Enigmatic mixture of magnetite magnetofossils and diagenetic greigite as the magnetic carriers of the Early Miocene lacustrine sediments from the Most Basin in Central Europe
Hakan Ucar , Gunther Kletetschka , Ramon Egli , Karel Mach , Michael S. Petronis , Hana Grison , Stephanie Scheidt , Petr Schnabl , Simon Kdyr
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引用次数: 0
Abstract
The Early Miocene lacustrine sediments of the Most Basin in the Czech Republic preserve a European continental paleoenvironmental archive. A number of paleoenvironmental and magnetostratigraphic studies have been carried out on sediment cores from boreholes due to ongoing coal mining in the basin. However, the magnetic carriers of the studied sediments have not been identified clearly. Here, we present a detailed paleo-rock magnetic study from the Burdigalian sediments near the Bilina mining area, Most Basin. The studied clay sediments cover the period of local lakes and a basin-wide lake above the main coal seam. Our results suggest that the magnetic carriers of the studied section in the Most Basin are mixtures of authigenic greigite and magnetite magnetofossils with overlapping magnetic signatures. Greigite is formed by migration of pore water through the sediment column, where iron from siderite grains reacts with these fluids with limited H2S, which then favors greigite precipitation. The co-existence of greigite and magnetite indicates a partial dissolution of magnetofossils due to H2S deficiency. Diagenetic greigite has been problematic in paleomagnetic studies due to an unknown time lag between the depositional remanence and the chemical remanent magnetization (CRM). A ghost polarity interval reveals that greigite acquired at least ∼45 kyr delayed CRM. The revealed timing of remanence acquisition brings a new perspective to the chronostratigraphic structure of the Most Basin.
期刊介绍:
Launched in 1968 to fill the need for an international journal in the field of planetary physics, geodesy and geophysics, Physics of the Earth and Planetary Interiors has now grown to become important reading matter for all geophysicists. It is the only journal to be entirely devoted to the physical and chemical processes of planetary interiors.
Original research papers, review articles, short communications and book reviews are all published on a regular basis; and from time to time special issues of the journal are devoted to the publication of the proceedings of symposia and congresses which the editors feel will be of particular interest to the reader.