Palynology of the Permian and Triassic of the Tesero and Bulla sections (Western Dolomites, Italy) and consideration about the enigmatic species Reduviasporonites chalastus.

A palynological study of two Permian-–Triassic sections of the Southern Alps (Tesero and Bulla sections) was carried out in order to correlate the palynological data with the available conodont zones. Both the sections crop out in the Western Dolomites, the Tesero section in Fiemme Valley and the Bulla section in Badia valley. The two sections include the uppermost Bellerophon Formation and the overlying Werfen Formation. In the latter the Permian/Triassic boundary (Farabegoli et al., 2007) has been defined by conodonts. The palynological assemblages collected in both sections throughout the Bellerophon up to the Werfen formations show compositional variation marked by: a) a dominance of taeniate and non -taeniate bisaccates in the Bellerophon Formation dated as Late Permian; b) a bloom of the organic microfossil incertae sedis Reduviasporonites chalastus in the lower Tesero Member (Werfen Formation), found only in the Tesero section. This interval should stratigraphically lie below the Permian/Triassic boundary, as defined by conodonts recorded in the Bulla section; c) poorly preserved acavate and bisaccate taxa in the upper Tesero Member, above the Permian/Triassic boundary, and in the overlying Mazzin Member of the Tesero section. The origin and the ecological preferences of Reduviasporonites chalastus and the implications of its worldwide distribution across the Permian/Triassic boundary are also discussed.