Original paper

The case for the original Neogene

Hilgen, Frits; Aubry, Marie-Pierre; Berggren, Bill; van Couvering, John; McGowran, Brian; Steininger, Fritz

Abstract

In 2004, the Quaternary was deliberately eliminated as a formal chronostratigraphic unit from the standard Geological Time Scale (GTS) while the Neogene extended to the Recent. This extended Neogene was not a spontaneous undertaking by the Neogene community. It is rooted in a strong and long-standing tradition in the study of especially the marine stratigraphic record. The original definition of the Neogene by Hörnes in 1853 included stratigraphic units that are now considered middle Pleistocene in age, but is ambiguous with regard to its upper limit. Nevertheless the concept of an extended Neogene was incorporated in a number of time scales but was not widely employed until it was firmly adopted by marine stratigraphers when they started to explore the deep marine record of the Cenozoic in the middle of the 20th century. As such the extended Neogene is found in the original codification and subsequent modifications of all standard microfossil zonal schemes with N(eogene) zones continuing up to the Recent. Moreover the extended Neogene was generally accepted by the DSDP and ODP community and incorporated in widely used integrated - magnetobiochronostratigraphic - time scales and in prominent textbooks dealing with Earth history. It has been likewise accepted by vertebrate paleontologists. The concept of an extended Neogene also stood at the base of the recommendations for defining the Pliocene/Pleistocene (= Tertiary/Quaternary) boundary that originated from the 1948 International Geological Congress (IGC) in London. The continuous deep marine archive is most suitable for the formal definition of global chronostratigraphic units to be incorporated in the standard GTS. Clearly this marine standard is pre-eminently exemplified by the Neogene but is at odds with the dominantly continental-based Quaternary. In fact, the detailed study of the marine Neogene has revolutionized chronostratigraphic thinking during the last several decades. It has led to a stable astronomical-tuned Neogene time scale with a fully integrated magnetobiochronostratigraphic framework via first-order correlations. This innovative approach further resulted in re-emphasizing the usefulness of the unit stratotype concept, in the potential introduction of orbital controlled cycles as formal chronostratigraphic units of minor rank (chronozones) and in the inter-calibration of astronomical and radio-isotopic time. For all these reasons, the term Neogene should remain attached to the extended concept of 23-0 Ma. Furthermore, if nomenclature reflects geological thinking, understanding and practice of Earth history, the truncation of the Neogene at 2.6 Ma would introduce an artificial division, especially when looking from the marine perspective. This would prevent scientific communities who deal with Earth history beyond the last 2.6 myr from correctly expressing the continuity of the evolutionary, oceanographic, climatic, and tectonic dynamics over the last 23 my.

Keywords

neogenequaternarycenozoicchronostratigraphygeological time scaleearth history