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

A. Ranga Rao ¹, R. P. Agarwal ¹, U. N. Sharma ¹, M. S. Bhalla ², A. C. Nanda ³

Affiliations
1 Oil and Natural Gas Commission, Dehradun, IN
2 National Geophysical Research Institute, Hyderabad, IN
3 Wadia Institute of Himalayan Geology, Dehradun, IN

Abstract

Magnetic polarity stratigraphy of Upper Siwalik Subgroup, Jammu Hills was worked out based on partially demagnetized data from 208 sites in three sections: Parmandal-Utterbeni, Nagrota-Jammu and Balli. One/two bentonitized tuff horizons occur close to the base of a long reversed polarity zone associated with Pinjor age fossils. Fisson track dates of 2.8±0.56 m.y. and 2.31±0.54 m.y. have been obtained on the zircon phenocrysts from these tuffs. These data permit correlation of our magnetic stratigraphy with the standard magnetic polarity time scale. The longest sampled section spans the interval from 4.92 to 0.22 m.y. This dating places the lower part of Upper Siwalik in the early Pliocene.

In the sampled parts of the sections, the magnetic polarity zonation establishes 16 magnetozones in Parmandal-Utterbeni, 13 in Nagrota and one in Balli. Individual magnetic transitions can be correlated over a lateral distance of 62 km and these provide time lines for correlation of lithology from one section to the other.

Estimated rates of sedimentation indicate rates varying from 0-45 m to 0.71 m/l000 years for Gilbert and Gauss epochs, while a decreased rate varying from 0.21 m to 0.37 m/l000 years is indicated during the Matuyama epoch.

The ]ast folding event of Suruin-Mastgarh anticline is not older than 0.22 m.y. However, the decrease in the rate of sedimentation during post Gauss time could possibly be due to an earlier period of deformation.

A significant change in fauna near the Gauss-Matuyama boundary is observed by the appearance of Equus and cervids with antlers and by the absence of Hipparion. We correlate this boundary with the Tatrot-Pinjor faunal boundary, No change either in lithology or in the vertebrate fauna is observed at the Pliocene-Pleistocene boundary if it is to be placed at the top of the Olduvai Normal Subchron.

Full Text

     

B. K. Dey ¹, D. S. Mitra ¹, R. P. Agarwal ¹, S. F. Dotiwala ¹, D. N. Prasad ¹

Affiliations
1 Remote Sensing Lab., Keshava Deva Malaviya Institute of Petroleum Exploration, Oil and Natural Gas Corporation, Debra Dun - 248195., IN

Abstract

The satellite and ground based spectral data corresponding to the six reflected radiance bands of Landsat Thematic Mapper (TM) are analysed to determine their utility in mapping the possible lithologic variations wihtin the Siwalik sediments of J&K foothills. The satellite reflectance values plotted along a selected image profile identified subunits within the Lower Siwalik, Pammdal and Nagrota, which were not identified by conventional field mapping. The field reflectance studies also confirmed their presence. The variation may reflect a possible lithofacies change wihtin the units. The technique developed may provide a rapid reconnaissance tool for preparing lithofacies map.

Keywords

Spectral Signature, Siwalik, Landsat Thematic Mapper, Jammu and Kashmir.

Full Text