Abstract
This chapter discusses the proposal for the global stratotype section and point (GSSP) for the base of the neogene (the palaeogene/neogene boundary). The historical concepts of “stratigraphic units” (chronostratigraphic units of modem usage) have been based mainly on two observations: (1) Major or minor discontinuities (or facies changes) in rock sequences, and (2) major or minor changes in the overall biotic content, or within a specific taxonomic group. The GSSP section is situated within the Visone-Lemme facies belt in the upper part of the Rioroso Formation, which overlies the Molare formation (Oligocene fan delta conglomerates with sandy shallow-marine intercalations yielding micro and macrofauna). The total mineral content is dominated by phyllosilicates and quartz, with various amounts of feldspar, calcite, dolomite, serpentine and pyrite. The main part of the clay fraction consists of a high amount of smectite, and minor parts of illite, kaolinite, chlorite and even serpentine. Only the most important biostratigraphic markers are discussed here. In general, the preservation of planktonic foraminifera and calcareous microfossils is moderate to poor; the dinocyst preservation is good to excellent.