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.^[5]

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 2021.^[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 Monograptus austerus sequens
Lower boundary GSSP	Trefawr Track Section, Llandovery, Wales, UK 52°01′48″N 3°42′00″W / 52.0300°N 3.7000°W / 52.0300; -3.7000
Lower GSSP ratified	1984^[4]
Upper boundary definition	Just above LAD of the brachiopod Eocoelia intermedia, below FAD of lowest succeeding species Eocoelia curtisi
Upper boundary GSSP	Cefn-cerig Road Section, Llandovery, Wales, UK 51°58′12″N 3°47′24″W / 51.9700°N 3.7900°W / 51.9700; -3.7900
Upper GSSP ratified	1984^[4]

During the Aeronian the Sedgwickii Event occurred in which graptolite diversity was greatly reduced.^[6] 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).^[6]

GSSP

The GSSP is located in the Trefawr Track section, 500m north of Cwm-coed-Aeron Farm, Wales, UK.^[7] 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.^[8]

References

1. Jeppsson, L.; Calner, M. (2007). "The Silurian Mulde Event and a scenario for secundo—secundo events". Earth and Environmental Science Transactions of the Royal Society of Edinburgh. 93 (02): 135–154. doi:10.1017/S0263593300000377.
2. Munnecke, A.; Samtleben, C.; Bickert, T. (2003). "The Ireviken Event in the lower Silurian of Gotland, Sweden-relation to similar Palaeozoic and Proterozoic events". Palaeogeography, Palaeoclimatology, Palaeoecology. 195 (1): 99–124. doi:10.1016/S0031-0182(03)00304-3.
3. "Chart/Time Scale". www.stratigraphy.org. International Commission on Stratigraphy.
4. Holland, C. (June 1985). "Series and Stages of the Silurian System". Episodes. 8 (2): 101–103. doi:10.18814/epiiugs/1985/v8i2/005. Retrieved 15 December 2020.
5. "GSSP Table - All Periods". International Commission on Stratigraphy. Retrieved 2018-09-15.
6. Lopez, Fernando Enrique; Kaufmann, Cintia (2023). "New insights on the Silurian graptolite biostratigraphy of the La Chilca Formation, Poblete Norte section, Central Precordillera of San Juan, Argentina: faunal replacement and paleoenvironmental implications". Andean Geology. 50 (2). doi:10.5027/andgeov50n2-3617.
7. Gradstein, Felix M.; Ogg, James G.; Smith, Alan G. (2004). A Geologic Time Scale 2004. ISBN 9780521786737.
8. "GSSP for Aeronian Stage". International Commission on Stratigraphy. Retrieved September 15, 2018.