Aeronian

The name and its history

Silurian Subcommission deliberations 1984; adoption reported by Holland/Bassett · See attributed dates and cited original / standardisation works; first-use priority qualified where noted

What does the word literally mean?

Named for cwm-coed-aeron. Immediate scientific language-route: Welsh locality → international English. This is a locality-based or geographical term, not a description of a universal geological event.

What did the original author mean?

A middle Llandovery stage introduced during international agreement in place of parts of the older Idwian–Fronian four-stage scheme.

Why was the name needed?

A new middle Llandovery stage was chosen when an earlier four-stage scheme was judged unsuitable for worldwide correlation; Aeronian replaced the intermediate Idwian/Fronian arrangement.

What evidence supported the original concept?

The Trefawr Track section and graptolite triangulatus zonal boundary were argued to make the division traceable internationally.

How has geology changed the concept?

Aeronian is one of three current Llandovery stages; its Welsh farm-name records a standardisation decision, not an ancient Greek geological quality.

Further historical context

*Naming and context. A new middle Llandovery stage was chosen when an earlier four-stage scheme was judged unsuitable for worldwide correlation; Aeronian* replaced the intermediate Idwian/Fronian arrangement.

*Evidence and later scope. The Trefawr Track section and graptolite triangulatus* zonal boundary were argued to make the division traceable internationally. Aeronian is one of three current Llandovery stages; its Welsh farm-name records a standardisation decision, not an ancient Greek geological quality.

Editorial qualification

The 1970 scheme did *not* already contain “Aeronian”; the 1984 reorganisation is essential context.

Related names

Silurian · Llandovery · Rhuddanian · Telychian · Graptolite

Sources

1. ICS International Chronostratigraphic Chart (June 2026) — Current formal unit, order, rank and numerical age
2. Holland (1984), Steps to a Standard Silurian — Contemporaneous committee history and Aeronian name
3. Cocks, Toghill & Ziegler (1970), Stage Names within the Llandovery Series — Original four-stage proposal, later modified
4. ICS international GSSPs: Silurian stages and boundary issues — Modern formal references, rank, locations and correlation
5. Geological Survey educational compilation of Silurian stage name origins — Locality/name origin, not original creation priority