Two-dimensional Crustal Velocity Structure along Hirapur-Mandla Profile from Seismic Refraction and Wide-angle Reflection Data

—The seismic velocity structure of the upper and lower crusts along Hirapur-Mandla pro|fi|le was obtained by 2-D forward modeling of the refraction and wide-angle reflection data. Digitized record sections of the analog data were utilized for delineation of the crustal velocity model across the Vindhyan basin and the Narmada-Son lineament by travel-time modeling and qualitatively matching the amplitudes of synthetic seismograms with seismic record sections. An interface at a depth of 8 km has been traced from wide-angle reflection data of shot points 160 and 235 between Jabalpur and Mandla. The wide-angle reflection phase from crust-mantle boundary is very prominent in all the seismic record sections of shot points 0, 40, 80, 120 and 235. The Moho horizon along the entire study area was continuously traced, depicting an upwarp between Katangi and Jabalpur below the Narmada-Son lineament. The three faults inferred near Narsinghgarh, Katangi and Jabalpur divide the crust into four blocks. The number of faults and displacement patterns along them, depicted along the profile, indicates that block tectonics appear to be active in this region throughout the geological history.     

Impact of Climate Change on Indian Agriculture: A Review

During the recent decade, with the growing recognition of the possibility of climate change and clear evidence of observed changes in climate during 20^th century, an increasing emphasis on food security and its regional impacts has come to forefront of the scientific community. In recent times, the crop simulation models have been used extensively to study the impact of climate change on agricultural production and food security. The output provided by the simulation models can be used to make appropriate crop management decisions and to provide farmers and others with alternative options for their farming system. It is expected that in the coming decades with the increased use of computers, the use of simulation models by farmers and professionals as well as policy and decision makers will increase. In India, substantial work has been done in last decade aimed at understanding the nature and magnitude of change in yield of different crops due to projected climate change. This paper presents an overview of the state of the knowledge of possible effect of the climate variability and change on food grain production in India. An erratum to this article can be found at     

Coexisting plagioclases from basic charnockites of India

Plagioclases of widely different compositions are found to coexist in basic charnockites of India. This may be due to structural discontinuities or difficult and slow substitution of Si/Al in tetrahedral sites. The presence of hydrous environment in making plagioclases homogeneous is discussed.     

Possibilities of oil shale mining under the Selisoo mire of the Estonia oil shale deposit

The paper presents results of the study on oil shale mining (Estonia underground mine) possibilities under the Selisoo mire. The Selisoo area is 2,051 ha in extent, and most of the mire is in natural state. Peat layer consists of thick (4.4–6.5 m) oligotrophic peat. Mining under Selisoo will go at depths 65–70 m under the surface. The mining field of the Estonia mine was planned between Ahtme and Viivikonna fault zones. The lowest hydraulic conductivity of carbonate rocks 0.11 l/day per m² is found in the Oandu layer and for peat it is 0.35–0.0002 m/day. Therefore, together they form a good aquitard. When the annual rainfall amount is the highest, the difference between horizontal water inflow and runoff is positive with 127,000 m³. Positive water balance is guaranteed in case of precipitation being at least 540 mm/year. The positive water balance is important for preserving the ecological system of Selisoo mire. For guaranteeing long-term stability of mine pillars, a new calculation method has been elaborated, based on the conventional calculation scheme, where the factor of safety is more than 2.3. Rheological processes are out of question, collapse of the pillars is impossible. Stability of the underground constructions and overburden rocks must be “eternal”. The criteria were elaborated for oil shale mining and will guarantee preservation of mires in natural or close to natural state.     

