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Large-scale semi-automatically generated thickness maps: better paleogeographic understanding helps to identify mineral occurrences with favorable geometry

Semi-automatically generated maps highlight the variability of the stratigraphic thickness of the Helvetic Kieselkalk. This geological unit is exposed in different Helvetic nappes over more than 300 km along the Swiss Alps and it is commonly extracted to produce hard rock aggregates for the national road and railway infrastructure. The deposition of this unit onto the European (Helvetic) continental margin during the Early Cretaceous coincided with normal faulting, which lead to strong lateral thickness variations.

The Python and MATLAB approach used to create the thickness maps was developed as part of a Switzerland-wide mineral resource mapping project and has been applied to the geological vector dataset GeoCover. The approach is designed to rapidly generate large-scale map overviews of the stratigraphic thickness, for which the construction of 3D models would be very time consuming.

Our results highlight an increase in thickness along the Alps from 100 m in the west to 1000 m in the east. The depositional thickness was certainly modified by the subsequent burial, folding, and faulting during the formation of the Helvetic nappes. Two discrete thickness jumps indicate the presence of three sedimentary basins in east-west direction with a half-graben-like geometry. These thickness jumps coincide with present-day nappe boundaries and suggests that the inherited basin geometry influenced the nappe formation.

The large-scale thickness maps and the improved undestanding of the paleogeography and tectonic evolution are used to rapidly identify mineral occurrences with favourable geometry. These can, when sufficiently investigated, be considered in land use or resource safeguarding plans.

Details

Author
Lukas Nibourel1, Thomas Galfetti2, Stefan Heuberger1
Institutionen
1Georesources Switzerland Group, Department of Earth Sciences, ETH Zurich, Switzerland; 2Swiss Geological Survey, Federal Office of Topography swisstopo, Wabern, Switzerland
Veranstaltung
GeoSaxonia 2024
Datum
2024
DOI
10.48380/p94s-hx44