Shift in detrital sedimentation in the eastern Bay of Bengal during the late Quaternary

Down-core variations of granulometric, geochemical and mineral magnetism of a 70-cm long sediment core retrieved from the eastern Bay of Bengal abyssal region were studied to understand sedimentation pattern and sediment provenance during the last ～12 kyr BP. Based on down-core physical and elemental variations, three units were identified: unit 3 (70–43 cm) is a ～30 cm thick clayey silt organic carbon-rich (0.5–0.92%) turbidite probably delivered by the Brahmaputra River during the late Quaternary period. Units 2 (43–24 cm) and 1 (24–0 cm) represent enhanced and reduced supply of coarse-grained detrital sediments from the Ganges River during early and late Holocene period, respectively. Increased terrigenous supply dilutes calcium carbonate (CaCO₃) and biogenic elements (P, Ba and Cu) in units 3 and 2. On the contrary, a reduction in detrital input enhances CaCO₃ and biogenic elements in unit 1. Lithogenic elements (Ti, Al, K and Rb) and shale-normalized REE patterns in all three units suggest terrigenous source. The shift in provenance from the Brahmaputra to the Ganges derived sediments is evident by a sharp increase in sediment grain size, increased concentration and grain size assemblages of magnetic minerals, lithogenic elements concentration and La_n/Yb_n ratio. This study highlights terrigenous dilution on biogenic sedimentation in the eastern Bay of Bengal sediments.     

Pyrolytic and spectroscopic studies of Eocene resin from Vastan lignite Mine,Cambay basin,Western India

The molecular structure of an Eocene fossil resin (Vastan, Cambay basin, Western India) has been investigated with complimentary spectroscopic techniques. The FTIR spectrum shows strong aliphatic CH _x (3000–2800 and 1460–1450 cm⁻¹) and CH₃ (1377 cm⁻¹) absorptions and less intense aromatic C=C (1560–1610 cm⁻¹) absorptions. The major products from analytical pyrolysis are cadalene based bicyclic sesquiterpenoids including some bicadinenes and bicadinanes. The polycadinane products confirm the fossil material as an Angiosperm dammar resin, associated with inputs of tropical rain forests supported by past climates.     

Groundwater study in the Piedmont zone of Mechi Mahananda interfluve in Darjiling district,West Bengal using remote sensing techniques

The Mechi-Mahananda interfluve is a transitional area between the hills and the plains and exhibits a wide range of topographical variations. The drainage system of the area has a close relationship with lithology and landforms. The rivers originating in the hills attain a braiding character and have well developed alluvial fans. Piedmont plain covers a large area and has high ground water potential. The river terraces and flood plains also have high potentialities of ground water targeting. Fluctuation of water table is very high in the upper piedmont plain dependent upon the proximity to the drainage lines.     

Multiple forecasts of kharif rice in orissa state-four year experience of fasal pilot study

Considering the requirement of multiple pre-harvest crop forecasts, the concept of Forecasting Agricultural output using Space, Agrometeorology and Land based observations (FASAL) has been formulated. Development of procedure and demonstration of this technique for four in-season forecasts for kharif rice has been carried out as a pilot study in Orissa State since 1998. As the availability of cloud-free optical remote sensing data during kharif season is very poor for Orissa state, multi-date RADARSAT SCANSAR data were used for acreage estimation of kharif rice. Meteorological models have been developed for early assessment of acreage and prediction of yield at mid and late crop growth season. Four in-season forecasts were made during four kharif seasons (1998-2001); the first forecast of zone level rice acreage at the beginning of kharif crop season using meteorological models, second forecast of district level acreage at mid growth season using two-date RADARSAT SCANSAR data and yield using meteorological models, third forecast at late growth season of district level acreage using three-date RADARSAT SCANSAR data and yield using meteorological models and revised forecast incorporating field observations at maturity. The results of multiple forecasts have shown rice acreage estimation and yield prediction with deviation up to 14 and 11 per cent respectively. This study has demonstrated the potential of FASAL concept to provide inseason multiple forecasts using data of remote sensing, meteorology and land based observations.     

Wheat crop classification using multidate IRS LISS-I data

Multi temporal dat acquired at different growth stages increases the dimensionality information content and have advantage over single date data for crop classification. Attempt was made to select suitable single date and combination of multidate data for wheat crop classification in Nalanda district of Bihar state where pulses and other crops are also grown in rabi season. Amongst the single date data February data was found to be better for wheat classification in comparison to November. January, March and April data. Combination of first two principal components each derived from IRS LISS-I four band data acquired in January and February was found to be the best set. Wheat classification accuracy achieved was 94.54 percent.     

