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Sequence stratigraphy of the Opalinuston-Formation in Southern Germany

The Opalinuston-Formation in Southern Germany comprises a thick (>100 m) sequence of Middle Jurassic claystones. In parts of Bavaria and Baden-Württemberg, the formation has been designated as a sub-area by the Federal company for radioactive waste disposal (BGE), indicating that favorable geological conditions for the final disposal of high-level radioactive waste can be expected there. However, coherent geological data for the complete formation is often lacking. Here we present new data on the geological variability of the Opalinuston-Formation based on four drill cores, each of which penetrated through the entire formation, and parts of the over- and underlying rock strata outside the sub-area. After completion of the drilling work, the cores were examined in high resolution for their petrophysical properties and element distribution using non-destructive analytical tools such as XRF core scanner and multi-sensor core logger. Furthermore, one sample per core meter was taken for a precise stratigraphic classification of the rocks and a geochemical-mineralogical and sedimentological characterization. Results exhibit notable geological variability at the investigated localities, particularly with respect to the Si/Al ratio. This is interpreted as changes in grain size due to relative sea-level fluctuations during deposition, and is thus useful to reconstruct stacking patterns of parasequences. In summary, this contribution highlights the geological variability of the Opalinuston-Formation in Southern Germany and discusses the possibilities of a sequence stratigraphic approach to identify the most suitable parts of sub-areas in claystone formations for the final disposal of high-level radioactive waste.

Details

Author
Thomas Mann1, Tilo Kneuker1, Géraldine Nicole Zimmerli2, Jochen Erbacher3, André Bornemann1, Bernhard Schuck1, Reiner Dohrmann3, Lukas Pollok1
Institutionen
1Bundesanstalt für Geowissenschaften und Rohstoffe (BGR), Hannover Germany; 2Department of Geosciences, University of Fribourg, Switzerland; 3Bundesanstalt für Geowissenschaften und Rohstoffe (BGR), Hannover Germany;State Authority for Mining, Energy and Geology (LBEG), Hannover, Germany
Veranstaltung
GeoSaxonia 2024
Datum
2024
DOI
10.48380/b1nt-mp29
Geolocation
Germany