A calibrated composite section for the Late Jurassic Reuchenette Formation in northwestern Switzerland (?Oxfordian, Kimmeridgian sensu gallico, Ajoie-Region)

Abstract.

A new stratigraphical frame for Kimmeridgian sediments of northwestern Switzerland has been established by correlating seventeen closely spaced sections by means of lithological, sedimentological, and microfacial data as well as by ammonites. This newly established stratigraphical frame is of great value, because these sediments are usually characterised by a prominent sparseness of index-fossils (i.e. ammonites).

The biostratigraphical frame is based on seven species of ammonites and corroborated by ostracodes. The investigated sedimentary record is divided into nine intervals and assigned to the Late Oxfordian to Late Kimmeridgian sensu gallico (middle Eudoxus-Zone). Exact lithological correlations between the outcrops are achieved by three marker beds.

The new stratigraphical frame is a pre-requirement for refining correlations of sections, for reconstructing sea level fluctuations, and for quantifying synsedimentary differential subsidence.