Aeronian

In the geologic timescale, the Aeronian is an age of the Llandovery Epoch of the Silurian Period of the Paleozoic Era of the Phanerozoic Eon that began 440.8 ± 1.2 Ma and ended 438.5 ± 1.1 Ma (million years ago). The Aeronian Age succeeds the Rhuddanian Age and precedes the Telychian Age, all in the same epoch.^[8]

Aeronian
440.8 ± 1.2 – 438.5 ± 1.1 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Chronology
−444 — – −442 — – −440 — – −438 — – −436 — – −434 — – −432 — – −430 — – −428 — – −426 — – −424 — – −422 — – −420 — – −418 — Paleozoic O Silurian D L Llandovery Wenlock Ludlow Přídolí E Hirnantian Rhuddanian Aeronian Telychian Sheinwoodian Homerian Gorstian Ludfordian Lochkovian             ← Lau event ← Mulde event[1] ← Ireviken event[2] Subdivision of the Silurian according to the ICS, as of 2023.[3] Vertical axis scale: Millions of years ago
Etymology
Name formality	Formal
Usage information
Celestial body	Earth
Regional usage	Global (ICS)
Time scale(s) used	ICS Time Scale
Definition
Chronological unit	Age
Stratigraphic unit	Stage
Time span formality	Formal
Lower boundary definition	FAD of the graptolite Demirastrites triangulatus
Lower boundary GSSP	Hlásná Třebaň section, Czech Republic 49.9230°N 14.2119°E / 49.9230; 14.2119[4]
Lower GSSP ratified	2024[5][6]
Upper boundary definition	FAD of the graptolite Spirograptus guerichi
Upper boundary GSSP	El Pintado section, Seville, Spain 37.9853°N 5.9285°W / 37.9853; -5.9285[4]
Upper GSSP ratified	2024[5][7]

During the Aeronian the Sedgwickii Event occurred in which graptolite diversity was greatly reduced.^[9] This event has been attested in locations such as today's Canada, Libya as well as in La Chilca Formation in Argentina (then part of Gondwana).^[9]

GSSP

The GSSP is located in the Trefawr Track section, 500m north of Cwm-coed-Aeron Farm, Wales, UK.^[10] The GSSP lies within the gently-dipping blocky mudstones of the Trefawr Formation, which principally yield abundant and diverse shelly faunas, but also contain enough graptolites to allow recognition of several biozones.^[11]