Paleobotanical assemblage from the Lower Jurassic amber bearing levels from the Rotzo Formation, Monti Lessini (Venetian Prealps, Northern Italy)

The Rotzo Formation flower Jurassic) is famous for its fossiliferous content, includ- ing plant fossils that have been collected and studied since the XIX century. The For- mation is composed of bioclastic limestones and marls, deposited from shallow ma- rine to lagoonal environments in the tropical zone. Of particular interest is the recent discovery of fossil resin [amberJ in the Bellori section [Lessini Mountains, Verona). This section is about 20 m thick and composed mostly of marine limestones. The limestone is well stratified, with beds of 10 cm to more than one metre thickness. In- tercalated in the limestones are clayey levels 3 to 40 cm thick sometimes yielding well-visible coal and charcoal fragments. The amber was found as millimetre-sized fragments in two clayey levels intercalated in the limestones. It is blackish to red-brownish in colour and can be subdivided, ac- cording to its size and shape, into droplets and tubular-shaped structures about 10-15 pm in diameter. The palynological assemblages from the two clayey levels yielding the amber contain abundant Classopollis and trilete spores, Classopolliswas produced by cheirolepidiaceous conifers that were probably well adapted to both wet and dry climates in a coastal area. The trilete spores in the plant assemblage are more diversified and be- long to sphenophytes, horsetails, lyCophytes and ferns. The dominance [more than 50%) of trilete spores (e.g., Deltoidospora) suggests abundant freshwater, corre- sponding to a general humid climate. A nearby marsh environment is inferred by the presence of freshwater algae such as Botryococcus and Pseudoschizaea; the latter is reported for the first time from the Lower furassic. Some clayey levels yielded many very well-preserved cuticle fragments. They are gen- erally thich with a high number of slightly sunken stomata complexes on both sides of the leaves. These cuticles are currently under study: preliminary data suggest that most cuticles belong to Pagiophyllum cf. rotzoanum, a cheirolepidiaceous conifer, but the diversity in the cuticle assemblage is high. The exceptional preservation of the cu- ticles and other palynomorphs suggests negligible transport after shielding from the parent plants, and sedimentation taking place in calm water, free from wave action and surface disturbance, as well as sedimentation in low-oxygen conditions. Some of the clayey levels yielded also numerous pieces of charcoal with well-preserved vascu- lar tissues. Sedimentological and palynological analyses suggest for the amber-bearing clayey levels a lagoonal palaeoenvironment with humid climate, comparable to the present- day Taxodium swamp or cypress swamp and a bahamian-type marine environment, with the additional influence of monsoonal climate as in modern southern Asia.