Climate Change and Rice Yields in Diverse Agro-Environments of India. I. Evaluation of Impact Assessment Models

This paper reports results of a comparison of two popular rice growth models- Ceres-Rice and ORYZA1N for the same input conditions. Both models use different approaches for simulating growth and yield, are sensitive to climate change parameters, and represent two major schools of crop modelling. A dataset of 32 experiments consisting of 98 treatments was assembled from an extensive literature search. These experiments were conducted over the period of 1980–1993 in diverse Indian locations from 11° N–33° N. The treatments varied in N management, sowing dates, varieties and seasons. The flowering duration in the dataset varied between 37 and 86 days and grain yields between 2587 kg ha^–1 and 8877 kg ha^–1. Seven treatments from this dataset, one for each variety, were selected for calibration. The genetic coefficients of different varieties used in the analysis for both models were estimated from this short-listed dataset by repeated iterations until a close match between simulated and observed phenology and yield was obtained in these treatments. Similarly 11 treatments with zero or low N applications were used for calibration of initial soil N for different locations. The remaining 80 treatments were used for validation of the models. Both models predicted satisfactorily the trends of leaf area and dry matter growth, grain number, days to flowering and grain yields. Simulated yields were within +15% of the measurements. Considering that the field measurements also generally have 10–15% error and that the treatments widely varied in weather conditions, particularly in temperature, it was concluded that both models are adequate to simulate the effects of climate change on rice yields in diverse agro-environments of India that are free from all pests.     

Studies in the system KAlSiO4-BaAl2Si2O8-SiO2-H2O

Various members of the KAlSi₃O₈-BaAl₂Si₂O₈ feldspar series are hydrothermally synthesized. Cellparameters of these are calculated from diffractometer patterns and found to be similar to those of Gay and Roy. A variation diagram is constructed correlating Cn-content and values of Δ_FeKα(2θ₍₁₁₁₎CaF₂—2θ₍₀₀₄₎Fs_ss), which gives $${\text{Mol}}\% {\text{ Cn = 229}}{\text{.83}}\Delta {\text{2}}\theta ---{\text{190}}{\text{.81}}$$ by a least square regression fitting. Phase equilibria relation in the solidus-liquidus-region for the KAlSi₃O₈-BaAl₂Si₂O₈-H₂O system at 1000 kg/cm² are investigated. It is found to be a case of simple solid solution in a binary system, with reservations at the potassium-rich side of the system. Goranson (1938) gives a temperature of about 1000°C at 1000 kg/cm² \(P_{{\text{H}}_{\text{2}} {\text{O}}} \) for the incongruent melting of sanidine, but the authors prefer a value around 930°C at the same \(P_{{\text{H}}_{\text{2}} {\text{O}}} \) . Reaction products of starting materials on the join KAlSi₂O₆-BaAl₂Si₂O₈ and KAlSiO₄-BaAl₂Si₂O₈ gave no experimental hint for replacement of K⁺ by Ba⁺⁺.     

Tectonics and thermal structure of western Satpura,India

Increased seismicity and occurrences of hot springs having surface temperature of 36–58 °C are observed in the central part of India (74–81° E, 20–25° N), where the NE trending Middle Proterozoic Aravalli Mobile Belt meets the ENE trending Satpura Mobile Belt. Earlier Deep Seismic Sounding (DSS) studies along Thuadara-Sendhwa-Sindad profile in the area has showed Mesozoic Sediments up to around 4 km depth covered by Deccan Trap and the Moho depth with a boundary velocity (P_n) of 8.2 km/s. In the present study, surface heat flow of 48 ± 4 mW m^?2 has been estimated based on P_n velocity, which agrees with the value of heat flow of 52 ± 4 mW m^?2 based on Curie point isotherms estimates. The calculated temperature-depth profile shows temperature of 80–120 °C at the basement, which is equivalent to oil window temperature in Mesozoic sediments and around 570–635 °C at Moho depth of 38–43 km and the thermal lithosphere is about 110 km thick, which is comparatively higher than those of adjoining regions. The present study reveals the brittle–ductile transition zone at 14–41 km depth (temperature around 250–600 °C) where earthquake nucleation takes place.