Paleoproterozoic
Proterozoic era spanning 2500–1600 Ma; period subdivisions are Siderian, Rhyacian, Orosirian, Statherian.
Language and route: Modern scientific compound from Greek roots. International stratigraphic compound with a relative Greek prefix added to Proterozoic; not an ancient Greek word.
Literal gloss: old earlier life
The name and its history
International Precambrian Stratigraphy Subcommission / IUGS · 1990 ratification; 1991 publication
- What does the word literally mean?
- Paleo-, meso- and neo- identify oldest, middle and youngest subdivisions of the Proterozoic, respectively; the deeper protero-zoic element is itself historically relative to the Paleozoic.
- What did the original author mean?
- The prefix marks the oldest third of the Proterozoic, not the origin of ancient life.
- Why was the name needed?
- Modern Precambrian correlation required three consistently named, ranked era-scale units.
- What evidence supported the original concept?
- International subdivisions were standardised around 1990–1991 with numerical limits rather than a single fossil sequence.
- How has geology changed the concept?
- Formal nomenclature persists although event-based alternatives to portions of the Precambrian scheme are under investigation.
Further historical context
The three-era subdivision and named Proterozoic periods were formalised in the 1991 account by K. A. Plumb on behalf of the international subcommission.
Because many lower boundaries are GSSAs fixed numerically rather than fossil-defined GSSPs, their Greek roots must not be treated as defining global events.
Editorial qualification
1991 ratification is established, but first individual usage of the full compound was not investigated.
Related names
Proterozoic · Archean · Mesoproterozoic · Siderian · Rhyacian · Orosirian · Statherian · Fossil · Stratigraphy · GSSP
Sources
- ICS International Chronostratigraphic Chart, 2026/06 — Current name, rank and numerical boundaries
- Plumb (1991), New Precambrian time scale — 1991 ratification and nomenclature of Proterozoic subdivisions
- Shields et al. (2021), revising the pre-Cryogenian time scale — Review of chronometric boundaries and historical meaning