SOUTHERN SIBERIAN PLATFORM: RECORD OF NON- SYNCHRONOUS NRM-COMPONENTS OR A NON-AXIAL GEOMAGNETIC FIELD?

• Main Authors: Ordovician Krivolutsky Suite, Krivaya Luka Section, V. P. Rodionov, C. E. Duermeijer, D. Heslop
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: North Pole; lena river; Siberia
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.581.9374; http://www.geo.uu.nl/~forth/publications/Rodionov_2003.pdf

The Middle Ordovician Volginsky and Kirensky fossil zones were sampled in the Krivaya Luka section (Krivolutsky suite) that outcrops along the Lena river in Siberia. The Volginsky and Kirensky zones are coeval to the Llandeilo in the global geologic time scale. The Krivaya Luka section consists of siltstones, clays, sandstones, and limestones, and displays a remarkably distinct sedimentary cyclicity, especially in its reddish middle part. Stepwise thermal demagnetization yields three NRM components. Component A, isolated in the 100−250°C interval can be either normal or reversed. The normal A-component has a direction close to recent local magnetic field. The reversed A-component directions are scattered around a direction close to that of the lower Triassic Siberian traps. Component B, has unblocking temperatures that range from 400 to 500°C and is represented mainly by normal polarity directions. The B-component, isolated from rocks of the middle part of the section is of a normal polarity with D = 176.5°, I = 30.0 ° and a North pole position at 16.2°S, 111.3°E. The other parts of the