Siderian
Proterozoic period spanning approximately 2500–2300 Ma on the 2026 ICS timescale.
Language and route: Modern international scientific formation from Greek. Classical Greek lexical stem adapted as an international period-name; precise language of the first individual coinage not verified.
Literal gloss: iron
The name and its history
ICS/IUGS Precambrian subdivision · ratified c. 1990; published 1991
- What does the word literally mean?
- Greek sídēros, ‘iron’, likely alluding to abundant ancient iron formations. The etymological cue is clearer than the original namer’s specific intent.
- What did the original author mean?
- The iron-derived name suggests major iron deposition; that exact intention is inferred, not traced to an individual namer.
- Why was the name needed?
- The subcommission needed fixed period names for Precambrian intervals with weak global rock-to-rock correlation.
- What evidence supported the original concept?
- A 1991 international numerical timetable provides secure standardisation, but does not document the original coiner’s interpretation of ‘iron’. The 1986 draft specified unnamed chronometric intervals; the 1991 announcement documented their later formal nomenclature.
- How has geology changed the concept?
- Iron formations are not confined to this period, and the name does not define a worldwide synchronous iron-deposition event.
Further historical context
Siderian belongs to the family of named Proterozoic periods standardised by the international Subcommission on Precambrian Stratigraphy and announced in Plumb (1991). The contemporaneous scheme defined these boundaries numerically, not from a global type section.
Subsequent work (Shields and colleagues, 2021) notes the mismatch that can arise between such chronometric limits and the geological processes suggested by the names. The term should not be interpreted to mean that all banded iron formations formed in this interval.
The Subcommission’s 1986 framework proposed unnamed Proterozoic period-scale divisions. The period vocabulary published by Plumb in 1991 arose from later collective standardisation. Its Greek image is an interpretive cue, but cannot establish a named scientist’s specific intent or a synchronous boundary event.
Editorial qualification
Individual coiner not established. Do not attribute the image suggested by Greek roots to a documented person or make it the definition of the time boundary. Collective subcommission standardisation is documented (1986 proposals; 1991 ratification).
Related names
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
- Liddell–Scott–Jones Ancient Greek Lexicon (Logeion) — Greek lexical meanings; not evidence of original scientific coinage
- Plumb & James (1986), Precambrian subdivision proposal — Original subcommission planning: period boundaries proposed before individual period names were finalised