Arbeitsbericht NAB 20-01

Quaternary Borehole QBO Trüllikon-Rudolfingen (QTRU) – Data Report

In the context of the sectoral plan "Sachplan geologische Tiefenlager" (SGT) Nagra is currently investigating three siting regions (Jura Ost, Nördlich Lägern, Zürich Nordost) in northern Switzerland to potentially host repositories for radioactive waste. The field exploration project "Quartäruntersuchungen" (QAU) is dedicated to the charac terisation of Quaternary deposits within and around these siting regions to further constrain scenarios of their geological long-term evolution. The investigations support the reconstruction of Quaternary landscape evolution.

The borehole (Quartärbohrung, QBO) at Trüllikon-Rudolfingen (QBO Trüllikon-Rudolfingen / QTRU, Tab. 1) is part of Nagra's Quaternary investigation programme (QAU; Nagra 2018a). The drill site was chosen to constrain the bedrock geometry and the valley fill of the Rudolfingen Trough (Fig. 1 and 2) together with borehole QBO Marthalen-Oobist (QMOB, Kuster et al. 2019). The borehole QTRU was positioned in the centre of the Rudolfingen Trough based on recently acquired reflection seismic line 16-QAU-11 (Nagra 2018b). The borehole QTRU was conducted in the period 15.02.2019 – 05.04.2019 using a combination of Düsterloh hammer drilling and wireline drilling with a triple-tube corebarrel, i.e. with a plastic core liner.

This report covers the request for a documentation of the authorised works on-site (UVEK 2019, Dispositiv 5.29) and documents also the core description and first lab analyses (UVEK 2019, Dispositiv 5.30). The work has been carried out according to the work program (Arbeitsprogramm, Nagra 2019) and this report corresponds to the data report announced there.

In this report, we present core images, sedimentological descriptions and geophysical measurements of the cores, all of which were acquired at the University of Bern. Additionally, a report on geophysical borehole logging by terratec Geophysical Services GmbH & CO KG and L. Keller (roXplore gmbh; responsible for quality control) and a technical drilling report by Blétry AG edited by P. Hinterholzer-Reisegger (Nagra) are presented in Appendices H and I, respectively. This report is the basis for planning further core analysis and later interpretation in the larger geological context.