Toarcian sporomorph assemblages from the Umbria‐Marche basin, central Italy

Abstract

The qualitative and quantitative characteristics of the Toarcian sporomorph assemblages from the Umbria‐Marche domain, are consistent with those of the palynological phase VI (late Pliensbachian, Toarcian, earliest Middle Jurassic) as defined by Visscher et al. (1980) in the Germanic realm. The presence of compositional similarities among palynological assemblages from widely separated areas emphasizes the potential of palynology in correlation problems. The Umbria‐Marche sporomorph assemblages correspond to an advanced stage of phase VI, where first occurrences of some index taxa, such as Leptolepidites spp., Trilites spp., Ischyosporites spp., Foveosporites spp. are observed, and the genus Callialasporites was represented by only one species, with low relative abundance. By means of qualitative analyses, together with species richness variation trends of older and younger sporomorphs, the Toarcian portion of phase VI in the Umbria‐Marche area can be subdivided into two assemblages. The variation trends concerning the relative abundances of bisaccate pollen and pteridophytic spores in the Northern Hemisphere, deduced by comparison with previous data, were related to palaeoclimatic causes.