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

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A Jurassic-Cretaceous Dolerite Dike from Sri Lanka


Affiliations
1 Department of Geosciences, Faculty of Science, Osaka City University, Sugimoto, Sumiyoshi-ku, Osaka 558, Japan
2 National Institute of Polar Research, Kaga, ltabashi-ku, Tokyo 173, Japan
3 Department of Geology, University of Peradeniya, Peradeniya, Sri Lanka
     

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A dolerite dike from southwestern Sri Lanka gave whole-rock K-Ar ages of 152.6 ± 7.6 Ma and 143.3 ± 7.2 Ma. Many of the other dolerite dikes of Sri Lanka are considered to be of Mesozoic ages judging from the present age data and tectonometamorphic history of Sri Lanka. Petrographic similarities should not be used for age correlations, because dolerites of different age may have the same petrography.

Preliminary natural remanent magnetization (NRM) after AF and thermal demagnetization gave a mean inclination of 24.6° and declination of 67.5° with α95=21.7°. A virtual geomagnetic pole position calculated from the mean NRM was rotated relative to Antarctica so as to fit with that obtained from the Jurassic Ferrar dolerite of Antarctica. This rotation results in the location and attitude of Sri Lanka to attach with Antarctica at Lutzow-Holm Bay as suggested by Barron et al. (1978).


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  • A Jurassic-Cretaceous Dolerite Dike from Sri Lanka

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Authors

M. Yoshida
Department of Geosciences, Faculty of Science, Osaka City University, Sugimoto, Sumiyoshi-ku, Osaka 558, Japan
M. Funaki
National Institute of Polar Research, Kaga, ltabashi-ku, Tokyo 173, Japan
P. W. Vitanage
Department of Geology, University of Peradeniya, Peradeniya, Sri Lanka

Abstract


A dolerite dike from southwestern Sri Lanka gave whole-rock K-Ar ages of 152.6 ± 7.6 Ma and 143.3 ± 7.2 Ma. Many of the other dolerite dikes of Sri Lanka are considered to be of Mesozoic ages judging from the present age data and tectonometamorphic history of Sri Lanka. Petrographic similarities should not be used for age correlations, because dolerites of different age may have the same petrography.

Preliminary natural remanent magnetization (NRM) after AF and thermal demagnetization gave a mean inclination of 24.6° and declination of 67.5° with α95=21.7°. A virtual geomagnetic pole position calculated from the mean NRM was rotated relative to Antarctica so as to fit with that obtained from the Jurassic Ferrar dolerite of Antarctica. This rotation results in the location and attitude of Sri Lanka to attach with Antarctica at Lutzow-Holm Bay as suggested by Barron et al. (1978).