Ammonite biostratigraphy as a tool for dating Upper Jurassic lithographic limestones from South Germany first results and open questions

Although the Upper Jurassic lithographic limestones of Franconia and Swabia belong to the worldwide most famous fossil sites ('Fossil Lagerstatten'), a detailed biostratigraphical analysis was missing. Often the various fossiliferous localities, distributed over an area of several hundreds of square kilometres, were summarized as 'Solnhofen', and an early Tithonian age was traditionally assumed for most of them, with few exceptions. This is the first comprehensive attempt for a high-resolution biostratigraphy based on ammonite biohorizons. The different ages of laminated limestones obtained by this method, ranging from the Kimmeridgian Pseudomutabilis Zone to the Tithonian Ciliata Zone - a duration of ca. 4 Ma - provide a basis for future high time-resolution correlations, environmental reconstructions, and deposition-modelling.