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| Titel |
Chemostratigraphy of lacustrine siliciclastics: how to process 200 m of monotonous mudstones (Most Basin, Czech Republic, Early Miocene) |
| VerfasserIn |
T. Matys Grygar, K. Mach, T. Novakova, J. Laurin |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250062213
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| Zusammenfassung |
| In the W to NW of the Czech Republic there are remnants of sedimentary basins (Cheb,
Sokolov and Most Basins), which were part of the European Cenozoic Rift System. These
basins were filled during the Burdigalian in purely terrestrial environment. Extensive
peatlands (which produced economically important coal measures) in the Most Basin were
covered by whole-basin Libkovice Lake after increase of the basin subsidence, and finally the
lake covered more than 1000 km2. The sedimentation was terminated in the upper Early
Miocene probably shortly before the Middle Miocene climatic optimum (MMCO). The
resulting monotonous, siliciclastic, fossil-barren deltaic and lacustrine sediments have total
thickness of up to 250 m; there is no datable material in them and hence their age is based on
biostratigrahy of the basin fill. The detailed stratigraphy including correlation over the entire
Most Basin (dimensions about 20x50 km), has not yet been established. We have
started our research to extract its palaeoenvironmental information content from the
Most Basin. The first step of our work was a chemostratigraphic correlation of the
sediments obtained from five long cores (~200 m) provided by Severoceske doly (a
coal-mining company). We use EDXRF element analysis and chemical analysis by
ion exchange with [Cu(trien)]2+. Analysis of exchangeable/water soluble cations
revealed that the Libkovice Lake was freshwater with only moderately mineralized
water. Slight and smooth variations of major element content proved very stable
sedimentary environment. Variations in K/Al element ratio, changes in the expandable clay
mineral content (CEC), and Sr accumulations allow a detailed correlation of boreholes
from different parts of the basin. Three crandallite-containing horizons formed by
alteration of volcaniclastic fallouts (or mass flows) were found that supports our
chemostratigraphic correlation. Spectral analysis suggests that Sr and K/Al variations
possibly record orbitally driven changes in insolation. The orbital interpretation implies
sedimentation rates up to 16 - 20 cm/ky during the major lacustrine phase (Libkovice
Lake).. These sedimentation rates make it possible to obtain high-resolution data on
depositional, volcanic and climatic changes during the Early Miocene in Central Europe. |
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