Optimization of spread configuration for seismic data acquisition through numerical modeling in tectonically complex areas: a case study from Badarpur anticline, Cachar, India

Cachar area, a part of the Assam–Arakan frontal fold belt in the eastern part of India is characterized by a series of narrow anticlines which are dissected by a number of faults including thrusts, and broad synclines. Out of several exposed structures, Badarpur anticline is most important because of its major share of hydrocarbon strikes in Cachar. However, the seismic image of this area so far has been extremely poor for deciding locations for exploratory drilling. The problems in obtaining a good seismic image in this area include proper spread configuration including far and near offsets to capture reflected signals from the complex subsurface, variation of charge-sizes and depths along a line, large variation in statics due to rapid changes in elevation and near surface properties. The presence of coherent noise due to scattering and proper migration are major processing problems. This paper deals with the problem of spread configuration. For areas of complex subsurface, spread configuration obtained through field experiment at one spot may be quite different from other spots, requiring a large number of costly experiments. In this work, therefore, we used numerical modeling to derive an optimum spread configuration. For this, we chose a line passing through four wells on Badarpur anticline, and prepared a depth model using available seismic, surface geological and well data. Continuous synthetic common shot records were generated through oblique incidence ray tracing and were processed to obtain stacks with various spread configurations. Comparison of these stacks of synthetic data shows that end-on shooting configuration is inadequate for acquiring a good seismic image of the complex subsurface. From the present study it is evident that a split–spread configuration with near and far offsets of 50 m and 2400 m, respectively, can bring out optimum seismic images in Badarpur and other anticlines in this area.     

Electrical resistivity and seismic refraction studies for groundwater in the Jodhpura area,Rajasthan

Summary The results of geophysical investigations carried out for groundwater employing seismic refraction and electrical resistivity methods near Jodhpura (27^o4730N:75^o4240E) in the Jhunjhunu District, Rajasthan, are presented. Prominent resistivity low zones, revealed by the resistivity profiles, are indicative of deeper section of unconsolidated sediments overlying the bedrock and are usually favourable locations for groundwater. An equiresistivity and water-level contour map based on well data is furnished, indicating the fresh water zone boundary deduced geophysically. Longitudinal velocities for the various rock types occurring in and around the area are tabulated for general interest. A bedrock map prepared on the basis of depths estimated geophysically is incorporated. The depths to bedrock computed from electrical and/or seismic data compare well with those obtained from borehole data.     

District wise yield models of rice in Bihar based on water requirement and meteorological data

Pre-harvest crop production forecast has been successfully provided by remote sensing technique. However, the probability to get cloud-free optical remote sensing data during kharif season is poor. Microwave data having the capability to penetrate cloud is used in the absence of cloud free optical remote sensing data. Yield models in broad band frequency range are in development stage. Meteorological yield models are developed and predicted yield is combined with area estimated by remote sensing data to provide rice production forecast. This paper describes the methodology adopted for improving the predictability of rice yield before harvest of the crop in Bihar province by taking into consideration meteorological parameters during its growth cycle upto October. Models developed using fortnightly meteorological data have been found to give reasonably fair indications of expected yield of rice in advance of harvest. The yield predictions have been made based on meteorological data and effective rainfall based on water requirement calculations representing a group of districts under similar agro-climatic zones, which could be further improved by incorporating meteorological data of individual districts within each group.     

Characteristics of atmospheric turbulence in the surface layer over Antarctica

This paper presents meteorological measurements made during the antarctic summer period, on two 9 m and 3 m towers, on the rocky and ice shelf terrains of the Indian antarctic stations Maitri and Dakshin Gangotri, respectively. The measurements of fluctuations in temperature and wind speed made with relatively lesser precision instrumentation pertain to smaller wave numbers ~10^-2 m^-1 appropriate to outer scale L ₀ of the atmospheric turbulence spectrum. Autocorrelation analysis of the fluctuations in temperature and wind speed has been performed. A new autoregressive scheme has been developed to represent the computed autocorrelation functions by a Yule statistical model, and to estimate the correlation period T ₀ of the turbulent medium. Height profiles of outer scale L ₀ of turbulence may be given in terms of T ₀ and mean wind speed u. Further, the similarity theory of Monin-Obukhov has been used to compute height profiles of temperature structure parameter C _T ². At Maitri, values of L ₀ and C _T ² are higher between 03–22 h local time than between 22–03 h. Values of L ₀ and C _T ² are smaller over the ice shelf terrain of the Dakshin Gangotri station, compared to those over the rocky terrain of the Maitri station.     

On the propagation of Love waves in a non-homogeneous internal stratum of finite depth lying between two semi-infinite isotropic media

Summary The possibility of propagation of Love waves in a non-homogeneous internal stratum of finite depth lying between two semi-infinite isotropic media has been studied in this paper. The density and rigidity of the internal stratum are taken to vary exponentially with depth.