to have formed due to the accumulation of mélange material in the upper part of the subduction zone where they suffered glaucophanitic (blueschist) metamorphism and retrograded partially to greenschist grade as these were subsequently obducted to its present position probably during the Cenozoic Himalayan orogeny due to collision of Indian and Eurasian plates. 相似文献
In this paper, an improvement has been made to the approximation technique of a complex domain through the stairstep approach to have a considerable accuracy, minimize computational cost, and avoid the hardship of manual work. A novel stair-step representation algorithm is used in this regard, where the entire procedure is carried out through our developed MATLAB routine. Arakawa C-grid is used in our approximation with (1/120)° grid resolution. As a test case, the method is applied to approximate the domain covering the area between 15°–23°N latitudes and 85°–95° E longitudes in the Bay of Bengal. Along with the approximation of the land-sea interface, coastal stations are also identified. Approximated land-sea interfaces and coastal stations are found to be in good agreement with the actual ones based on the similarity index, overlap fraction, and extra fraction criteria. The method can be used for approximating an irregular geometric domain to employ the finite difference method in solving problems related to long waves. As a test case, shallow water equations in Cartesian coordinates are solved on the domain of interest for simulating water levels due to the nonlinear tide-surge interaction associated with the storms April 1991 and AILA, 2009 along the coast of Bangladesh. The same input except for the discretized domain and bathymetry as that of Paul et al. (2016) is used in our simulation. The results are found to be in reasonable agreement with the observed data procured from Bangladesh Inland Water Transport Authority.
There is an on-going debate about climate-induced migration but little empirical evidence. We examine how climate-induced migration has impacted vulnerability and adaptation of a coastal fishing community in Bangladesh. We used household surveys, interviews and focus group discussions to compare fishery dependent households who migrated from Kutubdia Island to mainland with those who stayed behind. Our results suggest that the resettled households are less exposed to floods, sea-level-rise and land erosion than those who stayed behind. They also have more livelihood assets, higher incomes and better access to water supply, health and educational services, technology and markets. In our case study migration has thus been a viable strategy to respond to climate variability and change. 相似文献
This paper presents how faster two dimensional (2-D) tomography of soil layers is obtained in geotechnical characteristics through multi-channel analysis of surface wave (MASW) method. MASW is developed as a new technique incorporating multiple receivers and 2-D wave-field transformations to obtain better performance in surface wave analysis. Incorporating 2-D tomography technique with multi-channel analysis offers an efficient and cost effective technique in soil site investigations. In the previous research, the Geo-SW@T software was designed and developed with collecting a lot of records including programming array technique to show the 2-D tomography in near surface soil profiling. To make a 2-D tomography of soil profile based on the past planned MASW technique is time consuming for collecting large database through 2-D array of programming language. In this paper, a new idea is established to obtain faster performance in soil tomography profile using array and sub-array technique in MASW. The performance of newly developed tomography technique with MASW method is estimated as faster and important tomography system for using one single record in soil characterizations rather than arranging of multiple records. 相似文献
Different methods of lithology predictions from geophysical data have been developed in the last 15 years, among which the conventional logs are as follows: sonic, neutron–neutron, natural gamma, and density (backscattered gamma–gamma). This article concentrates on the nuclear geophysical suite, in particular, gamma and gamma–gamma logging, which, to date, provide the most accurate geophysical means of identifying coal seams and estimating their thickness. From the gamma and gamma–gamma logs of boreholes AEN 002, 007, 044, 045, 063, 085, and 105, which were carried out at the Phulbari Coal Basin of Bangladesh, two coal seams—upper and main with two lower seams of limited occurrence and of varying thickness—were identified, together with their regional occurrence. 相似文献