Geoscientific characterization of claystone as part of the German Repository Site Selection Act – “Sub-area Opalinuston Formation”

According to the Repository Site Selection Act (Standortauswahlgesetz – StandAG), the German Site Selection Procedure is an iterative process and consists of three phases with increasing levels of detail in which the assessed area is continuously reduced during the process. Starting with an empty, so-called “white map of Germany”, BGE (implementer of the German Site Selection Procedure) completed Step 1 of Phase I in September 2020 with the submission of the Sub-areas Interim Report (BGE 2020/88), where BGE identified 90 individual sub-areas (in claystone, rock salt, and crystalline rock).

In Step 2 of Phase I, BGE aims to localize siting regions within the 90 sub-areas by applying preliminary safety assessments and other scientific criteria. Within the preliminary safety assessments, subsurface data are interpreted and the results documented. The workflow comprises the detailed characterization and interpretation with a focus on the host rock formation that acts as the main geological barrier but also considers the surrounding rock formations.

The claystone succession of the “Opalinuston Formation” in southern Germany has been designated as claystone sub-area. Based on borehole data, the sequence was mapped and described in vertical and lateral extend. This information was used to assess, for example, the thickness of the barrier and the maximum depth of the top of the Opalinuston Formation, which led to the categorization of parts of the sub-area in the first two steps of the preliminary representative safety analysis. This poster explains the results that were already published as a preliminary working status in 2024.