PALEOMAGNETISM AND MAGNETOSTRATIGRAPHY OF THE UPPER CRETACEOUS AND CRETACEOUS-PALEOGENE BOUNDARY DEPOSITS IN THE SOUTH OF THE KULUNDA BASIN (West Siberia)
Z.N. Gnibidenko1, A.V. Levicheva1, N.N. Semakov1,2, G.G. Rusanov3
1A.A. Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences, pr. Akademika Koptyuga 3, Novosibirsk, 630090, Russia
2Novosibirsk State University, ul. Pirogova 2, Novosibirsk, 630090, Russia
3Gorno-Altaisk Expedition, ul. Sovetskaya 15, Maloeniseiskoe, 659370, Russia
Keywords: Paleomagnetism, magnetostratigraphy, ortozone, reversal, Upper Cretaceous, Lower Paleogene, South of the Kulunda basin, West Siberia
Subsection: STRATIGRAPHY
Abstract
We discuss the results of paleomagnetic studies of the Upper Cretaceous and Cretaceous-Paleogene boundary deposits in the south of the Kulunda basin (Alei area). Cores of two boreholes with a total thickness of 305 m were studied. Based on the revealed characteristic component of natural remnant magnetization (ChRM) in the studied deposits, we constructed paleomagnetic columns for each borehole and compared the borehole sections. Using the paleomagnetic, geological, stratigraphic, and paleontological data, we compiled the magnetostratigraphic section of the Upper Cretaceous and Cretaceous-Paleogene boundary deposits in the south of the Kulunda basin and recognized five magnetopolar zones within it: one of direct polarity and four of reverse polarity (Upper Cretaceous and Lower Paleogene deposits). The lower part of the Gan’kino Horizon, of direct polarity, forms one magnetozone of direct polarity N , and the upper part forms two magnetozones of reverse polarity, R 1km and R 2mt. The Lower Paleogene Talitsa and Lyulinvor Formations form two magnetozones of reverse polarity, R1zl and R2i. The compiled magnetostratigraphic section of the Upper Cretaceous and Lower Paleogene deposits is juxtaposed with the magnetochronological scale. Two variants of juxtaposition of the lower directly magnetized part of the section with the Gradstein scale are considered.
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