Available magnetostratigraphic and radiometric age data for Neogene sedimentary rocks within the Great Hungarian Plain can be shown to be consistent with each other if primary seismic reflectors are interpreted as geological time lines. Using this premise, we argue that the boundary between the lower and upper Pannonian (s. l.) units is diachronous and varies from 9 Ma to about 7 Ma. Lithogenetic units, determined by analyzing the trend of lithologic development in drill holes, and the correlation of these units by reflection seismic data provide a means of dividing the lower Pannonian into three subunits (Pa<pl>1a<above>1</pl>, Pa<pl>1b<above>1</pl>, and Pa<pl>2<above>1</pl>). By combining age data with these correlations, the unconformity between synrift and postrift sediments can be shown to represent a time gap of one to several million years in many places in the Pannonian basin.