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.[4]
| Aeronian | |
|---|---|
| 440.8 ± 1.2 – 438.5 ± 1.1 Ma | |
| Chronology | |
Epochs in the Silurian -444 — – -442 — – -440 — – -438 — – -436 — – -434 — – -432 — – -430 — – -428 — – -426 — – -424 — – -422 — – -420 — – -418 — Epochs of the Silurian Period. 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 52.0300°N 3.7000°W |
| GSSP ratified | 1984[3] |
| 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 51.9700°N 3.7900°W |
| GSSP ratified | 1984[3] |
GSSP
The GSSP is located in the Trefawr Track section, 500m north of Cwm-coed-Aeron Farm, Wales, UK.[5] 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.[6]
Palaeontology
Agnathans
| Agnathans of the Aeronian | ||||
|---|---|---|---|---|
| Taxa | Presence | Location | Description | Images |
| Rhuddanian-Telychian | It had an elongated body and a dorsal fin and an anal fin near the back third of its body. |  Jamoytius kerwoodi | ||
Cephalopods
| Cephalopods of the Aeronian | ||||
|---|---|---|---|---|
| Taxa | Presence | Location | Description | Images |
| Dapingian-Homerian | The shallow seas of Laurentia, Baltica and Siberia.[7] | Head was soft muscular tissue at the opening of hard cone-like shell. |  Cameroceras, shown feeding on an Aphetoceras, while a quartet of Cyclostomiceras swim by. | |
References
- 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.
- 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.
- Holland, C. (June 1985). "Series and Stages of the Silurian System". 8 (2): 101–103. doi:10.18814/epiiugs/1985/v8i2/005. Retrieved 15 December 2020. Cite journal requires
|journal=(help) - "GSSP Table - All Periods". International Commission on Stratigraphy. Retrieved 2018-09-15.
- Gradstein, Felix M.; Ogg, James G.; Smith, Alan G. (2004). A Geologic Time Scale 2004. ISBN 9780521786737.
- "GSSP for Aeronian Stage". International Commission on Stratigraphy. Retrieved September 15, 2018.
- Frey, R.C. 1995. "Middle and Upper Ordovician nautiloid cephalopods of the Cincinnati Arch region of Kentucky, Indiana, and Ohio" (PDF). U.S. Geological Survey, p.73
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