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

Ashok Sahni ¹

Affiliations
1 Panjab University, Chandigarh 160014, IN

Abstract

No Abstract.

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Ashok Sahni ¹, Sunil Bajpai ¹

Affiliations
1 Centre of Advanced Study in Geology, Panjab University, Chandigarh 160014, IN

Abstract

Recent data based on microvertebrates and associated microfossils suggest that the Lameta and coeval formations of Peninsular India are younger (Maestrichtian) than ages previously assigned to them (Cenomanian-Turonian). Similarly, the Takli and their intertrappean correlatives in several localities have yielded dinosaurian elements indicating thereby a Cretaceous rather than Tertiary age. Furthermore, no exclusively Tertiary taxa has been recorded from these beds at Nagpur, Asifabad, Kachchh and adjoining areas. Samples collected for palaeomagnetic studies with reference to vertebrate-bearing horizons suggest that the Deccan basaltic activity was initiated in the Late Maestrichtian at the end of Lameta times. The major part of the eruption took place during the reversed magnetic chron, 29R, which encompasses the Cretaceous-Tertiary Boundary. Radiometric dates (K/Ar, ⁴⁰Ar/³⁹Ar) tend to cluster in a 60 m.y. 70 m.y. interval. The Deccan traps have been cited as a possible alternative source of Ir enrichment in comparison to the hypothesis which ascribes the anomalously high values of this element at the KTB to an extra-terrestrial impact. The gradual decline of dinosaurs as well as other marine plankton and benthos towards the close of the Cretaceous favours hypotheses that do not advocate 'instantaneous' global mass extinctions.

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Ashok Sahni ¹, S. K. Shah ², K. R. Gupta ³

Affiliations
1 Centre of Advanced Studies in Geology, Panjab University, Chandrgarh, IN
2 Post Graduate of Department of Geology University of Jammu, Jammu, IN
3 Department of Science and Technology New Delhi, IN

Abstract

No Abstract.

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Sunil Bajpai ¹, S. Srinivasan ², Ashok Sahni ³

Affiliations
1 Department of Earth Sciences University of Roorkee, Roorkee-247667, IN
2 Department of Geology, Bangalore University, Bangalore-560056, IN
3 Department of Geology, Panjab University, Chandigarh-160014, IN

Abstract

Chelonian fossil eggshell fragments are reported from the Late Cretaceous Infratrappean beds near Duddukuru, West Godavari District, Andhra Pradesh.

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Ashok Sahni ¹

Affiliations
1 CAS in GeoLogy, Panjab University, Chandigarh - 160014, IN

Abstract

No Abstract.

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Ashok Sahni

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No Abstract.

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M. K. Bera ¹, Kasturi Bhattacharya ¹, A. Sarkar ², A. Samanta ², Kishor Kumar ³, Ashok Sahni ⁴

Affiliations
1 Department of Geology and Geophysics, Indian Institute of Technology, Kharagpur - 721 302, IN
2 Department of Geology and Geophysics, Indian Institute of Technology, Kharagpur -721 302, IN
3 Wadia Institute of Himalayan Geology, Dehradun - 248 001, IN
4 Centre of Advanced Study in Geology, Panjab University, Chandigarh - 160 014, IN

Abstract

Oxygen isotope composition (δ¹⁸O) of fossil bone and tooth enamel phosphate (bioapatite) is an important tool for estimating the isotopic composition of past environmental water. Lack of analytical facility was a hindrance for studying such bioapatites in spite of large number of fossil materials reported from various geological ages in India. We have established in our laboratory, based on available methods, the chemical procedure for extraction of very small amount (<1000 μg) PO₄ ^-3 from bioapatite and on-line mass spectrometric measurement of its δ¹⁸O composition by high temperature (∼1450 °C) pyrolysis. The achieved precision is ∼± 0.3 ‰ similar to obtained elsewhere, with interlaboratory calibration showing excellent agreement of standard phosphates. Inferred δ¹⁸O values of environmental water, based on the analysis of teeth and bones of sharks, fish and terrestrial mammals from the Paleogene successions of the northwest sub-Himalayan and the Peninsular India show strong correspondence with animal habitats. The freshwater δ¹⁸O values are much depleted having range similar to modern monsoon precipitation. However, owing to our small dataset it is not possible at this stage to infer about the existence of monsoon over the Indian sub-continent during the Eocene-Oligocene time.

Keywords

Phosphate, Pyrolysis, Oxygen Isotope, Monsoon.

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Ashok Sahni ¹, Sushil Kumar Khare ¹

Affiliations
1 Department of Geology, Lucknow University, IN

Abstract

Insectivores of very small size (Siwalikosorex prasadi) is being reported for the first time from the Siwalik sediments.

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