Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

B. Mishra ¹, K. L. Pruseth ¹, S. Sarkar ¹

Affiliations
1 Department of Geology and Geophysics, Indian Institute of Technology, Kharagpur 721302, IN

Abstract

Acanthite (Ag₂S), Stibnite (Sb₂S₃) and Boumonite (CuPbSbS₃) were synthesized by the evacuated silica tube method under dry conditions. Boumonite was synthesized both from its elemental composition and from the component sulfides. All the products were characterized by the optical and XRD methods and were found to be pure, homogeneous and direct semiconductors.

Diffuse reflectance studies were undertaken on these synthetic mineral phases. The forbidden energy gap (E_g) was calculated by α² vs. hν plots and linear extrapolation to α² = zero. E_g was also deduced by calculating the Kubelka - Munk remission function, and plotting it against the photon energy. The E_g values obtained were: acanthite 0.98, 1.0 eV; stibnite 1.50, 1.55 eV and boumonite 1.15, 1.23 eV. Possible industrial application of these syntheti∼ semiconducting mineral phases are discussed.

Keywords

Mineral Synthesis, Acanthite, Stibnite, Boumonite, Reflectance Spectroscopy.

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G. S. Mehrotra ¹, S. Sarkar ¹, D. P. Kanungo ¹, K. Mahadevaiah ¹

Affiliations
1 Central Building Research Institute, Roorkee-247 667, IN

Abstract

Landslides and slope instability problems are quite common in Sikkim Himalaya. Recent developmental activities in this region have aggravated the incidence of landslides to a great extent. The ongoing developmental activities, therefore, call for delineation of safe and unsafe zones.

The present study involves the preparation of landslide hazard zonation map of East Sikkim Himalaya in a semiquantitative way by evaluating various terrain factors like lithology, structure, slope, landuse and drainage in relation to existing landslides. A numerical weightage called Landslide Susceptibility Value (LSV) has been assigned to each factor and Landslide Susceptibility Index (LSI) of each category of factor maps has been catculated. Based on the proposed methodology landslide hazard zonation map of the area is prepared showing five zones of slope instability. This map may serve as a base map for any developmental activities to be planned in the terrain. An attempt has also been made to establish the relationships of various geoenvironmental factors with the landslide activity with an objective to develop an appropriate methodology for landslide hazard zonation.

Keywords

Landslides Hazards, Terrain Analysis, Sikkim Himalaya.

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J. Daneshian ¹, S. Sarkar ², V. Sharma ³

Affiliations
1 Department of Geology, Teacher Training University, No-49 Mofatteh Ave, Tehran, IR
2 Birbal Sahni Institute of Palaeobotany, 53 University Road, Lucknow - 226 007, IN
3 Department of Geology, University of Delhi, Delhi -110 007, IN

Abstract

A nch palynofloral assemblage has been recorded for the first time from a stratigraphc section of the Inglis Formation at Inglis Island, Andarnan Sea, India Forty-six genera and fifty eight species belonging to differen botanical groups viz , dinoflagellate cysts, fungal remains, ptendophytic spores, and gymnospermous and angiospermous pollen have been recognized Geological ranges of some stratigraphically important palynotaxa suggest late Early Mioceneearly Middle Miocene age to the assemblage The recorded palynofloral assemblage is also closely comparable to that recorded horn late Early Miocene-Early Middle Miocene sediments of South Indla The palynoflora has been compared with the modem equivalents and it indicates a warm humid climate with high degree of rainfall during the deposition of the sequence In the area of investigation.

Keywords

Palynoflora, Late Early Miocene-Early Middle Miocene, Palaeoecology, Inglis Island, Andaman Sea

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S. Sarkar ¹, Pravin K. Gupta ²

Affiliations
1 central Building Research Institute, Roorkee - 247 667, IN
2 Indian Institute of Technology Roorkee, Roorkee - 247 667, IN

Abstract

The present work deals with the development and evaluation of landslide hazard zonation techniques which have been applied to parts of Garhwal Himalaya. The binary relationships between the factors and landslides have been Detel-Mined. These relationships revealed the degree of susceptibility to landslide occurrence. The two techniques developed for landslide hazard zonation are the subjective Rating Technique (SRT) and Objective Rating Technique (ORT). Although the SRT employs the inferred relationships between the landslide occurrence and the terrain factors to assign ratings to the factor categories, yet the rating assignment to the individual factors is subjective. The ORT reduces the impact of subjectivity in rating assignment, by deriving these from the frequency distribution of landslides. In this technique an attempt has also been made to judiciously classify the different hazard classes. Finally, the maps prepared from two different techniques have been validated and compared. The work presents a systematic approach to n comprehensive landslide hazard assessment of a large region.

Keywords

Landslide, Susceptibility, Hazard Zonation, Garhwal Himalaya.

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N. Harijan ¹, A. K. Sen ¹, S. Sarkar ², J. D. Das ³, D. P. Kanungo ²

Affiliations
1 Department of Earth Sciences, IIT Roorkee, Roorkee - 247 667, IN
2 Central Building Research Institute, Roorkee - 247 667, IN
3 Earthquake Engg., IIT Roorkee, Roorkee - 247 667, IN

Abstract

Sung Valley Carbonatite Complex (SVCC) of the Shillong Plateau is one of the important known carbonatite complexes in India. This complex has intruded the sub-vertical beds of Shillong Group rocks and occur along the major N-S trending pre-existing Um Ngot fault. Topographically, the carbonatite intrusion is marked by a prominent semi-circular depression formed due to weathering of soft nature of the rocks present in the complex. This characteristic is unique in relation to carbonatite and related rocks with the surrounding relatively hard lithological formations. This < feature is prominently displayed on satellite image. The drainage network of the study area is found to be strongly controlled by structure and lithology. The present study is an attempt towards morphotectonic interpretation of the SVCC and adjoining region using satellite imagery and spatial data integration in GIS environment.

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