Sprecher
Beschreibung
A new diverse acritarch flora has been recovered from siltstones and claystones of the Landeyran Formation from the Early Ordovician Cabrières Biota and coeval Landeyran section in the southern Montagne Noire, France. Never studied since the late 20th century, the current study enriches the knowledge on the acritarchs from the southern Montagne Noire by the identification in this moderately to well-preserved assemblages of biostratigraphical, palaeobiogeographical and palaeoecological signals. In addition to typical Early and Middle Ordovician genera Veryhachium, Striatotheca, Peteinosphaeridium, and Aureotesta, identification of several typical index taxa from the Early Ordovician, such as Coryphidium bohemicum, Ampullula spp., Barakella spp. associated with the absence of Arkonia, Frankea, Orthosphaeridium and Dicrodiacrodium allows a precise assignment of a late middle to early late Floian age (transition Fl2 to Fl3) confirming the biostratigraphic data from trilobites and graptolites biozonations. The attribution of the assemblages to the high southern latitudes of the peri-Gondwana province is expressed by the presence of Arbusculidium, Coryphidium, Striatotheca and Acanthodiacrodium. The current studies suggest a re-evaluation of the local First Appearance Datum of Ampullula in the southern Gondwana from the early Darriwilian to the late Floian. The evolution of the relative proportion of the different groups and genera within the Landeyran section express a progressive change from a galeate’s to a polygonomorphs’ dominated palaeo-assemblages suggesting the presence of a transgressive phase to the Landeyran Formation conform to the sedimentary data.