Abstract

The recently published time scale by Harland el al. (1982) is critically considered. The unique significance of the transition from dominantly chronometric to dominantly chronostratic boundaries based on the "biostratigraphic sequence" is an additional justification for the higher ranks previously given to the Vendian (Era) and its constituent divisions: Varangian (or Varangerian) and Ediacaran (or Ediacarian) periods. The historic transition begins with the latest of the Proterozoic glaciations (the earlier ones started about 950 m.y. ago) and ends with the exponential diversification of the Metazoa. The stratigraphic sequence is demonstrable on the East European Platform where the type section of the Vendian is located, and on the Yangtse Platform. Normative, operationally designated boundaries are required for the stratigraphic divisions. The history of life in which there are no sharp initial and terminal boundaries shows clearly a rapid transition from widespread but generally rare occurrences of Vendian, particularly Ediacaran, fossils to ubiquitous, generally "shelly" Paleozoic (initially Cambrian) faunas of unquestioned biostratigraphic importance. This biohistoric transition is the beginning of the Phanerozoic division of a unique historic process. For the eon of the stratigraphic scale comprising Paleozoic to Cenozoic eras the new term Holozoic is therefore proposed.--Modified journal abstract.

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