MAGNETOSTRATIGRAPHY OF THE LOWER TRIASSIC VOLCANICS FROM DEEP DRILL SG6 IN WESTERN SIBERIA - EVIDENCE FOR LONG-LASTING PERMO-TRIASSIC VOLCANIC ACTIVITY

The deep drill hole SG6 in western Siberia (66 degrees N, 78.5 degrees E) penetrated 1.1 km of lower Triassic basalts, which are possibly an extension of the central Siberian Permo-Triassic flood basalt provinc e. About 300 samples of these basalts were progressively demagnetized and measured. Principal component analysis often shows multiple magnet izations carried by haematite and magnetite. The corrected mean inclin ations are +77 degrees and -77 degrees for the haematite component. A magnetostratigraphic scale was derived and showed a N-R-N-R-N successi on. This is quite different from the Noril'sk and Taimyr typical polar ity scale, R-N. The basalts found in the SG6 deep drill hole are sligh tly younger than those of central Siberia and Taimyr. They correspond to middle-upper Induan age, whereas the Noril'sk and Taimyr sections c orrespond to an uppermost Permian and lower Induan age. Altogether the y indicate that, after a high output rate of volcanic material near th e Permo-Triassic boundary, this activity slowed down drastically on th e Siberian platform and Taimyr, but persisted for several million year s in western Siberia.