Abstract
Abstract. Quaternary deposits are complex and heterogeneous. They contain some of the most abundant and extensively used aquifers. In order to improve the knowledge of the spatial heterogeneity of such deposits, we acquired a large (1500 ha) and dense (20 m spacing) time domain electromagnetic (TDEM) data set in the upper Aare Valley, Switzerland (available at https://doi.org/10.5281/zenodo.4269887; Neven et al., 2020). TDEM is a fast and reliable method to measure the magnetic field directly related to the resistivity of the underground. In this paper, we present the inverted resistivity models derived from this acquisition. The depth of investigation ranges between 40 and 120 m, with an average data residual contained in the standard deviation of the data. These data can be used for many different purposes: from sedimentological interpretation of quaternary environments in alpine environments, geological and hydrogeological modeling, to benchmarking geophysical inversion techniques.
Highlights
Background and summaryIn most urbanized and agricultural areas of Switzerland, the shallow underground is constituted of Quaternary deposits
The construction of geological models using only boreholes can miss most of the spatial heterogeneity and lead to inadequate models and wrong conclusions
There is a need for a better understanding of Quaternary sedimentary heterogeneity, in order to better constrain geological models, knowledge that could be applied in the Aare Valley or for any fluvioglacial filling area
Summary
In most urbanized and agricultural areas of Switzerland, the shallow underground is constituted of Quaternary deposits. Near-surface geophysics such as DC resistivity, electromagnetic, or seismic methods can bring important information in terms of the spatial distribution of facies They are usually carried out in restricted areas to answer specific local questions and do not help to understand the variations in geology at the valley scale. Quaternary formations are highly heterogeneous and constitute a challenge for geostatistical and uncertainty modeling (De Marsily et al, 2005) Sharing this data set will allow the testing and comparison of various methods to interpolate the properties of the underground and construct models that can be used for various purposes. From a more geological perspective, the tTEM20AAR data set could be used to better understand the internal structures of quaternary deposits within alpine valleys. It could be analyzed in detail from a sedimentological perspective and used to better constrain the glacial and geological history of the quaternary deposits (Preusser et al, 2011)
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