Late Pliensbachian (Early Jurassic) ammonites from Lac de Charmes (Haute-Marne, France): Systematic, biostratigraphy and palaeobiogeography

The present paper deals with the systematic description of a rich and well-preserved ammonite fauna of the Late Pliensbachian, collected in two outcrops near the “Lac de Charmes” (Haute-Marne, France). In terms of ammonite zonation, the studied faunas indicate the Margaritatus and Spinatum Chronozones. Most of their subdivisions (subchronozones and zonules) have been recognized for the first time in this region. We propose a correlation with zonations established in close areas (Germany, Southern France). As already suggested on the literature, the possibility to further subdivide the Solare zonule in finner intervals is confirmed by our data. Within this zonule, we recognize a first interval with only Pleuroceras solare (Phillips, 1829), and a second one where this species occurs with several subspecies and where Pleuroceras spinatum (Bruguière, 1789) appears. Our results also confirm the possibility to subdivide more finely the Solare zonule firstly suggested by some authors. We recognize a first part with only Pleuroceras solare and a second one where this species present various subspecies and where Pleuroceras spinatum appears. Some points of view are given about Amaltheus gr. margaritatus Montfort, 1808, Pleuroceras gr. solare (Phillips, 1829) and the species Pleuroceras transiens (Frentzen, 1934).