The Jurassic Period was affected by the opening of the Atlantic Ocean and the associated development of the Piemont – Liguria Ocean (Schmid et al. 1996, Handy et al. 2010, Winkler 2024; Fig. 3‑5c). Associated extension gave rise to multiple pulses of increased heat flow that affected the burial history in Northern Switzerland (e.g. Mazurek et al. 2006). Peak Early Cretaceous burial temperatures are recorded in the Early Jurassic units.
During the Early Jurassic, Northern Switzerland continued to be in a shallow, subtropical to tropical epicontinental sea. It was bordered to the east and south by the Vindelician Land and its promontory, the Alemannic Land, in the area of the present-day External Crystalline Massifs. The Early Jurassic succession (Lias Group, Staffelegg Formation) is characterised by a condensed succession of calcareous hardgrounds with phosphatic and reworked nodules, and iron-oolites, with common reworking and multiple hiatuses (Reisdorf et al. 2011). In addition, there are phases with expanded deposition recorded by units of siltstone and partly organic-rich claystone. In Northern Switzerland, the different stratigraphic intervals can be well correlated.