A new terrestrial plant-rich Fossil-Lagerstätte from the middle Cenomanian (Late Cretaceous) of the Apennine Carbonate Platform (Magliano Vetere, southern Italy): Depositional and palaeoenvironmental settings

We describe a new terrestrial, plant-rich Fossil-Lagerstatte discovered at Magliano Vetere (Campania region, S Italy) in the middle Cenomanian of the Apennine Carbonate Platform. The deposit, 1.42 m thick, is made up of a thin-bedded interlayering of evenly laminated dolomicrites, lenticular dolorudites and carbonaceous seams, which contain well-preserved remains of terrestrial plants yielding cuticles and minor fishes. This study focuses on plant remains, to provide systematical, taphonomical and palaeoenvironmental considerations; nevertheless, a preliminary analysis carried out on fossil fishes has led to the identification of pycnodontids and teleosts. The Fossil-Lagerstatte retains sterile foliage-bearing shoots with epidermal features belonging to the genus Frenelopsis of the extinct conifer family of the Cheirolepidiaceae. Plant remains possibly represent a stable biotope, as floral composition displays no variation along the deposit. Nevertheless, episodes of harsh environmental conditions occurred as demonstrated by a fish mortality event and Ca-sulphate evaporite precipitation. Taphonomical considerations and sedimentological evidence from the encasing sediments suggest a parautochthonous deposition of fossil plants in a supratidal/intertidal mudflat, including a salt-marsh that was characterised by a restricted sea-water circulation, deposition of primary dolomite and episodical wildfires. The presence of xeromorphic features in Frenelopsis from Magliano Vetere could represent an adaptation to haline environment which was subjected to microtephra supply from a distant, orogenic volcanism. The facies evolution of the studied Fossil-Lagerstatte records a rapid regressive and a following slower transgressive trend, and constitutes the lowermost portion of a ~20 m thick interval characterised by several dolomitic plattenkalk, up to 1.50 m thick, which are separated by cyclically stacked peritidal limestones. We infer that: 1) the ~20 m thick, Plattenkalk-bearing interval represents a Sequence Boundary Zone in the stratigraphical record of the middle Cenomanian ApCP; 2) Frenelopsis thrived at the verge of an arid–semiarid climatical phase during a major pulse of relative sea-level fall.