A method is presented here for subdividing the Neogene sedimentary rocks of the Pannonian basin based on the fact that these Neogene sediments are made up almost exclusively of pelite and psammite. The alternation of pelitic and psammitic layers and their thicknesses are known from geophysical well logs. We construct lithologic trend diagrams for several drill holes, and for each drill hole we obtain a characteristic trend diagram. Changes in lithologic trends can be used to define lithogenetic units, which may be used as a basis for subdividing the Pannonian strata. Similar lithologic trend diagrams from neighboring boreholes allow for local correlation of lithogenetic units. This correlation has been extended to a regional system of lithogenetic units through analysis o many lithogenetic trend curves and reflection seismic sections.

The Pannonian (s. l.) complex of the Great Hungarian Plain was divided into (from deepest to shallowest) units Pa<pl>1a<above>1</pl>, Pa<pl>1b<above>1</pl>, Pa<pl>2<above>1</pl>, and Pa₂. The lowermost units can be shown to occur only in the deep basin areas where sedimentation was probably uninterrupted from Sarmatian to Quaternary time.