The sedimentary units of the Dogger Group that directly overlie the Opalinus Clay form the lowermost and most important part of the upper confining units (Section 4.5.3.5). They were deposited in the Middle Jurassic. At this time, Central Europe was affected by the development of the Piemont – Liguria Ocean, resulting in large-scale N-S-directed extension leading to subsidence (Chapter 3). The Dogger Group above Opalinus Clay was deposited in a shallow epicontinental sea with some lateral and vertical facies variability (Fig. 4‑32).
Fig. 4‑32:Map of depositional environments during the Middle Jurassic (Middle Aalenian to Early Oxfordian) preserved in the Dogger Group above Opalinus Clay
Refer to Fig. 4‑3 for a schematic representation of depositional environments. The north arrow refers to present-day geographic north. Map shows the setting during the time interval 170.9_Aal_300 to 154.8_Oxf_975 as discussed in the text.
Fig. 4‑33:Stratigraphic borehole correlation of the units of the Dogger Group above Opalinus Clay
For lithological nomenclature refer to Naef et al. (2019). Clay-mineral content after Becker & Marnat (2024). Some of the boundaries and lithologies as discussed in the original reports were adjusted to integrate all presented borehole data.