Organic-walled microplankton studies from beds of the Sarmatian–Pannonian stratotype section at Marosorbó (Oarba de Mures), Transsylvanian Basin

Abstract

This study provides the results of investigations of organic-walled microplankton derived from the beds of the
Sarmatian–Pannonian boundary-stratotype section at Oarba de Mures (Marosorbó). Based on biostratigraphic
investigations, Mecsekia ultima, Spiniferites bentorii pannonicus and Spiniferites bentorii oblongus Assemblage-Zones
were identified, resulting in the determination of the boundary between the Sarmatian and Early Pannonian formations.
In Section ’A’ the Sarmatian–Pannonian boundary was defined at 3.4m, coinciding with the mass appearance of the
species Mecsekia ultima. At a depth of 1.4m the subspecies Spiniferites bentorii pannonicus appears, this is a zone marker
for the Pannonian stage.