A chronostratigraphic division of the Precambrian: possibilities and challenges
This chapter provides a review of events through Precambrian Earth history, with the aim of providing an up-to-date foundation on which to construct a chronostratigraphic revision of the Precambrian time scale. The guiding principles used to develop a revised Precambrian time scale follow Cloud’s vision to “…seek trend-related events that have affected the entire Earth over relatively short intervals of time and left recognizable signatures in the rock sequences of the globe…”, and apply Gould’s historical principles of directionality and contingency. Analysis of the Precambrian geological record reveals a series of linked, causative events over time that can be used as a basis for a more naturalistic time scale that better reflects our knowledge of events in the history of our planet and can be used as a template for further research. A revised Precambrian time scale envisages three eons: 1)A Hadean Eon, which extends from the time of formation of the solar system (T0 = 4567 Ma), to the age of Earth’s oldest rock (4030 Ma Acasta Gneiss); 2)An Archean Eon, extending from the top of the Hadean Eon to the time of the fundamental transition from an early, hotter, reducing Earth to a more modern, cooler, oxidized Earth, at c. 2420 Ma; 3)A Proterozoic Eon, from the c. 2420 Ma Archean-Proterozoic boundary to the base of the Phanerozoic Eon (542 Ma). Each of the eons may be subdivided into a number of eras and periods that can each be marked by a chronostratigraphic Global Stratotype Section and Point (GSSP), excepting lowermost chronometric divisions of the Hadean Eon and Paleoarchean Era. Suggestions are presented for the age, name, and GSSP locality of each division.