Late Jurassic sea-level fluctuations in NW Switzerland (Late Oxfordian to Late Kimmeridgian): closing the gap between the Boreal and Tethyan realm in Western Europe

In Late Jurassic times, the Swiss Jura carbonate platform occupied the transition between the Paris Basin and the Tethys and thus connects the Boreal and Tethyan realm. Up to now, the lack of index fossils in the Reuchenette Formation prevented a reliable correlation between both areas (its sediments are characterised by a prominent sparseness of index fossils). Now, seven recently in situ collected species of ammonites helped to establish a new sequence-stratigraphical frame for the platform sediments of the Reuchenette Formation in NW Switzerland. Based on biostratigraphical data, five third-order sedimentary sequences were assigned to the Late Oxfordian to Late Kimmeridgian. The upper three third-order sequences correspond to the Boreal sequences Kim3–5 of Hardenbol et al. (1998). The deduced large-scale sea-level fluctuations match those from other European regions (Spain, Russia). This biostratigraphically based sequence-stratigraphical frame is a prerequisite to refine correlations within a wider area covering the Swiss Jura and parts of adjacent France and Germany.