Magnetostratigraphy of the lower Triassic volcanics from deep drill SG6 in western Siberia: evidence for long-lasting Permo–Triassic volcanic activity |
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Authors: | Michel Westphal Evgueni L Gurevitch Boris V Samsonov Hugues Feinberg & Jean Pierre Pozzi |
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Institution: | Ecole et Observatoire des Sciences de la Terre and UMR CNRS-ULP 7516, Institut de Physique du Globe, 5 rue R. Descartes, F 67084 Strasbourg Cedex, France,;VNIGRI, Laboratory of Palaeomagnetism and Palaeoreconstructions, Liteiny 39, 191104 St Petersburg, Russia,;Ecole Normale Supérieure, Laboratoire de Géologie and URA 1316, 24 rue Lhomond, 75231 Paris Cedex 05, France |
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Abstract: | The deep drill hole SG6 in western Siberia (66°N, 78.5°E) penetrated 1.1 km of lower Triassic basalts, which are possibly an extension of the central Siberian Permo– Triassic flood basalt province. About 300 samples of these basalts were progressively demagnetized and measured. Principal component analysis often shows multiple magnetizations carried by haematite and magnetite. The corrected mean inclinations are +77° and ?77° for the haematite component. A magnetostratigraphic scale was derived and showed a N–R–N–R–N succession. This is quite different from the Noril'sk and Taimyr typical polarity scale, R–N. The basalts found in the SG6 deep drill hole are slightly younger than those of central Siberia and Taimyr. They correspond to middle–upper Induan age, whereas the Noril'sk and Taimyr sections correspond to an uppermost Permian and lower Induan age. Altogether they indicate that, after a high output rate of volcanic material near the Permo–Triassic boundary, this activity slowed down drastically on the Siberian platform and Taimyr, but persisted for several million years in western Siberia. |
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Keywords: | magnetostratigraphy palaeomagnetism Permian Triassic western Siberia |
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