CONICET | Buscador de Institutos y Recursos Humanos

Two sections from the type area where Piedra Clavada Fm. is found yielded pollen assemblages in which 65 palynomorphs have been determined, among which the presence of Bryophytes/Pteridophytes, Gymnosperms, Angiosperms and terrestrial plancton was confirmed. Few and badly preserved marine dinoflagellates confirm the close influence of sea shore in a delta environement that dominate both sections. These assemblages are similar to those found at La Horqueta section where the basal section of Piedra Clavada Fm. includes ammonites of Early Albian age. The two section studied in the type area are composed of slightly younger deposits that are covered by the Late Cretaceous Mata Amarilla Fm. The similaity of assemblages suggests that they correspond to the same paleofloristic episode and could be united into one biozone in the near future. Comparisons with asssemblages found in the Kachaike Fm., based on presently available data also show similarities with Piedra Clavada palynological content, however with slight differences that point to its younger age (Early to mid Albian), as suggested by dinoflagellate studies. Comparisons with aptian units found in the same area (Río Mayer Fm. ) and in neighbouring basins (Baqueró Basin and Golfo San Jorge Basin) are briefly considered. Finally, the importance of primitive angiosperm sporomorphs is pondered in regard to their variety and biostratigraphic significance.