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First U-Pb zircon age of a tuff horizon in the early Late Cretaceous Lengerich Formation of the Münsterland Basin

The Late Cretaceous succession of the Münsterland Basin is up to 2,000 m thick and comprises mainly limestone, marlstone and chalk. As flooding came from the north, siliciclastic coastal sediments dominate along the southern margin. Several large limestone quarries in the area of Lengerich at the today´s northern basin margin give detailed insights into distal Early to Late Turonian deposits (Hiss et al. 2007). These marine sediments were uplifted, folded and overturned along the Osning Fault Zone. Wiese & Kaplan (2004) argued to use the good quality exposures as Global Boundary Stratotype Section and Point (GSSP).

The Dyckerhoff quarry near Lengerich-Hohne in the SW Teutoburg Forest show intercalations of thin marly limestone and marlstone beds of the Lengerich Formation, which is part of the Upper Plänerkalk Subgroup. A few altered tuff horizons (TD1, TC and TF) occur within the succession, which have REE pattern with distinct negative Eu anomaly implying a volcanic origin (Wray et al. 1996).

Although intensively bentonized, several idiomorphic zircon grains with high-T typologies (850-900°C) could be separated for radiometric age determinations from the TD1 layer in the basal Late Turonian strata. The zircon grains yield an U-Pb age of 91.5 ± 0.7 Ma, allowing correlations with tuff horizons found in Upper Cretaceous sediments in NW Europe (Wray 1999) or in the Polish Carpathians (Bąk et al. 2001). The new data may also help to identify the source area of these pyroclastic layers of supposed acidic composition.

Details

Author
Karsten Obst1, Armin Zeh2, Tobias Fischer3
Institutionen
1Geological Survey of Mecklenburg-Western Pomerania, LUNG M-V;University of Greifswald, Institute of Geography and Geology; 2Karlsruhe Institute of Technology, Working Group Applied Geology – Mineralogy & Petrology; 3Natur- und Geopark TERRA.vita
Veranstaltung
GeoSaxonia 2024
Datum
2024
DOI
10.48380/a0kp-vw85