Early Miocene (Burdigalian) marine rocky shores in the French Jura Massif: a palaeoecological and palaeoenvironmental analysis

摘要: Fossil bioerosion traces at a new site of Les Bez (Jura Department) and those already known from Verrieres-de-Joux (Doubs in the central French Jura record an ancient Miocene cliffed shoreline cut into Lower Cretaceous limestones. Both localities are about 900 m above present sea level. Caulostrepsis, Gastrochaenolites Circolites ichnogenera identified Bez, whereas only is Verrieres-de-Joux. This ichnoassociation identifies Entobia ichnofacies, which corresponds to upper infralittoral marine environment, biologically associated with biocenosis photophilic algae. By means digital analysis high-resolution field images, percentage surface affected by erosive activity polychaete worms, bivalves echinoids has been calculated. information permits better evaluation their biological activity, thus complementing data on number specimens per area. The cliff preserved was more affected, showing diameters smaller than Verrieres. Circolites–Caulostrepsis association well developed where borings located within echinoid bowl-shaped pits particular patterns, suggesting ecological relationship between involved organisms. Moreover, distribution along this outcrop not uniform three sections (A, B C) suggests lower zone under slightly different environmental conditions infralittoral. exceptional preservation fossil cliff-site demands protection order ensure its future existence accessibility.